Lung-Protective Ventilation With Low Tidal Volumes and the Occurrence of Pulmonary Complications in Patients Without Acute Respiratory Distress Syndrome: A Systematic Review and Individual Patient Data Analysis.

PubMed

Neto, Ary Serpa; Simonis, Fabienne D; Barbas, Carmen S V; Biehl, Michelle; Determann, Rogier M; Elmer, Jonathan; Friedman, Gilberto; Gajic, Ognjen; Goldstein, Joshua N; Linko, Rita; Pinheiro de Oliveira, Roselaine; Sundar, Sugantha; Talmor, Daniel; Wolthuis, Esther K; Gama de Abreu, Marcelo; Pelosi, Paolo; Schultz, Marcus J

2015-10-01

Protective mechanical ventilation with low tidal volumes is standard of care for patients with acute respiratory distress syndrome. The aim of this individual patient data analysis was to determine the association between tidal volume and the occurrence of pulmonary complications in ICU patients without acute respiratory distress syndrome and the association between occurrence of pulmonary complications and outcome in these patients. Individual patient data analysis. ICU patients not fulfilling the consensus criteria for acute respiratory distress syndrome at the onset of ventilation. Mechanical ventilation with low tidal volume. The primary endpoint was development of a composite of acute respiratory distress syndrome and pneumonia during hospital stay. Based on the tertiles of tidal volume size in the first 2 days of ventilation, patients were assigned to a "low tidal volume group" (tidal volumes ≤ 7 mL/kg predicted body weight), an "intermediate tidal volume group" (> 7 and < 10 mL/kg predicted body weight), and a "high tidal volume group" (≥ 10 mL/kg predicted body weight). Seven investigations (2,184 patients) were included. Acute respiratory distress syndrome or pneumonia occurred in 23% of patients in the low tidal volume group, in 28% of patients in the intermediate tidal volume group, and in 31% of the patients in the high tidal volume group (adjusted odds ratio [low vs high tidal volume group], 0.72; 95% CI, 0.52-0.98; p = 0.042). Occurrence of pulmonary complications was associated with a lower number of ICU-free and hospital-free days and alive at day 28 (10.0 ± 10.9 vs 13.8 ± 11.6 d; p < 0.01 and 6.1 ± 8.1 vs 8.9 ± 9.4 d; p < 0.01) and an increased hospital mortality (49.5% vs 35.6%; p < 0.01). Ventilation with low tidal volumes is associated with a lower risk of development of pulmonary complications in patients without acute respiratory distress syndrome.

Electrical impedance tomography

PubMed Central

Lobo, Beatriz; Hermosa, Cecilia; Abella, Ana

2018-01-01

Continuous assessment of respiratory status is one of the cornerstones of modern intensive care unit (ICU) monitoring systems. Electrical impedance tomography (EIT), although with some constraints, may play the lead as a new diagnostic and guiding tool for an adequate optimization of mechanical ventilation in critically ill patients. EIT may assist in defining mechanical ventilation settings, assess distribution of tidal volume and of end-expiratory lung volume (EELV) and contribute to titrate positive end-expiratory pressure (PEEP)/tidal volume combinations. It may also quantify gains (recruitment) and losses (overdistention or derecruitment), granting a more realistic evaluation of different ventilator modes or recruitment maneuvers, and helping in the identification of responders and non-responders to such maneuvers. Moreover, EIT also contributes to the management of life-threatening lung diseases such as pneumothorax, and aids in guiding fluid management in the critical care setting. Lastly, assessment of cardiac function and lung perfusion through electrical impedance is on the way. PMID:29430443

Nasal mask ventilation is better than face mask ventilation in edentulous patients

PubMed Central

Kapoor, Mukul Chandra; Rana, Sandeep; Singh, Arvind Kumar; Vishal, Vindhya; Sikdar, Indranil

2016-01-01

Background and Aims: Face mask ventilation of the edentulous patient is often difficult as ineffective seating of the standard mask to the face prevents attainment of an adequate air seal. The efficacy of nasal ventilation in edentulous patients has been cited in case reports but has never been investigated. Material and Methods: Consecutive edentulous adult patients scheduled for surgery under general anesthesia with endotracheal intubation, during a 17-month period, were prospectively evaluated. After induction of anesthesia and administration of neuromuscular blocker, lungs were ventilated with a standard anatomical face mask of appropriate size, using a volume controlled anesthesia ventilator with tidal volume set at 10 ml/kg. In case of inadequate ventilation, the mask position was adjusted to achieve best-fit. Inspired and expired tidal volumes were measured. Thereafter, the face mask was replaced by a nasal mask and after achieving best-fit, the inspired and expired tidal volumes were recorded. The difference in expired tidal volumes and airway pressures at best-fit with the use of the two masks and number of patients with inadequate ventilation with use of the masks were statistically analyzed. Results: A total of 79 edentulous patients were recruited for the study. The difference in expiratory tidal volumes with the use of the two masks at best-fit was statistically significant (P = 0.0017). Despite the best-fit mask placement, adequacy of ventilation could not be achieved in 24.1% patients during face mask ventilation, and 12.7% patients during nasal mask ventilation and the difference was statistically significant. Conclusion: Nasal mask ventilation is more efficient than standard face mask ventilation in edentulous patients. PMID:27625477

Practice of mechanical ventilation in cardiac arrest patients and effects of targeted temperature management: A substudy of the targeted temperature management trial.

PubMed

Harmon, Matthew B A; van Meenen, David M P; van der Veen, Annelou L I P; Binnekade, Jan M; Dankiewicz, Josef; Ebner, Florian; Nielsen, Niklas; Pelosi, Paolo; Schultz, Marcus J; Horn, Janneke; Friberg, Hans; Juffermans, Nicole P

2018-05-12

Mechanical ventilation practices in patients with cardiac arrest are not well described. Also, the effect of temperature on mechanical ventilation settings is not known. The aims of this study were 1) to describe practice of mechanical ventilation and its relation with outcome 2) to determine effects of different target temperatures strategies (33 °C versus 36 °C) on mechanical ventilation settings. This is a substudy of the TTM-trial in which unconscious survivors of a cardiac arrest due to a cardiac cause were randomized to two TTM strategies, 33 °C (TTM33) and 36 °C (TTM36). Mechanical ventilation data were obtained at three time points: 1) before TTM; 2) at the end of TTM (before rewarming) and 3) after rewarming. Logistic regression was used to determine an association between mechanical ventilation variables and outcome. Repeated-measures mixed modelling was performed to determine the effect of TTM on ventilation settings. Mechanical ventilation data was available for 567 of the 950 TTM patients. Of these, 81% was male with a mean (SD) age of 64 (12) years. At the end of TTM median tidal volume was 7.7 ml/kg predicted body weight (PBW)(6.4-8.7) and 60% of patients were ventilated with a tidal volume ≤ 8 ml/kg PBW. Median PEEP was 7.7cmH 2 O (6.4-8.7) and mean driving pressure was 14.6 cmH 2 O (±4.3). The median FiO 2 fraction was 0.35 (0.30-0.45). Multivariate analysis showed an independent relationship between increased respiratory rate and 28-day mortality. TTM33 resulted in lower end-tidal CO 2 (Pgroup = 0.0003) and higher alveolar dead space fraction (Pgroup = 0.003) compared to TTM36, while PCO 2 levels and respiratory minute volume were similar between groups. In the majority of the cardiac arrest patients, protective ventilation settings are applied, including low tidal volumes and driving pressures. High respiratory rate was associated with mortality. TTM33 results in lower end-tidal CO 2 levels and a higher alveolar dead space fraction compared to TTTM36. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

The Origin of Faint Tidal Features around Galaxies in the RESOLVE Survey

NASA Astrophysics Data System (ADS)

Hood, Callie E.; Kannappan, Sheila J.; Stark, David V.; Dell’Antonio, Ian P.; Moffett, Amanda J.; Eckert, Kathleen D.; Norris, Mark A.; Hendel, David

2018-04-01

We study tidal features around galaxies in the REsolved Spectroscopy Of a Local VolumE (RESOLVE) survey. Our sample consists of 1048 RESOLVE galaxies that overlap with the DECam Legacy Survey, which reaches an r-band 3σ depth of ∼27.9 mag arcsec‑2 for a 100 arcsec2 feature. Images were masked, smoothed, and inspected for tidal features such as streams, shells, or tails/arms. We find tidal features in 17±2% of our galaxies, setting a lower limit on the true frequency. The frequency of tidal features in the gas-poor (gas-to-stellar mass ratio <0.1) subsample is lower than in the gas-rich subsample (13±3% versus 19±2%). Within the gas-poor subsample, galaxies with tidal features have higher stellar and halo masses, ∼3× closer distances to nearest neighbors (in the same group), and possibly fewer group members at fixed halo mass than galaxies without tidal features, but similar specific star formation rates. These results suggest tidal features in gas-poor galaxies are typically streams/shells from dry mergers or satellite disruption. In contrast, the presence of tidal features around gas-rich galaxies does not correlate with stellar or halo mass, suggesting these tidal features are often tails/arms from resonant interactions. Similar to tidal features in gas-poor galaxies, tidal features in gas-rich galaxies imply 1.7× closer nearest neighbors in the same group; however, they are associated with diskier morphologies, higher star formation rates, and higher gas content. In addition to interactions with known neighbors, we suggest that tidal features in gas-rich galaxies may arise from accretion of cosmic gas and/or gas-rich satellites below the survey limit.

Mask Ventilation during Induction of General Anesthesia: Influences of Obstructive Sleep Apnea.

PubMed

Sato, Shin; Hasegawa, Makoto; Okuyama, Megumi; Okazaki, Junko; Kitamura, Yuji; Sato, Yumi; Ishikawa, Teruhiko; Sato, Yasunori; Isono, Shiroh

2017-01-01

Depending on upper airway patency during anesthesia induction, tidal volume achieved by mask ventilation may vary. In 80 adult patients undergoing general anesthesia, the authors tested a hypothesis that tidal volume during mask ventilation is smaller in patients with sleep-disordered breathing priorly defined as apnea hypopnea index greater than 5 per hour. One-hand mask ventilation with a constant ventilator setting (pressure-controlled ventilation) was started 20 s after injection of rocuronium and maintained for 1 min during anesthesia induction. Mask ventilation efficiency was assessed by the breath number needed to initially exceed 5 ml/kg ideal body weight of expiratory tidal volume (primary outcome) and tidal volumes (secondary outcomes) during initial 15 breaths (UMIN000012494). Tidal volume progressively increased by more than 70% in 1 min and did not differ between sleep-disordered breathing (n = 42) and non-sleep-disordered breathing (n = 38) patients. In post hoc subgroup analyses, the primary outcome breath number (mean [95% CI], 5.7 [4.1 to 7.3] vs. 1.7 [0.2 to 3.2] breath; P = 0.001) and mean tidal volume (6.5 [4.6 to 8.3] vs. 9.6 [7.7 to 11.4] ml/kg ideal body weight; P = 0.032) were significantly smaller in 20 sleep-disordered breathing patients with higher apnea hypopnea index (median [25th to 75th percentile]: 21.7 [17.6 to 31] per hour) than in 20 non-sleep disordered breathing subjects with lower apnea hypopnea index (1.0 [0.3 to 1.5] per hour). Obesity and occurrence of expiratory flow limitation during one-hand mask ventilation independently explained the reduction of efficiency of mask ventilation, while the use of two hands effectively normalized inefficient mask ventilation during one-hand mask ventilation. One-hand mask ventilation is difficult in patients with obesity and severe sleep-disordered breathing particularly when expiratory flow limitation occurs during mask ventilation.

Ventilation practices in subarachnoid hemorrhage: a cohort study exploring the use of lung protective ventilation.

PubMed

Marhong, Jonathan D; Ferguson, Niall D; Singh, Jeffrey M

2014-10-01

Acute respiratory distress syndrome (ARDS) is common following aneurysmal subarachnoid hemorrhage (SAH), but the influence of mechanical ventilator settings on its development is unclear. We sought to determine adherence to lung protective thresholds in ventilated patients with SAH and describe the association between ventilator settings and subsequent development of ARDS. We conducted a retrospective cohort study of consecutive patients receiving mechanical ventilation within 72 h of SAH at a single academic center. Ventilator settings and blood gas data were collected twice daily for the first 7 days of ventilation along with ICU and hospital outcomes. Lung protective ventilation was defined as follows: tidal volume ≤8 mL/kg of predicted body weight, positive end-expiratory pressure (PEEP) ≥5 cm H(2)O, and peak or plateau pressure ≤30 cm H(2)O. The development of ARDS was ascertained retrospectively by PaO(2)/FiO(2) ≤300 with new bilateral lung opacities on chest X-ray within one day of hypoxemia. We identified 62 patients who underwent early mechanical ventilation following SAH. PS and Continuous Positive Airway Pressure were common ventilator modes with a median tidal volume of 7.8 mL/kg [interquartile range 6.8-8.8], median peak pressure of 14 cm H(2)O [IQR 12-17], and median PEEP of 5 cm H(2)O [IQR 5-6]. Adherence to tidal volumes ≤8 mL/kg was seen in 64 % of all observations and peak pressures <30 cm H(2)O were 94 % of all observations. All three lung protective criteria were seen in 58 % of all observations. Thirty-one patients (50 %) were determined to have ARDS. ARDS patients were more frequently ventilated with a peak pressure >30 cm H(2)O (11.3 % of ARDS ventilation days vs. 0 % of non-ARDS ventilation days; p < 0.01). Initial tidal volume was not associated with subsequent development of ARDS in univariate (p = 0.6) or multivariate analysis (p = 0.49). Only the number of ARDS risk factors was independently associated with the development of ARDS (Adjusted Odds Ratio 2.8 per additional risk factor [95 % CI 1.2-6.5]). Patients with SAH requiring mechanical ventilation frequently breathe spontaneously, generating tidal volumes above usual protective thresholds regardless of meeting ARDS criteria. In patients with SAH, the presence of an additional ARDS risk factor should prompt close screening for the development of ARDS and consideration of adjustment of ventilator settings to meet lung protective thresholds.

Function of the Dräger Oxylog ventilator at high altitude.

PubMed

Thomas, G; Brimacombe, J

1994-06-01

We have assessed the performance of the Dräger Oxylog ventilator at high altitude using a decompression chamber and a lung simulator set to mimic the normal and non-compliant lung. In the normal lung, tidal volume increased by 28% at 2040 metres and by 106% at 9120 metres. A lesser change, but in the opposite direction, occurred in respiratory rate. The net effect was a linear increase in minute volume with altitude. At 2040 and 9144 metres minute volume increased by 13% and by 45%, and rate decreased by 10% and 30% respectively. In the abnormal lung stimulation, similar, but slightly less marked, changes occurred in all variables. These changes are of sufficient magnitude to require frequent observation of tidal volume and respiratory rate during aircraft ascent and descent.

Accuracy of tidal volume delivered by home mechanical ventilation during mouthpiece ventilation

PubMed Central

Prigent, Helene; Falaize, Line; Leroux, Karl; Santos, Dante; Vaugier, Isabelle; Orlikowski, David; Lofaso, Frederic

2016-01-01

The aim of our study was to evaluate efficacy and reliability of currently available ventilators for mouthpiece ventilation (MPV). Five life-support home ventilators were assessed in a bench test using different settings simulating the specificities of MPV, such as intermittent circuit disconnection and presence of continuous leaks. The intermittent disconnection of the circuit caused relevant swings in the delivered tidal volume (VT), showing a VT overshoot during the disconnection periods and a VT decrease when the interface was reconnected to the test lung. The five ventilators showed substantial differences in the number of respiratory cycles necessary to reach a stable VT in the volume-controlled setting, ranging from 1.3 ± 0.6 to 7.3 ± 1.2 cycles. These differences were less accentuated in the volume-assisted setting (MPV-dedicated mode, when available). Our data show large differences in the capacity of the different ventilators to deal with the rapidly changing respiratory load features that characterize MPV, which can be further accentuated according to the used ventilator setting. The dedicated MPV modes allow improvement in the performance of ventilators only in some defined situations. This has practical consequences for the choice of the ventilator to be used for MPV in a specific patient. PMID:27146811

The effects of low tidal ventilation on lung strain correlate with respiratory system compliance.

PubMed

Xie, Jianfeng; Jin, Fang; Pan, Chun; Liu, Songqiao; Liu, Ling; Xu, Jingyuan; Yang, Yi; Qiu, Haibo

2017-02-03

The effect of alterations in tidal volume on mortality of acute respiratory distress syndrome (ARDS) is determined by respiratory system compliance. We aimed to investigate the effects of different tidal volumes on lung strain in ARDS patients who had various levels of respiratory system compliance. Nineteen patients were divided into high (C high group) and low (C low group) respiratory system compliance groups based on their respiratory system compliance values. We defined compliance ≥0.6 ml/(cmH 2 O/kg) as C high and compliance <0.6 ml/(cmH 2 O/kg) as C low . End-expiratory lung volumes (EELV) at various tidal volumes were measured by nitrogen wash-in/washout. Lung strain was calculated as the ratio between tidal volume and EELV. The primary outcome was that lung strain is a function of tidal volume in patients with various levels of respiratory system compliance. The mean baseline EELV, strain and respiratory system compliance values were 1873 ml, 0.31 and 0.65 ml/(cmH 2 O/kg), respectively; differences in all of these parameters were statistically significant between the two groups. For all participants, a positive correlation was found between the respiratory system compliance and EELV (R = 0.488, p = 0.034). Driving pressure and strain increased together as the tidal volume increased from 6 ml/kg predicted body weight (PBW) to 12 ml/kg PBW. Compared to the C high ARDS patients, the driving pressure was significantly higher in the C low patients at each tidal volume. Similar effects of lung strain were found for tidal volumes of 6 and 8 ml/kg PBW. The "lung injury" limits for driving pressure and lung strain were much easier to exceed with increases in the tidal volume in C low patients. Respiratory system compliance affected the relationships between tidal volume and driving pressure and lung strain in ARDS patients. These results showed that increasing tidal volume induced lung injury more easily in patients with low respiratory system compliance. Clinicaltrials.gov identifier NCT01864668 , Registered 21 May 2013.

Evaluating humidity recovery efficiency of currently available heat and moisture exchangers: a respiratory system model study.

PubMed

Lucato, Jeanette Janaina Jaber; Adams, Alexander Bernard; Souza, Rogério; Torquato, Jamili Anbar; Carvalho, Carlos Roberto Ribeiro; Marini, John J

2009-01-01

To evaluate and compare the efficiency of humidification in available heat and moisture exchanger models under conditions of varying tidal volume, respiratory rate, and flow rate. Inspired gases are routinely preconditioned by heat and moisture exchangers to provide a heat and water content similar to that provided normally by the nose and upper airways. The absolute humidity of air retrieved from and returned to the ventilated patient is an important measurable outcome of the heat and moisture exchangers' humidifying performance. Eight different heat and moisture exchangers were studied using a respiratory system analog. The system included a heated chamber (acrylic glass, maintained at 37 degrees C), a preserved swine lung, a hygrometer, circuitry and a ventilator. Humidity and temperature levels were measured using eight distinct interposed heat and moisture exchangers given different tidal volumes, respiratory frequencies and flow-rate conditions. Recovery of absolute humidity (%RAH) was calculated for each setting. Increasing tidal volumes led to a reduction in %RAH for all heat and moisture exchangers while no significant effect was demonstrated in the context of varying respiratory rate or inspiratory flow. Our data indicate that heat and moisture exchangers are more efficient when used with low tidal volume ventilation. The roles of flow and respiratory rate were of lesser importance, suggesting that their adjustment has a less significant effect on the performance of heat and moisture exchangers.

DOE Office of Scientific and Technical Information (OSTI.GOV)

White, Benjamin M., E-mail: bmwhite@mednet.ucla.edu; Lamb, James M.; Low, Daniel A.

Purpose: To characterize radiation therapy patient breathing patterns based on measured external surrogate information. Methods: Breathing surrogate data were collected during 4DCT from a cohort of 50 patients including 28 patients with lung cancer and 22 patients without lung cancer. A spirometer and an abdominal pneumatic bellows were used as the surrogates. The relationship between these measurements was assumed to be linear within a small phase difference. The signals were correlated and drift corrected using a previously published method to convert the signal into tidal volume. The airflow was calculated with a first order time derivative of the tidal volumemore » using a window centered on the point of interest and with a window length equal to the CT gantry rotation period. The airflow was compared against the tidal volume to create ellipsoidal patterns that were binned into 25 ml × 25 ml/s bins to determine the relative amount of time spent in each bin. To calculate the variability of the maximum inhalation tidal volume within a free-breathing scan timeframe, a metric based on percentile volume ratios was defined. The free breathing variability metric (κ) was defined as the ratio between extreme inhalation tidal volumes (defined as >93 tidal volume percentile of the measured tidal volume) and normal inhalation tidal volume (defined as >80 tidal volume percentile of the measured tidal volume). Results: There were three observed types of volume-flow curves, labeled Types 1, 2, and 3. Type 1 patients spent a greater duration of time during exhalation withκ = 1.37 ± 0.11. Type 2 patients had equal time duration spent during inhalation and exhalation with κ = 1.28 ± 0.09. The differences between the mean peak exhalation to peak inhalation tidal volume, breathing period, and the 85th tidal volume percentile for Type 1 and Type 2 patients were statistically significant at the 2% significance level. The difference between κ and the 98th tidal volume percentile for Type 1 and Type 2 patients was found to be statistically significant at the 1% significance level. Three patients did not display a breathing stability curve that could be classified as Type 1 or Type 2 due to chaotic breathing patterns. These patients were classified as Type 3 patients. Conclusions: Based on an observed volume-flow curve pattern, the cohort of 50 patients was divided into three categories called Type 1, Type 2, and Type 3. There were statistically significant differences in breathing characteristics between Type 1 and Type 2 patients. The use of volume-flow curves to classify patients has been demonstrated as a physiological characterization metric that has the potential to optimize gating windows in radiation therapy.« less

Poor Adherence to Lung-Protective Mechanical Ventilation in Pediatric Acute Respiratory Distress Syndrome.

PubMed

Ward, Shan L; Quinn, Carson M; Valentine, Stacey L; Sapru, Anil; Curley, Martha A Q; Willson, Douglas F; Liu, Kathleen D; Matthay, Michael A; Flori, Heidi R

2016-10-01

To determine the frequency of low-tidal volume ventilation in pediatric acute respiratory distress syndrome and assess if any demographic or clinical factors improve low-tidal volume ventilation adherence. Descriptive post hoc analysis of four multicenter pediatric acute respiratory distress syndrome studies. Twenty-six academic PICU. Three hundred fifteen pediatric acute respiratory distress syndrome patients. All patients who received conventional mechanical ventilation at hours 0 and 24 of pediatric acute respiratory distress syndrome who had data to calculate ideal body weight were included. Two cutoff points for low-tidal volume ventilation were assessed: less than or equal to 6.5 mL/kg of ideal body weight and less than or equal to 8 mL/kg of ideal body weight. Of 555 patients, we excluded 240 for other respiratory support modes or missing data. The remaining 315 patients had a median PaO2-to-FIO2 ratio of 140 (interquartile range, 90-201), and there were no differences in demographics between those who did and did not receive low-tidal volume ventilation. With tidal volume cutoff of less than or equal to 6.5 mL/kg of ideal body weight, the adherence rate was 32% at hour 0 and 33% at hour 24. A low-tidal volume ventilation cutoff of tidal volume less than or equal to 8 mL/kg of ideal body weight resulted in an adherence rate of 58% at hour 0 and 60% at hour 24. Low-tidal volume ventilation use was no different by severity of pediatric acute respiratory distress syndrome nor did adherence improve over time. At hour 0, overweight children were less likely to receive low-tidal volume ventilation less than or equal to 6.5 mL/kg ideal body weight (11% overweight vs 38% nonoverweight; p = 0.02); no difference was noted by hour 24. Furthermore, in the overweight group, using admission weight instead of ideal body weight resulted in misclassification of up to 14% of patients as receiving low-tidal volume ventilation when they actually were not. Low-tidal volume ventilation is underused in the first 24 hours of pediatric acute respiratory distress syndrome. Age, Pediatric Risk of Mortality-III, and pediatric acute respiratory distress syndrome severity were not associated with improved low-tidal volume ventilation adherence nor did adherence improve over time. Overweight children were less likely to receive low-tidal volume ventilation strategies in the first day of illness.

Interaction between peri-operative blood transfusion, tidal volume, airway pressure and postoperative ARDS: an individual patient data meta-analysis

PubMed Central

Juffermans, Nicole P.; Hemmes, Sabrine N. T.; Barbas, Carmen S. V.; Beiderlinden, Martin; Biehl, Michelle; Fernandez-Bustamante, Ana; Futier, Emmanuel; Gajic, Ognjen; Jaber, Samir; Kozian, Alf; Licker, Marc; Lin, Wen-Qian; Memtsoudis, Stavros G.; Miranda, Dinis Reis; Moine, Pierre; Paparella, Domenico; Ranieri, Marco; Scavonetto, Federica; Schilling, Thomas; Selmo, Gabriele; Severgnini, Paolo; Sprung, Juraj; Sundar, Sugantha; Talmor, Daniel; Treschan, Tanja; Unzueta, Carmen; Weingarten, Toby N.; Wolthuis, Esther K.; Wrigge, Hermann; de Abreu, Marcelo Gama; Pelosi, Paolo; Schultz, Marcus J.

2018-01-01

Background Transfusion of blood products and mechanical ventilation with injurious settings are considered risk factors for postoperative lung injury in surgical Patients. Methods A systematic review and individual patient data meta-analysis was done to determine the independent effects of peri-operative transfusion of blood products, intra-operative tidal volume and airway pressure in adult patients undergoing mechanical ventilation for general surgery, as well as their interactions on the occurrence of postoperative acute respiratory distress syndrome (ARDS). Observational studies and randomized trials were identified by a systematic search of MEDLINE, CINAHL, Web of Science, and CENTRAL and screened for inclusion into a meta-analysis. Individual patient data were obtained from the corresponding authors. Patients were stratified according to whether they received transfusion in the peri-operative period [red blood cell concentrates (RBC) and/or fresh frozen plasma (FFP)], tidal volume size [≤7 mL/kg predicted body weight (PBW), 7–10 and >10 mL/kg PBW] and airway pressure level used during surgery (≤15, 15–20 and >20 cmH2O). The primary outcome was development of postoperative ARDS. Results Seventeen investigations were included (3,659 patients). Postoperative ARDS occurred in 40 (7.2%) patients who received at least one blood product compared to 40 patients (2.5%) who did not [adjusted hazard ratio (HR), 2.32; 95% confidence interval (CI), 1.25–4.33; P=0.008]. Incidence of postoperative ARDS was highest in patients ventilated with tidal volumes of >10 mL/kg PBW and having airway pressures of >20 cmH2O receiving both RBC and FFP, and lowest in patients ventilated with tidal volume of ≤7 mL/kg PBW and having airway pressures of ≤15 cmH2O with no transfusion. There was a significant interaction between transfusion and airway pressure level (P=0.002) on the risk of postoperative ARDS. Conclusions Peri-operative transfusion of blood products is associated with an increased risk of postoperative ARDS, which seems more dependent on airway pressure than tidal volume size. PMID:29430440

Interaction between peri-operative blood transfusion, tidal volume, airway pressure and postoperative ARDS: an individual patient data meta-analysis.

PubMed

Serpa Neto, Ary; Juffermans, Nicole P; Hemmes, Sabrine N T; Barbas, Carmen S V; Beiderlinden, Martin; Biehl, Michelle; Fernandez-Bustamante, Ana; Futier, Emmanuel; Gajic, Ognjen; Jaber, Samir; Kozian, Alf; Licker, Marc; Lin, Wen-Qian; Memtsoudis, Stavros G; Miranda, Dinis Reis; Moine, Pierre; Paparella, Domenico; Ranieri, Marco; Scavonetto, Federica; Schilling, Thomas; Selmo, Gabriele; Severgnini, Paolo; Sprung, Juraj; Sundar, Sugantha; Talmor, Daniel; Treschan, Tanja; Unzueta, Carmen; Weingarten, Toby N; Wolthuis, Esther K; Wrigge, Hermann; de Abreu, Marcelo Gama; Pelosi, Paolo; Schultz, Marcus J

2018-01-01

Transfusion of blood products and mechanical ventilation with injurious settings are considered risk factors for postoperative lung injury in surgical Patients. A systematic review and individual patient data meta-analysis was done to determine the independent effects of peri-operative transfusion of blood products, intra-operative tidal volume and airway pressure in adult patients undergoing mechanical ventilation for general surgery, as well as their interactions on the occurrence of postoperative acute respiratory distress syndrome (ARDS). Observational studies and randomized trials were identified by a systematic search of MEDLINE, CINAHL, Web of Science, and CENTRAL and screened for inclusion into a meta-analysis. Individual patient data were obtained from the corresponding authors. Patients were stratified according to whether they received transfusion in the peri-operative period [red blood cell concentrates (RBC) and/or fresh frozen plasma (FFP)], tidal volume size [≤7 mL/kg predicted body weight (PBW), 7-10 and >10 mL/kg PBW] and airway pressure level used during surgery (≤15, 15-20 and >20 cmH 2 O). The primary outcome was development of postoperative ARDS. Seventeen investigations were included (3,659 patients). Postoperative ARDS occurred in 40 (7.2%) patients who received at least one blood product compared to 40 patients (2.5%) who did not [adjusted hazard ratio (HR), 2.32; 95% confidence interval (CI), 1.25-4.33; P=0.008]. Incidence of postoperative ARDS was highest in patients ventilated with tidal volumes of >10 mL/kg PBW and having airway pressures of >20 cmH 2 O receiving both RBC and FFP, and lowest in patients ventilated with tidal volume of ≤7 mL/kg PBW and having airway pressures of ≤15 cmH 2 O with no transfusion. There was a significant interaction between transfusion and airway pressure level (P=0.002) on the risk of postoperative ARDS. Peri-operative transfusion of blood products is associated with an increased risk of postoperative ARDS, which seems more dependent on airway pressure than tidal volume size.

Dead space and tidal volume of the giraffe compared with some other mammals.

PubMed

Hugh-Jones, P; Barter, C E; Hime, J M; Rusbridge, M M

1978-10-01

The ventilation, tidal volume and anatomical dead-space were measured in a living giraffe and compared with similar measurements in a camel, red deer, llama and man. The giraffe had a resting tidal volume of about 3.3 litres with a dead-space/tidal-volume ratio of 0.34. The giraffe breathes slowly, apparently because of the unusually small diameter of its trachea relative to its length, compared with known measurement in other mammals.

High tidal volume decreases adult respiratory distress syndrome, atelectasis, and ventilator days compared with low tidal volume in pediatric burned patients with inhalation injury.

PubMed

Sousse, Linda E; Herndon, David N; Andersen, Clark R; Ali, Arham; Benjamin, Nicole C; Granchi, Thomas; Suman, Oscar E; Mlcak, Ronald P

2015-04-01

Inhalation injury, which is among the causes of acute lung injury and acute respiratory distress syndrome (ARDS), continues to represent a significant source of mortality in burned patients. Inhalation injury often requires mechanical ventilation, but the ideal tidal volume strategy is not clearly defined in burned pediatric patients. The aim of this study was to determine the effects of low and high tidal volume on the number of ventilator days, ventilation pressures, and incidence of atelectasis, pneumonia, and ARDS in pediatric burned patients with inhalation injury within 1 year post burn injury. From 1986 to 2014, inhalation injury was diagnosed by bronchoscopy in pediatric burned patients (n = 932). Patients were divided into 3 groups: unventilated (n = 241), high tidal volume (HTV, 15 ± 3 mL/kg, n = 190), and low tidal volume (LTV, 9 ± 3 mL/kg, n = 501). High tidal volume was associated with significantly decreased ventilator days (p < 0.005) and maximum positive end expiratory pressure (p < 0.0001) and significantly increased maximum peak inspiratory pressure (p < 0.02) and plateau pressure (p < 0.02) compared with those in patients with LTV. The incidence of atelectasis (p < 0.0001) and ARDS (p < 0.02) was significantly decreased with HTV compared with LTV. However, the incidence of pneumothorax was significantly increased in the HTV group compared with the LTV group (p < 0.03). High tidal volume significantly decreases ventilator days and the incidence of both atelectasis and ARDS compared with low tidal volume in pediatric burned patients with inhalation injury. Therefore, the use of HTV may interrupt sequences leading to lung injury in our patient population. Copyright © 2015 American College of Surgeons. Published by Elsevier Inc. All rights reserved.

Evaluating Humidity Recovery Efficiency of Currently Available Heat and Moisture Exchangers: A Respiratory System Model Study

PubMed Central

Lucato, Jeanette Janaina Jaber; Adams, Alexander Bernard; Souza, Rogério; Torquato, Jamili Anbar; Carvalho, Carlos Roberto Ribeiro; Marini, John J

2009-01-01

OBJECTIVES: To evaluate and compare the efficiency of humidification in available heat and moisture exchanger models under conditions of varying tidal volume, respiratory rate, and flow rate. INTRODUCTION: Inspired gases are routinely preconditioned by heat and moisture exchangers to provide a heat and water content similar to that provided normally by the nose and upper airways. The absolute humidity of air retrieved from and returned to the ventilated patient is an important measurable outcome of the heat and moisture exchangers’ humidifying performance. METHODS: Eight different heat and moisture exchangers were studied using a respiratory system analog. The system included a heated chamber (acrylic glass, maintained at 37°C), a preserved swine lung, a hygrometer, circuitry and a ventilator. Humidity and temperature levels were measured using eight distinct interposed heat and moisture exchangers given different tidal volumes, respiratory frequencies and flow-rate conditions. Recovery of absolute humidity (%RAH) was calculated for each setting. RESULTS: Increasing tidal volumes led to a reduction in %RAH for all heat and moisture exchangers while no significant effect was demonstrated in the context of varying respiratory rate or inspiratory flow. CONCLUSIONS: Our data indicate that heat and moisture exchangers are more efficient when used with low tidal volume ventilation. The roles of flow and respiratory rate were of lesser importance, suggesting that their adjustment has a less significant effect on the performance of heat and moisture exchangers. PMID:19578664

Delivery of tidal volume from four anaesthesia ventilators during volume-controlled ventilation: a bench study.

PubMed

Wallon, G; Bonnet, A; Guérin, C

2013-06-01

Tidal volume (V(T)) must be accurately delivered by anaesthesia ventilators in the volume-controlled ventilation mode in order for lung protective ventilation to be effective. However, the impact of fresh gas flow (FGF) and lung mechanics on delivery of V(T) by the newest anaesthesia ventilators has not been reported. We measured delivered V(T) (V(TI)) from four anaesthesia ventilators (Aisys™, Flow-i™, Primus™, and Zeus™) on a pneumatic test lung set with three combinations of lung compliance (C, ml cm H2O(-1)) and resistance (R, cm H2O litre(-1) s(-2)): C60R5, C30R5, C60R20. For each CR, three FGF rates (0.5, 3, 10 litre min(-1)) were investigated at three set V(T)s (300, 500, 800 ml) and two values of PEEP (0 and 10 cm H2O). The volume error = [(V(TI) - V(Tset))/V(Tset)] ×100 was computed in body temperature and pressure-saturated conditions and compared using analysis of variance. For each CR and each set V(T), the absolute value of the volume error significantly declined from Aisys™ to Flow-i™, Zeus™, and Primus™. For C60R5, these values were 12.5% for Aisys™, 5% for Flow-i™ and Zeus™, and 0% for Primus™. With an increase in FGF, absolute values of the volume error increased only for Aisys™ and Zeus™. However, in C30R5, the volume error was minimal at mid-FGF for Aisys™. The results were similar at PEEP 10 cm H2O. Under experimental conditions, the volume error differed significantly between the four new anaesthesia ventilators tested and was influenced by FGF, although this effect may not be clinically relevant.

Association between use of lung-protective ventilation with lower tidal volumes and clinical outcomes among patients without acute respiratory distress syndrome: a meta-analysis.

PubMed

Serpa Neto, Ary; Cardoso, Sérgio Oliveira; Manetta, José Antônio; Pereira, Victor Galvão Moura; Espósito, Daniel Crepaldi; Pasqualucci, Manoela de Oliveira Prado; Damasceno, Maria Cecília Toledo; Schultz, Marcus J

2012-10-24

Lung-protective mechanical ventilation with the use of lower tidal volumes has been found to improve outcomes of patients with acute respiratory distress syndrome (ARDS). It has been suggested that use of lower tidal volumes also benefits patients who do not have ARDS. To determine whether use of lower tidal volumes is associated with improved outcomes of patients receiving ventilation who do not have ARDS. MEDLINE, CINAHL, Web of Science, and Cochrane Central Register of Controlled Trials up to August 2012. Eligible studies evaluated use of lower vs higher tidal volumes in patients without ARDS at onset of mechanical ventilation and reported lung injury development, overall mortality, pulmonary infection, atelectasis, and biochemical alterations. Three reviewers extracted data on study characteristics, methods, and outcomes. Disagreement was resolved by consensus. Twenty articles (2822 participants) were included. Meta-analysis using a fixed-effects model showed a decrease in lung injury development (risk ratio [RR], 0.33; 95% CI, 0.23 to 0.47; I2, 0%; number needed to treat [NNT], 11), and mortality (RR, 0.64; 95% CI, 0.46 to 0.89; I2, 0%; NNT, 23) in patients receiving ventilation with lower tidal volumes. The results of lung injury development were similar when stratified by the type of study (randomized vs nonrandomized) and were significant only in randomized trials for pulmonary infection and only in nonrandomized trials for mortality. Meta-analysis using a random-effects model showed, in protective ventilation groups, a lower incidence of pulmonary infection (RR, 0.45; 95% CI, 0.22 to 0.92; I2, 32%; NNT, 26), lower mean (SD) hospital length of stay (6.91 [2.36] vs 8.87 [2.93] days, respectively; standardized mean difference [SMD], 0.51; 95% CI, 0.20 to 0.82; I2, 75%), higher mean (SD) PaCO2 levels (41.05 [3.79] vs 37.90 [4.19] mm Hg, respectively; SMD, -0.51; 95% CI, -0.70 to -0.32; I2, 54%), and lower mean (SD) pH values (7.37 [0.03] vs 7.40 [0.04], respectively; SMD, 1.16; 95% CI, 0.31 to 2.02; I2, 96%) but similar mean (SD) ratios of PaO2 to fraction of inspired oxygen (304.40 [65.7] vs 312.97 [68.13], respectively; SMD, 0.11; 95% CI, -0.06 to 0.27; I2, 60%). Tidal volume gradients between the 2 groups did not influence significantly the final results. Among patients without ARDS, protective ventilation with lower tidal volumes was associated with better clinical outcomes. Some of the limitations of the meta-analysis were the mixed setting of mechanical ventilation (intensive care unit or operating room) and the duration of mechanical ventilation.

Effects of different tidal volumes in pulmonary and extrapulmonary lung injury with or without intraabdominal hypertension.

PubMed

Santos, Cíntia L; Moraes, Lillian; Santos, Raquel S; Oliveira, Mariana G; Silva, Johnatas D; Maron-Gutierrez, Tatiana; Ornellas, Débora S; Morales, Marcelo M; Capelozzi, Vera L; Jamel, Nelson; Pelosi, Paolo; Rocco, Patricia R M; Garcia, Cristiane S N B

2012-03-01

We hypothesized that: (1) intraabdominal hypertension increases pulmonary inflammatory and fibrogenic responses in acute lung injury (ALI); (2) in the presence of intraabdominal hypertension, higher tidal volume reduces lung damage in extrapulmonary ALI, but not in pulmonary ALI. Wistar rats were randomly allocated to receive Escherichia coli lipopolysaccharide intratracheally (pulmonary ALI) or intraperitoneally (extrapulmonary ALI). After 24 h, animals were randomized into subgroups without or with intraabdominal hypertension (15 mmHg) and ventilated with positive end expiratory pressure = 5 cmH(2)O and tidal volume of 6 or 10 ml/kg during 1 h. Lung and chest wall mechanics, arterial blood gases, lung and distal organ histology, and interleukin (IL)-1β, IL-6, caspase-3 and type III procollagen (PCIII) mRNA expressions in lung tissue were analyzed. With intraabdominal hypertension, (1) chest-wall static elastance increased, and PCIII, IL-1β, IL-6, and caspase-3 expressions were more pronounced than in animals with normal intraabdominal pressure in both ALI groups; (2) in extrapulmonary ALI, higher tidal volume was associated with decreased atelectasis, and lower IL-6 and caspase-3 expressions; (3) in pulmonary ALI, higher tidal volume led to higher IL-6 expression; and (4) in pulmonary ALI, liver, kidney, and villi cell apoptosis was increased, but not affected by tidal volume. Intraabdominal hypertension increased inflammation and fibrogenesis in the lung independent of ALI etiology. In extrapulmonary ALI associated with intraabdominal hypertension, higher tidal volume improved lung morphometry with lower inflammation in lung tissue. Conversely, in pulmonary ALI associated with intraabdominal hypertension, higher tidal volume increased IL-6 expression.

Lung protection: an intervention for tidal volume reduction in a teaching intensive care unit.

PubMed

Briva, Arturo; Gaiero, Cristina

2016-01-01

To determine the effect of feedback and education regarding the use of predicted body weight to adjust tidal volume in a lung-protective mechanical ventilation strategy. The study was performed from October 2014 to November 2015 (12 months) in a single university polyvalent intensive care unit. We developed a combined intervention (education and feedback), placing particular attention on the importance of adjusting tidal volumes to predicted body weight bedside. In parallel, predicted body weight was estimated from knee height and included in clinical charts. One hundred fifty-nine patients were included. Predicted body weight assessed by knee height instead of visual evaluation revealed that the delivered tidal volume was significantly higher than predicted. After the inclusion of predicted body weight, we observed a sustained reduction in delivered tidal volume from a mean (standard error) of 8.97 ± 0.32 to 7.49 ± 0.19mL/kg (p < 0.002). Furthermore, the protocol adherence was subsequently sustained for 12 months (delivered tidal volume 7.49 ± 0.54 versus 7.62 ± 0.20mL/kg; p = 0.103). The lack of a reliable method to estimate the predicted body weight is a significant impairment for the application of a worldwide standard of care during mechanical ventilation. A combined intervention based on education and repeated feedbacks promoted sustained tidal volume education during the study period (12 months).

Lung ventilation strategies for acute respiratory distress syndrome: a systematic review and network meta-analysis

PubMed Central

Wang, Changsong; Wang, Xiaoyang; Chi, Chunjie; Guo, Libo; Guo, Lei; Zhao, Nana; Wang, Weiwei; Pi, Xin; Sun, Bo; Lian, Ailing; Shi, Jinghui; Li, Enyou

2016-01-01

To identify the best lung ventilation strategy for acute respiratory distress syndrome (ARDS), we performed a network meta-analysis. The Cochrane Central Register of Controlled Trials, EMBASE, MEDLINE, CINAHL, and the Web of Science were searched, and 36 eligible articles were included. Compared with higher tidal volumes with FiO2-guided lower positive end-expiratory pressure [PEEP], the hazard ratios (HRs) for mortality were 0.624 (95% confidence interval (CI) 0.419–0.98) for lower tidal volumes with FiO2-guided lower PEEP and prone positioning and 0.572 (0.34–0.968) for pressure-controlled ventilation with FiO2-guided lower PEEP. Lower tidal volumes with FiO2-guided higher PEEP and prone positioning had the greatest potential to reduce mortality, and the possibility of receiving the first ranking was 61.6%. Permissive hypercapnia, recruitment maneuver, and low airway pressures were most likely to be the worst in terms of all-cause mortality. Compared with higher tidal volumes with FiO2-guided lower PEEP, pressure-controlled ventilation with FiO2-guided lower PEEP and lower tidal volumes with FiO2-guided lower PEEP and prone positioning ventilation are associated with lower mortality in ARDS patients. Lower tidal volumes with FiO2-guided higher PEEP and prone positioning ventilation and lower tidal volumes with pressure-volume (P–V) static curve-guided individual PEEP are potential optimal strategies for ARDS patients. PMID:26955891

Mechanical ventilation with lower tidal volumes and positive end-expiratory pressure prevents pulmonary inflammation in patients without preexisting lung injury.

PubMed

Wolthuis, Esther K; Choi, Goda; Dessing, Mark C; Bresser, Paul; Lutter, Rene; Dzoljic, Misa; van der Poll, Tom; Vroom, Margreeth B; Hollmann, Markus; Schultz, Marcus J

2008-01-01

Mechanical ventilation with high tidal volumes aggravates lung injury in patients with acute lung injury or acute respiratory distress syndrome. The authors sought to determine the effects of short-term mechanical ventilation on local inflammatory responses in patients without preexisting lung injury. Patients scheduled to undergo an elective surgical procedure (lasting > or = 5 h) were randomly assigned to mechanical ventilation with either higher tidal volumes of 12 ml/kg ideal body weight and no positive end-expiratory pressure (PEEP) or lower tidal volumes of 6 ml/kg and 10 cm H2O PEEP. After induction of anesthesia and 5 h thereafter, bronchoalveolar lavage fluid and/or blood was investigated for polymorphonuclear cell influx, changes in levels of inflammatory markers, and nucleosomes. Mechanical ventilation with lower tidal volumes and PEEP (n = 21) attenuated the increase of pulmonary levels of interleukin (IL)-8, myeloperoxidase, and elastase as seen with higher tidal volumes and no PEEP (n = 19). Only for myeloperoxidase, a difference was found between the two ventilation strategies after 5 h of mechanical ventilation (P < 0.01). Levels of tumor necrosis factor alpha, IL-1alpha, IL-1beta, IL-6, macrophage inflammatory protein 1alpha, and macrophage inflammatory protein 1beta in the bronchoalveolar lavage fluid were not affected by mechanical ventilation. Plasma levels of IL-6 and IL-8 increased with mechanical ventilation, but there were no differences between the two ventilation groups. The use of lower tidal volumes and PEEP may limit pulmonary inflammation in mechanically ventilated patients without preexisting lung injury. The specific contribution of both lower tidal volumes and PEEP on the protective effects of the lung should be further investigated.

Prone positioning reduces mortality from acute respiratory distress syndrome in the low tidal volume era: a meta-analysis

PubMed Central

Shaefi, Shahzad; Montesi, Sydney B.; Devlin, Amy; Loring, Stephen H.; Talmor, Daniel; Malhotra, Atul

2014-01-01

Purpose Prone positioning for ARDS has been performed for decades without definitive evidence of clinical benefit. A recent multicenter trial demonstrated for the first time significantly reduced mortality with prone positioning. This meta-analysis was performed to integrate these findings with existing literature and test whether differences in tidal volume explain conflicting results among randomized trials. Methods Studies were identified using MEDLINE, EMBASE, Cochrane Register of Controlled Trials, LILACS, and citation review. Included were randomized trials evaluating the effect on mortality of prone versus supine positioning during conventional ventilation for ARDS. The primary outcome was risk ratio of death at 60 days meta-analyzed using random effects models. Analysis stratified by high (>8 ml/kg predicted body weight) or low (≤8 ml/kg PBW) mean baseline tidal volume was planned a priori. Results Seven trials were identified including 2,119 patients, of whom 1,088 received prone positioning. Overall, prone positioning was not significantly associated with the risk ratio of death (RR 0.83; 95 % CI 0.68–1.02; p = 0.073; I2 = 64 %). When stratified by high or low tidal volume, prone positioning was associated with a significant decrease in RR of death only among studies with low baseline tidal volume (RR 0.66; 95 % CI 0.50–0.86; p = 0.002; I2 = 25 %). Stratification by tidal volume explained over half the between-study heterogeneity observed in the unstratified analysis. Conclusions Prone positioning is associated with significantly reduced mortality from ARDS in the low tidal volume era. Substantial heterogeneity across studies can be explained by differences in tidal volume. PMID:24435203

Airway driving pressure and lung stress in ARDS patients.

PubMed

Chiumello, Davide; Carlesso, Eleonora; Brioni, Matteo; Cressoni, Massimo

2016-08-22

Lung-protective ventilation strategy suggests the use of low tidal volume, depending on ideal body weight, and adequate levels of PEEP. However, reducing tidal volume according to ideal body weight does not always prevent overstress and overstrain. On the contrary, titrating mechanical ventilation on airway driving pressure, computed as airway pressure changes from PEEP to end-inspiratory plateau pressure, equivalent to the ratio between the tidal volume and compliance of respiratory system, should better reflect lung injury. However, possible changes in chest wall elastance could affect the reliability of airway driving pressure. The aim of this study was to evaluate if airway driving pressure could accurately predict lung stress (the pressure generated into the lung due to PEEP and tidal volume). One hundred and fifty ARDS patients were enrolled. At 5 and 15 cmH2O of PEEP, lung stress, driving pressure, lung and chest wall elastance were measured. The applied tidal volume (mL/kg of ideal body weight) was not related to lung gas volume (r (2) = 0.0005 p = 0.772). Patients were divided according to an airway driving pressure lower and equal/higher than 15 cmH2O (the lower and higher airway driving pressure groups). At both PEEP levels, the higher airway driving pressure group had a significantly higher lung stress, respiratory system and lung elastance compared to the lower airway driving pressure group. Airway driving pressure was significantly related to lung stress (r (2) = 0.581 p < 0.0001 and r (2) = 0.353 p < 0.0001 at 5 and 15 cmH2O of PEEP). For a lung stress of 24 and 26 cmH2O, the optimal cutoff value for the airway driving pressure were 15.0 cmH2O (ROC AUC 0.85, 95 % CI = 0.782-0.922); and 16.7 (ROC AUC 0.84, 95 % CI = 0.742-0.936). Airway driving pressure can detect lung overstress with an acceptable accuracy. However, further studies are needed to establish if these limits could be used for ventilator settings.

Continuous on-line measurements of respiratory system, lung and chest wall mechanics during mechanic ventilation.

PubMed

Kárason, S; Søndergaard, S; Lundin, S; Stenqvist, O

2001-08-01

We present a concept of on-line, manoeuvre-free monitoring of respiratory mechanics during dynamic conditions, displaying calculated alveolar pressure/volume curves continuously and separating lung and chest wall mechanics. Prospective observational study. Intensive care unit of a university hospital. Ten ventilator-treated patients with acute lung injury. Different positive end-expiratory pressure (PEEP) and tidal volumes, low flow inflation. Previously validated methods were used to present a single-value dynostatic compliance for the whole breath and a dynostatic volume-dependent initial, middle and final compliance within the breath. A high individual variation of respiratory mechanics was observed. Reproducibility of repeated measurements was satisfactory (coefficients of variations for dynostatic volume-dependent compliance: < or =9.2% for total respiratory system, < or =18% for lung). Volume-dependent compliance showed a statistically significant pattern of successively decreasing compliance from the initial segment through the middle and final parts within each breath at all respiratory settings. This pattern became more prominent with increasing PEEP and tidal volume, indicating a greater distension of alveoli. No lower inflection point (LIP) was seen in patients with respiratory rate 20/min and PEEP at 4 cmH2O. A trial with low flow inflation in four of the patients showed formation of a LIP in three of them and an upper inflection in one. The monitoring concept revealed a constant pattern of successively decreasing compliance within each breath, which became more prominent with increasing PEEP and tidal volume. The monitoring concept offers a simple and reliable method of monitoring respiratory mechanics during ongoing ventilator treatment.

Actual performance of mechanical ventilators in ICU: a multicentric quality control study.

PubMed

Govoni, Leonardo; Dellaca', Raffaele L; Peñuelas, Oscar; Bellani, Giacomo; Artigas, Antonio; Ferrer, Miquel; Navajas, Daniel; Pedotti, Antonio; Farré, Ramon

2012-01-01

Even if the performance of a given ventilator has been evaluated in the laboratory under very well controlled conditions, inappropriate maintenance and lack of long-term stability and accuracy of the ventilator sensors may lead to ventilation errors in actual clinical practice. The aim of this study was to evaluate the actual performances of ventilators during clinical routines. A resistance (7.69 cmH(2)O/L/s) - elastance (100 mL/cmH(2)O) test lung equipped with pressure, flow, and oxygen concentration sensors was connected to the Y-piece of all the mechanical ventilators available for patients in four intensive care units (ICUs; n = 66). Ventilators were set to volume-controlled ventilation with tidal volume = 600 mL, respiratory rate = 20 breaths/minute, positive end-expiratory pressure (PEEP) = 8 cmH(2)O, and oxygen fraction = 0.5. The signals from the sensors were recorded to compute the ventilation parameters. The average ± standard deviation and range (min-max) of the ventilatory parameters were the following: inspired tidal volume = 607 ± 36 (530-723) mL, expired tidal volume = 608 ± 36 (530-728) mL, peak pressure = 20.8 ± 2.3 (17.2-25.9) cmH(2)O, respiratory rate = 20.09 ± 0.35 (19.5-21.6) breaths/minute, PEEP = 8.43 ± 0.57 (7.26-10.8) cmH(2)O, oxygen fraction = 0.49 ± 0.014 (0.41-0.53). The more error-prone parameters were the ones related to the measure of flow. In several cases, the actual delivered mechanical ventilation was considerably different from the set one, suggesting the need for improving quality control procedures for these machines.

Lung protection: an intervention for tidal volume reduction in a teaching intensive care unit

PubMed Central

Briva, Arturo; Gaiero, Cristina

2016-01-01

Objective To determine the effect of feedback and education regarding the use of predicted body weight to adjust tidal volume in a lung-protective mechanical ventilation strategy. Methods The study was performed from October 2014 to November 2015 (12 months) in a single university polyvalent intensive care unit. We developed a combined intervention (education and feedback), placing particular attention on the importance of adjusting tidal volumes to predicted body weight bedside. In parallel, predicted body weight was estimated from knee height and included in clinical charts. Results One hundred fifty-nine patients were included. Predicted body weight assessed by knee height instead of visual evaluation revealed that the delivered tidal volume was significantly higher than predicted. After the inclusion of predicted body weight, we observed a sustained reduction in delivered tidal volume from a mean (standard error) of 8.97 ± 0.32 to 7.49 ± 0.19mL/kg (p < 0.002). Furthermore, the protocol adherence was subsequently sustained for 12 months (delivered tidal volume 7.49 ± 0.54 versus 7.62 ± 0.20mL/kg; p = 0.103). Conclusion The lack of a reliable method to estimate the predicted body weight is a significant impairment for the application of a worldwide standard of care during mechanical ventilation. A combined intervention based on education and repeated feedbacks promoted sustained tidal volume education during the study period (12 months). PMID:27925055

Effects of inhalational anaesthesia with low tidal volume ventilation on end-tidal sevoflurane and carbon dioxide concentrations: prospective randomized study.

PubMed

de la Matta-Martín, M; López-Herrera, D; Luis-Navarro, J C; López-Romero, J L

2014-02-01

We investigated how ventilation with low tidal volumes affects the pharmacokinetics of sevoflurane uptake during the first minutes of inhaled anaesthesia. Forty-eight patients scheduled for lung resection were randomly assigned to three groups. Patients in group 1, 2 and 3 received 3% sevoflurane for 3 min via face mask and controlled ventilation with a tidal volume of 2.2, 8 and 12 ml kg(-1), respectively (Phase 1). After tracheal intubation (Phase 2), 3% sevoflurane was supplied for 2 min using a tidal volume of 8 ml kg(-1) (Phase 3). End-tidal sevoflurane concentrations were significantly higher in group 1 at the end of phase 1 and lower at the end of phase 2 than in the other groups as follows: median of 2.5%, 2.2% and 2.3% in phase 1 for groups 1, 2 and 3, respectively (P<0.001); and 1.7%, 2.1% and 2.0% in phase 2, respectively (P<0.001). End-tidal carbon dioxide values in group 1 were significantly lower at the end of phase 1 and higher at the end of phase 2 than in the other groups as follows: median of 16.5, 31 and 29.5 mm Hg in phase 1 for groups 1, 2 and 3, respectively (P<0.001); and 46.2, 36 and 33.5 mm Hg in phase 2, respectively (P<0.001). When sevoflurane is administered with tidal volume approximating the airway dead space volume, end-tidal sevoflurane and end-tidal carbon dioxide may not correctly reflect the concentration of these gases in the alveoli, leading to misinterpretation of expired gas data. Copyright © 2013 Sociedad Española de Anestesiología, Reanimación y Terapéutica del Dolor. Published by Elsevier España. All rights reserved.

Important influence of respiration on human R-R interval power spectra is largely ignored

NASA Technical Reports Server (NTRS)

Brown, T. E.; Beightol, L. A.; Koh, J.; Eckberg, D. L.

1993-01-01

Frequency-domain analyses of R-R intervals are used widely to estimate levels of autonomic neural traffic to the human heart. Because respiration modulates autonomic activity, we determined for nine healthy subjects the influence of breathing frequency and tidal volume on R-R interval power spectra (fast-Fourier transform method). We also surveyed published literature to determine current practices in this burgeoning field of scientific inquiry. Supine subjects breathed at rates of 6, 7.5, 10, 15, 17.1, 20, and 24 breaths/min and with nominal tidal volumes of 1,000 and 1,500 ml. R-R interval power at respiratory and low (0.06-0.14 Hz) frequencies declined significantly as breathing frequency increased. R-R interval power at respiratory frequencies was significantly greater at a tidal volume of 1,500 than 1,000 ml. Neither breathing frequency nor tidal volume influenced average R-R intervals significantly. Our review of studies reporting human R-R interval power spectra showed that 51% of the studies controlled respiratory rate, 11% controlled tidal volume, and 11% controlled both respiratory rate and tidal volume. The major implications of our analyses are that breathing parameters strongly influence low-frequency as well as respiratory frequency R-R interval power spectra and that this influence is largely ignored in published research.

Intraoperative low tidal volume ventilation strategy has no benefits during laparoscopic cholecystectomy

PubMed Central

Arora, Vandna; Tyagi, Asha; Kumar, Surendra; Kakkar, Aanchal; Das, Shukla

2017-01-01

Background and Aims: Benefits of intraoperative low tidal volume ventilation during laparoscopic surgery are not conclusively proven, even though its advantages were seen in other situations with intraoperative respiratory compromise such as one-lung ventilation. The present study compared the efficacy of intraoperative low tidal volume ventilatory strategy (6 ml/kg along with positive end-expiratory pressure [PEEP] of 10 cmH2O) versus one with higher tidal volume (10 ml/kg with no PEEP) on various clinical parameters and plasma levels of interleukin (IL)-6 in patients undergoing laparoscopic cholecystectomy. Material and Methods: A total of 58 adult patients with American Society of Anesthesiologists physical status I or II, undergoing laparoscopic cholecystectomy were randomized to receive the low or higher tidal volume strategy as above (n = 29 each). The primary outcome measure was postoperative PaO2. Systemic levels of IL-6 along with clinical indices of intraoperative gas exchange, pulmonary mechanics, and hemodynamic consequences were measured as secondary outcome measures. Results: There was no statistically significant difference in oxygenation; intraoperative dynamic compliance, peak airway pressures, or hemodynamic parameters, or the IL-6 levels between the two groups (P > 0.05). Low tidal volume strategy was associated with significantly higher mean airway pressure, lower airway resistance, greater respiratory rates, and albeit clinically similar, higher PaCO2and lower pH (P < 0.05). Conclusion: Strategy using 6 ml/kg tidal volume along with 10 cmH2O of PEEP was not associated with any significant improvement in gas exchange, hemodynamic parameters, or systemic inflammatory response over ventilation with 10 ml/kg volume without PEEP during laparoscopic cholecystectomy. PMID:28413273

Protective ventilation reduces Pseudomonas aeruginosa growth in lung tissue in a porcine pneumonia model.

PubMed

Sperber, Jesper; Nyberg, Axel; Lipcsey, Miklos; Melhus, Åsa; Larsson, Anders; Sjölin, Jan; Castegren, Markus

2017-08-31

Mechanical ventilation with positive end expiratory pressure and low tidal volume, i.e. protective ventilation, is recommended in patients with acute respiratory distress syndrome. However, the effect of protective ventilation on bacterial growth during early pneumonia in non-injured lungs is not extensively studied. The main objectives were to compare two different ventilator settings on Pseudomonas aeruginosa growth in lung tissue and the development of lung injury. A porcine model of severe pneumonia was used. The protective group (n = 10) had an end expiratory pressure of 10 cm H 2 O and a tidal volume of 6 ml x kg -1 . The control group (n = 10) had an end expiratory pressure of 5 cm H 2 O and a tidal volume of 10 ml x kg -1 . 10 11 colony forming units of Pseudomonas aeruginosa were inoculated intra-tracheally at baseline, after which the experiment continued for 6 h. Two animals from each group received only saline, and served as sham animals. Lung tissue samples from each animal were used for bacterial cultures and wet-to-dry weight ratio measurements. The protective group displayed lower numbers of Pseudomonas aeruginosa (p < 0.05) in the lung tissue, and a lower wet-to-dry ratio (p < 0.01) than the control group. The control group deteriorated in arterial oxygen tension/inspired oxygen fraction, whereas the protective group was unchanged (p < 0.01). In early phase pneumonia, protective ventilation with lower tidal volume and higher end expiratory pressure has the potential to reduce the pulmonary bacterial burden and the development of lung injury.

Optimal ventilation of the anesthetized pediatric patient.

PubMed

Feldman, Jeffrey M

2015-01-01

Mechanical ventilation of the pediatric patient is challenging because small changes in delivered volume can be a significant fraction of the intended tidal volume. Anesthesia ventilators have traditionally been poorly suited to delivering small tidal volumes accurately, and pressure-controlled ventilation has become used commonly when caring for pediatric patients. Modern anesthesia ventilators are designed to deliver small volumes accurately to the patient's airway by compensating for the compliance of the breathing system and delivering tidal volume independent of fresh gas flow. These technology advances provide the opportunity to implement a lung-protective ventilation strategy in the operating room based upon control of tidal volume. This review will describe the capabilities of the modern anesthesia ventilator and the current understanding of lung-protective ventilation. An optimal approach to mechanical ventilation for the pediatric patient is described, emphasizing the importance of using bedside monitors to optimize the ventilation strategy for the individual patient.

Tidal volume in acute respiratory distress syndrome: how best to select it.

PubMed

Umbrello, Michele; Marino, Antonella; Chiumello, Davide

2017-07-01

Mechanical ventilation is the type of organ support most widely provided in the intensive care unit. However, this form of support does not constitute a cure for acute respiratory distress syndrome (ARDS), as it mainly works by buying time for the lungs to heal while contributing to the maintenance of vital gas exchange. Moreover, it can further damage the lung, leading to the development of a particular form of lung injury named ventilator-induced lung injury (VILI). Experimental evidence accumulated over the last 30 years highlighted the factors associated with an injurious form of mechanical ventilation. The present paper illustrates the physiological effects of delivering a tidal volume to the lungs of patients with ARDS, and suggests an approach to tidal volume selection. The relationship between tidal volume and the development of VILI, the so called volotrauma, will be reviewed. The still actual suggestion of a lung-protective ventilatory strategy based on the use of low tidal volumes scaled to the predicted body weight (PBW) will be presented, together with newer strategies such as the use of airway driving pressure as a surrogate for the amount of ventilatable lung tissue or the concept of strain, i.e., the ratio between the tidal volume delivered relative to the resting condition, that is the functional residual capacity (FRC). An ultra-low tidal volume strategy with the use of extracorporeal carbon dioxide removal (ECCO 2 R) will be presented and discussed. Eventually, the role of other ventilator-related parameters in the generation of VILI will be considered (namely, plateau pressure, airway driving pressure, respiratory rate (RR), inspiratory flow), and the promising unifying framework of mechanical power will be presented.

Tidal volume in acute respiratory distress syndrome: how best to select it

PubMed Central

Umbrello, Michele; Marino, Antonella

2017-01-01

Mechanical ventilation is the type of organ support most widely provided in the intensive care unit. However, this form of support does not constitute a cure for acute respiratory distress syndrome (ARDS), as it mainly works by buying time for the lungs to heal while contributing to the maintenance of vital gas exchange. Moreover, it can further damage the lung, leading to the development of a particular form of lung injury named ventilator-induced lung injury (VILI). Experimental evidence accumulated over the last 30 years highlighted the factors associated with an injurious form of mechanical ventilation. The present paper illustrates the physiological effects of delivering a tidal volume to the lungs of patients with ARDS, and suggests an approach to tidal volume selection. The relationship between tidal volume and the development of VILI, the so called volotrauma, will be reviewed. The still actual suggestion of a lung-protective ventilatory strategy based on the use of low tidal volumes scaled to the predicted body weight (PBW) will be presented, together with newer strategies such as the use of airway driving pressure as a surrogate for the amount of ventilatable lung tissue or the concept of strain, i.e., the ratio between the tidal volume delivered relative to the resting condition, that is the functional residual capacity (FRC). An ultra-low tidal volume strategy with the use of extracorporeal carbon dioxide removal (ECCO2R) will be presented and discussed. Eventually, the role of other ventilator-related parameters in the generation of VILI will be considered (namely, plateau pressure, airway driving pressure, respiratory rate (RR), inspiratory flow), and the promising unifying framework of mechanical power will be presented. PMID:28828362

Effect of lung-protective ventilation with lower tidal volumes on clinical outcomes among patients undergoing surgery: a meta-analysis of randomized controlled trials.

PubMed

Gu, Wan-Jie; Wang, Fei; Liu, Jing-Chen

2015-02-17

In anesthetized patients undergoing surgery, the role of lung-protective ventilation with lower tidal volumes is unclear. We performed a meta-analysis of randomized controlled trials (RCTs) to evaluate the effect of this ventilation strategy on postoperative outcomes. We searched electronic databases from inception through September 2014. We included RCTs that compared protective ventilation with lower tidal volumes and conventional ventilation with higher tidal volumes in anesthetized adults undergoing surgery. We pooled outcomes using a random-effects model. The primary outcome measures were lung injury and pulmonary infection. We included 19 trials (n=1348). Compared with patients in the control group, those who received lung-protective ventilation had a decreased risk of lung injury (risk ratio [RR] 0.36, 95% confidence interval [CI] 0.17 to 0.78; I2=0%) and pulmonary infection (RR 0.46, 95% CI 0.26 to 0.83; I2=8%), and higher levels of arterial partial pressure of carbon dioxide (standardized mean difference 0.47, 95% CI 0.18 to 0.75; I2=65%). No significant differences were observed between the patient groups in atelectasis, mortality, length of hospital stay, length of stay in the intensive care unit or the ratio of arterial partial pressure of oxygen to fraction of inspired oxygen. Anesthetized patients who received ventilation with lower tidal volumes during surgery had a lower risk of lung injury and pulmonary infection than those given conventional ventilation with higher tidal volumes. Implementation of a lung-protective ventilation strategy with lower tidal volumes may lower the incidence of these outcomes. © 2015 Canadian Medical Association or its licensors.

Measurement of tidal volume using respiratory ultrasonic plethysmography in anaesthetized, mechanically ventilated horses.

PubMed

Russold, Elena; Ambrisko, Tamas D; Schramel, Johannes P; Auer, Ulrike; Van Den Hoven, Rene; Moens, Yves P

2013-01-01

To compare tidal volume estimations obtained from Respiratory Ultrasonic Plethysmography (RUP) with simultaneous spirometric measurements in anaesthetized, mechanically ventilated horses. Prospective randomized experimental study. Five experimental horses. Five horses were anaesthetized twice (1 week apart) in random order in lateral and in dorsal recumbency. Nine ventilation modes (treatments) were scheduled in random order (each lasting 4 minutes) applying combinations of different tidal volumes (8, 10, 12 mL kg(-1)) and positive end-expiratory pressures (PEEP) (0, 10, 20 cm H(2)O). Baseline ventilation mode (tidal volume=15 mL kg(-1), PEEP=0 cm H(2)O) was applied for 4 minutes between all treatments. Spirometry and RUP data were downloaded to personal computers. Linear regression analyses (RUP versus spirometric tidal volume) were performed using different subsets of data. Additonally RUP was calibrated against spirometry using a regression equation for all RUP signal values (thoracic, abdominal and combined) with all data collectively and also by an individually determined best regression equation (highest R(2)) for each experiment (horse versus recumbency) separately. Agreement between methods was assessed with Bland-Altman analyses. The highest correlation of RUP and spirometric tidal volume (R(2)=0.81) was found with the combined RUP signal in horses in lateral recumbency and ventilated without PEEP. The bias ±2 SD was 0±2.66 L when RUP was calibrated for collective data, but decreased to 0±0.87 L when RUP was calibrated with individual data. A possible use of RUP for tidal volume measurement during IPPV needs individual calibration to obtain limits of agreement within ±20%. © 2012 The Authors. Veterinary Anaesthesia and Analgesia. © 2012 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesiologists.

A normal mode treatment of semi-diurnal body tides on an aspherical, rotating and anelastic Earth

NASA Astrophysics Data System (ADS)

Lau, Harriet C. P.; Yang, Hsin-Ying; Tromp, Jeroen; Mitrovica, Jerry X.; Latychev, Konstantin; Al-Attar, David

2015-08-01

Normal mode treatments of the Earth's body tide response were developed in the 1980s to account for the effects of Earth rotation, ellipticity, anelasticity and resonant excitation within the diurnal band. Recent space-geodetic measurements of the Earth's crustal displacement in response to luni-solar tidal forcings have revealed geographical variations that are indicative of aspherical deep mantle structure, thus providing a novel data set for constraining deep mantle elastic and density structure. In light of this, we make use of advances in seismic free oscillation literature to develop a new, generalized normal mode theory for the tidal response within the semi-diurnal and long-period tidal band. Our theory involves a perturbation method that permits an efficient calculation of the impact of aspherical structure on the tidal response. In addition, we introduce a normal mode treatment of anelasticity that is distinct from both earlier work in body tides and the approach adopted in free oscillation seismology. We present several simple numerical applications of the new theory. First, we compute the tidal response of a spherically symmetric, non-rotating, elastic and isotropic Earth model and demonstrate that our predictions match those based on standard Love number theory. Second, we compute perturbations to this response associated with mantle anelasticity and demonstrate that the usual set of seismic modes adopted for this purpose must be augmented by a family of relaxation modes to accurately capture the full effect of anelasticity on the body tide response. Finally, we explore aspherical effects including rotation and we benchmark results from several illustrative case studies of aspherical Earth structure against independent finite-volume numerical calculations of the semi-diurnal body tide response. These tests confirm the accuracy of the normal mode methodology to at least the level of numerical error in the finite-volume predictions. They also demonstrate that full coupling of normal modes, rather than group coupling, is necessary for accurate predictions of the body tide response.

Low Tidal Volume Ventilation in Patients without Acute Respiratory Distress Syndrome: A Paradigm Shift in Mechanical Ventilation

PubMed Central

Lipes, Jed; Bojmehrani, Azadeh; Lellouche, Francois

2012-01-01

Protective ventilation with low tidal volume has been shown to reduce morbidity and mortality in patients suffering from acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). Low tidal volume ventilation is associated with particular clinical challenges and is therefore often underutilized as a therapeutic option in clinical practice. Despite some potential difficulties, data have been published examining the application of protective ventilation in patients without lung injury. We will briefly review the physiologic rationale for low tidal volume ventilation and explore the current evidence for protective ventilation in patients without lung injury. In addition, we will explore some of the potential reasons for its underuse and provide strategies to overcome some of the associated clinical challenges. PMID:22536499

Mechanical ventilation in abdominal surgery.

PubMed

Futier, E; Godet, T; Millot, A; Constantin, J-M; Jaber, S

2014-01-01

One of the key challenges in perioperative care is to reduce postoperative morbidity and mortality. Patients who develop postoperative morbidity but survive to leave hospital have often reduced functional independence and long-term survival. Mechanical ventilation provides a specific example that may help us to shift thinking from treatment to prevention of postoperative complications. Mechanical ventilation in patients undergoing surgery has long been considered only as a modality to ensure gas exchange while allowing maintenance of anesthesia with delivery of inhaled anesthetics. Evidence is accumulating, however, suggesting an association between intraoperative mechanical ventilation strategy and postoperative pulmonary function and clinical outcome in patients undergoing abdominal surgery. Non-protective ventilator settings, especially high tidal volume (VT) (>10-12mL/kg) and the use of very low level of positive end-expiratory pressure (PEEP) (PEEP<5cmH2O) or no PEEP, may cause alveolar overdistension and repetitive tidal recruitment leading to ventilator-associated lung injury in patients with healthy lungs. Stimulated by previous findings in patients with acute respiratory distress syndrome, the use of lower tidal volume ventilation is becoming increasingly more common in the operating room. However, lowering tidal volume, though important, is only part of the overall multifaceted approach of lung protective mechanical ventilation. In this review, we aimed at providing the most recent and relevant clinical evidence regarding the use of mechanical ventilation in patients undergoing abdominal surgery. Copyright © 2014 Société française d’anesthésie et de réanimation (Sfar). Published by Elsevier SAS. All rights reserved.

Methodology for classification of geographical features with remote sensing images: Application to tidal flats

NASA Astrophysics Data System (ADS)

Revollo Sarmiento, G. N.; Cipolletti, M. P.; Perillo, M. M.; Delrieux, C. A.; Perillo, Gerardo M. E.

2016-03-01

Tidal flats generally exhibit ponds of diverse size, shape, orientation and origin. Studying the genesis, evolution, stability and erosive mechanisms of these geographic features is critical to understand the dynamics of coastal wetlands. However, monitoring these locations through direct access is hard and expensive, not always feasible, and environmentally damaging. Processing remote sensing images is a natural alternative for the extraction of qualitative and quantitative data due to their non-invasive nature. In this work, a robust methodology for automatic classification of ponds and tidal creeks in tidal flats using Google Earth images is proposed. The applicability of our method is tested in nine zones with different morphological settings. Each zone is processed by a segmentation stage, where ponds and tidal creeks are identified. Next, each geographical feature is measured and a set of shape descriptors is calculated. This dataset, together with a-priori classification of each geographical feature, is used to define a regression model, which allows an extensive automatic classification of large volumes of data discriminating ponds and tidal creeks against other various geographical features. In all cases, we identified and automatically classified different geographic features with an average accuracy over 90% (89.7% in the worst case, and 99.4% in the best case). These results show the feasibility of using freely available Google Earth imagery for the automatic identification and classification of complex geographical features. Also, the presented methodology may be easily applied in other wetlands of the world and perhaps employing other remote sensing imagery.

A quasi-experimental, before-after trial examining the impact of an emergency department mechanical ventilator protocol on clinical outcomes and lung-protective ventilation in acute respiratory distress syndrome

PubMed Central

Fuller, Brian M.; Ferguson, Ian T.; Mohr, Nicholas M.; Drewry, Anne M.; Palmer, Christopher; Wessman, Brian T.; Ablordeppey, Enyo; Keeperman, Jacob; Stephens, Robert J.; Briscoe, Cristopher C.; Kolomiets, Angelina A.; Hotchkiss, Richard S.; Kollef, Marin H.

2017-01-01

Objective To evaluate the impact of an emergency department (ED) mechanical ventilation protocol on clinical outcomes and adherence to lung-protective ventilation in patients with acute respiratory distress syndrome (ARDS). Design Quasi-experimental, before-after trial. Setting ED and intensive care units (ICU) of an academic center. Patients Mechanically ventilated ED patients experiencing ARDS while in the ED or after admission to the ICU. Interventions An ED ventilator protocol which targeted parameters in need of quality improvement, as identified by prior work: 1) lung-protective tidal volume; 2) appropriate setting of positive end-expiratory pressure (PEEP); 3) oxygen weaning; and 4) head-of-bed elevation. Measurements and Main Results A total of 229 patients (186 pre-intervention group, 43 intervention group) were studied. In the ED, the intervention was associated with significant changes (P < 0.01 for all) in tidal volume, PEEP, respiratory rate, oxygen administration, and head-of-bed elevation. There was a reduction in ED tidal volume from 8.1 mL/kg PBW (7.0 – 9.1) to 6.4 mL/kg PBW (6.1 – 6.7), and an increase in lung-protective ventilation from 11.1% to 61.5%, P < 0.01. The intervention was associated with a reduction in mortality from 54.8% to 39.5% (OR 0.38, 95% CI 0.17 – 0.83, P = 0.02), and a 3.9 day increase in ventilator-free days, P = 0.01. Conclusions This before-after study of mechanically ventilated patients with ARDS demonstrates that implementing a mechanical ventilator protocol in the ED is feasible, and associated with improved clinical outcomes. PMID:28157140

An in vitro evaluation of the influence of neonatal endotracheal tube diameter and length on the work of breathing.

PubMed

Miyake, Fuyu; Suga, Rika; Akiyama, Takahiro; Namba, Fumihiko

2018-04-06

Neonates, particularly premature babies, are often managed with endotracheal intubation and subsequent mechanical ventilation to maintain adequate pulmonary gas exchange. There is no consensus on the standard length of endotracheal tube. Although a short tube reduces resistance and respiratory dead space, it is believed to increase the risk of accidental extubation. There are not entirely coherent data regarding the effect of endotracheal tube length on work of breathing in infants. The aim of this study was to evaluate the impact of neonatal endotracheal tube diameter and length on the work of breathing using an infant in vitro lung model. We assessed the work of breathing index and mechanical ventilation settings with various endotracheal tube diameters and lengths using the JTR100 in vitro infant lung model. The basic parameters of the model were breathing frequency of 20 per minutes, inspiratory-expiratory ratio of 1:3, and positive end-expiratory pressure of 5 cmH 2 O. In addition, the diaphragm driving pressure to maintain the set tidal volume was measured as the work of breathing index. The JTR100 was connected to the Babylog 8000plus through the endotracheal tube. Finally, we monitored the peak inspiratory pressure generated during assist-control volume guarantee mode with a targeted tidal volume of 10-30 mL. The diaphragm driving pressure using a 2.0-mm inner diameter tube was twice as high as that using a 4.0-mm inner diameter tube. To maintain the targeted tidal volume, a shorter tube reduced both the diaphragm driving pressure and ventilator-generated peak inspiratory pressure. The difference in the generated peak inspiratory pressure between the shortest and longest tubes was 5 cmH 2 O. In our infant lung model, a shorter tube resulted in a lower work of breathing and lower ventilator-generated peak inspiratory pressure. © 2018 John Wiley & Sons Ltd.

A bench evaluation of fraction of oxygen in air delivery and tidal volume accuracy in home care ventilators available for hospital use

PubMed Central

Baboi, Loredana; Subtil, Fabien

2016-01-01

Background Turbine-powered ventilators are not only designed for long-term ventilation at home but also for hospital use. It is important to verify their capabilities in delivering fraction of oxygen in air (FIO2) and tidal volume (VT). Methods We assessed the FIO2 accuracy and the VT delivery in four home care ventilators (HCV) on the bench. The four HCV were Astral 150, Elisée 150, Monnal T50 and Trilogy 200 HCV, which were connected to a lung model (ASL 5000). For assessing FIO2 accuracy, lung model was set to mimic an obstructive lung and HCV were set in volume controlled mode (VC). They supplied with air, 3 or 15 L/min oxygen and FIO2 was measured by using a ventilator tester (Citrex H4TM). For the VT accuracy, the lung model was set in a way to mimic three adult configurations (normal, obstructive, or restrictive respiratory disorder) and one pediatric configuration. Each HCV was set in VC. Two VT (300 and 500 mL) in adult lung configuration and one 50 mL VT in pediatric lung configuration, at two positive end expiratory pressures 5 and 10 cmH2O, were tested. VT accuracy was measured as volume error (the relative difference between set and measured VT). Statistical analysis was performed by suing one-factor ANOVA with a Bonferroni correction for multiple tests. Results For Astral 150, Elisée 150, Monnal T50 and Trilogy 200, FIO2 averaged 99.2%, 93.7%, 86.3%, and 62.1%, respectively, at 15 L/min oxygen supplementation rate (P<0.001). Volume error was 0.5%±0%, −38%±0%, −9%±0%, −29%±0% and −36%±0% for pediatric lung condition (P<0.001). In adult lung configurations, Monnal T50 systematically over delivered VT and Trilogy 150 was sensitive to lung configuration when VT was set to 300 mL at either positive end-expiratory pressure (PEEP). Conclusions HCV are different in terms of FIO2 efficiency and VT delivery. PMID:28149559

Variability in Usual Care Mechanical Ventilation for Pediatric Acute Respiratory Distress Syndrome: Time for a Decision Support Protocol?

PubMed

Newth, Christopher J L; Sward, Katherine A; Khemani, Robinder G; Page, Kent; Meert, Kathleen L; Carcillo, Joseph A; Shanley, Thomas P; Moler, Frank W; Pollack, Murray M; Dalton, Heidi J; Wessel, David L; Berger, John T; Berg, Robert A; Harrison, Rick E; Holubkov, Richard; Doctor, Allan; Dean, J Michael; Jenkins, Tammara L; Nicholson, Carol E

2017-11-01

Although pediatric intensivists philosophically embrace lung protective ventilation for acute lung injury and acute respiratory distress syndrome, we hypothesized that ventilator management varies. We assessed ventilator management by evaluating changes to ventilator settings in response to blood gases, pulse oximetry, or end-tidal CO2. We also assessed the potential impact that a pediatric mechanical ventilation protocol adapted from National Heart Lung and Blood Institute acute respiratory distress syndrome network protocols could have on reducing variability by comparing actual changes in ventilator settings to those recommended by the protocol. Prospective observational study. Eight tertiary care U.S. PICUs, October 2011 to April 2012. One hundred twenty patients (age range 17 d to 18 yr) with acute lung injury/acute respiratory distress syndrome. Two thousand hundred arterial and capillary blood gases, 3,964 oxygen saturation by pulse oximetry, and 2,757 end-tidal CO2 values were associated with 3,983 ventilator settings. Ventilation mode at study onset was pressure control 60%, volume control 19%, pressure-regulated volume control 18%, and high-frequency oscillatory ventilation 3%. Clinicians changed FIO2 by ±5 or ±10% increments every 8 hours. Positive end-expiratory pressure was limited at ~10 cm H2O as oxygenation worsened, lower than would have been recommended by the protocol. In the first 72 hours of mechanical ventilation, maximum tidal volume/kg using predicted versus actual body weight was 10.3 (8.5-12.9) (median [interquartile range]) versus 9.2 mL/kg (7.6-12.0) (p < 0.001). Intensivists made changes similar to protocol recommendations 29% of the time, opposite to the protocol's recommendation 12% of the time and no changes 56% of the time. Ventilator management varies substantially in children with acute respiratory distress syndrome. Opportunities exist to minimize variability and potentially injurious ventilator settings by using a pediatric mechanical ventilation protocol offering adequately explicit instructions for given clinical situations. An accepted protocol could also reduce confounding by mechanical ventilation management in a clinical trial.

Accuracy of height estimation and tidal volume setting using anthropometric formulas in an ICU Caucasian population.

PubMed

L'her, Erwan; Martin-Babau, Jérôme; Lellouche, François

2016-12-01

Knowledge of patients' height is essential for daily practice in the intensive care unit. However, actual height measurements are unavailable on a daily routine in the ICU and measured height in the supine position and/or visual estimates may lack consistency. Clinicians do need simple and rapid methods to estimate the patients' height, especially in short height and/or obese patients. The objectives of the study were to evaluate several anthropometric formulas for height estimation on healthy volunteers and to test whether several of these estimates will help tidal volume setting in ICU patients. This was a prospective, observational study in a medical intensive care unit of a university hospital. During the first phase of the study, eight limb measurements were performed on 60 healthy volunteers and 18 height estimation formulas were tested. During the second phase, four height estimates were performed on 60 consecutive ICU patients under mechanical ventilation. In the 60 healthy volunteers, actual height was well correlated with the gold standard, measured height in the erect position. Correlation was low between actual and calculated height, using the hand's length and width, the index, or the foot equations. The Chumlea method and its simplified version, performed in the supine position, provided adequate estimates. In the 60 ICU patients, calculated height using the simplified Chumlea method was well correlated with measured height (r = 0.78; ∂ < 1 %). Ulna and tibia estimates also provided valuable estimates. All these height estimates allowed calculating IBW or PBW that were significantly different from the patients' actual weight on admission. In most cases, tidal volume set according to these estimates was lower than what would have been set using the actual weight. When actual height is unavailable in ICU patients undergoing mechanical ventilation, alternative anthropometric methods to obtain patient's height based on lower leg and on forearm measurements could be useful to facilitate the application of protective mechanical ventilation in a Caucasian ICU population. The simplified Chumlea method is easy to achieve in a bed-ridden patient and provides accurate height estimates, with a low bias.

Passive continuous positive airway pressure ventilation during cardiopulmonary resuscitation: a randomized cross-over manikin simulation study.

PubMed

Winkler, Bernd E; Muellenbach, Ralf M; Wurmb, Thomas; Struck, Manuel F; Roewer, Norbert; Kranke, Peter

2017-02-01

While controlled ventilation is most frequently used during cardiopulmonary resuscitation (CPR), the application of continuous positive airway pressure (CPAP) and passive ventilation of the lung synchronously with chest compressions and decompressions might represent a promising alternative approach. One benefit of CPAP during CPR is the reduction of peak airway pressures and therefore a potential enhancement in haemodynamics. We therefore evaluated the tidal volumes and airway pressures achieved during CPAP-CPR. During CPR with the LUCAS™ 2 compression device, a manikin model was passively ventilated at CPAP levels of 5, 10, 20 and 30 hPa with the Boussignac tracheal tube and the ventilators Evita ® V500, Medumat ® Transport, Oxylator ® EMX, Oxylog ® 2000, Oxylog ® 3000, Primus ® and Servo ® -i as well as the Wenoll ® diver rescue system. Tidal volumes and airway pressures during CPAP-CPR were recorded and analyzed. Tidal volumes during CPAP-CPR were higher than during compression-only CPR without positive airway pressure. The passively generated tidal volumes increased with increasing CPAP levels and were significantly influenced by the ventilators used. During ventilation at 20 hPa CPAP via a tracheal tube, the mean tidal volumes ranged from 125 ml (Medumat ® ) to 309 ml (Wenoll ® ) and the peak airway pressures from 23 hPa (Primus ® ) to 49 hPa (Oxylog ® 3000). Transport ventilators generated lower tidal volumes than intensive care ventilators or closed-circuit systems. Peak airway pressures during CPAP-CPR were lower than those during controlled ventilation CPR reported in literature. High peak airway pressures are known to limit the applicability of ventilation via facemask or via supraglottic airway devices and may adversely affect haemodynamics. Hence, the application of ventilators generating high tidal volumes with low peak airway pressures appears desirable during CPAP-CPR. The limited CPAP-CPR capabilities of transport ventilators in our study might be prerequisite for future developments of transport ventilators.

Circuit compliance compensation in lung protective ventilation.

PubMed

Masselli, Grazia Maria Pia; Silvestri, Sergio; Sciuto, Salvatore Andrea; Cappa, Paolo

2006-01-01

Lung protective ventilation utilizes low tidal volumes to ventilate patients with severe lung pathologies. The compensation of breathing circuit effects, i.e. those induced by compressible volume of the circuit, results particularly critical in the calculation of the actual tidal volume delivered to patient's respiratory system which in turns is responsible of the level of permissive hypercapnia. The present work analyzes the applicability of the equation for circuit compressible volume compensation in the case of pressure and volume controlled lung protective ventilation. Experimental tests conducted in-vitro show that the actual tidal volume can be reliably estimated if the compliance of the breathing circuit is measured with the same parameters and ventilation technique that will be utilized in lung protective ventilation. Differences between volume and pressure controlled ventilation are also quantitatively assessed showing that pressure controlled ventilation allows a more reliable compensation of breathing circuit compressible volume.

Application of intraoperative lung-protective ventilation varies in accordance with the knowledge of anaesthesiologists: a single-Centre questionnaire study and a retrospective observational study.

PubMed

Kim, Seung Hyun; Na, Sungwon; Lee, Woo Kyung; Choi, Hyunwoo; Kim, Jeongmin

2018-04-02

The benefits of lung-protective ventilation (LPV) with a low tidal volume (6 mL/kg of ideal body weight [IBW]), limited plateau pressure (< 28-30 cm H 2 O), and appropriate positive end-expiratory pressure (PEEP) in patients with acute respiratory distress syndrome have become apparent and it is now widely adopted in intensive care units. Recently evidence for LPV in general anaesthesia has been accumulated, but it is not yet generally applied by anaesthesiologists in the operating room. This study investigated the perception about intraoperative LPV among 82 anaesthesiologists through a questionnaire survey and identified the differences in ventilator settings according to recognition of lung-protective ventilation. Furthermore, we investigated the changes in the trend for using this form of ventilation during general anaesthesia in the past 10 years. Anaesthesiologists who had received training in LPV were more knowledgeable about this approach. Anaesthesiologists with knowledge of the concept behind LPV strategies applied a lower tidal volume (median (IQR [range]), 8.2 (8.0-9.2 [7.1-10.3]) vs. 9.2 (9.1-10.1 [7.6-10.1]) mL/kg; p = 0.033) and used PEEP more frequently (69/72 [95.8%] vs. 5/8 [62.5%]; p = 0.012; odds ratio, 13.8 [2.19-86.9]) for laparoscopic surgery than did those without such knowledge. Anaesthesiologists who were able to answer a question related to LPV correctly (respondents who chose 'height' to a multiple choice question asking what variables should be considered most important in the initial setting of tidal volume) applied a lower tidal volume in cases of laparoscopic surgery and obese patients. There was an increase in the number of patients receiving LPV (V T  < 10 mL/kgIBW and PEEP ≥5 cm H 2 O) between 2004 and 2014 (0/818 [0.0%] vs. 280/818 [34.2%]; p <  0.001). Our study suggests that the knowledge of LPV is directly related to its implementation, and can explain the increase in LPV use in general anaesthesia. Further studies should assess the impact of using intraoperative LPV on clinical outcomes and should determine the efficacy of education on intraoperative LPV implementation.

Comparison of lung protective ventilation strategies in a rabbit model of acute lung injury.

PubMed

Rotta, A T; Gunnarsson, B; Fuhrman, B P; Hernan, L J; Steinhorn, D M

2001-11-01

To determine the impact of different protective and nonprotective mechanical ventilation strategies on the degree of pulmonary inflammation, oxidative damage, and hemodynamic stability in a saline lavage model of acute lung injury. A prospective, randomized, controlled, in vivo animal laboratory study. Animal research facility of a health sciences university. Forty-six New Zealand White rabbits. Mature rabbits were instrumented with a tracheostomy and vascular catheters. Lavage-injured rabbits were randomized to receive conventional ventilation with either a) low peak end-expiratory pressure (PEEP; tidal volume of 10 mL/kg, PEEP of 2 cm H2O); b) high PEEP (tidal volume of 10 mL/kg, PEEP of 10 cm H2O); c) low tidal volume with PEEP above Pflex (open lung strategy, tidal volume of 6 mL/kg, PEEP set 2 cm H2O > Pflex); or d) high-frequency oscillatory ventilation. Animals were ventilated for 4 hrs. Lung lavage fluid and tissue samples were obtained immediately after animals were killed. Lung lavage fluid was assayed for measurements of total protein, elastase activity, tumor necrosis factor-alpha, and malondialdehyde. Lung tissue homogenates were assayed for measurements of myeloperoxidase activity and malondialdehyde. The need for inotropic support was recorded. Animals that received a lung protective strategy (open lung or high-frequency oscillatory ventilation) exhibited more favorable oxygenation and lung mechanics compared with the low PEEP and high PEEP groups. Animals ventilated by a lung protective strategy also showed attenuation of inflammation (reduced tracheal fluid protein, tracheal fluid elastase, tracheal fluid tumor necrosis factor-alpha, and pulmonary leukostasis). Animals treated with high-frequency oscillatory ventilation had attenuated oxidative injury to the lung and greater hemodynamic stability compared with the other experimental groups. Both lung protective strategies were associated with improved oxygenation, attenuated inflammation, and decreased lung damage. However, in this small-animal model of acute lung injury, an open lung strategy with deliberate hypercapnia was associated with significant hemodynamic instability.

Clinical impact of leak compensation during non-invasive ventilation.

PubMed

Storre, Jan Hendrik; Bohm, Philipp; Dreher, Michael; Windisch, Wolfram

2009-10-01

This study aimed to assess the impact of leak compensation capabilities during pressure- and volume-limited non-invasive positive-pressure ventilation (NPPV) in COPD patients. Fourteen patients with stable hypercapnic COPD who were receiving long-term NPPV were included in the study. For both modes of NPPV, a full face mask and an artificial leak in the ventilatory circuit were used at three different settings, and applied during daytime NPPV, either without leakage (setting I), with leakage during inspiration only (setting II), and with leakage during inspiration and expiration (setting III). Ventilation pattern was pneumotachy-graphically recorded. NPPV was feasible with negligible leak volumes, indicating optimal mask fitting during the daytime (setting I). In the presence of leakage (settings II and III), the attempt to compensate for leak was only evident during pressure-limited NPPV, since inspiratory volumes delivered by the ventilator increased from 726+/-129 (setting I) to 1104+/-164 (setting II), and to 1257+/-166 (setting III) ml during pressure-limited NPPV, respectively (all p<0.001); however, they remained stable during volume-limited NPPV. Leak compensation resulted in a decrease in leakage-induced dyspnea. However, 83%/87% (setting II/III) of the additionally-delivered inspiratory volume during pressure-limited NPPV was also lost via leakage. Expiratory volume was higher in setting II compared to setting III (both p<0.001), indicating the presence of significant expiratory leakage. The attempt at leak compensation largely feeds the leakage itself and only results in a marginal increase of tidal volume. However, pressure-limited--but not volume-limited--NPPV results in a clinically-important leak compensation in vivo. www.uniklinik-freiburg.de/zks/live/uklregister/Oeffentlich.html Identifier: UKF001272.

Effects of a preemptive alveolar recruitment strategy on arterial oxygenation during one-lung ventilation with different tidal volumes in patients with normal pulmonary function test.

PubMed

Jung, Jong Dal; Kim, Sang Hun; Yu, Byung Sik; Kim, Hye Ji

2014-08-01

Hypoxemia during one-lung ventilation (OLV) remains a major concern. The present study compared the effect of alveolar recruitment strategy (ARS) on arterial oxygenation during OLV at varying tidal volumes (Vt) with or without positive end-expiratory pressure (PEEP). In total, 120 patients undergoing wedge resection by video assisted thoracostomy were randomized into four groups comprising 30 patients each: those administered a 10 ml/kg tidal volume with or without preemptive ARS (Group H and Group H-ARS, respectively) and those administered a 6 ml/kg tidal volume and a 8 cmH2O PEEP with or without preemptive ARS (Group L and Group L-ARS, respectively). ARS was performed using pressure-controlled ventilation with a 40 cmH2O plateau airway pressure and a 15 cmH2O PEEP for at least 10 breaths until OLV began. Preemptive ARS significantly improved the PaO2/FiO2 ratio compared to the groups that did not receive ARS (P < 0.05). The H-ARS group showed a highest PaO2/FiO2 ratio during OLV, the L-ARS and H groups showed similarly improved arterial oxygenation, which was significantly higher than in group L (P < 0.05). The plateau airway pressure in group H-ARS was significantly higher than in group L-ARS (P < 0.05). Preemptive ARS can improve arterial oxygenation during OLV. Furthermore, a 6 ml/kg tidal volume combined with 8 cmH2O PEEP after preemptive ARS may reduce the risk of pulmonary injury caused by high tidal volume during one-lung ventilation in patients with normal pulmonary function.

Factors associated with elevated plateau pressure in patients with acute lung injury receiving lower tidal volume ventilation.

PubMed

Prescott, Hallie C; Brower, Roy G; Cooke, Colin R; Phillips, Gary; O'Brien, James M

2013-03-01

Lung-protective ventilation with lower tidal volume and lower plateau pressure improves mortality in patients with acute lung injury and acute respiratory distress syndrome. We sought to determine the incidence of elevated plateau pressure in acute lung injury /acute respiratory distress syndrome patients receiving lower tidal volume ventilation and to determine the factors that predict elevated plateau pressure in these patients. We used data from 1398 participants in Acute Respiratory Distress Syndrome Network trials, who received lower tidal volume ventilation (≤ 6.5mL/kg predicted body weight). We considered patients with a plateau pressure greater than 30cm H2O and/or a tidal volume less than 5.5mL/kg predicted body weight on study day 1 to have "elevated plateau pressure." We used logistic regression to identify baseline clinical variables associated with elevated plateau pressure and to develop a model to predict elevated plateau pressure using a subset of 1,188 patients. We validated the model in the 210 patients not used for model development. Medical centers participating in Acute Respiratory Distress Syndrome Network clinical trials. None. Of the 1,398 patients in our study, 288 (20.6%) had elevated plateau pressure on day 1. Severity of illness indices and demographic factors (younger age, greater body mass index, and non-white race) were independently associated with elevated plateau pressure. The multivariable logistic regression model for predicting elevated plateau pressure had an area under the receiving operator characteristic curve of 0.71 for both the developmental and the validation subsets. acute lung injury patients receiving lower tidal volume ventilation often have a plateau pressure that exceeds Acute Respiratory Distress Syndrome Network goals. Race, body mass index, and severity of lung injury are each independently associated with elevated plateau pressure. Selecting a smaller initial tidal volume for non-white patients and patients with higher severity of illness may decrease the incidence of elevated plateau pressure. Prospective studies are needed to evaluate this approach.

Convexity, Jensen's inequality, and benefits of noisy or biologically variable life support (Keynote Address)

NASA Astrophysics Data System (ADS)

Mutch, W. Alan C.

2005-05-01

Life support with a mechanical ventilator is used to manage patients with a variety of lung diseases including acute respiratory distress syndrome (ARDS). Recently, management of ARDS has concentrated on ventilating at lower airway pressure using lower tidal volume. A large international study demonstrated a 22% reduction in mortality with the low tidal volume approach. The potential advantages of adding physiologic noise with fractal characteristics to the respiratory rate and tidal volume as delivered by a mechanical ventilator are discussed. A so-called biologically variable ventilator (BVV), incorporating such noise, has been developed. Here we show that the benefits of noisy ventilation - at lower tidal volumes - can be deduced from a simple probabilistic result known as Jensen"s Inequality. Using the local convexity of the pressure-volume relationship in the lung we demonstrate that the addition of noise results in higher mean tidal volume or lower mean airway pressure. The consequence is enhanced gas exchange or less stress on the lungs, both clinically desirable. Jensen"s Inequality has important considerations in engineering, information theory and thermodynamics. Here is an example of the concept applied to medicine that may have important considerations for the clinical management of critically ill patients. Life support devices, such as mechanical ventilators, are of vital use in critical care units and operating rooms. These devices usually have monotonous output. Improving mechanical ventilators and other life support devices may be as simple as adding noise to their output signals.

One-Lung Ventilation with Additional Ipsilateral Ventilation of Low Tidal Volume and High Frequency in Lung Lobectomy

PubMed Central

Feng, Yong; Wang, Jianyue; Zhang, Yang; Wang, Shiduan

2016-01-01

Background To investigate the protective effects of additional ipsilateral ventilation of low tidal volume and high frequency on lung functions in the patients receiving lobectomy. Material/Methods Sixty patients receiving lung lobectomy were randomized into the conventional one-lung ventilation (CV) group (n=30) and the ipsilateral low tidal volume high frequency ventilation (LV) group (n=30). In the CV group, patients received only contralateral OLV. In the LV group, patients received contralateral ventilation and additional ipsilateral ventilation of low tidal volume of 1–2 ml/kg and high frequency of 40 times/min. Normal lung tissues were biopsied for the analysis of lung injury. Lung injury was scored by evaluating interstitial edema, alveolar edema, neutrophil infiltration, and alveolar congestion. Results At 30 min and 60 min after the initiation of one-lung ventilation and after surgery, patients in the LV group showed significantly higher ratio of the partial pressure of arterial oxygen to the fraction of inspired oxygen than those in the CV group (P<0.001). Lung injury was significantly less severe (2.7±0.7) in the LV group than in the CV group (3.1±0.7) (P=0.006). Conclusions Additional ipsilateral ventilation of low tidal volume and high frequency can decrease the risk of hypoxemia and alleviate lung injury in patients receiving lobectomy. PMID:27166086

Extracorporeal membrane oxygenation (ECMO) as a treatment strategy for severe acute respiratory distress syndrome (ARDS) in the low tidal volume era: A systematic review.

PubMed

Tillmann, Bourke W; Klingel, Michelle L; Iansavichene, Alla E; Ball, Ian M; Nagpal, A Dave

2017-10-01

To evaluate the hospital survival in patients with severe ARDS managed with ECMO and low tidal volume ventilation as compared to patients managed with low tidal volume ventilation alone. Electronic databases were searched for studies of at least 10 adult patients with severe ARDS comparing the use of ECMO with low tidal volume ventilation to mechanical ventilation with a low tidal volume alone. Only studies reporting hospital or ICU survival were included. All identified studies were assessed independently by two reviewers. Of 1782 citations, 27 studies (n=1674) met inclusion criteria. Hospital survival for ECMO patients ranged from 33.3 to 86%, while survival with conventional therapy ranged from 36.3 to 71.2%. Five studies were identified with appropriate control groups allowing comparison, but due to the high degree of variability between studies (I 2 =63%), their results could not be pooled. Two of these studies demonstrated a significant difference, both favouring ECMO over conventional therapy. Given the lack of studies with appropriate control groups, our confidence in a difference in outcome between the two therapies remains weak. Future studies on the use of ECMO for severe ARDS are needed to clarify the role of ECMO in this disease. Copyright © 2017 Elsevier Inc. All rights reserved.

Physiological mechanisms of dyspnea during exercise with external thoracic restriction: Role of increased neural respiratory drive

PubMed Central

Mendonca, Cassandra T.; Schaeffer, Michele R.; Riley, Patrick

2013-01-01

We tested the hypothesis that neuromechanical uncoupling of the respiratory system forms the mechanistic basis of dyspnea during exercise in the setting of “abnormal” restrictive constraints on ventilation (VE). To this end, we examined the effect of chest wall strapping (CWS) sufficient to mimic a “mild” restrictive lung deficit on the interrelationships between VE, breathing pattern, dynamic operating lung volumes, esophageal electrode-balloon catheter-derived measures of the diaphragm electromyogram (EMGdi) and the transdiaphragmatic pressure time product (PTPdi), and sensory intensity and unpleasantness ratings of dyspnea during exercise. Twenty healthy men aged 25.7 ± 1.1 years (means ± SE) completed symptom-limited incremental cycle exercise tests under two randomized conditions: unrestricted control and CWS to reduce vital capacity (VC) by 21.6 ± 0.5%. Compared with control, exercise with CWS was associated with 1) an exaggerated EMGdi and PTPdi response; 2) no change in the relationship between EMGdi and each of tidal volume (expressed as a percentage of VC), inspiratory reserve volume, and PTPdi, thus indicating relative preservation of neuromechanical coupling; 3) increased sensory intensity and unpleasantness ratings of dyspnea; and 4) no change in the relationship between increasing EMGdi and each of the intensity and unpleasantness of dyspnea. In conclusion, the increased intensity and unpleasantness of dyspnea during exercise with CWS could not be readily explained by increased neuromechanical uncoupling but likely reflected the awareness of increased neural respiratory drive (EMGdi) needed to achieve any given VE during exercise in the setting of “abnormal” restrictive constraints on tidal volume expansion. PMID:24356524

Hypoxemia, hypercapnia, and breathing pattern in patients with chronic obstructive pulmonary disease.

PubMed

Parot, S; Miara, B; Milic-Emili, J; Gautier, H

1982-11-01

The results of lung function tests (total and functional residual capacities, residual volume/total lung capacity ratio, forced expiratory volume in one second) breathing patterns and arterial PO2 and PCO2 were studied in 651 ambulatory male patients with chronic obstructive pulmonary disease, functionally and clinically stable. Function tests were only loosely correlated with gas tensions: abnormalities in mechanics and in gas exchange are not necessarily related. In patients matched for the degree of obstruction, the breathing pattern depended upon both PaO2 and PaCO2. Isolated hypoxemia was accompanied by increased respiratory frequency without any variation in tidal volume: this suggests that the chemoreceptive systems still responded to changes in PaO2. Isolated hypercapnia was accompanied by a decrease in tidal volume and an increase in respiratory frequency. Consequently, the dead space/tidal volume ratio increased, leading to a drop in alveolar ventilation and to CO2 retention.

Evaluation of Fractional Regional Ventilation Using 4D-CT and Effects of Breathing Maneuvers on Ventilation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mistry, Nilesh N., E-mail: nmistry@som.umaryland.edu; Diwanji, Tejan; Shi, Xiutao

2013-11-15

Purpose: Current implementations of methods based on Hounsfield units to evaluate regional lung ventilation do not directly incorporate tissue-based mass changes that occur over the respiratory cycle. To overcome this, we developed a 4-dimensional computed tomography (4D-CT)-based technique to evaluate fractional regional ventilation (FRV) that uses an individualized ratio of tidal volume to end-expiratory lung volume for each voxel. We further evaluated the effect of different breathing maneuvers on regional ventilation. The results from this work will help elucidate the relationship between global and regional lung function. Methods and Materials: Eight patients underwent 3 sets of 4D-CT scans during 1more » session using free-breathing, audiovisual guidance, and active breathing control. FRV was estimated using a density-based algorithm with mass correction. Internal validation between global and regional ventilation was performed by use of the imaging data collected during the use of active breathing control. The impact of breathing maneuvers on FRV was evaluated comparing the tidal volume from 3 breathing methods. Results: Internal validation through comparison between the global and regional changes in ventilation revealed a strong linear correlation (slope of 1.01, R{sup 2} of 0.97) between the measured global lung volume and the regional lung volume calculated by use of the “mass corrected” FRV. A linear relationship was established between the tidal volume measured with the automated breathing control system and FRV based on 4D-CT imaging. Consistently larger breathing volumes were observed when coached breathing techniques were used. Conclusions: The technique presented improves density-based evaluation of lung ventilation and establishes a link between global and regional lung ventilation volumes. Furthermore, the results obtained are comparable with those of other techniques of functional evaluation such as spirometry and hyperpolarized-gas magnetic resonance imaging. These results were demonstrated on retrospective analysis of patient data, and further research using prospective data is under way to validate this technique against established clinical tests.« less

End-expiratory lung volume and ventilation distribution with different continuous positive airway pressure systems in volunteers.

PubMed

Andersson, B; Lundin, S; Lindgren, S; Stenqvist, O; Odenstedt Hergès, H

2011-02-01

Continuous positive airway pressure (CPAP) has been shown to improve oxygenation and a number of different CPAP systems are available. The aim of this study was to assess lung volume and ventilation distribution using three different CPAP techniques. A high-flow CPAP system (HF-CPAP), an ejector-driven system (E-CPAP) and CPAP using a Servo 300 ventilator (V-CPAP) were randomly applied at 0, 5 and 10 cmH₂O in 14 volunteers. End-expiratory lung volume (EELV) was measured by N₂ dilution at baseline; changes in EELV and tidal volume distribution were assessed by electric impedance tomography. Higher end-expiratory and mean airway pressures were found using the E-CPAP vs. the HF-CPAP and the V-CPAP system (P<0.01). EELV increased markedly from baseline, 0 cmH₂O, with increased CPAP levels: 1110±380, 1620±520 and 1130±350 ml for HF-, E- and V-CPAP, respectively, at 10 cmH₂O. A larger fraction of the increase in EELV occurred for all systems in ventral compared with dorsal regions (P<0.01). In contrast, tidal ventilation was increasingly directed toward dorsal regions with increasing CPAP levels (P<0.01). The increase in EELV as well as the tidal volume redistribution were more pronounced with the E-CPAP system as compared with both the HF-CPAP and the V-CPAP systems (P<0.05) at 10 cmH₂O. EELV increased more in ventral regions with increasing CPAP levels, independent of systems, leading to a redistribution of tidal ventilation toward dorsal regions. Different CPAP systems resulted in different airway pressure profiles, which may result in different lung volume expansion and tidal volume distribution. © 2010 The Authors. Journal compilation © 2010 The Acta Anaesthesiologica Scandinavica Foundation.

Accuracy of tidal breathing measurement of FloRight compared to an ultrasonic flowmeter in infants.

PubMed

Petrus, Nicole C M; Thamrin, Cindy; Fuchs, Oliver; Frey, Urs

2015-04-01

Monitoring breathing pattern is especially relevant in infants with lung disease. Recently, a vest-based inductive plethysmograph system (FloRight®) has been developed for tidal breathing measurement in infants. We investigated the accuracy of tidal breathing flow volume loop (TBFVL) measurements in healthy term-born infants and infants with lung disease by the vest-based system in comparison to an ultrasonic flowmeter (USFM) with a face mask. We also investigated whether the system discriminates between healthy infants and those with lung disease. Floright® measures changes in thoracoabdominal volume during tidal breathing through magnetic field changes generated by current-carrying conductor coils in an elastic vest. Simultaneous TBFVL measurements by the vest-based system and the USFM were performed at 44 weeks corrected postmenstrual age during quiet unsedated sleep. TBFVL parameters derived by both techniques and within both groups were compared. We included 19 healthy infants and 18 infants with lung disease. Tidal volume per body weight derived by the vest-based system was significantly lower with a mean difference (95% CI) of -1.33 ml/kg (-1.73; -0.92), P < 0.001. Respiratory rate and ratio of time to peak tidal expiratory flow over total expiratory time (tPTEF/tE) did not differ between the two techniques. Both systems were able to discriminate between healthy infants and those with lung disease using tPTEF/tE. FloRight® accurately measures time indices and may discriminate between healthy infants and those with lung disease, but demonstrates differences in tidal volume measurements. It may be better suited to monitor breathing pattern than for TBFVL measurements. © 2014 Wiley Periodicals, Inc.

Ventilation practices in the neonatal intensive care unit: a cross-sectional study.

PubMed

van Kaam, Anton H; Rimensberger, Peter C; Borensztajn, Dorine; De Jaegere, Anne P

2010-11-01

To assess current ventilation practices in newborn infants. We conducted a 2-point cross-sectional study in 173 European neonatal intensive care units, including 535 infants (mean gestational age 28 weeks and birth weight 1024 g). Patient characteristics, ventilator settings, and measurements were collected bedside from endotracheally ventilated infants. A total of 457 (85%) patients were conventionally ventilated. Time cycled pressure-limited ventilation was used in 59% of these patients, most often combined with synchronized intermittent mandatory ventilation (51%). Newer conventional ventilation modes like volume targeted and pressure support ventilation were used in, respectively, 9% and 7% of the patients. The mean tidal volume, measured in 84% of the conventionally ventilated patients, was 5.7 ± 2.3 ml/kg. The mean positive end-expiratory pressure was 4.5 ± 1.1 cmH(2)O and rarely exceeded 7 cmH(2)O. Time cycled pressure-limited ventilation is the most commonly used mode in neonatal ventilation. Tidal volumes are usually targeted between 4 to 7 mL/kg and positive end-expiratory pressure between 4 to 6 cmH(2)O. Newer ventilation modes are only used in a minority of patients. Copyright © 2010 Mosby, Inc. All rights reserved.

Numerical analysis of tidal dynamics in the region around Gulf of Mannar and Palk Strait

NASA Astrophysics Data System (ADS)

Scaria, Sajumon; Murali, K.; Shanmugam, P.

2015-04-01

A 3D hydrodynamic model is presented to study tidal dynamics along the Indian coast and adjoining marginal seas as well as to investigate the volume transport of water across a tidal channel between the Gulf of Mannar and Palk Strait areas. The numerical model is validated in three stages, and its performance is further assessed by comparing the derived amplitudes of the semidiurnal and diurnal constituents with those of FES 2004 model. The accuracy of the model is ensured by comparing the tidal elevations at selected locations with the observed data. As a next level of validation, the elevations are subjected to the harmonic analysis in order to derive the harmonic constants. The numerical analysis of tidal energetics in the Palk Strait and Gulf of Mannar leads to conclude that M2 constituent undergoes more dissipation and the area-integrated mean dissipation rate of M2 and K1 is 3.22 and 0.25 GW. The temporal and spatial distributions of the sectional daily water volume transport are also analysed for the channel connecting the Palk Strait and the Gulf of Mannar. The localized geographical factors near the Adam's bridge area strongly influence the tidal flow, and the water volume transport shows seasonal variations.

Synthesis study of an erosion hot spot, Ocean Beach, California

USGS Publications Warehouse

Barnard, Patrick L.; Hansen, Jeff E.; Erikson, Li H.

2012-01-01

A synthesis of multiple coastal morphodynamic research efforts is presented to identify the processes responsible for persistent erosion along a 1-km segment of 7-km-long Ocean Beach in San Francisco, California. The beach is situated adjacent to a major tidal inlet and in the shadow of the ebb-tidal delta at the mouth of San Francisco Bay. Ocean Beach is exposed to a high-energy wave climate and significant alongshore variability in forcing introduced by varying nearshore bathymetry, tidal forcing, and beach morphology (e.g., beach variably backed by seawall, dunes, and bluffs). In addition, significant regional anthropogenic factors have influenced sediment supply and tidal current strength. A variety of techniques were employed to investigate the erosion at Ocean Beach, including historical shoreline and bathymetric analysis, monthly beach topographic surveys, nearshore and regional bathymetric surveys, beach and nearshore grain size analysis, two surf-zone hydrodynamic experiments, four sets of nearshore wave and current experiments, and several numerical modeling approaches. Here, we synthesize the results of 7 years of data collection to lay out the causes of persistent erosion, demonstrating the effectiveness of integrating an array of data sets covering a huge range of spatial scales. The key findings are as follows: anthropogenic influences have reduced sediment supply from San Francisco Bay, leading to pervasive contraction (i.e., both volume and area loss) of the ebb-tidal delta, which in turn reduced the regional grain size and modified wave focusing patterns along Ocean Beach, altering nearshore circulation and sediment transport patterns. In addition, scour associated with an exposed sewage outfall pipe causes a local depression in wave heights, significantly modifying nearshore circulation patterns that have been shown through modeling to be key drivers of persistent erosion in that area.

Determination of regional lung air volume distribution at mid-tidal breathing from computed tomography: a retrospective study of normal variability and reproducibility

PubMed Central

2014-01-01

Background Determination of regional lung air volume has several clinical applications. This study investigates the use of mid-tidal breathing CT scans to provide regional lung volume data. Methods Low resolution CT scans of the thorax were obtained during tidal breathing in 11 healthy control male subjects, each on two separate occasions. A 3D map of air volume was derived, and total lung volume calculated. The regional distribution of air volume from centre to periphery of the lung was analysed using a radial transform and also using one dimensional profiles in three orthogonal directions. Results The total air volumes for the right and left lungs were 1035 +/− 280 ml and 864 +/− 315 ml, respectively (mean and SD). The corresponding fractional air volume concentrations (FAVC) were 0.680 +/− 0.044 and 0.658 +/− 0.062. All differences between the right and left lung were highly significant (p < 0.0001). The coefficients of variation of repeated measurement of right and left lung air volumes and FAVC were 6.5% and 6.9% and 2.5% and 3.6%, respectively. FAVC correlated significantly with lung space volume (r = 0.78) (p < 0.005). FAVC increased from the centre towards the periphery of the lung. Central to peripheral ratios were significantly higher for the right (0.100 +/− 0.007 SD) than the left (0.089 +/− 0.013 SD) (p < 0.0001). Conclusion A technique for measuring the distribution of air volume in the lung at mid-tidal breathing is described. Mean values and reproducibility are described for healthy male control subjects. Fractional air volume concentration is shown to increase with lung size. PMID:25063729

A flow-simulation model of the tidal Potomac River

USGS Publications Warehouse

Schaffranek, Raymond W.

1987-01-01

A one-dimensional model capable of simulating flow in a network of interconnected channels has been applied to the tidal Potomac River including its major tributaries and embayments between Washington, D.C., and Indian Head, Md. The model can be used to compute water-surface elevations and flow discharges at any of 66 predetermined locations or at any alternative river cross sections definable within the network of channels. In addition, the model can be used to provide tidal-interchange flow volumes and to evaluate tidal excursions and the flushing properties of the riverine system. Comparisons of model-computed results with measured watersurface elevations and discharges demonstrate the validity and accuracy of the model. Tidal-cycle flow volumes computed by the calibrated model have been verified to be within an accuracy of ? 10 percent. Quantitative characteristics of the hydrodynamics of the tidal river are identified and discussed. The comprehensive flow data provided by the model can be used to better understand the geochemical, biological, and other processes affecting the river's water quality.

Numerical investigation of flow motion and performance of a horizontal axis tidal turbine subjected to a steady current

NASA Astrophysics Data System (ADS)

Li, Lin-juan; Zheng, Jin-hai; Peng, Yu-xuan; Zhang, Ji-sheng; Wu, Xiu-guang

2015-04-01

Horizontal axis tidal turbines have attracted more and more attentions nowadays, because of their convenience and low expense in construction and high efficiency in extracting tidal energy. The present study numerically investigates the flow motion and performance of a horizontal axis tidal turbine with a supporting vertical cylinder under steady current. In the numerical model, the continuous equation and incompressible Reynolds-averaged Navier-Stokes equations are solved, and the volume of fluid method is employed to track free surface motion. The RNG k- ɛ model is adopted to calculate turbulence transport while the fractional area/volume obstacle representation method is used to describe turbine characteristics and movement. The effects of installation elevation of tidal turbine and inlet velocity on the water elevation, and current velocity, rotating speed and resultant force on turbine are discussed. Based on the comparison of the numerical results, a better understanding of flow structure around horizontal axis tidal turbine and turbine performance is achieved.

Ventilatory protective strategies during thoracic surgery: effects of alveolar recruitment maneuver and low-tidal volume ventilation on lung density distribution.

PubMed

Kozian, Alf; Schilling, Thomas; Schütze, Hartmut; Senturk, Mert; Hachenberg, Thomas; Hedenstierna, Göran

2011-05-01

The increased tidal volume (V(T)) applied to the ventilated lung during one-lung ventilation (OLV) enhances cyclic alveolar recruitment and mechanical stress. It is unknown whether alveolar recruitment maneuvers (ARMs) and reduced V(T) may influence tidal recruitment and lung density. Therefore, the effects of ARM and OLV with different V(T) on pulmonary gas/tissue distribution are examined. Eight anesthetized piglets were mechanically ventilated (V(T) = 10 ml/kg). A defined ARM was applied to the whole lung (40 cm H(2)O for 10 s). Spiral computed tomographic lung scans were acquired before and after ARM. Thereafter, the lungs were separated with an endobronchial blocker. The pigs were randomized to receive OLV in the dependent lung with a V(T) of either 5 or 10 ml/kg. Computed tomography was repeated during and after OLV. The voxels were categorized by density intervals (i.e., atelectasis, poorly aerated, normally aerated, or overaerated). Tidal recruitment was defined as the addition of gas to collapsed lung regions. The dependent lung contained atelectatic (56 ± 10 ml), poorly aerated (183 ± 10 ml), and normally aerated (187 ± 29 ml) regions before ARM. After ARM, lung volume and aeration increased (426 ± 35 vs. 526 ± 69 ml). Respiratory compliance enhanced, and tidal recruitment decreased (95% vs. 79% of the whole end-expiratory lung volume). OLV with 10 ml/kg further increased aeration (atelectasis, 15 ± 2 ml; poorly aerated, 94 ± 24 ml; normally aerated, 580 ± 98 ml) and tidal recruitment (81% of the dependent lung). OLV with 5 ml/kg did not affect tidal recruitment or lung density distribution. (Data are given as mean ± SD.) The ARM improves aeration and respiratory mechanics. In contrast to OLV with high V(T), OLV with reduced V(T) does not reinforce tidal recruitment, indicating decreased mechanical stress.

Particle size concentration distribution and influences on exhaled breath particles in mechanically ventilated patients.

PubMed

Wan, Gwo-Hwa; Wu, Chieh-Liang; Chen, Yi-Fang; Huang, Sheng-Hsiu; Wang, Yu-Ling; Chen, Chun-Wan

2014-01-01

Humans produce exhaled breath particles (EBPs) during various breath activities, such as normal breathing, coughing, talking, and sneezing. Airborne transmission risk exists when EBPs have attached pathogens. Until recently, few investigations had evaluated the size and concentration distributions of EBPs from mechanically ventilated patients with different ventilation mode settings. This study thus broke new ground by not only evaluating the size concentration distributions of EBPs in mechanically ventilated patients, but also investigating the relationship between EBP level and positive expiratory end airway pressure (PEEP), tidal volume, and pneumonia. This investigation recruited mechanically ventilated patients, with and without pneumonia, aged 20 years old and above, from the respiratory intensive care unit of a medical center. Concentration distributions of EBPs from mechanically ventilated patients were analyzed with an optical particle analyzer. This study finds that EBP concentrations from mechanically ventilated patients during normal breathing were in the range 0.47-2,554.04 particles/breath (0.001-4.644 particles/mL). EBP concentrations did not differ significantly between the volume control and pressure control modes of the ventilation settings in the mechanically ventilated patients. The patient EBPs were sized below 5 µm, and 80% of them ranged from 0.3 to 1.0 µm. The EBPs concentrations in patients with high PEEP (> 5 cmH₂O) clearly exceeded those in patients with low PEEP (≤ 5 cmH₂O). Additionally, a significant negative association existed between pneumonia duration and EBPs concentration. However, tidal volume was not related to EBPs concentration.

System Design Verification for Closed Loop Control of Oxygenation With Concentrator Integration.

PubMed

Gangidine, Matthew M; Blakeman, Thomas C; Branson, Richard D; Johannigman, Jay A

2016-05-01

Addition of an oxygen concentrator into a control loop furthers previous work in autonomous control of oxygenation. Software integrates concentrator and ventilator function from a single control point, ensuring maximum efficiency by placing a pulse of oxygen at the beginning of the breath. We sought to verify this system. In a test lung, fraction of inspired oxygen (FIO2) levels and additional data were monitored. Tests were run across a range of clinically relevant ventilator settings in volume control mode, for both continuous flow and pulse dose flow oxygenation. Results showed the oxygen concentrator could maintain maximum pulse output (192 mL) up to 16 breaths per minute. Functionality was verified across ranges of tidal volumes and respiratory rates, with and without positive end-expiratory pressure, in continuous flow and pulse dose modes. For a representative test at respiratory rate 16 breaths per minute, tidal volume 550 mL, without positive end-expiratory pressure, pulse dose oxygenation delivered peak FIO2 of 76.83 ± 1.41%, and continuous flow 47.81 ± 0.08%; pulse dose flow provided a higher FIO2 at all tested setting combinations compared to continuous flow (p < 0.001). These tests verify a system that provides closed loop control of oxygenation while integrating time-coordinated pulse-doses from an oxygen concentrator. This allows the most efficient use of resources in austere environments. Reprint & Copyright © 2016 Association of Military Surgeons of the U.S.

Effects of positive end-expiratory pressure and recruitment maneuvers in a ventilator-induced injury mouse model

PubMed Central

Franzi, Lisa M.; Linderholm, Angela L.; Last, Jerold A.; Adams, Jason Y.; Harper, Richart W.

2017-01-01

Background Positive-pressure mechanical ventilation is an essential therapeutic intervention, yet it causes the clinical syndrome known as ventilator-induced lung injury. Various lung protective mechanical ventilation strategies have attempted to reduce or prevent ventilator-induced lung injury but few modalities have proven effective. A model that isolates the contribution of mechanical ventilation on the development of acute lung injury is needed to better understand biologic mechanisms that lead to ventilator-induced lung injury. Objectives To evaluate the effects of positive end-expiratory pressure and recruitment maneuvers in reducing lung injury in a ventilator-induced lung injury murine model in short- and longer-term ventilation. Methods 5–12 week-old female BALB/c mice (n = 85) were anesthetized, placed on mechanical ventilation for either 2 hrs or 4 hrs with either low tidal volume (8 ml/kg) or high tidal volume (15 ml/kg) with or without positive end-expiratory pressure and recruitment maneuvers. Results Alteration of the alveolar-capillary barrier was noted at 2 hrs of high tidal volume ventilation. Standardized histology scores, influx of bronchoalveolar lavage albumin, proinflammatory cytokines, and absolute neutrophils were significantly higher in the high-tidal volume ventilation group at 4 hours of ventilation. Application of positive end-expiratory pressure resulted in significantly decreased standardized histology scores and bronchoalveolar absolute neutrophil counts at low- and high-tidal volume ventilation, respectively. Recruitment maneuvers were essential to maintain pulmonary compliance at both 2 and 4 hrs of ventilation. Conclusions Signs of ventilator-induced lung injury are evident soon after high tidal volume ventilation (as early as 2 hours) and lung injury worsens with longer-term ventilation (4 hrs). Application of positive end-expiratory pressure and recruitment maneuvers are protective against worsening VILI across all time points. Dynamic compliance can be used guide the frequency of recruitment maneuvers to help ameloriate ventilator-induced lung injury. PMID:29112971

Novel analysis of 4DCT imaging quantifies progressive increases in anatomic dead space during mechanical ventilation in mice.

PubMed

Kim, Elizabeth H; Preissner, Melissa; Carnibella, Richard P; Samarage, Chaminda R; Bennett, Ellen; Diniz, Marcio A; Fouras, Andreas; Zosky, Graeme R; Jones, Heather D

2017-09-01

Increased dead space is an important prognostic marker in early acute respiratory distress syndrome (ARDS) that correlates with mortality. The cause of increased dead space in ARDS has largely been attributed to increased alveolar dead space due to ventilation/perfusion mismatching and shunt. We sought to determine whether anatomic dead space also increases in response to mechanical ventilation. Mice received intratracheal lipopolysaccharide (LPS) or saline and mechanical ventilation (MV). Four-dimensional computed tomography (4DCT) scans were performed at onset of MV and after 5 h of MV. Detailed measurements of airway volumes and lung tidal volumes were performed using image analysis software. The forced oscillation technique was used to obtain measures of airway resistance, tissue damping, and tissue elastance. The ratio of airway volumes to total tidal volume increased significantly in response to 5 h of mechanical ventilation, regardless of LPS exposure, and airways demonstrated significant variation in volumes over the respiratory cycle. These findings were associated with an increase in tissue elastance (decreased lung compliance) but without changes in tidal volumes. Airway volumes increased over time with exposure to mechanical ventilation without a concomitant increase in tidal volumes. These findings suggest that anatomic dead space fraction increases progressively with exposure to positive pressure ventilation and may represent a pathological process. NEW & NOTEWORTHY We demonstrate that anatomic dead space ventilation increases significantly over time in mice in response to mechanical ventilation. The novel functional lung-imaging techniques applied here yield sensitive measures of airway volumes that may have wide applications. Copyright © 2017 the American Physiological Society.

Effect of different ventilatory strategies on local and systemic cytokine production in intact swine lungs in vivo.

PubMed

Myrianthefs, P; Boutzouka, E; Venetsanou, K; Papalois, A; Kouloukousa, M; Kittas, C; Baltopoulos, G

2006-05-01

The purpose of the study was to investigate the effect of different ventilatory strategies on local and systemic cytokine production in swine with intact lungs in vivo after 4 h of mechanical ventilation. Twenty-five swine were anesthetized and then randomized into five groups (n = 5): (1) low tidal volume zero PEEP (LVZP); (2) medium tidal volume zero PEEP (MVZP); (3) high tidal volume zero PEEP (HVZP); (4) low tidal volume PEEP (LVP); (4) high tidal volume PEEP (HVP). Respiratory rate was adjusted to maintain normocapnia and fraction of inspired oxygen (FiO2) was 1.0. TNF-alpha and IL-10 were measured in BALF and serum at baseline, 2 h, and 4 h of MV. One animal in LVZP (2 h) and two in HVP (3 h) group died before the end of the experiment. TNF-alpha level in BALF was significantly higher in LVZP and LVP at 4 h compared to baseline and the other groups. IL-10 level in BALF was significantly higher in LVP at 4h compared to baseline and the other groups. There was a statistically significant increase in serum TNF-alpha levels at 4 h in LVP group compared to baseline and the other groups at 4 h. There was statistically significant increase in serum IL-10 levels in HVZP and LVP groups at 2 and 4 h which was significantly higher compared to the other groups at 4 h. Our results show that a) low volume MV may induce local and systemic pro- and anti-inflammatory cytokine increase b) in the presence of pro-inflammatory cytokine response there is also an anti-inflammatory response in the same compartment (lungs, circulation). c) There maybe loss of alveolar-to-systemic cytokine compartmentalization.

An open-loop controlled active lung simulator for preterm infants.

PubMed

Cecchini, Stefano; Schena, Emiliano; Silvestri, Sergio

2011-01-01

We describe the underlying theory, design and experimental evaluation of an electromechanical analogue infant lung to simulate spontaneous breathing patterns of preterm infants. The aim of this work is to test the possibility to obtain breathing patterns of preterm infants by taking into consideration the air compressibility. Respiratory volume function represents the actuation pattern, and pulmonary pressure and flow-rate waveforms are mathematically obtained through the application of the perfect gas and adiabatic laws. The mathematical model reduces the simulation interval into a step shorter than 1 ms, allowing to consider an entire respiratory act as composed of a large number of almost instantaneous adiabatic transformations. The device consists of a spherical chamber where the air is compressed by four cylinder-pistons, moved by stepper motors, and flows through a fluid-dynamic resistance, which also works as flow-rate sensor. Specifically designed software generates the actuators motion, based on the desired ventilation parameters, without controlling the gas pneumatic parameters with a closed-loop. The system is able to simulate tidal volumes from 3 to 8 ml, breathing frequencies from 60 to 120 bpm and functional residual capacities from 25 to 80 ml. The simulated waveforms appear very close to the measured ones. Percentage differences on the tidal volume waveform vary from 7% for the tidal volume of 3 ml, down to 2.2-3.5% for tidal volumes in the range of 4-7 ml, and 1.3% for the tidal volume equal to 8 ml in the whole breathing frequency and functional residual capacity ranges. The open-loop electromechanical simulator shows that gas compressibility can be theoretically assessed in the typical pneumatic variable range of preterm infant respiratory mechanics. Copyright © 2010 IPEM. Published by Elsevier Ltd. All rights reserved.

Tidal inlet response to sediment infilling of the associated bay and possible implications of human activities: the Marennes-Oléron Bay and the Maumusson Inlet, France

NASA Astrophysics Data System (ADS)

Bertin, Xavier; Chaumillon, Eric; Sottolichio, Aldo; Pedreros, Rodrigo

2005-06-01

Tidal inlet characteristics are controlled by wave energy, tidal range, tidal prism, sediment supply and direction and rates of sand delivered to the inlet. This paper deals with the relations between inlet and lagoon evolutions, linked by the tidal prism. Our study is focused on the Maumusson Inlet and the Marennes-Oléron Bay (first oyster farming area in Europe), located on the western coast of France. The tidal range (2-6 m) and wave climate (mean height: 1.5 m) place this tidal inlet system in the mixed energy (tide, waves), tide-dominated category. The availability of high-resolution bathymetric data since 1824 permits to characterise and quantify accurately morphological changes of both the inlet and the tidal bay. Since 1824, sediment filling of the tidal bay has led to a 20% decrease in its water volume, and a 35% reduction of the inlet throat section. Furthermore, the bay is subjected to a very high anthropic pressure, mainly related to oyster farming. Thus, both natural and human-related processes seem relevant to explain high sedimentation rates. Current measurements, hydrodynamic modelling and cross-sectional area of the inlet throat are used in order to quantify tidal prism changes since 1824. Both flood and ebb tidal prism decreased by 35%. Decrease in the Marennes-Oléron Bay water volume is inferred to be responsible for a part of tidal prism decrease at the inlet. Tidal prisms decrease may also be explained by an increase in frictional resistance to tidal wave propagation, due to a general shoaling and oyster farms in the bay. A conceptual model is proposed, taking into account natural and human-related sedimentation processes, and explaining tidal inlet response to tidal bay evolutions.

FLOW-i ventilator performance in the presence of a circle system leak.

PubMed

Lucangelo, Umberto; Ajčević, Miloš; Accardo, Agostino; Borelli, Massimo; Peratoner, Alberto; Comuzzi, Lucia; Zin, Walter A

2017-04-01

Recently, the FLOW-i anaesthesia ventilator was developed based on the SERVO-i intensive care ventilator. The aim of this study was to test the FLOW-i's tidal volume delivery in the presence of a leak in the breathing circuit. We ventilated a test lung model in volume-, pressure-, and pressure-regulated volume-controlled modes (VC, PC, and PRVC, respectively) with a FLOW-i. First, the circuit remained airtight and the ventilator was tested with fresh gas flows of 6, 1, and 0.3 L/min in VC, PC, and PRVC modes and facing 4 combinations of different resistive and elastic loads. Second, a fixed leak in the breathing circuit was introduced and the measurements repeated. In the airtight system, FLOW-i maintained tidal volume (VT) and circuit pressure at approximately the set values, independently of respiratory mode, load, or fresh gas flow. In the leaking circuit, set VT = 500 mL, FLOW-i delivered higher VTs in PC (about 460 mL) than in VC and PRVC, where VTs were substantially less than 500 mL. Interestingly, VT did not differ appreciably from 6 to 0.3 L/min of fresh air flow among the 3 ventilatory modes. In the absence of leakage, peak inspiratory pressures were similar, while they were 35-45 % smaller in PRVC and VC than in PC mode in the presence of leaks. In conclusion, FLOW-i maintained VT (down to fresh gas flows of 0.3 L/min) to 90 % of its preset value in PC mode, which was 4-5 times greater than in VC or PRVC modes.

Spirometry and volumetric capnography in lung function assessment of obese and normal-weight individuals without asthma.

PubMed

Ferreira, Mariana S; Mendes, Roberto T; Marson, Fernando A L; Zambon, Mariana P; Antonio, Maria A R G M; Paschoal, Ilma A; Toro, Adyléia A D C; Severino, Silvana D; Ribeiro, Maria A G O; Ribeiro, José D

To analyze and compare lung function of obese and healthy, normal-weight children and adolescents, without asthma, through spirometry and volumetric capnography. Cross-sectional study including 77 subjects (38 obese) aged 5-17 years. All subjects underwent spirometry and volumetric capnography. The evaluations were repeated in obese subjects after the use of a bronchodilator. At the spirometry assessment, obese individuals, when compared with the control group, showed lower values of forced expiratory volume in the first second by forced vital capacity (FEV 1 /FVC) and expiratory flows at 75% and between 25 and 75% of the FVC (p<0.05). Volumetric capnography showed that obese individuals had a higher volume of produced carbon dioxide and alveolar tidal volume (p<0.05). Additionally, the associations between dead space volume and tidal volume, as well as phase-3 slope normalized by tidal volume, were lower in healthy subjects (p<0.05). These data suggest that obesity does not alter ventilation homogeneity, but flow homogeneity. After subdividing the groups by age, a greater difference in lung function was observed in obese and healthy individuals aged >11 years (p<0.05). Even without the diagnosis of asthma by clinical criteria and without response to bronchodilator use, obese individuals showed lower FEV 1 /FVC values and forced expiratory flow, indicating the presence of an obstructive process. Volumetric capnography showed that obese individuals had higher alveolar tidal volume, with no alterations in ventilation homogeneity, suggesting flow alterations, without affecting lung volumes. Copyright © 2017 Sociedade Brasileira de Pediatria. Published by Elsevier Editora Ltda. All rights reserved.

pRotective vEntilation with veno-venouS lung assisT in respiratory failure: A protocol for a multicentre randomised controlled trial of extracorporeal carbon dioxide removal in patients with acute hypoxaemic respiratory failure.

PubMed

McNamee, J J; Gillies, M A; Barrett, N A; Agus, A M; Beale, R; Bentley, A; Bodenham, A; Brett, S J; Brodie, D; Finney, S J; Gordon, A J; Griffiths, M; Harrison, D; Jackson, C; McDowell, C; McNally, C; Perkins, G D; Tunnicliffe, W; Vuylsteke, A; Walsh, T S; Wise, M P; Young, D; McAuley, D F

2017-05-01

One of the few interventions to demonstrate improved outcomes for acute hypoxaemic respiratory failure is reducing tidal volumes when using mechanical ventilation, often termed lung protective ventilation. Veno-venous extracorporeal carbon dioxide removal (vv-ECCO 2 R) can facilitate reducing tidal volumes. pRotective vEntilation with veno-venouS lung assisT (REST) is a randomised, allocation concealed, controlled, open, multicentre pragmatic trial to determine the clinical and cost-effectiveness of lower tidal volume mechanical ventilation facilitated by vv-ECCO 2 R in patients with acute hypoxaemic respiratory failure. Patients requiring intubation and mechanical ventilation for acute hypoxaemic respiratory failure will be randomly allocated to receive either vv-ECCO 2 R and lower tidal volume mechanical ventilation or standard care with stratification by recruitment centre. There is a need for a large randomised controlled trial to establish whether vv-ECCO 2 R in acute hypoxaemic respiratory failure can allow the use of a more protective lung ventilation strategy and is associated with improved patient outcomes.

Are tidal volume measurements in neonatal pressure-controlled ventilation accurate?

PubMed

Chow, Lily C; Vanderhal, Andre; Raber, Jorge; Sola, Augusto

2002-09-01

Bedside pulmonary mechanics monitors (PMM) have become useful in ventilatory management in neonates. These monitors are used more frequently due to recent improvements in data-processing capabilities. PMM devices are often part of the ventilator or are separate units. The accuracy and reliability of these systems have not been carefully evaluated. We compared a single ventilatory parameter, tidal volume (V(t)), as measured by several systems. We looked at two freestanding PMMs: the Ventrak Respiratory Monitoring System (Novametrix, Wallingford, CT) and the Bicore CP-100 Neonatal Pulmonary Monitor (Allied Health Care Products, Riverside, CA), and three ventilators with built-in PMM: the VIP Bird Ventilator (Bird Products Corp., Palm Springs, CA), Siemens Servo 300A (Siemens-Elema AB, Solna, Sweden), and Drager Babylog 8000 (Drager, Inc., Chantilly, VA). A calibrated syringe (Hans Rudolph, Inc., Kansas City, MO) was used to deliver tidal volumes of 4, 10, and 20 mL to each ventilator system coupled with a freestanding PMM. After achieving steady state, six consecutive V(t) readings were taken simultaneously from the freestanding PMM and each ventilator. In a second portion of the bench study, we used pressure-control ventilation and measured exhaled tidal volume (V(te)) while ventilating a Bear Test Lung with the same three ventilators. We adjusted peak inspiratory pressure (PIP) under controlled conditions to achieve the three different targeted tidal volumes on the paired freestanding PMM. Again, six V(te) measurements were recorded for each tidal volume. Means and standard deviations were calculated.The percentage difference in measurement of V(t) delivered by calibrated syringe varied greatly, with the greatest discrepancy seen in the smallest tidal volumes, by up to 28%. In pressure control mode, V(te) as measured by the Siemens was significantly overestimated by 20-95%, with the biggest discrepancy at the smallest V(te), particularly when paired with the Bicore PMM. V(te), as measured by the VIP Bird and Drager paired with the Ventrak PMM, had a tendency to underestimate V(t) by up to 25% at the smallest V(te). However, when paired with the Bicore PMM, these same two ventilators read over target by up to 18%. Under controlled laboratory conditions, we demonstrated that true delivered V(te), as measured by the three ventilators and two freestanding PMM, differed markedly. In general, decreasing dynamic compliance of the tubing was not associated with greater inaccuracy in V(te) measurements. Copyright 2002 Wiley-Liss, Inc.

Time-Resolved Quantitative Analysis of the Diaphragms During Tidal Breathing in a Standing Position Using Dynamic Chest Radiography with a Flat Panel Detector System ("Dynamic X-Ray Phrenicography"): Initial Experience in 172 Volunteers.

PubMed

Yamada, Yoshitake; Ueyama, Masako; Abe, Takehiko; Araki, Tetsuro; Abe, Takayuki; Nishino, Mizuki; Jinzaki, Masahiro; Hatabu, Hiroto; Kudoh, Shoji

2017-04-01

Diaphragmatic motion in a standing position during tidal breathing remains unclear. The purpose of this observational study was to evaluate diaphragmatic motion during tidal breathing in a standing position in a health screening center cohort using dynamic chest radiography in association with participants' demographic characteristics. One hundred seventy-two subjects (103 men; aged 56.3 ± 9.8 years) underwent sequential chest radiographs during tidal breathing using dynamic chest radiography with a flat panel detector system. We evaluated the excursions of and peak motion speeds of the diaphragms. Associations between the excursions and participants' demographics (gender, height, weight, body mass index [BMI], smoking history, tidal volume, vital capacity, and forced expiratory volume) were investigated. The average excursion of the left diaphragm (14.9 ± 4.6 mm, 95% CI 14.2-15.5 mm) was significantly larger than that of the right (11.0 ± 4.0 mm, 95% CI 10.4-11.6 mm) (P <0.001). The peak motion speed of the left diaphragm (inspiratory, 16.6 ± 4.2 mm/s; expiratory, 13.7 ± 4.2 mm/s) was significantly faster than that of the right (inspiratory, 12.4 ± 4.4 mm/s; expiratory, 9.4 ± 3.8 mm/s) (both P <0.001). Both simple and multiple regression models demonstrated that higher BMI and higher tidal volume were associated with increased excursions of the bilateral diaphragm (all P <0.05). The average excursions of the diaphragms are 11.0 mm (right) and 14.9 mm (left) during tidal breathing in a standing position. The diaphragmatic motion of the left is significantly larger and faster than that of the right. Higher BMI and tidal volume are associated with increased excursions of the bilateral diaphragm. Copyright © 2017 The Association of University Radiologists. Published by Elsevier Inc. All rights reserved.

Performance of Portable Ventilators at Altitude

DTIC Science & Technology

2015-03-30

collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT...Deploying ventilators that can maintain a consistent tidal volume (VT) delivery at various altitudes is imperative for lung protection when...performance of mechanical ventilators calibrated for operation at sea level. Deploying ventilators that can maintain a consistent tidal volume (VT) delivery

Ventilatory changes during the use of heat and moisture exchangers in patients submitted to mechanical ventilation with support pressure and adjustments in ventilation parameters to compensate for these possible changes: a self-controlled intervention study in humans.

PubMed

Lucato, Jeanette Janaina Jaber; Cunha, Thiago Marraccini Nogueira da; Reis, Aline Mela Dos; Picanço, Patricia Salerno de Almeida; Barbosa, Renata Cléia Claudino; Liberali, Joyce; Righetti, Renato Fraga

2017-01-01

To evaluate the possible changes in tidal volume, minute volume and respiratory rate caused by the use of a heat and moisture exchanger in patients receiving pressure support mechanical ventilation and to quantify the variation in pressure support required to compensate for the effect caused by the heat and moisture exchanger. Patients under invasive mechanical ventilation in pressure support mode were evaluated using heated humidifiers and heat and moisture exchangers. If the volume found using the heat and moisture exchangers was lower than that found with the heated humidifier, an increase in pressure support was initiated during the use of the heat and moisture exchanger until a pressure support value was obtained that enabled the patient to generate a value close to the initial tidal volume obtained with the heated humidifier. The analysis was performed by means of the paired t test, and incremental values were expressed as percentages of increase required. A total of 26 patients were evaluated. The use of heat and moisture exchangers increased the respiratory rate and reduced the tidal and minute volumes compared with the use of the heated humidifier. Patients required a 38.13% increase in pressure support to maintain previous volumes when using the heat and moisture exchanger. The heat and moisture exchanger changed the tidal and minute volumes and respiratory rate parameters. Pressure support was increased to compensate for these changes.

Ventilatory changes during the use of heat and moisture exchangers in patients submitted to mechanical ventilation with support pressure and adjustments in ventilation parameters to compensate for these possible changes: a self-controlled intervention study in humans

PubMed Central

Lucato, Jeanette Janaina Jaber; da Cunha, Thiago Marraccini Nogueira; dos Reis, Aline Mela; Picanço, Patricia Salerno de Almeida; Barbosa, Renata Cléia Claudino; Liberali, Joyce; Righetti, Renato Fraga

2017-01-01

Objective To evaluate the possible changes in tidal volume, minute volume and respiratory rate caused by the use of a heat and moisture exchanger in patients receiving pressure support mechanical ventilation and to quantify the variation in pressure support required to compensate for the effect caused by the heat and moisture exchanger. Methods Patients under invasive mechanical ventilation in pressure support mode were evaluated using heated humidifiers and heat and moisture exchangers. If the volume found using the heat and moisture exchangers was lower than that found with the heated humidifier, an increase in pressure support was initiated during the use of the heat and moisture exchanger until a pressure support value was obtained that enabled the patient to generate a value close to the initial tidal volume obtained with the heated humidifier. The analysis was performed by means of the paired t test, and incremental values were expressed as percentages of increase required. Results A total of 26 patients were evaluated. The use of heat and moisture exchangers increased the respiratory rate and reduced the tidal and minute volumes compared with the use of the heated humidifier. Patients required a 38.13% increase in pressure support to maintain previous volumes when using the heat and moisture exchanger. Conclusion The heat and moisture exchanger changed the tidal and minute volumes and respiratory rate parameters. Pressure support was increased to compensate for these changes. PMID:28977257

[Bellows or bag? Testing 10 ventilators and some medical history comments].

PubMed

Kötter, K P; Maleck, W H; Altmannsberger, S; Herchet, J; Petroianu, G A

1998-01-01

We compared a new bellows ventilator (Kendall Cardiovent) with two other bellows (Dräger Resutator 63, Tagg Breathsaver) and seven bag or ball ventilators (Aerodyne Hope, Ambu Mark 3, Ambu Silicon, Dräger Resutator 2000, Laerdal Resu, Mercury CPR, Weinmann Combibag). Tidal volumes were measured with two Laerdal Recording Resusci Annies, one lying on the floor, one in a bed. Twelve participants performed mask ventilation with all ten devices on both manikins for two minutes, trying to achieve tidal volumes of between 0.8 and 1.21 as recommended by the AHA. The last ten ventilations each on the graphic strips were analysed for volume. The participants scored handling of the devices on a 6-point scale (1 = very good, 6 = insufficient). The results of the Cardiovent were compared to those of the other devices by rank sum test (percentage of correct ventilations) and sign test (subjective handling). The Cardiovent provided exact ventilation with 95% of ventilations) on the floor and 78% of ventilations in bed in the recommended range. However, the percentage of correct ventilations with the Cardiovent was not significantly different to the other devices except for a lower percentage of correct ventilations with the Combibag in the in bed setting. Concerning subjective handling, the Cardiovent was significantly superior to several ball ventilators.

A Quasi-Experimental, Before-After Trial Examining the Impact of an Emergency Department Mechanical Ventilator Protocol on Clinical Outcomes and Lung-Protective Ventilation in Acute Respiratory Distress Syndrome.

PubMed

Fuller, Brian M; Ferguson, Ian T; Mohr, Nicholas M; Drewry, Anne M; Palmer, Christopher; Wessman, Brian T; Ablordeppey, Enyo; Keeperman, Jacob; Stephens, Robert J; Briscoe, Cristopher C; Kolomiets, Angelina A; Hotchkiss, Richard S; Kollef, Marin H

2017-04-01

To evaluate the impact of an emergency department mechanical ventilation protocol on clinical outcomes and adherence to lung-protective ventilation in patients with acute respiratory distress syndrome. Quasi-experimental, before-after trial. Emergency department and ICUs of an academic center. Mechanically ventilated emergency department patients experiencing acute respiratory distress syndrome while in the emergency department or after admission to the ICU. An emergency department ventilator protocol which targeted variables in need of quality improvement, as identified by prior work: 1) lung-protective tidal volume, 2) appropriate setting of positive end-expiratory pressure, 3) oxygen weaning, and 4) head-of-bed elevation. A total of 229 patients (186 preintervention group, 43 intervention group) were studied. In the emergency department, the intervention was associated with significant changes (p < 0.01 for all) in tidal volume, positive end-expiratory pressure, respiratory rate, oxygen administration, and head-of-bed elevation. There was a reduction in emergency department tidal volume from 8.1 mL/kg predicted body weight (7.0-9.1) to 6.4 mL/kg predicted body weight (6.1-6.7) and an increase in lung-protective ventilation from 11.1% to 61.5%, p value of less than 0.01. The intervention was associated with a reduction in mortality from 54.8% to 39.5% (odds ratio, 0.38; 95% CI, 0.17-0.83; p = 0.02) and a 3.9 day increase in ventilator-free days, p value equals to 0.01. This before-after study of mechanically ventilated patients with acute respiratory distress syndrome demonstrates that implementing a mechanical ventilator protocol in the emergency department is feasible and associated with improved clinical outcomes.

Tidal currents and Kuroshio transport variations in the Tokara Strait estimated from ferryboat ADCP data

NASA Astrophysics Data System (ADS)

Zhu, Xiao-Hua; Nakamura, Hirohiko; Dong, Menghong; Nishina, Ayako; Yamashiro, Toru

2017-03-01

From 2003 to 2011, current surveys, using an acoustic Doppler current profiler (ADCP) mounted on the Ferry Naminoue, were conducted across the Tokara Strait (TkS). Resulting velocity sections (1234) were used to estimate major tidal current constituents in the TkS. The semidiurnal M2 tidal current (maximum amplitude 27 cm s-1) was dominant among all the tidal constituents, and the diurnal K1 tidal current (maximum amplitude 21 cm s-1) was the largest among all the diurnal tidal constituents. Over the section, the ratios, relative to M2, of averaged amplitudes of M2, S2, N2, K2, K1, O1, P1, and Q1 tidal currents were 1.00:0.44:0.21:0.12:0.56:0.33:0.14:0.10. Tidal currents estimated from the ship-mounted ADCP data were in good agreement with those from the mooring ADCP data. Their root-mean-square difference for the M2 tidal current amplitude was 2.0 cm s-1. After removing the tidal currents, the annual-mean of the net volume transport (NVT) through the TkS ± its standard derivation was 23.03 ± 3.31 Sv (Sv = 106 m3 s-1). The maximum (minimum) monthly mean NVT occurred in July (November) with 24.60 (21.47) Sv. NVT values from the ship-mounted ADCP were in good agreement with previous geostrophic volume transports calculated from conductivity temperature depth data, but the former showed much finer temporal structure than those from the geostrophic calculation.

Predictive capabilities of preoperative and postoperative pulmonary function tests in delayed repair of congenital diaphragmatic hernia.

PubMed

Tracy, T F; Bailey, P V; Sadiq, F; Noguchi, A; Silen, M L; Weber, T R

1994-02-01

To improve the survival of newborns with congenital diaphragmatic hernia (CHD), preoperative stabilization with conventional ventilatory therapy and extracorporeal membrane oxygenation (ECMO) have been used. Measurements that quantify pulmonary function may allow an accurate assessment of lethal pulmonary hypoplasia and predict outcome. Pulmonary function tests (PFTs) were obtained in 20 infants preoperatively and postoperatively; these included measurements of compliance, dynamic compliance, and tidal volume. Overall survival was 75%. Six surviving infants were initially managed with ventilator therapy alone, followed by repair (group 1). The remaining 14 patients, who were moribund at presentation or whose initial ventilator therapy failed, were placed on ECMO and received repair during bypass; nine survived (group 2), and five died (group 3). Compliance, dynamic compliance, and tidal volume obtained at initial presentation and immediately preoperatively were significantly higher for group 1 as compared with groups 2 and 3. Infants whose initial compliance was greater than 0.25 mL/cm H2O/kg and initial tidal volume was greater than 3.5 mL/kg did not require ECMO. Ultimate improvement in compliance was noted in 5 of 6 patients in group 1, 8 of 8 patients in group 2, and 5 of 5 in group 3. This improvement followed an initial decline in compliance in 9 of 14 survivors, from 15% to 76%. All six patients in group 1 had tidal volumes of more than 4 mL/kg, as did 7 of 9 patients in group 2. Only one patient among the ECMO nonsurvivors (group 3) had a postoperative tidal volume of this magnitude. These data suggest that initial PFTs may predict which infants will require ECMO.(ABSTRACT TRUNCATED AT 250 WORDS)

Noninvasive measurement of mean alveolar carbon dioxide tension and Bohr's dead space during tidal breathing.

PubMed

Koulouris, N G; Latsi, P; Dimitroulis, J; Jordanoglou, B; Gaga, M; Jordanoglou, J

2001-06-01

The lack of methodology for measuring the alveolar carbon dioxide tension (PA,CO2) has forced investigators to make several assumptions, such as that PA,CO2 is equal to end-tidal (PET,CO2) and arterial CO2 tension (Pa,CO2). The present study measured the mean PA,CO2 and Bohr's dead space ratio (Bohr's dead space/tidal volume (VD,Bohr/VT)) during tidal breathing. The method used is a new, simple and noninvasive technique, based on the analysis of the expired CO2 volume per breath (VCO2) versus the exhaled VT. This curve was analysed in 21 normal, healthy subjects and 35 chronic obstructive pulmonary disease (COPD) patients breathing tidally through a mouthpiece apparatus in the sitting position. It is shown that: 1) PA,CO2 is similar to Pa,CO2 in normal subjects, whilst it is significantly lower than Pa,CO2 in COPD patients; 2) PA,CO2 is significantly higher than PET,CO2 in all subjects, especially in COPD patients; 3) VD,Bohr/VT is increased in COPD patients as compared to normal subjects; and 4) VD,Bohr/VT is lower than the "physiological" dead space ratio (VD,phys/VT) in COPD patients. It is concluded that the expired carbon dioxide versus tidal volume curve is a useful tool for research and clinical work, because it permits the noninvasive and accurate measurement of Bohr's dead space and mean alveolar carbon dioxide tension accurately during spontaneous breathing.

Non-Contact Detection of Breathing Using a Microwave Sensor

PubMed Central

Dei, Devis; Grazzini, Gilberto; Luzi, Guido; Pieraccini, Massimiliano; Atzeni, Carlo; Boncinelli, Sergio; Camiciottoli, Gianna; Castellani, Walter; Marsili, Massimo; Dico, Juri Lo

2009-01-01

In this paper the use of a continuous-wave microwave sensor as a non-contact tool for quantitative measurement of respiratory tidal volume has been evaluated by experimentation in seventeen healthy volunteers. The sensor working principle is reported and several causes that can affect its response are analyzed. A suitable data processing has been devised able to reject the majority of breath measurements taken under non suitable conditions. Furthermore, a relationship between microwave sensor measurements and volume inspired and expired at quiet breathing (tidal volume) has been found. PMID:22574033

Tidal, Residual, Intertidal Mudflat (TRIM) Model and its Applications to San Francisco Bay, California

USGS Publications Warehouse

Cheng, R.T.; Casulli, V.; Gartner, J.W.

1993-01-01

A numerical model using a semi-implicit finite-difference method for solving the two-dimensional shallow-water equations is presented. The gradient of the water surface elevation in the momentum equations and the velocity divergence in the continuity equation are finite-differenced implicitly, the remaining terms are finite-differenced explicitly. The convective terms are treated using an Eulerian-Lagrangian method. The combination of the semi-implicit finite-difference solution for the gravity wave propagation, and the Eulerian-Lagrangian treatment of the convective terms renders the numerical model unconditionally stable. When the baroclinic forcing is included, a salt transport equation is coupled to the momentum equations, and the numerical method is subject to a weak stability condition. The method of solution and the properties of the numerical model are given. This numerical model is particularly suitable for applications to coastal plain estuaries and tidal embayments in which tidal currents are dominant, and tidally generated residual currents are important. The model is applied to San Francisco Bay, California where extensive historical tides and current-meter data are available. The model calibration is considered by comparing time-series of the field data and of the model results. Alternatively, and perhaps more meaningfully, the model is calibrated by comparing the harmonic constants of tides and tidal currents derived from field data with those derived from the model. The model is further verified by comparing the model results with an independent data set representing the wet season. The strengths and the weaknesses of the model are assessed based on the results of model calibration and verification. Using the model results, the properties of tides and tidal currents in San Francisco Bay are characterized and discussed. Furthermore, using the numerical model, estimates of San Francisco Bay's volume, surface area, mean water depth, tidal prisms, and tidal excursions at spring and neap tides are computed. Additional applications of the model reveal, qualitatively the spatial distribution of residual variables. ?? 1993 Academic Press. All rights reserved.

Normalization of respiratory sinus arrhythmia by factoring in tidal volume.

PubMed

Kobayashi, H

1998-09-01

The amplitude of respiratory sinus arrhythmia (RSA) was measured in eight healthy young male students with special reference to the effect of tidal volume (Vt). Under simultaneously controlled respiratory frequency and Vt, the heart rate variability (HRV) of the subjects was measured. While the respiratory frequency was adjusted to either 0.25 or 0.10 Hz, the Vt was controlled at 13 different volumes for each frequency. Linear relationships between RSA amplitude and Vt were observed and close correlations were obtained for 0.25 Hz compared with 0.10 Hz. However, regression equations showed a marked variation among subjects. Furthermore, RSA amplitude was related to vital capacity. Subjects who had lower vital capacity tended to show higher RSA amplitudes at the same Vt. Therefore, the ratio (% Vt) of Vt to vital capacity is a more effective index in normalizing RSA than raw tidal volume. From these results, we have proposed a normalized RSA (RSA amplitude/% Vt) as a new index of autonomic activity that provides a constant value regardless of Vt.

A metabolic simulator for unmanned testing of breathing apparatuses in hyperbaric conditions.

PubMed

Frånberg, Oskar; Loncar, Mario; Larsson, Åke; Ornhagen, Hans; Gennser, Mikael

2014-11-01

A major part of testing of rebreather apparatuses for underwater diving focuses on the oxygen dosage system. A metabolic simulator for testing breathing apparatuses was built and evaluated. Oxygen consumption was achieved through catalytic combustion of propene. With an admixture of carbon dioxide in the propene fuel, the system allowed the respiratory exchange ratio to be set freely within human variability and also made it possible to increase test pressures above the condensation pressure of propene. The system was tested by breathing ambient air in a pressure chamber with oxygen uptake (Vo₂) ranging from 1-4 L · min(-1), tidal volume (VT) from 1-3 L, breathing frequency (f) of 20 and 25 breaths/min, and chamber pressures from 100 to 670 kPa. The measured end-tidal oxygen concentration (Fo₂) was compared to calculated end-tidal Fo₂. The largest average difference in end-tidal Fo₂during atmospheric pressure conditions was 0.63%-points with a 0.28%-point average difference during the whole test. During hyperbaric conditions with pressures ranging from 100 to 670 kPa, the largest average difference in Fo₂was 1.68%-points seen during compression from 100 kPa to 400 kPa and the average difference in Fo₂during the whole test was 0.29%-points. In combination with a breathing simulator simulating tidal breathing, the system can be used for dynamic continuous testing of breathing equipment with changes in VT, f, Vo2, and pressure.

Continental-Margin Processes Recorded in Shelf and Canyon Sediments. Sediment Deposition, Erosion and Accumulation on a Tidal Flat Adjacent to a River Mouth

DTIC Science & Technology

2007-01-01

to the formation and preservation of sedimentary strata in the seabed. The goal of the tidal-flats project during the first year was to help plan ...publish the STRATAFORM Master Volume (results are summarized under Work Completed); and 3) help with planning the Tidal Flats DRI (results are... Plan (White Paper), negotiating with Korean scientists about a modified study in Korea, and helping to identify and explore US tidal flats for

Increasing the inspiratory time and I:E ratio during mechanical ventilation aggravates ventilator-induced lung injury in mice.

PubMed

Müller-Redetzky, Holger C; Felten, Matthias; Hellwig, Katharina; Wienhold, Sandra-Maria; Naujoks, Jan; Opitz, Bastian; Kershaw, Olivia; Gruber, Achim D; Suttorp, Norbert; Witzenrath, Martin

2015-01-28

Lung-protective ventilation reduced acute respiratory distress syndrome (ARDS) mortality. To minimize ventilator-induced lung injury (VILI), tidal volume is limited, high plateau pressures are avoided, and positive end-expiratory pressure (PEEP) is applied. However, the impact of specific ventilatory patterns on VILI is not well defined. Increasing inspiratory time and thereby the inspiratory/expiratory ratio (I:E ratio) may improve oxygenation, but may also be harmful as the absolute stress and strain over time increase. We thus hypothesized that increasing inspiratory time and I:E ratio aggravates VILI. VILI was induced in mice by high tidal-volume ventilation (HVT 34 ml/kg). Low tidal-volume ventilation (LVT 9 ml/kg) was used in control groups. PEEP was set to 2 cm H2O, FiO2 was 0.5 in all groups. HVT and LVT mice were ventilated with either I:E of 1:2 (LVT 1:2, HVT 1:2) or 1:1 (LVT 1:1, HVT 1:1) for 4 hours or until an alternative end point, defined as mean arterial blood pressure below 40 mm Hg. Dynamic hyperinflation due to the increased I:E ratio was excluded in a separate group of animals. Survival, lung compliance, oxygenation, pulmonary permeability, markers of pulmonary and systemic inflammation (leukocyte differentiation in lung and blood, analyses of pulmonary interleukin-6, interleukin-1β, keratinocyte-derived chemokine, monocyte chemoattractant protein-1), and histopathologic pulmonary changes were analyzed. LVT 1:2 or LVT 1:1 did not result in VILI, and all individuals survived the ventilation period. HVT 1:2 decreased lung compliance, increased pulmonary neutrophils and cytokine expression, and evoked marked histologic signs of lung injury. All animals survived. HVT 1:1 caused further significant worsening of oxygenation, compliance and increased pulmonary proinflammatory cytokine expression, and pulmonary and blood neutrophils. In the HVT 1:1 group, significant mortality during mechanical ventilation was observed. According to the "baby lung" concept, mechanical ventilation-associated stress and strain in overinflated regions of ARDS lungs was simulated by using high tidal-volume ventilation. Increase of inspiratory time and I:E ratio significantly aggravated VILI in mice, suggesting an impact of a "stress/strain × time product" for the pathogenesis of VILI. Thus increasing the inspiratory time and I:E ratio should be critically considered.

Perfluorocarbon-associated gas exchange in normal and acid-injured large sheep.

PubMed

Hernan, L J; Fuhrman, B P; Kaiser, R E; Penfil, S; Foley, C; Papo, M C; Leach, C L

1996-03-01

We hypothesized that a) perfluorocarbon-associated gas exchange could be accomplished in normal large sheep; b) the determinants of gas exchange would be similar during perfluorocarbon-associated gas exchange and conventional gas ventilation; c)in large animals with lung injury, perfluorocarbon-associated gas exchange could be used to enhance gas exchange without adverse effects on hemodynamics; and d) the large animal with lung injury could be supported with an FIO2 of <1.0 during perfluorocarbon-associated gas exchange. Prospective, observational animal study and prospective randomized, controlled animal study. An animal laboratory in a university setting. Thirty adult ewes. Five normal ewes (61.0 +/- 4.0 kg) underwent perfluorocarbon-associated gas exchange to ascertain the effects of tidal volume, end-inspiratory pressure, and positive end-expiratory pressure (PEEP) on oxygenation. Respiratory rate, tidal volume, and minute ventilation were studied to determine their effects on CO2 clearance. Sheep, weighing 58.9 +/- 8.3 kg, had lung injury induced by instilling 2 mL/kg of 0.05 Normal hydrochloric acid into the trachea. Five minutes after injury, PEEP was increased to 10 cm H2O. Ten minutes after injury, sheep with Pao2 values of <100 torr (<13.3 kPa) were randomized to continue gas ventilation (control, n=9) or to institute perfluorocarbon-associated gas exchange (n=9) by instilling 1.6 L of unoxygenated perflubron into the trachea and resuming gas ventilation. Blood gas and hemodynamic measurements were obtained throughout the 4-hr study. Both tidal volume and end-inspiratory pressure influenced oxygenation in normal sheep during perfluorocarbon-associated gas exchange. Minute ventilation determined CO2 clearance during perfluorocarbon-associated gas exchange in normal sheep. After acid aspiration lung injury, perfluorocarbon-associated gas exchange increased PaO2 and reduced intrapulmonary shunt fraction. Hypoxia and intrapulmonary shunting were unabated after injury in control animals. Hemodynamics were not influenced by the institution of perfluorocarbon-associated gas exchange. Tidal volume and end-inspiratory pressure directly influence oxygenation during perfluorocarbon-associated gas exchange in large animals. Minute ventilation influences clearance of CO2. In adult sheep with acid aspiration lung injury, perfluorocarbon-associated gas exchange at an FIO2 of <1.0 supports oxygenation and improves intrapulmonary shunting, without adverse hemodynamic effects, when compared with conventional gas ventilation.

Lung gas volumes and expiratory time constant in immature newborn rabbits treated with natural or synthetic surfactant or detergents.

PubMed

Bongrani, S; Fornasier, M; Papotti, M; Razzetti, R; Robertson, B

1994-01-01

Immature newborn rabbits delivered at a gestational age of 27 days were tracheotomized and treated, via the tracheal cannula, with clinically recommended doses of natural or synthetic surfactant (Curosurf and Exosurf, respectively). Littermates received 0.1% tyloxapol, 5% Tween 20, or saline. The dose volume of Curosurf was 2.5 ml/kg, that of the other materials 5 ml/kg. Animals were kept in a multiplethysmograph system and ventilated for 30 min with a standardized sequence of insufflation pressures. End-expiratory lung gas volume was calculated at the end of the experiment from measurements of lung weight and total lung volume. Tidal volumes were significantly improved in all groups of animals receiving surfactant or detergents. However, expiratory time constant (determined from the tidal volume tracing) was significantly longer, and end-expiratory gas volume significantly larger, in animals treated with Curosurf than in those receiving Exosurf or detergents. These differences were confirmed by semiquantitative evaluation of alveolar air expansion in histological sections. In addition, airway epithelial necrosis was reduced in animals receiving Curosurf, Exosurf, or Tween 20, but not in animals treated with tyloxapol. The discrepancy between improvements in tidal volume, expiratory time constant, and end-expiratory gas volume reflects failure of lung stabilization in animals treated with Exosurf or detergents, probably due to absence of specific hydrophobic proteins in the synthetic products.

Diaphragm electrical activity during negative lower torso pressure in quadriplegic men.

PubMed

Banzett, R B; Inbar, G F; Brown, R; Goldman, M; Rossier, A; Mead, J

1981-09-01

We recorded the diaphragm electromyogram (EMG) of quadriplegic men before and during exposure of the lower torso to continuous negative pressure, which caused shortening of the inspiratory muscles by expanding the respiratory system by one tidal volume. The moving-time-averaged diaphragm EMG was larger during expansion of the respiratory system. When we repeated the experiment with subjects who breathed through a mouthpiece, we found qualitatively similar EMG changes and little or no change in tidal volume or end-tidal CO2 partial pressure. When the pressure was applied or removed rapidly, changes in EMG occurred within one or two breaths. Because end-tidal CO2 partial pressure did not increase, and because the response was rapid, we suggest that the response results from proprioceptive, rather than chemoreceptive, reflexes. As most of these men had complete spinal lesions at C6 or C7 the afferent pathways are likely to be vagal or phrenic.

The performances of standard and ResMed masks during bag-valve-mask ventilation.

PubMed

Lee, Hyoung Youn; Jeung, Kyung Woon; Lee, Byung Kook; Lee, Seung Joon; Jung, Yong Hun; Lee, Geo Sung; Min, Yong Il; Heo, Tag

2013-01-01

A tight mask seal is frequently difficult to obtain and maintain during single-rescuer bag-valve-mask (BVM) ventilation. The ResMed mask (Bella Vista, NSW, Australia) is a continuous-positive-airway-pressure mask (CM) designed for noninvasive ventilation. In this study, we compared the ventilation performances of a standard mask (SM) and a ResMed CM using a simulation manikin in an out-of-hospital single-rescuer BVM ventilation scenario. Thirty emergency medical technicians (EMTs) performed two 2-minute attempts to ventilate a simulation manikin using BVM ventilation, alternatively, with the SM or the ResMed CM in a randomized order. Ventilation parameters including tidal volume and peak airway pressure were measured using computer analysis software connected to the simulation manikin. Successful volume delivery was defined as delivery of 440-540 mL of tidal volume in accord with present cardiopulmonary resuscitation guidelines. BVM ventilation using the ResMed CM produced higher mean (± standard deviation) tidal volumes (452 ± 50 mL vs. 394 ± 113 mL, p = 0.014) and had a higher proportion of successful volume deliveries (65.3% vs. 26.7%, p < 0.001) than that using the SM. Peak airway pressure was higher in BVM ventilation using the ResMed CM (p = 0.035). Stomach insufflation did not occur during either method. Twenty-nine of the participants (96.7%) preferred BVM ventilation using the ResMed CM. BVM ventilations using ResMed CM resulted in a significantly higher proportion of successful volume deliveries meeting the currently recommended range of tidal volume. Clinical studies are needed to determine the value of the ResMed CM for BVM ventilation.

Performance of the Volumetric Diffusive Respirator at Altitude

DTIC Science & Technology

2014-08-18

information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT DATE (DD-MM...increased by 30-40%. Tidal volume remained within 15% of sea level values. Respiratory rate fell, while inspiratory time increased and high frequency...altitude, positive end expiratory pressure and peak inspiratory pressure were increased by 30-40%. Tidal volume remained within 15% of sea level

Continuous distributions of specific ventilation recovered from inert gas washout

NASA Technical Reports Server (NTRS)

Lewis, S. M.; Evans, J. W.; Jalowayski, A. A.

1978-01-01

A new technique is described for recovering continuous distributions of ventilation as a function of tidal ventilation/volume ratio from the nitrogen washout. The analysis yields a continuous distribution of ventilation as a function of tidal ventilation/volume ratio represented as fractional ventilations of 50 compartments plus dead space. The procedure was verified by recovering known distributions from data to which noise had been added. Using an apparatus to control the subject's tidal volume and FRC, mixed expired N2 data gave the following results: (a) the distributions of young, normal subjects were narrow and unimodal; (b) those of subjects over age 40 were broader with more poorly ventilated units; (c) patients with pulmonary disease of all descriptions showed enlarged dead space; (d) patients with cystic fibrosis showed multimodal distributions with the bulk of the ventilation going to overventilated units; and (e) patients with obstructive lung disease fell into several classes, three of which are illustrated.

Controlled breathing protocols probe human autonomic cardiovascular rhythms

NASA Technical Reports Server (NTRS)

Cooke, W. H.; Cox, J. F.; Diedrich, A. M.; Taylor, J. A.; Beightol, L. A.; Ames, J. E. 4th; Hoag, J. B.; Seidel, H.; Eckberg, D. L.

1998-01-01

The purpose of this study was to determine how breathing protocols requiring varying degrees of control affect cardiovascular dynamics. We measured inspiratory volume, end-tidal CO2, R-R interval, and arterial pressure spectral power in 10 volunteers who followed the following 5 breathing protocols: 1) uncontrolled breathing for 5 min; 2) stepwise frequency breathing (at 0.3, 0.25, 0.2, 0.15, 0.1, and 0.05 Hz for 2 min each); 3) stepwise frequency breathing as above, but with prescribed tidal volumes; 4) random-frequency breathing (approximately 0.5-0.05 Hz) for 6 min; and 5) fixed-frequency breathing (0.25 Hz) for 5 min. During stepwise breathing, R-R interval and arterial pressure spectral power increased as breathing frequency decreased. Control of inspired volume reduced R-R interval spectral power during 0.1 Hz breathing (P < 0.05). Stepwise and random-breathing protocols yielded comparable coherence and transfer functions between respiration and R-R intervals and systolic pressure and R-R intervals. Random- and fixed-frequency breathing reduced end-tidal CO2 modestly (P < 0.05). Our data suggest that stringent tidal volume control attenuates low-frequency R-R interval oscillations and that fixed- and random-rate breathing may decrease CO2 chemoreceptor stimulation. We conclude that autonomic rhythms measured during different breathing protocols have much in common but that a stepwise protocol without stringent control of inspired volume may allow for the most efficient assessment of short-term respiratory-mediated autonomic oscillations.

Assessment of regional ventilation and deformation using 4D-CT imaging for healthy human lungs during tidal breathing

PubMed Central

Jahani, Nariman; Choi, Jiwoong; Iyer, Krishna; Hoffman, Eric A.

2015-01-01

This study aims to assess regional ventilation, nonlinearity, and hysteresis of human lungs during dynamic breathing via image registration of four-dimensional computed tomography (4D-CT) scans. Six healthy adult humans were studied by spiral multidetector-row CT during controlled tidal breathing as well as during total lung capacity and functional residual capacity breath holds. Static images were utilized to contrast static vs. dynamic (deep vs. tidal) breathing. A rolling-seal piston system was employed to maintain consistent tidal breathing during 4D-CT spiral image acquisition, providing required between-breath consistency for physiologically meaningful reconstructed respiratory motion. Registration-derived variables including local air volume and anisotropic deformation index (ADI, an indicator of preferential deformation in response to local force) were employed to assess regional ventilation and lung deformation. Lobar distributions of air volume change during tidal breathing were correlated with those of deep breathing (R2 ≈ 0.84). Small discrepancies between tidal and deep breathing were shown to be likely due to different distributions of air volume change in the left and the right lungs. We also demonstrated an asymmetric characteristic of flow rate between inhalation and exhalation. With ADI, we were able to quantify nonlinearity and hysteresis of lung deformation that can only be captured in dynamic images. Nonlinearity quantified by ADI is greater during inhalation, and it is stronger in the lower lobes (P < 0.05). Lung hysteresis estimated by the difference of ADI between inhalation and exhalation is more significant in the right lungs than that in the left lungs. PMID:26316512

Risk factors of bronchial hyperresponsiveness in children with wheezing-associated respiratory infection.

PubMed

Futrakul, Sitthivuddhi; Deerojanawong, Jitladda; Prapphal, Nuanchan

2005-07-01

The objectives of this study were to identify possible risk factors of bronchial hyperesponsiveness (BHR) in children up to 5 years of age with wheezing-associated respiratory infection (WARI), and to study the prevalence of BHR. Children up to 5 years of age with WARI were enrolled in the study. The parents or caregivers of children were asked about their demographic data and clinical histories. Physical examination and clinical score assessment were performed. Pulmonary function tests, i.e., tidal breathing flow volume (TBFV), were performed to measure tidal breathing parameters before and after salbutamol nebulization. If volume at peak tidal expiratory flow/expiratory tidal volume and time to peak expiratory flow/total expiratory time increased > or = 20%, or tidal expiratory flow at 25% of tidal volume/peak tidal expiratory flow increased > or = 20% after nebulization therapy, BHR was diagnosed. The number in the positive BHR group was used to calculate the prevalence of BHR, and clinical features were compared with those of the negative BHR group. Categorical data were analyzed for statistical significance (P < 0.05) by chi-square test or Fisher's exact test, or Student's t-test, as appropriate. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated for those with statistical significance. One hundred and six wheezing children underwent pulmonary function tests before and after salbutamol nebulization. With the aforementioned criteria, 41 cases (38.7%) were diagnosed with BHR. History of reactive airway disease, (OR, 6.31; 95% CI, 1.68-25), maternal history of asthma (OR, 3.45; 95% CI, 1.34-9), breastfeeding less than 3 months (OR, 3.18; 95% CI, 1.26-8.12), and passive smoking (OR, 3; 95% CI, 1.15-7.62) were significant risk factors of BHR. The eosinophil count was significantly higher in the BHR (+) group particularly, in children 1-5 years of age (P < or = 0.01). Patchy infiltrates were more commonly found in patients with negative BHR but not statistically significant. In conclusion, a history of reactive airway disease, maternal history, breastfeeding less than 3 months, and passive smoking were significant risk factors for BHR. Copyright 2005 Wiley-Liss, Inc.

[Lung protective ventilation. Ventilatory modes and ventilator parameters].

PubMed

Schädler, Dirk; Weiler, Norbert

2008-06-01

Mechanical ventilation has a considerable potential for injuring the lung tissue. Therefore, attention has to be paid to the proper choice of ventilatory mode and settings to secure lung-protective ventilation whenever possible. Such ventilator strategy should account for low tidal volume ventilation (6 ml/kg PBW), limited plateau pressure (30 to 35 cm H2O) and positive end-expiratory pressure (PEEP). It is unclear whether pressure controlled or volume controlled ventilation with square flow profile is beneficial. The adjustment of inspiration and expiration time should consider the actual breathing mechanics and anticipate the generation of intrinsic PEEP. Ventilatory modes with the possibility of supporting spontaneous breathing should be used as soon as possible.

Effects of increasing seawater circulation by tidal power plant operation on the water quality in the Shihwa coastal reservoir, Republic of Korea

NASA Astrophysics Data System (ADS)

Lee, B. Y.; Lee, C. H.; KIm, K. T.

2016-02-01

Since 2012 to present, the Tidal Power Plant (TPP) has been operated in Shihwa Coastal Reservoir (SCR) to improve the water quality. The tidal mixing volume increased about 5 times from 0.03 to 0.16 billion ton/day which represents about 50% of the SCR water volume. Water quality monitoring data showed that it break a strong stratification and hypoxia (≤3 mg/L Dissolved Oxygen) during summer season in main tidal channel. In addition, Total Phosphorus (TP), Total Nitrogen (TN) and Chemical Oxygen Demand concentrations in the main tidal channel reached to similar level with outside SCR concentrations. However, inner area with limited tidal mixing has not experienced improvement in TN and TP concentrations after the TPP operation. Trophic State Index (TSI) which was composite index of trophic condition also kept high score (>50) and remained in eutrophic state especially in summer season. Overall, an increase of seawater circulation has a positive effect on water quality in main tidal channel but not in inner area because of limited seawater mixing and effects of stormwater runoff. The stormwater runoff should be properly managed in this case because most point source pollution load is discharged outside of SCR. Acknowledgement : This research was a part of the project titled 'Development of integrated estuarine management system', funded by the Ministry of Oceans and Fisheries, Korea

Alveolar edema dispersion and alveolar protein permeability during high volume ventilation: effect of positive end-expiratory pressure.

PubMed

de Prost, Nicolas; Roux, Damien; Dreyfuss, Didier; Ricard, Jean-Damien; Le Guludec, Dominique; Saumon, Georges

2007-04-01

To evaluate whether PEEP affects intrapulmonary alveolar edema liquid movement and alveolar permeability to proteins during high volume ventilation. Experimental study in an animal research laboratory. 46 male Wistar rats. A (99m)Tc-labeled albumin solution was instilled in a distal airway to produce a zone of alveolar flooding. Conventional ventilation (CV) was applied for 30 min followed by various ventilation strategies for 3 h: CV, spontaneous breathing, and high volume ventilation with different PEEP levels (0, 6, and 8 cmH(2)O) and different tidal volumes. Dispersion of the instilled liquid and systemic leakage of (99m)Tc-albumin from the lungs were studied by scintigraphy. The instillation protocol produced a zone of alveolar flooding that stayed localized during CV or spontaneous breathing. High volume ventilation dispersed alveolar liquid in the lungs. This dispersion was prevented by PEEP even when tidal volume was the same and thus end-inspiratory pressure higher. High volume ventilation resulted in the leakage of instilled (99m)Tc-albumin from the lungs. This increase in alveolar albumin permeability was reduced by PEEP. Albumin permeability was more affected by the amplitude of tidal excursions than by overall lung distension. PEEP prevents the dispersion of alveolar edema liquid in the lungs and lessens the increase in alveolar albumin permeability due to high volume ventilation.

Spontaneous Effort During Mechanical Ventilation: Maximal Injury With Less Positive End-Expiratory Pressure.

PubMed

Yoshida, Takeshi; Roldan, Rollin; Beraldo, Marcelo A; Torsani, Vinicius; Gomes, Susimeire; De Santis, Roberta R; Costa, Eduardo L V; Tucci, Mauro R; Lima, Raul G; Kavanagh, Brian P; Amato, Marcelo B P

2016-08-01

We recently described how spontaneous effort during mechanical ventilation can cause "pendelluft," that is, displacement of gas from nondependent (more recruited) lung to dependent (less recruited) lung during early inspiration. Such transfer depends on the coexistence of more recruited (source) liquid-like lung regions together with less recruited (target) solid-like lung regions. Pendelluft may improve gas exchange, but because of tidal recruitment, it may also contribute to injury. We hypothesize that higher positive end-expiratory pressure levels decrease the propensity to pendelluft and that with lower positive end-expiratory pressure levels, pendelluft is associated with improved gas exchange but increased tidal recruitment. Crossover design. University animal research laboratory. Anesthetized landrace pigs. Surfactant depletion was achieved by saline lavage in anesthetized pigs, and ventilator-induced lung injury was produced by ventilation with high tidal volume and low positive end-expiratory pressure. Ventilation was continued in each of four conditions: positive end-expiratory pressure (low or optimized positive end-expiratory pressure after recruitment) and spontaneous breathing (present or absent). Tidal recruitment was assessed using dynamic CT and regional ventilation/perfusion using electric impedance tomography. Esophageal pressure was measured using an esophageal balloon manometer. Among the four conditions, spontaneous breathing at low positive end-expiratory pressure not only caused the largest degree of pendelluft, which was associated with improved ventilation/perfusion matching and oxygenation, but also generated the greatest tidal recruitment. At low positive end-expiratory pressure, paralysis worsened oxygenation but reduced tidal recruitment. Optimized positive end-expiratory pressure decreased the magnitude of spontaneous efforts (measured by esophageal pressure) despite using less sedation, from -5.6 ± 1.3 to -2.0 ± 0.7 cm H2O, while concomitantly reducing pendelluft and tidal recruitment. No pendelluft was observed in the absence of spontaneous effort. Spontaneous effort at low positive end-expiratory pressure improved oxygenation but promoted tidal recruitment associated with pendelluft. Optimized positive end-expiratory pressure (set after lung recruitment) may reverse the harmful effects of spontaneous breathing by reducing inspiratory effort, pendelluft, and tidal recruitment.

Postoperative Pulmonary Atelectasis and Collapse, and its Prophylaxis with Intravenous Bicarbonate

PubMed Central

O'Driscoll, M.

1970-01-01

Of 181 patients undergoing major abdominal surgery 116 developed chest complications associated with a metabolic acidosis, low Pco2, depressed tidal volume, increased respiratory rate, but no increase in minute volume. In a matched group of 116 patients given intravenous bicarbonate postoperatively only 15 developed chest complications. This suggests that respiratory physiological dead space decreases in patients with pulmonary collapse and atelectasis following surgery. Acidotic respiration proved inefficient in the postoperative period, and intravenous bicarbonate had a very pronounced effect on the tidal and minute volumes of acidotic patients with pulmonary collapse and atelectasis. PMID:5470431

Non-invasive measurement of the mean alveolar O(2) tension from the oxygen uptake versus tidal volume curve.

PubMed

Jordanoglou, J; Latsi, P; Chroneou, A; Koulouris, N G

2007-10-01

The classical equations for measuring the mean and the ideal alveolar O(2) tension are based on assumptions, which are shown to be invalid. So we thought to develop a new, non-invasive method for measuring the mean alveolar P,O(2) within the volume domain (PA,O(2(Bohr))). This method is based on the oxygen uptake vs. tidal volume curve (VO(2) vs. VT) obtained during tidal breathing of room air and/or air enriched with oxygen. PA,O(2(Bohr)) and the ideal alveolar PO(2) (PA,O(2(ideal))) were simultaneously measured in 10 healthy subjects and 34 patients suffering from chronic obstructive pulmonary disease (COPD) breathing tidally room air at rest. Additionally, 10 subjects (three healthy subjects and seven COPD patients) were studied while breathing initially room air and subsequently air enriched with oxygen. According to the results, PA,O(2(Bohr)) considerably differed from PA,O(2(ideal)) (P = 0.004). The cause of the difference, at the individual's R, is: (1) the difference between the arterial and Bohr's alveolar CO(2) tension, mainly in COPD patients, and (2) the inequality between Bohr's alveolar part of the tidal volume for CO(2) and O(2). Furthermore, end-tidal gas tension (PET,CO(2) and PET,O(2)) differed from Pa,CO(2) and PA,O(2(Bohr)) respectively. The deviation of PA,O(2(Bohr)) from PA,O(2(ideal)) has a definite impact on Bohr's dead space ratio for O(2) and CO(2), and on the alveolar-arterial O(2) difference. The difference (PA,O(2(Bohr)) - PA,O(2(ideal))) is not related to the pathology of the disease. So, gas exchange within the lungs should be assessed at the subject's R from PA,O(2(Bohr)) and PA,CO(2(Bohr)) but not from PA,O(2(ideal)) nor Pa,CO(2).

Alveolar Tidal recruitment/derecruitment and Overdistension During Four Levels of End-Expiratory Pressure with Protective Tidal Volume During Anesthesia in a Murine Lung-Healthy Model.

PubMed

Soares, Joao Henrique Neves; Carvalho, Alysson Roncally; Bergamini, Bruno Curty; Gress, Maria Alice Kuster; Jandre, Frederico Caetano; Zin, Walter Araujo; Giannella-Neto, Antonio

2018-06-01

We compared respiratory mechanics between the positive end-expiratory pressure of minimal respiratory system elastance (PEEP minErs ) and three levels of PEEP during low-tidal-volume (6 mL/kg) ventilation in rats. Twenty-four rats were anesthetized, paralyzed, and mechanically ventilated. Airway pressure (P aw ), flow (F), and volume (V) were fitted by a linear single compartment model (LSCM) P aw (t) = E rs  × V(t) + R rs  × F(t) + PEEP or a volume- and flow-dependent SCM (VFDSCM) P aw (t) = (E 1  + E 2  × V(t)) × V(t) + (K 1  + K 2  × |F(t)|) × F(t) + PEEP, where E rs and R rs are respiratory system elastance and resistance, respectively; E 1 and E 2 × V are volume-independent and volume-dependent E rs , respectively; and K 1 and K 2  × F are flow-independent and flow-dependent R rs , respectively. Animals were ventilated for 1 h at PEEP 0 cmH 2 O (ZEEP); PEEP minErs ; 2 cmH 2 O above PEEP minErs (PEEP minErs+2 ); or 4 cmH 2 O above PEEP minErs (PEEP minErs+4 ). Alveolar tidal recruitment/derecruitment and overdistension were assessed by the index %E 2  = 100 × [(E 2  × V T )/(E 1  + |E 2 | × V T )], and alveolar stability by the slope of E rs (t). %E 2 varied between 0 and 30% at PEEP minErs in most respiratory cycles. Alveolar Tidal recruitment/derecruitment (%E 2  < 0) and overdistension (%E 2  > 30) were predominant in the absence of PEEP and in PEEP levels higher than PEEP minErs , respectively. The slope of E rs (t) was different from zero in all groups besides PEEP minErs+4 . PEEP minErs presented the best compromise between alveolar tidal recruitment/derecruitment and overdistension, during 1 h of low-V T mechanical ventilation.

Automated respiratory cycles selection is highly specific and improves respiratory mechanics analysis.

PubMed

Rigo, Vincent; Graas, Estelle; Rigo, Jacques

2012-07-01

Selected optimal respiratory cycles should allow calculation of respiratory mechanic parameters focusing on patient-ventilator interaction. New computer software automatically selecting optimal breaths and respiratory mechanics derived from those cycles are evaluated. Retrospective study. University level III neonatal intensive care unit. Ten mins synchronized intermittent mandatory ventilation and assist/control ventilation recordings from ten newborns. The ventilator provided respiratory mechanic data (ventilator respiratory cycles) every 10 secs. Pressure, flow, and volume waves and pressure-volume, pressure-flow, and volume-flow loops were reconstructed from continuous pressure-volume recordings. Visual assessment determined assisted leak-free optimal respiratory cycles (selected respiratory cycles). New software graded the quality of cycles (automated respiratory cycles). Respiratory mechanic values were derived from both sets of optimal cycles. We evaluated quality selection and compared mean values and their variability according to ventilatory mode and respiratory mechanic provenance. To assess discriminating power, all 45 "t" values obtained from interpatient comparisons were compared for each respiratory mechanic parameter. A total of 11,724 breaths are evaluated. Automated respiratory cycle/selected respiratory cycle selections agreement is high: 88% of maximal κ with linear weighting. Specificity and positive predictive values are 0.98 and 0.96, respectively. Averaged values are similar between automated respiratory cycle and ventilator respiratory cycle. C20/C alone is markedly decreased in automated respiratory cycle (1.27 ± 0.37 vs. 1.81 ± 0.67). Tidal volume apparent similarity disappears in assist/control: automated respiratory cycle tidal volume (4.8 ± 1.0 mL/kg) is significantly lower than for ventilator respiratory cycle (5.6 ± 1.8 mL/kg). Coefficients of variation decrease for all automated respiratory cycle parameters in all infants. "t" values from ventilator respiratory cycle data are two to three times higher than ventilator respiratory cycles. Automated selection is highly specific. Automated respiratory cycle reflects most the interaction of both ventilator and patient. Improving discriminating power of ventilator monitoring will likely help in assessing disease status and following trends. Averaged parameters derived from automated respiratory cycles are more precise and could be displayed by ventilators to improve real-time fine tuning of ventilator settings.

Water Resources Data, New Jersey, Water Year 2003; Volume 1. Surface-Water Data

USGS Publications Warehouse

Reed, T.J.; White, B.T.; Centinaro, G.L.; Dudek, J.F.; Protz, A.R.; Shvanda, J.C.; Watson, A.F.

2004-01-01

Water-resources data for the 2003 Water Year for New Jersey are presented in three volumes, and consists of records of stage, discharge, and water quality of streams; stage and contents of lakes and reservoirs; and water levels and water quality of ground water. Volume 1 contains discharge records for 100 gaging stations; tide summaries at 29 tidal gaging stations; and stage and contents at 39 lakes and reservoirs. Also included are stage and discharge for 106 crest-stage partial-record stations, stage-only at 33 tidal crest-stage gages, and discharge for 142 low-flow partial- record stations. Locations of these sites are shown in figures 8-11. Additional discharge measurements were made at 143 miscellaneous sites that are not part of the systematic data-collection program. Discontinued station tables for gaging stations, crest-stage gages, tidal crest-stage and tidal gaging stations show historical coverage. The data in this report represent that part of the National Water Information System (NWIS) data collected by the United States Geological Survey (USGS). Hydrologic conditions are also described for this water year, including streamflow, precipitation, reservoir conditions, and air temperatures.

Water resources data, New Jersey, water year 2005. Volume 1 - surface-water data

USGS Publications Warehouse

White, B.T.; Hoppe, H.L.; Centinaro, G.L.; Dudek, J.F.; Painter, B.S.; Protz, A.R.; Reed, T.J.; Shvanda, J.C.; Watson, A.F.

2006-01-01

Water-resources data for the 2005 water year for New Jersey are presented in three volumes, and consists of records of stage, discharge, and water-quality of streams; stage and contents of lakes and reservoirs; and water levels and water-quality of ground water. Volume 1 contains discharge records for 103 gaging stations; tide summaries at 28 tidal gaging stations; stage and contents at 34 lakes and reservoirs; and diversions from 50 surface-water sources. Also included are stage and discharge for 116 crest-stage partial-record stations, stage-only at 33 tidal crest-stage gages, and discharge for 155 low-flow partial-record stations. Locations of these sites are shown in figures 8-11. Additional discharge measurements were made at 222 miscellaneous sites that are not part of the systematic data-collection program. Discontinued station tables for gaging stations, crest-stage gages, tidal crest-stage and tidal gaging stations show historical coverage. The data in this report represent that part of the National Water Information System (NWIS) data collected by the United States Geological Survey (USGS). Hydrologic conditions are also described for this water year, including stream-flow, precipitation, reservoir conditions, and air temperatures.

Water resources data, New Jersey, water year 2004-volume 1. surface-water data

USGS Publications Warehouse

Centinaro, G.L.; White, B.T.; Hoppe, H.L.; Dudek, J.F.; Protz, A.R.; Reed, T.J.; Shvanda, J.C.; Watson, A.F.

2005-01-01

Water-resources data for the 2004 water year for New Jersey are presented in three volumes, and consists of records of stage, discharge, and water-quality of streams; stage and contents of lakes and reservoirs; and water levels and water-quality of ground water. Volume 1 contains discharge records for 105 gaging stations; tide summaries at 27 tidal gaging stations; stage and contents at 39 lakes and reservoirs; and diversions from 51 surface-water sources. Also included are stage and discharge for 108 crest-stage partial-record stations, stage-only at 34 tidal crest-stage gages, and discharge for 124 low-flow partial-record stations. Locations of these sites are shown in figures 8-11. Additional discharge measurements were made at 131 miscellaneous sites that are not part of the systematic data-collection program. Discontinued station tables for gaging stations, crest-stage gages, tidal crest-stage and tidal gaging stations show historical coverage. The data in this report represent that part of the National Water Information System (NWIS) data collected by the United States Geological Survey (USGS). Hydrologic conditions are also described for this water year, including stream-flow, precipitation, reservoir conditions, and air temperatures.

Reliability of Displayed Tidal Volume in Healthy and Surfactant-Depleted Piglets.

PubMed

Mendiondo Luedloff, A Cecilia; Thurman, Tracy L; Holt, Shirley J; Bai, Shasha; Heulitt, Mark J; Courtney, Sherry E

2016-12-01

Volutrauma has been established as the key factor in ventilator-induced lung injury and can only be avoided if tidal volume (V T ) is accurately displayed and delivered. The purpose of this study was to investigate the accuracy of displayed exhaled V T in a ventilator commonly used in small infants with or without a proximal flow sensor and using 3 methods to achieve a target V T in both a healthy and lung-injured neonatal pig model. This was a prospective animal study utilizing 8 male pigs, approximately 2.0 kg (range 1.8-2.2 kg). Intubated, sedated, neonatal pigs were studied with both healthy and injured lungs using the Servo-i ventilator. In pressure-regulated volume control, both with and without a proximal flow sensor, we used 3 methods to set V T : (1) circuit compliance compensation (CCC) on, set V T 6-8 mL/kg; (2) CCC off, calculated V T using the manufacturer's circuit compliance factor; and (3) CCC off, set V T 10-12 mL/kg to approximate a target V T of 6-8 mL/kg. Ventilator-displayed exhaled V T measurements were compared with exhaled V T measured at the airway opening by a calibrated pneumotachograph. Bland-Altman plots were constructed to show the level of agreement between the two. CCC improved accuracy and precision of displayed exhaled V T when the sensor was not used, more markedly in the lung-injured model. Without CCC, the sensor improved accuracy and precision of displayed exhaled V T , again more markedly in the lung-injured model. When the Servo-i ventilator is used in neonates, CCC or the in-line sensor should be employed due to the large positive bias and imprecision seen with CCC off and no sensor in-line. Copyright © 2016 by Daedalus Enterprises.

Protective mechanical ventilation in United Kingdom critical care units: A multicentre audit

PubMed Central

Martin, Matthew J; Richardson, Neil; Bourdeaux, Christopher P

2016-01-01

Lung protective ventilation is becoming increasingly used for all critically ill patients being mechanically ventilated on a mandatory ventilator mode. Compliance with the universal application of this ventilation strategy in intensive care units in the United Kingdom is unknown. This 24-h audit of ventilation practice took place in 16 intensive care units in two regions of the United Kingdom. The mean tidal volume for all patients being ventilated on a mandatory ventilator mode was 7.2(±1.4) ml kg−1 predicted body weight and overall compliance with low tidal volume ventilation (≤6.5 ml kg−1 predicted body weight) was 34%. The mean tidal volume for patients ventilated with volume-controlled ventilation was 7.0(±1.2) ml kg−1 predicted body weight and 7.9(±1.8) ml kg−1 predicted body weight for pressure-controlled ventilation (P < 0.0001). Overall compliance with recommended levels of positive end-expiratory pressure was 72%. Significant variation in practice existed both at a regional and individual unit level. PMID:28979556

Protective mechanical ventilation in United Kingdom critical care units: A multicentre audit.

PubMed

Newell, Christopher P; Martin, Matthew J; Richardson, Neil; Bourdeaux, Christopher P

2017-05-01

Lung protective ventilation is becoming increasingly used for all critically ill patients being mechanically ventilated on a mandatory ventilator mode. Compliance with the universal application of this ventilation strategy in intensive care units in the United Kingdom is unknown. This 24-h audit of ventilation practice took place in 16 intensive care units in two regions of the United Kingdom. The mean tidal volume for all patients being ventilated on a mandatory ventilator mode was 7.2(±1.4) ml kg -1 predicted body weight and overall compliance with low tidal volume ventilation (≤6.5 ml kg -1 predicted body weight) was 34%. The mean tidal volume for patients ventilated with volume-controlled ventilation was 7.0(±1.2) ml kg -1 predicted body weight and 7.9(±1.8) ml kg -1 predicted body weight for pressure-controlled ventilation ( P  < 0.0001). Overall compliance with recommended levels of positive end-expiratory pressure was 72%. Significant variation in practice existed both at a regional and individual unit level.

Respiratory system loop gain in normal men and women measured with proportional-assist ventilation.

PubMed

Wellman, Andrew; Malhotra, Atul; Fogel, Robert B; Edwards, Jill K; Schory, Karen; White, David P

2003-01-01

We hypothesized that increased chemical control instability (CCI) in men could partially explain the male predominance in obstructive sleep apnea (OSA). CCI was assessed by sequentially increasing respiratory control system loop gain (LG) with proportional-assist ventilation (PAV) in 10 men (age 24-48 yr) and 9 women (age 22-36 yr) until periodic breathing or awakening occurred. Women were studied in both the follicular and luteal phases of the menstrual cycle. The amount by which PAV amplified LG was quantified from the tidal volume amplification factor [(VtAF) assisted tidal volume/unassisted tidal volume]. LG was calculated as the inverse of the VtAF occurring at the assist level immediately preceding the emergence of periodic breathing (when LG x VtAF = 1). Only 1 of 10 men and 2 of 9 women developed periodic breathing with PAV. The rest were resistant to periodic breathing despite moderately high levels of PAV amplification. We conclude that LG is low in the majority of normal men and women and that higher volume amplification factors are needed to determine whether gender differences exist in this low range.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kiely, J Blanco; Olszanski, A; Both, S

Purpose: To develop a quantitative decision making metric for automatically detecting irregular breathing using a large patient population that received phase-sorted 4DCT. Methods: This study employed two patient cohorts. Cohort#1 contained 256 patients who received a phasesorted 4DCT. Cohort#2 contained 86 patients who received three weekly phase-sorted 4DCT scans. A previously published technique used a single abdominal surrogate to calculate the ratio of extreme inhalation tidal volume to normal inhalation tidal volume, referred to as the κ metric. Since a single surrogate is standard for phase-sorted 4DCT in radiation oncology clinical practice, tidal volume was not quantified. Without tidal volume,more » the absolute κ metric could not be determined, so a relative κ (κrel) metric was defined based on the measured surrogate amplitude instead of tidal volume. Receiver operator characteristic (ROC) curves were used to quantitatively determine the optimal cutoff value (jk) and efficiency cutoff value (τk) of κrel to automatically identify irregular breathing that would reduce the image quality of phase-sorted 4DCT. Discriminatory accuracy (area under the ROC curve) of κrel was calculated by a trapezoidal numeric integration technique. Results: The discriminatory accuracy of ?rel was found to be 0.746. The key values of jk and tk were calculated to be 1.45 and 1.72 respectively. For values of ?rel such that jk≤κrel≤τk, the decision to reacquire the 4DCT would be at the discretion of the physician. This accounted for only 11.9% of the patients in this study. The magnitude of κrel held consistent over 3 weeks for 73% of the patients in cohort#3. Conclusion: The decision making metric, ?rel, was shown to be an accurate classifier of irregular breathing patients in a large patient population. This work provided an automatic quantitative decision making metric to quickly and accurately assess the extent to which irregular breathing is occurring during phase-sorted 4DCT.« less

Relationship between clinical signs and pulmonary function estimated by the single breath diagram for CO(2) (SBD-CO(2)) in horses with chronic obstructive pulmonary disease.

PubMed

Herholz, C; Straub, R; Gerber, V; Wampfler, B; Lüthi, S; Imhof, A; Moens, Y; Busato, A

2002-03-01

The pulmonary health of 66 horses was assessed by a clinical examination and simple supplementary diagnostic methods. Single breath diagrams for CO(2) (SBD-CO(2)) and derived lung function indices were used to determine pulmonary function. The clinical signs in different groups were related to the results of the lung function indices derived from the SBD-CO(2). In horses with moderate to severe chronic obstructive pulmonary disease (COPD), a significant relationship was found between the respiratory frequency and the ratio of Bohr's dead space to the tidal volume (VD(Bohr)/VT), and between the physiological dead space/tidal volume ratio (VD(phys)/VT) and the ratio of the alveolar dead space to the alveolar tidal volume (VD(alv)/VT(alv)), but no significant associations were found between the arterial oxygen tension (P(a)O(2)) and lung function indices derived from the SBD-CO(2). The occurrence of cough, the viscosity of tracheobronchial mucus and the amount of polynuclear neutrophils in tracheobronchial aspirates were significantly related to the expiratory tidal volume (VT), the total expired volume of CO(2) (VCO(2)), VD(Bohr)/VT, VD(phys)/VT and VD(alv)/VT(alv). We conclude that abnormal findings in these clinical parameters indicate a measurable ventilation and perfusion (V(A)/Q) mismatch which is reflected by increases in dead space, VD(Bohr)/VT and VD(phys)/VT as well as VD(alv)/VT(alv). Copyright 2002 Elsevier Science Ltd. All rights reserved.

Mechanical ventilation management during extracorporeal membrane oxygenation for acute respiratory distress syndrome: a retrospective international multicenter study.

PubMed

Schmidt, Matthieu; Stewart, Claire; Bailey, Michael; Nieszkowska, Ania; Kelly, Joshua; Murphy, Lorna; Pilcher, David; Cooper, D James; Scheinkestel, Carlos; Pellegrino, Vincent; Forrest, Paul; Combes, Alain; Hodgson, Carol

2015-03-01

To describe mechanical ventilation settings in adult patients treated for an acute respiratory distress syndrome with extracorporeal membrane oxygenation and assess the potential impact of mechanical ventilation settings on ICU mortality. Retrospective observational study. Three international high-volume extracorporeal membrane oxygenation centers. A total of 168 patients treated with extracorporeal membrane oxygenation for severe acute respiratory distress syndrome from January 2007 to January 2013. We analyzed the association between mechanical ventilation settings (i.e. plateau pressure, tidal volume, and positive end-expiratory pressure) on ICU mortality using multivariable logistic regression model and Cox-proportional hazards model. We obtained detailed demographic, clinical, daily mechanical ventilation settings and ICU outcome data. One hundred sixty-eight patients (41 ± 14 years old; PaO2/FIO2 67 ± 19 mm Hg) fulfilled our inclusion criteria. Median duration of extracorporeal membrane oxygenation and ICU stay were 10 days (6-18 d) and 28 days (16-42 d), respectively. Lower positive end-expiratory pressure levels and significantly lower plateau pressures during extracorporeal membrane oxygenation were used in the French center than in both Australian centers (23.9 ± 1.4 vs 27.6 ± 3.7 and 27.8 ± 3.6; p < 0.0001). Overall ICU mortality was 29%. Lower positive end-expiratory pressure levels (until day 7) and lower delivered tidal volume after 3 days on extracorporeal membrane oxygenation were associated with significantly higher mortality (p < 0.05). In multivariate analysis, higher positive end-expiratory pressure levels during the first 3 days of extracorporeal membrane oxygenation support were associated with lower mortality (odds ratio, 0.75; 95% CI, 0.64-0.88; p = 0.0006). Other independent predictors of ICU mortality included time between ICU admission and extracorporeal membrane oxygenation initiation, plateau pressure greater than 30 cm H2O before extracorporeal membrane oxygenation initiation, and lactate level on day 3 of extracorporeal membrane oxygenation support. Protective mechanical ventilation strategies were routinely used in high-volume extracorporeal membrane oxygenation centers. However, higher positive end-expiratory pressure levels during the first 3 days on extracorporeal membrane oxygenation support were independently associated with improved survival. Further prospective trials on the optimal mechanical ventilation strategy during extracorporeal membrane oxygenation support are warranted.

Comparative Effects of Volutrauma and Atelectrauma on Lung Inflammation in Experimental Acute Respiratory Distress Syndrome

PubMed Central

Güldner, Andreas; Braune, Anja; Ball, Lorenzo; Silva, Pedro L.; Samary, Cynthia; Insorsi, Angelo; Huhle, Robert; Rentzsch, Ines; Becker, Claudia; Oehme, Liane; Andreeff, Michael; Vidal Melo, Marcos F.; Winkler, Tilo; Pelosi, Paolo; Rocco, Patricia R. M.; Kotzerke, Jörg; de Abreu, Marcelo Gama

2016-01-01

Objective Volutrauma and atelectrauma promote ventilator-induced lung injury, but their relative contribution to inflammation in ventilator-induced lung injury is not well established. The aim of this study was to determine the impact of volutrauma and atelectrauma on the distribution of lung inflammation in experimental acute respiratory distress syndrome. Design Laboratory investigation. Setting University-hospital research facility. Subjects Ten pigs (five per group; 34.7–49.9 kg) Interventions Animals were anesthetized and intubated, and saline lung lavage was performed. Lungs were separated with a double-lumen tube. Following lung recruitment and decremental positive end-expiratory pressure trial, animals were randomly assigned to 4 hours of ventilation of the left (ventilator-induced lung injury) lung with tidal volume of approximately 3 mL/kg and 1) high positive end-expiratory pressure set above the level where dynamic compliance increased more than 5% during positive end-expiratory pressure trial (volutrauma); or 2) low positive end-expiratory pressure to achieve driving pressure comparable with volutrauma (atelectrauma). The right (control) lung was kept on continuous positive airway pressure of 20 cm H2O, and Co2 was partially removed extracorporeally. Measurements and Main Results Regional lung aeration, specific [18F]fluorodeoxyglucose uptake rate, and perfusion were assessed using computed and positron emission tomography. Volutrauma yielded higher [18F]fluorodeoxyglucose uptake rate in the ventilated lung compared with atelectrauma (median [interquartile range], 0.017 [0.014–0.025] vs 0.013 min−1 [0.010–0.014min−1]; p < 0.01), mainly in central lung regions. Volutrauma yielded higher [18F]fluorodeoxyglucose uptake rate in ventilator-induced lung injury versus control lung (0.017 [0.014–0.025] vs 0.011 min−1 [0.010–0.016min−1]; p < 0.05), whereas atelectrauma did not. Volutrauma decreased blood fraction at similar perfusion and increased normally as well as hyper-aerated lung compartments and tidal hyperaeration. Atelectrauma yielded higher poorly and nonaerated lung compartments, and tidal recruitment. Driving pressure increased in atelectrauma. Conclusions In this model of acute respiratory distress syndrome, volutrauma promoted higher lung inflammation than atelectrauma at comparable low tidal volume and lower driving pressure, suggesting that static stress and strain are major determinants of ventilator-induced lung injury. PMID:27035236

Novel spirometry based on optical surface imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Guang, E-mail: lig2@mskcc.org; Huang, Hailiang; Li, Diana G.

2015-04-15

Purpose: To evaluate the feasibility of using optical surface imaging (OSI) to measure the dynamic tidal volume (TV) of the human torso during free breathing. Methods: We performed experiments to measure volume or volume change in geometric and deformable phantoms as well as human subjects using OSI. To assess the accuracy of OSI in volume determination, we performed experiments using five geometric phantoms and two deformable body phantoms and compared the values with those derived from geometric calculations and computed tomography (CT) measurements, respectively. To apply this technique to human subjects, an institutional review board protocol was established and threemore » healthy volunteers were studied. In the human experiment, a high-speed image capture mode of OSI was applied to acquire torso images at 4–5 frames per second, which was synchronized with conventional spirometric measurements at 5 Hz. An in-house MATLAB program was developed to interactively define the volume of interest (VOI), separate the thorax and abdomen, and automatically calculate the thoracic and abdominal volumes within the VOIs. The torso volume change (TV C = ΔV{sub torso} = ΔV{sub thorax} + ΔV{sub abdomen}) was automatically calculated using full-exhalation phase as the reference. The volumetric breathing pattern (BP{sub v} = ΔV{sub thorax}/ΔV{sub torso}) quantifying thoracic and abdominal volume variations was also calculated. Under quiet breathing, TVC should equal the tidal volume measured concurrently by a spirometer with a conversion factor (1.08) accounting for internal and external differences of temperature and moisture. Another MATLAB program was implemented to control the conventional spirometer that was used as the standard. Results: The volumes measured from the OSI imaging of geometric phantoms agreed with the calculated volumes with a discrepancy of 0.0% ± 1.6% (range −1.9% to 2.5%). In measurements from the deformable torso/thorax phantoms, the volume differences measured using OSI imaging and CT imaging were 1.2% ± 2.1% (range −0.5% to 3.6%), with a linear regression fitting (slope = 1.02 and R{sup 2} = 0.999). In volunteers, the relative error in OSI tidal volume measurement was −2.2% ± 4.9% (range −9.2% to 4.8%) and a correlation of r = 0.98 was found with spirometric measurement. The breathing pattern values of the three volunteers were substantially different from each other (BP{sub v} = 0.15, 0.45, and 0.32). Conclusions: This study demonstrates the feasibility of using OSI to measure breathing tidal volumes and breathing patterns with adequate accuracy. This is the first time that dynamic breathing tidal volume as well as breathing patterns is measured using optical surface imaging. The OSI-observed movement of the entire torso could serve as a new respiratory surrogate in the treatment room during radiation therapy.« less

Variable versus conventional lung protective mechanical ventilation during open abdominal surgery (PROVAR): a randomised controlled trial.

PubMed

Spieth, P M; Güldner, A; Uhlig, C; Bluth, T; Kiss, T; Conrad, C; Bischlager, K; Braune, A; Huhle, R; Insorsi, A; Tarantino, F; Ball, L; Schultz, M J; Abolmaali, N; Koch, T; Pelosi, P; Gama de Abreu, M

2018-03-01

Experimental studies showed that controlled variable ventilation (CVV) yielded better pulmonary function compared to non-variable ventilation (CNV) in injured lungs. We hypothesized that CVV improves intraoperative and postoperative respiratory function in patients undergoing open abdominal surgery. Fifty patients planned for open abdominal surgery lasting >3 h were randomly assigned to receive either CVV or CNV. Mean tidal volumes and PEEP were set at 8 ml kg -1 (predicted body weight) and 5 cm H 2 O, respectively. In CVV, tidal volumes varied randomly, following a normal distribution, on a breath-by-breath basis. The primary endpoint was the forced vital capacity (FVC) on postoperative Day 1. Secondary endpoints were oxygenation, non-aerated lung volume, distribution of ventilation, and pulmonary and extrapulmonary complications until postoperative Day 5. FVC did not differ significantly between CVV and CNV on postoperative Day 1, 61.5 (standard deviation 22.1) % vs 61.9 (23.6) %, respectively; mean [95% confidence interval (CI)] difference, -0.4 (-13.2-14.0), P=0.95. Intraoperatively, CVV did not result in improved respiratory function, haemodynamics, or redistribution of ventilation compared to CNV. Postoperatively, FVC, forced expiratory volume at the first second (FEV 1 ), and FEV 1 /FVC deteriorated, while atelectasis volume and plasma levels of interleukin-6 and interleukin-8 increased, but values did not differ between groups. The incidence of postoperative pulmonary and extrapulmonary complications was comparable in CVV and CNV. In patients undergoing open abdominal surgery, CVV did not improve intraoperative and postoperative respiratory function compared with CNV. NCT 01683578. Copyright © 2017 British Journal of Anaesthesia. Published by Elsevier Ltd. All rights reserved.

Temporal stability and coherence of anxiety, dyspnea, and physiological variables in panic disorder

PubMed Central

Burkhardt, Susan C. A.; Wilhelm, Frank H.; Meuret, Alicia E.; Blechert, Jens; Roth, Walton T.

2010-01-01

Twenty-five panic disorder (PD) patients, 19 social phobics (SP), and 20 healthy controls (HC) sat quietly for 15 minutes, rating their anxiety and dyspnea every 30 seconds while respiratory, cardiovascular, and electrodermal responses were recorded. No panic attacks were reported. For self-reported anxiety and dyspnea, within-subject variability over time was higher in PD than in SP or HC. In PD within-subject correlations across 30-second epochs were significant for (a) self-reported anxiety versus dyspnea, end-tidal pCO2, minute volume, duty cycle, skin conductance level, and interbeat interval, and for (b) dyspnea versus end-tidal pCO2, minute volume, tidal volume, and inspiratory flow rate. Several positive or negative correlations were greater in PD than in other groups. Thus in PD, experienced anxiety and dyspnea are temporally unstable but are correlated with each other and with fluctuations in respiratory and autonomic variables, even in the absence of panic attacks. PMID:20637257

Lung protective mechanical ventilation strategies in cardiothoracic critical care: a retrospective study.

PubMed

Zochios, Vasileios; Hague, Matthew; Giraud, Kimberly; Jones, Nicola

2016-01-01

A body of evidence supports the use of low tidal volumes in ventilated patients without lung pathology to slow progress to acute respiratory distress syndrome (ARDS) due to ventilator associated lung injury. We undertook a retrospective chart review and tested the hypothesis that tidal volume is a predictor of mortality in cardiothoracic (medical and surgical) critical care patients receiving invasive mechanical ventilation. Independent predictors of mortality in our study included: type of surgery, albumin, H + , bilirubin, and fluid balance. In particular, it is important to note that cardiac, thoracic, and transplant surgical patients were associated with lower mortality. However, our study did not sample equally from The Berlin Definition of ARDS severity categories (mild, moderate, and severe hypoxemia). Although our study was not adequately powered to detect a difference in mortality between these groups, it will inform the development of a large prospective cohort study exploring the role of low tidal volume ventilation in cardiothoracic critically ill patients.

Acute severe asthma: performance of ventilator at simulated altitude.

PubMed

Tourtier, Jean-Pierre; Forsans, Emma; Leclerc, Thomas; Libert, Nicolas; Ramsang, Solange; Tazarourte, Karim; Man, Michel; Borne, Marc

2011-04-01

Exacerbation of asthma can be seen during air transport. Severe patients, not responding to conventional therapy, require ventilator support. We evaluated the performance of two transport ventilators, built with turbine technology, the T-birdVSO2 and the LTV-1000, for use during aeromedical evacuation of acute severe asthma. We have assessed the ability of both the ventilators to deliver to an acute severe asthma model a tidal volume (Vt) set at different simulated altitudes, by changing the ambient air pressure. The simulated cabin altitudes were 1500, 2500, and 3000 m (decompression chamber). Vt was set at 700 and 400 ml in an acute severe asthma lung model. Comparisons of the preset with the actual measured values were accomplished using a t-test. Comparisons between the actual delivered Vt and set Vt showed a significant difference starting at 1500 m for both the ventilators. The T-birdVSO2 showed a decrease in the volume delivered, with a negative variation of more than 10% compared with the Vt set. The LTV-1000 showed mostly an increase in the volume delivered. The delivered Vt remained within 10% of the set Vt. The accuracy of Vt delivery was superior with the LTV-1000 than with the T-birdVSO2, but the higher delivered Vt of the LTV-1000 are likely to be more harmful than lower delivered Vt of the T-birdVSO2.

Quantification of the thorax-to-abdomen breathing ratio for breathing motion modeling.

PubMed

White, Benjamin M; Zhao, Tianyu; Lamb, James; Bradley, Jeffrey D; Low, Daniel A

2013-06-01

The purpose of this study was to develop a methodology to quantitatively measure the thorax-to-abdomen breathing ratio from a 4DCT dataset for breathing motion modeling and breathing motion studies. The thorax-to-abdomen breathing ratio was quantified by measuring the rate of cross-sectional volume increase throughout the thorax and abdomen as a function of tidal volume. Twenty-six 16-slice 4DCT patient datasets were acquired during quiet respiration using a protocol that acquired 25 ciné scans at each couch position. Fifteen datasets included data from the neck through the pelvis. Tidal volume, measured using a spirometer and abdominal pneumatic bellows, was used as breathing-cycle surrogates. The cross-sectional volume encompassed by the skin contour when compared for each CT slice against the tidal volume exhibited a nearly linear relationship. A robust iteratively reweighted least squares regression analysis was used to determine η(i), defined as the amount of cross-sectional volume expansion at each slice i per unit tidal volume. The sum Ση(i) throughout all slices was predicted to be the ratio of the geometric expansion of the lung and the tidal volume; 1.11. The Xiphoid process was selected as the boundary between the thorax and abdomen. The Xiphoid process slice was identified in a scan acquired at mid-inhalation. The imaging protocol had not originally been designed for purposes of measuring the thorax-to-abdomen breathing ratio so the scans did not extend to the anatomy with η(i) = 0. Extrapolation of η(i)-η(i) = 0 was used to include the entire breathing volume. The thorax and abdomen regions were individually analyzed to determine the thorax-to-abdomen breathing ratios. There were 11 image datasets that had been scanned only through the thorax. For these cases, the abdomen breathing component was equal to 1.11 - Ση(i) where the sum was taken throughout the thorax. The average Ση(i) for thorax and abdomen image datasets was found to be 1.20 ± 0.17, close to the expected value of 1.11. The thorax-to-abdomen breathing ratio was 0.32 ± 0.24. The average Ση(i) was 0.26 ± 0.14 in the thorax and 0.93 ± 0.22 in the abdomen. In the scan datasets that encompassed only the thorax, the average Ση(i) was 0.21 ± 0.11. A method to quantify the relationship between abdomen and thoracic breathing was developed and characterized.

The effect of respiratory motion on pulmonary nodule location during electromagnetic navigation bronchoscopy.

PubMed

Chen, Alexander; Pastis, Nicholas; Furukawa, Brian; Silvestri, Gerard A

2015-05-01

Electromagnetic navigation has improved the diagnostic yield of peripheral bronchoscopy for pulmonary nodules. For these procedures, a thin-slice chest CT scan is performed prior to bronchoscopy at full inspiration and is used to create virtual airway reconstructions that are used as a map during bronchoscopy. Movement of the lung occurs with respiratory variation during bronchoscopy, and the location of pulmonary nodules during procedures may differ significantly from their location on the initial planning full-inspiratory chest CT scan. This study was performed to quantify pulmonary nodule movement from full inspiration to end-exhalation during tidal volume breathing in patients undergoing electromagnetic navigation procedures. A retrospective review of electromagnetic navigation procedures was performed for which two preprocedure CT scans were performed prior to bronchoscopy. One CT scan was performed at full inspiration, and a second CT scan was performed at end-exhalation during tidal volume breathing. Pulmonary lesions were identified on both CT scans, and distances between positions were recorded. Eighty-five pulmonary lesions were identified in 46 patients. Average motion of all pulmonary lesions was 17.6 mm. Pulmonary lesions located in the lower lobes moved significantly more than upper lobe nodules. Size and distance from the pleura did not significantly impact movement. Significant movement of pulmonary lesions occurs between full inspiration and end-exhalation during tidal volume breathing. This movement from full inspiration on planning chest CT scan to tidal volume breathing during bronchoscopy may significantly affect the diagnostic yield of electromagnetic navigation bronchoscopy procedures.

Design and Evaluation of an Intelligent Remote Tidal Volume Variability Monitoring System in E-Health Applications.

PubMed

Fekr, Atena Roshan; Radecka, Katarzyna; Zilic, Zeljko

2015-09-01

A reliable long-term monitoring and diagnosis of breath disorders at an early stage provides an improvement of medical act, life expectancy, and quality of life while decreasing the costs of treatment and medical services. Therefore, a real-time unobtrusive monitoring of respiration patterns, as well as breath parameters, is a critical need in medical applications. In this paper, we propose an intelligent system for patient home care, capable of measuring respiration rate and tidal volume variability via a wearable sensing technology. The proposed system is designed particularly for the goal of diagnosis and treatment in patients with pathological breathing, e.g., respiratory complications after surgery or sleep disorders. The complete system was comprised of wearable calibrated accelerometer sensor, Bluetooth low energy, and cloud database. The experiments are conducted with eight subjects and the overall error in respiration rate calculation is obtained 0.29%±0.33% considering SPR-BTA spirometer as the reference. We also introduce a method for tidal volume variability estimation while validated using Pearson correlation. Furthermore, since it is essential to detect the critical events resulted from sudden rise or fall in per breath tidal volume of the patients, we provide a technique to automatically find the accurate threshold values based on each individual breath characteristics. Therefore, the system is able to detect the major changes, precisely by more than 98%, and provide immediate feedback such as sound alarm for round-the-clock respiration monitoring.

Ventilatory accommodation of oxygen demand and respiratory water loss in kangaroos from mesic and arid environments, the eastern grey kangaroo (Macropus giganteus) and the red kangaroo (Macropus rufus).

PubMed

Dawson, T J; Munn, A J; Blaney, C E; Krockenberger, A; Maloney, S K

2000-01-01

We studied ventilation in kangaroos from mesic and arid environments, the eastern grey kangaroo (Macropus giganteus) and the red kangaroo (Macropus rufus), respectively, within the range of ambient temperatures (T(a)) from -5 degrees to 45 degrees C. At thermoneutral temperatures (Ta=25 degrees C), there were no differences between the species in respiratory frequency, tidal volume, total ventilation, or oxygen extraction. The ventilatory patterns of the kangaroos were markedly different from those predicted from the allometric equation derived for placentals. The kangaroos had low respiratory frequencies and higher tidal volumes, even when adjustment was made for their lower basal metabolism. At Ta>25 degrees C, ventilation was increased in the kangaroos to facilitate respiratory water loss, with percent oxygen extraction being markedly lowered. Ventilation was via the nares; the mouth was closed. Differences in ventilation between the two species occurred at higher temperatures, and at 45 degrees C were associated with differences in respiratory evaporative heat loss, with that of M. giganteus being higher. Panting in kangaroos occurred as a graded increase in respiratory frequency, during which tidal volume was lowered. When panting, the desert red kangaroo had larger tidal volumes and lower respiratory frequencies at equivalent T(a) than the eastern grey kangaroo, which generally inhabits mesic forests. The inference made from this pattern is that the red kangaroo has the potential to increase respiratory evaporative heat loss to a greater level.

Assessment of Factors Related to Auto-PEEP.

PubMed

Natalini, Giuseppe; Tuzzo, Daniele; Rosano, Antonio; Testa, Marco; Grazioli, Michele; Pennestrì, Vincenzo; Amodeo, Guido; Marsilia, Paolo F; Tinnirello, Andrea; Berruto, Francesco; Fiorillo, Marialinda; Filippini, Matteo; Peratoner, Alberto; Minelli, Cosetta; Bernardini, Achille

2016-02-01

Previous physiological studies have identified factors that are involved in auto-PEEP generation. In our study, we examined how much auto-PEEP is generated from factors that are involved in its development. One hundred eighty-six subjects undergoing controlled mechanical ventilation with persistent expiratory flow at the beginning of each inspiration were enrolled in the study. Volume-controlled continuous mandatory ventilation with PEEP of 0 cm H2O was applied while maintaining the ventilator setting as chosen by the attending physician. End-expiratory and end-inspiratory airway occlusion maneuvers were performed to calculate respiratory mechanics, and tidal flow limitation was assessed by a maneuver of manual compression of the abdomen. The variable with the strongest effect on auto-PEEP was flow limitation, which was associated with an increase of 2.4 cm H2O in auto-PEEP values. Moreover, auto-PEEP values were directly related to resistance of the respiratory system and body mass index and inversely related to expiratory time/time constant. Variables that were associated with the breathing pattern (tidal volume, frequency minute ventilation, and expiratory time) did not show any relationship with auto-PEEP values. The risk of auto-PEEP ≥5 cm H2O was increased by flow limitation (adjusted odds ratio 17; 95% CI: 6-56.2), expiratory time/time constant ratio <1.85 (12.6; 4.7-39.6), respiratory system resistance >15 cm H2O/L s (3; 1.3-6.9), age >65 y (2.8; 1.2-6.5), and body mass index >26 kg/m(2) (2.6; 1.1-6.1). Flow limitation, expiratory time/time constant, resistance of the respiratory system, and obesity are the most important variables that affect auto-PEEP values. Frequency expiratory time, tidal volume, and minute ventilation were not independently associated with auto-PEEP. Therapeutic strategies aimed at reducing auto-PEEP and its adverse effects should be primarily oriented to the variables that mainly affect auto-PEEP values. Copyright © 2016 by Daedalus Enterprises.

Modeling In-stream Tidal Energy Extraction and Its Potential Environmental Impacts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Zhaoqing; Wang, Taiping; Copping, Andrea

In recent years, there has been growing interest in harnessing in-stream tidal energy in response to concerns of increasing energy demand and to mitigate climate change impacts. While many studies have been conducted to assess and map tidal energy resources, efforts for quantifying the associated potential environmental impacts have been limited. This paper presents the development of a tidal turbine module within a three-dimensional unstructured-grid coastal ocean model and its application for assessing the potential environmental impacts associated with tidal energy extraction. The model is used to investigate in-stream tidal energy extraction and associated impacts on estuarine hydrodynamic and biologicalmore » processes in a tidally dominant estuary. A series of numerical experiments with varying numbers and configurations of turbines installed in an idealized estuary were carried out to assess the changes in the hydrodynamics and biological processes due to tidal energy extraction. Model results indicated that a large number of turbines are required to extract the maximum tidal energy and cause significant reduction of the volume flux. Preliminary model results also indicate that extraction of tidal energy increases vertical mixing and decreases flushing rate in a stratified estuary. The tidal turbine model was applied to simulate tidal energy extraction in Puget Sound, a large fjord-like estuary in the Pacific Northwest coast.« less

Assessment of volume and leak measurements during CPAP using a neonatal lung model.

PubMed

Fischer, H S; Roehr, C C; Proquitté, H; Wauer, R R; Schmalisch, G

2008-01-01

Although several commercial devices are available which allow tidal volume and air leak monitoring during continuous positive airway pressure (CPAP) in neonates, little is known about their measurement accuracy and about the influence of air leaks on volume measurement. The aim of this in vitro study was the validation of volume and leak measurement under CPAP using a commercial ventilatory device, taking into consideration the clinical conditions in neonatology. The measurement accuracy of the Leoni ventilator (Heinen & Löwenstein, Germany) was investigated both in a leak-free system and with leaks simulated using calibration syringes (2-10 ml, 20-100 ml) and a mechanical lung model. Open tubes of variable lengths were connected for leak simulation. Leak flow was measured with the flow-through technique. In a leak-free system the mean relative volume error +/-SD was 3.5 +/- 2.6% (2-10 ml) and 5.9 +/- 0.7% (20-60 ml), respectively. The influence of CPAP level, driving flow, respiratory rate and humidification of the breathing gas on the volume error was negligible. However, an increasing F(i)O(2) caused the measured tidal volume to increase by up to 25% (F(i)O(2) = 1.0). The relative error +/- SD of the leak measurements was -0.2 +/- 11.9%. For leaks > 19%, measured tidal volume was underestimated by more than 10%. In conclusion, the present in vitro study showed that the Leoni allowed accurate volume monitoring under CPAP conditions similar to neonates. Air leaks of up to 90% of patient flow were reliably detected. For an F(i)O(2) > 0.4 and for leaks > 19%, a numerical correction of the displayed volume should be performed.

Tidal residual current and its role in the mean flow on the Changjiang Bank

NASA Astrophysics Data System (ADS)

Xuan, Jiliang; Yang, Zhaoqing; Huang, Daji; Wang, Taiping; Zhou, Feng

2016-02-01

The tidal residual current may play an important role in the mean flow in the Changjiang Bank region, in addition to other residual currents, such as the Taiwan Warm Current, the Yellow Sea Coastal Current, and the Yellow Sea Warm Current. In this paper, a detailed structure of the tidal residual current, in particular the meso-scale eddies, in the Changjiang Bank region is observed from model simulations, and its role in the mean flow is quantified using the well-validated Finite Volume Coastal Ocean Model. The tidal residual current in the Changjiang Bank region consists of two components: an anticyclonic regional-scale tidal residual circulation around the edge of the Changjiang Bank and some cyclonic meso-scale tidal residual eddies across the Changjiang Bank. The meso-scale tidal residual eddies occur across the Changjiang Bank and contribute to the regional-scale tidal residual circulation offshore at the northwest boundary and on the northeast edge of the Changjiang Bank, southeastward along the 50 m isobath. Tidal rectification is the major mechanism causing the tidal residual current to flow along the isobaths. Both components of the tidal residual current have significant effects on the mean flow. A comparison between the tidal residual current and the mean flow indicates that the contribution of the tidal residual current to the mean flow is greater than 50%.

Positive end-expiratory pressure at minimal respiratory elastance represents the best compromise between mechanical stress and lung aeration in oleic acid induced lung injury.

PubMed

Carvalho, Alysson Roncally S; Jandre, Frederico C; Pino, Alexandre V; Bozza, Fernando A; Salluh, Jorge; Rodrigues, Rosana; Ascoli, Fabio O; Giannella-Neto, Antonio

2007-01-01

Protective ventilatory strategies have been applied to prevent ventilator-induced lung injury in patients with acute lung injury (ALI). However, adjustment of positive end-expiratory pressure (PEEP) to avoid alveolar de-recruitment and hyperinflation remains difficult. An alternative is to set the PEEP based on minimizing respiratory system elastance (Ers) by titrating PEEP. In the present study we evaluate the distribution of lung aeration (assessed using computed tomography scanning) and the behaviour of Ers in a porcine model of ALI, during a descending PEEP titration manoeuvre with a protective low tidal volume. PEEP titration (from 26 to 0 cmH2O, with a tidal volume of 6 to 7 ml/kg) was performed, following a recruitment manoeuvre. At each PEEP, helical computed tomography scans of juxta-diaphragmatic parts of the lower lobes were obtained during end-expiratory and end-inspiratory pauses in six piglets with ALI induced by oleic acid. The distribution of the lung compartments (hyperinflated, normally aerated, poorly aerated and non-aerated areas) was determined and the Ers was estimated on a breath-by-breath basis from the equation of motion of the respiratory system using the least-squares method. Progressive reduction in PEEP from 26 cmH2O to the PEEP at which the minimum Ers was observed improved poorly aerated areas, with a proportional reduction in hyperinflated areas. Also, the distribution of normally aerated areas remained steady over this interval, with no changes in non-aerated areas. The PEEP at which minimal Ers occurred corresponded to the greatest amount of normally aerated areas, with lesser hyperinflated, and poorly and non-aerated areas. Levels of PEEP below that at which minimal Ers was observed increased poorly and non-aerated areas, with concomitant reductions in normally inflated and hyperinflated areas. The PEEP at which minimal Ers occurred, obtained by descending PEEP titration with a protective low tidal volume, corresponded to the greatest amount of normally aerated areas, with lesser collapsed and hyperinflated areas. The institution of high levels of PEEP reduced poorly aerated areas but enlarged hyperinflated ones. Reduction in PEEP consistently enhanced poorly or non-aerated areas as well as tidal re-aeration. Hence, monitoring respiratory mechanics during a PEEP titration procedure may be a useful adjunct to optimize lung aeration.

A numerical study of the barotropic tides and tidal energy distribution in the Indonesian seas with the assimilated finite volume coastal ocean model

NASA Astrophysics Data System (ADS)

Ding, Yang; Bao, Xianwen; Yu, Huaming; Kuang, Liang

2012-04-01

The tides and tidal energetics in the Indonesian seas are simulated using a three-dimensional finite volume coastal ocean model. The high-resolution coastline-fitted model is configured to better resolve the hydrodynamic processes around the numerous barrier islands. A large model domain is adopted to minimize the uncertainty adjacent to open boundaries. The model results with elevation assimilation based on a simple nudge scheme faithfully reproduced the general features of the barotropic tides in the Indonesian Seas. The mean root-mean-square errors between the observed and simulated tidal constants are 2.3, 1.1, 2.4, and 1.5 cm for M2, S2, K1, and O1, respectively. Analysis of the model solutions indicates that the semidiurnal tides in the Indonesian Seas are primarily dominated by the Indian Ocean, whereas the diurnal tides in this region are mainly influenced by the Pacific Ocean, which is consistent with previous studies. Examinations of tidal energy transport reveal that the tidal energy for both of the simulated tidal constituents are transported from the Indian Ocean into the IS mainly through the Lombok Strait and the Timor Sea, whereas only M2 energy enters the Banda Sea and continues northward. The tidal energy dissipates the most in the passages on both sides of Timor Island, with the maximum M2 and K1 tidal energy transport reaching about 750 and 650 kW m-1, respectively. The total energy losses of the four dominant constituents in the IS are nearly 338 GW, with the M2 constituent dissipating 240.8 GW. It is also shown that the bottom dissipation rate for the M2 tide is about 1-2 order of magnitudes larger than that of the other three tidal components in the Indonesian seas.

Large-scale tidal effect on redshift-space power spectrum in a finite-volume survey

NASA Astrophysics Data System (ADS)

Akitsu, Kazuyuki; Takada, Masahiro; Li, Yin

2017-04-01

Long-wavelength matter inhomogeneities contain cleaner information on the nature of primordial perturbations as well as the physics of the early Universe. The large-scale coherent overdensity and tidal force, not directly observable for a finite-volume galaxy survey, are both related to the Hessian of large-scale gravitational potential and therefore are of equal importance. We show that the coherent tidal force causes a homogeneous anisotropic distortion of the observed distribution of galaxies in all three directions, perpendicular and parallel to the line-of-sight direction. This effect mimics the redshift-space distortion signal of galaxy peculiar velocities, as well as a distortion by the Alcock-Paczynski effect. We quantify its impact on the redshift-space power spectrum to the leading order, and discuss its importance for ongoing and upcoming galaxy surveys.

Association between ventilatory settings and development of acute respiratory distress syndrome in mechanically ventilated patients due to brain injury.

PubMed

Tejerina, Eva; Pelosi, Paolo; Muriel, Alfonso; Peñuelas, Oscar; Sutherasan, Yuda; Frutos-Vivar, Fernando; Nin, Nicolás; Davies, Andrew R; Rios, Fernando; Violi, Damian A; Raymondos, Konstantinos; Hurtado, Javier; González, Marco; Du, Bin; Amin, Pravin; Maggiore, Salvatore M; Thille, Arnaud W; Soares, Marco Antonio; Jibaja, Manuel; Villagomez, Asisclo J; Kuiper, Michael A; Koh, Younsuck; Moreno, Rui P; Zeggwagh, Amine Ali; Matamis, Dimitrios; Anzueto, Antonio; Ferguson, Niall D; Esteban, Andrés

2017-04-01

In neurologically critically ill patients with mechanical ventilation (MV), the development of acute respiratory distress syndrome (ARDS) is a major contributor to morbidity and mortality, but the role of ventilatory management has been scarcely evaluated. We evaluate the association of tidal volume, level of PEEP and driving pressure with the development of ARDS in a population of patients with brain injury. We performed a secondary analysis of a prospective, observational study on mechanical ventilation. We included 986 patients mechanically ventilated due to an acute brain injury (hemorrhagic stroke, ischemic stroke or brain trauma). Incidence of ARDS in this cohort was 3%. Multivariate analysis suggested that driving pressure could be associated with the development of ARDS (odds ratio for unit increment of driving pressure 1.12; confidence interval for 95%: 1.01 to 1.23) whereas we did not observe association for tidal volume (in ml per kg of predicted body weight) or level of PEEP. ARDS was associated with an increase in mortality, longer duration of mechanical ventilation, and longer ICU length of stay. In a cohort of brain-injured patients the development of ARDS was not common. Driving pressure was associated with the development of this disease. Copyright © 2016 Elsevier Inc. All rights reserved.

Cardiopulmonary resuscitation using the cardio vent device in a resuscitation model.

PubMed

Suner, Selim; Jay, Gregory D; Kleinman, Gary J; Woolard, Robert H; Jagminas, Liudvikas; Becker, Bruce M

2002-05-01

To compare the "Bellows on Sternum Resuscitation" (BSR) device that permits simultaneous compression and ventilation by one rescuer with two person cardiopulmonary resuscitation (CPR) with bag-valve-mask (BVM) ventilation in a single blind crossover study performed in the laboratory setting. Tidal volume and compression depth were recorded continuously during 12-min CPR sessions with the BSR device and two person CPR. Six CPR instructors performed a total of 1,894 ventilations and 10,532 compressions in 3 separate 12-min sessions. Mean tidal volume (MTV) and compression rate (CR) with the BSR device differed significantly from CPR with the BVM group (1242 mL vs. 1065 mL, respectively, p = 0.0018 and 63.2 compressions per minute (cpm) vs. 81.3 cpm, respectively, p = 0.0076). Error in compression depth (ECD) rate of 9.78% was observed with the BSR device compared to 8.49% with BMV CPR (p = 0.1815). Error rate was significantly greater during the second half of CPR sessions for both BSR and BVM groups. It is concluded that one-person CPR with the BSR device is equivalent to two-person CPR with BVM in all measured parameters except for CR. Both groups exhibited greater error rate in CPR performance in the latter half of 12-min CPR sessions.

The impacts of land reclamation on suspended-sediment dynamics in Jiaozhou Bay, Qingdao, China

NASA Astrophysics Data System (ADS)

Gao, Guan Dong; Wang, Xiao Hua; Bao, Xian Wen; Song, Dehai; Lin, Xiao Pei; Qiao, Lu Lu

2018-06-01

A three-dimensional, high-resolution tidal model coupled with the UNSW sediment model (UNSW-Sed) based on Finite Volume Coastal Ocean Model (FVCOM) was set up to study the suspended-sediment dynamics and its change in Jiaozhou Bay (JZB) due to land reclamation over the period 1935 to 2008. During the past decades, a large amount of tidal flats were lost due to land reclamation. Other than modulating the tides, the tidal flats are a primary source for sediment resuspensions, leading to turbidity maxima nearshore. The tidal dynamics are dominant in controlling the suspended-sediment dynamics in JZB and have experienced significant changes with the loss of tidal flats due to the land reclamation. The sediment model coupled with the tide model was used to investigate the changes in suspended-sediment dynamics due to the land reclamation from 1935 to 2008, including suspended-sediment concentrations (SSC) and the horizontal suspended-sediment fluxes. This model can predict the general patterns of the spatial and temporal variation of SSC. The model was applied to investigate how the net transport of suspended sediments between JZB and its adjacent sea areas changed with land reclamation: in 1935 the net movement of suspended sediments was from JZB to the adjacent sea (erosion for JZB), primarily caused by horizontal advection associated with a horizontal gradient in the SSC; This seaward transport (erosion for JZB) had gradually declined from 1935 to 2008. If land reclamation on a large scale is continued in future, the net transport between JZB and the adjacent sea would turn landward and JZB would switch from erosion to siltation due to the impact of land reclamation on the horizontal advection of suspended sediments. We also evaluate the primary physical mechanisms including advection of suspended sediments, settling lag and tidal asymmetry, which control the suspended-sediment dynamics with the process of land reclamation.

A numerical model for the whole Wadden Sea: results on the hydrodynamics

NASA Astrophysics Data System (ADS)

Gräwe, Ulf; Duran-Matute, Matias; Gerkema, Theo; Flöser, Götz; Burchard, Hans

2015-04-01

A high-resolution baroclinic three-dimensional numerical model for the entire Wadden Sea of the German Bight in the southern North Sea is first validated against field data for surface elevation, current velocity, temperature and salinity at selected stations and then used to calculate fluxes of volume, heat and salt inside the Wadden Sea and the exchange between the Wadden Sea and the adjacent North Sea through the major tidal inlets. The General Estuarine Transport Model (GETM) is simulating the reference years 2009-2011. The numerical grid has a resolution of 200x200m and 30 adaptive vertical layers. It is the final stage of a multi-nested setup, starting from the North Atlantic. The atmospheric forcing is taken from the operational forecast of the German Weather Service. Additionally, the freshwater discharge of 23 local rivers and creeks are included. For validation, we use observations from a ship of opportunity measuring sea surface properties, tidal gauge stations, high frequency of salinity and volume transport estimates for the Mardiep and Spiekeroog inlet. Finally, the estuarine overturning circulation in three tidal gulleys is quantified. Regional differences between the gullies are assessed and drivers of the estuarine circulation are identified. Moreover, we will give a consistent estimate of the tidal prisms for all tidal inlets in the entire Wadden Sea.

Initial mechanical ventilator settings and lung protective ventilation in the ED.

PubMed

Wilcox, Susan R; Richards, Jeremy B; Fisher, Daniel F; Sankoff, Jeffrey; Seigel, Todd A

2016-08-01

Mechanical ventilation with low tidal volumes has been shown to improve outcomes for patients both with and without acute respiratory distress syndrome. This study aims to characterize mechanically ventilated patients in the emergency department (ED), describe the initial ED ventilator settings, and assess for associations between lung protective ventilation strategies in the ED and outcomes. This was a multicenter, prospective, observational study of mechanical ventilation at 3 academic EDs. We defined lung protective ventilation as a tidal volume of less than or equal to 8 mL/kg of predicted body weight and compared outcomes for patients ventilated with lung protective vs non-lung protective ventilation, including inhospital mortality, ventilator days, intensive care unit length of stay, and hospital length of stay. Data from 433 patients were analyzed. Altered mental status without respiratory pathology was the most common reason for intubation, followed by trauma and respiratory failure. Two hundred sixty-one patients (60.3%) received lung protective ventilation, but most patients were ventilated with a low positive end-expiratory pressure, high fraction of inspired oxygen strategy. Patients were ventilated in the ED for a mean of 5 hours and 7 minutes but had few ventilator adjustments. Outcomes were not significantly different between patients receiving lung protective vs non-lung protective ventilation. Nearly 40% of ED patients were ventilated with non-lung protective ventilation as well as with low positive end-expiratory pressure and high fraction of inspired oxygen. Despite a mean ED ventilation time of more than 5 hours, few patients had adjustments made to their ventilators. Copyright © 2016 Elsevier Inc. All rights reserved.

Tidal residual current and its role in the mean flow on the Changjiang Bank

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xuan, Jiliang; Yang, Zhaoqing; Huang, Daji

Tidal residual current may play an important role in the mean flow in the Changjiang Bank region, in addition to other residual currents, such as the Taiwan Warm Current, the Yellow Sea Coastal Current, and the Yellow Sea Warm Current. In this paper, a detailed structure of the tidal residual current, in particular the meso-scale eddies, in the Changjiang Bank region is observed from model simulations, and its role in the mean flow is quantified using the well-validated Finite Volume Coastal Ocean Model). The tidal residual current in the Changjiang Bank region consists of two components: an anticyclonic regional-scale tidalmore » residual circulation around the edge of the Changjiang Bank and some cyclonic meso-scale tidal residual eddies across the Changjiang Bank. The meso-scale tidal residual eddies occur across the Changjiang Bank and contribute to the regional-scale tidal residual circulation offshore at the northwest boundary and at the northeast edge of the Changjiang Bank, southeastward along the 50 m isobath. Tidal rectification is the major mechanism causing the tidal residual current to flow along the isobaths. Both components of the tidal residual current have significant effects on the mean flow. A comparison between the tidal residual current and the mean flow indicates that the contribution of the tidal residual current to the mean flow is greater than 50%.« less

Predictors of outcome of prematurely born infants with pulmonary interstitial emphysema.

PubMed

Williams, Emma; Dassios, Theodore; Clarke, Paul; Chowdhury, Olie; Greenough, Anne

2018-05-13

To determine how oxygenation, ventilation efficiency and tidal volume requirements changed with the development of pulmonary interstitial emphysema (PIE) and whether in affected patients a composite gas exchange index predicted death or bronchopulmonary dysplasia (BPD). Infants who developed PIE from 2010 to 2016 were identified. The oxygenation index, ventilation efficiency index, ventilation to perfusion ratio and inspiratory tidal volume were calculated before radiological evidence of PIE (pre-PIE) and at the worst PIE radiographic appearance (PIE-worst). Thirty infants, median (IQR) gestational age of 24.6 (24.3-26.7) weeks were assessed. Their age at pre-PIE was 11(6-19) days and 23 (13-42) days at PIE-worst. Compared to pre-PIE, at PIE-worst, the oxygenation index was higher [14.5 (10.7-19.2) versus 4.8 (3.1-6.1) respectively, p<0.001], ventilation efficiency index was lower [0.01 (0.01-0.11) versus 0.16 (0.13-0.19) respectively, p<0.001], ventilation to perfusion ratio was lower [0.15 (0.11-0.40) versus 0.26 (0.20-0.37), p=0.033] and tidal volume was higher [9.9 (7.2-13.1) versus 6.4 (5.5-6.8) ml/kg, p=0.007]. An oxygenation index >11.4 at PIE-worst predicted death or BPD with 80% sensitivity and 100% specificity. Development of PIE was associated with poorer oxygenation and ventilation efficiency despite increased tidal volumes. The oxygenation index at PIE-worst predicted death or BPD. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

21 CFR 868.1850 - Monitoring spirometer.

Code of Federal Regulations, 2011 CFR

2011-04-01

... of gas inhaled by the patient during each respiration cycle) or minute volume (the tidal volume multiplied by the rate of respiration for 1 minute) for the evaluation of the patient's ventilatory status...

21 CFR 868.1850 - Monitoring spirometer.

Code of Federal Regulations, 2010 CFR

2010-04-01

... of gas inhaled by the patient during each respiration cycle) or minute volume (the tidal volume multiplied by the rate of respiration for 1 minute) for the evaluation of the patient's ventilatory status...

A Review of Indicators of Estuarine Tidal Wetland Condition

EPA Science Inventory

This review critically evaluates indicators of tidal wetland condition based on 36 indicator development studies and indicators developed as part of U.S. state tidal wetland monitoring programs. Individual metrics were evaluated based on relative scores on two sets of evaluation ...

Influence of breathing resistance of heat and moisture exchangers on tracheal climate and breathing pattern in laryngectomized individuals.

PubMed

Scheenstra, Renske J; Muller, Sara H; Vincent, Andrew; Sinaasappel, Michiel; Hilgers, Frans J M

2010-08-01

The aim of this study was to determine the influence of breathing resistance of heat and moisture exchangers (HMEs) on endotracheal climate and breathing pattern. Endotracheal temperature and humidity and tidal volumes were measured in 11 laryngectomized patients with a regularly used HME with "standard" breathing resistance (Provox Normal HME; R-HME), a low breathing-resistance HME (Provox HiFlow HME; L-HME), and without HME. Both R-HME and L-HME increased end-inspiratory humidity (+5.8 and 4.7 mgH(2)O/L, respectively), decreased end-inspiratory temperature (-1.6 and -1.0 degrees C, respectively), and prolonged the exhalation breath length to approximately 0.5 seconds. The R-HME significantly enlarged tidal volumes (0.07 L; p < .05). Both HMEs significantly improve tracheal climate. The R-HME has better moistening properties and a small but significant positive effect on tidal volume. Therefore, if the higher resistance is tolerated, the R-HME is the preferred pulmonary rehabilitation device. The L-HME is indicated if lower breathing resistance is required. 2009 Wiley Periodicals, Inc. Head Neck, 2010.

Investigating parameters participating in the infant respiratory control system attractor.

PubMed

Terrill, Philip I; Wilson, Stephen J; Suresh, Sadasivam; Cooper, David M; Dakin, Carolyn

2008-01-01

Theoretically, any participating parameter in a non-linear system represents the dynamics of the whole system. Taken's time delay embedding theory provides the fundamental basis for allowing non-linear analysis to be performed on physiological, time-series data. In practice, only one measurable parameter is required to be measured to convey an accurate representation of the system dynamics. In this paper, the infant respiratory control system is represented using three variables-a digitally sampled respiratory inductive plethysmography waveform, and the derived parameters tidal volume and inter-breath interval time series data. For 14 healthy infants, these data streams were analysed using recurrence plot analysis across one night of sleep. The measured attractor size of these variables followed the same qualitative trends across the nights study. Results suggest that the attractor size measures of the derived IBI and tidal volume are representative surrogates for the raw respiratory waveform. The extent to which the relative attractor sizes of IBI and tidal volume remain constant through changing sleep state could potentially be used to quantify pathology, or maturation of breathing control.

A system shift in tidal choking due to the construction of Yangshan Harbour, Shanghai, China

NASA Astrophysics Data System (ADS)

Guo, Wenyun; Wang, Xiao Hua; Ding, Pingxing; Ge, Jianzhong; Song, Dehai

2018-06-01

Tidal choking is a geometric feature caused by a narrowed channel. Construction of the Yangshan Harbour, Shanghai, China obstructed three key channels and intensively changed the local geometry and topography. In this study nine numerical experiments based on the Finite-Volume Community Ocean Model are conducted to study the project's influence on tidal characteristics. Results show that stronger tidal choking happened at the East Entrance after project, mainly due to the jet induced water-level drop forced by Bernoulli law and the longer and narrower geometry. The stronger tidal choking forces a faster flow and larger tidal energy flux at the choked channel while reducing the tidal amplitude in the Inner Harbour Area (IHA). The scouring on this channel reduces the choking effect but further enlarges tidal energy flux. Moreover, damming the channels decrease the tidal amplitude at the lee side of tidal propagating direction while increasing the amplitude on the stoss side. The dams also decrease the tidal current on both sides, and meanwhile develop two patches with stronger current aside the dam. The project induced changes in tidal characteristics are complex in space, and perturbations in bathymetry increase this complexity. Yangshan Harbour's construction induces little changes in the total tidal energy density in the IHA, but induces obvious changes in the spatial distribution of tidal energy. Although this study is site-specific, the findings may be applicable to tidal dynamics in land reclamation close to open seas, such as the dramatic reclamation of islands in the South China Sea.

Tidal volume single-breath washin of SF6 and CH4 in transient microgravity

NASA Technical Reports Server (NTRS)

Dutrieue, Brigitte; Paiva, Manuel; Verbanck, Sylvia; Le Gouic, Marine; Darquenne, Chantal; Prisk, G. Kim

2003-01-01

We performed tidal volume single-breath washins (SBW) by using tracers of different diffusivity and varied the time spent in microgravity (microG) before the start of the tests to look for time-dependent effects. SF(6) and CH(4) phase III slopes decreased by 35 and 26%, respectively, in microG compared with 1 G (P < 0.05), and the slope difference between gases disappeared. There was no effect of time in microG, suggesting that neither the hypergravity period preceding microG nor the time spent in microG affected gas mixing at volumes near functional residual capacity. In previous studies using SF(6) and He (Lauzon A-M, Prisk GK, Elliott AR, Verbanck S, Paiva M, and West JB. J Appl Physiol 82: 859-865, 1997), the vital capacity SBW showed an increase in slope difference between gases in transient microG, the opposite of the decrease in sustained microG. In contrast, tidal volume SBW showed a decrease in slope difference in both microG conditions. Because it is only the behavior of the more diffusive gas that differed between maneuvers and microG conditions, we speculate that, in the previous vital capacity SBW, the hypergravity period preceding the test in transient microG provoked conformational changes at low lung volumes near the acinar entrance.

A space-based climatology of diurnal MLT tidal winds, temperatures and densities from UARS wind measurements

NASA Astrophysics Data System (ADS)

Svoboda, Aaron A.; Forbes, Jeffrey M.; Miyahara, Saburo

2005-11-01

A self-consistent global tidal climatology, useful for comparing and interpreting radar observations from different locations around the globe, is created from space-based Upper Atmosphere Research Satellite (UARS) horizontal wind measurements. The climatology created includes tidal structures for horizontal winds, temperature and relative density, and is constructed by fitting local (in latitude and height) UARS wind data at 95 km to a set of basis functions called Hough mode extensions (HMEs). These basis functions are numerically computed modifications to Hough modes and are globally self-consistent in wind, temperature, and density. We first demonstrate this self-consistency with a proxy data set from the Kyushu University General Circulation Model, and then use a linear weighted superposition of the HMEs obtained from monthly fits to the UARS data to extrapolate the global, multi-variable tidal structure. A brief explanation of the HMEs’ origin is provided as well as information about a public website that has been set up to make the full extrapolated data sets available.

Variability of tidal signals in the Brent Delta Front: New observations on the Rannoch Formation, northern North Sea

NASA Astrophysics Data System (ADS)

Wei, Xiaojie; Steel, Ronald J.; Ravnås, Rodmar; Jiang, Zaixing; Olariu, Cornel; Li, Zhiyang

2016-04-01

Detailed observations on the Rannoch Formation in several deep Viking Graben wells indicate that the 'classical' wave-dominated Brent delta-front shows coupled storm-tide processes. The tidal signals are of three types: I): alternations of thick cross-laminated sandstone and thin mud-draped sandstone, whereby double mud drapes are prominent but discretely distributed, II): a few tidal bundles within bottomsets and foresets of up to 10 cm-thick sets cross-strata, and III): dm-thick heterolithic lamination showing multiple, well-organized sand-mud couplets. During progradation of the Brent Delta, the Rannoch shoreline system passed upward from 1) a succession dominated by clean-water, storm-event sets and cosets frequently and preferentially interbedded with type I tidal beds, and occasional types II and III tidal deposits, toward 2) very clean storm-event beds less frequently separated by types II and III tidal beds, and then into 3) a thin interval showing muddier storm-event beds mainly alternating with type II tidal beds. It is likely that those variations in preservation bias of storm and tidal beds in each facies succession result from combined effects of 1) the frequency and duration of storms; 2) river discharge; and 3) the absolute and relative strength of tides. Tidal deposits are interpreted as inter-storm, fair-weather deposits, occurred preferentially in longer intermittent fair-weather condition and periods of lower river discharge, and well-pronounced in the distal-reach of delta-front. The formation and preservation of tidal signals between storm beds, indicate that the studied Rannoch Formation was most likely a storm-dominated, tide-influenced delta front 1) near the mouth of a large Brent river, where a significant tidal prism and high tidal range might be expected, and 2) in a setting where there were relatively high sedimentation rates associated with high local subsidence rates, so that the storm waves did not completely rework the inter-storm deposits. The documentation of the unconventional Rannoch Formation contributes to our understanding of mixed-energy coastal systems.

Ventilation-perfusion relationships in the lung during head-out water immersion

NASA Technical Reports Server (NTRS)

Derion, Toniann; Guy, Harold J. B.; Tsukimoto, Koichi; Schaffartzik, Walter; Prediletto, Renato; Poole, David C.; Knight, Douglas R.; Wagner, Peter D.

1992-01-01

Mechanisms of altered pulmonary gas exchange during water immersion were studied in 12 normal males: 6 young (aged 20-29) and 6 older (aged 40-45). It is concluded that, in young subjects with closing volume (CV) less than expiratory reserve volume (ERV), gas exchange was enhanced during immersion, because normal ventilation-perfusion relations were preserved, and by mass balance, the ventilation/O2 uptake changes elevated arterial P(O2). In older males with CV greater than ERV and 52 percent of tidal volume below CV, immersion-induced airways closure during tidal breathing was associated with minimally increased shunt that did not significantly impair gas exchange. It is suggested that airways closure of this degree is of little importance to gas exchange.

A life-cycle model for wave-dominated tidal inlets along passive margin coasts of North America

NASA Astrophysics Data System (ADS)

Seminack, Christopher T.; McBride, Randolph A.

2018-03-01

A regional overview of 107 wave-dominated tidal inlets along the U.S. Atlantic coast, U.S. Gulf of Mexico coast, and Canadian Gulf of St. Lawrence coast yielded a generalized wave-dominated tidal inlet life-cycle model that recognized the rotational nature of tidal inlets. Tidal inlets are influenced by concurrently acting processes transpiring over two timescales: short-term, event-driven processes and long-term, evolutionary processes. Wave-dominated tidal inlets are classified into three rotational categories based on net longshore sediment transport direction and rotation direction along the landward (back-barrier) portion of the inlet channel: downdrift channel rotation, updrift channel rotation, or little-to-no channel rotation. Lateral shifting of the flood-tidal delta depocenter in response to available estuarine accommodation space appears to control inlet channel rotation. Flood-tidal delta deposits fill accommodation space locally within the estuary (i.e., creating bathymetric highs), causing the tidal-inlet channel to rotate. External influences, such as fluvial discharge, pre-existing back-barrier channels, and impeding salt marsh will also influence inlet-channel rotation. Storm events may rejuvenate the tidal inlet by scouring sediment within the flood-tidal delta, increasing local accommodation space. Wave-dominated tidal inlets are generally unstable and tend to open, concurrently migrate laterally and rotate, infill, and close. Channel rotation is a primary reason for wave-dominated tidal inlet closure. During rotation, the inlet channel lengthens and hydraulic efficiency decreases, thus causing tidal prism to decrease. Tidal prism, estuarine accommodation space, and sediment supply to the flood-tidal delta are the primary variables responsible for tidal inlet rotation. Stability of wave-dominated tidal inlets is further explained by: stability (S) = tidal prism (Ω) + estuarine accommodation space (V) - volume of annual sediment supply (Mt). Rotating wave-dominated tidal inlets follow a six-stage evolutionary model; whereas wave-dominated tidal inlets that exhibit little-to-no rotation follow a five-stage evolutionary model.

Determination of mass balance and entrainment in the stratified Duwamish River Estuary, King County, Washington

USGS Publications Warehouse

Stoner, J.D.

1972-01-01

During a study of the effects of waste-water input on the stratified Duwamish River estuary, intensive water-velocity and salinity measurements were made in both the lower salt wedge and the upper fresher water layer for tidal-cycle periods. The net movement of water and salt mass past a cross section during a tidal cycle was determined from integration of the measured rates of movement of water and salt past the section. The net volume of water that moved downstream past the section during the cycle agreed with the volume of fresh-water inflow at the head of the estuary within (1) 3.8 and 7.2 percent, respectively, for two studies made during periods of maximum and minimum tidal-prism thickness and identical inflow rates .of 312 cfs (cubic feet per second), and (2) 15 percent for one study made during a period of average tidal-prism thickness and an inflow rate of 1,280 cfs. For the three studies, the difference between salt mass transported upstream and downstream during the cycles ranged from 0.8 to 19 percent of the respective mean salt-mass transport. Water was entrained from the .salt-water wedge into the overlying layer of mixed fresh and salt water at tidal-cycle-average rates of 30 and 69 cfs per million square feet of interface for the inflow rates of 312 cfs, and 99 cfs per million square feet of interface for an inflow rate of 1,280 cfs. At a constant inflow rate, the rate of entrainment of salt-wedge water in the Duwamish River estuary more than doubled for a doubling of tidal-prism thickness. It also doubled for a quadrupling of inflow rate at about constant tidal-prism thickness.

Role of bronchodilation and pattern of breathing in increasing tidal expiratory flow with progressive induced hypercapnia in chronic obstructive pulmonary disease.

PubMed

Finucane, Kevin E; Singh, Bhajan

2018-01-01

Hypercapnia (HC) in vitro relaxes airway smooth muscle; in vivo, it increases respiratory effort, tidal expiratory flows (V̇ exp ), and, by decreasing inspiratory duration (Ti), increases elastic recoil pressure (Pel) via lung viscoelasticity; however, its effect on airway resistance is uncertain. We examined the contributions of bronchodilation, Ti, and expiratory effort to increasing V̇ exp with progressive HC in 10 subjects with chronic obstructive pulmonary disease (COPD): mean forced expiratory volume in 1 s (FEV 1 ) 53% predicted. Lung volumes (Vl), V̇ exp , esophageal pressure (Pes), Ti, and end-tidal Pco 2 ([Formula: see text]) were measured during six tidal breaths followed by an inspiratory capacity (IC), breathing air, and at three levels of HC. V̇ exp and V̇ with submaximal forced vital capacities breathing air (V̇ sFVC ) were compared. Pulmonary resistance ( Rl) was measured from the Pes-V̇ relationship. V̇ exp and Pes at end-expiratory lung volume (EELV) + 0.3 tidal volume [V̇ (0.3Vt) and Pes (0.3Vt) , respectively], Ti, and Rl correlated with [Formula: see text] ( P < 0.001 for all) and were independent of tiotropium. [Formula: see text], Ti, and Pes (0.3Vt) predicted the increasing V̇ (0.3Vt) /V̇ sFVC(0.3Vt) [multiple regression analysis (MRA): P = 0.001, 0.004, and 0.025, respectively]. At [Formula: see text] ≥ 50 Torr, V̇ (0.3Vt) /V̇ sFVC(0.3Vt) exceeded unity in 30 of 36 measurements and was predicted by [Formula: see text] and Pes (0.3Vt) (MRA: P = 0.02 and 0.025, respectively). Rl decreased at [Formula: see text] 45 Torr ( P < 0.05) and did not change with further HC. IC and Vl (0.3Vt) did not change with HC. We conclude that in COPD HC increases V̇ exp due to bronchodilation, increased Pel secondary to decreasing Ti, and increased expiratory effort, all promoting lung emptying and a stable EELV. NEW & NOTEWORTHY The response of airways to intrapulmonary hypercapnia (HC) is uncertain. In chronic obstructive pulmonary disease (COPD), progressive HC increases tidal expiratory flows by inducing bronchodilation and via an increased rate of inspiration and lung viscoelasticity, a probable increase in lung elastic recoil pressure, both changes increasing expiratory flows, promoting lung emptying and a stable end-expiratory volume. Bronchodilation with HC occurred despite optimal standard bronchodilator therapy, suggesting that in COPD further bronchodilation is possible.

Tidal Volume Estimation Using the Blanket Fractal Dimension of the Tracheal Sounds Acquired by Smartphone

PubMed Central

Reljin, Natasa; Reyes, Bersain A.; Chon, Ki H.

2015-01-01

In this paper, we propose the use of blanket fractal dimension (BFD) to estimate the tidal volume from smartphone-acquired tracheal sounds. We collected tracheal sounds with a Samsung Galaxy S4 smartphone, from five (N = 5) healthy volunteers. Each volunteer performed the experiment six times; first to obtain linear and exponential fitting models, and then to fit new data onto the existing models. Thus, the total number of recordings was 30. The estimated volumes were compared to the true values, obtained with a Respitrace system, which was considered as a reference. Since Shannon entropy (SE) is frequently used as a feature in tracheal sound analyses, we estimated the tidal volume from the same sounds by using SE as well. The evaluation of the performed estimation, using BFD and SE methods, was quantified by the normalized root-mean-squared error (NRMSE). The results show that the BFD outperformed the SE (at least twice smaller NRMSE was obtained). The smallest NRMSE error of 15.877% ± 9.246% (mean ± standard deviation) was obtained with the BFD and exponential model. In addition, it was shown that the fitting curves calculated during the first day of experiments could be successfully used for at least the five following days. PMID:25923929

Tidal volume estimation using the blanket fractal dimension of the tracheal sounds acquired by smartphone.

PubMed

Reljin, Natasa; Reyes, Bersain A; Chon, Ki H

2015-04-27

In this paper, we propose the use of blanket fractal dimension (BFD) to estimate the tidal volume from smartphone-acquired tracheal sounds. We collected tracheal sounds with a Samsung Galaxy S4 smartphone, from five (N = 5) healthy volunteers. Each volunteer performed the experiment six times; first to obtain linear and exponential fitting models, and then to fit new data onto the existing models. Thus, the total number of recordings was 30. The estimated volumes were compared to the true values, obtained with a Respitrace system, which was considered as a reference. Since Shannon entropy (SE) is frequently used as a feature in tracheal sound analyses, we estimated the tidal volume from the same sounds by using SE as well. The evaluation of the performed estimation, using BFD and SE methods, was quantified by the normalized root-mean-squared error (NRMSE). The results show that the BFD outperformed the SE (at least twice smaller NRMSE was obtained). The smallest NRMSE error of 15.877% ± 9.246% (mean ± standard deviation) was obtained with the BFD and exponential model. In addition, it was shown that the fitting curves calculated during the first day of experiments could be successfully used for at least the five following days.

Catalog of worldwide tidal bore occurrences and characteristics

USGS Publications Warehouse

Bartsch-Winkler, S.; Lynch, David K.

1988-01-01

Documentation of tidal bore phenomena occurring throughout the world aids in defining the typical geographical setting of tidal bores and enables prediction of their occurrence in remote areas. Tidal bores are naturally occurring, tidally generated, solitary, moving water waves up to 6 meters in height that form upstream in estuaries with semidiurnal or nearly semidiurnal tide ranges exceeding 4 meters. Estuarine settings that have tidal bores typically include meandering fluvial systems with shallow gradients. Bores are well defined, having amplitudes greater than wind- or turbulence-caused waves, and may be undular or breaking. Formation of a bore is dependent on depth and velocity of the incoming tide and river outflow. Bores may occur in series (in several channels) or in succession (marking each tidal pulse). Tidal bores propagate up tidal estuaries a greater distance than the width of the estuary and most occur within 100 kilometers upstream of the estuary mouth. Because they are dynamic, bores cause difficulties in some shipping ports and are targets for eradication. Tidal bores are known to occur, or to have occurred in the recent past, in at least 67 localities in 16 countries at all latitudes, including every continent except Antarctica. Parts of Argentina, Canada, Central America, China, Mozambique, Madagascar, Northern Europe, North and South Korea, the United Kingdom, and the U.S.S.R. probably have additional undiscovered or unreported tidal bores. In Turnagain Arm estuary in Alaska, bores cause an abrupt increase in salinity, suspended sediment, surface character, and bottom pressure, a decrease in illumination of the water column, and a change in water temperature. Tidal bores occurring in Turnagain Arm, Alaska, have the

Treatment response of airway clearance assessed by single-breath washout in children with cystic fibrosis.

PubMed

Abbas, Chiara; Singer, Florian; Yammine, Sophie; Casaulta, Carmen; Latzin, Philipp

2013-12-01

We studied the ability of 4 single-breath gas washout (SBW) tests to measure immediate effects of airway clearance in children with CF. 25 children aged 4-16 years with CF performed pulmonary function tests to assess short-term variability at baseline and response to routine airway clearance. Tidal helium and sulfur hexafluoride (double-tracer gas: DTG) SBW, tidal capnography, tidal and vital capacity nitrogen (N2) SBW and spirometry were applied. We analyzed the gasses' phase III slope (SnIII--normalized for tidal volume) and FEV1 from spirometry. SnIII from tidal DTG-SBW, SnIII from vital capacity N2-SBW, and FEV1 improved significantly after airway clearance. From these tests, individual change of SnIII from tidal DTG-SBW and FEV1 exceeded short-term variability in 10 and 6 children. With the tidal DTG-SBW, an easy and promising test for peripheral gas mixing efficiency, immediate pulmonary function response to airway clearance can be assessed in CF children. Copyright © 2013 European Cystic Fibrosis Society. Published by Elsevier B.V. All rights reserved.

Analytical models for the groundwater tidal prism and associated benthic water flux

USGS Publications Warehouse

King, Jeffrey N.; Mehta, Ashish J.; Dean, Robert G.

2010-01-01

The groundwater tidal prism is defined as the volume of water that inundates a porous medium, forced by one tidal oscillation in surface water. The pressure gradient that generates the prism acts on the subterranean estuary. Analytical models for the groundwater tidal prism and associated benthic flux are presented. The prism and flux are shown to be directly proportional to porosity, tidal amplitude, and the length of the groundwater wave; flux is inversely proportional to tidal period. The duration of discharge flux exceeds the duration of recharge flux over one tidal period; and discharge flux continues for some time following low tide. Models compare favorably with laboratory observations and are applied to a South Atlantic Bight study area, where tide generates an 11-m3 groundwater tidal prism per m of shoreline, and drives 81 m3 s −1 to the study area, which describes 23% of an observational estimate. In a marine water body, the discharge component of any oscillatory benthic water flux is submarine groundwater discharge. Benthic flux transports constituents between groundwater and surface water, and is a process by which pollutant loading and saltwater intrusion may occur in coastal areas.

Spatiotemporal Aeration and Lung Injury Patterns Are Influenced by the First Inflation Strategy at Birth.

PubMed

Tingay, David G; Rajapaksa, Anushi; Zonneveld, C Elroy; Black, Don; Perkins, Elizabeth J; Adler, Andy; Grychtol, Bartłomiej; Lavizzari, Anna; Frerichs, Inéz; Zahra, Valerie A; Davis, Peter G

2016-02-01

Ineffective aeration during the first inflations at birth creates regional aeration and ventilation defects, initiating injurious pathways. This study aimed to compare a sustained first inflation at birth or dynamic end-expiratory supported recruitment during tidal inflations against ventilation without intentional recruitment on gas exchange, lung mechanics, spatiotemporal regional aeration and tidal ventilation, and regional lung injury in preterm lambs. Lambs (127 ± 2 d gestation), instrumented at birth, were ventilated for 60 minutes from birth with either lung-protective positive pressure ventilation (control) or as per control after either an initial 30 seconds of 40 cm H2O sustained inflation (SI) or an initial stepwise end-expiratory pressure recruitment maneuver during tidal inflations (duration 180 s; open lung ventilation [OLV]). At study completion, molecular markers of lung injury were analyzed. The initial use of an OLV maneuver, but not SI, at birth resulted in improved lung compliance, oxygenation, end-expiratory lung volume, and reduced ventilatory needs compared with control, persisting throughout the study. These changes were due to more uniform inter- and intrasubject gravity-dependent spatiotemporal patterns of aeration (measured using electrical impedance tomography). Spatial distribution of tidal ventilation was more stable after either recruitment maneuver. All strategies caused regional lung injury patterns that mirrored associated regional volume states. Irrespective of strategy, spatiotemporal volume loss was consistently associated with up-regulation of early growth response-1 expression. Our results show that mechanical and molecular consequences of lung aeration at birth are not simply related to rapidity of fluid clearance; they are also related to spatiotemporal pressure-volume interactions within the lung during inflation and deflation.

Sniffing position combined with mouth opening improves facemask ventilation in children with adenotonsillar hypertrophy.

PubMed

Cuvas, O; Dikmen, B; Yucel, F

2011-05-01

This study evaluates the influence of sniffing position combined with mouth opening on the effectiveness of facemask ventilation in paralyzed pediatric patients undergoing adenotonsillectomy during sevoflurane-N(2)O anesthesia. After Institutional Ethics Committee approval, 40 children 5-11 years of age who were scheduled for an elective adenotonsillectomy operation were enrolled in this prospective randomized study. After routine monitoring and pre-oxygenation, anesthesia was induced with sevoflurane 8% in a mixture of 50% N(2)O-O(2). Three minutes after the administration of vecuronium, the sequence of the positions was randomized. Three positions were applied during facemask ventilation: Position CN (closed mouth - neutral head and neck position), position CS (closed mouth-sniffing position) and position OS (opened mouth-sniffing position). Volume-controlled ventilation was started. Peak inspiratory pressure (PIP), tidal volume (V(T)), expired tidal volume (V(Texp)) and end-tidal CO(2) pressure were recorded. The percent of leakage was calculated. The primary endpoint of this study was the expired tidal volume (V(Texp)). There was a statistically significant difference among the three positions for V(Texp) and PIP values. The OS resulted in higher V(Texp) values when compared with CN (P=0.022). The OS was significantly better than the other two positions, resulting in lower PIP values (P<0.001 and P=0.004, for CN and CS, respectively). The OS also resulted in less leakage during facemask ventilation when compared with CN and CS. Sniffing position combined with mouth opening improves V(Texp) and PIP values during facemask ventilation during sevoflurane-N(2)O anesthesia in paralyzed pediatric patients with adenotonsillar hypertrophy.

Mechanics of lung ventilation in a post-metamorphic salamander, Ambystoma Tigrinum.

PubMed

Simons, R S; Bennett, W O; Brainerd, E L

2000-03-01

The mechanics of lung ventilation in frogs and aquatic salamanders has been well characterized, whereas lung ventilation in terrestrial-phase (post-metamorphic) salamanders has received little attention. We used electromyography (EMG), X-ray videography, standard videography and buccal and body cavity pressure measurements to characterize the ventilation mechanics of adult (post-metamorphic) tiger salamanders (Ambystoma tigrinum). Three results emerged: (i) under terrestrial conditions or when floating at the surface of the water, adult A. tigrinum breathed through their nares using a two-stroke buccal pump; (ii) in addition to this narial two-stroke pump, adult tiger salamanders also gulped air in through their mouths using a modified two-stroke buccal pump when in an aquatic environment; and (iii) exhalation in adult tiger salamanders is active during aquatic gulping breaths, whereas exhalation appears to be passive during terrestrial breathing at rest. Active exhalation in aquatic breaths is indicated by an increase in body cavity pressure during exhalation and associated EMG activity in the lateral hypaxial musculature, particularly the M. transversus abdominis. In terrestrial breathing, no EMG activity in the lateral hypaxial muscles is generally present, and body cavity pressure decreases during exhalation. In aquatic breaths, tidal volume is larger than in terrestrial breaths, and breathing frequency is much lower (approximately 1 breath 10 min(-)(1 )versus 4-6 breaths min(-)(1)). The use of hypaxial muscles to power active exhalation in the aquatic environment may result from the need for more complete exhalation and larger tidal volumes when breathing infrequently. This hypothesis is supported by previous findings that terrestrial frogs ventilate their lungs with small tidal volumes and exhale passively, whereas aquatic frogs and salamanders use large tidal volumes and and exhale actively.

On the tidal prism-channel area relations

NASA Astrophysics Data System (ADS)

D'Alpaos, Andrea; Lanzoni, Stefano; Marani, Marco; Rinaldo, Andrea

2010-03-01

We verify the broad applicability of tidal prism cross-sectional area relationships, originally proposed to relate the total water volume entering a lagoon during a characteristic tidal cycle (the tidal prism) to the size of its inlet, to arbitrary sheltered cross sections within a tidal network. We suggest, with reasonable approximation defining a statistical tendency rather than a pointwise equivalence, that the regime of tidal channels may be anywhere related to local landscape-forming prisms embedded in a characteristic spring tide oscillation. The importance of the proposed extension stems from its potential for quantitative predictions of the long-term morphological evolution of whole tidal landforms, in response to forcings affecting tidal prisms. This is the case, in particular, for alterations of relative mean sea levels possibly driven by climate change. Various 1-D and 2-D morphodynamic and hydrodynamic models are employed to evaluate peak flow rates, bottom shear stresses, and the ensuing local tidal prisms. One-dimensional morphodynamic models describing both the longitudinal and cross-sectional evolution of tidal channels are used to verify the validity of the relationship for sheltered sections. Relevant hydrodynamic features determined through accurate 2-D numerical models are compared with those obtained through time-invariant equivalents, defining a mean watershed by an energy landscape from averaged free surface gradients. Empirical evidence gathered within the lagoon of Venice (Italy) supports the proposed extension. We conclude that the geomorphic law relating tidal prisms to channel cross-sectional areas anywhere within a tidal landscape is a valuable tool for studies on long-term tidal geomorphology.

Driving pressure and mechanical power: new targets for VILI prevention.

PubMed

Tonetti, Tommaso; Vasques, Francesco; Rapetti, Francesca; Maiolo, Giorgia; Collino, Francesca; Romitti, Federica; Camporota, Luigi; Cressoni, Massimo; Cadringher, Paolo; Quintel, Michael; Gattinoni, Luciano

2017-07-01

Several factors have been recognized as possible triggers of ventilator-induced lung injury (VILI). The first is pressure (thus the 'barotrauma'), then the volume (hence the 'volutrauma'), finally the cyclic opening-closing of the lung units ('atelectrauma'). Less attention has been paid to the respiratory rate and the flow, although both theoretical considerations and experimental evidence attribute them a significant role in the generation of VILI. The initial injury to the lung parenchyma is necessarily mechanical and it could manifest as an unphysiological distortion of the extracellular matrix and/or as micro-fractures in the hyaluronan, likely the most fragile polymer embedded in the matrix. The order of magnitude of the energy required to break a molecular bond between the hyaluronan and the associated protein is 1.12×10 -16 Joules (J), 70-90% higher than the average energy delivered by a single breath of 1L assuming a lung elastance of 10 cmH 2 O/L (0.5 J). With a normal statistical distribution of the bond strength some polymers will be exposed each cycle to an energy large enough to rupture. Both the extracellular matrix distortion and the polymer fractures lead to inflammatory increase of capillary permeability with edema if a pulmonary blood flow is sufficient. The mediation analysis of higher vs. lower tidal volume and PEEP studies suggests that the driving pressure, more than tidal volume, is the best predictor of VILI, as inferred by increased mortality. This is not surprising, as both tidal volume and respiratory system elastance (resulting in driving pressure) may independently contribute to the mortality. For the same elastance driving pressure is a predictor similar to plateau pressure or tidal volume. Driving pressure is one of the components of the mechanical power, which also includes respiratory rate, flow and PEEP. Finding the threshold for mechanical power would greatly simplify assessment and prevention of VILI.

Evaluation of ventilators used during transport of critically ill patients: a bench study.

PubMed

Boussen, Salah; Gainnier, Marc; Michelet, Pierre

2013-11-01

To evaluate the most recent transport ventilators' operational performance regarding volume delivery in controlled mode, trigger function, and the quality of pressurization in pressure support mode. Eight recent transport ventilators were included in a bench study in order to evaluate their accuracy to deliver a set tidal volume under normal resistance and compliance conditions, ARDS conditions, and obstructive conditions. The performance of the triggering system was assessed by the measure of the decrease in pressure and the time delay required to open the inspiratory valve. The quality of pressurization was obtained by computing the integral of the pressure-time curve for the first 300 ms and 500 ms after the onset of inspiration. For the targeted tidal volumes of 300, 500, and 800 mL the errors ranged from -3% to 48%, -7% to 18%, and -5% to 25% in the normal conditions, -4% to 27%, -2% to 35%, and -3% to 35% in the ARDS conditions, and -4% to 53%, -6% to 30%, and -30% to 28% in the obstructive conditions. In pressure support mode the pressure drop range was 0.4-1.7 cm H2O, the trigger delay range was 68-198 ms, and the pressurization performance (percent of ideal pressurization, as measured by pressure-time product at 300 ms and 500 ms) ranges were -9% to 44% at 300 ms and 6%-66% at 500 ms (P < .01). There were important differences in the performance of the tested ventilators. The most recent turbine ventilators outperformed the pneumatic ventilators. The best performers among the turbine ventilators proved comparable to modern ICU ventilators.

The effects of tidal range on saltmarsh morphology

NASA Astrophysics Data System (ADS)

Goodwin, Guillaume; Mudd, Simon

2017-04-01

Saltmarshes are highly productive coastal ecosystems that act simultaneously as flood barriers, carbon storage, pollutant filters and nurseries. As halophytic plants trap suspended sediment and decay in the settled strata, innervated platforms emerge from the neighbouring tidal flats, forming sub-vertical scarps on their eroding borders and sub-horizontal pioneer zones in areas of seasonal expansion. These evolutions are subject to two contrasting influences: stochastically generated waves erode scarps and scour tidal flats, whereas tidally-generated currents transport sediment to and from the marsh through the channel network. Hence, the relative power of waves and tidal currents strongly influences saltmarsh evolution, and regional variations in tidal range yield marshes of differing morphologies. We analyse several sheltered saltmarshes to determine how their morphology reflects variations in tidal forcing. Using tidal, topographic and spectral data, we implement an algorithm based on the open-source software LSDTopoTools to automatically identify features such as marsh platforms, tidal flats, erosion scarps, pioneer zones and tidal channels on local Digital Elevation Models. Normalised geometric properties are then computed and compared throughout the spectrum of tidal range, highlighting a notable effect on channel networks, platform geometry and wave exposure. We observe that micro-tidal marshes typically display jagged outlines and multiple islands along with wide, shallow channels. As tidal range increases, we note the progressive disappearance of marsh islands and linearization of scarps, both indicative of higher hydrodynamic stress, along with a structuration of channel networks and the increase of levee volume, suggesting higher sediment input on the platform. Future research will lead to observing and modelling the evolution of saltmarshes under various tidal forcing in order to assess their resilience to environmental change.

Ridges and tidal stress on Io

USGS Publications Warehouse

Bart, G.D.; Turtle, E.P.; Jaeger, W.L.; Keszthelyi, L.P.; Greenberg, R.

2004-01-01

Sets of ridges of uncertain origin are seen in twenty-nine high-resolution Galileo images, which sample seven locales on Io. These ridges are on the order of a few kilometers in length with a spacing of about a kilometer. Within each locale, the ridges have a consistent orientation, but the orientations vary from place to place. We investigate whether these ridges could be a result of tidal flexing of Io by comparing their orientations with the peak tidal stress orientations at the same locations. We find that ridges grouped near the equator are aligned either north-south or east-west, as are the predicted principal stress orientations there. It is not clear why particular groups run north-south and others east-west. The one set of ridges observed far from the equator (52?? S) has an oblique azimuth, as do the tidal stresses at those latitudes. Therefore, all observed ridges have similar orientations to the tidal stress in their region. This correlation is consistent with the hypothesis that tidal flexing of Io plays an important role in ridge formation. ?? 2004 Elsevier Inc. All rights reserved.

Modes of mechanical ventilation for the operating room.

PubMed

Ball, Lorenzo; Dameri, Maddalena; Pelosi, Paolo

2015-09-01

Most patients undergoing surgical procedures need to be mechanically ventilated, because of the impact of several drugs administered at induction and during maintenance of general anaesthesia on respiratory function. Optimization of intraoperative mechanical ventilation can reduce the incidence of post-operative pulmonary complications and improve the patient's outcome. Preoxygenation at induction of general anaesthesia prolongs the time window for safe intubation, reducing the risk of hypoxia and overweighs the potential risk of reabsorption atelectasis. Non-invasive positive pressure ventilation delivered through different interfaces should be considered at the induction of anaesthesia morbidly obese patients. Anaesthesia ventilators are becoming increasingly sophisticated, integrating many functions that were once exclusive to intensive care. Modern anaesthesia machines provide high performances in delivering the desired volumes and pressures accurately and precisely, including assisted ventilation modes. Therefore, the physicians should be familiar with the potential and pitfalls of the most commonly used intraoperative ventilation modes: volume-controlled, pressure-controlled, dual-controlled and assisted ventilation. Although there is no clear evidence to support the advantage of any one of these ventilation modes over the others, protective mechanical ventilation with low tidal volume and low levels of positive end-expiratory pressure (PEEP) should be considered in patients undergoing surgery. The target tidal volume should be calculated based on the predicted or ideal body weight rather than on the actual body weight. To optimize ventilation monitoring, anaesthesia machines should include end-inspiratory and end-expiratory pause as well as flow-volume loop curves. The routine administration of high PEEP levels should be avoided, as this may lead to haemodynamic impairment and fluid overload. Higher PEEP might be considered during surgery longer than 3 h, laparoscopy in the Trendelenburg position and in patients with body mass index >35 kg/m(2). Large randomized trials are warranted to identify subgroups of patients and the type of surgery that can potentially benefit from specific ventilation modes or ventilation settings. Copyright © 2015 Elsevier Ltd. All rights reserved.

Humidification performance of humidifying devices for tracheostomized patients with spontaneous breathing: a bench study.

PubMed

Chikata, Yusuke; Oto, Jun; Onodera, Mutsuo; Nishimura, Masaji

2013-09-01

Heat and moisture exchangers (HMEs) are commonly used for humidifying respiratory gases administered to mechanically ventilated patients. While they are also applied to tracheostomized patients with spontaneous breathing, their performance in this role has not yet been clarified. We carried out a bench study to investigate the effects of spontaneous breathing parameters and oxygen flow on the humidification performance of 11 HMEs. We evaluated the humidification provided by 11 HMEs for tracheostomized patients, and also by a system delivering high-flow CPAP, and an oxygen mask with nebulizer heater. Spontaneous breathing was simulated with a mechanical ventilator, lung model, and servo-controlled heated humidifier at tidal volumes of 300, 500, and 700 mL, and breathing frequencies of 10 and 20 breaths/min. Expired gas was warmed to 37°C. The high-flow CPAP system was set to deliver 15, 30, and 45 L/min. With the 8 HMEs that were equipped with ports to deliver oxygen, and with the high-flow CPAP system, measurements were taken when delivering 0 and 3 L/min of dry oxygen. After stabilization we measured the absolute humidity (AH) of inspired gas with a hygrometer. AH differed among HMEs applied to tracheostomized patients with spontaneous breathing. For all the HMEs, as tidal volume increased, AH decreased. At 20 breaths/min, AH was higher than at 10 breaths/min. For all the HMEs, when oxygen was delivered, AH decreased to below 30 mg/L. With an oxygen mask and high-flow CPAP, at all settings, AH exceeded 30 mg/L. None of the HMEs provided adequate humidification when supplemental oxygen was added. In the ICU, caution is required when applying HME to tracheostomized patients with spontaneous breathing, especially when supplemental oxygen is required.

Respiratory Sinus Arrhythmia as an Index of Vagal Activity during Stress in Infants: Respiratory Influences and Their Control

PubMed Central

Ritz, Thomas; Bosquet Enlow, Michelle; Schulz, Stefan M.; Kitts, Robert; Staudenmayer, John; Wright, Rosalind J.

2012-01-01

Respiratory sinus arrhythmia (RSA) is related to cardiac vagal outflow and the respiratory pattern. Prior infant studies have not systematically examined respiration rate and tidal volume influences on infant RSA or the extent to which infants' breathing is too fast to extract a valid RSA. We therefore monitored cardiac activity, respiration, and physical activity in 23 six-month old infants during a standardized laboratory stressor protocol. On average, 12.6% (range 0–58.2%) of analyzed breaths were too short for RSA extraction. Higher respiration rate was associated with lower RSA amplitude in most infants, and lower tidal volume was associated with lower RSA amplitude in some infants. RSA amplitude corrected for respiration rate and tidal volume influences showed theoretically expected strong reductions during stress, whereas performance of uncorrected RSA was less consistent. We conclude that stress-induced changes of peak-valley RSA and effects of variations in breathing patterns on RSA can be determined for a representative percentage of infant breaths. As expected, breathing substantially affects infant RSA and needs to be considered in studies of infant psychophysiology. PMID:23300753

Efficacy of a new device to optimize positive pressure ventilation via face mask in edentulous patients: a randomized trial.

PubMed

Niño, Maria C; Pauwels, Andres; Raffan, Fernando; Arango, Enrique; Romero, David J; Benitez, Daniel

2017-04-01

Mask ventilation is routinely performed during anesthesia. Under some circumstances, it might be difficult to perform, such as in edentulous patients, due to inadequate mask seal. We developed a new device called NIPARA and studied its use For ventilation optimization in edentulous patients. This randomized controlled trial included edentulous adults who had no other predictors of difficult airway, scheduled to undergo general anesthesia. Patients were assigned either to the NIPARA device group or to the control group (oral airway only). The primary outcomes were peak inspiratory pressure and tidal volume values of the first 14 breaths. The secondary outcome was the incidence of complications. Data from 37 patients were collected during a one-year period (twenty in the NIPARA device group and 17 in the control group). The difference in mean PIP was not statistically significant. The tidal volume was 1.5 times greater in the NIPARA group than in the control group. One patient from the intervention group had minimal oral trauma. In the administration of face mask ventilation, NIPARA is an effective device that significantly improves the tidal volume administered in edentulous patients.

Role of central and peripheral opiate receptors in the effects of fentanyl on analgesia, ventilation and arterial blood-gas chemistry in conscious rats

PubMed Central

Henderson, Fraser; May, Walter J.; Gruber, Ryan B.; Discala, Joseph F.; Puscovic, Veljko; Young, Alex P.; Baby, Santhosh M.; Lewis, Stephen J.

2015-01-01

This study determined the effects of the peripherally restricted µ-opiate receptor (µ-OR) antagonist, naloxone methiodide (NLXmi) on fentanyl (25 µg/kg, i.v.)-induced changes in (1) analgesia, (2) arterial blood gas chemistry (ABG) and alveolar-arterial gradient (A-a gradient), and (3) ventilatory parameters, in conscious rats. The fentanyl-induced increase in analgesia was minimally affected by a 1.5 mg/kg of NLXmi but was attenuated by a 5.0 mg/kg dose. Fentanyl decreased arterial blood pH, pO2 and sO2 and increased pCO2 and A-a gradient. These responses were markedly diminished in NLXmi (1.5 mg/kg)-pretreated rats. Fentanyl caused ventilatory depression (e.g., decreases in tidal volume and peak inspiratory flow). Pretreatment with NLXmi (1.5 mg/kg, i.v.) antagonized the fentanyl decrease in tidal volume but minimally affected the other responses. These findings suggest that (1) the analgesia and ventilatory depression caused by fentanyl involve peripheral µ-ORs and (2) NLXmi prevents the fentanyl effects on ABG by blocking the negative actions of the opioid on tidal volume and A-a gradient. PMID:24284037

Respiratory responses to intermittent hypoxia in unsedated piglets: relation to substance P binding in brainstem.

PubMed

Laferrière, André; Moss, Immanuela Ravé

2004-10-12

Respiratory responses to single intermittent hypoxia (5 min 21% O(2), 5 min 8% O(2) X6) in 5-6, 10-11, 21-22 and 26-27 day-old piglets, and to recurrent six daily intermittent hypoxia in 10-11 and 26-27 day-old piglets were assessed. Substance P binding in the piglets' brainstem immediately after the last hypoxic episode was measured. All piglets hyperventilated during hypoxia. Weight adjusted inspired ventilation, tidal volume and instantaneous flow decreased with age. The oldest piglets uniquely displayed attenuated ventilation and tidal volume during the sixth versus first hypoxic episode with single intermittent hypoxia, and reduced inspired ventilation and tidal volume during the first hypoxic episode on the sixth daily hypoxia compared to single hypoxia. By contrast, substance P binding was greatly reduced in the solitary, hypoglossal, paraambigual and lateral reticular brainstem nuclei of both younger and older piglets following either single or recurrent intermittent hypoxia. Thus, the reduction in membrane-bound neurokinin receptors by intermittent hypoxia, presumably consequent to endogenously released substance P, does not exclusively determine whether the ventilatory response to that hypoxia will be attenuated or not.

Determining volume sensitive waters in Beaufort County, SC tidal creeks

Treesearch

Andrew Tweel; Denise Sanger; Anne Blair; John Leffler

2016-01-01

Non-point source pollution from stormwater runoff associated with large-scale land use changes threatens the integrity of ecologically and economically valuable estuarine ecosystems. Beaufort County, SC implemented volume-based stormwater regulations on the rationale that if volume discharge is controlled, contaminant loading will also be controlled.

Increasing compliance with low tidal volume ventilation in the ICU with two nudge-based interventions: evaluation through intervention time-series analyses

PubMed Central

Bourdeaux, Christopher P; Thomas, Matthew JC; Gould, Timothy H; Malhotra, Gaurav; Jarvstad, Andreas; Jones, Timothy; Gilchrist, Iain D

2016-01-01

Objectives Low tidal volume (TVe) ventilation improves outcomes for ventilated patients, and the majority of clinicians state they implement it. Unfortunately, most patients never receive low TVes. ‘Nudges’ influence decision-making with subtle cognitive mechanisms and are effective in many contexts. There have been few studies examining their impact on clinical decision-making. We investigated the impact of 2 interventions designed using principles from behavioural science on the deployment of low TVe ventilation in the intensive care unit (ICU). Setting University Hospitals Bristol, a tertiary, mixed medical and surgical ICU with 20 beds, admitting over 1300 patients per year. Participants Data were collected from 2144 consecutive patients receiving controlled mechanical ventilation for more than 1 hour between October 2010 and September 2014. Patients on controlled mechanical ventilation for more than 20 hours were included in the final analysis. Interventions (1) Default ventilator settings were adjusted to comply with low TVe targets from the initiation of ventilation unless actively changed by a clinician. (2) A large dashboard was deployed displaying TVes in the format mL/kg ideal body weight (IBW) with alerts when TVes were excessive. Primary outcome measure TVe in mL/kg IBW. Findings TVe was significantly lower in the defaults group. In the dashboard intervention, TVe fell more quickly and by a greater amount after a TVe of 8 mL/kg IBW was breached when compared with controls. This effect improved in each subsequent year for 3 years. Conclusions This study has demonstrated that adjustment of default ventilator settings and a dashboard with alerts for excessive TVe can significantly influence clinical decision-making. This offers a promising strategy to improve compliance with low TVe ventilation, and suggests that using insights from behavioural science has potential to improve the translation of evidence into practice. PMID:27230998

A simple, inexpensive, and field-relevant microcosm tidal simulator for use in marsh macrophyte studies1

PubMed Central

MacTavish, Rachel M.; Cohen, Risa A.

2014-01-01

• Premise of the study: A microcosm unit with tidal simulation was developed to address the challenge of maintaining ecologically relevant tidal regimes while performing controlled greenhouse experiments on smooth cordgrass, Spartina alterniflora. • Methods and Results: We designed a simple, inexpensive, easily replicated microcosm unit with tidal simulation and tested whether S. alterniflora growth in microcosms with tidal simulation was similar to that of tidally influenced plants in the field on Sapelo Island, Georgia. After three months of exposure to either natural or simulated tidal treatment, plants in microcosms receiving tidal simulation had similar stem density, height, and above- and belowground biomass to plants in field plots. • Conclusions: The tidal simulator developed may provide an inexpensive, effective method for conducting studies on S. alterniflora and other tidally influenced plants in controlled settings to be used not only to complement field studies, but also in locations without coastal access. PMID:25383265

Continuous positive airway pressure and ventilation are more effective with a nasal mask than a full face mask in unconscious subjects: a randomized controlled trial.

PubMed

Oto, Jun; Li, Qian; Kimball, William R; Wang, Jingping; Sabouri, Abdolnabi S; Harrell, Priscilla G; Kacmarek, Robert M; Jiang, Yandong

2013-12-23

Upper airway obstruction (UAO) is a major problem in unconscious subjects, making full face mask ventilation difficult. The mechanism of UAO in unconscious subjects shares many similarities with that of obstructive sleep apnea (OSA), especially the hypotonic upper airway seen during rapid eye movement sleep. Continuous positive airway pressure (CPAP) via nasal mask is more effective at maintaining airway patency than a full face mask in patients with OSA. We hypothesized that CPAP via nasal mask and ventilation (nCPAP) would be more effective than full face mask CPAP and ventilation (FmCPAP) for unconscious subjects, and we tested our hypothesis during induction of general anesthesia for elective surgery. In total, 73 adult subjects requiring general anesthesia were randomly assigned to one of four groups: nCPAP P0, nCPAP P5, FmCPAP P0, and FmCPAP P5, where P0 and P5 represent positive end-expiratory pressure (PEEP) 0 and 5 cm H2O applied prior to induction. After apnea, ventilation was initiated with pressure control ventilation at a peak inspiratory pressure over PEEP (PIP/PEEP) of 20/0, then 20/5, and finally 20/10 cm H2O, each applied for 1 min. At each pressure setting, expired tidal volume (Vte) was calculated by using a plethysmograph device. The rate of effective tidal volume (Vte > estimated anatomical dead space) was higher (87.9% vs. 21.9%; P<0.01) and the median Vte was larger (6.9 vs. 0 mL/kg; P<0.01) with nCPAP than with FmCPAP. Application of CPAP prior to induction of general anesthesia did not affect Vte in either approach (nCPAP pre- vs. post-; 7.9 vs. 5.8 mL/kg, P = 0.07) (FmCPAP pre- vs. post-; 0 vs. 0 mL/kg, P = 0.11). nCPAP produced more effective tidal volume than FmCPAP in unconscious subjects. ClinicalTrials.gov identifier: NCT01524614.

Protective Lung Ventilation and Morbidity After Pulmonary Resection: A Propensity Score-Matched Analysis.

PubMed

Amar, David; Zhang, Hao; Pedoto, Alessia; Desiderio, Dawn P; Shi, Weiji; Tan, Kay See

2017-07-01

Protective lung ventilation (PLV) during one-lung ventilation (OLV) for thoracic surgery is frequently recommended to reduce pulmonary complications. However, limited outcome data exist on whether PLV use during OLV is associated with less clinically relevant pulmonary morbidity after lung resection. Intraoperative data were prospectively collected in 1080 patients undergoing pulmonary resection with OLV, intentional crystalloid restriction, and mechanical ventilation to maintain inspiratory peak airway pressure <30 cm H2O. Other ventilator settings and all aspects of anesthetic management were at the discretion of the anesthesia care team. We defined PLV and non-PLV as <8 or ≥8 mL/kg (predicted body weight) mean tidal volume. The primary outcome was the occurrence of pneumonia and/or acute respiratory distress syndrome (ARDS). Propensity score matching was used to generate PLV and non-PLV groups with comparable characteristics. Associations between outcomes and PLV status were analyzed by exact logistic regression, with matching as cluster in the anatomic and nonanatomic lung resection cohorts. In the propensity score-matched analysis, the incidence of pneumonia and/or ARDS among patients who had an anatomic lung resection was 9/172 (5.2%) in the non-PLV compared to the PLV group 7/172 (4.1%; odds ratio, 1.29; 95% confidence interval, 0.48-3.45, P= .62). The incidence of pneumonia and/or ARDS in patients who underwent nonanatomic resection was 3/118 (2.5%) in the non-PLV compared to the PLV group, 1/118 (0.9%; odds ratio, 3.00; 95% confidence interval, 0.31-28.84, P= .34). In this prospective observational study, we found no differences in the incidence of pneumonia and/or ARDS between patients undergoing lung resection with tidal volumes <8 or ≥8 mL/kg. Our data suggest that when fluid restriction and peak airway pressures are limited, the clinical impact of PLV in this patient population is small. Future randomized trials are needed to better understand the benefits of a small tidal volume strategy during OLV on clinically important outcomes.

Lung volumes in giraffes, Giraffa camelopardalis.

PubMed

Mitchell, G; Skinner, J D

2011-01-01

We have measured lung mass and trachea dimensions in 46 giraffes of both genders ranging in body mass from 147 kg to 1441 kg, calculated static and dynamic lung volumes, and developed allometric equations that relate changes in them to growth. We found that relative lung mass is 0.6±0.2% of body mass which is significantly less than it is in other mammals (1.1±0.1%). Total lung volume is significantly smaller (46.2±5.9 mL kg⁻¹) than in similar sized mammals (75.0±2.1 mL kg⁻¹). The lung volume:body mass ratio decreases during growth rather than increase as it does in other mammals. Tracheal diameter is significantly narrower than in similar sized mammals but dead space volume (2.9±0.5 mL kg⁻¹) is larger than in similar sized mammals (2.4±0.1 mL kg⁻¹). Our calculations suggest that tidal volume (10.5±0.2 mL kg⁻¹) is increased compared to that in other mammals(10.0±0.2 mL kg⁻¹) so that the dead space:tidal volume ratio is the same as in other mammals. Calculated Functional Residual Capacity is smaller than predicted (53.4±3.5 vs 33.7±0.6 mL kg⁻¹) as is Expiratory Reserve Volume (47.4±2.6 vs 27.2±1.0 mL kg⁻¹, but Residual Volume (6.0±0.4 mL kg⁻¹) is the same as in other similar sized mammals (6.0±0.9 mL kg⁻¹. Our calculations suggest that Inspiratory Reserve Volume is significantly reduced in size (11.6±1.6 vs 3.8±2.4 mL kg⁻¹), and, if so, the capacity to increase tidal volume is limited. Calculated dynamic lung volumes were the same as in similar sized mammals. We have concluded that giraffe morphology has resulted in lung volumes that are significantly different to that of similar sized mammals, but these changes do not compromise ventilatory capacity. Copyright © 2010 Elsevier Inc. All rights reserved.

Assessment and monitoring of flow limitation and other parameters from flow/volume loops.

PubMed

Dueck, R

2000-01-01

Flow/volume (F/V) spirometry is routinely used for assessing the type and severity of lung disease. Forced vital capacity (FVC) and timed vital capacity (FEV1) provide the best estimates of airflow obstruction in patients with asthma, chronic obstructive pulmonary disease (COPD) and emphysema. Computerized spirometers are now available for early home recognition of asthma exacerbation in high risk patients with severe persistent disease, and for recognition of either infection or rejection in lung transplant patients. Patients with severe COPD may exhibit expiratory flow limitation (EFL) on tidal volume (VT) expiratory F/V (VTF/V) curves, either with or without applying negative expiratory pressure (NEP). EFL results in dynamic hyperinflation and persistently raised alveolar pressure or intrinsic PEEP (PEEPi). Hyperinflation and raised PEEPi greatly enhance dyspnea with exertion through the added work of the threshold load needed to overcome raised pleural pressure. Esophageal (pleural) pressure monitoring may be added to VTF/V loops for assessing the severity of PEEPi: 1) to optimize assisted ventilation by mask or via endotracheal tube with high inspiratory flow rates to lower I:E ratio, and 2) to assess the efficacy of either pressure support ventilation (PSV) or low level extrinsic PEEP in reducing the threshold load of PEEPi. Intraoperative tidal volume F/V loops can also be used to document the efficacy of emphysema lung volume reduction surgery (LVRS) via disappearance of EFL. Finally, the mechanism of ventilatory constraint can be identified with the use of exercise tidal volume F/V loops referenced to maximum F/V loops and static lung volumes. Patients with severe COPD show inspiratory F/V loops approaching 95% of total lung capacity, and flow limitation over the entire expiratory F/V curve during light levels of exercise. Surprisingly, patients with a history of congestive heart failure may lower lung volume towards residual volume during exercise, thereby reducing airway diameter and inducing expiratory flow limitation.

The effect of body mass and sex on the accuracy of respiratory magnetometers for measurement of end-expiratory lung volumes.

PubMed

Avraam, Joanne; Bourke, Rosie; Trinder, John; Nicholas, Christian L; Brazzale, Danny; O'Donoghue, Fergal J; Rochford, Peter D; Jordan, Amy S

2016-11-01

Respiratory magnetometers are increasingly being used in sleep studies to measure changes in end-expiratory lung volume (EELV), including in obese obstructive sleep apnea patients. Despite this, the accuracy of magnetometers has not been confirmed in obese patients nor compared between sexes. Thus we compared spirometer-measured and magnetometer-estimated lung volume and tidal volume changes during voluntary end-expiratory lung volume changes of 1.5, 1, and 0.5 l above and 0.5 l below functional respiratory capacity in supine normal-weight [body mass index (BMI) < 25 kg/m] and healthy obese (BMI > 30 kg/m) men and women. Two different magnetometer calibration techniques proposed by Banzett et al. [Banzett RB, Mahan ST, Garner DM, Brughera A, Loring SH. J Appl Physiol (1985) 79: 2169-2176, 1995] and Sackner et al. [Sackner MA, Watson H, Belsito AS, Feinerman D, Suarez M, Gonzalez G, Bizousky F, Krieger B. J Appl Physiol (1985) 66: 410-420, 1989] were assessed. Across all groups and target volumes, magnetometers overestimated spirometer-measured EELV by ~65 ml (<0.001) with no difference between techniques (0.07). The Banzett method overestimated the spirometer EELV change in normal-weight women for all target volumes except +0.5 l, whereas no differences between mass or sex groups were observed for the Sackner technique. The variability of breath-to-breath measures of EELV was significantly higher for obese compared with nonobese subjects and was higher for the Sackner than Banzett technique. On the other hand, for tidal volume, both calibration techniques underestimated spirometer measurements (<0.001), with the underestimation being more marked for the Banzett than Sackner technique (0.03), in obese than normal weight (<0.001) and in men than in women (0.003). These results indicate that both body mass and sex affect the accuracy of respiratory magnetometers in measuring EELV and tidal volume. Copyright © 2016 the American Physiological Society.

Infrared end-tidal CO2 measurement does not accurately predict arterial CO2 values or end-tidal to arterial PCO2 gradients in rabbits with lung injury.

PubMed

Hopper, A O; Nystrom, G A; Deming, D D; Brown, W R; Peabody, J L

1994-03-01

End-tidal PCO2 (PETCO2) measurements from two commercially available neonatal infrared capnometers with different sampling systems and a mass spectrometer were compared with arterial PCO2 (PaCO2) to determine whether the former could predict the latter in mechanically ventilated rabbits with and without lung injury. The effects of tidal volume, ventilator frequency and type of lung injury on the gradient between PETCO2 and PaCO2 (delta P(a-ET)CO2) were evaluated. Twenty rabbits were studied: 10 without lung injury, 5 with saline lavage and 5 with lung injury by meconium instillation. Paired measurements of PETCO2 by two infrared capnometers and a mass spectrometer were compared to PaCO2. In the rabbits without lung injury, the values from the infrared capnometers and mass spectrometer correlated strongly with PaCO2 (r > or = 0.91) despite differences in the slopes of the linear regression between PETCO2 and PaCO2 and in delta P(a-ET)CO2 (P < 0.05). Values from the mainstream IR-capnometer more closely approximated the line of identity than the regression between the sidestream IR-capnometer values or the mass spectrometer and PaCO2, but tended to overestimate PaCO2. The delta P(a-ET)CO2 was similar at all tidal volumes and ventilator frequencies, regardless of capnometer type. In the rabbits with induced lung injury, while there was a positive correlation between the slopes of the regression between PETCO2 and PaCO2 for both capnometers (r > or = 0.70), none of the regression slopes approximated the line of identity. The delta P(a-ET)CO2 was greater in rabbits with injured than noninjured lungs (P < 0.05). The delta P(a-ET)CO2 was similar among capnometers regardless of tidal volume, ventilator frequency, or type of lung injury. The 95% confidence interval of plots PaCO2 against PETCO2 was large for rabbits with injured and noninjured lungs.(ABSTRACT TRUNCATED AT 250 WORDS)

Value and limitations of transpulmonary pressure calculations during intra-abdominal hypertension.

PubMed

Cortes-Puentes, Gustavo A; Gard, Kenneth E; Adams, Alexander B; Faltesek, Katherine A; Anderson, Christopher P; Dries, David J; Marini, John J

2013-08-01

To clarify the effect of progressively increasing intra-abdominal pressure on esophageal pressure, transpulmonary pressure, and functional residual capacity. Controlled application of increased intra-abdominal pressure at two positive end-expiratory pressure levels (1 and 10 cm H2O) in an anesthetized porcine model of controlled ventilation. Large animal laboratory of a university-affiliated hospital. Eleven deeply anesthetized swine (weight 46.2 ± 6.2 kg). Air-regulated intra-abdominal hypertension (0-25 mm Hg). Esophageal pressure, tidal compliance, bladder pressure, and end-expiratory lung aeration by gas dilution. Functional residual capacity was significantly reduced by increasing intra-abdominal pressure at both positive end-expiratory pressure levels (p ≤ 0.0001) without corresponding changes of end-expiratory esophageal pressure. Above intra-abdominal pressure 5 mm Hg, plateau airway pressure increased linearly by ~ 50% of the applied intra-abdominal pressure value, associated with commensurate changes of esophageal pressure. With tidal volume held constant, negligible changes occurred in transpulmonary pressure due to intra-abdominal pressure. Driving pressures calculated from airway pressures alone (plateau airway pressure--positive end-expiratory pressure) did not equate to those computed from transpulmonary pressure (tidal changes in transpulmonary pressure). Increasing positive end-expiratory pressure shifted the predominantly negative end-expiratory transpulmonary pressure at positive end-expiratory pressure 1 cm H2O (mean -3.5 ± 0.4 cm H2O) into the positive range at positive end-expiratory pressure 10 cm H2O (mean 0.58 ± 1.2 cm H2O). Despite its insensitivity to changes in functional residual capacity, measuring transpulmonary pressure may be helpful in explaining how different levels of positive end-expiratory pressure influence recruitment and collapse during tidal ventilation in the presence of increased intra-abdominal pressure and in calculating true transpulmonary driving pressure (tidal changes of transpulmonary pressure). Traditional interpretations of respiratory mechanics based on unmodified airway pressure were misleading regarding lung behavior in this setting.

Physiological and perceptual responses to incremental exercise testing in healthy men: effect of exercise test modality.

PubMed

Muscat, Kristina M; Kotrach, Houssam G; Wilkinson-Maitland, Courtney A; Schaeffer, Michele R; Mendonca, Cassandra T; Jensen, Dennis

2015-11-01

In a randomized cross-over study of 15 healthy men aged 20-30 years, we compared physiological and perceptual responses during treadmill and cycle exercise test protocols matched for increments in work rate - the source of increased locomotor muscle metabolic and contractile demands. The rates of O2 consumption and CO2 production were higher at the peak of treadmill versus cycle testing (p ≤ 0.05). Nevertheless, work rate, minute ventilation, tidal volume (VT), breathing frequency (fR), inspiratory capacity (IC), inspiratory reserve volume (IRV), tidal esophageal (Pes,tidal) and transdiaphragmatic pressure swings (Pdi,tidal), peak expiratory gastric pressures (Pga,peak), the root mean square of the diaphragm electromyogram (EMGdi,rms) expressed as a percentage of maximum EMGdi,rms (EMGdi,rms%max), and dyspnea ratings were similar at the peak of treadmill versus cycle testing (p > 0.05). Ratings of leg discomfort were higher at the peak of cycle versus treadmill exercise (p ≤ 0.05), even though peak O2 consumption was lower during cycling. Oxygen consumption, CO2 production, minute ventilation, fR, Pes,tidal, Pdi,tidal and Pga,peak were higher (p ≤ 0.05), while VT, IC, IRV, EMGdi,rms%max, and ratings of dyspnea and leg discomfort were similar (p > 0.05) at all or most submaximal work rates during treadmill versus cycle exercise. Our findings highlight important differences (and similarities) in physiological and perceptual responses at maximal and submaximal work rates during incremental treadmill and cycle exercise testing protocols. The lack of effect of exercise test modality on peak work rate advocates for the use of this readily available parameter to optimize training intensity determination, regardless of exercise training mode.

Computer Simulations of Deltas with Varying Fluvial Input and Tidal Forcing

NASA Astrophysics Data System (ADS)

Sun, T.

2015-12-01

Deltas are important depositional systems because many large hydrocarbon reservoirs in the world today are found in delta deposits. Deltas form when water and sediments carried by fluvial channels are emptied to an open body of water, and form delta shaped deposits. Depending on the relative importance of the physical processes that controls the forming and the growth of deltas, deltas can often be classified into three different types, namely fluvial, tidal and wave dominated delta. Many previous works, using examples from modern systems, tank experiments, outcrops, and 2 and 3D seismic data sets, have studied the shape, morphology and stratigraphic architectures corresponding to each of the deltas' types. However, few studies have focused on the change of these properties as a function of the relative change of the key controls, and most of the studies are qualitative. Here, using computer simulations, the dynamics of delta evolutions under an increasing amount of tidal influences are studied. The computer model used is fully based on the physics of fluid flow and sediment transport. In the model, tidal influences are taken into account by setting proper boundary conditions that varies both temporally and spatially. The model is capable of capturing many important natural geomorphic and sedimentary processes in fluvial and tidal systems, such as channel initiation, formation of channel levees, growth of mouth bars, bifurcation of channels around channel mouth bars, and channel avulsion. By systematically varying tidal range and fluvial input, the following properties are investigated quantitatively: (1) the presence and the form of tidal beds as a function of tidal range, (2) change of stratigraphic architecture of distributary channel mouth bars or tidal bars as tidal range changes, (3) the transport and sorting of different grainsizes and the overall facie distributions in the delta with different tidal ranges, and (4) the conditions and locations of mud drapes with different magnitude of tidal forcing.

High-resolution modeling assessment of tidal stream resource in Western Passage of Maine, USA

NASA Astrophysics Data System (ADS)

Yang, Zhaoqing; Wang, Taiping; Feng, Xi; Xue, Huijie; Kilcher, Levi

2017-04-01

Although significant efforts have been taken to assess the maximum potential of tidal stream energy at system-wide scale, accurate assessment of tidal stream energy resource at project design scale requires detailed hydrodynamic simulations using high-resolution three-dimensional (3-D) numerical models. Extended model validation against high quality measured data is essential to minimize the uncertainties of the resource assessment. Western Passage in the State of Maine in U.S. has been identified as one of the top ranking sites for tidal stream energy development in U.S. coastal waters, based on a number of criteria including tidal power density, market value and transmission distance. This study presents an on-going modeling effort for simulating the tidal hydrodynamics in Western Passage using the 3-D unstructured-grid Finite Volume Community Ocean Model (FVCOM). The model domain covers a large region including the entire the Bay of Fundy with grid resolution varies from 20 m in the Western Passage to approximately 1000 m along the open boundary near the mouth of Bay of Fundy. Preliminary model validation was conducted using existing NOAA measurements within the model domain. Spatial distributions of tidal power density were calculated and extractable tidal energy was estimated using a tidal turbine module embedded in FVCOM under different tidal farm scenarios. Additional field measurements to characterize resource and support model validation were discussed. This study provides an example of high resolution resource assessment based on the guidance recommended by the International Electrotechnical Commission Technical Specification.

On-Shore Central Hydraulic Power Generation for Wind and Tidal Energy

NASA Technical Reports Server (NTRS)

Jones, Jack A.; Bruce, Allan; Lim, Steven; Murray, Luke; Armstrong, Richard; Kimbrall, Richard; Cook-Chenault, Kimberly; DeGennaro, Sean

2012-01-01

Tidal energy, offshore wind energy, and onshore wind energy can be converted to electricity at a central ground location by means of converting their respective energies into high-pressure hydraulic flows that are transmitted to a system of generators by high-pressure pipelines. The high-pressure flows are then efficiently converted to electricity by a central power plant, and the low-pressure outlet flow is returned. The Department of Energy (DOE) is presently supporting a project led by Sunlight Photonics to demonstrate a 15 kW tidal hydraulic power generation system in the laboratory and possibly later submerged in the ocean. All gears and submerged electronics are completely eliminated. A second portion of this DOE project involves sizing and costing a 15 MW tidal energy system for a commercial tidal energy plant. For this task, Atlantis Resources Corporation s 18-m diameter demonstrated tidal blades are rated to operate in a nominal 2.6 m/sec tidal flow to produce approximately one MW per set of tidal blades. Fifteen units would be submerged in a deep tidal area, such as in Maine s Western Passage. All would be connected to a high-pressure (20 MPa, 2900 psi) line that is 35 cm ID. The high-pressure HEPG fluid flow is transported 500-m to on-shore hydraulic generators. HEPG is an environmentally-friendly, biodegradable, watermiscible fluid. Hydraulic adaptations to ORPC s cross-flow turbines are also discussed. For 15 MW of wind energy that is onshore or offshore, a gearless, high efficiency, radial piston pump can replace each set of top-mounted gear-generators. The fluid is then pumped to a central, easily serviceable generator location. Total hydraulic/electrical efficiency is 0.81 at full rated wind or tidal velocities and increases to 0.86 at 1/3 rated velocities.

On-Shore Central Hydraulic Power Generation for Wind and Tidal Energy

NASA Technical Reports Server (NTRS)

Jones, Jack A.; Bruce, Allan; Lim, Steven; Murray, Luke; Armstrong, Richard; Kimball, Richard; Cook-Chenault, Kimberly; DeGennaro, Sean

2012-01-01

Tidal energy, offshore wind energy, and onshore wind energy can be converted to electricity at a central ground location by means of converting their respective energies into high-pressure hydraulic flows that are transmitted to a system of generators by high-pressure pipelines. The high-pressure flows are then efficiently converted to electricity by a central power plant, and the low-pressure outlet flow is returned. The Department of Energy (DOE) is presently supporting a project led by Sunlight Photonics to demonstrate a 15 kilowatt tidal hydraulic power generation system in the laboratory and possibly later submerged in the ocean. All gears and submerged electronics are completely eliminated.A second portion of this DOE project involves sizing and costing a 15 megawatt tidal energy system for a commercial tidal energy plant. For this task, Atlantis Resources Corporation's 18-m diameter demonstrated tidal blades are rated to operate in a nominal 2.6 m/sec tidal flow to produce approximately one megawatt per set of tidal blades. Fifteen units would be submerged in a deep tidal area, such as in Maine's Western Passage. All would be connected to a high-pressure (20 megapascals, 2900 pounds per square inch) line that is 35 cm ID. The high-pressure HEPG fluid flow is transported 500-m to on-shore hydraulic generators. HEPG is an environmentally-friendly, biodegradable, water-miscible fluid. Hydraulic adaptations to ORPC's cross-flow turbines are also discussed.For 15 megawatt of wind energy that is onshore or offshore, a gearless, high efficiency, radial piston pump can replace each set of top-mounted gear-generators. The fluid is then pumped to a central, easily serviceable generator location. Total hydraulic/electrical efficiency is 0.81 at full rated wind or tidal velocities and increases to 0.86 at 1/3 rated velocities.

Contributions of organic and inorganic matter to sediment volume and accretion in tidal wetlands at steady state

EPA Science Inventory

A mixing model derived from first principles describes the bulk density (BD) of intertidal wetland sediments as a function of loss on ignition (LOI). The model assumes the bulk volume of sediment equates to the sum of self-packing volumes of organic and mineral components or BD =...

Titration of Ideal Positive End-expiratory Pressure in Acute Respiratory Distress Syndrome: Comparison between Lower Inflection Point and Esophageal Pressure Method Using Volumetric Capnography.

PubMed

Baikunje, Nandakishore; Sehgal, Inderpaul Singh; Dhooria, Sahajal; Prasad, Kuruswamy Thurai; Agarwal, Ritesh

2017-05-01

The tenets of mechanical ventilation in acute respiratory distress syndrome (ARDS) include the utilization of low tidal volume and optimal application of positive end-expiratory pressure (PEEP). Optimal PEEP in ARDS is characterized by reduction in alveolar dead space along with improvement in the lung compliance and resultant betterment in oxygenation. There are various methods of setting PEEP in ARDS. Herein, we report a patient of ARDS, wherein we employed measurement of dead space using volumetric capnography to compare two different PEEP strategies, namely, the lower inflection point and transpulmonary pressure monitoring.

Saltwater-freshwater mixing fluctuation in shallow beach aquifers

NASA Astrophysics Data System (ADS)

Han, Qiang; Chen, Daoyi; Guo, Yakun; Hu, Wulong

2018-07-01

Field measurements and numerical simulations demonstrate the existence of an upper saline plume in tidally dominated beaches. The effect of tides on the saltwater-freshwater mixing occurring at both the upper saline plume and lower salt wedge is well understood. However, it is poorly understood whether the tidal driven force acts equally on the mixing behaviours of above two regions and what factors control the mixing fluctuation features. In this study, variable-density, saturated-unsaturated, transient groundwater flow and solute transport numerical models are proposed and performed for saltwater-freshwater mixing subject to tidal forcing on a sloping beach. A range of tidal amplitude, fresh groundwater flux, hydraulic conductivity, beach slope and dispersivity anisotropy are simulated. Based on the time sequential salinity data, the gross mixing features are quantified by computing the spatial moments in three different aspects, namely, the centre point, length and width, and the volume (or area in a two-dimensional case). Simulated salinity distribution varies significantly at saltwater-freshwater interfaces. Mixing characteristics of the upper saline plume greatly differ from those in the salt wedge for both the transient and quasi-steady state. The mixing of the upper saline plume largely inherits the fluctuation characteristics of the sea tide in both the transverse and longitudinal directions when the quasi-steady state is reached. On the other hand, the mixing in the salt wedge is relatively steady and shows little fluctuation. The normalized mixing width and length, mixing volume and the fluctuation amplitude of the mass centre in the upper saline plume are, in general, one-magnitude-order larger than those in the salt wedge region. In the longitudinal direction, tidal amplitude, fresh groundwater flux, hydraulic conductivity and beach slope are significant control factors of fluctuation amplitude. In the transverse direction, tidal amplitude and beach slope are the main control parameters. Very small dispersivity anisotropy (e.g., αL /αT < 5) could greatly suppress mixing fluctuation in the longitudinal direction. This work underlines the close connection between the sea tides and the upper saline plume in the aspect of mixing, thereby enhancing understanding of the interplay between tidal oscillations and mixing mechanisms in tidally dominated sloping beach systems.

Intraoperative protective mechanical ventilation for prevention of postoperative pulmonary complications: a comprehensive review of the role of tidal volume, positive end-expiratory pressure, and lung recruitment maneuvers.

PubMed

Güldner, Andreas; Kiss, Thomas; Serpa Neto, Ary; Hemmes, Sabrine N T; Canet, Jaume; Spieth, Peter M; Rocco, Patricia R M; Schultz, Marcus J; Pelosi, Paolo; Gama de Abreu, Marcelo

2015-09-01

Postoperative pulmonary complications are associated with increased morbidity, length of hospital stay, and mortality after major surgery. Intraoperative lung-protective mechanical ventilation has the potential to reduce the incidence of postoperative pulmonary complications. This review discusses the relevant literature on definition and methods to predict the occurrence of postoperative pulmonary complication, the pathophysiology of ventilator-induced lung injury with emphasis on the noninjured lung, and protective ventilation strategies, including the respective roles of tidal volumes, positive end-expiratory pressure, and recruitment maneuvers. The authors propose an algorithm for protective intraoperative mechanical ventilation based on evidence from recent randomized controlled trials.

Respiratory response to microinjections of GABA and penicillin into various parts of the ventral respiratory group.

PubMed

Vedyasova, O A; Kovalyov, A M

2012-06-01

Experiments on rats showed that local injection of GABA (10(-4) M) into the rostral and caudal compartments of the ventral respiratory groups decreased the respiratory rhythm, but increased lung ventilation (especially injection into the rostral part). Penicillin (10(-7) M) injected into the rostral division increased the tidal volume and practically did not change the respiratory rate, but its injection into the caudal part reduced the tidal volume and increased respiratory rate. These results indicate that GABAergic mechanisms including GABA(A) sites play an ambiguous role in the regulation of respiration at the level of the rostral and caudal parts of the ventral respiratory group.

High tidal volume ventilation in infant mice.

PubMed

Cannizzaro, Vincenzo; Zosky, Graeme R; Hantos, Zoltán; Turner, Debra J; Sly, Peter D

2008-06-30

Infant mice were ventilated with either high tidal volume (V(T)) with zero end-expiratory pressure (HVZ), high V(T) with positive end-expiratory pressure (PEEP) (HVP), or low V(T) with PEEP. Thoracic gas volume (TGV) was determined plethysmographically and low-frequency forced oscillations were used to measure the input impedance of the respiratory system. Inflammatory cells, total protein, and cytokines in bronchoalveolar lavage fluid (BALF) and interleukin-6 (IL-6) in serum were measured as markers of pulmonary and systemic inflammatory response, respectively. Coefficients of tissue damping and tissue elastance increased in all ventilated mice, with the largest rise seen in the HVZ group where TGV rapidly decreased. BALF protein levels increased in the HVP group, whereas serum IL-6 rose in the HVZ group. PEEP keeps the lungs open, but provides high volumes to the entire lungs and induces lung injury. Compared to studies in adult and non-neonatal rodents, infant mice demonstrate a different response to similar ventilation strategies underscoring the need for age-specific animal models.

Dynamic Determination of Oxygenation and Lung Compliance in Murine Pneumonectomy

PubMed Central

Gibney, Barry; Lee, Grace S.; Houdek, Jan; Lin, Miao; Miele, Lino; Chamoto, Kenji; Konerding, Moritz A.; Tsuda, Akira; Mentzer, Steven J.

2012-01-01

Thoracic surgical procedures in mice have been applied to a wide range of investigations, but little is known about the murine physiologic response to pulmonary surgery. Using continuous arterial oximetry monitoring and the FlexiVent murine ventilator, we investigated the effect of anesthesia and pneumonectomy on mouse oxygen saturation and lung mechanics. Sedation resulted in a dose-dependent decline of oxygen saturation that ranged from 55–82%. Oxygen saturation was restored by mechanical ventilation with increased rate and tidal volumes. In the mouse strain studied, optimal ventilatory rates were a rate of 200/minute and a tidal volume of 10ml/kg. Sustained inflation pressures, referred to as a "recruitment maneuver," improved lung volumes, lung compliance and arterial oxygenation. In contrast, positive end expiratory pressure (PEEP) had a detrimental effect on oxygenation; an effect that was ameliorated after pneumonectomy. Our results confirm that lung volumes in the mouse are dynamically determined and suggest a threshold level of mechanical ventilation to maintain perioperative oxygen saturation. PMID:21574875

Accuracy of stroke volume variation in predicting fluid responsiveness: a systematic review and meta-analysis.

PubMed

Zhang, Zhongheng; Lu, Baolong; Sheng, Xiaoyan; Jin, Ni

2011-12-01

Stroke volume variation (SVV) appears to be a good predictor of fluid responsiveness in critically ill patients. However, a wide range of its predictive values has been reported in recent years. We therefore undertook a systematic review and meta-analysis of clinical trials that investigated the diagnostic value of SVV in predicting fluid responsiveness. Clinical investigations were identified from several sources, including MEDLINE, EMBASE, WANFANG, and CENTRAL. Original articles investigating the diagnostic value of SVV in predicting fluid responsiveness were considered to be eligible. Participants included critically ill patients in the intensive care unit (ICU) or operating room (OR) who require hemodynamic monitoring. A total of 568 patients from 23 studies were included in our final analysis. Baseline SVV was correlated to fluid responsiveness with a pooled correlation coefficient of 0.718. Across all settings, we found a diagnostic odds ratio of 18.4 for SVV to predict fluid responsiveness at a sensitivity of 0.81 and specificity of 0.80. The SVV was of diagnostic value for fluid responsiveness in OR or ICU patients monitored with the PiCCO or the FloTrac/Vigileo system, and in patients ventilated with tidal volume greater than 8 ml/kg. SVV is of diagnostic value in predicting fluid responsiveness in various settings.

Limited Influence of Urban Stormwater Runoff on Salt Marsh Platform and Marsh Creek Oxygen Dynamics in Coastal Georgia.

PubMed

Savidge, William B; Brink, Jonathan; Blanton, Jackson O

2016-12-01

Oxygen concentrations and oxygen utilization rates were monitored continuously for 23 months on marsh platforms and in small tidal creeks at two sites in coastal Georgia, USA, that receive urban stormwater runoff via an extensive network of drainage canals. These data were compared to nearby control sites that receive no significant surface runoff. Overall, rainfall and runoff per se were not associated with differences in the oxygen dynamics among the different locations. Because of the large tidal range and long tidal excursions in coastal Georgia, localized inputs of stormwater runoff are rapidly mixed with large volumes of ambient water. Oxygen concentrations in tidal creeks and on flooded marsh platforms were driven primarily by balances of respiration and photosynthesis in the surrounding regional network of marshes and open estuarine waters. Local respiration, while measurable, was of relatively minor importance in determining oxygen concentrations in tidal floodwaters. Water residence time on the marshes could explain differences in oxygen concentration between the runoff-influenced and control sites.

Limited Influence of Urban Stormwater Runoff on Salt Marsh Platform and Marsh Creek Oxygen Dynamics in Coastal Georgia

NASA Astrophysics Data System (ADS)

Savidge, William B.; Brink, Jonathan; Blanton, Jackson O.

2016-12-01

Oxygen concentrations and oxygen utilization rates were monitored continuously for 23 months on marsh platforms and in small tidal creeks at two sites in coastal Georgia, USA, that receive urban stormwater runoff via an extensive network of drainage canals. These data were compared to nearby control sites that receive no significant surface runoff. Overall, rainfall and runoff per se were not associated with differences in the oxygen dynamics among the different locations. Because of the large tidal range and long tidal excursions in coastal Georgia, localized inputs of stormwater runoff are rapidly mixed with large volumes of ambient water. Oxygen concentrations in tidal creeks and on flooded marsh platforms were driven primarily by balances of respiration and photosynthesis in the surrounding regional network of marshes and open estuarine waters. Local respiration, while measurable, was of relatively minor importance in determining oxygen concentrations in tidal floodwaters. Water residence time on the marshes could explain differences in oxygen concentration between the runoff-influenced and control sites.

The Effects of the Impedance of the Flow Source on the Design of Tidal Stream Generators

NASA Astrophysics Data System (ADS)

Salter, S.

2011-12-01

The maximum performance of a wind turbine is set by the well-known Betz limit. If the designer of a wind turbine uses too fast a rotation, too large a blade chord or too high an angle of blade pitch, the air flow can take an easier path over or around the rotor. Most estimates of the tidal stream resource use equations borrowed from wind and would be reasonably accurate for a single unit. But water cannot flow through the seabed or over rotors which reach to the surface. If contra-rotating, vertical-axis turbines with a rectangular flow-window are placed close to one another and reach from the surface close to the seabed, the leakage path is blocked and they become more like turbines in a closed duct. Instead of an equation with area times velocity-cubed we should use the first power of volume flow rate though the rotor times the pressure difference across it. A long channel with a rough bed will already be losing lots of energy and will behave more like a high impedance flow. Attempts to block it with closely-packed turbines will increase the head across the turbines with only a small effect on flow rate. The same thing will occur if a close-packed line of turbines is built out to sea from a headland. It is necessary to understand the impedance of the flow source all the way out to mid-ocean. In deep seas where the current velocities at the seabed are too slow to disturb the ooze the friction coefficients will be similar to those of gloss paint, perhaps 0.0025. But the higher velocities in shallow water will remove ooze and quite large sediments leaving rough, bare rock and leading to higher friction-coefficients. Energy dissipation will be set by the higher friction coefficients and the cube of the higher velocities. The presence of turbines will reduce seabed losses and about one third of the present loss can be converted to electricity. The velocity reduction would be about 10%. In many sites the energy output will be far higher than the wind turbine equations would predict. It may be possible to measure friction coefficients by looking at the slope of the water across a likely tidal stream site as indicated by the pressure-sensing instruments built in to acoustic Doppler current profilers. If this reasoning is correct it would lead to large changes in turbine design for tidal streams particularly with regard to the very large forces which have to be passed into the seabed. The spacing of three rotor diameters, often recommended for tidal stream turbines becomes the equivalent of leaking pipes in conventional hydro-electric plant. These design changes will be discussed. Reference Salter SH. Correcting the Under-estimate of the Tidal-Stream Resource of the Pentland Firth. 8th European Wave and Tidal Energy Conference, Uppsala 2009 From www.see.ed.ac.uk/~shs then browse to /Tidal stream.

Role of central and peripheral opiate receptors in the effects of fentanyl on analgesia, ventilation and arterial blood-gas chemistry in conscious rats.

PubMed

Henderson, Fraser; May, Walter J; Gruber, Ryan B; Discala, Joseph F; Puskovic, Veljko; Young, Alex P; Baby, Santhosh M; Lewis, Stephen J

2014-01-15

This study determined the effects of the peripherally restricted μ-opiate receptor (μ-OR) antagonist, naloxone methiodide (NLXmi) on fentanyl (25μg/kg, i.v.)-induced changes in (1) analgesia, (2) arterial blood gas chemistry (ABG) and alveolar-arterial gradient (A-a gradient), and (3) ventilatory parameters, in conscious rats. The fentanyl-induced increase in analgesia was minimally affected by a 1.5mg/kg of NLXmi but was attenuated by a 5.0mg/kg dose. Fentanyl decreased arterial blood pH, pO2 and sO2 and increased pCO2 and A-a gradient. These responses were markedly diminished in NLXmi (1.5mg/kg)-pretreated rats. Fentanyl caused ventilatory depression (e.g., decreases in tidal volume and peak inspiratory flow). Pretreatment with NLXmi (1.5mg/kg, i.v.) antagonized the fentanyl decrease in tidal volume but minimally affected the other responses. These findings suggest that (1) the analgesia and ventilatory depression caused by fentanyl involve peripheral μ-ORs and (2) NLXmi prevents the fentanyl effects on ABG by blocking the negative actions of the opioid on tidal volume and A-a gradient. Copyright © 2013 Elsevier B.V. All rights reserved.

Closed-loop mechanical ventilation for lung injury: a novel physiological-feedback mode following the principles of the open lung concept.

PubMed

Schwaiberger, David; Pickerodt, Philipp A; Pomprapa, Anake; Tjarks, Onno; Kork, Felix; Boemke, Willehad; Francis, Roland C E; Leonhardt, Steffen; Lachmann, Burkhard

2018-06-01

Adherence to low tidal volume (V T ) ventilation and selected positive end-expiratory pressures are low during mechanical ventilation for treatment of the acute respiratory distress syndrome. Using a pig model of severe lung injury, we tested the feasibility and physiological responses to a novel fully closed-loop mechanical ventilation algorithm based on the "open lung" concept. Lung injury was induced by surfactant washout in pigs (n = 8). Animals were ventilated following the principles of the "open lung approach" (OLA) using a fully closed-loop physiological feedback algorithm for mechanical ventilation. Standard gas exchange, respiratory- and hemodynamic parameters were measured. Electrical impedance tomography was used to quantify regional ventilation distribution during mechanical ventilation. Automatized mechanical ventilation provided strict adherence to low V T -ventilation for 6 h in severely lung injured pigs. Using the "open lung" approach, tidal volume delivery required low lung distending pressures, increased recruitment and ventilation of dorsal lung regions and improved arterial blood oxygenation. Physiological feedback closed-loop mechanical ventilation according to the principles of the open lung concept is feasible and provides low tidal volume ventilation without human intervention. Of importance, the "open lung approach"-ventilation improved gas exchange and reduced lung driving pressures by opening atelectasis and shifting of ventilation to dorsal lung regions.

Transdiaphragmatic pressure in quadriplegic individuals ventilated by diaphragmatic pacemaker.

PubMed Central

Garrido-García, H.; Martín-Escribano, P.; Palomera-Frade, J.; Arroyo, O.; Alonso-Calderón, J. L.; Mazaira-Alvarez, J.

1996-01-01

BACKGROUND: Electrophrenic pacing can be used in the management of ventilatory failure in quadriplegic patients. A study was undertaken to determine the pattern of transdiaphragmatic pressure (PDI) during the conditioning phase of electrophrenic pacing to see if it had a possible role in optimising the process of conditioning. METHODS: The tidal volume (TV) and PDI were measured in a group of six quadriplegic patients commencing ventilation by low frequency pulse stimulation (7-10 Hz) and low respiratory rate stimulation (< 10 breaths/min). RESULTS: Tidal volume increased between baseline and month 1 (4.33 ml/kg, p < 0.001) and between months 1 and 2 (3.00 ml/kg, p < 0.05) and then stabilised. PDI was higher during bilateral diaphragmatic pacing (mean (SD) 1.73 (0.30) kPa) than with either left (1.15 (0.34) kPa) or right (0.86 (0.37) kPa) unilateral pacing. PDI varied throughout the observation period, probably by interaction between recovery of the diaphragmatic fibres and the pacing regimen. CONCLUSIONS: Patients with quadriplegia due to high spinal injury can be maintained with ventilation by continuous electrophrenic pacing. The control criteria used in this study for pacing were tidal volume and the patient's tolerance, and the PDI measurement did not contribute any additional information to help with managing the conditioning process. PMID:8733497

Inhalation of substance P and thiorphan: acute toxicity and effects on respiration in conscious guinea pigs.

PubMed

Koch, B L; Edvinsson, A A; Koskinen, L O

1999-01-01

Substance P is a tachykinin and a biologically active neuropeptide. The peptide produces salivation, neuronal excitation, vasodilatation, increased vascular permeability and contraction of smooth muscles in the respiratory tract. The study was designed to evaluate the acute effects in guinea pigs of inhaled aerosolized Substance P (SP). Apart from the acute toxic effect of the peptide, the distribution in different organs was also investigated. The acute inhalation toxicity of SP (LC50, 15 min) when co-administrated with the neutral endopeptidase inhibitor thiorphan was 368 microg m(-3). The peptide caused an increase in respiratory rate proceeding a decrease in tidal volume. As the exposure proceeded, a decrease in both respiratory rate and further decreases in tidal volume were observed until either the animal died or the exposure was terminated. The decreases in respiratory rate and tidal volume were probably due to bronchoconstriction caused by SP. Eighteen per cent of the inhaled amount of radioactive SP was retained in the body, and the highest concentrations of radioactivity were found in the kidney, lung and liver. Substance P in combination with thiorphan administered as an aerosol is extremely toxic and highly potent. Exposure to the substance at extremely low air concentrations may result in incapacitation in humans.

Effect of the laryngeal tube on the no-flow-time in a simulated two rescuer basic life support setting with inexperienced users.

PubMed

Schröder, J; Bucher, M; Meyer, O

2016-09-01

Intubation with a laryngeal tube (LT) is a recommended alternative to endotracheal intubation during advanced life support (ALS). LT insertion is easy; therefore, it may also be an alternative to bag-mask ventilation (BMV) for untrained personnel performing basic life support (BLS). Data from manikin studies support the influence of LT on no-flow-time (NFT) during ALS. We performed a prospective, randomized manikin study using a two-rescuer model to compare the effects of ventilation using a LT and BMV on NFT during BLS. Participants were trained in BMV and were inexperienced in the use of a LT. There was no significant difference in total NFT with the use of a LT and BMV (LT: mean 83.1 ± 37.3 s; BMV: mean 78.7 ± 24.5 s; p = 0.313), but we found significant differences in the progression of the scenario: in the BLS-scenario, the proportion of time spent performing chest compressions was higher when BMV was used compared to when a LT was used. The quality of chest compressions and the ventilation rate did not differ significantly between the two groups. The mean tidal volume and mean minute volume were significantly larger with the use of a LT compared with the use of BMV. In conclusion, in a two-rescuer BLS scenario, NFT is longer with the use of a LT (without prior training) than with the use of BMV (with prior training). The probable reasons for this result are higher tidal volumes with the use of a LT leading to longer interruptions without chest compressions.

A randomized comparison of different ventilator strategies during thoracotomy for pulmonary resection.

PubMed

Maslow, Andrew D; Stafford, Todd S; Davignon, Kristopher R; Ng, Thomas

2013-07-01

Protective lung ventilation is reported to benefit patients with acute respiratory distress syndrome. It is not known whether protective lung ventilation is also beneficial to patients undergoing single-lung ventilation for elective pulmonary resection. In an institutional review board-approved prospective randomized trial, 34 patients undergoing elective pulmonary resection requiring single-lung ventilation were enrolled. Informed consent was obtained. Patients were randomized to 1 of 2 groups: (1) high tidal volume (Hi-TV) of 10 mL/kg, rate of 7 breaths/min, and zero positive end-expiratory pressure or (2) low tidal volume (Lo-TV) of 5 mL/kg, rate of 14 breaths/min, and 5 cmH2O positive end-expiratory pressure. Ventilator settings were continued during both double- and single-lung ventilation. Pulmonary functions, hemodynamics, and postoperative outcomes were recorded. Patient demographics, operative characteristics, intraoperative hemodynamics, and postoperative pain and sedation scores were similar between the 2 groups. During most time periods, airway pressures (peak and plateau) were significantly higher in the Hi-TV group; however, plateau pressures remained less than 30 cmH2O at all times for all patients. The Hi-TV group had significantly lower arterial carbon dioxide tension, less arterial carbon dioxide tension-end-tidal carbon dioxide gradient, lower alveolar dead space ratio, and higher dynamic pulmonary compliance. There were no differences in postoperative morbidity and hospital days between the 2 groups, but atelectasis scores on postoperative days 1 and 2 were lower in the Hi-TV group. The use of Hi-TV during single-lung ventilation for pulmonary resection resulted in no increase in morbidity and was associated with less hypercarbia, less dead space ventilation, better dynamic compliance, and less postoperative atelectasis. Copyright © 2013 The American Association for Thoracic Surgery. Published by Mosby, Inc. All rights reserved.

Tidal triggering of moonquakes.

NASA Technical Reports Server (NTRS)

Hamilton, W. L.

1972-01-01

It is argued that the moonquakes recorded by sensors at the Apollo 12 landing site between December 1969 and December 1970, and which according to Latham et al. (1971) are believed to be triggered by the anomalistic lunar tide, could be triggered just as well by the latitudinal (or declination) tidal wave. Considerations are set forth which indicate that a combined latitudinal-anomalistic tidal mechanism is supported by Latham's data.

Respiration in neonate sea turtles.

PubMed

Price, Edwin R; Paladino, Frank V; Strohl, Kingman P; Santidrián T, Pilar; Klann, Kenneth; Spotila, James R

2007-03-01

The pattern and control of respiration is virtually unknown in hatchling sea turtles. Using incubator-raised turtles, we measured oxygen consumption, frequency, tidal volume, and minute volume for leatherback (Dermochelys coriacea) and olive ridley (Lepidochelys olivacea) turtle hatchlings for the first six days after pipping. In addition, we tested the hatchlings' response to hypercapnic, hyperoxic, and hypoxic challenges over this time period. Hatchling sea turtles generally showed resting ventilation characteristics that are similar to those of adults: a single breath followed by a long respiratory pause, slow frequency, and high metabolic rate. With hypercapnic challenge, both species responded primarily by elevating respiratory frequency via a decrease in the non-ventilatory period. Leatherback resting tidal volume increased with age but otherwise, neither species' resting respiratory pattern nor response to gas challenge changed significantly over the first few days after hatching. At the time of nest emergence, sea turtles have achieved a respiratory pattern that is similar to that of actively diving adults.

Physiological responses of mules on prolonged exposure to high altitude (3 650 m)

NASA Astrophysics Data System (ADS)

Riar, S. S.; Shankar Bhat, K.; Sen Gupta, J.

1982-06-01

Eight healthy male animals were inducted and kept for 2 1/2 years at 3 650 m altitude and subjected to normal work schedules. Physiological measurements viz. heart rate, blood pressure, minute ventilation, oxygen consumption, respiration rate, hemoglobin, packed cell haematocrit volume and eosinophil count were made on these animals at periodic intervals. On acute induction to an altitude of 3 650 m these animals demonstrated a sudden increase in tidal volume, a decrease in Rf and no change in VE, suggesting a decreased dead space/tidal volume ratio at altitude. However, all these changes stabilised within 3 weeks but on prolongation of stay, the physical state of these animals was adversely affected. The respiratory adjustments occurring on return to sea level appear to be a response to thermal stress. The initial increase in heart rate and blood pressure stabilised by the 2nd week.

The effect of lagoons on Adriatic Sea tidal dynamics

NASA Astrophysics Data System (ADS)

Ferrarin, Christian; Maicu, Francesco; Umgiesser, Georg

2017-11-01

In this study the effects that lagoons exert on the barotropic tidal dynamics of a regional sea, the Adriatic Sea, were numerically explored. This semi-enclosed basin is one of the places with the highest tidal range in the Mediterranean Sea and is characterised by the presence of several lagoons in its northern part. The tidal dynamics of a system comprising the whole Adriatic Sea and the lagoons of Venice, Marano-Grado and Po Delta were investigated using an unstructured hydrodynamic model. Numerical experiments with and without lagoons reveal that even if the considered shallow water bodies represent only the 0.5 and 0.002% of the Adriatic Sea surface and volume, respectively, they significantly affect the entire Northern Adriatic Sea tidal dynamics by enhancing tidal range (by 5%) and currents (by 10%). The inclusion of lagoons in the computation improved the model performance by 25% in reproducing tidal constituents in the Adriatic Sea. The back-effect of the lagoons on the open-sea tide is due to the waves radiating from the co-oscillating lagoons into the adjacent sea. This is the first time these processes are shown to be relevant for the Adriatic Sea, thus enhancing the understanding of the tidal dynamics in this regional sea. These findings may also apply to other coastal seas with connections to lagoons, bays and estuaries.

The respiratory system during resuscitation: a review of the history, risk of infection during assisted ventilation, respiratory mechanics, and ventilation strategies for patients with an unprotected airway.

PubMed

Wenzel, V; Idris, A H; Dörges, V; Nolan, J P; Parr, M J; Gabrielli, A; Stallinger, A; Lindner, K H; Baskett, P J

2001-05-01

The fear of acquiring infectious diseases has resulted in reluctance among healthcare professionals and the lay public to perform mouth-to-mouth ventilation. However, the benefit of basic life support for a patient in cardiopulmonary or respiratory arrest greatly outweighs the risk for secondary infection in the rescuer or the patient. The distribution of ventilation volume between lungs and stomach in the unprotected airway depends on patient variables such as lower oesophageal sphincter pressure, airway resistance and respiratory system compliance, and the technique applied while performing basic or advanced airway support, such as head position, inflation flow rate and time, which determine upper airway pressure. The combination of these variables determines gas distribution between the lungs and the oesophagus and subsequently, the stomach. During bag-valve-mask ventilation of patients in respiratory or cardiac arrest with oxygen supplementation (> or = 40% oxygen), a tidal volume of 6-7 ml kg(-1) ( approximately 500 ml) given over 1-2 s until the chest rises is recommended. For bag-valve-mask ventilation with room-air, a tidal volume of 10 ml kg(-1) (700-1000 ml) in an adult given over 2 s until the chest rises clearly is recommended. During mouth-to-mouth ventilation, a breath over 2 s sufficient to make the chest rise clearly (a tidal volume of approximately 10 ml kg(-1) approximately 700-1000 ml in an adult) is recommended.

Mask versus Nasal Tube for Stabilization of Preterm Infants at Birth: Respiratory Function Measurements.

PubMed

van Vonderen, Jeroen J; Kamlin, C Omar; Dawson, Jennifer A; Walther, Frans J; Davis, Peter G; te Pas, Arjan B

2015-07-01

To compare the nasal tube with face mask as interfaces for stabilization of very preterm infants at birth by using physiological measurements of leak, obstruction, and expired tidal volumes during positive pressure ventilation (PPV). In the delivery room, 43 infants <30 weeks gestation were allocated to receive respiratory support by nasal tube or face mask. Respiratory function, heart rate, and oxygen saturation were measured. Occurrence of obstruction, amount of leak, and tidal volumes were compared using a Mann-Whitney U test or a Fisher exact test. The first 5 minutes after initiation of PPV were analyzed (1566 inflations in the nasal tube group and 1896 inflations in the face mask group). Spontaneous breathing coincided with PPV in 32% of nasal tube and 34% of face mask inflations. During inflations, higher leak was observed using nasal tube compared with face mask (98% [33%-100%] vs 14 [0%-39%]; P < .0001). Obstruction occurred more often (8.2% vs 1.1%; P < .0001). Expired tidal volumes were significantly lower during inflations when using nasal tube compared with face mask (0.0 [0.0-3.1] vs 9.9 [5.5-12.8] mL/kg; P < .0001) and when spontaneous breathing coincided with PPV (4.4 [2.1-8.4] vs 9.6 [5.4-15.2] mL/kg; P < .0001) but were similar during breathing on continuous positive airway pressure (4.7 [2.8-6.9] vs 4.8 [2.7-7.9] mL/kg; P > 0.05). Heart rate was not significantly different between groups, but oxygen saturation was significantly lower in the nasal tube group the first 2 minutes after start of respiratory support. The use of a nasal tube led to large leak, more obstruction, and inadequate tidal volumes compared with face mask. Trial registration Registered with the Dutch Trial Registry (NTR 2061) and the Australia and New Zealand Clinical Trials Register (ACTRN 12610000230055). Copyright © 2015 Elsevier Inc. All rights reserved.

Pulse pressure variation and prediction of fluid responsiveness in patients ventilated with low tidal volumes.

PubMed

Oliveira-Costa, Clarice Daniele Alves de; Friedman, Gilberto; Vieira, Sílvia Regina Rios; Fialkow, Léa

2012-07-01

To determine the utility of pulse pressure variation (ΔRESP PP) in predicting fluid responsiveness in patients ventilated with low tidal volumes (V T) and to investigate whether a lower ΔRESP PP cut-off value should be used when patients are ventilated with low tidal volumes. This cross-sectional observational study included 37 critically ill patients with acute circulatory failure who required fluid challenge. The patients were sedated and mechanically ventilated with a V T of 6-7 ml/kg ideal body weight, which was monitored with a pulmonary artery catheter and an arterial line. The mechanical ventilation and hemodynamic parameters, including ΔRESP PP, were measured before and after fluid challenge with 1,000 ml crystalloids or 500 ml colloids. Fluid responsiveness was defined as an increase in the cardiac index of at least 15%. ClinicalTrial.gov: NCT01569308. A total of 17 patients were classified as responders. Analysis of the area under the ROC curve (AUC) showed that the optimal cut-off point for ΔRESP PP to predict fluid responsiveness was 10% (AUC = 0.74). Adjustment of the ΔRESP PP to account for driving pressure did not improve the accuracy (AUC = 0.76). A ΔRESP PP ≥ 10% was a better predictor of fluid responsiveness than central venous pressure (AUC = 0.57) or pulmonary wedge pressure (AUC = 051). Of the 37 patients, 25 were in septic shock. The AUC for ΔRESP PP ≥ 10% to predict responsiveness in patients with septic shock was 0.484 (sensitivity, 78%; specificity, 93%). The parameter D RESP PP has limited value in predicting fluid responsiveness in patients who are ventilated with low tidal volumes, but a ΔRESP PP>10% is a significant improvement over static parameters. A ΔRESP PP ≥ 10% may be particularly useful for identifying responders in patients with septic shock.

Recurrent Recruitment Manoeuvres Improve Lung Mechanics and Minimize Lung Injury during Mechanical Ventilation of Healthy Mice

PubMed Central

Reiss, Lucy Kathleen; Kowallik, Anke; Uhlig, Stefan

2011-01-01

Introduction Mechanical ventilation (MV) of mice is increasingly required in experimental studies, but the conditions that allow stable ventilation of mice over several hours have not yet been fully defined. In addition, most previous studies documented vital parameters and lung mechanics only incompletely. The aim of the present study was to establish experimental conditions that keep these parameters within their physiological range over a period of 6 h. For this purpose, we also examined the effects of frequent short recruitment manoeuvres (RM) in healthy mice. Methods Mice were ventilated at low tidal volume VT = 8 mL/kg or high tidal volume VT = 16 mL/kg and a positive end-expiratory pressure (PEEP) of 2 or 6 cmH2O. RM were performed every 5 min, 60 min or not at all. Lung mechanics were followed by the forced oscillation technique. Blood pressure (BP), electrocardiogram (ECG), heart frequency (HF), oxygen saturation and body temperature were monitored. Blood gases, neutrophil-recruitment, microvascular permeability and pro-inflammatory cytokines in bronchoalveolar lavage (BAL) and blood serum as well as histopathology of the lung were examined. Results MV with repetitive RM every 5 min resulted in stable respiratory mechanics. Ventilation without RM worsened lung mechanics due to alveolar collapse, leading to impaired gas exchange. HF and BP were affected by anaesthesia, but not by ventilation. Microvascular permeability was highest in atelectatic lungs, whereas neutrophil-recruitment and structural changes were strongest in lungs ventilated with high tidal volume. The cytokines IL-6 and KC, but neither TNF nor IP-10, were elevated in the BAL and serum of all ventilated mice and were reduced by recurrent RM. Lung mechanics, oxygenation and pulmonary inflammation were improved by increased PEEP. Conclusions Recurrent RM maintain lung mechanics in their physiological range during low tidal volume ventilation of healthy mice by preventing atelectasis and reduce the development of pulmonary inflammation. PMID:21935418

Mechanical ventilation with high tidal volume induces inflammation in patients without lung disease.

PubMed

Pinheiro de Oliveira, Roselaine; Hetzel, Marcio Pereira; dos Anjos Silva, Mauro; Dallegrave, Daniele; Friedman, Gilberto

2010-01-01

Mechanical ventilation (MV) with high tidal volumes may induce or aggravate lung injury in critical ill patients. We compared the effects of a protective versus a conventional ventilatory strategy, on systemic and lung production of tumor necrosis factor-alpha (TNF-alpha) and interleukin-8 (IL-8) in patients without lung disease. Patients without lung disease and submitted to mechanical ventilation admitted to one trauma and one general adult intensive care unit of two different university hospitals were enrolled in a prospective randomized-control study. Patients were randomized to receive MV either with tidal volume (VT) of 10 to 12 ml/kg predicted body weight (high VT group) (n = 10) or with VT of 5 to 7 ml/kg predicted body weight (low VT group) (n = 10) with an oxygen inspiratory fraction (FIO2) enough to keep arterial oxygen saturation >90% with positive end-expiratory pressure (PEEP) of 5 cmH2O during 12 hours after admission to the study. TNF-alpha and IL-8 concentrations were measured in the serum and in the bronchoalveolar lavage fluid (BALF) at admission and after 12 hours of study observation time. Twenty patients were enrolled and analyzed. At admission or after 12 hours there were no differences in serum TNF-alpha and IL-8 between the two groups. While initial analysis did not reveal significant differences, standardization against urea of logarithmic transformed data revealed that TNF-alpha and IL-8 levels in bronchoalveolar lavage (BAL) fluid were stable in the low VT group but increased in the high VT group (P = 0.04 and P = 0.03). After 12 hours, BALF TNF-alpha (P = 0.03) and BALF IL-8 concentrations (P = 0.03) were higher in the high VT group than in the low VT group. The use of lower tidal volumes may limit pulmonary inflammation in mechanically ventilated patients even without lung injury. NCT00935896.

A Permo-Carboniferous tide-storm interactive system: Talchir formation, Raniganj Basin, India

NASA Astrophysics Data System (ADS)

Bhattacharya, H. N.; Bhattacharya, Biplab

2006-08-01

Sandstone/siltstone-mudstone interbedded facies of the Permo-Carboniferous Talchir formation, Gondwana Supergroup, is exposed in the Raniganj Basin and records the activities of tidal currents in a terminoglacial, storm-influenced shallow marine setting. Tidal bundles of various types with pause plane drapes, evidence of time-velocity asymmetry and rare bidirectional current flow patterns are indicative of tidal activity. Chance preservation of such structures from storm reworking might have occurred due to dampening of storm waves on the low-gradient muddy substrate of the tidal flat. The tide-generated stratifications are draped by over-thickened muddy-siltstone with wavy/hummocky laminations. Increased suspended sediment concentrations following a storm yielded such thick mudstone drapes. Thin beds containing tidal structures indicate poor sediment supply in a blind tidal embayment.

[Lung protective ventilation - pathophysiology and diagnostics].

PubMed

Uhlig, Stefan; Frerichs, Inéz

2008-06-01

Mechanical ventilation may lead to lung injury depending on the ventilatory settings (e.g. pressure amplitudes, endexpiratory pressures, frequency) and the length of mechanical ventilation. Particularly in the inhomogeneously injured lungs of ARDS patients, alveolar overextension results in volutrauma, cyclic opening and closure of alveolar units in atelectrauma. Particularly important appears to be the fact that these processes may also cause biotrauma, i.e. the ventilator-induced hyperactivation of inflammatory responses in the lung. These side effects are reduced, but not eliminated with the currently recommended ventilation strategy with a tidal volume of 6 ml/kg idealized body weight. It is our hope that in the future optimization of ventilator settings will be facilated by bedside monitoring of novel indices of respiratory mechanics such as the stress index or the Slice technique, and by innovative real-time imaging technologies such as electrical impedance tomography.

Tidal Residual Eddies and their Effect on Water Exchange in Puget Sound

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Zhaoqing; Wang, Taiping

Tidal residual eddies are one of the important hydrodynamic features in tidally dominant estuaries and coastal bays, and they could have significant effects on water exchange in a tidal system. This paper presents a modeling study of tides and tidal residual eddies in Puget Sound, a tidally dominant fjord-like estuary in the Pacific Northwest coast, using a three-dimensional finite-volume coastal ocean model. Mechanisms of vorticity generation and asymmetric distribution patterns around an island/headland were analyzed using the dynamic vorticity transfer approach and numerical experiments. Model results of Puget Sound show that a number of large twin tidal residual eddies existmore » in the Admiralty Inlet because of the presence of major headlands in the inlet. Simulated residual vorticities near the major headlands indicate that the clockwise tidal residual eddy (negative vorticity) is generally stronger than the anticlockwise eddy (positive vorticity) because of the effect of Coriolis force. The effect of tidal residual eddies on water exchange in Puget Sound and its sub-basins were evaluated by simulations of dye transport. It was found that the strong transverse variability of residual currents in the Admiralty Inlet results in a dominant seaward transport along the eastern shore and a dominant landward transport along the western shore of the Inlet. A similar transport pattern in Hood Canal is caused by the presence of tidal residual eddies near the entrance of the canal. Model results show that tidal residual currents in Whidbey Basin are small in comparison to other sub-basins. A large clockwise residual circulation is formed around Vashon Island near entrance of South Sound, which can potentially constrain the water exchange between the Central Basin and South Sound.« less

Regional physiology of ARDS.

PubMed

Gattinoni, Luciano; Tonetti, Tommaso; Quintel, Michael

2017-12-28

The acute respiratory distress (ARDS) lung is usually characterized by a high degree of inhomogeneity. Indeed, the same lung may show a wide spectrum of aeration alterations, ranging from completely gasless regions, up to hyperinflated areas. This inhomogeneity is normally caused by the presence of lung edema and/or anatomical variations, and is deeply influenced by the gravitational forces.For any given airway pressure generated by the ventilator, the pressure acting directly on the lung (i.e., the transpulmonary pressure or lung stress) is determined by two main factors: 1) the ratio between lung elastance and the total elastance of the respiratory system (which has been shown to vary widely in ARDS patients, between 0.2 and 0.8); and 2) the lung size. In severe ARDS, the ventilatable parenchyma is strongly reduced in size ('baby lung'); its resting volume could be as low as 300 mL, and the total inspiratory capacity could be reached with a tidal volume of 750-900 mL, thus generating lethal stress and strain in the lung. Although this is possible in theory, it does not explain the occurrence of ventilator-induced lung injury (VILI) in lungs ventilated with much lower tidal volumes. In fact, the ARDS lung contains areas acting as local stress multipliers and they could multiply the stress by a factor ~ 2, meaning that in those regions the transpulmonary pressure could be double that present in other parts of the same lung. These 'stress raisers' widely correspond to the inhomogenous areas of the ARDS lung and can be present in up to 40% of the lung.Although most of the literature on VILI concentrates on the possible dangers of tidal volume, mechanical ventilation in fact delivers mechanical power (i.e., energy per unit of time) to the lung parenchyma, which reacts to it according to its anatomical structure and pathophysiological status. The determinants of mechanical power are not only the tidal volume, but also respiratory rate, inspiratory flow, and positive end-expiratory pressure (PEEP). In the end, decreasing mechanical power, increasing lung homogeneity, and avoiding reaching the anatomical limits of the 'baby lung' should be the goals for safe ventilation in ARDS.

Bibliography on Cold Regions Science and Technology. Volume 40, Part 1, 1986

DTIC Science & Technology

1986-12-01

witer migration in an unaaturated frozen soil, morin clay, waa determined in horizontally cloaed »oil columns under linear temperature gradients...Peninsula At both ice fronts there is signiPcant tidal height energy in the first seven tidal species, indicating strong non- linear interaction, not all...dry soil weight, and increases with the increase in the molality linearly because of the linear freezing point depression. The curves of the

Analysis of tidal currents in the North Sea from shipboard acoustic Doppler current profiler data

NASA Astrophysics Data System (ADS)

Vindenes, Håvard; Orvik, Kjell Arild; Søiland, Henrik; Wehde, Henning

2018-06-01

North Sea tidal currents are determined by applying harmonic analysis to ship-borne acoustic Doppler current profiler data recorded from 1999 to 2016, covering large areas of the northern North Sea. Direct current measurement data sets of this magnitude are rare in the otherwise well investigated North Sea, and thus it is a valuable asset in studying and expanding our understanding of its tidal currents and circulation in general. The harmonic analysis is applied to a least squares fit of the current observations at a set of knot points. Results from the harmonic analysis compare favorably to tidal parameters estimated from observations from moored instruments. The analysis shows that the tides are characterized by strong semi-diurnal component, with amplitudes of the principal Lunar constituent ranging from 1.6 cm/s in the Skagerrak to 67 cm/s in the Fair Isle Channel. Diurnal tides are found to be approximately one fifth the strength of the predominant semi-diurnal constituent. Output from a regional barotropic tide model compares well to tidal current determined from the harmonic analysis of the Acoustic Doppler Current Profiler data.

Ventilatory abnormalities in patients with cystic fibrosis undergoing the submaximal treadmill exercise test.

PubMed

Parazzi, Paloma Lopes Francisco; Marson, Fernando Augusto de Lima; Ribeiro, Maria Angela Gonçalves de Oliveira; de Almeida, Celize Cruz Bresciani; Martins, Luiz Cláudio; Paschoal, Ilma Aparecida; Toro, Adyleia Aparecida Dalbo Contrera; Schivinski, Camila Isabel Santos; Ribeiro, Jose Dirceu

2015-05-19

Exercise has been studied as a prognostic marker for patients with cystic fibrosis (CF), as well as a tool for improving their quality of life and analyzing lung disease. In this context, the aim of the present study was to evaluate and compare variables of lung functioning. Our data included: (i) volumetric capnography (VCAP) parameters: expiratory minute volume (VE), volume of exhaled carbon dioxide (VCO2), VE/VCO2, ratio of dead space to tidal volume (VD/VT), and end-tidal carbon dioxide (PetCO2); (ii) spirometry parameters: forced vital capacity (FVC), percent forced expiratory volume in the first second of the FVC (FEV1%), and FEV1/FVC%; and (iii) cardiorespiratory parameters: heart rate (HR), respiratory rate, oxygen saturation (SpO2), and Borg scale rating at rest and during exercise. The subjects comprised children, adolescents, and young adults aged 6-25 years with CF (CF group [CFG]) and without CF (control group [CG]). This was a clinical, prospective, controlled study involving 128 male and female patients (64 with CF) of a university hospital. All patients underwent treadmill exercise tests and provided informed consent after study approval by the institutional ethics committee. Linear regression, Kruskal-Wallis test, and Mann-Whitney test were performed to compare the CFG and CG. The α value was set at 0.05. Patients in the CFG showed significantly different VCAP values and spirometry variables throughout the exercise test. Before, during, and after exercise, several variables were different between the two groups; statistically significant differences were seen in the spirometry parameters, SpO2, HR, VCO2, VE/VCO2, PetCO2, and Borg scale rating. VCAP variables changed at each time point analyzed during the exercise test in both groups. VCAP can be used to analyze ventilatory parameters during exercise. All cardiorespiratory, spirometry, and VCAP variables differed between patients in the CFG and CG before, during, and after exercise.

Fast or Slow Rescue Ventilations: A Predictive Model of Gastric Inflation.

PubMed

Fitz-Clarke, John R

2018-05-01

Rescue ventilations are given during respiratory and cardiac arrest. Tidal volume must assure oxygen delivery; however, excessive pressure applied to an unprotected airway can cause gastric inflation, regurgitation, and pulmonary aspiration. The optimal technique provides mouth pressure and breath duration that minimize gastric inflation. It remains unclear if breath delivery should be fast or slow, and how inflation time affects the division of gas flow between the lungs and esophagus. A physiological model was used to predict and compare rates of gastric inflation and to determine ideal ventilation duration. Gas flow equations were based on standard pulmonary physiology. Gastric inflation was assumed to occur whenever mouth pressure exceeded lower esophageal sphincter pressure. Mouth pressure profiles that approximated mouth-to-mouth ventilation and bag-valve-mask ventilation were investigated. Target tidal volumes were set to 0.6 and 1.0 L. Compliance and airway resistance were varied. Rapid breaths shorter than 1 s required high mouth pressures, up to 25 cm H 2 O to achieve the target lung volume, which thus promotes gastric inflation. Slow breaths longer than 1 s permitted lower mouth pressures but increased time over which airway pressure exceeded lower esophageal sphincter pressure. The gastric volume increased with breath durations that exceeded 1 s for both mouth pressure profiles. Breath duration of ∼1.0 s caused the least gastric inflation in most scenarios. Very low esophageal sphincter pressure favored a shift toward 0.5 s. High resistance and low compliance each increased gastric inflation and altered ideal breath times. The model illustrated a general theory of optimal rescue ventilation. Breath duration with an unprotected airway should be 1 s to minimize gastric inflation. Short pressure-driven and long duration-driven gastric inflation regimens provide a unifying explanation for results in past studies. Copyright © 2018 by Daedalus Enterprises.

Mechanical Ventilation as a Therapeutic Tool to Reduce ARDS Incidence.

PubMed

Nieman, Gary F; Gatto, Louis A; Bates, Jason H T; Habashi, Nader M

2015-12-01

Trauma, hemorrhagic shock, or sepsis can incite systemic inflammatory response syndrome, which can result in early acute lung injury (EALI). As EALI advances, improperly set mechanical ventilation (MV) can amplify early injury into a secondary ventilator-induced lung injury that invariably develops into overt ARDS. Once established, ARDS is refractory to most therapeutic strategies, which have not been able to lower ARDS mortality below the current unacceptably high 40%. Low tidal volume ventilation is one of the few treatments shown to have a moderate positive impact on ARDS survival, presumably by reducing ventilator-induced lung injury. Thus, there is a compelling case to be made that the focus of ARDS management should switch from treatment once this syndrome has become established to the application of preventative measures while patients are still in the EALI stage. Indeed, studies have shown that ARDS incidence is markedly reduced when conventional MV is applied preemptively using a combination of low tidal volume and positive end-expiratory pressure in both patients in the ICU and in surgical patients at high risk for developing ARDS. Furthermore, there is evidence from animal models and high-risk trauma patients that superior prevention of ARDS can be achieved using preemptive airway pressure release ventilation with a very brief duration of pressure release. Preventing rather than treating ARDS may be the way forward in dealing with this recalcitrant condition and would represent a paradigm shift in the way that MV is currently practiced.

Calculating lunar retreat rates using tidal rhythmites

USGS Publications Warehouse

Kvale, E.P.; Johnson, H.W.; Sonett, C.P.; Archer, A.W.; Zawistoski, A.N.N.

1999-01-01

Tidal rhythmites are small-scale sedimenta??r}- structures that can preserve a hierarchy of astronomically induced tidal periods. They can also preserve a record of periodic nontidal sedimentation. If properly interpreted and understood, tidal rhjthmites can be an important component of paleoastronomy and can be used to extract information on ancient lunar orbital dynamics including changes in Earth-Moon distance through geologic time. Herein we present techniques that can be used to calculate ancient Earth-Moon distances. Each of these techniques, when used on a modern high-tide data set, results in calculated estimates of lunar orbital periods and an EarthMoon distance that fall well within 1 percent of the actual values. Comparisons to results from modern tidal data indicate that ancient tidal rhythmite data as short as 4 months can provide suitable estimates of lunar orbital periods if these tidal records are complete. An understanding of basic tidal theory allows for the evaluation of completeness of the ancient tidal record as derived from an analysis of tidal rhythmites. Utilizing the techniques presented herein, it appears from the rock record that lunar orbital retreat slowed sometime during the midPaleozoic. Copyright ??1999, SEPM (Society for Sedimentary Geology).

Sedimentation and response to sea-level rise of a restored marsh with reduced tidal exchange: Comparison with a natural tidal marsh

USGS Publications Warehouse

Vandenbruwaene, W.; Maris, T.; Cahoon, D.R.; Meire, P.; Temmerman, S.

2011-01-01

Along coasts and estuaries, formerly embanked land is increasingly restored into tidal marshes in order to re-establish valuable ecosystem services, such as buffering against flooding. Along the Scheldt estuary (Belgium), tidal marshes are restored on embanked land by allowing a controlled reduced tide (CRT) into a constructed basin, through a culvert in the embankment. In this way tidal water levels are significantly lowered (ca. 3 m) so that a CRT marsh can develop on formerly embanked land with a ca. 3 m lower elevation than the natural tidal marshes. In this study we compared the long-term change in elevation (ΔE) within a CRT marsh and adjacent natural tidal marsh. Over a period of 4 years, the observed spatio-temporal variations in ΔE rate were related to variations in inundation depth, and this relationship was not significantly different for the CRT marsh and natural tidal marsh. A model was developed to simulate the ΔE over the next century. (1) Under a scenario without mean high water level (MHWL) rise in the estuary, the model shows that the marsh elevation-ΔE feedback that is typical for a natural tidal marsh (i.e. rising marsh elevation results in decreasing inundation depth and therefore a decreasing increase in elevation) is absent in the basin of the CRT marsh. This is because tidal exchange of water volumes between the estuary and CRT marsh are independent from the CRT marsh elevation but dependent on the culvert dimensions. Thus the volume of water entering the CRT remains constant regardless of the marsh elevation. Consequently the CRT MHWL follows the increase in CRT surface elevation, resulting after 75 years in a 2–2.5 times larger elevation gain in the CRT marsh, and a faster reduction of spatial elevation differences. (2) Under a scenario of constant MHWL rise (historical rate of 1.5 cm a-1), the equilibrium elevation (relative to MHWL) is 0.13 m lower in the CRT marsh and is reached almost 2 times faster. (3) Under a scenario of accelerated MHWL rise (acceleration of 0.02 cm a-1), the CRT marsh is much less able to keep up with the MHWL rise; after 75 years the CRT elevation is already 0.21 m lower than for the natural marsh. In conclusion, this study demonstrates that although short-term (4 years) ΔE rates are similar in a restored CRT marsh and natural tidal marsh, these ecosystems may evolve differently in response to sea-level rise in the longer term (10–100 years).

Patterns and drivers of daily bed-level dynamics on two tidal flats with contrasting wave exposure.

PubMed

Hu, Zhan; Yao, Peng; van der Wal, Daphne; Bouma, Tjeerd J

2017-08-02

Short-term bed-level dynamics has been identified as one of the main factors affecting biota establishment or retreat on tidal flats. However, due to a lack of proper instruments and intensive labour involved, the pattern and drivers of daily bed-level dynamics are largely unexplored in a spatiotemporal context. In this study, 12 newly-developed automatic bed-level sensors were deployed for nearly 15 months on two tidal flats with contrasting wave exposure, proving an unique dataset of daily bed-level changes and hydrodynamic forcing. By analysing the data, we show that (1) a general steepening trend exists on both tidal flats, even with contrasting wave exposure and different bed sediment grain size; (2) daily morphodynamics level increases towards the sea; (3) tidal forcing sets the general morphological evolution pattern at both sites; (4) wave forcing induces short-term bed-level fluctuations at the wave-exposed site, but similar effect is not seen at the sheltered site with smaller waves; (5) storms provoke aggravated erosion, but the impact is conditioned by tidal levels. This study provides insights in the pattern and drivers of daily intertidal bed-level dynamics, thereby setting a template for future high-resolution field monitoring programmes and inviting in-depth morphodynamic modelling for improved understanding and predictive capability.

Pressure-limited sustained inflation vs. gradual tidal inflations for resuscitation in preterm lambs.

PubMed

Tingay, David G; Polglase, Graeme R; Bhatia, Risha; Berry, Clare A; Kopotic, Robert J; Kopotic, Clinton P; Song, Yong; Szyld, Edgardo; Jobe, Alan H; Pillow, J Jane

2015-04-01

Support of the mechanically complex preterm lung needs to facilitate aeration while avoiding ventilation heterogeneities: whether to achieve this gradually or quickly remains unclear. We compared the effect of gradual vs. constant tidal inflations and a pressure-limited sustained inflation (SI) at birth on gas exchange, lung mechanics, gravity-dependent lung volume distribution, and lung injury in 131-day gestation preterm lambs. Lambs were resuscitated with either 1) a 20-s, 40-cmH2O pressure-limited SI (PressSI), 2) a gradual increase in tidal volume (Vt) over 5-min from 3 ml/kg to 7 ml/kg (IncrVt), or 3) 7 ml/kg Vt from birth. All lambs were subsequently ventilated for 15 min with 7 ml/kg Vt with the same end-expiratory pressure. Lung mechanics, gas exchange and spatial distribution of end-expiratory volume (EEV), and tidal ventilation (electrical impedance tomography) were recorded regularly. At 15 min, early mRNA tissue markers of lung injury were assessed. The IncrVt group resulted in greater tissue hysteresivity at 5 min (P = 0.017; two-way ANOVA), higher alveolar-arterial oxygen difference from 10 min (P < 0.01), and least uniform gravity-dependent distribution of EEV. There were no other differences in lung mechanics between groups, and the PressSI and 7 ml/kg Vt groups behaved similarly throughout. EEV was more uniformly distributed, but Vt least so, in the PressSI group. There were no differences in mRNA markers of lung injury. A gradual increase in Vt from birth resulted in less recruitment of the gravity-dependent lung with worse oxygenation. There was no benefit of a SI at birth over mechanical ventilation with 7 ml/kg Vt. Copyright © 2015 the American Physiological Society.

Evaluation of the effects of dorsal versus lateral recumbency on the cardiopulmonary system during anesthesia with isoflurane in red-tailed hawks (Buteo jamaicensis).

PubMed

Hawkins, Michelle G; Malka, Shachar; Pascoe, Peter J; Solano, Adrian M; Kass, Philip H; Ohmura, Hajime; Jones, James H

2013-01-01

To evaluate the effects of dorsal versus lateral recumbency on the cardiopulmonary system during isoflurane anesthesia in red-tailed hawks (Buteo jamaicensis). 6 adult 1.1- to 1.6-kg red-tailed hawks. A randomized, crossover study was used to evaluate changes in respiratory rate, tidal volume, minute ventilation, heart rate, mean arterial and indirect blood pressures, and end-tidal Pco(2) measured every 5 minutes plus Paco(2) and Pao(2) and arterial pH measured every 15 minutes throughout a 75-minute study period. Respiratory rate was higher, tidal volume lower, and minute ventilation not different in lateral versus dorsal recumbency. Position did not affect heart rate, mean arterial blood pressure, or indirect blood pressure, although heart rate decreased during the anesthetic period. Birds hypoventilated in both positions and Paco(2) differed with time and position × time interaction. The Petco(2) position × time interaction was significant and Petco(2) was a mean of 7 Torr higher than Paco(2). The Paco(2) in dorsal recumbency was a mean of 32 Torr higher than in lateral recumbency. Birds in both positions developed respiratory acidosis. Differences in tidal volume with similar minute ventilation suggested red-tailed hawks in dorsal recumbency might have lower dead space ventilation. Despite similar minute ventilation in both positions, birds in dorsal recumbency hypoventilated more yet maintained higher Pao(2), suggesting parabronchial ventilatory or pulmonary blood flow distribution changes with position. The results refute the hypothesis that dorsal recumbency compromises ventilation and O(2) transport more than lateral recumbency in red-tailed hawks.

Prevalence of tidal expiratory flow limitation in preschool children with and without respiratory symptoms: application of the negative expiratory pressure (NEP) method.

PubMed

JIRICKOVA, A; SULC, J; POHUNEK, P; KITTNAR, O; DOHNALOVA, A; KOFRANEK, J

2009-01-01

Negative expiratory pressure (NEP) applied at the mouth during tidal expiration provides a non-invasive method for detecting expiratory flow limitation. Forty-two children were studied, i.e. 25 children with different respiratory symptoms (R) and 17 without any respiratory symptoms (NR). Children were examined without any sedation. A preset NEP of -5 cm H(2)O was applied; its duration did not exceed duration of tidal expiration. A significance of FL was judged by determining of a flow-limited range (in % of tidal volume). FL was found in 48 % children of R group. No patient of the NR group elicited FL (P<0.001 R vs. NR). The frequency of upper airway collapses was higher in R group (12 children) than in NR group (5 children). In conclusion, a high frequency of tidal FL in the R group was found, while it was not present in NR group. A relatively high frequency of expiratory upper airway collapses was found in both groups, but it did not differ significantly. NEP method represents a reasonable approach for tidal flow limitation testing in non-sedated preschool children.

Impact of intertidal area characteristics on estuarine tidal hydrodynamics: A modelling study for the Scheldt Estuary

NASA Astrophysics Data System (ADS)

Stark, J.; Smolders, S.; Meire, P.; Temmerman, S.

2017-11-01

Marsh restoration projects are nowadays being implemented as ecosystem-based strategies to reduce flood risks and to restore intertidal habitat along estuaries. Changes in estuarine tidal hydrodynamics are expected along with such intertidal area changes. A validated hydrodynamic model of the Scheldt Estuary is used to gain fundamental insights in the role of intertidal area characteristics on tidal hydrodynamics and tidal asymmetry in particular through several geomorphological scenarios in which intertidal area elevation and location along the estuary is varied. Model results indicate that the location of intertidal areas and their storage volume relative to the local tidal prism determine the intensity and reach along the estuary over which tidal hydrodynamics are affected. Our model results also suggest that intertidal storage areas that are located within the main estuarine channel system, and hence are part of the flow-carrying part of the estuary, may affect tidal hydrodynamics differently than intertidal areas that are side-basins of the main estuarine channel, and hence only contribute little to the flow-carrying cross-section of the estuary. If tidal flats contribute to the channel cross-section and exert frictional effects on the tidal propagation, the elevation of intertidal flats influences the magnitude and direction of tidal asymmetry along estuarine channels. Ebb-dominance is most strongly enhanced if tidal flats are around mean sea level or slightly above. Conversely, flood-dominance is enhanced if the tidal flats are situated low in the tidal frame. For intertidal storage areas at specific locations besides the main channel, flood-dominance in the estuary channel peaks in the vicinity of those areas and generally reduces upstream and downstream compared to a reference scenario. Finally, the model results indicate an along-estuary varying impact on the tidal prism as a result of adding intertidal storage at a specific location. In addition to known effects of tidal prism decrease upstream and tidal prism increase downstream of additional storage areas, our model results indicate a reduction in tidal prism far downstream of intertidal storage areas as a result of a decreasing tidal range. This study may assist estuarine managers in assessing the impact of marsh restoration and managed shoreline realignment projects, as well as with the morphological management of estuaries through dredging and disposal of sediment on intertidal areas.

[Anesthesia for thoracoscopic laser ablation of bullae in a patient with severe bullous emphysema].

PubMed

Saito, Y; Hayashida, M; Arita, H; Hanaoka, K

1995-05-01

A 46-year-old male underwent laser-ablation of emphysematous bullae of the right lung via thoracoscope. For almost a year he had been bedridden because of severe dyspnea on exertion, in spite of medication and oxygen therapy. He also complained of orthopnea at rest and had suffered from body weight loss of 10 kg during the preceding year. Radiologic examination revealed emphysemotous lung with bilateral giant bullae. In spirogram, forced vital capacity in 1 second was markedly low (0.45 l, corresponding to 19% in %FVC1.0), vital capacity moderately depressed (2.41 l, 64%) and residual volume markedly elevated (5.85 l, 387%). Anesthesia was induced and maintained using the combination of thoracic-epidural anesthesia and intravenous anesthesia (midazolam and fentanyl). One lung ventilation (OLV) was used to facilitate thoracoscopic procedure. Mechanical ventilation was conducted at first with an anesthesia ventilator. As the duration of OLV was prolonged, however, the peak airway pressure increased, the tidal volume decreased and the value of percutaneous arterial hemoglobin saturation (SpO2) declined. In order to keep adequate oxygenation, brief periods of two lung ventilation (TLV) became necessary, in addition to the application of continuous positive airway pressure to the non-dependent lung. When ventilation was changed from volume-cycled ventilation to pressure-cycled and from using an anesthesia ventilator to a critical care type ventilator (Servo 900C), sufficient tidal volume was achieved with lower peak airway pressure, producing reasonable Spo2 value with much less frequent TLV. At the end of the surgery bronchopleural fistulae still persisted, with resultant air leak of about 50% of inspired tidal volume.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of tidal action on pollination and reproductive allocation in an estuarine emergent wetland plant-Sagittaria graminea (Alismataceae).

PubMed

Zhang, Yanwen; Zhang, Lihui; Zhao, Xingnan; Huang, Shengjun; Zhao, Jimin

2013-01-01

In estuarine wetlands, the daily periodic tidal activity has a profound effect on plant growth and reproduction. We studied the effects of tidal action on pollination and reproductive allocation of Sagittaria graminea. Results showed that the species had very different reproductive allocation in tidal and non-tidal habitats. In the tidal area, seed production was only 9.7% of that in non-tidal habitat, however, plants produced more male flowers and nearly twice the corms compared to those in non-tidal habitat. An experiment showed that the time available for effective pollination determined the pollination rate and pollen deposition in the tidal area. A control experiment suggested that low pollen deposition from low visitation frequency is not the main cause of very low seed sets or seed production in this plant in tidal habitat. The negative effects of tides (water) on pollen germination may surpass the influence of low pollen deposition from low visitation frequency. The length of time from pollen deposition to flower being submerged by water affected pollen germination rate on stigmas; more than three hours is necessary to allow pollen germination and complete fertilization to eliminate the risk of pollen grains being washed away by tidal water.

Effects of Tidal Action on Pollination and Reproductive Allocation in an Estuarine Emergent Wetland Plant–Sagittaria graminea (Alismataceae)

PubMed Central

Zhang, Yanwen; Zhang, Lihui; Zhao, Xingnan; Huang, Shengjun; Zhao, Jimin

2013-01-01

In estuarine wetlands, the daily periodic tidal activity has a profound effect on plant growth and reproduction. We studied the effects of tidal action on pollination and reproductive allocation of Sagittaria graminea. Results showed that the species had very different reproductive allocation in tidal and non-tidal habitats. In the tidal area, seed production was only 9.7% of that in non-tidal habitat, however, plants produced more male flowers and nearly twice the corms compared to those in non-tidal habitat. An experiment showed that the time available for effective pollination determined the pollination rate and pollen deposition in the tidal area. A control experiment suggested that low pollen deposition from low visitation frequency is not the main cause of very low seed sets or seed production in this plant in tidal habitat. The negative effects of tides (water) on pollen germination may surpass the influence of low pollen deposition from low visitation frequency. The length of time from pollen deposition to flower being submerged by water affected pollen germination rate on stigmas; more than three hours is necessary to allow pollen germination and complete fertilization to eliminate the risk of pollen grains being washed away by tidal water. PMID:24244393

Respiratory effort correction strategies to improve the reproducibility of lung expansion measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Du, Kaifang; Reinhardt, Joseph M.; Christensen, Gary E.

2013-12-15

Purpose: Four-dimensional computed tomography (4DCT) can be used to make measurements of pulmonary function longitudinally. The sensitivity of such measurements to identify change depends on measurement uncertainty. Previously, intrasubject reproducibility of Jacobian-based measures of lung tissue expansion was studied in two repeat prior-RT 4DCT human acquisitions. Difference in respiratory effort such as breathing amplitude and frequency may affect longitudinal function assessment. In this study, the authors present normalization schemes that correct ventilation images for variations in respiratory effort and assess the reproducibility improvement after effort correction.Methods: Repeat 4DCT image data acquired within a short time interval from 24 patients priormore » to radiation therapy (RT) were used for this analysis. Using a tissue volume preserving deformable image registration algorithm, Jacobian ventilation maps in two scanning sessions were computed and compared on the same coordinate for reproducibility analysis. In addition to computing the ventilation maps from end expiration to end inspiration, the authors investigated the effort normalization strategies using other intermediated inspiration phases upon the principles of equivalent tidal volume (ETV) and equivalent lung volume (ELV). Scatter plots and mean square error of the repeat ventilation maps and the Jacobian ratio map were generated for four conditions: no effort correction, global normalization, ETV, and ELV. In addition, gamma pass rate was calculated from a modified gamma index evaluation between two ventilation maps, using acceptance criterions of 2 mm distance-to-agreement and 5% ventilation difference.Results: The pattern of regional pulmonary ventilation changes as lung volume changes. All effort correction strategies improved reproducibility when changes in respiratory effort were greater than 150 cc (p < 0.005 with regard to the gamma pass rate). Improvement of reproducibility was correlated with respiratory effort difference (R = 0.744 for ELV in the cohort with tidal volume difference greater than 100 cc). In general for all subjects, global normalization, ETV and ELV significantly improved reproducibility compared to no effort correction (p = 0.009, 0.002, 0.005 respectively). When tidal volume difference was small (less than 100 cc), none of the three effort correction strategies improved reproducibility significantly (p = 0.52, 0.46, 0.46 respectively). For the cohort (N = 13) with tidal volume difference greater than 100 cc, the average gamma pass rate improves from 57.3% before correction to 66.3% after global normalization, and 76.3% after ELV. ELV was found to be significantly better than global normalization (p = 0.04 for all subjects, and p = 0.003 for the cohort with tidal volume difference greater than 100 cc).Conclusions: All effort correction strategies improve the reproducibility of the authors' pulmonary ventilation measures, and the improvement of reproducibility is highly correlated with the changes in respiratory effort. ELV gives better results as effort difference increase, followed by ETV, then global. However, based on the spatial and temporal heterogeneity in the lung expansion rate, a single scaling factor (e.g., global normalization) appears to be less accurate to correct the ventilation map when changes in respiratory effort are large.« less

Galactic Tidal Shocks Effects in Globular Clusters

NASA Astrophysics Data System (ADS)

Cruz, F.; Aguilar, L.

2001-07-01

We present results of a set of N--Body simulations of 105--particle King models in the presence of a realistic Galactic tidal field. Tidal effects over a cluster are dominated by two processes, differentiated by the way they produc e mass loss in the system. The first one is the Roche lobe overflow, which depend s directly on the ratio of cluster to the Roche lobe size. The second process is tidal heating, produced by the time varying part of the Galactic tide, which injects energy directly on the orbits of the stars inside the cluster.

Performance of portable ventilators at altitude

DTIC Science & Technology

2015-04-20

currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT DATE (DD-MM-YYYY) 20 Apr 2015 2. REPORT TYPE Journal...consistent tidal volume (VT) delivery at various altitudes is imperative for lung protection when transporting wounded war fighters to each echelon...of care. Three ventilators (Impact 731, Hamilton T1, and CareFusion Revel) were tested at pediatric (50 and 100 mL) and adult (250Y750 mL) tidal VTs

Predicting tidal marsh survival or submergence to sea-level rise using Holocene data

NASA Astrophysics Data System (ADS)

Horton, B.; Shennan, I.; Bradley, S.; Cahill, N.; Kirwan, M. L.; Kopp, R. E.; Shaw, T.

2017-12-01

Rising sea level threatens to permanently submerge tidal marsh environments if they cannot accrete faster than the rate of relative sea-level rise (RSLR). But regional and global model simulations of the future ability of marshes to maintain their elevation with respect to the tidal frame are uncertain. The compilation of empirical data for tidal marsh vulnerability is, therefore, essential to address disparities across these simulations. A hitherto unexplored source of empirical data are Holocene records of tidal marsh evolution. In particular, the marshes of Great Britain have survived and submerged while RSLR varied between -7.7 and 15.2 mm/yr, primarily because of the interplay between global ice-volume changes and regional isostatic processes. Here, we reveal the limits to marsh vulnerability are revealed through the analysis of over 400 reconstructions of tidal marsh submergence and conversion to tidal mud flat or open water from 54 regions in Great Britain during the Holocene. Holocene records indicate a 90% probability of tidal marsh submergence at sites with RSLR exceeding 7.3 mm/yr (95% CI: 6.6-8.6 mm/yr). Although most modern tidal marshes in Great Britain have not yet reached these sea-level rise limits, our empirical data suggest widespread concern over their ability to survive rates of sea-level rise in the 21st century under high emission scenarios. Integrating over the uncertainties in both sea-level rise predictions and the response of tidal marshes to sea-level rise, all of Great Britain has a >80% probability of marsh submergence under RCP 8.5 by 2100, with areas of south and eastern England, where the rate of RSLR is increased by glacio-isostatic subsidence, achieving this probability by 2040.

[Dynamic changes of lung function in infant of different gestational ages].

PubMed

Qi, Li-feng; Yu, Jia-lin; Liu, Xiao-hong; Wei, Min-chao

2013-06-25

To explore the dynamic changes of lung function in infants born at different gestational ages without respiratory complications. A total of 110 cases of hospitalized neonatal patients were retrospectively recruited and analyzed at Shenzhen Children's Hospital from July 2010 to August 2012. By gestational age they were divided into 3 groups of full term (37-40 weeks, n = 55, 29 males and 26 females) with an average birth weight (3.1 ± 0.3) kg, late preterm group (34- < 37 weeks, n = 30, 18 males and 12 females) with an average birth weight (2.1 ± 0.3) kg and early preterm (<34 weeks, n = 25, 16 males and 9 females )with an average birth weight (1.4 ± 0.3) kg. At Days 1, 14 and 28, lung function parameters of functional residual capacity (FRC) and lung clear index (LCI) were measured by multiple breath washouts with an ultrasonic flow meter and tidal breathing. One-way ANOVA was used for each index. Tidal expiratory flow 75% remaining tidal volume (TEF75), tidal expiratory flow 50% remaining tidal volume (TEF50) and tidal expiratory flow 25% remaining tidal volume (TEF25) gradually increased at Days 1, 14 and 28 in 3 groups. However respiratory rate (RR) gradually decreased. Compared with full term and late preterm, the early preterm infants had lower TEF75, TEF50 and TEF25, lower the ratios of time to peak expiratory flow and expiratory time (TPTEF/TE), lower ratios of volume to peak expiratory flow and expiratory volume (VPEF/VE) ((71 ± 21) and (66 ± 16) vs (55 ± 19)ml/s, (70 ± 20) and (62 ± 17) vs (51 ± 16)ml/s, (54 ± 17) and (51 ± 13) vs (38 ± 10)ml/s, 37% ± 8% and 34% ± 9% vs 29% ± 6%, 38% ± 6% and 33% ± 8% vs 28% ± 7%, F = 5.82, 8.74, 11.30, 7.72, 16.40, all P < 0.01), higher RR and LCI at Day 28((49 ± 6) and (51 ± 8) vs (56 ± 7)/min, 8.6 ± 2.7 and 8.9 ± 2.2 vs 10.8 ± 2.0,F = 10.09, 7.15, both P < 0.05). At a matched post-menstrual age of 40 weeks, compared with full term and late preterm, the early preterm group had lower TEF50, TEF25, TPTEF/TE, VPEF/VE ((65 ± 21) and (62 ± 12) vs (50 ± 17)ml/s,(51 ± 13) and (47 ± 10) vs (39 ± 10)ml/s, 36% ± 8% and 31% ± 7% vs 30% ± 6%, 37% ± 10% and 32% ± 8% vs 29% ± 6%,F = 4.41, 8.23, 9.08, 7.35, all P < 0.05). Lung function improves with the elongation of days. The parameters of lung function in early infants are worse than those in full and late-preterm counterparts. At a corrected gestational age of 40 weeks, early preterm infants fail to achieve catch-up growth in lung function. Dynamic monitoring of lung function in preterm infants of different gestational ages is of vital importance for gauging respiratory maturity and assessing lung development especially for preterm infants.

Changing tidal hydrodynamics during different stages of eco-geomorphological development of a tidal marsh: A numerical modeling study

NASA Astrophysics Data System (ADS)

Stark, J.; Meire, P.; Temmerman, S.

2017-03-01

The eco-geomorphological development of tidal marshes, from initially low-elevated bare tidal flats up to a high-elevated marsh and its typical network of channels and creeks, induces long-term changes in tidal hydrodynamics in a marsh, which will have feedback effects on the marsh development. We use a two-dimensional hydrodynamic model of the Saeftinghe marsh (Netherlands) to study tidal hydrodynamics, and tidal asymmetry in particular, for model scenarios with different input bathymetries and vegetation coverages that represent different stages of eco-geomorphological marsh development, from a low elevation stage with low vegetation coverage to a high and fully vegetated marsh platform. Tidal asymmetry is quantified along a 4 km marsh channel by (1) the difference in peak flood and peak ebb velocities, (2) the ratio between duration of the rising tide and the falling tide and (3) the time-integrated dimensionless bed shear stress during flood and ebb. Although spatial variations in tidal asymmetry are large and the different indicators for tidal asymmetry do not always respond similarly to eco-geomorphological changes, some general trends can be obtained. Flood-dominance prevails during the initial bare stage of a low-lying tidal flat. Vegetation establishment and platform expansion lead to marsh-scale flow concentration to the bare channels, causing an increase in tidal prism in the channels along with a less flood-dominant asymmetry of the horizontal tide. The decrease in flood-dominance continues as the platform grows vertically and the sediment-demand of the platform decreases. However, when the platform elevation gets sufficiently high in the tidal frame and part of the spring-neap cycle is confined to the channels, the discharge in the channels decreases and tidal asymmetry becomes more flood-dominant again, indicating an infilling of the marsh channels. Furthermore, model results suggest that hydro-morphodynamic feedbacks based on tidal prism to channel cross-sectional area relationships keep the marsh channels from filling in completely by enhancing ebb-dominance as long as the tidal volume and flow velocities remain sufficiently high. Overall, this study increases insight into the hydro-morphodynamic interactions between tidal flow and marsh geomorphology during various stages of eco-geomorphological development of marshes and marsh channels in particular.

Are we fully utilizing the functionalities of modern operating room ventilators?

PubMed

Liu, Shujie; Kacmarek, Robert M; Oto, Jun

2017-12-01

The modern operating room ventilators have become very sophisticated and many of their features are comparable with those of an ICU ventilator. To fully utilize the functionality of modern operating room ventilators, it is important for clinicians to understand in depth the working principle of these ventilators and their functionalities. Piston ventilators have the advantages of delivering accurate tidal volume and certain flow compensation functions. Turbine ventilators have great ability of flow compensation. Ventilation modes are mainly volume-based or pressure-based. Pressure-based ventilation modes provide better leak compensation than volume-based. The integration of advanced flow generation systems and ventilation modes of the modern operating room ventilators enables clinicians to provide both invasive and noninvasive ventilation in perioperative settings. Ventilator waveforms can be used for intraoperative neuromonitoring during cervical spine surgery. The increase in number of new features of modern operating room ventilators clearly creates the opportunity for clinicians to optimize ventilatory care. However, improving the quality of ventilator care relies on a complete understanding and correct use of these new features. VIDEO ABSTRACT: http://links.lww.com/COAN/A47.

A prototype of volume-controlled tidal liquid ventilator using independent piston pumps.

PubMed

Robert, Raymond; Micheau, Philippe; Cyr, Stéphane; Lesur, Olivier; Praud, Jean-Paul; Walti, Hervé

2006-01-01

Liquid ventilation using perfluorochemicals (PFC) offers clear theoretical advantages over gas ventilation, such as decreased lung damage, recruitment of collapsed lung regions, and lavage of inflammatory debris. We present a total liquid ventilator designed to ventilate patients with completely filled lungs with a tidal volume of PFC liquid. The two independent piston pumps are volume controlled and pressure limited. Measurable pumping errors are corrected by a programmed supervisor module, which modifies the inserted or withdrawn volume. Pump independence also allows easy functional residual capacity modifications during ventilation. The bubble gas exchanger is divided into two sections such that the PFC exiting the lungs is not in contact with the PFC entering the lungs. The heating system is incorporated into the metallic base of the gas exchanger, and a heat-sink-type condenser is placed on top of the exchanger to retrieve PFC vapors. The prototype was tested on 5 healthy term newborn lambs (<5 days old). The results demonstrate the efficiency and safety of the prototype in maintaining adequate gas exchange, normal acido-basis equilibrium, and cardiovascular stability during a short, 2-hour total liquid ventilator. Airway pressure, lung volume, and ventilation scheme were maintained in the targeted range.

[Study of setting of ventilator volume tidal and airway pressure alarm threshold with continuous extra-sternum heart compression in cardiopulmonary resuscitation].

PubMed

Luo, Jian-yu; Wang, Xiao-yuan; Cai, Tian-bin; Jiang, Wen-fang

2013-02-01

To investigate the setting of ventilator volume tidal (VT) and airway pressure alarm threshold during cardiopulmonary resuscitation (CPR) by continuous extra-sternum heart compression. Forty cases with respiration and cardiac arrest in the department of critical care medicine were randomly divided into low VT ventilation group and conventional VT group. Both groups were given the volume control mode. In the low VT ventilation group, VT was set on 6 - 7 ml/kg, and high pressure alarm threshold was adjusted to 60 cm H2O by the conventional 40 cm H2O during CPR. In the conventional VT group, VT and high pressure alarm threshold were set at 8 - 12 ml/kg and 40 cm H2O, respectively. Real-time actual VT, peak inspiratory pressure (PIP), and arterial blood gas test, blood lactic acid at 10 minutes and 30 minutes after CPR were observed. At 10 minutes after CPR, in the low VT ventilation group, arterial blood pH, arterial partial pressure of oxygen (PaO2), arterial partial pressure of carbon dioxide (PaCO2), HCO3(-), arterial oxygen saturation (SaO2) and blood lactic acid were better as compared with those in the conventional VT ventilation group (pH: 7.21±0.09 vs. 7.13±0.07, PaO2: 45.35±5.92 mm Hg vs. 40.70±4.70 mm Hg, PaCO2: 57.10±7.59 mm Hg vs. 61.60±5.47 mm Hg, HCO3(-): 18.50±3.50 mmol/L vs. 14.75±2.65 mmol/L, SaO2: 0.796±0.069 vs. 0.699±0.066, blood lactic acid: 7.07±1.60 mmol/L vs. 8.13±1.56 mmol/L, all P<0.05). The success rate of resuscitation in the low VT ventilation group was higher than that of the conventional VT ventilation group (45% vs. 15%, P<0.05), and PIP (cm H2O) of low VT ventilation group was lower than that of the conventional VT group (37.25±7.99 cm H2O vs. 42.70±7.40 cm H2O, P<0.05). In all the patients in both groups barotrauma did not occur. The strategy of low ventilator VT (6 - 7 ml/kg) with appropriate elevation of airway pressure alarm threshold was better than that of conventional ventilation setting, with no increase in incidence of barotraumas during CPR.

Neonatal hygroscopic condenser humidifier.

PubMed

Gedeon, A; Mebius, C; Palmer, K

1987-01-01

A hygroscopic condenser humidifier was developed for neonates on mechanical ventilation and was evaluated by laboratory tests and clinically. Humidification provided by the unit was measured in the 10- to 50-ml tidal-volume range at ambient temperatures of 24 degrees C and 38 degrees C. The effect of a leaking patient connection on device performance was investigated. Leakage rates were measured routinely in a neonatal ICU and surgery to determine the clinical significance. In the entire tidal volume and temperature range, the unit provided an inspiratory water content in excess of 30 g/m3 when the leak fraction (volume leaked/volume delivered at Y-piece) was less than 15%. This was found in three out of four cases. In about one out of ten cases, the leak exceeded 30%, which invariably led to corrective action, such as repositioning or changing the endotracheal tube. However, even at a 30% leak, a water content of about 26 g/m3 was still available for humidifying the inspired gas, which corresponds to normal physiologic conditions found in the trachea for nasal breathing of room air.

Tides and tidal stress: Applications to Europa

NASA Astrophysics Data System (ADS)

Hurford, Terry Anthony, Jr.

A review of analytical techniques and documentation of previously inaccessible mathematical formulations is applied to study of Jupiter's satellite Europa. Compared with numerical codes that are commonly used to model global tidal effects, analytical models of tidal deformation give deeper insight into the mechanics of tides, and can better reveal the nature of the dependence of observable effects on key parameters. I develop analytical models for tidal deformation of multi-layered bodies. Previous studies of Europa, based on numerical computation, only to show isolated examples from parameter space. My results show a systematic dependence of tidal response on the thicknesses and material parameters of Europa's core, rocky mantle, liquid water ocean, and outer layer of ice. As in the earlier work, I restrict these studies to incompressible materials. Any set of Love numbers h 2 and k 2 which describe a planet's tidal deformation, could be fit by a range of ice thickness values, by adjusting other parameters such as mantle rigidity or core size, an important result for mission planning. Inclusion of compression into multilayer models has been addressed analytically, uncovering several issues that are not explicit in the literature. Full evaluation with compression is here restricted to a uniform sphere. A set of singularities in the classical solution, which correspond to instabilities due to self-gravity has been identified and mapped in parameter space. The analytical models of tidal response yield the stresses anywhere within the body, including on its surface. Crack patterns (such as cycloids) on Europa are probably controlled by these stresses. However, in contrast to previous studies which used a thin shell approximation of the tidal stress, I consider how other tidal models compare with the observed tectonic features. In this way the relationship between Europa's surface tectonics and the global tidal distortion can be constrained. While large-scale tidal deformations probe internal structure deep within a body, small-scale deformations can probe internal structure at shallower depths. I have used photoclinometry to obtain topographic profiles across terrain adjacent to Europan ridges to detect the effects of loading on the lithosphere. Lithospheric thicknesses have been determined and correlated with types and ages of terrain.

The Development of a Finite Volume Method for Modeling Sound in Coastal Ocean Environment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Long, Wen; Yang, Zhaoqing; Copping, Andrea E.

: As the rapid growth of marine renewable energy and off-shore wind energy, there have been concerns that the noises generated from construction and operation of the devices may interfere marine animals’ communication. In this research, a underwater sound model is developed to simulate sound prorogation generated by marine-hydrokinetic energy (MHK) devices or offshore wind (OSW) energy platforms. Finite volume and finite difference methods are developed to solve the 3D Helmholtz equation of sound propagation in the coastal environment. For finite volume method, the grid system consists of triangular grids in horizontal plane and sigma-layers in vertical dimension. A 3Dmore » sparse matrix solver with complex coefficients is formed for solving the resulting acoustic pressure field. The Complex Shifted Laplacian Preconditioner (CSLP) method is applied to efficiently solve the matrix system iteratively with MPI parallelization using a high performance cluster. The sound model is then coupled with the Finite Volume Community Ocean Model (FVCOM) for simulating sound propagation generated by human activities in a range-dependent setting, such as offshore wind energy platform constructions and tidal stream turbines. As a proof of concept, initial validation of the finite difference solver is presented for two coastal wedge problems. Validation of finite volume method will be reported separately.« less

Tidal Triggering of Microearthquakes Over an Eruption Cycle at 9°50'N East Pacific Rise

NASA Astrophysics Data System (ADS)

Tan, Yen Joe; Tolstoy, Maya; Waldhauser, Felix; Bohnenstiehl, DelWayne R.

2018-02-01

Studies have found that earthquake timing often correlates with tides at mid-ocean ridges and some terrestrial settings. Studies have also suggested that tidal triggering may preferentially happen when a region is critically stressed, making it a potential tool to forecast earthquakes and volcanic eruptions. We examine tidal triggering of ˜100,000 microearthquakes near 9°50'N East Pacific Rise recorded between October 2003 and January 2007, which encompasses an eruption in January 2006. This allows us to look at how tidal triggering signal varies over an eruption cycle to examine its utility as a forecasting tool. We find that tidal triggering signal is strong but does not vary systematically in the 2+ years leading up to the eruption. However, tidal triggering signal disappears immediately posteruption. Our findings suggest that tidal triggering variation may not be useful for forecasting mid-ocean ridge eruptions over a 2+ year timescale but might be useful over a longer timescale.

Acupressure Improves the Weaning Indices of Tidal Volumes and Rapid Shallow Breathing Index in Stable Coma Patients Receiving Mechanical Ventilation: Randomized Controlled Trial

PubMed Central

Maa, Suh-Hwa; Wang, Chiu-Hua; Hsu, Kuang-Hung; Lin, Horng-Chyuan; Yee, Brian; MacDonald, Karen

2013-01-01

Background. Acupressure has been shown to improve respiratory parameters. We investigated the effects of acupressure on weaning indices in stable coma patients receiving mechanical ventilation. Methods. Patients were randomly allocated to one of three treatments: standard care with adjunctive acupressure on one (n = 32) or two days (n = 31) and standard care (n = 31). Acupressure in the form of 10 minutes of bilateral stimulation at five acupoints was administered per treatment session. Weaning indices were collected on two days before, right after, and at 0.5 hrs, 1 hr, 1.5 hrs, 2 hrs, 2.5 hrs, 3 hrs, 3.5 hrs, and 4 hrs after the start of treatment. Results. There were statistically significant improvements in tidal volumes and index of rapid shallow breathing in the one-day and two-day adjunctive acupressure study arms compared to the standard care arm immediately after acupressure and persisting until 0.5, 1 hr, and 2 hrs after adjustment for covariates. Conclusions. In the stable ventilated coma patient, adjunctive acupressure contributes to improvements in tidal volumes and the index of rapid shallow breathing, the two indices most critical for weaning patients from mechanical ventilation. These effects tend to be immediate and likely to be sustained for 1 to 2 hours. PMID:23710234

A randomised crossover comparison of mouth-to-face-shield ventilation and mouth-to-pocket-mask ventilation by surf lifeguards in a manikin.

PubMed

Adelborg, K; Bjørnshave, K; Mortensen, M B; Espeseth, E; Wolff, A; Løfgren, B

2014-07-01

Thirty surf lifeguards (mean (SD) age: 25.1 (4.8) years; 21 male, 9 female) were randomly assigned to perform 2 × 3 min of cardiopulmonary resuscitation on a manikin using mouth-to-face-shield ventilation (AMBU LifeKey) and mouth-to-pocket-mask ventilation (Laerdal Pocket Mask). Interruptions in chest compressions, effective ventilation (visible chest rise) ratio, tidal volume and inspiratory time were recorded. Interruptions in chest compressions per cycle were increased with mouth-to-face-shield ventilation (mean (SD) 8.6 (1.7) s) compared with mouth-to-pocket-mask ventilation (6.9 (1.2) s, p < 0.0001). The proportion of effective ventilations was less using mouth-to-face-shield ventilation (199/242 (82%)) compared with mouth-to-pocket-mask ventilation (239/240 (100%), p = 0.0002). Tidal volume was lower using mouth-to-face-shield ventilation (mean (SD) 0.36 (0.20) l) compared with mouth-to-pocket-mask ventilation (0.45 (0.20) l, p = 0.006). No differences in inspiratory times were observed between mouth-to-face-shield ventilation and mouth-to-pocket-mask ventilation. In conclusion, mouth-to-face-shield ventilation increases interruptions in chest compressions, reduces the proportion of effective ventilations and decreases delivered tidal volumes compared with mouth-to-pocket-mask ventilation. © 2014 The Association of Anaesthetists of Great Britain and Ireland.

Adjusting tidal volume to stress index in an open lung condition optimizes ventilation and prevents overdistension in an experimental model of lung injury and reduced chest wall compliance.

PubMed

Ferrando, Carlos; Suárez-Sipmann, Fernando; Gutierrez, Andrea; Tusman, Gerardo; Carbonell, Jose; García, Marisa; Piqueras, Laura; Compañ, Desamparados; Flores, Susanie; Soro, Marina; Llombart, Alicia; Belda, Francisco Javier

2015-01-13

The stress index (SI), a parameter derived from the shape of the pressure-time curve, can identify injurious mechanical ventilation. We tested the hypothesis that adjusting tidal volume (VT) to a non-injurious SI in an open lung condition avoids hypoventilation while preventing overdistension in an experimental model of combined lung injury and low chest-wall compliance (Ccw). Lung injury was induced by repeated lung lavages using warm saline solution, and Ccw was reduced by controlled intra-abdominal air-insufflation in 22 anesthetized, paralyzed and mechanically ventilated pigs. After injury animals were recruited and submitted to a positive end-expiratory pressure (PEEP) titration trial to find the PEEP level resulting in maximum compliance. During a subsequent four hours of mechanical ventilation, VT was adjusted to keep a plateau pressure (Pplat) of 30 cmH2O (Pplat-group, n = 11) or to a SI between 0.95 and 1.05 (SI-group, n = 11). Respiratory rate was adjusted to maintain a 'normal' PaCO2 (35 to 65 mmHg). SI, lung mechanics, arterial-blood gases haemodynamics pro-inflammatory cytokines and histopathology were analyzed. In addition Computed Tomography (CT) data were acquired at end expiration and end inspiration in six animals. PaCO2 was significantly higher in the Pplat-group (82 versus 53 mmHg, P = 0.01), with a resulting lower pH (7.19 versus 7.34, P = 0.01). We observed significant differences in VT (7.3 versus 5.4 mlKg(-1), P = 0.002) and Pplat values (30 versus 35 cmH2O, P = 0.001) between the Pplat-group and SI-group respectively. SI (1.03 versus 0.99, P = 0.42) and end-inspiratory transpulmonary pressure (PTP) (17 versus 18 cmH2O, P = 0.42) were similar in the Pplat- and SI-groups respectively, without differences in overinflated lung areas at end- inspiration in both groups. Cytokines and histopathology showed no differences. Setting tidal volume to a non-injurious stress index in an open lung condition improves alveolar ventilation and prevents overdistension without increasing lung injury. This is in comparison with limited Pplat protective ventilation in a model of lung injury with low chest-wall compliance.

A perfluorochemical loss/restoration (L/R) system for tidal liquid ventilation.

PubMed

Libros, R; Philips, C M; Wolfson, M R; Shaffer, T H

2000-01-01

Tidal liquid ventilation is the transport of dissolved respiratory gases via volume exchange of perfluorochemical (PFC) liquid to and from the PFC-filled lung. All gas-liquid surface tension is eliminated, increasing compliance and providing lung protection due to lower inflation pressures. Tidal liquid ventilation is achieved by cycling fluid from a reservoir to and from the lung by a ventilator. Current approaches are microprocessor-based with feedback control. During inspiration, warmed oxygenated PFC liquid is pumped from a fluid reservoir/gas exchanger into the lung. PFC fluid is conserved by condensing (60-80% efficiency) vapor in the expired gas. A feedback-control system was developed to automatically replace PFC lost due to condenser inefficiency. This loss/restoration (L/R) system consists of a PFC-vapor thermal detector (+/- 2.5%), pneumatics, amplifiers, a gas flow detector (+/- 1%), a PFC pump (+/- 5%), and a controller. Gravimetric studies of perflubron loss from a flask due to evaporation were compared with experimental L/R results and found to be within +/- 1.4%. In addition, when L/R studies were conducted with a previously reported liquid ventilation system over a four-hour period, the L/R system maintained system perflubron volume to within +/- 1% of prime volume and 11.5% of replacement volume, and the difference between experimental PFC loss and that of the L/R system was 1.8 mL/hr. These studies suggest that the PFC L/R system may have significant economic (appropriate dosing for PFC loss) as well as physiologic (maintenance of PFC inventory in the lungs and liquid ventilator) impact on liquid ventilation procedures.

Tidal and tidally averaged circulation characteristics of Suisun Bay, California

USGS Publications Warehouse

Smith, Lawrence H.; Cheng, Ralph T.

1987-01-01

Availability of extensive field data permitted realistic calibration and validation of a hydrodynamic model of tidal circulation and salt transport for Suisun Bay, California. Suisun Bay is a partially mixed embayment of northern San Francisco Bay located just seaward of the Sacramento-San Joaquin Delta. The model employs a variant of an alternating direction implicit finite-difference method to solve the hydrodynamic equations and an Eulerian-Lagrangian method to solve the salt transport equation. An upwind formulation of the advective acceleration terms of the momentum equations was employed to avoid oscillations in the tidally averaged velocity field produced by central spatial differencing of these terms. Simulation results of tidal circulation and salt transport demonstrate that tides and the complex bathymetry determine the patterns of tidal velocities and that net changes in the salinity distribution over a few tidal cycles are small despite large changes during each tidal cycle. Computations of tidally averaged circulation suggest that baroclinic and wind effects are important influences on tidally averaged circulation during low freshwater-inflow conditions. Exclusion of baroclinic effects would lead to overestimation of freshwater inflow by several hundred m3/s for a fixed set of model boundary conditions. Likewise, exclusion of wind would cause an underestimation of flux rates between shoals and channels by 70–100%.

Determinants of early-life lung function in African infants

PubMed Central

Willemse, Lauren; Visagie, Ane; Czövek, Dorottya; Nduru, Polite; Vanker, Aneesa; Stein, Dan J; Koen, Nastassja; Sly, Peter D; Hantos, Zoltán; Hall, Graham L; Zar, Heather J

2017-01-01

Background Low lung function in early life is associated with later respiratory illness. There is limited data on lung function in African infants despite a high prevalence of respiratory disease. Aim To assess the determinants of early lung function in African infants. Method Infants enrolled in a South African birth cohort, the Drakenstein child health study, had lung function measured at 6–10 weeks of age. Measurements, made with the infant breathing via a facemask during natural sleep, included tidal breathing, sulfur hexafluoride multiple breath washout and the forced oscillation technique. Information on antenatal and early postnatal exposures was collected using questionnaires and urine cotinine. Household benzene exposure was measured antenatally. Results Successful tests were obtained in 645/675 (95%) infants, median (IQR) age of 51 (46–58) days. Infant size, age and male gender were associated with larger tidal volume. Infants whose mothers smoked had lower tidal volumes (−1.6 mL (95% CI −3.0 to −0.1), p=0.04) and higher lung clearance index (0.1 turnovers (95% CI 0.01 to 0.3), p=0.03) compared with infants unexposed to tobacco smoke. Infants exposed to alcohol in utero or household benzene had lower time to peak tidal expiratory flow over total expiratory time ratios, 10% (95% CI −15.4% to −3.7%), p=0.002) and 3.0% (95% CI −5.2% to −0.7%, p=0.01) lower respectively compared with unexposed infants. HIV-exposed infants had higher tidal volumes (1.7 mL (95% CI 0.06 to 3.3) p=0.04) compared with infants whose mothers were HIV negative. Conclusion We identified several factors including infant size, sex, maternal smoking, maternal alcohol, maternal HIV and household benzene associated with altered early lung function, many of which are factors amenable to public health interventions. Long-term study of lung function and respiratory disease in these children is a priority to develop strategies to strengthen child health. PMID:27856821

Influence of tidal fluctuations in the water table and methods applied in the calculation of hydrogeological parameters. The case of Motril-Salobreña coastal aquifer

NASA Astrophysics Data System (ADS)

Sánchez Úbeda, Juan Pedro; Calvache Quesada, María Luisa; Duque Calvache, Carlos; López Chicano, Manuel; Martín Rosales, Wenceslao

2013-04-01

The hydraulic properties of coastal aquifer are essential for any estimation of groundwater flow with simple calculations or modelling techniques. Usually the application of slug test or tracers test are the techniques selected for solving the uncertainties. Other methods are based on the information associated to the changes induced by tidal fluctuation in coastal zones. The Tidal Response Method is a simple technique based in two different factors, tidal efficiency factor and time lag of the tidal oscillation regarding to hydraulic head oscillation caused into the aquifer. This method was described for a homogeneous and isotropic confined aquifer; however, it's applicable to unconfined aquifers when the ratio of maximum water table fluctuation and the saturated aquifer thickness is less than 0.02. Moreover, the tidal equations assume that the tidal signal follows a sinusoidal wave, but actually, the tidal wave is a set of simple harmonic components. Due to this, another methods based in the Fourier series have been applied in earlier studies trying to describe the tidal wave. Nevertheless, the Tidal Response Method represents an acceptable and useful technique in the Motril-Salobreña coastal aquifer. From recently hydraulic head data sets at discharge zone of the Motril-Salobreña aquifer have been calculated transmissivity values using different methods based in the tidal fluctuations and its effects on the hydraulic head. The effects of the tidal oscillation are detected in two boreholes of 132 m and 38 m depth located 300 m to the coastline. The main difficulties for the application of the method were the consideration of a confined aquifer and the variation of the effect at different depths (that is not included into the tidal equations), but these troubles were solved. In one hand, the assumption that the storage coefficient (S) in this unconfined aquifer is close to confined aquifers values due to the hydrogeological conditions at high depth and without saturation changes. In the other hand, we have monitored hydraulic head fluctuations due to tidal oscillations in different shallow boreholes close to the shoreline, and comparing with the deep ones. The calculated values with the tidal efficiency factor in the deep boreholes are about one less order of magnitude regarding to the obtained results with time lag method. Nevertheless, the application of these calculation methods based on tidal response in unconfined aquifers provides knowledge about the characteristics of the discharge zone and groundwater flow patterns, and it may be an easy and profitable alternative to traditional pumping tests.

Arterial-to-end-tidal carbon dioxide tension difference in children with congenital heart disease.

PubMed

Choudhury, Minati; Kiran, Usha; Choudhary, Shiv Kumar; Airan, Balram

2006-04-01

This study estimated the arterial-to-end-tidal carbon dioxide tension difference (deltaPaCO2-PE'CO2) in children with congenital heart disease; evaluated whether hyperventilation can reduce this difference; and analyzed the relationship between the difference and the oxygen saturation (SaO2) and hemoglobin level. Prospective clinical study. Tertiary health care center. One hundred patients scheduled for correction of their underlying cardiac defect with either right-to-left or left-to-right intracardiac shunts were divided into 4 groups (n = 25 each): (1) N1, cyanotic with severe pulmonary artery hypertension; (2) N2, cyanotic with normal or decreased pulmonary artery pressure (PAP); (3) N3, acyanotic with normal or mild increases in PAP and severe increases in pulmonary blood flow (PBF); and (4) N4, acyanotic with normal PAP and normal or mild increase in PBF. All the patients received the same anesthetic regimen. The initial settings for tidal volume, respiratory rate, and inspiratory-to-expiratory (I:E) ratio were 10 mL/kg, 15 to 30 breath/min, and inspired time 40% of the total respiratory period with a 10% end-inspiratory pause. After the measurement of oxygen saturation, PO2, Hb, and deltaPaCO2-PE'CO2, all the children were hyperventilated (tidal volume: 14-15 mL/kg, respiratory rate: 5-6 breaths/min more than the initial rate, I:E ratio: same) to observe its effects on the deltaPaCO2-PE'CO2. The deltaPaCO2-PE'CO2, when predicted from the oxygen saturation, hemoglobin concentration, and PaO2, was found to be greater than the observed value in the first 3 groups (p < 0.001); whereas in group N4 these 2 values were comparable. It was also found that the gradient was higher when there was a decrease in SaO2 and an increase in the hemoglobin level. After hyperventilation, in groups N1 and N3, deltaPaCO2-PE'CO2 was decreased when compared with their baseline values; this reduction was not as much as predicted (p = 0.363 and 0.236, respectively). However, in groups N2 and N4 posthyperventilation, the deltaPaCO2-PE'27 CO2 was decreased significantly below their baseline measurements. These decreases were as much predicted. The deltaPaCO2-end-tidal carbon dioxide (PE'CO2) can be increased both in cyanotic and acyanotic children. Increased PAP is as important as increased PBF or right-to-left shunting in producing disorders in carbon dioxide homeostasis. Hyperventilation is of little use in reducing deltaPaCO2-PE'CO2 in children with high PAPs and pulmonary hyperperfusion.

Extension of Oxygen Tolerance in Man. Predictive Studies 6.

DTIC Science & Technology

1991-12-31

maintained on Ziegler rat and mouse diet were used in these -12- i exposures. Average weights of the different exposure groups ranged from about 300...end of oxygen exposure were associated with reciprocal changes in end-tidal PCO 2 . Average PCO 2 (N=7) decreased significantly from 40.8 mm Hg during... PCO 2 (N=6) increased from 30.8 to 36.2 mm Hg. An increased frequency of breathing with a related reduction in tidal volume was found near the end of

Effects of Breathing Resistance on Resting Ventilatory Sensitivity to CO2

DTIC Science & Technology

2014-08-12

be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE...elements were designed to generate work of breathing per tidal volume of 1 kPa when minute ventilation was 100 L/min. Resistance caused no systematic...the laboratory is considerably lower and that end- tidal PCO2 is higher with resistance in the breathing circuit than without it.2, 3 Work has

Respiratory mechanics to understand ARDS and guide mechanical ventilation.

PubMed

Mauri, Tommaso; Lazzeri, Marta; Bellani, Giacomo; Zanella, Alberto; Grasselli, Giacomo

2017-11-30

As precision medicine is becoming a standard of care in selecting tailored rather than average treatments, physiological measurements might represent the first step in applying personalized therapy in the intensive care unit (ICU). A systematic assessment of respiratory mechanics in patients with the acute respiratory distress syndrome (ARDS) could represent a step in this direction, for two main reasons. Approach and Main results: On the one hand, respiratory mechanics are a powerful physiological method to understand the severity of this syndrome in each single patient. Decreased respiratory system compliance, for example, is associated with low end expiratory lung volume and more severe lung injury. On the other hand, respiratory mechanics might guide protective mechanical ventilation settings. Improved gravitationally dependent regional lung compliance could support the selection of positive end-expiratory pressure and maximize alveolar recruitment. Moreover, the association between driving airway pressure and mortality in ARDS patients potentially underlines the importance of sizing tidal volume on respiratory system compliance rather than on predicted body weight. The present review article aims to describe the main alterations of respiratory mechanics in ARDS as a potent bedside tool to understand severity and guide mechanical ventilation settings, thus representing a readily available clinical resource for ICU physicians.

Analytical Model of Inlet Growth and Equilibrium Cross-Sectional Area

DTIC Science & Technology

2016-04-01

performance in a real-world setting. BACKGROUND: Long-term inlet stability in bar-built systems is determined by the tidal and wave forces that...across the node was limited due to convergence of the two incoming tidal waves . As such, the equivalent bay area was calculated using the midpoint as a...sediment transport is driven by tides and does not incorporate other forcing and associated sediment pathways. The ratio of wave to tidal energy is an

[Successful airway management using i-gel in 7 patients undergoing awake craniotomy].

PubMed

Matsunami, Katsuaki; Sanuki, Michiyoshi; Yasuuji, Masakazu; Nakanuno, Ryuichi; Kato, Takahiro; Kawamoto, Masashi

2014-07-01

In order to secure airway during awake craniotomy, we used i-gel to perform positive-pressure ventilation in 7 patients for their anesthetic management. During removal of a tumor around the motor speech center, anesthetic management including asleep-awake-asleep technique was applied for speech testing. The technique, insertion and re-insertion of i-gel, was needed and it was easy in all the patients. During positive-pressure ventilation, peak pressure, tidal volume both for inspiration and expiration, and endtidal-CO2 were not markedly altered. Leakage around i-gel, and its differences between inspiration and expiration were negligible, while the tidal volume was adequate. We conclude that i-gel is useful for anesthetic management for awake craniotomy procedure for both securing airway and ventilation.

Thermal Pollution Mathematical Model. Volume 6; Verification of Three-Dimensional Free-Surface Model at Anclote Anchorage; [environment impact of thermal discharges from power plants

NASA Technical Reports Server (NTRS)

Lee, S. S.; Sengupta, S.; Tuann, S. Y.; Lee, C. R.

1980-01-01

The free-surface model presented is for tidal estuaries and coastal regions where ambient tidal forces play an important role in the dispersal of heated water. The model is time dependent, three dimensional, and can handle irregular bottom topography. The vertical stretching coordinate is adopted for better treatment of kinematic condition at the water surface. The results include surface elevation, velocity, and temperature. The model was verified at the Anclote Anchorage site of Florida Power Company. Two data bases at four tidal stages for winter and summer conditions were used to verify the model. Differences between measured and predicted temperatures are on an average of less than 1 C.

Flows of X-ray gas reveal the disruption of a star by a massive black hole.

PubMed

Miller, Jon M; Kaastra, Jelle S; Miller, M Coleman; Reynolds, Mark T; Brown, Gregory; Cenko, S Bradley; Drake, Jeremy J; Gezari, Suvi; Guillochon, James; Gultekin, Kayhan; Irwin, Jimmy; Levan, Andrew; Maitra, Dipankar; Maksym, W Peter; Mushotzky, Richard; O'Brien, Paul; Paerels, Frits; de Plaa, Jelle; Ramirez-Ruiz, Enrico; Strohmayer, Tod; Tanvir, Nial

2015-10-22

Tidal forces close to massive black holes can violently disrupt stars that make a close approach. These extreme events are discovered via bright X-ray and optical/ultraviolet flares in galactic centres. Prior studies based on modelling decaying flux trends have been able to estimate broad properties, such as the mass accretion rate. Here we report the detection of flows of hot, ionized gas in high-resolution X-ray spectra of a nearby tidal disruption event, ASASSN-14li in the galaxy PGC 043234. Variability within the absorption-dominated spectra indicates that the gas is relatively close to the black hole. Narrow linewidths indicate that the gas does not stretch over a large range of radii, giving a low volume filling factor. Modest outflow speeds of a few hundred kilometres per second are observed; these are below the escape speed from the radius set by variability. The gas flow is consistent with a rotating wind from the inner, super-Eddington region of a nascent accretion disk, or with a filament of disrupted stellar gas near to the apocentre of an elliptical orbit. Flows of this sort are predicted by fundamental analytical theory and more recent numerical simulations.

Highly dynamically evolved intermediate-age open clusters

NASA Astrophysics Data System (ADS)

Piatti, Andrés E.; Dias, Wilton S.; Sampedro, Laura M.

2017-04-01

We present a comprehensive UBVRI and Washington CT1T2 photometric analysis of seven catalogued open clusters, namely: Ruprecht 3, 9, 37, 74, 150, ESO 324-15 and 436-2. The multiband photometric data sets in combination with 2MASS photometry and Gaia astrometry for the brighter stars were used to estimate their structural parameters and fundamental astrophysical properties. We found that Ruprecht 3 and ESO 436-2 do not show self-consistent evidence of being physical systems. The remained studied objects are open clusters of intermediate age (9.0 ≤ log(t yr-1) ≤ 9.6), of relatively small size (rcls ˜ 0.4-1.3 pc) and placed between 0.6 and 2.9 kpc from the Sun. We analysed the relationships between core, half-mass, tidal and Jacoby radii as well as half-mass relaxation times to conclude that the studied clusters are in an evolved dynamical stage. The total cluster masses obtained by summing those of the observed cluster stars resulted to be ˜10-15 per cent of the masses of open clusters of similar age located closer than 2 kpc from the Sun. We found that cluster stars occupy volumes as large as those for tidally filled clusters.

Effect of metronome rates on the quality of bag-mask ventilation during metronome-guided 30:2 cardiopulmonary resuscitation: A randomized simulation study.

PubMed

Na, Ji Ung; Han, Sang Kuk; Choi, Pil Cho; Shin, Dong Hyuk

2017-01-01

Metronome guidance is a feasible and effective feedback technique to improve the quality of cardiopulmonary resuscitation (CPR). The rate of the metronome should be set between 100 to 120 ticks/minute and the speed of ventilation may have crucial effect on the quality of ventilation. We compared three different metronome rates (100, 110, 120 ticks/minute) to investigate its effect on the quality of ventilation during metronome-guided 30:2 CPR. This is a prospective, randomized, crossover observational study using a RespiTrainer○ r . To simulate 30 chest compressions, one investigator counted from 1 to 30 in cadence with the metronome rate (1 count for every 1 tick), and the participant performed 2 consecutive ventilations immediately following the counting of 30. Thirty physicians performed 5 sets of 2 consecutive (total 10) bag-mask ventilations for each metronome rate. Participants were instructed to squeeze the bag over 2 ticks (1.0 to 1.2 seconds depending on the rate of metronome) and deflate the bag over 2 ticks. The sequence of three different metronome rates was randomized. Mean tidal volume significantly decreased as the metronome rate was increased from 110 ticks/minute to 120 ticks/minute (343±84 mL vs. 294±90 mL, P =0.004). Peak airway pressure significantly increased as metronome rate increased from 100 ticks/minute to 110 ticks/minute (18.7 vs. 21.6 mmHg, P =0.006). In metronome-guided 30:2 CPR, a higher metronome rate may adversely affect the quality of bag-mask ventilations. In cases of cardiac arrest where adequate ventilation support is necessary, 100 ticks/minute may be better than 110 or 120 ticks/minute to deliver adequate tidal volume during audio tone guided 30:2 CPR.

Effect of metronome rates on the quality of bag-mask ventilation during metronome-guided 30:2 cardiopulmonary resuscitation: A randomized simulation study

PubMed Central

Na, Ji Ung; Han, Sang Kuk; Choi, Pil Cho; Shin, Dong Hyuk

2017-01-01

BACKGROUND: Metronome guidance is a feasible and effective feedback technique to improve the quality of cardiopulmonary resuscitation (CPR). The rate of the metronome should be set between 100 to 120 ticks/minute and the speed of ventilation may have crucial effect on the quality of ventilation. We compared three different metronome rates (100, 110, 120 ticks/minute) to investigate its effect on the quality of ventilation during metronome-guided 30:2 CPR. METHODS: This is a prospective, randomized, crossover observational study using a RespiTrainer○r. To simulate 30 chest compressions, one investigator counted from 1 to 30 in cadence with the metronome rate (1 count for every 1 tick), and the participant performed 2 consecutive ventilations immediately following the counting of 30. Thirty physicians performed 5 sets of 2 consecutive (total 10) bag-mask ventilations for each metronome rate. Participants were instructed to squeeze the bag over 2 ticks (1.0 to 1.2 seconds depending on the rate of metronome) and deflate the bag over 2 ticks. The sequence of three different metronome rates was randomized. RESULTS: Mean tidal volume significantly decreased as the metronome rate was increased from 110 ticks/minute to 120 ticks/minute (343±84 mL vs. 294±90 mL, P=0.004). Peak airway pressure significantly increased as metronome rate increased from 100 ticks/minute to 110 ticks/minute (18.7 vs. 21.6 mmHg, P=0.006). CONCLUSION: In metronome-guided 30:2 CPR, a higher metronome rate may adversely affect the quality of bag-mask ventilations. In cases of cardiac arrest where adequate ventilation support is necessary, 100 ticks/minute may be better than 110 or 120 ticks/minute to deliver adequate tidal volume during audio tone guided 30:2 CPR. PMID:28458759

Variable effectiveness of stepwise implementation of nudge-type interventions to improve provider compliance with intraoperative low tidal volume ventilation.

PubMed

O'Reilly-Shah, Vikas N; Easton, George S; Jabaley, Craig S; Lynde, Grant C

2018-05-18

Identifying mechanisms to improve provider compliance with quality metrics is a common goal across medical disciplines. Nudge interventions are minimally invasive strategies that can influence behavioural changes and are increasingly used within healthcare settings. We hypothesised that nudge interventions may improve provider compliance with lung-protective ventilation (LPV) strategies during general anaesthesia. We developed an audit and feedback dashboard that included information on both provider-level and department-level compliance with LPV strategies in two academic hospitals, two non-academic hospitals and two academic surgery centres affiliated with a single healthcare system. Dashboards were emailed to providers four times over the course of the 9-month study. Additionally, the default setting on anaesthesia machines for tidal volume was decreased from 700 mL to 400 mL. Data on surgical cases performed between 1 September 2016 and 31 May 2017 were examined for compliance with LPV. The impact of the interventions was assessed via pairwise logistic regression analysis corrected for multiple comparisons. A total of 14 793 anaesthesia records were analysed. Absolute compliance rates increased from 59.3% to 87.8%preintervention to postintervention. Introduction of attending physician dashboards resulted in a 41% increase in the odds of compliance (OR 1.41, 95% CI 1.17 to 1.69, p=0.002). Subsequently, the addition of advanced practice provider and resident dashboards lead to an additional 93% increase in the odds of compliance (OR 1.93, 95% CI 1.52 to 2.46, p<0.001). Lastly, modifying ventilator defaults led to a 376% increase in the odds of compliance (OR 3.76, 95% CI 3.1 to 4.57, p<0.001). Audit and feedback tools in conjunction with default changes improve provider compliance. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Mechanical ventilatory constraints during incremental cycle exercise in human pregnancy: implications for respiratory sensation

PubMed Central

Jensen, Dennis; Webb, Katherine A; Davies, Gregory A L; O'Donnell, Denis E

2008-01-01

The aim of this study was to identify the physiological mechanisms of exertional respiratory discomfort (breathlessness) in pregnancy by comparing ventilatory (breathing pattern, airway function, operating lung volumes, oesophageal pressure (Poes)-derived indices of respiratory mechanics) and perceptual (breathlessness intensity) responses to incremental cycle exercise in 15 young, healthy women in the third trimester (TM3; between 34 and 38 weeks gestation) and again 4–5 months postpartum (PP). During pregnancy, resting inspiratory capacity (IC) increased (P < 0.01) and end-expiratory lung volume decreased (P < 0.001), with no associated change in total lung capacity (TLC) or static respiratory muscle strength. This permitted greater tidal volume (VT) expansion throughout exercise in TM3, while preserving the relationship between contractile respiratory muscle effort (tidal Poes swing expressed as a percentage of maximum inspiratory pressure (PImax)) and thoracic volume displacement (VT expressed as a percentage of vital capacity) and between breathlessness and ventilation (V̇E). At the highest equivalent work rate (HEWR = 128 ± 5 W) in TM3 compared with PP: V̇E, tidal Poes/PImax and breathlessness intensity ratings increased by 10.2 l min−1 (P < 0.001), 8.8%PImax (P < 0.05) and 0.9 Borg units (P < 0.05), respectively. Pulmonary resistance was not increased at rest or during exercise at the HEWR in TM3, despite marked increases in mean tidal inspiratory and expiratory flow rates, suggesting increased bronchodilatation. Dynamic mechanical constraints on VT expansion (P < 0.05) with associated increased breathlessness intensity ratings (P < 0.05) were observed near peak exercise in TM3 compared with PP. In conclusion: (1) pregnancy-induced increases in exertional breathlessness reflected the normal awareness of increased V̇E and contractile respiratory muscle effort; (2) mechanical adaptations of the respiratory system, including recruitment of resting IC and increased bronchodilatation, accommodated the increased VT while preserving effort–displacement and breathlessness–V̇E relationships; and (3) dynamic mechanical ventilatory constraints contributed to respiratory discomfort near the limits of tolerance in late gestation. PMID:18687714

Association between driving pressure and development of postoperative pulmonary complications in patients undergoing mechanical ventilation for general anaesthesia: a meta-analysis of individual patient data.

PubMed

Neto, Ary Serpa; Hemmes, Sabrine N T; Barbas, Carmen S V; Beiderlinden, Martin; Fernandez-Bustamante, Ana; Futier, Emmanuel; Gajic, Ognjen; El-Tahan, Mohamed R; Ghamdi, Abdulmohsin A Al; Günay, Ersin; Jaber, Samir; Kokulu, Serdar; Kozian, Alf; Licker, Marc; Lin, Wen-Qian; Maslow, Andrew D; Memtsoudis, Stavros G; Reis Miranda, Dinis; Moine, Pierre; Ng, Thomas; Paparella, Domenico; Ranieri, V Marco; Scavonetto, Federica; Schilling, Thomas; Selmo, Gabriele; Severgnini, Paolo; Sprung, Juraj; Sundar, Sugantha; Talmor, Daniel; Treschan, Tanja; Unzueta, Carmen; Weingarten, Toby N; Wolthuis, Esther K; Wrigge, Hermann; Amato, Marcelo B P; Costa, Eduardo L V; de Abreu, Marcelo Gama; Pelosi, Paolo; Schultz, Marcus J

2016-04-01

Protective mechanical ventilation strategies using low tidal volume or high levels of positive end-expiratory pressure (PEEP) improve outcomes for patients who have had surgery. The role of the driving pressure, which is the difference between the plateau pressure and the level of positive end-expiratory pressure is not known. We investigated the association of tidal volume, the level of PEEP, and driving pressure during intraoperative ventilation with the development of postoperative pulmonary complications. We did a meta-analysis of individual patient data from randomised controlled trials of protective ventilation during general anesthaesia for surgery published up to July 30, 2015. The main outcome was development of postoperative pulmonary complications (postoperative lung injury, pulmonary infection, or barotrauma). We included data from 17 randomised controlled trials, including 2250 patients. Multivariate analysis suggested that driving pressure was associated with the development of postoperative pulmonary complications (odds ratio [OR] for one unit increase of driving pressure 1·16, 95% CI 1·13-1·19; p<0·0001), whereas we detected no association for tidal volume (1·05, 0·98-1·13; p=0·179). PEEP did not have a large enough effect in univariate analysis to warrant inclusion in the multivariate analysis. In a mediator analysis, driving pressure was the only significant mediator of the effects of protective ventilation on development of pulmonary complications (p=0·027). In two studies that compared low with high PEEP during low tidal volume ventilation, an increase in the level of PEEP that resulted in an increase in driving pressure was associated with more postoperative pulmonary complications (OR 3·11, 95% CI 1·39-6·96; p=0·006). In patients having surgery, intraoperative high driving pressure and changes in the level of PEEP that result in an increase of driving pressure are associated with more postoperative pulmonary complications. However, a randomised controlled trial comparing ventilation based on driving pressure with usual care is needed to confirm these findings. None. Copyright © 2016 Elsevier Ltd. All rights reserved.

Recovery from welding-fume-exposure-induced lung fibrosis and pulmonary function changes in sprague dawley rats.

PubMed

Sung, Jae Hyuck; Choi, Byung-Gil; Maeng, Seung-Hee; Kim, Soo-Jin; Chung, Yong Hyun; Han, Jeong Hee; Song, Kyung Seuk; Lee, Yong Hwan; Cho, Yong Bong; Cho, Myung-Haing; Kim, Kwang Jong; Hyun, Jin Suk; Yu, Il Je

2004-12-01

Welder's pneumoconiosis has generally been determined as benign based on the absence of pulmonary function abnormalities in welders with marked radiographic abnormalities. Yet, there have also been several reports on welders with respiratory symptoms, indicating lung function impairment, X-ray abnormalities, and extensive fibrosis. Accordingly, this study attempted to investigate the inflammatory responses and pulmonary function changes in rats during a 60-day welding-fume-inhalation exposure period to elucidate the process of fibrosis. The rats were exposed to manual metal-arc stainless-steel welding fumes (MMA-SS) with total suspended particulate concentrations of 64.8 +/- 0.9 (low dose) and 107.8 +/- 2.6 mg/m3 (high dose) for 2 h per day in an inhalation chamber for 60 days. Animals were sacrificed after the initial 2-h exposure and after 15, 30, and 60 days, and the pulmonary function was also measured every week after the daily exposure. Elevated cellular differential counts were also measured in the acellular bronchoalveolar lavage fluid of the rats exposed to the MMA-SS fumes for 60 days. Among the pulmonary function test parameters, only the tidal volume showed a statistically significant and dose-dependent decrease after 35 to 60 days of MMA-SS welding-fume exposure. When the rats exposed to the welding fumes were left for 60 days to recover their lung function and cellular differentiation, recovery was observed in both the high and low-dose rats exposed up to 30 days, resulting in the disappearance of inflammatory cells and restoration of the tidal volume. The rats exposed for 60 days at the low dose also recovered from the inflammation and tidal volume loss, yet the rats exposed for 60 days at the high dose did not fully recover even after a 60-day recovery period. Therefore, when taken together, the results of the current study suggest that a decrease in the tidal volume could be used as an early indicator of pulmonary fibrosis induced by welding-fume exposure in Sprague Dawley rats, and fibrosis would seem to be preventable if the exposure is short-term and moderate.

The Tulip GT® airway versus the facemask and Guedel airway: a randomised, controlled, cross-over study by Basic Life Support-trained airway providers in anaesthetised patients.

PubMed

Shaikh, A; Robinson, P N; Hasan, M

2016-03-01

We performed a randomised, controlled, cross-over study of lung ventilation by Basic Life Support-trained providers using either the Tulip GT® airway or a facemask with a Guedel airway in 60 anaesthetised patients. Successful ventilation was achieved if the provider produced an end-tidal CO2 > 3.5 kPa and a tidal volume > 250 ml in two of the first three breaths, within 60 sec and within two attempts. Fifty-seven (95%) providers achieved successful ventilation using the Tulip GT compared with 35 (58%) using the facemask (p < 0.0001). Comparing the Tulip GT and facemask, the mean (SD) end-tidal CO2 was 5.0 (0.7) kPa vs 2.5 (1.5) kPa, tidal volume was 494 (175) ml vs 286 (186) ml and peak inspiratory pressure was 18.3 (3.4) cmH2 O vs 13.6 (7) cmH2 O respectively (all p < 0.0001). Forty-seven (78%) users favoured the Tulip GT airway. These results are similar to a previous manikin study using the same protocol, suggesting a close correlation between human and manikin studies for this airway device. We conclude that the Tulip GT should be considered as an adjunct to airway management both within and outside hospitals when ventilation is being undertaken by Basic Life Support-trained airway providers. © 2015 The Association of Anaesthetists of Great Britain and Ireland.

How does a tidal embayment morphodynamically react on sea level rise?

NASA Astrophysics Data System (ADS)

van der Wegen, Mick

2010-05-01

Conditions for (assumed) equilibrium in tidal embayments have been studied extensively in the past years with morphodynamic 1D models (Van Dongeren and De Vriend, 1994; Schuttelaars and de Swart, 1996, 2000; Lanzoni and Seminara, 2002) and 2D models (Hibma et al. [2003], Van der Wegen and Roelvink [2008]) Van der Wegen et al 2008). The current research addresses the impact of sea level rise on tidal embayments. Although effects of sea level rise may only become apparent after decades, the character of the embayment can change considerably. Examples are the (dis)appearance or re-allocation of intertidal flats, increased tidal resonance, shift from sediment export to import, deepening of channel area and other related (ecological) parameters. The research applies a 2D morphodynamic model (Delft3D) in an idealized environment. The model is based on the 2 D shallow water equations, the Engelund -Hansen transport formula and includes bed slope effects, drying and flooding procedures and an advanced morphodynamic update scheme (Roelvink 2006). The initial condition of the bathymetry is generated by 3000 years of morphodynamic calculations in a 80 km long and 2.5 km wide rectangular tidal embayment under constant M2 tidal forcing conditions (Van der Wegen and Roelvink [2008]). After this period sea level rise gradually developing towards a rate of 0.4 m/century is added to the boundary conditions. Model results describe development towards less intertidal area and a transition from an exporting system to a importing system. Model results are evaluated in terms of M2, M4 and M6 tidal constituents as well as against Vs/Vc (shoal volume over channel volume) versus a/h (amplitude over water depth) relationship as proposed by Friedrichs and Aubrey (1988). Although the model describes morphodynamic development in a strongly idealized environment the results can provide an excellent tool to systematically study the impact of sea level rise in tidal embayments as well as the time scales of dominant underlying resulting transport mechanisms and processes. DISSANAYAKE, D.M.P.K; RANASINGHE, R. and ROELVINK, J.A., 2009. Effect of Sea Level Rise in tidal inlet evolution: a numerical modelling approach. Journal of Coastal Research, SI 56 (Proceedings of the 10th International Coastal Symposium), pg - pg. Lisbon, Portugal. Friedrichs, C. T., and D. G. Aubrey (1988), Non-linear tidal distortion in shallow well mixed estuaries: A synthesis, Estuarine Coastal Shelf Sci.,27, 521- 545, doi:10.1016/0272-7714(88)90082-0. Hibma, A., H.M. Schuttelaars, and H. J. de Vriend (2003b), Initial formation and long-term evolution of channel-shoal patterns in estuaries, in Proc. 3rd RCEM conf.edited by A. Sánchez -Acrilla and A. Bateman, pp. 740-760, IAHR., Barcelona, Spain. Lanzoni, S., and G. Seminara (2002), Long-term evolution and morphodynamic equilibrium of tidal channels, J. Geophys. Res., 107(C1), 3001, doi:10.1029/2000JC000468. Roelvink, J. A. (2006), Coastal morphodynamic evolution techniques, J. Coastal Eng., 53, 177-187. Schuttelaars, H. M., and H. E. De Swart (1996), An idealized long termmorphodynamic model of a tidal embayment, Eur. J. Mech. B Fluids, 15(1), 55-80. Schuttelaars, H. M., and H. E. De Swart (2000), Multiple morphodynamic equilibria in tidal embayments, J. Geophys. Res., 105(C10), 24,105 - 24,118. Van Dongeren, A. D., and H. J. De Vriend (1994), A model of morphological behaviour of tidal basins, Coastal Eng., 22, 287- 310. van der Wegen, M., and J. A. Roelvink (2008), Long-term morphodynamic evolution of a tidal embayment using a twodimensional, process-based model, J. Geophys. Res., 113, C03016, doi:10.1029/2006JC003983 van der Wegen, M., Z. B. Wang, H. H. G. Savenije, and J. A. Roelvink (2008), Long-term morphodynamic evolution and energy dissipation in a coastal plain, tidal embayment, J. Geophys. Res., 113, F03001, doi:10.1029/2007JF000898

Dynamical Tidal Response of a Rotating Neutron Star

NASA Astrophysics Data System (ADS)

Landry, Philippe; Poisson, Eric

2017-01-01

The gravitational wave phase of a neutron star (NS) binary is sensitive to the deformation of the NS that results from its companion's tidal influence. In a perturbative treatment, the tidal deformation can be characterized by a set of dimensionless constants, called Love numbers, which depend on the NS equation of state. For static NSs, one type of Love number encodes the response to gravitoelectric tidal fields (associated with mass multipole moments), while another does likewise for gravitomagnetic fields (associated with mass currents). A NS subject to a gravitomagnetic tidal field develops internal fluid motions through gravitomagnetic induction; the fluid motions are irrotational, provided the star is non-rotating. When the NS is allowed to rotate, the situation is complicated by couplings between the tidal field and the star's spin. The problem becomes tractable in the slow-rotation limit. In this case, the fluid motions induced by an external gravitomagnetic field are fully dynamical, even if the tidal field is stationary: interior metric and fluid variables are time-dependent, and vary on the timescale of the rotation period. Remarkably, the exterior geometry of the NS remains time-independent.

VISCOELASTIC MODELS OF TIDALLY HEATED EXOMOONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dobos, Vera; Turner, Edwin L., E-mail: dobos@konkoly.hu

2015-05-01

Tidal heating of exomoons may play a key role in their habitability, since the elevated temperature can melt the ice on the body even without significant solar radiation. The possibility of life has been intensely studied on solar system moons such as Europa or Enceladus where the surface ice layer covers a tidally heated water ocean. Tidal forces may be even stronger in extrasolar systems, depending on the properties of the moon and its orbit. To study the tidally heated surface temperature of exomoons, we used a viscoelastic model for the first time. This model is more realistic than themore » widely used, so-called fixed Q models because it takes into account the temperature dependence of the tidal heat flux and the melting of the inner material. Using this model, we introduced the circumplanetary Tidal Temperate Zone (TTZ), which strongly depends on the orbital period of the moon and less on its radius. We compared the results with the fixed Q model and investigated the statistical volume of the TTZ using both models. We have found that the viscoelastic model predicts 2.8 times more exomoons in the TTZ with orbital periods between 0.1 and 3.5 days than the fixed Q model for plausible distributions of physical and orbital parameters. The viscoelastic model provides more promising results in terms of habitability because the inner melting of the body moderates the surface temperature, acting like a thermostat.« less

Slow and deep respiration suppresses steady-state sympathetic nerve activity in patients with chronic heart failure: from modeling to clinical application.

PubMed

Harada, Daisuke; Asanoi, Hidetsugu; Takagawa, Junya; Ishise, Hisanari; Ueno, Hiroshi; Oda, Yoshitaka; Goso, Yukiko; Joho, Shuji; Inoue, Hiroshi

2014-10-15

Influences of slow and deep respiration on steady-state sympathetic nerve activity remain controversial in humans and could vary depending on disease conditions and basal sympathetic nerve activity. To elucidate the respiratory modulation of steady-state sympathetic nerve activity, we modeled the dynamic nature of the relationship between lung inflation and muscle sympathetic nerve activity (MSNA) in 11 heart failure patients with exaggerated sympathetic outflow at rest. An autoregressive exogenous input model was utilized to simulate entire responses of MSNA to variable respiratory patterns. In another 18 patients, we determined the influence of increasing tidal volume and slowing respiratory frequency on MSNA; 10 patients underwent a 15-min device-guided slow respiration and the remaining 8 had no respiratory modification. The model predicted that a 1-liter, step increase of lung volume decreased MSNA dynamically; its nadir (-33 ± 22%) occurred at 2.4 s; and steady-state decrease (-15 ± 5%), at 6 s. Actually, in patients with the device-guided slow and deep respiration, respiratory frequency effectively fell from 16.4 ± 3.9 to 6.7 ± 2.8/min (P < 0.0001) with a concomitant increase in tidal volume from 499 ± 206 to 1,177 ± 497 ml (P < 0.001). Consequently, steady-state MSNA was decreased by 31% (P < 0.005). In patients without respiratory modulation, there were no significant changes in respiratory frequency, tidal volume, and steady-state MSNA. Thus slow and deep respiration suppresses steady-state sympathetic nerve activity in patients with high levels of resting sympathetic tone as in heart failure. Copyright © 2014 the American Physiological Society.

Factors Influencing Continuous Breath Signal in Intubated and Mechanically-Ventilated Intensive Care Unit Patients Measured by an Electronic Nose

PubMed Central

Leopold, Jan Hendrik; Abu-Hanna, Ameen; Colombo, Camilla; Sterk, Peter J.; Schultz, Marcus J.; Bos, Lieuwe D. J.

2016-01-01

Introduction: Continuous breath analysis by electronic nose (eNose) technology in the intensive care unit (ICU) may be useful in monitoring (patho) physiological changes. However, the application of breath monitoring in a non-controlled clinical setting introduces noise into the data. We hypothesized that the sensor signal is influenced by: (1) humidity in the side-stream; (2) patient-ventilator disconnections and the nebulization of medication; and (3) changes in ventilator settings and the amount of exhaled CO2. We aimed to explore whether the aforementioned factors introduce noise into the signal, and discuss several approaches to reduce this noise. Methods: Study in mechanically-ventilated ICU patients. Exhaled breath was monitored using a continuous eNose with metal oxide sensors. Linear (mixed) models were used to study hypothesized associations. Results: In total, 1251 h of eNose data were collected. First, the initial 15 min of the signal was discarded. There was a negative association between humidity and Sensor 1 (Fixed-effect β: −0.05 ± 0.002) and a positive association with Sensors 2–4 (Fixed-effect β: 0.12 ± 0.001); the signal was corrected for this noise. Outliers were most likely due to noise and therefore removed. Sensor values were positively associated with end-tidal CO2, tidal volume and the pressure variables. The signal was corrected for changes in these ventilator variables after which the associations disappeared. Conclusion: Variations in humidity, ventilator disconnections, nebulization of medication and changes of ventilator settings indeed influenced exhaled breath signals measured in ventilated patients by continuous eNose analysis. We discussed several approaches to reduce the effects of these noise inducing variables. PMID:27556467

MIT Project Apophis: Surface Evaulation & Tomography (SET) Mission Study for the April 2029 Earth Encounter

NASA Astrophysics Data System (ADS)

Binzel, R. P.; Earle, A. M.; Vanatta, M.; Miller, D. W.

2017-12-01

Nature is providing a once-per-thousand year opportunity to study the geophysical outcome induced on an unprecedentedly large (350 meter) asteroid making an extremely close passage by the Earth (inside the distance of geosynchronous satellites) on Friday April 13, 2029. The aircraft carrier-sized (estimated 20 million metric ton) asteroid is named Apophis. While many previous spacecraft missions have studied asteroids, none has ever had the opportunity to study "live" the outcome of planetary tidal forces on their shapes, spin states, surface geology, and internal structure. Beyond the science interest directly observing this planetary process, the Apophis encounter provides an invaluable opportunity to gain knowledge for any eventuality of a known asteroid found to be on a certain impact trajectory. MIT's Project Apophis [1] is our response to nature's generous opportunity by developing a detailed mission concept for sending a spacecraft to orbit Apophis with the objectives of surveying its surface and interior structure before, during, and after its 2029 near-Earth encounter. The Surface Evaluation & Tomography (SET) mission concept we present is designed toward accomplishing three key science objectives: (1) bulk physical characterization, (2) internal structure, and (3) long-term orbit tracking. For its first mission objective, SET will study Apophis' bulk properties, including: shape, size, mass, volume, bulk density, surface geology, and composition, rotation rate, and spin state. The second mission objective is to characterize Apophis' internal structure before and after the encounter to determine its strength and cohesion - including tidally induced changes. Finally, the third objective studies the process of thermal re-radiation and consequential Yarkovsky drift, whose results will improve orbit predictions for Apophis as well as other potentially hazardous asteroids. [1] https://eapsweb.mit.edu/mit-project-apophis

Coupled Landscape and Channel Dynamics in the Ganges-Brahmaputra Tidal Deltaplain, Southwest Bangladesh

NASA Astrophysics Data System (ADS)

Bomer, J.; Wilson, C.; Hale, R. P.

2017-12-01

In the Ganges-Brahmaputra Delta (GBD) and other tide-dominated systems, periodic flooding of the land surface during the tidal cycle promotes sediment accretion and surface elevation gain over time. However, over the past several decades, anthropogenic modification of the GBD tidal deltaplain through embankment construction has precluded sediment delivery to catchment areas, leading to widespread channel siltation and subsidence in poldered landscapes. Amongst the current discussion on GBD sustainability, the relationship between tidal inundation period and resultant sedimentation in natural and embanked settings remains unclear. Moreover, an evaluation of how riparian sedimentology and stratigraphic architecture changes across the GBD tidal-fluvial spectrum is notably absent, despite its critical importance in assessing geomorphic change in human-impacted transitional environments. To provide local-scale, longitudinal trends of coupled landscape-channel dynamics, an array of surface elevation tables, groundwater piezometers, and sediment traps deployed in natural and embanked settings have been monitored seasonally over a time span of 4 years. This knowledge base will be extended across the GBD tidal-fluvial transition by collecting sediment cores from carefully selected point bars along the Gorai River. Sediments will be analyzed for lithologic, biostratigraphic, and geochemical properties to provide an integrated framework for discerning depositional zones and associated facies assemblages across this complex transitional environment. Preliminary comparisons of accretion and hydroperiod data suggest that inundation duration strongly governs mass accumulation on the intertidal platform, though other factors such as mass extraction from sediment source and vegetation density may play secondary roles.

Cardiovascular, electrodermal, and respiratory response patterns to fear- and sadness-inducing films.

PubMed

Kreibig, Sylvia D; Wilhelm, Frank H; Roth, Walton T; Gross, James J

2007-09-01

Responses to fear- and sadness-inducing films were assessed using a broad range of cardiovascular (heart rate, T-wave amplitude, low- and high-frequency heart rate variability, stroke volume, preejection period, left-ventricular ejection time, Heather index, blood pressure, pulse amplitude and transit time, and finger temperature), electrodermal (level, response rate, and response amplitude), and respiratory (rate, tidal volume and its variability, inspiratory flow rate, duty cycle, and end-tidal pCO(2)) measures. Subjective emotional experience and facial behavior (Corrugator Supercilii and Zygomaticus Major EMG) served as control measures. Results indicated robust differential physiological response patterns for fear, sadness, and neutral (mean classification accuracy 85%). Findings are discussed in terms of the fight-flight and conservation-withdrawal responses and possible limitations of a valence-arousal categorization of emotion in affective space.

Airway Strain during Mechanical Ventilation in an Intact Animal Model

PubMed Central

Sinclair, Scott E.; Molthen, Robert C.; Haworth, Steve T.; Dawson, Christopher A.; Waters, Christopher M.

2007-01-01

Rationale: Mechanical ventilation with large tidal volumes causes ventilator-induced lung injury in animal models. Little direct evidence exists regarding the deformation of airways in vivo during mechanical ventilation, or in the presence of positive end-expiratory pressure (PEEP). Objectives: To measure airway strain and to estimate airway wall tension during mechanical ventilation in an intact animal model. Methods: Sprague-Dawley rats were anesthetized and mechanically ventilated with tidal volumes of 6, 12, and 25 cm3/kg with and without 10–cm H2O PEEP. Real-time tantalum bronchograms were obtained for each condition, using microfocal X-ray imaging. Images were used to calculate circumferential and longitudinal airway strains, and on the basis of a simplified mathematical model we estimated airway wall tensions. Measurements and Main Results: Circumferential and longitudinal airway strains increased with increasing tidal volume. Levels of mechanical strain were heterogeneous throughout the bronchial tree. Circumferential strains were higher in smaller airways (less than 800 μm). Airway size did not influence longitudinal strain. When PEEP was applied, wall tensions increased more rapidly than did strain levels, suggesting that a “strain limit” had been reached. Airway collapse was not observed under any experimental condition. Conclusions: Mechanical ventilation results in significant airway mechanical strain that is heterogeneously distributed in the uninjured lung. The magnitude of circumferential but not axial strain varies with airway diameter. Airways exhibit a “strain limit” above which an abrupt dramatic rise in wall tension is observed. PMID:17626911

Placement of Intubating Laryngeal Mask Airway Is Easier than Placement of Laryngeal Tube during Manual In-Line Stabilisation of The Neck

PubMed Central

Komatsu, R.; Nagata, O.; Kamata, K.; Yamagata, K.; Sessler, D.I.; Ozaki, M.

2005-01-01

Summary We compared the usefulness of the laryngeal tube (LT) with the intubating laryngeal mask airway (ILMA) in 51 patients whose necks were stabilised by manual in-line traction. After induction of anaesthesia and neuromuscular block, the LT and ILMA were inserted consecutively in a randomised, crossover design. During pressure-controlled ventilation (20 cmH2O inspiratory pressure), we measured insertion attempts, time to establish positive-pressure ventilation, tidal volume, gastric insufflation, and minimum airway pressure at which gas leaked around the cuff. Data were compared using Wilcoxon signed-rank tests; P<0.05 was considered significant. Insertion was more difficult with the LT (successful at first attempt in 16 patients) than with the ILMA (successful at first attempt in 42 patients, P<0.0001). Time required for insertion was longer for the LT (28 [23–35] sec, median [interquartile range]) than the ILMA (20 [15–25] sec, P=0.0009). Tidal volume was less for the LT (440 [290–670] ml) than the ILMA. (630 [440–750] ml, P=0.013). Minimum airway pressure at which gas leak occurred and incidence of gastric insufflation were similar with two devices. In patients whose necks were stabilised with manual in-line traction, insertion of the ILMA was easier and quicker than insertion of the LT and tidal volume was greater with the ILMA than the LT. PMID:15644005

Tidal characteristics of the gulf of Tonkin

NASA Astrophysics Data System (ADS)

Minh, Nguyen Nguyet; Patrick, Marchesiello; Florent, Lyard; Sylvain, Ouillon; Gildas, Cambon; Damien, Allain; Van Uu, Dinh

2014-12-01

The Gulf of Tonkin, situated in the South China Sea, is a zone of strong ecological, touristic and economic interest. Improving our knowledge of its hydro-sedimentary processes is of great importance to the sustainable development of the area. The scientific objective of this study is to revisit the dominant physical processes that characterize tidal dynamics in the Gulf of Tonkin using a high-resolution model and combination of all available data. Particular attention is thus given to model-data cross-examination using tidal gauges and coastal satellite altimetry and to model calibration derived from a set of sensitivity experiments to model parameters. The tidal energy budget of the gulf (energy flux and dissipation) is then analyzed and its resonance properties are evaluated and compared with idealized models and observations. Then, the tidal residual flow in both Eulerian and Lagrangian frameworks is evaluated. Finally, the problem of tidal frontogenesis is addressed to explain the observed summer frontal structures in chlorophyll concentrations.

Pulmonary function in obese vs non-obese cats.

PubMed

García-Guasch, Laín; Caro-Vadillo, Alicia; Manubens-Grau, Jordi; Carretón, Elena; Camacho, Aparecido A; Montoya-Alonso, José Alberto

2015-06-01

Obesity is a risk factor in the development of several respiratory diseases. Lung volumes tend to be decreased, especially expiratory reserve volume, increasing expiratory flow limitation during tidal breathing. Barometric whole-body plethysmography is a non-invasive pulmonary function test that allows a dynamic study of breathing patterns. The objective of this study was to compare pulmonary function variables between obese and non-obese cats through the use of barometric whole-body plethysmography. Nine normal-weight and six obese cats were placed in the plethysmograph chamber, and different respiratory variables were measured. There was a significant decrease in tidal volume per kilogram (P = 0.003), minute volume per kilogram (P = 0.001) and peak inspiratory and expiratory flows per kilogram (P = 0.001) in obese cats compared with non-obese cats. Obesity failed to demonstrate a significant increase in bronchoconstriction index variable enhanced pause (Penh), as previously reported in humans and dogs. The results show that feline obesity impairs pulmonary function in cats, although a significant increase in bronchoconstriction indexes was not observed. Non-invasive barometric whole-body plethysmography can help characterise mechanical dysfunction of the airways in obese cats. © ISFM and AAFP 2014.

Role of neurotensin and opioid receptors in the cardiorespiratory effects of [Ile⁹]PK20, a novel antinociceptive chimeric peptide.

PubMed

Kaczyńska, Katarzyna; Szereda-Przestaszewska, Małgorzata; Kleczkowska, Patrycja; Lipkowski, Andrzej W

2014-10-15

Ile(9)PK20 is a novel hybrid of opioid-neurotensin peptides synthesized from the C-terminal hexapeptide of neurotensin and endomorphin-2 pharmacophore. This chimeric compound shows potent central and peripheral antinociceptive activity in experimental animals, however nothing is known about its influence on the respiratory and cardiovascular parameters. The present study was designed to determine the cardiorespiratory effects exerted by an intravenous injection (i.v.) of [Ile(9)]PK20. Share of the vagal afferentation and the contribution of NTS1 neurotensin and opioid receptors were tested. Intravenous injection of the hybrid at a dose of 100 μg/kg in the intact, anaesthetized rats provoked an increase in tidal volume preceded by a prompt short-lived decrease. Immediately after the end of injection brief acceleration of the respiratory rhythm appeared, and was ensued by the slowing down of breathing. Changes in respiration were concomitant with a bi-phasic response of the blood pressure: an immediate increase was followed by a sustained hypotension. Midcervical vagotomy eliminated the increase in tidal volume and respiratory rate responses. Antagonist of opioid receptors - naloxone hydrochloride eliminated only [Ile(9)]PK20-evoked decline in tidal volume response. Blockade of NTS1 receptors with an intravenous dose of SR 142,948, lessened the remaining cardiorespiratory effects. This study depicts that [Ile(9)]PK20 acting through neurotensin NTS1 receptors augments the tidal component of the breathing pattern and activates respiratory timing response through the vagal pathway. Blood pressure effects occur outside vagal afferentation and might result from activation of the central and peripheral vascular NTS1 receptors. In summary the respiratory effects of the hybrid appeared not to be profound, but they were accompanied with unfavourable prolonged hypotension. Copyright © 2014 Elsevier B.V. All rights reserved.

Oral mask ventilation is more effective than face mask ventilation after nasal surgery.

PubMed

Yazicioğlu, Dilek; Baran, Ilkay; Uzumcugil, Filiz; Ozturk, Ibrahim; Utebey, Gulten; Sayın, M Murat

2016-06-01

To evaluate and compare the face mask (FM) and oral mask (OM) ventilation techniques during anesthesia emergence regarding tidal volume, leak volume, and difficult mask ventilation (DMV) incidence. Prospective, randomized, crossover study. Operating room, training and research hospital. American Society of Anesthesiologists physical status I and II adult patients scheduled for nasal surgery. Patients in group FM-OM received FM ventilation first, followed by OM ventilation, and patients in group OM-FM received OM ventilation first, followed by FM ventilation, with spontaneous ventilation after deep extubation. The FM ventilation was applied with the 1-handed EC-clamp technique. The OM was placed only over the mouth, and the 1-handed EC-clamp technique was used again. A child's size FM was used for the OM ventilation technique, the mask was rotated, and the inferior part of the mask was placed toward the nose. The leak volume (MVleak), mean airway pressure (Pmean), and expired tidal volume (TVe) were assessed with each mask technique for 3 consecutive breaths. A mask ventilation grade ≥3 was considered DMV. DMV occurred more frequently during FM ventilation (75% with FM vs 8% with OM). In the FM-first sequence, the mean TVe was 249±61mL with the FM and 455±35mL with the OM (P=.0001), whereas in the OM-first sequence, it was 276±81mL with the FM and 409±37mL with the OM (P=.0001). Regardless of the order used, the OM technique significantly decreased the MVleak and increased the TVe when compared to the FM technique. During anesthesia emergence after nasal surgery the OM may offer an effective ventilation method as it decreases the incidence of DMV and the gas leak around the mask and provides higher tidal volume delivery compared with FM ventilation. Copyright © 2016 Elsevier Inc. All rights reserved.

On the Specification of Upward-Propagating Tides for ICON Science Investigations

NASA Astrophysics Data System (ADS)

Forbes, Jeffrey M.; Zhang, Xiaoli; Hagan, Maura E.; England, Scott L.; Liu, Guiping; Gasperini, Federico

2017-10-01

The National Center for Atmospheric Research (NCAR) Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM) will provide a physics-based context for the interpretation of ICON measurements. To optimize the realism of the model simulations, ICON wind and temperature measurements near the ˜97 km lower boundary of the TIEGCM will be used to specify the upward-propagating tidal spectrum at this altitude. This will be done by fitting a set of basis functions called Hough Mode Extensions (HMEs) to 27-day mean tidal winds and temperatures between 90 and 105 km altitude and between 12 °S and 42 °N latitude on a day-by-day basis. The current paper assesses the veracity of the HME fitting methodology given the restricted latitude sampling and the UT-longitude sampling afforded by the MIGHTI instrument viewing from the ICON satellite, which will be in a circular 27° inclination orbit. These issues are investigated using the output from a reanalysis-driven global circulation model, which contains realistic variability of the important tidal components, as a mock data set. ICON sampling of the model reveals that the 27-day mean diurnal and semidiurnal tidal components replicate well the 27-day mean tidal components obtained from full synoptic sampling of the model, but the terdiurnal tidal components are not faithfully reproduced. It is also demonstrated that reconstructed tidal components based on HME fitting to the model tides between 12 °S and 42 °N latitude provide good approximations to the major tidal components expected to be encountered during the ICON mission. This is because the constraints provided by fitting both winds and temperatures over the 90-105 km height range are adequate to offset the restricted sampling in latitude. The boundary conditions provided by the methodology described herein will greatly enhance the ability of the TIEGCM to provide a physical framework for interpreting atmosphere-ionosphere coupling in ICON observations due to atmospheric tides.

Life on the Tidal Mudflats: Elkhorn Slough.

ERIC Educational Resources Information Center

Andresen, Ruth

Life in an estuarine environment is studied in this set of audio-visual materials prepared for grades 6-12. A 71-frame colored filmstrip, cassette tape narration, and teacher's guide focus upon Elkhorn Slough, a tidal mudflat in the Monterey Bay area, California. Topics examined range from river drainage and the effects of pollution on living…

New Algorithm Identifies Tidal Streams Oriented Along our Line-of-Sight

NASA Astrophysics Data System (ADS)

Lin, Ziyi; Newberg, Heidi; Amy, Paul; Martin, Charles Harold; Rockcliffe, Keighley E.

2018-01-01

The known dwarf galaxy tidal streams in the Milky Way are primarily oriented perpendicular to our line-of-sight. That is because they are concentrated into an observable higher-surface-brightness feature at a particular distance, or because they tightly cluster in line-of-sight velocity in a particular direction. Streams that are oriented along our line-of-sight are spread over a large range of distances and velocities. However, these distances and velocities are correlated in predicable ways. We used a set of randomly oriented Milky Way orbits to develop a technique that bins stars in combinations of distance and velocity that are likely for tidal streams. We applied this technique to identify previously unknown tidal streams in a set of blue horizontal branch stars in the first quadrant from Data Release 10 of the Sloan Digital Sky Survey (SDSS). This project was supported by NSF grant AST 16-15688, a Rensselaer Presidential Fellowship, the NASA/NY Space Grant fellowship, and contributions made by The Marvin Clan, Babette Josephs, Manit Limlamai, and the 2015 Crowd Funding Campaign to Support Milky Way Research.

Early application of airway pressure release ventilation may reduce the duration of mechanical ventilation in acute respiratory distress syndrome.

PubMed

Zhou, Yongfang; Jin, Xiaodong; Lv, Yinxia; Wang, Peng; Yang, Yunqing; Liang, Guopeng; Wang, Bo; Kang, Yan

2017-11-01

Experimental animal models of acute respiratory distress syndrome (ARDS) have shown that the updated airway pressure release ventilation (APRV) methodologies may significantly improve oxygenation, maximize lung recruitment, and attenuate lung injury, without circulatory depression. This led us to hypothesize that early application of APRV in patients with ARDS would allow pulmonary function to recover faster and would reduce the duration of mechanical ventilation as compared with low tidal volume lung protective ventilation (LTV). A total of 138 patients with ARDS who received mechanical ventilation for <48 h between May 2015 to October 2016 while in the critical care medicine unit (ICU) of the West China Hospital of Sichuan University were enrolled in the study. Patients were randomly assigned to receive APRV (n = 71) or LTV (n = 67). The settings for APRV were: high airway pressure (P high ) set at the last plateau airway pressure (P plat ), not to exceed 30 cmH 2 O) and low airway pressure ( P low ) set at 5 cmH 2 O; the release phase (T low ) setting adjusted to terminate the peak expiratory flow rate to ≥ 50%; release frequency of 10-14 cycles/min. The settings for LTV were: target tidal volume of 6 mL/kg of predicted body weight; P plat not exceeding 30 cmH 2 O; positive end-expiratory pressure (PEEP) guided by the PEEP-FiO 2 table according to the ARDSnet protocol. The primary outcome was the number of days without mechanical ventilation from enrollment to day 28. The secondary endpoints included oxygenation, P plat , respiratory system compliance, and patient outcomes. Compared with the LTV group, patients in the APRV group had a higher median number of ventilator-free days {19 [interquartile range (IQR) 8-22] vs. 2 (IQR 0-15); P < 0.001}. This finding was independent of the coexisting differences in chronic disease. The APRV group had a shorter stay in the ICU (P = 0.003). The ICU mortality rate was 19.7% in the APRV group versus 34.3% in the LTV group (P = 0.053) and was associated with better oxygenation and respiratory system compliance, lower P plat , and less sedation requirement during the first week following enrollment (P < 0.05, repeated-measures analysis of variance). Compared with LTV, early application of APRV in patients with ARDS improved oxygenation and respiratory system compliance, decreased P plat and reduced the duration of both mechanical ventilation and ICU stay.

Impacts of marine renewable energy scheme operation on the eutrophication potential of the Severn Estuary, UK

NASA Astrophysics Data System (ADS)

Kadiri, Margaret; Kay, David; Ahmadian, Reza; Bockelmann-Evans, Bettina; Falconer, Roger; Bray, Michaela

2013-04-01

In recent years there has being growing global interest in the generation of electricity from renewable resources. Amongst these, marine energy resource is now being considered to form a significant part of the energy mix, with plans for the implementation of several marine renewable energy schemes such as barrages and tidal stream turbines around the UK in the near future. Although marine energy presents a great potential for future electricity generation, there are major concerns over its potential impacts, particularly barrages, on the hydro-environment. Previous studies have shown that a barrage could significantly alter the hydrodynamic regime and tidal flow characteristics of an estuary, with changes to sediment transport (Kadiri et al., 2012). However, changes to nutrients have been overlooked to date. Hence, considerable uncertainty remains as to how a barrage would affect the trophic status of an estuary. This is particularly important because eutrophication can lead to algal toxin production and increased mortality of aquatic invertebrates and fish populations. Therefore, this study examines the impacts of the two different modes of operation of a barrage (i.e. ebb generation and flood-ebb generation) on the eutrophication potential of the Severn Estuary using a simplified model developed by the UK's Comprehensive Studies Task Team (CSTT). The model uses a set of equations and site-specific input data to predict equilibrium dissolved nutrient concentrations, phytoplankton biomass, light-controlled phytoplankton growth rate and primary production which are compared against CSTT set standards for assessing the eutrophic status of estuaries and coastal waters. The estuary volume and tidal flushing time under the two operating modes were estimated using a hydrodynamic model and field surveys were conducted to obtain dissolved nitrate and phosphate concentrations which served as input data. The predicted equilibrium dissolved nitrate and phosphate concentrations were slightly greater under ebb generation compared to flood-ebb generation. However, the concentrations did not exceed the CSTT standard indicating that hypernutrification is not likely to occur. Similarly, the predicted phytoplankton biomass and light-controlled growth rate under both ebb and flood-ebb generation were less than the CSTT standards suggesting no likelihood of eutrophication. The predicted phytoplankton production, however, was significantly greater under ebb generation compared to flood-ebb generation due to restricted tidal flushing decreasing nutrient dispersion and increasing the residence time of nutrient in the region upstream of the barrage. This study also examines the wider positive ecological implications of these findings for the Severn Estuary. Reference Kadiri, M., Ahmadian, R., Bockelmann-Evans, B., Rauen, W., and Falconer, R., 2012. A review of the potential water quality impacts of tidal renewable energy systems. Renewable and Sustainable Energy Reviews, 16: 329- 341.

Land Use in Korean Tidal Wetlands: Impacts and Management Strategies

NASA Astrophysics Data System (ADS)

Hong, Sun-Kee; Koh, Chul-Hwan; Harris, Richard R.; Kim, Jae-Eun; Lee, Jeom-Sook; Ihm, Byung-Sun

2010-05-01

The coastal landscapes in southwestern Korea include a diverse array of tidal wetlands and salt marshes. These coastal zones link the ecological functions of marine tidal wetlands and freshwater ecosystems with terrestrial ecosystems. They are rich in biological diversity and play important roles in sustaining ecological health and processing environmental pollutants. Korean tidal wetlands are particularly important as nurseries for economically important fishes and habitats for migratory birds. Diking, draining, tourism, and conversion to agricultural and urban uses have adversely affected Korean tidal wetlands. Recent large development projects have contributed to further losses. Environmental impact assessments conducted for projects affecting tidal wetlands and their surrounding landscapes should be customized for application to these special settings. Adequate environmental impact assessments will include classification of hydrogeomorphic units and consideration of their responses to biological and environmental stressors. As is true worldwide, Korean laws and regulations are changing to be more favorable to the conservation and protection of tidal wetlands. More public education needs to be done at the local level to build support for tidal wetland conservation. Some key public education points include the role of tidal wetlands in maintaining healthy fish populations and reducing impacts of nonpoint source pollution. There is also a need to develop procedures for integrating economic and environmental objectives within the overall context of sustainable management and land uses.

Land use in Korean tidal wetlands: impacts and management strategies.

PubMed

Hong, Sun-Kee; Koh, Chul-Hwan; Harris, Richard R; Kim, Jae-Eun; Lee, Jeom-Sook; Ihm, Byung-Sun

2010-05-01

The coastal landscapes in southwestern Korea include a diverse array of tidal wetlands and salt marshes. These coastal zones link the ecological functions of marine tidal wetlands and freshwater ecosystems with terrestrial ecosystems. They are rich in biological diversity and play important roles in sustaining ecological health and processing environmental pollutants. Korean tidal wetlands are particularly important as nurseries for economically important fishes and habitats for migratory birds. Diking, draining, tourism, and conversion to agricultural and urban uses have adversely affected Korean tidal wetlands. Recent large development projects have contributed to further losses. Environmental impact assessments conducted for projects affecting tidal wetlands and their surrounding landscapes should be customized for application to these special settings. Adequate environmental impact assessments will include classification of hydrogeomorphic units and consideration of their responses to biological and environmental stressors. As is true worldwide, Korean laws and regulations are changing to be more favorable to the conservation and protection of tidal wetlands. More public education needs to be done at the local level to build support for tidal wetland conservation. Some key public education points include the role of tidal wetlands in maintaining healthy fish populations and reducing impacts of nonpoint source pollution. There is also a need to develop procedures for integrating economic and environmental objectives within the overall context of sustainable management and land uses.

Synchrotron imaging of the grasshopper tracheal system : morphological and physiological components of tracheal hypermetry.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Greenlee, K. J.; Henry, J. R.; Kirkton, S. D.

2009-11-01

As grasshoppers increase in size during ontogeny, they have mass specifically greater whole body tracheal and tidal volumes and ventilation than predicted by an isometric relationship with body mass and body volume. However, the morphological and physiological bases to this respiratory hypermetry are unknown. In this study, we use synchrotron imaging to demonstrate that tracheal hypermetry in developing grasshoppers (Schistocerca americana) is due to increases in air sacs and tracheae and occurs in all three body segments, providing evidence against the hypothesis that hypermetry is due to gaining flight ability. We also assessed the scaling of air sac structure andmore » function by assessing volume changes of focal abdominal air sacs. Ventilatory frequencies increased in larger animals during hypoxia (5% O{sub 2}) but did not scale in normoxia. For grasshoppers in normoxia, inflated and deflated air sac volumes and ventilation scaled hypermetrically. During hypoxia (5% O{sub 2}), many grasshoppers compressed air sacs nearly completely regardless of body size, and air sac volumes scaled isometrically. Together, these results demonstrate that whole body tracheal hypermetry and enhanced ventilation in larger/older grasshoppers are primarily due to proportionally larger air sacs and higher ventilation frequencies in larger animals during hypoxia. Prior studies showed reduced whole body tracheal volumes and tidal volume in late-stage grasshoppers, suggesting that tissue growth compresses air sacs. In contrast, we found that inflated volumes, percent volume changes, and ventilation were identical in abdominal air sacs of late-stage fifth instar and early-stage animals, suggesting that decreasing volume of the tracheal system later in the instar occurs in other body regions that have harder exoskeleton.« less

Ventilatory inhomogeneity determined from multiple-breath washouts during sustained microgravity on Spacelab SLS-1.

PubMed

Prisk, G K; Guy, H J; Elliott, A R; Paiva, M; West, J B

1995-02-01

We used multiple-breath N2 washouts (MBNW) to study the inhomogeneity of ventilation in four normal humans (mean age 42.5 yr) before, during, and after 9 days of exposure to microgravity on Spacelab Life Sciences-1. Subjects performed 20-breath MBNW at tidal volumes of approximately 700 ml and 12-breath MBNW at tidal volumes of approximately 1,250 ml. Six indexes of ventilatory inhomogeneity were derived from data from 1) distribution of specific ventilation (SV) from mixed-expired and 2) end-tidal N2, 3) change of slope of N2 washout (semilog plot) with time, 4) change of slope of normalized phase III of successive breaths, 5) anatomic dead space, and 6) Bohr dead space. Significant ventilatory inhomogeneity was seen in the standing position at normal gravity (1 G). When we compared standing 1 G with microgravity, the distributions of SV became slightly narrower, but the difference was not significant. Also, there were no significant changes in the change of slope of the N2 washout, change of normalized phase III slopes, or the anatomic and Bohr dead spaces. By contrast, transition from the standing to supine position in 1 G resulted in significantly broader distributions of SV (P < 0.05) and significantly greater changes in the changes in slope of the N2 washouts (P < 0.001), indicating more ventilatory inhomogeneity in that posture. Thus these techniques can detect relatively small changes in ventilatory inhomogeneity. We conclude that the primary determinants of ventilatory inhomogeneity during tidal breathing in the upright posture are not gravitational in origin.

Ventilatory inhomogeneity determined from multiple-breath washouts during sustained microgravity on Spacelab SLS-1

NASA Technical Reports Server (NTRS)

Prisk, G. Kim; Guy, Harold J. B.; Elliott, Ann R.; Paiva, Manuel; West, John B.

1995-01-01

We used multiple-breath N2 washouts (MBNW) to study the homogeneity of ventilation in four normal humans (mean age 42.5 yr) before, during, and after 9 days of exposure to microgravity on Spacelab Life Sciences-1. Subjects performed 20-breath MBNW at tidal volumes of approximately 700 ml and 12-breath MBNW at tidal volumes of approximately 1,250 ml. Six indexes of ventilatory inhomogeneity were derived from data from (1) distribution of specific ventilation (SV) from mixed-expired and (2) end-tidal N2, (3) change of slope of N2 washout (semilog plot) with time, (4) change of slope of normalized phase III of successive breaths, (5) anatomic lead dead space, and (6) Bohr dead space. Significant ventilatory inhomogeneity was seen in the standing position at normal gravity (1 G). When we compared standing 1 G with microgravity, the distributions of SV became slightly narrower, but the difference was not significant. Also, there were no significant changes in the change of slope of the N2 washout, change of normalized phase III slopes, or the anatomic and Bohr dead spaces. By contrast, transition from the standing to supine position in 1 G resulted in significantly broader distributions of SV and significantly greater changes in the changes in slope of the N2 washouts, indicating more ventilatory inhomogeneity in that posture. Thus these techniques can detect relatively small changes in ventilatory inhomogeneity. We conclude that the primary determinants of ventilatory inhomogeneity during tidal breathing in the upright posture are not gravitational in origin.

Mapping the Tidal Destruction of the Hercules Dwarf: A Wide-field DECam Imaging Search for RR Lyrae Stars

NASA Astrophysics Data System (ADS)

Garling, Christopher; Willman, Beth; Sand, David J.; Hargis, Jonathan; Crnojević, Denija; Bechtol, Keith; Carlin, Jeffrey L.; Strader, Jay; Zou, Hu; Zhou, Xu; Nie, Jundan; Zhang, Tianmeng; Zhou, Zhimin; Peng, Xiyan

2018-01-01

We investigate the hypothesized tidal disruption of the Hercules ultra-faint dwarf galaxy (UFD). Previous tidal disruption studies of the Hercules UFD have been hindered by the high degree of foreground contamination in the direction of the dwarf. We bypass this issue by using RR Lyrae stars, which are standard candles with a very low field-volume density at the distance of Hercules. We use wide-field imaging from the Dark Energy Camera on CTIO to identify candidate RR Lyrae stars, supplemented with observations taken in coordination with the Beijing–Arizona Sky Survey on the Bok Telescope. Combining color, magnitude, and light-curve information, we identify three new RR Lyrae stars associated with Hercules. All three of these new RR Lyrae stars lie outside its published tidal radius. When considered with the nine RR Lyrae stars already known within the tidal radius, these results suggest that a substantial fraction of Hercules’ stellar content has been stripped. With this degree of tidal disruption, Hercules is an interesting case between a visibly disrupted dwarf (such as the Sagittarius dwarf spheroidal galaxy) and one in dynamic equilibrium. The degree of disruption also shows that we must be more careful with the ways we determine object membership when estimating dwarf masses in the future. One of the three discovered RR Lyrae stars sits along the minor axis of Hercules, but over two tidal radii away. This type of debris is consistent with recent models that suggest Hercules’ orbit is aligned with its minor axis.

43 CFR Appendix II to Part 11 - Format for Data Inputs and Modifications to the NRDAM/CME

Code of Federal Regulations, 2013 CFR

2013-10-01

....g., coral reef) and is classified as “landward” in Table 6.2, Volume I of the NRDAM/CME technical... kelp) or invertebrate reef (e.g., coral reef) and is classified as “seaward” in Table 6.2, Volume I of..., seagrass, or kelp) or invertebrate reef (e.g., coral reef). Tidal current—currents caused by alternating...

43 CFR Appendix II to Part 11 - Format for Data Inputs and Modifications to the NRDAM/CME

Code of Federal Regulations, 2014 CFR

2014-10-01

....g., coral reef) and is classified as “landward” in Table 6.2, Volume I of the NRDAM/CME technical... kelp) or invertebrate reef (e.g., coral reef) and is classified as “seaward” in Table 6.2, Volume I of..., seagrass, or kelp) or invertebrate reef (e.g., coral reef). Tidal current—currents caused by alternating...

43 CFR Appendix II to Part 11 - Format for Data Inputs and Modifications to the NRDAM/CME

Code of Federal Regulations, 2011 CFR

2011-10-01

....g., coral reef) and is classified as “landward” in Table 6.2, Volume I of the NRDAM/CME technical... kelp) or invertebrate reef (e.g., coral reef) and is classified as “seaward” in Table 6.2, Volume I of..., seagrass, or kelp) or invertebrate reef (e.g., coral reef). Tidal current—currents caused by alternating...

Physiologic and anti-G suit performance data from YF-16 flight tests

NASA Technical Reports Server (NTRS)

Gillingham, K. K.; Winter, W. R.

1976-01-01

Biomedical data were collected during high-G portions of 11 YF-16 test flights. Test pilots monitored revealed increased respiratory rate and volume, decreased tidal volume, and increased heart rate at higher G levels, with one pilot exhibiting various cardiac arrhythmias. Anti-G suit inflation and pressurization lags varied inversely with G-onset rate, and suit pressurization slope was near the design value.

Sleep-Disordered Breathing in Neuromuscular Disease: Diagnostic and Therapeutic Challenges.

PubMed

Aboussouan, Loutfi S; Mireles-Cabodevila, Eduardo

2017-10-01

Normal sleep-related rapid eye movement sleep atonia, reduced lung volumes, reduced chemosensitivity, and impaired airway dilator activity become significant vulnerabilities in the setting of neuromuscular disease. In that context, the compounding effects of respiratory muscle weakness and disease-specific features that promote upper airway collapse or cause dilated cardiomyopathy contribute to various sleep-disordered breathing events. The reduction in lung volumes with neuromuscular disease is further compromised by sleep and the supine position, exaggerating the tendency for upper airway collapse and desaturation with sleep-disordered breathing events. The most commonly identified events are diaphragmatic/pseudo-central, due to a decrease in the rib cage contribution to the tidal volume during phasic rapid eye movement sleep. Obstructive and central sleep apneas are also common. Noninvasive ventilation can improve survival and quality of sleep but should be used with caution in the context of dilated cardiomyopathy or significant bulbar symptoms. Noninvasive ventilation can also trigger sleep-disordered breathing events, including ineffective triggering, autotriggering, central sleep apnea, and glottic closure, which compromise the potential benefits of the intervention by increasing arousals, reducing adherence, and impairing sleep architecture. Polysomnography plays an important diagnostic and therapeutic role by correctly categorizing sleep-disordered events, identifying sleep-disordered breathing triggered by noninvasive ventilation, and improving noninvasive ventilation settings. Optimal management may require dedicated hypoventilation protocols and a technical staff well versed in the identification and troubleshooting of respiratory events. Copyright © 2017 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.

Rescue therapeutic strategy combining ultra-protective mechanical ventilation with extracorporeal CO2 removal membrane in near-fatal asthma with severe pulmonary barotraumas: A case report.

PubMed

Pavot, Arthur; Mallat, Jihad; Vangrunderbeeck, Nicolas; Thevenin, Didier; Lemyze, Malcolm

2017-10-01

Mechanical ventilation of severe acute asthma is still considered a challenging issue, mainly because of the gas trapping phenomenon with the potential for life-threatening barotraumatic pulmonary complications. Herein, we describe 2 consecutive cases of near-fatal asthma for whom the recommended protective mechanical ventilation approach using low tidal volume of 6 mL/kg and small levels of PEEP was rapidly compromised by giant pneumomediastinum with extensive subcutaneousemphysema. Near fatal asthma. A rescue therapeutic strategy combining extracorporeal CO2 removal membrane with ultra-protective extremely low tidal volume (3 mL/kg) ventilation was applied. Both patients survived hospital discharge. These 2 cases indicate that ECCO2R associated with ultra-protective ventilation could be an alternative to surgery in case of life-threatening barotrauma occurring under mechanical ventilation.

Modeling pesticide fate in a small tidal estuary

USGS Publications Warehouse

McCarthy, A.M.; Bales, J.D.; Cope, W.G.; Shea, D.

2007-01-01

The exposure analysis modeling system (EXAMS), a pesticide fate model developed by the U.S. Environmental Protection Agency, was modified to model the fate of the herbicides atrazine and metolachlor in a small tidally dominated estuary (Bath Creek) in North Carolina, USA where freshwater inflow accounts for only 3% of the total flow. The modifications simulated the changes that occur during the tidal cycle in the estuary, scenarios that are not possible with the original EXAMS model. Two models were created within EXAMS, a steady-state model and a time-variant tidally driven model. The steady-state model accounted for tidal flushing by simply altering freshwater input to yield an estuary residence time equal to that measured in Bath Creek. The tidal EXAMS model explicitly incorporated tidal flushing by modifying the EXAMS code to allow for temporal changes in estuary physical attributes (e.g., volume). The models were validated with empirical measurements of atrazine and metolachlor concentrations in the estuary shortly after herbicide application in nearby fields and immediately following a rain event. Both models provided excellent agreement with measured concentrations. The steady-state EXAMS model accurately predicted atrazine concentrations in the middle of the estuary over the first 3 days and under-predicted metolachlor by a factor of 2-3. The time-variant, tidally driven EXAMS model accurately predicted the rise and plateau of both herbicides over the 6-day measurement period. We have demonstrated the ability of these modified EXAMS models to be useful in predicting pesticide fate and exposure in small tidal estuaries. This is a significant improvement and expansion of the application of EXAMS, and given the wide use of EXAMS for surface water quality modeling by both researchers and regulators and the ability of EXAMS to interface with terrestrial models (e.g., pesticide root zone model) and bioaccumulation models, we now have an easily-accessible and widely accepted means of modeling chemical fate in estuaries. ?? 2006 Elsevier B.V. All rights reserved.

Inside anesthesia breathing circuits: time to reach a set sevoflurane concentration in toddlers and newborns: simulation using a test lung.

PubMed

Kern, Delphine; Larcher, Claire; Basset, Bertrand; Alacoque, Xavier; Fesseau, Rose; Samii, Kamran; Minville, Vincent; Fourcade, Olivier

2012-08-01

We measured the time it takes to reach the desired inspired anesthetic concentration using the Primus (Drägerwerk, AG, Lübeck, Germany) and the Avance (GE Datex-Ohmeda, Munich, Germany) anesthesia machines with toddler and newborn ventilation settings. The time to reach 95% of inspired target sevoflurane concentration was measured during wash-in from 0 to 6 vol% sevoflurane and during wash-out from 6 to 0 vol% with fresh gas flows equal to 1 and 2 times the minute ventilation. The Avance was faster than the Primus (65 seconds [95% confidence interval (CI): 55 to 78] vs 310 seconds [95% CI: 261 to 359]) at 1.5 L/min fresh gas flow, tidal volume of 50 mL, and 30 breaths/min. Times were shorter by the same magnitude at higher fresh gas flows and higher minute ventilation rates. The effect of doubling fresh gas flow was variable and less than expected. The Primus is slower during newborn than toddler ventilation, whereas the Avance's response time was the same for newborn and toddler ventilation. Our data confirm that the time to reach the target-inspired anesthetic concentration depends on breathing circuit volume, fresh gas flow, and minute ventilation.

Influence of drive and timing mechanisms on breathing pattern and ventilation during mental task performance.

PubMed

Wientjes, C J; Grossman, P; Gaillard, A W

1998-09-01

Assessment of multiple respiratory measures may provide insight into how behavioral demands affect the breathing pattern. This is illustrated by data from a study among 44 subjects, in which tidal volume, respiration rate, minute ventilation and indices of central drive and timing mechanisms were assessed via inductive plethysmography, in addition to end-tidal PCO2. After a baseline, three conditions of a memory comparison task were presented. The first two conditions differed only with regard to the presence or absence of feedback of performance (NFB and FB). In the third 'all-or-nothing' (AON) condition, subjects only received a monetary bonus, if their performance exceeded that of the previous two conditions. Minute ventilation increased from baseline to all task conditions, and from NFB and FB to AON. Respiration rate increased in all task conditions, but there were no differences between task conditions. Tidal volume decreased during NFB, but was equal to baseline during FB and AON. Of the respiratory control indices, inspiratory flow rate covaried much more closely with minute ventilation than duty cycle. The task performance induced a minor degree of hyperventilation. The discussion focusses on how behavioral demands affect respiratory control processes to produce alterations in breathing pattern and ventilation.

Slow Breathing and Hypoxic Challenge: Cardiorespiratory Consequences and Their Central Neural Substrates

PubMed Central

Critchley, Hugo D.; Nicotra, Alessia; Chiesa, Patrizia A.; Nagai, Yoko; Gray, Marcus A.; Minati, Ludovico; Bernardi, Luciano

2015-01-01

Controlled slow breathing (at 6/min, a rate frequently adopted during yoga practice) can benefit cardiovascular function, including responses to hypoxia. We tested the neural substrates of cardiorespiratory control in humans during volitional controlled breathing and hypoxic challenge using functional magnetic resonance imaging (fMRI). Twenty healthy volunteers were scanned during paced (slow and normal rate) breathing and during spontaneous breathing of normoxic and hypoxic (13% inspired O2) air. Cardiovascular and respiratory measures were acquired concurrently, including beat-to-beat blood pressure from a subset of participants (N = 7). Slow breathing was associated with increased tidal ventilatory volume. Induced hypoxia raised heart rate and suppressed heart rate variability. Within the brain, slow breathing activated dorsal pons, periaqueductal grey matter, cerebellum, hypothalamus, thalamus and lateral and anterior insular cortices. Blocks of hypoxia activated mid pons, bilateral amygdalae, anterior insular and occipitotemporal cortices. Interaction between slow breathing and hypoxia was expressed in ventral striatal and frontal polar activity. Across conditions, within brainstem, dorsal medullary and pontine activity correlated with tidal volume and inversely with heart rate. Activity in rostroventral medulla correlated with beat-to-beat blood pressure and heart rate variability. Widespread insula and striatal activity tracked decreases in heart rate, while subregions of insular cortex correlated with momentary increases in tidal volume. Our findings define slow breathing effects on central and cardiovascular responses to hypoxic challenge. They highlight the recruitment of discrete brainstem nuclei to cardiorespiratory control, and the engagement of corticostriatal circuitry in support of physiological responses that accompany breathing regulation during hypoxic challenge. PMID:25973923

No change in the regional distribution of tidal volume during lateral posture in mechanically ventilated patients assessed by electrical impedance tomography.

PubMed

Bein, Thomas; Ploner, Franz; Ritzka, Markus; Pfeifer, Michael; Schlitt, Hans J; Graf, Bernhard M

2010-07-01

We assessed the distribution of regional lung ventilation during moderate and steep lateral posture using electrical impedance tomography (EIT) in mechanically ventilated patients. Seven patients were placed on a kinetic treatment table. An elastic belt containing 16 electrodes was placed around the chest and was connected to the EIT device. Patients were moved to left and right lateral positions in a stepwise (10 degrees ) mode up to 60 degrees. EIT images [arbitrary units (AU)] were generated and scanned for assessment of relative ventilation distribution changes [tidal volume (V(T))]. A calibration procedure of arbitrary units (AUs) versus ventilator-derived V(T) performed in all patients during three predefined positions (supine, 60 degrees-left dependent and 60 degrees-right-dependent) showed a significant correlation between V(T) in supine, left and right lateral positions with the corresponding AUs (r(2) = 0.356, P<0.05). Changes in V(T) were calculated and compared to supine position, and specific regions of interest (ROIs) were analysed. In our study, in contrast to recent findings, a change in lateral positions did not induce a significant change in regional tidal volume distribution. In right lateral positions, a broader variation of V(T) with a trend towards an increase in the dependently positioned lung was observed in comparison with supine. Lateral positioning promotes the redistribution of ventilation to the ventral regions of the lung. The use of EIT technology might become a helpful tool for understanding and guiding posture therapy in mechanically ventilated patients.

No change in the regional distribution of tidal volume during lateral posture in mechanically ventilated patients assessed by electrical impedance tomography

PubMed Central

Bein, Thomas; Ploner, Franz; Ritzka, Markus; Pfeifer, Michael; Schlitt, Hans J; Graf, Bernhard M

2010-01-01

We assessed the distribution of regional lung ventilation during moderate and steep lateral posture using electrical impedance tomography (EIT) in mechanically ventilated patients. Seven patients were placed on a kinetic treatment table. An elastic belt containing 16 electrodes was placed around the chest and was connected to the EIT device. Patients were moved to left and right lateral positions in a stepwise (10°) mode up to 60°. EIT images [arbitrary units (AU)] were generated and scanned for assessment of relative ventilation distribution changes [tidal volume (VT)]. A calibration procedure of arbitrary units (AUs) versus ventilator-derived VT performed in all patients during three predefined positions (supine, 60°-left dependent and 60°-right-dependent) showed a significant correlation between VT in supine, left and right lateral positions with the corresponding AUs (r2 = 0·356, P<0·05). Changes in VT were calculated and compared to supine position, and specific regions of interest (ROIs) were analysed. In our study, in contrast to recent findings, a change in lateral positions did not induce a significant change in regional tidal volume distribution. In right lateral positions, a broader variation of VT with a trend towards an increase in the dependently positioned lung was observed in comparison with supine. Lateral positioning promotes the redistribution of ventilation to the ventral regions of the lung. The use of EIT technology might become a helpful tool for understanding and guiding posture therapy in mechanically ventilated patients. PMID:20491842

Mechanical Ventilation in Acute Hypoxemic Respiratory Failure: A Review of New Strategies for the Practicing Hospitalist

PubMed Central

Wilson, Jennifer G.; Matthay, Michael A.

2014-01-01

BACKGROUND The goal of mechanical ventilation in acute hypoxemic respiratory failure is to support adequate gas exchange without harming the lungs. How patients are mechanically ventilated can significantly impact their ultimate outcomes. METHODS This review focuses on emerging evidence regarding strategies for mechanical ventilation in patients with acute hypoxemic respiratory failure including: low tidal volume ventilation in the acute respiratory distress syndrome (ARDS), novel ventilator modes as alternatives to low tidal volume ventilation, adjunctive strategies that may enhance recovery in ARDS, the use of lung-protective strategies in patients without ARDS, rescue therapies in refractory hypoxemia, and an evidence-based approach to weaning from mechanical ventilation. RESULTS Once a patient is intubated and mechanically ventilated, low tidal volume ventilation remains the best strategy in ARDS. Adjunctive therapies in ARDS include a conservative fluid management strategy, as well as neuromuscular blockade and prone positioning in moderate-to-severe disease. There is also emerging evidence that a lung-protective strategy may benefit non-ARDS patients. For patients with refractory hypoxemia, extracorporeal membrane oxygenation should be considered. Once the patient demonstrates signs of recovery, the best approach to liberation from mechanical ventilation involves daily spontaneous breathing trials and protocolized assessment of readiness for extubation. CONCLUSIONS Prompt recognition of ARDS and use of lung-protective ventilation, as well as evidence-based adjunctive therapies, remain the cornerstones of caring for patients with acute hypoxemic respiratory failure. In the absence of contraindications, it is reasonable to consider lung-protective ventilation in non-ARDS patients as well, though the evidence supporting this practice is less conclusive. PMID:24733692

Accuracy and consistency of respiratory inductive plethysmography for overnight tidal volume measurement.

PubMed

Zhang, J; Ruch, E W; Bloch, K E

2001-01-01

To validate the accuracy and consistency of respiratory inductive plethysmography (RIP) in measuring tidal volume after an overnight sleep, tidal volumes of 18 patients with suspected sleep-disordered breathing and 8 normal volunteers were measured simultaneously with RIP (VTRIP) and with an ultrasonic airflow meter (VTUFM) before and after an unstrained overnight sleep on supine and lateral decubitus. The bias of the VTRIP was expressed as (VTRIP-VTUFM)/ VTUFM.100%, limits of agreement between VTRIP and VTUFM was measured by averaged bias +/- 2 s. Results showed that in normal subjects, the bias of RIP before and after overnight sleep was precise and consistent in both supine (0.7% and -1.6%) and lateral decubitus (3.7% and -0.56%). In these patients, the bias of RIP before and after sleep in supine also remained small (1.9% and 1.7%), but it became larger in lateral decubitus (24.5% and 20.4%) and 11.5% exceeded the limits of agreement observed in the evening. The patients' body mass indices (BMI) were higher than those of normal subjects (median 34.2 vs. 27.8 kg/m2). Pooled data showed that the bias of VTRIP in the morning on lateral decubitus but not on supine was correlated to BMI (Spearman R = 0.32, n = 52, P = 0.02). Thus, we were led to conclude that the accuracy of VTRIP overnight was precise and consistent in normal subjects, but the deviation of VTRIP measured on lateral decubitus in patients especially in those with excessive obesity was greater, thus, the method should not be used for quantitative determination.

Optimization and Dose Estimation of Aerosol Delivery to Non-Human Primates.

PubMed

MacLoughlin, Ronan J; van Amerongen, Geert; Fink, James B; Janssens, Hettie M; Duprex, W Paul; de Swart, Rik L

2016-06-01

In pre-clinical animal studies, the uniformity of dosing across subjects and routes of administration is a crucial requirement. In preparation for a study in which aerosolized live-attenuated measles virus vaccine was administered to cynomolgus monkeys (Macaca fascicularis) by inhalation, we assessed the percentage of a nebulized dose inhaled under varying conditions. Drug delivery varies with breathing parameters. Therefore we determined macaque breathing patterns (tidal volume, breathing frequency, and inspiratory to expiratory (I:E) ratio) across a range of 3.3-6.5 kg body weight, using a pediatric pneumotachometer interfaced either with an endotracheal tube or a facemask. Subsequently, these breathing patterns were reproduced using a breathing simulator attached to a filter to collect the inhaled dose. Albuterol was nebulized using a vibrating mesh nebulizer and the percentage inhaled dose was determined by extraction of drug from the filter and subsequent quantification. Tidal volumes ranged from 24 to 46 mL, breathing frequencies from 19 to 31 breaths per minute and I:E ratios from 0.7 to 1.6. A small pediatric resuscitation mask was identified as the best fitting interface between animal and pneumotachometer. The average efficiency of inhaled dose delivery was 32.1% (standard deviation 7.5, range 24%-48%), with variation in tidal volumes as the most important determinant. Studies in non-human primates aimed at comparing aerosol delivery with other routes of administration should take both the inter-subject variation and relatively low efficiency of delivery to these low body weight mammals into account.

Field testing of a convergent array of acoustic Doppler profilers for high-resolution velocimetry in energetic tidal currents

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harding, Samuel F.; Sellar, Brian; Richmond, Marshall C.

An array of single-beam acoustic Doppler profilers has been developed for the high resolution measurement of three-dimensional tidal flow velocities and subsequently tested in an energetic tidal site. This configuration has been developed to increase spatial resolution of velocity measurements in comparison to conventional acoustic Doppler profilers (ADPs) which characteristically use divergent acoustic beams emanating from a single instrument. This is achieved using geometrically convergent acoustic beams creating a sample volume at the focal point of 0.03 m3. Away from the focal point, the array is also able to simultaneously reconstruct three-dimensional velocity components in a profile throughout the watermore » column, and is referred to herein as a convergent-beam acoustic Doppler profiler (C-ADP). Mid-depth profiling is achieved through integration of the sensor platform with the operational commercial-scale Alstom 1MW DeepGen-IV Tidal Turbine deployed at the European Marine Energy Center, Orkney Isles, UK. This proof-of-concept paper outlines the C-ADP system configuration and comparison to measurements provided by co-installed reference instrumentation.« less

A radar map of Titan Seas: Tidal dissipation and ocean mixing through the throat of Kraken

NASA Astrophysics Data System (ADS)

Lorenz, Ralph D.; Kirk, Randolph L.; Hayes, Alexander G.; Anderson, Yanhua Z.; Lunine, Jonathan I.; Tokano, Tetsuya; Turtle, Elizabeth P.; Malaska, Michael J.; Soderblom, Jason M.; Lucas, Antoine; Karatekin, Özgür; Wall, Stephen D.

2014-07-01

We present a radar map of the Titan’s seas, with bathymetry estimated as proportional to distance from the nearest shore. This naïve analytic bathymetry, scaled to a recent radar sounding of Ligeia Mare, suggests a total liquid volume of ∼32,000 km3, at the low end of estimates made in 2008 when mapping coverage was incomplete. We note that Kraken Mare has two principal basins, separated by a narrow (∼17 km wide, ∼40 km long) strait we refer to as the ‘throat’. Tidal currents in this strait may be dramatic (∼0.5 m/s), generating observable effects such as dynamic topography, whirlpools, and acoustic noise, much like tidal races on Earth such as the Corryvreckan off Scotland. If tidal flow through this strait is the dominant mixing process, the two basins take ∼20 Earth years to exchange their liquid inventory. Thus compositional differences over seasonal timescales may exist, but the composition of solutes (and thus evaporites) over Croll-Milankovich timescales should be homogenized.

Mild hypothermia attenuates changes in respiratory system mechanics and modifies cytokine concentration in bronchoalveolar lavage fluid during low lung volume ventilation.

PubMed

Dostál, P; Senkeřík, M; Pařízková, R; Bareš, D; Zivný, P; Zivná, H; Cerný, V

2010-01-01

Hypothermia was shown to attenuate ventilator-induced lung injury due to large tidal volumes. It is unclear if the protective effect of hypothermia is maintained under less injurious mechanical ventilation in animals without previous lung injury. Tracheostomized rats were randomly allocated to non-ventilated group (group C) or ventilated groups of normothermia (group N) and mild hypothermia (group H). After two hours of mechanical ventilation with inspiratory fraction of oxygen 1.0, respiratory rate 60 min(-1), tidal volume 10 ml x kg(-1), positive end-expiratory pressure (PEEP) 2 cm H2O or immediately after tracheostomy in non-ventilated animals inspiratory pressures were recorded, rats were sacrificed, pressure-volume (PV) curve of respiratory system constructed, bronchoalveolar lavage (BAL) fluid and aortic blood samples obtained. Group N animals exhibited a higher rise in peak inspiratory pressures in comparison to group H animals. Shift of the PV curve to right, higher total protein and interleukin-6 levels in BAL fluid were observed in normothermia animals in comparison with hypothermia animals and non-ventilated controls. Tumor necrosis factor-alpha was lower in the hypothermia group in comparison with normothermia and non-ventilated groups. Mild hypothermia attenuated changes in respiratory system mechanics and modified cytokine concentration in bronchoalveolar lavage fluid during low lung volume ventilation in animals without previous lung injury.

Effects of tiotropium on lung hyperinflation, dyspnoea and exercise tolerance in COPD.

PubMed

O'Donnell, D E; Flüge, T; Gerken, F; Hamilton, A; Webb, K; Aguilaniu, B; Make, B; Magnussen, H

2004-06-01

The aim of this study was to test the hypothesis that use of tiotropium, a new long-acting anticholinergic bronchodilator, would be associated with sustained reduction in lung hyperinflation and, thereby, would improve exertional dyspnoea and exercise performance in patients with chronic obstructive pulmonary disease. A randomised, double-blind, placebo-controlled, parallel-group study was conducted in 187 patients (forced expiratory volume in one second 44 +/- 13% pred): 96 patients received 18 microg tiotropium and 91 patients received placebo once daily for 42 days. Spirometry, plethysmographic lung volumes, cycle exercise endurance and exertional dyspnoea intensity at 75% of each patient's maximal work capacity were compared. On day 42, the use of tiotropium was associated with the following effects at pre-dose and post-dose measurements as compared to placebo: vital capacity and inspiratory capacity (IC) increased, with inverse decreases in residual volume and functional residual capacity. Tiotropium increased post-dose exercise endurance time by 105 +/- 40 s (21%) as compared to placebo on day 42. At a standardised time near end-exercise (isotime), IC, tidal volume and minute ventilation all increased, whilst dyspnoea decreased by 0.9 +/- 0.3 Borg scale units. In conclusion, the use of tiotropium was associated with sustained reductions of lung hyperinflation at rest and during exercise. Resultant increases in inspiratory capacity permitted greater expansion of tidal volume and contributed to improvements in both exertional dyspnoea and exercise endurance.

The effects of exogenous surfactant administration on ventilation-induced inflammation in mouse models of lung injury.

PubMed

Puntorieri, Valeria; Hiansen, Josh Qua; McCaig, Lynda A; Yao, Li-Juan; Veldhuizen, Ruud A W; Lewis, James F

2013-11-20

Mechanical ventilation (MV) is an essential supportive therapy for acute lung injury (ALI); however it can also contribute to systemic inflammation. Since pulmonary surfactant has anti-inflammatory properties, the aim of the study was to investigate the effect of exogenous surfactant administration on ventilation-induced systemic inflammation. Mice were randomized to receive an intra-tracheal instillation of a natural exogenous surfactant preparation (bLES, 50 mg/kg) or no treatment as a control. MV was then performed using the isolated and perfused mouse lung (IPML) set up. This model allowed for lung perfusion during MV. In experiment 1, mice were exposed to mechanical ventilation only (tidal volume =20 mL/kg, 2 hours). In experiment 2, hydrochloric acid or air was instilled intra-tracheally four hours before applying exogenous surfactant and ventilation (tidal volume =5 mL/kg, 2 hours). For both experiments, exogenous surfactant administration led to increased total and functional surfactant in the treated groups compared to the controls. Exogenous surfactant administration in mice exposed to MV only did not affect peak inspiratory pressure (PIP), lung IL-6 levels and the development of perfusate inflammation compared to non-treated controls. Acid injured mice exposed to conventional MV showed elevated PIP, lung IL-6 and protein levels and greater perfusate inflammation compared to air instilled controls. Instillation of exogenous surfactant did not influence the development of lung injury. Moreover, exogenous surfactant was not effective in reducing the concentration of inflammatory cytokines in the perfusate. The data indicates that exogenous surfactant did not mitigate ventilation-induced systemic inflammation in our models. Future studies will focus on altering surfactant composition to improve its immuno-modulating activity.

Adaptive support ventilation may deliver unwanted respiratory rate-tidal volume combinations in patients with acute lung injury ventilated according to an open lung concept.

PubMed

Dongelmans, Dave A; Paulus, Frederique; Veelo, Denise P; Binnekade, Jan M; Vroom, Margreeth B; Schultz, Marcus J

2011-05-01

With adaptive support ventilation, respiratory rate and tidal volume (V(T)) are a function of the Otis least work of breathing formula. We hypothesized that adaptive support ventilation in an open lung ventilator strategy would deliver higher V(T)s to patients with acute lung injury. Patients with acute lung injury were ventilated according to a local guideline advising the use of lower V(T) (6-8 ml/kg predicted body weight), high concentrations of positive end-expiratory pressure, and recruitment maneuvers. Ventilation parameters were recorded when the ventilator was switched to adaptive support ventilation, and after recruitment maneuvers. If V(T) increased more than 8 ml/kg predicted body weight, airway pressure was limited to correct for the rise of V(T). Ten patients with a mean (±SD) Pao(2)/Fio(2) of 171 ± 86 mmHg were included. After a switch from pressure-controlled ventilation to adaptive support ventilation, respiratory rate declined (from 31 ± 5 to 21 ± 6 breaths/min; difference = 10 breaths/min, 95% CI 3-17 breaths/min, P = 0.008) and V(T) increased (from 6.5 ± 0.8 to 9.0 ± 1.6 ml/kg predicted body weight; difference = 2.5 ml, 95% CI 0.4-4.6 ml/kg predicted body weight, P = 0.02). Pressure limitation corrected for the rise of V(T), but minute ventilation declined, forcing the user to switch back to pressure-controlled ventilation. Adaptive support ventilation, compared with pressure-controlled ventilation in an open lung strategy setting, delivers a lower respiratory rate-higher V(T) combination. Pressure limitation does correct for the rise of V(T), but leads to a decline in minute ventilation.

The role of high airway pressure and dynamic strain on ventilator-induced lung injury in a heterogeneous acute lung injury model.

PubMed

Jain, Sumeet V; Kollisch-Singule, Michaela; Satalin, Joshua; Searles, Quinn; Dombert, Luke; Abdel-Razek, Osama; Yepuri, Natesh; Leonard, Antony; Gruessner, Angelika; Andrews, Penny; Fazal, Fabeha; Meng, Qinghe; Wang, Guirong; Gatto, Louis A; Habashi, Nader M; Nieman, Gary F

2017-12-01

Acute respiratory distress syndrome causes a heterogeneous lung injury with normal and acutely injured lung tissue in the same lung. Improperly adjusted mechanical ventilation can exacerbate ARDS causing a secondary ventilator-induced lung injury (VILI). We hypothesized that a peak airway pressure of 40 cmH 2 O (static strain) alone would not cause additional injury in either the normal or acutely injured lung tissue unless combined with high tidal volume (dynamic strain). Pigs were anesthetized, and heterogeneous acute lung injury (ALI) was created by Tween instillation via a bronchoscope to both diaphragmatic lung lobes. Tissue in all other lobes was normal. Airway pressure release ventilation was used to precisely regulate time and pressure at both inspiration and expiration. Animals were separated into two groups: (1) over-distension + high dynamic strain (OD + H DS , n = 6) and (2) over-distension + low dynamic strain (OD + L DS , n = 6). OD was caused by setting the inspiratory pressure at 40 cmH 2 O and dynamic strain was modified by changing the expiratory duration, which varied the tidal volume. Animals were ventilated for 6 h recording hemodynamics, lung function, and inflammatory mediators followed by an extensive necropsy. In normal tissue (N T ), OD + L DS caused minimal histologic damage and a significant reduction in BALF total protein (p < 0.05) and MMP-9 activity (p < 0.05), as compared with OD + H DS . In acutely injured tissue (ALI T ), OD + L DS resulted in reduced histologic injury and pulmonary edema (p < 0.05), as compared with OD + H DS . Both N T and ALI T are resistant to VILI caused by OD alone, but when combined with a H DS , significant tissue injury develops.

The Modern Integrated Anaesthesia Workstation

PubMed Central

Patil, Vijaya P; Shetmahajan, Madhavi G; Divatia, Jigeeshu V

2013-01-01

Over the years, the conventional anaesthesia machine has evolved into an advanced carestation. The new machines use advanced electronics, software and technology to offer extensive capabilities for ventilation, monitoring, inhaled agent delivery, low-flow anaesthesia and closed-loop anaesthesia. They offer integrated monitoring and recording facilities and seamless integration with anaesthesia information systems. It is possible to deliver tidal volumes accurately and eliminate several hazards associated with the low pressure system and oxygen flush. Appropriate use can result in enhanced safety and ergonomy of anaesthetic delivery and monitoring. However, these workstations have brought in a new set of limitations and potential drawbacks. There are differences in technology and operational principles amongst the new workstations. Understand the principles of operation of these workstations and have a thorough knowledge of the operating manual of the individual machines. PMID:24249877

Use of a single ventilator to support 4 patients: laboratory evaluation of a limited concept.

PubMed

Branson, Richard D; Blakeman, Thomas C; Robinson, Bryce Rh; Johannigman, Jay A

2012-03-01

A mass-casualty respiratory failure event where patients exceed available ventilators has spurred several proposed solutions. One proposal is use of a single ventilator to support 4 patients. A ventilator was modified to allow attachment of 4 circuits. Each circuit was connected to one chamber of 2 dual-chambered, test lungs. The ventilator was set at a tidal volume (V(T)) of 2.0 L, respiratory frequency of 10 breaths/min, and PEEP of 5 cm H(2)O. Tests were repeated with pressure targeted breaths at 15 cm H(2)O. Airway pressure, volume, and flow were measured at each chamber. The test lungs were set to simulate 4 patients using combinations of resistance (R) and compliance (C). These included equivalent C and R, constant R and variable C, constant C and variable R, and variable C and variable R. When R and C were equivalent the V(T) distributed to each chamber of the test lung was similar during both volume (range 428-442 mL) and pressure (range 528-544 mL) breaths. Changing C while R was constant resulted in large variations in delivered V(T) (volume range 257-621 mL, pressure range 320-762 mL). Changing R while C was constant resulted in a smaller variation in V(T) (volume range 418-460 mL, pressure range 502-554 mL) compared to only C changes. When R and C were both varied, the range of delivered V(T) in both volume (336-517 mL) and pressure (417-676 mL) breaths was greater, compared to only R changes. Using a single ventilator to support 4 patients is an attractive concept; however, the V(T) cannot be controlled for each subject and V(T) disparity is proportional to the variability in compliance. Along with other practical limitations, these findings cannot support the use of this concept for mass-casualty respiratory failure.

Pathogenetic Significance of Biological Markers of Ventilator-Associated Lung Injury in Experimental and Clinical Studies*

PubMed Central

Frank, James A.; Parsons, Polly E.; Matthay, Michael A.

2009-01-01

For patients with acute lung injury, positive pressure mechanical ventilation is life saving. However, considerable experimental and clinical data have demonstrated that how clinicians set the tidal volume, positive end-expiratory pressure, and plateau airway pressure influences lung injury severity and patient outcomes including mortality. In order to better identify ventilator-associated lung injury (VALI), clinical investigators have sought to measure blood-borne and airspace biological markers of VALI. At the same time, several laboratory-based studies have focused on biological markers of inflammation and organ injury in experimental models in order to clarify the mechanisms of ventilator-induced lung injury (VILI) and VALI. This review summarizes data on biological markers of VALI and VILI from both clinical and experimental studies with an emphasis on markers identified in patients and in the experimental setting. This analysis suggests that measurement of some of these biological markers may be of value in diagnosing VALI and in understanding its pathogenesis. PMID:17167015

Low tidal volume mechanical ventilation against no ventilation during cardiopulmonary bypass heart surgery (MECANO): study protocol for a randomized controlled trial.

PubMed

Nguyen, Lee S; Merzoug, Messaouda; Estagnasie, Philippe; Brusset, Alain; Law Koune, Jean-Dominique; Aubert, Stephane; Waldmann, Thierry; Grinda, Jean-Michel; Gibert, Hadrien; Squara, Pierre

2017-12-02

Postoperative pulmonary complications are a leading cause of morbidity and mortality after cardiac surgery. There are no recommendations on mechanical ventilation associated with cardiopulmonary bypass (CPB) during surgery and anesthesiologists perform either no ventilation (noV) at all during CPB or maintain low tidal volume (LTV) ventilation. Indirect evidence points towards better pulmonary outcomes when LTV is performed but no large-scale prospective trial has yet been published in cardiac surgery. The MECANO trial is a single-center, double-blind, randomized, controlled trial comparing two mechanical ventilation strategies, noV and LTV, during cardiac surgery with CPB. In total, 1500 patients are expected to be included, without any restrictions. They will be randomized between noV and LTV on a 1:1 ratio. The noV group will receive no ventilation during CPB. The LTV group will receive 5 breaths/minute with a tidal volume of 3 mL/kg and positive end-expiratory pressure of 5 cmH2O. The primary endpoint will be a composite of all-cause mortality, early respiratory failure defined as a ratio of partial pressure of oxygen/fraction of inspired oxygen <200 mmHg at 1 hour after arrival in the ICU, heavy oxygenation support (defined as a patient requiring either non-invasive ventilation, mechanical ventilation or high-flow oxygen) at 2 days after arrival in the ICU or ventilator-acquired pneumonia defined by the Center of Disease Control. Lung recruitment maneuvers will be performed in the noV and LTV groups at the end of surgery and at arrival in ICU with an insufflation at +30 cmH20 for 5 seconds. Secondary endpoints are those composing the primary endpoint with the addition of pneumothorax, CPB duration, quantity of postoperative bleeding, red blood cell transfusions, revision surgery requirements, length of stay in the ICU and in the hospital and total hospitalization costs. Patients will be followed until hospital discharge. The MECANO trial is the first of its kind to compare in a double-blind design, a no-ventilation to a low-tidal volume strategy for mechanical ventilation during cardiac surgery with CPB, with a primary composite outcome including death, respiratory failure and postoperative pneumonia. ClinicalTrials.gov, NCT03098524 . Registered on 27 February 2017.

The Effect of Compartmental Asymmetry on the Monitoring of Pulmonary Mechanics and Lung Volumes.

PubMed

Keenan, Joseph C; Cortes-Puentes, Gustavo A; Adams, Alexander B; Dries, David J; Marini, John J

2016-11-01

Esophageal pressure measurement for computation of transpulmonary pressure (P tp ) has begun to be incorporated into clinical use for evaluating forces across the lungs. Gaps exist in our understanding of how esophageal pressure (and therefore P tp ), a value measured at a single site, responds when respiratory system compartments are asymmetrically affected by whole-lung atelectasis or unilateral injury as well as changes in chest wall compliance. We reasoned that P tp would track with aerated volume changes as estimated by functional residual capacity (FRC) and tidal volume. We examined this hypothesis in the setting of asymmetric lungs and changes in intra-abdominal pressure. This study was conducted in the animal laboratory of a university-affiliated hospital. Models of unilateral atelectasis and unilateral and bilateral lung injury exposed to intra-abdominal hypertension (IAH) in 10 deeply sedated mechanically ventilated swine. Atelectasis was created by balloon occlusion of the left main bronchus. Unilateral lung injury was induced by saline lavage of isolated right lung. Diffuse lung injury was induced by saline lavage of both lungs. The peritoneum was insufflated with air to create a model of pressure-regulated IAH. We measured esophageal pressures, airway pressures, FRC by gas dilution, and oxygenation. FRC was reduced by IAH in normal lungs (P < .001) and both asymmetric lung pathologies (P < .001). P tp at end-expiration was decreased by IAH in bilateral (P = .001) and unilateral lung injury (P = .003) as well as unilateral atelectasis (P = .019). In the setting of both lung injury models, end-expiratory P tp showed a moderate correlation in tracking with FRC. P tp tracks with aerated lung volume in the setting of thoracic asymmetry and changes in intra-abdominal pressure. However, used alone, it cannot distinguish the relative contributions of air-space distention and recruitment of lung units. Copyright © 2016 by Daedalus Enterprises.

Mechanical Ventilation and Bronchopulmonary Dysplasia.

PubMed

Keszler, Martin; Sant'Anna, Guilherme

2015-12-01

Mechanical ventilation is an important potentially modifiable risk factor for the development of bronchopulmonary dysplasia. Effective use of noninvasive respiratory support reduces the risk of lung injury. Lung volume recruitment and avoidance of excessive tidal volume are key elements of lung-protective ventilation strategies. Avoidance of oxidative stress, less invasive methods of surfactant administration, and high-frequency ventilation are also important factors in lung injury prevention. Copyright © 2015 Elsevier Inc. All rights reserved.

Work of breathing during lung-protective ventilation in patients with acute lung injury and acute respiratory distress syndrome: a comparison between volume and pressure-regulated breathing modes.

PubMed

Kallet, Richard H; Campbell, Andre R; Dicker, Rochelle A; Katz, Jeffrey A; Mackersie, Robert C

2005-12-01

Pressure-control ventilation (PCV) and pressure-regulated volume-control (PRVC) ventilation are used during lung-protective ventilation because the high, variable, peak inspiratory flow rate (V (I)) may reduce patient work of breathing (WOB) more than the fixed V (I) of volume-control ventilation (VCV). Patient-triggered breaths during PCV and PRVC may result in excessive tidal volume (V(T)) delivery unless the inspiratory pressure is reduced, which in turn may decrease the peak V (I). We tested whether PCV and PRVC reduce WOB better than VCV with a high, fixed peak V (I) (75 L/min) while also maintaining a low V(T) target. Fourteen nonconsecutive patients with acute lung injury or acute respiratory distress syndrome were studied prospectively, using a random presentation of ventilator modes in a crossover, repeated-measures design. A target V(T) of 6.4 + 0.5 mL/kg was set during VCV and PRVC. During PCV the inspiratory pressure was set to achieve the same V(T). WOB and other variables were measured with a pulmonary mechanics monitor (Bicore CP-100). There was a nonsignificant trend toward higher WOB (in J/L) during PCV (1.27 + 0.58 J/L) and PRVC (1.35 + 0.60 J/L), compared to VCV (1.09 + 0.59 J/L). While mean V(T) was not statistically different between modes, in 40% of patients, V(T) markedly exceeded the lung-protective ventilation target during PRVC and PCV. During lung-protective ventilation, PCV and PRVC offer no advantage in reducing WOB, compared to VCV with a high flow rate, and in some patients did not allow control of V(T) to be as precise.

Blind Compressed Sensing Enables 3-Dimensional Dynamic Free Breathing Magnetic Resonance Imaging of Lung Volumes and Diaphragm Motion.

PubMed

Bhave, Sampada; Lingala, Sajan Goud; Newell, John D; Nagle, Scott K; Jacob, Mathews

2016-06-01

The objective of this study was to increase the spatial and temporal resolution of dynamic 3-dimensional (3D) magnetic resonance imaging (MRI) of lung volumes and diaphragm motion. To achieve this goal, we evaluate the utility of the proposed blind compressed sensing (BCS) algorithm to recover data from highly undersampled measurements. We evaluated the performance of the BCS scheme to recover dynamic data sets from retrospectively and prospectively undersampled measurements. We also compared its performance against that of view-sharing, the nuclear norm minimization scheme, and the l1 Fourier sparsity regularization scheme. Quantitative experiments were performed on a healthy subject using a fully sampled 2D data set with uniform radial sampling, which was retrospectively undersampled with 16 radial spokes per frame to correspond to an undersampling factor of 8. The images obtained from the 4 reconstruction schemes were compared with the fully sampled data using mean square error and normalized high-frequency error metrics. The schemes were also compared using prospective 3D data acquired on a Siemens 3 T TIM TRIO MRI scanner on 8 healthy subjects during free breathing. Two expert cardiothoracic radiologists (R1 and R2) qualitatively evaluated the reconstructed 3D data sets using a 5-point scale (0-4) on the basis of spatial resolution, temporal resolution, and presence of aliasing artifacts. The BCS scheme gives better reconstructions (mean square error = 0.0232 and normalized high frequency = 0.133) than the other schemes in the 2D retrospective undersampling experiments, producing minimally distorted reconstructions up to an acceleration factor of 8 (16 radial spokes per frame). The prospective 3D experiments show that the BCS scheme provides visually improved reconstructions than the other schemes do. The BCS scheme provides improved qualitative scores over nuclear norm and l1 Fourier sparsity regularization schemes in the temporal blurring and spatial blurring categories. The qualitative scores for aliasing artifacts in the images reconstructed by nuclear norm scheme and BCS scheme are comparable.The comparisons of the tidal volume changes also show that the BCS scheme has less temporal blurring as compared with the nuclear norm minimization scheme and the l1 Fourier sparsity regularization scheme. The minute ventilation estimated by BCS for tidal breathing in supine position (4 L/min) and the measured supine inspiratory capacity (1.5 L) is in good correlation with the literature. The improved performance of BCS can be explained by its ability to efficiently adapt to the data, thus providing a richer representation of the signal. The feasibility of the BCS scheme was demonstrated for dynamic 3D free breathing MRI of lung volumes and diaphragm motion. A temporal resolution of ∼500 milliseconds, spatial resolution of 2.7 × 2.7 × 10 mm, with whole lung coverage (16 slices) was achieved using the BCS scheme.

Novel approach to the exploitation of the tidal energy. Volume 1: Summary and discussion

NASA Astrophysics Data System (ADS)

Gorlov, A. M.

1981-12-01

The hydropneumatic concept in the approach to harnessing low tidal hydropower is discussed. The energy of water flow is converted into the energy of an air jet by a specialized air chamber which is placed on the ocean floor across a flowing watercourse. Water passes through the chamber where it works as a natural piston compressing air in the upper part of the closure. Compressed air is used as a new working plenum to drive air turbines. The kinetic energy of an air jet provided by the air chamber is sufficient for stable operation of industrial air turbines. It is possible to use light plastic barriers instead of conventional rigid dams (the water sail concept). It is confirmed that the concept can result in a less expensive and more effective tidal power plant project than the conventional hydroturbine approach.

The inclusion of ocean-current effects in a tidal-current model as forcing in the convection term and its application to the mesoscale fate of CO2 seeping from the seafloor

NASA Astrophysics Data System (ADS)

Sakaizawa, Ryosuke; Kawai, Takaya; Sato, Toru; Oyama, Hiroyuki; Tsumune, Daisuke; Tsubono, Takaki; Goto, Koichi

2018-03-01

The target seas of tidal-current models are usually semi-closed bays, minimally affected by ocean currents. For these models, tidal currents are simulated in computational domains with a spatial scale of a couple hundred kilometers or less, by setting tidal elevations at their open boundaries. However, when ocean currents cannot be ignored in the sea areas of interest, such as in open seas near coastlines, it is necessary to include ocean-current effects in these tidal-current models. In this study, we developed a numerical method to analyze tidal currents near coasts by incorporating pre-calculated ocean-current velocities. First, a large regional-scale simulation with a spatial scale of several thousand kilometers was conducted and temporal changes in the ocean-current velocity at each grid point were stored. Next, the spatially and temporally interpolated ocean-current velocity was incorporated as forcing into the cross terms of the convection term of a tidal-current model having computational domains with spatial scales of hundreds of kilometers or less. Then, we applied this method to the diffusion of dissolved CO2 in a sea area off Tomakomai, Japan, and compared the numerical results and measurements to validate the proposed method.

Outstanding Universal Values of the Korean Archipelago Getbol: Its potential for World Heritage Nomination

NASA Astrophysics Data System (ADS)

Woo, K. S.; Chun, S. S.; Moon, K. O.

2017-12-01

The `Korean Archipelago Getbol (KAG; Getbol means tidal flat deposits in Korean)' has developed due to the decreasing accommodation space during the Holocene sea-level rise on the broad epicontinental shelf of the southeastern part of the Yellow Sea. Sedimentation and evolution show a variety of quite distinctive tidal flat patterns with intertidal and subtidal drainage systems depending upon the location and orientation of rocky shores. The following KAG`s Outstanding Universal Values are suggested to support the WH: 1) It is the unique coastal sedimentary environment formed by special geological and oceanographic setting in the world. It is the only place in the world where tide-controlled sedimentation processes have produced special tidal flats surrounding numerous rocky islands on a broad epicontinental shelf near convergent tectonic boundary. Macrotidal currents combined with waves and typhoons in this semi-closed oceanographic setting have provided unique geological and oceanographic conditions for their formation. 2) It diplays the most dynamic and complicated, but stable coastal depositional system in the world. Even though the property has been constantly influenced by strong microtidal currents combined with East Asian Monsoon climate (winter erosion and summer deposition) with occasional typhoons during summer, Getbol has maintained its stable depositional system and tidal flat sediments have been accumulated for the past 9,000 years. Sufficient supply of suspended load through Geumgang River provides sustainable depositional system within the property. Complicated island-topography also produced the most complicated and divese depositional systems as well as the deepest tidal channels in the world. (3) The KAG shows the thickest tidal flat sediments protected by numerous islands. Aggradation of tidal sediments has caught up with the rapid Holocene sealevel rise and produced the thickest tidal flat sediments in the world. As a results, numerous former islands of relatively elevated areas have been vanished and hidden. In addition, the KAG shows a complete story of geological, ecological and conservational integrity (the wholeness and intactness). Thus, we strongly believe that the KAG has great potential to be inscribed on a World Heritage List for the criterion (viii).

A Conceptual Framework and Classification for the Fluvial-Backwater-Marine Transition in Coastal Rivers Globally

NASA Astrophysics Data System (ADS)

Howes, N. C.; Georgiou, I. Y.; Hughes, Z. J.; Wolinsky, M. A.

2012-12-01

Channels in fluvio-deltaic and coastal plain settings undergo a progressive series of downstream transitions in hydrodynamics and sediment transport, which is consequently reflected in their morphology and stratigraphic architecture. Conditions progress from uniform fluvial flow to backwater conditions with non-uniform flow, and finally to bi-directional tidal flow or estuarine circulation at the ocean boundary. While significant attention has been given to geomorphic scaling relationships in purely fluvial settings, there have been far fewer studies on the backwater and tidal reaches, and no systematic comparisons. Our study addresses these gaps by analyzing geometric scaling relationships independently in each of the above hydrodynamic regimes and establishes a comparison. To accomplish this goal we have constructed a database of planform geometries including more than 150 channels. In terms of hydrodynamics studies, much of the work on backwater dynamics has concentrated on the Mississippi River, which has very limited tidal influence. We will extend this analysis to include systems with appreciable offshore tidal range, using a numerical hydrodynamic model to study the interaction between backwater dynamics and tides. The database is comprised of systems with a wide range of tectonic, climatic, and oceanic forcings. The scale of these systems, as measured by bankfull width, ranges over three orders of magnitude from the Amazon River in Brazil to the Palix River in Washington. Channel centerlines are extracted from processed imagery, enabling continuous planform measurements of bankfull width, meander wavelength, and sinuosity. Digital terrain and surface models are used to estimate floodplain slopes. Downstream tidal boundary conditions are obtained from the TOPEX 7.1 global tidal model, while upstream boundary conditions such as basin area, relief, and discharge are obtained by linking the databases of Milliman and Meade (2011) and Syvitski (2005). Backwater and tidal length-scales are computed from published data as well as from numerical simulations. An analysis of the database combined with numerical hydrodynamic simulations allows us to organize the results into a process-based classification of coastal rivers. The classification describes the scale, shape, and flow field transitions of coastal rivers as a function of discharge, floodplain slope, and offshore tidal range.

Offshore sand resources for coastal erosion control in Louisiana

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramsey, K.E.; Penland, S.; McBride, R.A.

1990-09-01

An inventory of existing geophysical data supplemented by more than 15,000 km of high-resolution seismic profiles and 400 vibracores collected cooperatively by the Louisiana Geological Survey and US Geological Survey since 1981 indicates that a wide range of aggregate minerals occurs on the continental shelf in a variety of depositional settings. The distribution of these deposits is controlled by the geometry of the preexisting fluvial and deltaic channel systems and the stratigraphic signature of the Holocene Transgression across these features. The geology of coastal and offshore Louisiana is tied to the depositional history of the Mississippi River. Offshore of themore » delta plain, five types of aggregate sources can be identified: inner shelf shoals, submerged barrier islands, tidal inlets, distributary channels, and barrier platforms. This paper describes the geology of offshore Louisiana, the available geophysical data sets, and the distribution of aggregate mineral resources. On the continental shelf of the Mississippi River delta plain, two extensive seismic survey grids have been developed by the Louisiana Geological Survey and US Geological Survey. The most prospective resources found are the huge sand bodies of Ship Shoal and associated distributaries, Cat Island Pass tidal channels and associated tidal deltas, and Barataria Pass/Grand Terre tidal channels and associated tidal deltas. East of the mouth of the Mississippi River are the Chandeleur Islands, where LGS identified seven major sand resource targets, truncated barrier-spit and tidal inlet deposits, submerged beach ridges, and distributaries associated with abandoned St. Bernard delta complexes. Abundant sand resources can be found in offshore Louisiana. Many of the sand bodies contain heavy minerals, but their concentration and distribution is unknown. Other potential sand resources not yet adequately explored include Sabine Bank, the Outer Shoal, and the St. Bernard shoal.« less

Shore erosion as a sediment source to the tidal Potomac River, Maryland and Virginia

USGS Publications Warehouse

Miller, Andrew J.

1987-01-01

The shoreline of the tidal Potomac River attained its present form as a result of the Holocene episode of sea-level rise; the drowned margins of the system are modified by wave activity in the shore zone and by slope processes on banks steepened by basal-wave erosion. Shore erosion leaves residual sand and gravel in shallow water and transports silt and clay offshore to form a measurable component of the suspended-sediment load of the tidal Potomac River. Erosion rates were measured by comparing digitized historical shoreline maps and modern maps, and by comparing stereopairs of aerial photographs taken at different points in time, with the aid of an interactive computer-graphics system and a digitizing stereoplotter. Cartographic comparisons encompassed 90 percent of the study reach and spanned periods of 38 to 109 years, with most measurements spanning at least 84 years. Photogrammetric comparisons encompassed 49 percent of the study reach and spanned 16 to 40 years. Field monitoring of erosion rates and processes at two sites, Swan Point Neck, Maryland, and Mason Neck, Virginia, spanned periods of 10 to 18 months. Estimated average recession rates of shoreline in the estuary, based on cartographic and photogrammetric measurements, were 0.42 to 0.52 meter per annum (Virginia shore) and 0.31 to 0.41 meter per annum (Maryland shore). Average recession rates of shoreline in the tidal river and transition zone were close to 0.15 meter per annum. Estimated average volume-erosion rates along the estuary were 1.20 to 1.87 cubic meters per meter of shoreline per annum (Virginia shore) and 0.56 to 0.73 cubic meter per meter of shoreline per annum (Maryland shore); estimated average volume-erosion rates along the shores of the tidal river and transition zone were 0.55 to 0.74 cubic meter per meter of shoreline per annum. Estimated total sediment contributed to the tidal Potomac River by shore erosion was 0.375 x 10 6 to 0.565 x 10 6 metric tons per annum; of this, the estimated amount of silt and clay ranged from 0.153x10 6 to 0.226x10 6 metric tons per annum. Between 49 and 60 percent of the sediment was derived from the Virginia shore of the estuary; 14 to 18 percent was derived from the Maryland shore of the estuary; and 23 to 36 percent was derived from the shores of the tidal river and transition zone. The adjusted modern estimate of sediment eroded from the shoreline of the estuary is about 55 percent of the historical estimate. Sediment eroded from the shoreline accounted for about 6 to 9 percent of the estimated total suspended load for the tidal Potomac River during water years 1979 through 1981 and for about 11 to 18 percent of the suspended load delivered to the estuary during the same period. Annual suspended-sediment loads derived from upland source areas fluctuated by about an order of magnitude during the 3 years of record (1979-81); shore erosion may have been a more important component of the sediment budget during periods of low flow than during periods of higher discharges. Prior to massive land clearance during the historical period of intensive agriculture in the 18th and 19th centuries, annual sediment loads from upland sources probably were smaller than they are at present; under these circumstances shore erosion would have been an important component of the sediment budget. At current rates of sediment supply, relative sea-level rise, and shoreline recession, the landward parts of the tidal Potomac River are rapidly being filled by sediment. If these rates were to remain constant over time, and no sediment were to escape into Chesapeake Bay, the tidal river and transition zone would be filled within 600 years, and the total system would be filled in less than 4,000 years. Given a slower rate of sediment supply, comparable to the measured rate during the low-flow 1981 water year, the volume of the tidal Potomac River might remain relatively stable or even increase over time. Changes in rates

Channel Capture as a Response to Anthropogenic Modification of a Tidal Landscape: Ganges-Brahmaputra-Meghna Delta, Southwest Bangladesh

NASA Astrophysics Data System (ADS)

Wilson, C.; Bain, R. L.; Goodbred, S. L., Jr.; Hale, R. P.

2017-12-01

Studies of tidal channel dynamics frequently emphasize "morphologically short" spatial scales (i.e., settings in which the cross-system tidal propagation time is negligible) or idealized single-channel planforms. In contrast, tides in the Ganges-Brahmaputra-Meghna Delta (GBMD) propagate more than 100 kilometers inland from the coast through a network of interconnected tidal estuaries, producing complex hydrodynamic behavior that remains poorly understood. Intense anthropogenic modification of the GBMD landscape further complicates tidally-driven, natural delta surface maintenance. Analyzing this system is particularly urgent given the current trend of rising sea level and its associated impacts on coastal communities.We present results from an ongoing field investigation of tidal waveform interaction and mass exchange between the Pussur and Shibsa Rivers, two large macrotidal estuaries in the southwestern GBMD. In the 1960s, construction of earthen embankments ("polders") eliminated regular tidal inundation for a vast region of the tidal platform, shrinking the Shibsa and Pussur basins by an estimated 1000 km2 and 700 km2, respectively. Conservation of mass predicts that a reduction in tidal basin area will decrease peak flow velocities and induce channel siltation; indeed, 100 km2 of secondary channels at the distal end of the tidal range have partly or fully closed in recent decades. The Pussur is likewise rapidly shoaling, restricting navigational access along a major shipping route. However, discharge and bathymetric datasets indicate that the adjacent Shibsa conveys three to four times more water than the Pussur and is actively scouring its bed, contrary to its predicted response to polder construction. Our field measurements are consistent with an ongoing channel capture event in which the Shibsa floods and drains a progressively greater portion of the former Pussur basin, allowing the Shibsa to widen and deepen despite the regional trend of channel abandonment. These observations suggest that natural or anthropogenic changes to a tidal basin can drive rapid morphological adjustment of these typically-stable tidal channel systems.

Early pictures of global climate change impact to the coastal area (North West of Demak Central Java Indonesia)

NASA Astrophysics Data System (ADS)

Andreas, Heri; Pradipta, Dhota; Abidin, Hasanuddin Z.; Sarsito, Dina A.

2017-07-01

In the last several decades we have been realized for the Global Climate Change situation. Some indicators are worldwide increasing temperature, decreasing volume of ice in Antarctica, and the sea level rise. Relating to the decreased of ice volume and the sea level rise, this situation has been predicted to endanger the living at the coastal area in the future. Prediction models have shown some coastal cities area would suffer flood by tidal inundation and even permanent flooding. Coincidently, today in the North West of Demak District Central Java Indonesia we literally can see the early picture of Global Climate Change impact to the coastal areas as mention. The occurrence of tidal inundation in this area was recognized at least in the early 2000 and even earlier, and in the recent years the tidal inundation comes not only at a high tide but even at the regular tide, and in fact some of this area are obviously sinking to the sea through times. This early picture is truly showing a disaster. Adaptation has been made in facing the disaster such as increasing the house and infrastructures, and built dyke. We have been done some investigations to this area by field observations (mapping the flooded area, interviewing people and seeing the adaptations, conduct GPS measurement to see deformation, etc.), gather information from digital media and also using remotely time series of high resolution satellite image data to mapping the tidal inundation in this area. We noted people increased their house and the local goverment elevated the road and the bridge, etc. regulary over less decade periode. Our conclusions said that the adaptation only made temporaly since the sea level keep rising worsening by the land subsidence significantly.

Tidal volume single breath washout of two tracer gases--a practical and promising lung function test.

PubMed

Singer, Florian; Stern, Georgette; Thamrin, Cindy; Fuchs, Oliver; Riedel, Thomas; Gustafsson, Per; Frey, Urs; Latzin, Philipp

2011-03-10

Small airway disease frequently occurs in chronic lung diseases and may cause ventilation inhomogeneity (VI), which can be assessed by washout tests of inert tracer gas. Using two tracer gases with unequal molar mass (MM) and diffusivity increases specificity for VI in different lung zones. Currently washout tests are underutilised due to the time and effort required for measurements. The aim of this study was to develop and validate a simple technique for a new tidal single breath washout test (SBW) of sulfur hexafluoride (SF(6)) and helium (He) using an ultrasonic flowmeter (USFM). The tracer gas mixture contained 5% SF(6) and 26.3% He, had similar total MM as air, and was applied for a single tidal breath in 13 healthy adults. The USFM measured MM, which was then plotted against expired volume. USFM and mass spectrometer signals were compared in six subjects performing three SBW. Repeatability and reproducibility of SBW, i.e., area under the MM curve (AUC), were determined in seven subjects performing three SBW 24 hours apart. USFM reliably measured MM during all SBW tests (n = 60). MM from USFM reflected SF(6) and He washout patterns measured by mass spectrometer. USFM signals were highly associated with mass spectrometer signals, e.g., for MM, linear regression r-squared was 0.98. Intra-subject coefficient of variation of AUC was 6.8%, and coefficient of repeatability was 11.8%. The USFM accurately measured relative changes in SF(6) and He washout. SBW tests were repeatable and reproducible in healthy adults. We have developed a fast, reliable, and straightforward USFM based SBW method, which provides valid information on SF(6) and He washout patterns during tidal breathing.

Tidal Volume Single Breath Washout of Two Tracer Gases - A Practical and Promising Lung Function Test

PubMed Central

Singer, Florian; Stern, Georgette; Thamrin, Cindy; Fuchs, Oliver; Riedel, Thomas; Gustafsson, Per; Frey, Urs; Latzin, Philipp

2011-01-01

Background Small airway disease frequently occurs in chronic lung diseases and may cause ventilation inhomogeneity (VI), which can be assessed by washout tests of inert tracer gas. Using two tracer gases with unequal molar mass (MM) and diffusivity increases specificity for VI in different lung zones. Currently washout tests are underutilised due to the time and effort required for measurements. The aim of this study was to develop and validate a simple technique for a new tidal single breath washout test (SBW) of sulfur hexafluoride (SF6) and helium (He) using an ultrasonic flowmeter (USFM). Methods The tracer gas mixture contained 5% SF6 and 26.3% He, had similar total MM as air, and was applied for a single tidal breath in 13 healthy adults. The USFM measured MM, which was then plotted against expired volume. USFM and mass spectrometer signals were compared in six subjects performing three SBW. Repeatability and reproducibility of SBW, i.e., area under the MM curve (AUC), were determined in seven subjects performing three SBW 24 hours apart. Results USFM reliably measured MM during all SBW tests (n = 60). MM from USFM reflected SF6 and He washout patterns measured by mass spectrometer. USFM signals were highly associated with mass spectrometer signals, e.g., for MM, linear regression r-squared was 0.98. Intra-subject coefficient of variation of AUC was 6.8%, and coefficient of repeatability was 11.8%. Conclusion The USFM accurately measured relative changes in SF6 and He washout. SBW tests were repeatable and reproducible in healthy adults. We have developed a fast, reliable, and straightforward USFM based SBW method, which provides valid information on SF6 and He washout patterns during tidal breathing. PMID:21423739

Tidal river dynamics: Implications for deltas

NASA Astrophysics Data System (ADS)

Hoitink, A. J. F.; Jay, D. A.

2016-03-01

Tidal rivers are a vital and little studied nexus between physical oceanography and hydrology. It is only in the last few decades that substantial research efforts have been focused on the interactions of river discharge with tidal waves and storm surges into regions beyond the limit of salinity intrusion, a realm that can extend inland hundreds of kilometers. One key phenomenon resulting from this interaction is the emergence of large fortnightly tides, which are forced long waves with amplitudes that may increase beyond the point where astronomical tides have become extinct. These can be larger than the linear tide itself at more landward locations, and they greatly influence tidal river water levels and wetland inundation. Exploration of the spectral redistribution and attenuation of tidal energy in rivers has led to new appreciation of a wide range of consequences for fluvial and coastal sedimentology, delta evolution, wetland conservation, and salinity intrusion under the influence of sea level rise and delta subsidence. Modern research aims at unifying traditional harmonic tidal analysis, nonparametric regression techniques, and the existing understanding of tidal hydrodynamics to better predict and model tidal river dynamics both in single-thread channels and in branching channel networks. In this context, this review summarizes results from field observations and modeling studies set in tidal river environments as diverse as the Amazon in Brazil, the Columbia, Fraser and Saint Lawrence in North America, the Yangtze and Pearl in China, and the Berau and Mahakam in Indonesia. A description of state-of-the-art methods for a comprehensive analysis of water levels, wave propagation, discharges, and inundation extent in tidal rivers is provided. Implications for lowland river deltas are also discussed in terms of sedimentary deposits, channel bifurcation, avulsion, and salinity intrusion, addressing contemporary research challenges.

The physiological basis and clinical significance of lung volume measurements.

PubMed

Lutfi, Mohamed Faisal

2017-01-01

From a physiological standpoint, the lung volumes are either dynamic or static. Both subclasses are measured at different degrees of inspiration or expiration; however, dynamic lung volumes are characteristically dependent on the rate of air flow. The static lung volumes/capacities are further subdivided into four standard volumes (tidal, inspiratory reserve, expiratory reserve, and residual volumes) and four standard capacities (inspiratory, functional residual, vital and total lung capacities). The dynamic lung volumes are mostly derived from vital capacity. While dynamic lung volumes are essential for diagnosis and follow up of obstructive lung diseases, static lung volumes are equally important for evaluation of obstructive as well as restrictive ventilatory defects. This review intends to update the reader with the physiological basis, clinical significance and interpretative approaches of the standard static lung volumes and capacities.

Increasing compliance with low tidal volume ventilation in the ICU with two nudge-based interventions: evaluation through intervention time-series analyses.

PubMed

Bourdeaux, Christopher P; Thomas, Matthew Jc; Gould, Timothy H; Malhotra, Gaurav; Jarvstad, Andreas; Jones, Timothy; Gilchrist, Iain D

2016-05-26

Low tidal volume (TVe) ventilation improves outcomes for ventilated patients, and the majority of clinicians state they implement it. Unfortunately, most patients never receive low TVes. 'Nudges' influence decision-making with subtle cognitive mechanisms and are effective in many contexts. There have been few studies examining their impact on clinical decision-making. We investigated the impact of 2 interventions designed using principles from behavioural science on the deployment of low TVe ventilation in the intensive care unit (ICU). University Hospitals Bristol, a tertiary, mixed medical and surgical ICU with 20 beds, admitting over 1300 patients per year. Data were collected from 2144 consecutive patients receiving controlled mechanical ventilation for more than 1 hour between October 2010 and September 2014. Patients on controlled mechanical ventilation for more than 20 hours were included in the final analysis. (1) Default ventilator settings were adjusted to comply with low TVe targets from the initiation of ventilation unless actively changed by a clinician. (2) A large dashboard was deployed displaying TVes in the format mL/kg ideal body weight (IBW) with alerts when TVes were excessive. TVe in mL/kg IBW. TVe was significantly lower in the defaults group. In the dashboard intervention, TVe fell more quickly and by a greater amount after a TVe of 8 mL/kg IBW was breached when compared with controls. This effect improved in each subsequent year for 3 years. This study has demonstrated that adjustment of default ventilator settings and a dashboard with alerts for excessive TVe can significantly influence clinical decision-making. This offers a promising strategy to improve compliance with low TVe ventilation, and suggests that using insights from behavioural science has potential to improve the translation of evidence into practice. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

The respiration pattern as an indicator of the anaerobic threshold.

PubMed

Mirmohamadsadeghi, Leila; Vesin, Jean-Marc; Lemay, Mathieu; Deriaz, Olivier

2015-08-01

The anaerobic threshold (AT) is a good index of personal endurance but needs a laboratory setting to be determined. It is important to develop easy AT field measurements techniques in order to rapidly adapt training programs. In the present study, it is postulated that the variability of the respiratory parameters decreases with exercise intensity (especially at the AT level). The aim of this work was to assess, on healthy trained subjects, the putative relationships between the variability of some respiration parameters and the AT. The heart rate and respiratory variables (volume, rate) were measured during an incremental exercise performed on a treadmill by healthy moderately trained subjects. Results show a decrease in the variance of 1/tidal volume with the intensity of exercise. Consequently, the cumulated variance (sum of the variance measured at each level of the exercise) follows an exponential relationship with respect to the intensity to reach eventually a plateau. The amplitude of this plateau is closely related to the AT (r=-0.8). It is concluded that the AT is related to the variability of the respiration.

The ocean response at multiple space and time scales to tidal stream energy extraction by a large-scale turbine array.

NASA Astrophysics Data System (ADS)

De Dominicis, Michela; O'Hara Murray, Rory; Wolf, Judith

2017-04-01

A comprehensive assessment of the tidal energy resource realistically available for electricity generation and the study of the potential environmental impacts associated with its extraction in the Pentland Firth (Scottish Waters, UK) are presented. In order to examine both local (< 100 km) and region-wide (>100 km) spatial scales, the Scottish Shelf Model (SSM), an unstructured grid three-dimensional FVCOM (Finite Volume Community Ocean Model) model implementation has been used, since it covers the entire NW European Shelf, with a high resolution where the tidal stream energy is extracted. A large theoretical array of tidal stream turbines has been designed and implemented in the model using the momentum sink approach, in which a momentum sink term represents the loss of momentum due to tidal energy extraction. The estimate of the maximum available power for electricity generation from the Pentland Firth is 1.64 GW, which requires thousands of turbines to be deployed. This estimate takes into account the tidal stream energy extraction feedbacks on the flow and considers, for the first time, the realistic operation of a generic tidal stream turbine, which is limited to operate in a range of flow velocities due to technological constraints. The ocean response to the extraction of 1.64 GW of energy has been examined by comparing a typical annual cycle of the NW European Shelf hydrodynamics reproduced by the SSM with the same period perturbed by tidal stream energy extraction. The changes were analysed at the temporal scale of a spring-neap tidal cycle and, for the first time, on longer term seasonal timescales. Tidal elevation mainly increases in the vicinity of the tidal farm, while far-field effects show a decrease in the mean spring tidal range of the order of 2 cm along the whole east coast of the UK, possibly counteracting some part of the predicted sea level rise due to climate change. Marine currents, both tidal and residual flows, are also affected. They can slow down due to the turbines action or speed up due to flow diversion processes, on both a local and regional scale. The strongest signal in tidal velocities is an overall reduction, which can in turn decrease the energy of tidal mixing and perturb the seasonal stratification on the NW European Shelf. Although the strength of summer water stratification has been found to slightly increase, the extent of the stratified region does not greatly change, thus suggesting the enhanced biological and pelagic biodiversity hotspots, e.g. tidal mixing front locations, are not displaced. Such large scale tidal stream energy extraction is unlikely to occur in the near future, but such potential changes should be considered when planning future tidal energy exploitation. It is likely that large scale developments around the NW European shelf will interact and could, for example, intensify or weaken the changes predicted here, or even be used as mitigation measures (e.g. coastal defence) for other changes (e.g. climate change).

Spin-orbit coupling and tidal dissipation in hot Jupiter systems

NASA Astrophysics Data System (ADS)

Shabaltas, Natalia Igorevna

Hot Jupiters are giant planets located extremely close to their host stars, with orbital periods less than 5 days. Many aspects of hot Jupiter (HJ) formation remain unclear, but several clues, such as the observed misalignment between their orbital axes and their hosts' spin axes, point to a dynamical origin. In the first portion of this work we explore the stellar spin-orbit dynamics of one such dynamical formation channel, the Lidov-Kozai mechanism. We show that the coupling between the stellar spin and the planet orbit can lead to complex, and sometimes chaotic, behavior of the stellar spin vector. Many features of this behavior arise due to a set of resonances between the stellar spin axis precession timescale and the Lidov-Kozai timescale. Under the assumption that the stellar quadrupole does not induce precession in the planet's orbit, given a system with a set of initial parameters, we show that it is possible to predict whether the system can attain high spin-orbit misalignments. In the second portion of this work, we discuss tidal dissipation in giant planets, another aspect that is crucial to dynamical HJ formation theories. We show that tidal dissipation in the cores of giant planets can be significant, and can help reconcile inconsistencies in the tidal dissipation efficiencies inferred from observations of Jupiter's moons and from high-eccentricity HJ migration theories. Finally, we improve upon existing core tidal dissipation theories by presenting semi-analytical formulae for dissipation in a core surrounded by a polytropic n = 1 envelope.

The investigation of chemical quality of water in tidal rivers

USGS Publications Warehouse

Keighton, Walter B.

1954-01-01

This report has been prepared for the guidance of personnel of the Water Resources Division who are engaged in water-quality investigations of tidal rivers. The study of tidal rivers is beset with many complexities not present in the investigation of non-tidal rivers. The periodic rise and fall of the tide may result in a corresponding periodic change in salinity at a sampling location on the tidal river. When the fresh water discharge is low, saline water may intrude up-river, and any factor changing the relative elevations of the ocean and the mean river level has an effect on the extent of salt-water intrusion. Variations in water composition between samples taken at several locations up or down river, at different depths, or at several locations across the stream are likely to be more pronounced than for similar sets of samples from a non-tidal stream. The nature of these variations and factors responsible for them are discussed, and the need for consideration of them in planning a sampling routine is stressed. The nature and mechanism of ocean-water intrusion in tidal rivers is discussed and sampling procedures for its detection are described. lllustrative examples - mostly from the work of the United States Geological Survey or State agencies - show various methods for correlating and presenting data from quality-of-water surveys of tidal rivers. Each tidal river presents an individual problem which can best be understood from a study of the factors involved. To that end the report is supplemented by an annotated bibliography of selected publications in the field.

REDUCTION IN INSPIRATORY FLOW ATTENUATES IL-8 RELEASE AND MAPK ACTIVATION OF LUNG OVERSTRETCH

EPA Science Inventory

Lung overstretch involves mechanical factors, including large tidal volumes (VT), which induce inflammatory responses. The current authors hypothesised that inspiratory flow contributes to ventilator-induced inflammation. Buffer-perfused rabbit lungs were ventilated for 2 h with ...

A classification of U.S. estuaries based on physical and hydrologic attributes

USGS Publications Warehouse

Engle, V.D.; Kurtz, J.C.; Smith, L.M.; Chancy, C.; Bourgeois, P.

2007-01-01

A classification of U.S. estuaries is presented based on estuarine characteristics that have been identified as important for quantifying stressor-response relationships in coastal systems. Estuaries within a class have similar physical and hydrologic characteristics and would be expected to demonstrate similar biological responses to stressor loads from the adjacent watersheds. Nine classes of estuaries were identified by applying cluster analysis to a database for 138 U.S. estuarine drainage areas. The database included physical measures of estuarine areas, depth and volume, as well as hydrologic parameters (i.e., tide height, tidal prism volume, freshwater inflow rates, salinity, and temperature). The ability of an estuary to dilute or flush pollutants can be estimated using physical and hydrologic properties such as volume, bathymetry, freshwater inflow and tidal exchange rates which influence residence time and affect pollutant loading rates. Thus, physical and hydrologic characteristics can be used to estimate the susceptibility of estuaries to pollutant effects. This classification of estuaries can be used by natural resource managers to describe and inventory coastal systems, understand stressor impacts, predict which systems are most sensitive to stressors, and manage and protect coastal resources. ?? Springer Science+Business Media B.V. 2007.

Ventilatory baroreflex sensitivity in humans is not modulated by chemoreflex activation

PubMed Central

Rivera, Eileen; Clarke, Debbie A.; Baugham, Ila L.; Ocon, Anthony J.; Taneja, Indu; Terilli, Courtney; Medow, Marvin S.

2011-01-01

Increasing arterial blood pressure (AP) decreases ventilation, whereas decreasing AP increases ventilation in experimental animals. To determine whether a “ventilatory baroreflex” exists in humans, we studied 12 healthy subjects aged 18–26 yr. Subjects underwent baroreflex unloading and reloading using intravenous bolus sodium nitroprusside (SNP) followed by phenylephrine (“Oxford maneuver”) during the following “gas conditions:” room air, hypoxia (10% oxygen)-eucapnia, and 30% oxygen-hypercapnia to 55–60 Torr. Mean AP (MAP), heart rate (HR), cardiac output (CO), total peripheral resistance (TPR), expiratory minute ventilation (VE), respiratory rate (RR), and tidal volume were measured. After achieving a stable baseline for gas conditions, we performed the Oxford maneuver. VE increased from 8.8 ± 1.3 l/min in room air to 14.6 ± 0.8 l/min during hypoxia and to 20.1 ± 2.4 l/min during hypercapnia, primarily by increasing tidal volume. VE doubled during SNP. CO increased from 4.9 ± .3 l/min in room air to 6.1 ± .6 l/min during hypoxia and 6.4 ± .4 l/min during hypercapnia with decreased TPR. HR increased for hypoxia and hypercapnia. Sigmoidal ventilatory baroreflex curves of VE versus MAP were prepared for each subject and each gas condition. Averaged curves for a given gas condition were obtained by averaging fits over all subjects. There were no significant differences in the average fitted slopes for different gas conditions, although the operating point varied with gas conditions. We conclude that rapid baroreflex unloading during the Oxford maneuver is a potent ventilatory stimulus in healthy volunteers. Tidal volume is primarily increased. Ventilatory baroreflex sensitivity is unaffected by chemoreflex activation, although the operating point is shifted with hypoxia and hypercapnia. PMID:21317304

Face mask ventilation in edentulous patients: a comparison of mandibular groove and lower lip placement.

PubMed

Racine, Stéphane X; Solis, Audrey; Hamou, Nora Ait; Letoumelin, Philippe; Hepner, David L; Beloucif, Sadek; Baillard, Christophe

2010-05-01

In edentulous patients, it may be difficult to perform face mask ventilation because of inadequate seal with air leaks. Our aim was to ascertain whether the "lower lip" face mask placement, as a new face mask ventilation method, is more effective at reducing air leaks than the standard face mask placement. Forty-nine edentulous patients with inadequate seal and air leak during two-hand positive-pressure ventilation using the ventilator circle system were prospectively evaluated. In the presence of air leaks, defined as a difference of at least 33% between inspired and expired tidal volumes, the mask was placed in a lower lip position by repositioning the caudal end of the mask above the lower lip while maintaining the head in extension. The results are expressed as mean +/- SD or median (25th-75th percentiles). Patient characteristics included age (71 +/- 11 yr) and body mass index (24 +/- 4 kg/m2). By using the standard method, the median inspired and expired tidal volumes were 450 ml (400-500 ml) and 0 ml (0-50 ml), respectively, and the median air leak was 400 ml (365-485 ml). After placing the mask in the lower lip position, the median expired tidal volume increased to 400 ml (380-490), and the median air leak decreased to 10 ml (0-20 ml) (P < 0.001 vs. standard method). The lower lip face mask placement with two hands reduced the air leak by 95% (80-100%). In edentulous patients with inadequate face mask ventilation, the lower lip face mask placement with two hands markedly reduced the air leak and improved ventilation.

Visual attention on a respiratory function monitor during simulated neonatal resuscitation: an eye-tracking study.

PubMed

Katz, Trixie A; Weinberg, Danielle D; Fishman, Claire E; Nadkarni, Vinay; Tremoulet, Patrice; Te Pas, Arjan B; Sarcevic, Aleksandra; Foglia, Elizabeth E

2018-06-14

A respiratory function monitor (RFM) may improve positive pressure ventilation (PPV) technique, but many providers do not use RFM data appropriately during delivery room resuscitation. We sought to use eye-tracking technology to identify RFM parameters that neonatal providers view most commonly during simulated PPV. Mixed methods study. Neonatal providers performed RFM-guided PPV on a neonatal manikin while wearing eye-tracking glasses to quantify visual attention on displayed RFM parameters (ie, exhaled tidal volume, flow, leak). Participants subsequently provided qualitative feedback on the eye-tracking glasses. Level 3 academic neonatal intensive care unit. Twenty neonatal resuscitation providers. Visual attention: overall gaze sample percentage; total gaze duration, visit count and average visit duration for each displayed RFM parameter. Qualitative feedback: willingness to wear eye-tracking glasses during clinical resuscitation. Twenty providers participated in this study. The mean gaze sample captured wa s 93% (SD 4%). Exhaled tidal volume waveform was the RFM parameter with the highest total gaze duration (median 23%, IQR 13-51%), highest visit count (median 5.17 per 10 s, IQR 2.82-6.16) and longest visit duration (median 0.48 s, IQR 0.38-0.81 s). All participants were willing to wear the glasses during clinical resuscitation. Wearable eye-tracking technology is feasible to identify gaze fixation on the RFM display and is well accepted by providers. Neonatal providers look at exhaled tidal volume more than any other RFM parameter. Future applications of eye-tracking technology include use during clinical resuscitation. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Sonographic assessment of changes in diaphragmatic kinetics induced by inspiratory resistive loading.

PubMed

Soilemezi, Eleni; Tsagourias, Matthew; Talias, Michael A; Soteriades, Elpidoforos S; Makrakis, Vasilios; Zakynthinos, Epaminondas; Matamis, Dimitrios

2013-04-01

Diaphragmatic breathing patterns under resistive loading remain poorly documented. To our knowledge, this is the first study assessing diaphragmatic motion under conditions of inspiratory resistive loading with the use of sonography. We assessed diaphragmatic motion during inspiratory resistive loading in 40 healthy volunteers using M-mode sonography. In phase I of the study, sonography was performed during normal quiet breathing without respiratory loading. In phase II, sonography was performed after application of a nose clip and connection of the subjects to a pneumotachograph through a mouth piece. In phase III, the participants were assessed while subjected to inspiratory resistive loading of 50 cm H(2)O/L/s. Compared with baseline, the application of a mouth piece and nose clip induced a significant increase in diaphragmatic excursion (from 1.7 to 2.3 cm, P < 0.001) and a decrease in respiratory rate (from 13.4 to 12.2, P < 0.01). Inspiratory resistive loading induced a further decrease in respiratory rate (from 12.2 to 8.0, P < 0.01) and a decrease in diaphragmatic velocity contraction (from 1.2 to 0.8 cm/s, P < 0.01), and also an increase in tidal volume (from 795 to 904 mL, P < 0.01); diaphragmatic excursion, however, did not change significantly. Inspiratory resistive loading induced significant changes in diaphragmatic contraction pattern, which mainly consisted of decreased velocity of diaphragmatic displacement with no change in diaphragmatic excursion. Tidal volume, increased significantly; the increase in tidal volume, along with the unchanged diaphragmatic excursion, provides sonographic evidence of increased recruitment of extradiaphragmatic muscles under inspiratory resistive loading. © 2013 The Authors. Respirology © 2013 Asian Pacific Society of Respirology.

A description of intraoperative ventilator management in patients with acute lung injury and the use of lung protective ventilation strategies.

PubMed

Blum, James M; Maile, Michael; Park, Pauline K; Morris, Michelle; Jewell, Elizabeth; Dechert, Ronald; Rosenberg, Andrew L

2011-07-01

The incidence of acute lung injury (ALI) in hypoxic patients undergoing surgery is currently unknown. Previous studies have identified lung protective ventilation strategies that are beneficial in the treatment of ALI. The authors sought to determine the incidence and examine the use of lung protective ventilation strategies in patients receiving anesthetics with a known history of ALI. The ventilation parameters that were used in all patients were reviewed, with an average preoperative PaO₂/Fio₂ [corrected] ratio of ≤ 300 between January 1, 2005 and July 1, 2009. This dataset was then merged with a dataset of patients screened for ALI. The median tidal volume, positive end-expiratory pressure, peak inspiratory pressures, fraction inhaled oxygen, oxygen saturation, and tidal volumes were compared between groups. A total of 1,286 patients met criteria for inclusion; 242 had a diagnosis of ALI preoperatively. Comparison of patients with ALI versus those without ALI found statistically yet clinically insignificant differences between the ventilation strategies between the groups in peak inspiratory pressures and positive end-expiratory pressure but no other category. The tidal volumes in cc/kg predicted body weight were approximately 8.7 in both groups. Peak inspiratory pressures were found to be 27.87 cm H₂O on average in the non-ALI group and 29.2 in the ALI group. Similar ventilation strategies are used between patients with ALI and those without ALI. These findings suggest that anesthesiologists are not using lung protective ventilation strategies when ventilating patients with low PaO₂/Fio₂ [corrected] ratios and ALI, and instead are treating hypoxia and ALI with higher concentrations of oxygen and peak pressures.

Noninvasive estimation of pharyngeal airway resistance and compliance in children based on volume-gated dynamic MRI and computational fluid dynamics.

PubMed

Persak, Steven C; Sin, Sanghun; McDonough, Joseph M; Arens, Raanan; Wootton, David M

2011-12-01

Computational fluid dynamics (CFD) analysis was used to model the effect of collapsing airway geometry on internal pressure and velocity in the pharyngeal airway of three sedated children with obstructive sleep apnea syndrome (OSAS) and three control subjects. Model geometry was reconstructed from volume-gated magnetic resonance images during normal tidal breathing at 10 increments of tidal volume through the respiratory cycle. Each geometry was meshed with an unstructured grid and solved using a low-Reynolds number k-ω turbulence model driven by flow data averaged over 12 consecutive breathing cycles. Combining gated imaging with CFD modeling created a dynamic three-dimensional view of airway anatomy and mechanics, including the evolution of airway collapse and flow resistance and estimates of the local effective compliance. The upper airways of subjects with OSAS were generally much more compliant during tidal breathing. Compliance curves (pressure vs. cross-section area), derived for different locations along the airway, quantified local differences along the pharynx and between OSAS subjects. In one subject, the distal oropharynx was more compliant than the nasopharynx (1.028 vs. 0.450 mm(2)/Pa) and had a lower theoretical limiting flow rate, confirming the distal oropharynx as the flow-limiting segment of the airway in this subject. Another subject had a more compliant nasopharynx (0.053 mm(2)/Pa) during inspiration and apparent stiffening of the distal oropharynx (C = 0.0058 mm(2)/Pa), and the theoretical limiting flow rate indicated the nasopharynx as the flow-limiting segment. This new method may help to differentiate anatomical and functional factors in airway collapse.

Effects of Interventions on Survival in Acute Respiratory Distress Syndrome: an Umbrella Review of 159 Published Randomized Trials and 29 Meta-analyses

PubMed Central

Tonelli, Adriano R.; Zein, Joe; Adams, Jacob; Ioannidis, John P.A.

2014-01-01

Purpose Multiple interventions have been tested in acute respiratory distress syndrome (ARDS). We examined the entire agenda of published randomized controlled trials (RCTs) in ARDS that reported on mortality and of respective meta-analyses. Methods We searched PubMed, the Cochrane Library and Web of Knowledge until July 2013. We included RCTs in ARDS published in English. We excluded trials of newborns and children; and those on short-term interventions, ARDS prevention or post-traumatic lung injury. We also reviewed all meta-analyses of RCTs in this field that addressed mortality. Treatment modalities were grouped in five categories: mechanical ventilation strategies and respiratory care, enteral or parenteral therapies, inhaled / intratracheal medications, nutritional support and hemodynamic monitoring. Results We identified 159 published RCTs of which 93 had overall mortality reported (n= 20,671 patients) - 44 trials (14,426 patients) reported mortality as a primary outcome. A statistically significant survival benefit was observed in 8 trials (7 interventions) and two trials reported an adverse effect on survival. Among RTCs with >50 deaths in at least 1 treatment arm (n=21), 2 showed a statistically significant mortality benefit of the intervention (lower tidal volumes and prone positioning), 1 showed a statistically significant mortality benefit only in adjusted analyses (cisatracurium) and 1 (high-frequency oscillatory ventilation) showed a significant detrimental effect. Across 29 meta-analyses, the most consistent evidence was seen for low tidal volumes and prone positioning in severe ARDS. Conclusions There is limited supportive evidence that specific interventions can decrease mortality in ARDS. While low tidal volumes and prone positioning in severe ARDS seem effective, most sporadic findings of interventions suggesting reduced mortality are not corroborated consistently in large-scale evidence including meta-analyses. PMID:24667919

Pumpless extracorporeal interventional lung assist in patients with acute respiratory distress syndrome: a prospective pilot study.

PubMed

Zimmermann, Markus; Bein, Thomas; Arlt, Matthias; Philipp, Alois; Rupprecht, Leopold; Mueller, Thomas; Lubnow, Matthias; Graf, Bernhard M; Schlitt, Hans J

2009-01-01

Pumpless interventional lung assist (iLA) is used in patients with acute respiratory distress syndrome (ARDS) aimed at improving extracorporeal gas exchange with a membrane integrated in a passive arteriovenous shunt. In previous studies, feasibility and safety of the iLA system was demonstrated, but no survival benefit was observed. In the present pilot study we tested the hypothesis that timely initiation of iLA using clear algorithms and an improved cannulation technique will positively influence complication rates and management of lung protective ventilation. iLA was implemented in 51 patients from multiple aetiologies meeting ARDS-criteria (American-European Consensus) for more than 12 hours. Initiation of iLA followed an algorithm for screening, careful evaluation and insertion technique. Patients with cardiac insufficiency or severe peripheral vascular disease were not considered suitable for iLA. Arterial and venous cannulae were inserted using a new strategy (ultrasound evaluation of vessels by an experienced team, using cannulae of reduced diameter). The incidence of complications and the effects on tidal volumes and inspiratory plateau pressures were primary outcome parameters, while oxygenation improvement and carbon dioxide removal capabilities were secondary study parameters. Initiation of iLA resulted in a marked removal in arterial carbon dioxide allowing a rapid reduction in tidal volume (

Tidal Impacts on Oceanographic and Sea-ice Processes in the Southern Ocean

NASA Astrophysics Data System (ADS)

Padman, L.; Muench, R. D.; Howard, S.; Mueller, R.

2008-12-01

We review recent field and modeling results that demonstrate the importance of tides in establishing the oceanographic and sea-ice conditions in the boundary regions of the Southern Ocean. The tidal component dominates the total oceanic kinetic energy throughout much of the circum-Antarctic seas. This domination is especially pronounced over the continental slope and shelf including the sub-ice-shelf cavities. Tides provide most of the energy that forces diapycnal mixing under ice shelves and thereby contributes to basal melting. The resulting Ice Shelf Water is a significant component of the Antarctic Bottom Water (AABW) filling much of the deep global ocean. Tides exert significant divergent forcing on sea ice along glacial ice fronts and coastal regions, contributing to creation and maintenance of the coastal polynyas where much of the High Salinity Shelf Water component of AABW is formed. Additional tidally forced ice divergence along the shelf break and upper slope significantly impacts area-averaged ice growth and upper-ocean salinity. Tidally forced cross- slope advection, and mixing by the benthic stress associated with tidal currents along the shelf break and upper slope, strongly influence the paths, volume fluxes and hydrographic properties of benthic outflows of dense water leaving the continental shelf. These outflows provide primary source waters for the AABW. These results confirm that general ocean circulation and coupled ocean/ice/atmosphere climate models must incorporate the impacts of tides.

Effect of menstrual cycle phase on the ventilatory response to rising body temperature during exercise.

PubMed

Hayashi, Keiji; Kawashima, Takayo; Suzuki, Yuichi

2012-07-01

To examine the effect of menstrual cycle on the ventilatory sensitivity to rising body temperature, ten healthy women exercised for ~60 min on a cycle ergometer at 50% of peak oxygen uptake during the follicular and luteal phases of their cycle. Esophageal temperature, mean skin temperature, mean body temperature, minute ventilation, and tidal volume were all significantly higher at baseline and during exercise in the luteal phase than the follicular phase. On the other hand, end-tidal partial pressure of carbon dioxide was significantly lower during exercise in the luteal phase than the follicular phase. Plotting ventilatory parameters against esophageal temperature revealed there to be no significant menstrual cycle-related differences in the slopes or intercepts of the regression lines, although minute ventilation and tidal volume did significantly differ during exercise with mild hyperthermia. To evaluate the cutaneous vasodilatory response, relative laser-Doppler flowmetry values were plotted against mean body temperature, which revealed that the mean body temperature threshold for cutaneous vasodilation was significantly higher in the luteal phase than the follicular phase, but there were no significant differences in the sensitivity or peak values. These results suggest that the menstrual cycle phase influences the cutaneous vasodilatory response during exercise and the ventilatory response at rest and during exercise with mild hyperthermia, but it does not influence ventilatory responses during exercise with moderate hyperthermia.

Stratification and loading of fecal indicator bacteria (FIB) in a tidally muted urban salt marsh.

PubMed

Johnston, Karina K; Dorsey, John H; Saez, Jose A

2015-03-01

Stratification and loading of fecal indicator bacteria (FIB) were assessed in the main tidal channel of the Ballona Wetlands, an urban salt marsh receiving muted tidal flows, to (1) determine FIB concentration versus loading within the water column at differing tidal flows, (2) identify associations of FIB with other water quality parameters, and (3) compare wetland FIB concentrations to the adjacent estuary. Sampling was conducted four times during spring-tide events; samples were analyzed for FIB and turbidity (NTU) four times over a tidal cycle at pre-allocated depths, depending on the water level. Additional water quality parameters measured included temperature, salinity, oxygen, and pH. Loadings were calculated by integrating the stratified FIB concentrations with water column cross-sectional volumes corresponding to each depth. Enterococci and Escherichia coli were stratified both by concentration and loading, although these variables portrayed different patterns over a tidal cycle. Greatest concentrations occurred in surface to mid-strata levels, during flood tides when contaminated water flowed in from the estuary, and during ebb flows when sediments were suspended. Loading was greatest during flood flows and diminished during low tide periods. FIB concentrations within the estuary often were significantly greater than those within the wetland tide channel, supporting previous studies that the wetlands act as a sink for FIB. For public health water quality monitoring, these results indicate that more accurate estimates of FIB concentrations would be obtained by sampling a number of points within a water column rather than relying only on single surface samples.

Breathing pattern and breathlessness in idiopathic pulmonary fibrosis: An observational study.

PubMed

Olukogbon, Kasope L; Thomas, Paul; Colasanti, Ricardo; Hope-Gill, Ben; Williams, Edgar Mark

2016-02-01

Idiopathic pulmonary fibrosis (IPF) is characterized by progressive decline in lung function and increasing dyspnoea. The aim of this study was to investigate the relationship among IPF, pulmonary function, resting tidal breathing patterns and level of breathlessness. Thirty-one participants with IPF and 17 matched healthy controls underwent lung function testing, followed by a 2-min period of resting tidal breathing. The IPF cohort was stratified according to disease severity, based on their forced vital capacity and diffusion capacity for carbon monoxide. In comparison to the healthy controls, the IPF cohort showed a higher tidal volume, VT , of 0.22 L (P = 0.026) and a raised minute ventilation in the severest IPF group, while no differences in the timing of inspiration or expiration were observed. In the IPF cohort, the ratio of VT to forced vital capacity was around 15% higher. These changes corresponded with an increase in the self-reported sensation of breathlessness. Those with IPF increased their depth of breathing with worsening disease severity, with IPF-induced changes in pulmonary function and breathlessness associated with an altered tidal breathing pattern. © 2015 Asian Pacific Society of Respirology.

Breathing regulation and blood gas homeostasis after near complete lesions of the retrotrapezoid nucleus in adult rats.

PubMed

Souza, George M P R; Kanbar, Roy; Stornetta, Daniel S; Abbott, Stephen B G; Stornetta, Ruth L; Guyenet, Patrice G

2018-04-18

The retrotrapezoid nucleus (RTN) is one of several CNS nuclei that contribute, in various capacities (e.g. CO 2 detection, neuronal modulation) to the central respiratory chemoreflex (CRC). Here we test how important the RTN is to PCO 2 homeostasis and breathing during sleep or wake. RTN Nmb positive neurons were killed with targeted microinjections of substance-P-saporin conjugate in adult rats. Under normoxia, rats with large RTN lesions (92 ± 4 % cell loss) had normal blood pressure (BP) and arterial pH but were hypoxic (-8 mmHg PaO 2 ) and hypercapnic (+10 mmHg PaCO 2 ). In resting conditions, minute-volume (V E ) was normal but breathing frequency (f R ) was elevated and tidal volume (V T ) reduced. Resting O 2 consumption and CO 2 production were normal. The hypercapnic ventilatory reflex in 65% FiO 2 had an inverse exponential relationship with the number of surviving RTN neurons and was decreased by up to 92%. The hypoxic ventilatory reflex (HVR; FiO 2 21-10%) persisted after RTN lesions, hypoxia-induced sighing was normal and hypoxia-induced hypotension reduced. In rats with RTN lesions, breathing was lowest during slow-wave sleep (SWS), especially under hyperoxia, but apneas and sleep-disordered breathing were not observed. In conclusion, near complete RTN destruction in rats virtually eliminates the CRC but HVR persists and sighing and the state-dependence of breathing are unchanged. Under normoxia, RTN lesions cause no change in V E but alveolar ventilation is reduced by at least 21%, probably because of increased physiological dead volume. RTN lesions do not cause sleep apnea during SWS, even under hyperoxia. Background: the retrotrapezoid nucleus (RTN) drives breathing proportionally to brain PCO 2 but its role during various states of vigilance needed clarification. New result: Under normoxia, RTN lesions increase the arterial PCO 2 set-point, lower the PO 2 set-point and reduce alveolar ventilation relative to CO 2 production. Tidal volume is reduced and breathing frequency increased to a comparable degree during wake, slow-wave sleep and REM sleep. RTN lesions do not produce apneas or disordered breathing during sleep. New result: RTN lesions in rats virtually eliminate the central respiratory chemoreflex (CRC) while preserving the cardiorespiratory responses to hypoxia; the relationship between CRC and number of surviving RTN Nmb neurons is an inverse exponential. the CRC does not function without the RTN. In the quasi-complete absence of the RTN and CRC, alveolar ventilation is reduced despite an increased drive to breathe from the carotid bodies. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

4D-CT motion estimation using deformable image registration and 5D respiratory motion modeling.

PubMed

Yang, Deshan; Lu, Wei; Low, Daniel A; Deasy, Joseph O; Hope, Andrew J; El Naqa, Issam

2008-10-01

Four-dimensional computed tomography (4D-CT) imaging technology has been developed for radiation therapy to provide tumor and organ images at the different breathing phases. In this work, a procedure is proposed for estimating and modeling the respiratory motion field from acquired 4D-CT imaging data and predicting tissue motion at the different breathing phases. The 4D-CT image data consist of series of multislice CT volume segments acquired in ciné mode. A modified optical flow deformable image registration algorithm is used to compute the image motion from the CT segments to a common full volume 3D-CT reference. This reference volume is reconstructed using the acquired 4D-CT data at the end-of-exhalation phase. The segments are optimally aligned to the reference volume according to a proposed a priori alignment procedure. The registration is applied using a multigrid approach and a feature-preserving image downsampling maxfilter to achieve better computational speed and higher registration accuracy. The registration accuracy is about 1.1 +/- 0.8 mm for the lung region according to our verification using manually selected landmarks and artificially deformed CT volumes. The estimated motion fields are fitted to two 5D (spatial 3D+tidal volume+airflow rate) motion models: forward model and inverse model. The forward model predicts tissue movements and the inverse model predicts CT density changes as a function of tidal volume and airflow rate. A leave-one-out procedure is used to validate these motion models. The estimated modeling prediction errors are about 0.3 mm for the forward model and 0.4 mm for the inverse model.

Heart rate variability and aerobic fitness.

PubMed

De Meersman, R E

1993-03-01

Heart rate variability, a noninvasive marker of parasympathetic activity, diminishes with aging and is augmented after exercise training. Whether habitual exercise over time can attenuate this loss is unknown. This cross-sectional investigation compared 72 male runners, aged 15 to 83 to 72 age- and weight-matched sedentary control subjects for the amplitude of their heart rate variability. Heart rate variability was assessed during rest while subjects were breathing at a rate of 6 breaths per minute and at an augmented tidal volume (tidal volume = 30% of vital capacity). Fitness levels were assessed with on-line, open-circuit spirometry while subjects were performing an incremental stress test. Overall results between the two groups showed that the physically active group had significantly higher fitness levels (p < 0.001), which were associated with significantly higher levels of heart rate variability, when compared with their sedentary counterparts (p < 0.001). These findings provide suggestive evidence for habitual aerobic exercise as a beneficial modulator of heart rate variability in an aging population.

Intraoperative mechanical ventilation for the pediatric patient.

PubMed

Kneyber, Martin C J

2015-09-01

Invasive mechanical ventilation is required when children undergo general anesthesia for any procedure. It is remarkable that one of the most practiced interventions such as pediatric mechanical ventilation is hardly supported by any scientific evidence but rather based on personal experience and data from adults, especially as ventilation itself is increasingly recognized as a harmful intervention that causes ventilator-induced lung injury. The use of low tidal volume and higher levels of positive end-expiratory pressure became an integral part of lung-protective ventilation following the outcomes of clinical trials in critically ill adults. This approach has been readily adopted in pediatric ventilation. However, a clear association between tidal volume and mortality has not been ascertained in pediatrics. In fact, experimental studies have suggested that young children might be less susceptible to ventilator-induced lung injury. As such, no recommendations on optimal lung-protective ventilation strategy in children with or without lung injury can be made. Copyright © 2015 Elsevier Ltd. All rights reserved.

Cardiorespiratory activity of C-terminal pentapeptide of substance P in anaesthetized rats.

PubMed

Wojciechowski, Piotr; Szereda-Przestaszewska, Małgorzata; Lipkowski, Andrzej Wojciech

2016-11-01

Experiments were performed in anaesthetized, spontaneously breathing rats to: (1) analyse the respiratory and cardiovascular effects of C-terminal fragment of substance P (AWL2077) as referred to those exerted by the parent undecapeptide, (2) determine the involvement of lung vagal afferents to these responses. Each peptide was injected intravenously at a dose of 0.3μmol/kg into neurally intact or midcervically vagotomized rats. Administration of both compounds decreased tidal volume, minute ventilation, mean arterial blood pressure and heart rate, showing stimulatory (SP) and depressive (AWL2077) effects on the rate of breathing. Midcervical vagotomy reversed (post-SP) and precluded (post-AWL2077) respiratory rate responses and eliminated bradycardia evoked by both peptides. These findings indicate that the examined C-terminal pentapeptide was convergent with, but less potent than substance P in central depression of tidal volume and displayed divergence in the peripheral effect on respiratory timing. Copyright © 2016 Elsevier B.V. All rights reserved.

Cross-sectional changes in lung volume measured by electrical impedance tomography are representative for the whole lung in ventilated preterm infants.

PubMed

van der Burg, Pauline S; Miedema, Martijn; de Jongh, Frans H; Frerichs, Inez; van Kaam, Anton H

2014-06-01

Electrical impedance tomography measures lung volume in a cross-sectional slice of the lung. Whether these cross-sectional volume changes are representative of the whole lung has only been investigated in adults, showing conflicting results. This study aimed to compare cross-sectional and whole lung volume changes using electrical impedance tomography and respiratory inductive plethysmography. A prospective, single-center, observational, nonrandomized study. The study was conducted in a neonatal ICU in the Netherlands. High-frequency ventilated preterm infants with respiratory distress syndrome. Cross-sectional and whole lung volume changes were continuously and simultaneously measured by, respectively, electrical impedance tomography and respiratory inductive plethysmography during a stepwise recruitment procedure. End-expiratory lung volume changes were assessed by mapping the inflation and deflation limbs using both the pressure/impedance and pressure/inductance pairs and characterized by calculating the inflection points. In addition, oscillatory tidal volume changes were assessed at each pressure step. Twenty-three infants were included in the study. Of these, eight infants had to be excluded because the quality of the registration was insufficient for analysis (two electrical impedance tomography and six respiratory inductive plethysmography). In the remaining 15 infants (gestational age 28.0 ± 2.6 wk; birth weight 1,027 ± 514 g), end-expiratory lung volume changes measured by electrical impedance tomography were significantly correlated to respiratory inductive plethysmography measurements in 12 patients (mean r = 0.93 ± 0.05). This was also true for the upper inflection point on the inflation (r = 0.91, p < 0.01) and deflation limb (r = 0.83, p < 0.01). In 13 patients, impedance and inductance data also correlated significantly on oscillatory tidal volume/pressure relationships (mean r = 0.81 ± 0.18). This study shows that cross-sectional lung volume changes measured by electrical impedance tomography are representative for the whole lung and that this concept also applies to newborn infants.

Numerical study on inter-tidal transports in coastal seas

NASA Astrophysics Data System (ADS)

Mao, Xinyan; Jiang, Wensheng; Zhang, Ping; Feng, Shizuo

2016-06-01

Inter-tidal (subtidal) transport processes in coastal sea depend on the residual motion, turbulent dispersion and relevant sources/sinks. In Feng et al. (2008), an updated Lagrangian inter-tidal transport equation, as well as new concept of Lagrangian inter-tidal concentration (LIC), has been proposed for a general nonlinear shallow water system. In the present study, the LIC is numerically applied for the first time to passive tracers in idealized settings and salinity in the Bohai Sea, China. Circulation and tracer motion in the three idealized model seas with different topography or coastline, termed as `flat-bottom', `stairs' and `cape' case, respectively, are simulated. The dependence of the LIC on initial tidal phase suggests that the nonlinearities in the stairs and cape cases are stronger than that in the flat-bottom case. Therefore, the `flat-bottom' case still meets the convectively weakly nonlinear condition. For the Bohai Sea, the simulation results show that most parts of it still meet the weakly nonlinear condition. However, the dependence of the LIS (Lagrangian inter-tidal salinity) on initial tidal phase is significant around the southern headland of the Liaodong Peninsula and near the mouth of the Yellow River. The nonlinearity in the former region is mainly related to the complicated coastlines, and that in the latter region is due to the presence of the estuarine salinity front.

On the extended stellar structure around NGC 288

NASA Astrophysics Data System (ADS)

Piatti, Andrés E.

2018-01-01

We report on observational evidence of an extra-tidal clumpy structure around NGC 288 from homogeneous coverage of a large area with the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) PS1 data base. The extra-tidal star population has been disentangled from that of the Milky Way (MW) field by using a cleaning technique that successfully reproduces the stellar density, luminosity function and colour distributions of MW field stars. We have produced the cluster stellar density radial profile and a stellar density map from independent approaches, and we found the results to be in excellent agreement - the feature extends up to 3.5 times further than the cluster tidal radius. Previous works based on shallower photometric data sets have speculated on the existence of several long tidal tails, similar to that found in Pal 5. The present outcome shows that NGC 288 could hardly have such tails, but it favours the notion that the use of interactions with the MW tidal field has been a relatively inefficient process for stripping stars off the cluster. These results point to the need for a renewed overall study of the external regions of Galactic globular clusters (GGCs) in order to reliably characterize them. It will then be possible to investigate whether there is any connection between detected tidal tails, extra-tidal stellar populations and extended diffuse halo-like structures, and the dynamical histories of GGCs in the Galaxy.

The effect of carbonated beverages on colorimetric end-tidal CO(2) determination

PubMed

Qureshi; Park; Sturmann; Hsu

2000-10-01

Esophageal intubation is a significant complication of attempted airway control. Colorimetric end-tidal CO(2) monitors are highly sensitive and specific for detecting the presence of CO(2). There are reports of false-positive end-tidal CO(2) readings from esophageal intubations in patients who had ingested carbonated beverages. OBJECTIVE: To determine whether carbonated gastric contents can affect colorimetric end-tidal CO(2) readings. METHODS: End-tidal CO(2) was measured in sacrificed piglets at measured time intervals after instillation of 5-, 10-, 15-, and 20-mL aliquots of Diet Coke were placed into the stomach via a 28-French orogastric tube followed by esophageal intubation. The stomach was completely evacuated prior to each instillation and rechecked for baseline CO(2). RESULTS: Compiled data from three piglets (20-30 kg). Piglets were not ventilated or moved and determinations were measured at 20 degrees while supine. All data collected within 2 hours postmortem (table 24-1). CONCLUSIONS: The colorimetric end-tidal CO(2) turned "yellow" and did not change to blue with extended insufflations. The CO(2) of a small quantity of carbonated beverage in the stomach could be "blown off" by multiple insufflations. We conclude that esophageal intubation in the setting of recent ingestion of a carbonated beverage may result in a false-positive end-tidal CO(2) determination.

Joint Calibration of Submarine Groundwater Discharge (SGD) with Tidal Pumping: Modeling Variable-density Groundwater Flow in Unconfined Coastal Aquifer of Apalachee Bay, Gulf of Mexico

NASA Astrophysics Data System (ADS)

Li, X.; Hu, B.; Burnett, W.; Santos, I.

2008-05-01

Submarine Groundwater Discharge (SGD) as an unseen phenomenon is now recognized as an important pathway between land and sea. These discharges typically display significant spatial and temporal variability making quantification difficult. Groundwater seepage is patchy, diffuse, and temporally variable, and thus makes the estimation of its magnitude and components is a challenging enterprise. A two-dimensional hydrogeological model is developed to the near-shore environment of an unconfined aquifer at a Florida coastal area in the northeastern Gulf of Mexico. Intense geological survey and slug tests are set to investigate the heterogeneity of this layered aquifer. By applying SEAWAT2000, considering the uncertainties caused by changes of boundary conditions, a series of variable-density-flow models incorporates the tidal-influenced seawater recirculation and the freshwater-saltwater mixing zone under the dynamics of tidal pattern, tidal amplitude and variation of water table. These are thought as the contributing factors of tidal pumping and hydraulic gradient which are the driven forces of SGD. A tidal-influenced mixing zone in the near-shore aquifer shows the importance of tidal mechanism to flow and salt transport in the process of submarine pore water exchange. Freshwater ratio in SGD is also analyzed through the comparison of Submarine Groundwater Recharge and freshwater inflow. The joint calibration with other methods (natural tracer model and seepage meter) is also discussed.

Halving the Volume of AnaConDa: Evaluation of a New Small-Volume Anesthetic Reflector in a Test Lung Model.

PubMed

Bomberg, Hagen; Meiser, Franziska; Daume, Philipp; Bellgardt, Martin; Volk, Thomas; Sessler, Daniel I; Groesdonk, Heinrich V; Meiser, Andreas

2018-05-21

Volatile anesthetics are increasingly used for sedation in intensive care units. The most common administration system is AnaConDa-100 mL (ACD-100; Sedana Medical, Uppsala, Sweden), which reflects volatile anesthetics in open ventilation circuits. AnaConDa-50 mL (ACD-50) is a new device with half the volumetric dead space. Carbon dioxide (CO2) can be retained with both devices. We therefore compared the CO2 elimination and isoflurane reflection efficiency of both devices. A test lung constantly insufflated with CO2 was ventilated with a tidal volume of 500 mL at 10 breaths/min. End-tidal CO2 (EtCO2) partial pressure was measured using 3 different devices: a heat-and-moisture exchanger (HME, 35 mL), ACD-100, and ACD-50 under 4 different experimental conditions: ambient temperature pressure (ATP), body temperature pressure saturated (BTPS) conditions, BTPS with 0.4 Vol% isoflurane (ISO-0.4), and BTPS with 1.2 Vol% isoflurane. Fifty breaths were recorded at 3 time points (n = 150) for each device and each condition. To determine device dead space, we adjusted the tidal volume to maintain normocapnia (n = 3), for each device. Thereafter, we determined reflection efficiency by measuring isoflurane concentrations at infusion rates varying from 0.5 to 20 mL/h (n = 3), for each device. EtCO2 was consistently greater with ACD-100 than with ACD-50 and HME (ISO-0.4, mean ± standard deviations: ACD-100, 52.4 ± 0.8; ACD-50, 44.4 ± 0.8; HME, 40.1 ± 0.4 mm Hg; differences of means of EtCO2 [respective 95% confidence intervals]: ACD-100 - ACD-50, 8.0 [7.9-8.1] mm Hg, P < .001; ACD-100 - HME, 12.3 [12.2-12.4] mm Hg, P < .001; ACD-50 - HME, 4.3 [4.2-4.3] mm Hg, P < .001). It was greatest under ATP, less under BTPS, and least with ISO-0.4 and BTPS with 1.2 Vol% isoflurane. In addition to the 100 or 50 mL "volumetric dead space" of each AnaConDa, "reflective dead space" was 40 mL with ACD-100 and 25 mL with ACD-50 when using isoflurane. Isoflurane reflection was highest under ATP. Under BTPS with CO2 insufflation and isoflurane concentrations around 0.4 Vol%, reflection efficiency was 93% with ACD-100 and 80% with ACD-50. Isoflurane reflection remained sufficient with the ACD-50 at clinical anesthetic concentrations, while CO2 elimination was improved. The ACD-50 should be practical for tidal volumes as low as 200 mL, allowing lung-protective ventilation even in small patients.

The role of ocean tides on groundwater-surface water exchange in a mangrove-dominated estuary: Shark River Slough, Florida Coastal Everglades, USA

USGS Publications Warehouse

Smith, Christopher G.; Price, René M.; Swarzenski, Peter W.; Stalker, Jeremy C.

2016-01-01

Low-relief environments like the Florida Coastal Everglades (FCE) have complicated hydrologic systems where surface water and groundwater processes are intimately linked yet hard to separate. Fluid exchange within these lowhydraulic-gradient systems can occur across broad spatial and temporal scales, with variable contributions to material transport and transformation. Identifying and assessing the scales at which these processes operate is essential for accurate evaluations of how these systems contribute to global biogeochemical cycles. The distribution of 222Rn and 223,224,226Ra have complex spatial patterns along the Shark River Slough estuary (SRSE), Everglades, FL. High-resolution time-series measurements of 222Rn activity, salinity, and water level were used to quantify processes affecting radon fluxes out of the mangrove forest over a tidal cycle. Based on field data, tidal pumping through an extensive network of crab burrows in the lower FCE provides the best explanation for the high radon and fluid fluxes. Burrows are irrigated during rising tides when radon and other dissolved constituents are released from the mangrove soil. Flushing efficiency of the burrows—defined as the tidal volume divided by the volume of burrows— estimated for the creek drainage area vary seasonally from 25 (wet season) to 100 % (dry season) in this study. The tidal pumping of the mangrove forest soil acts as a significant vector for exchange between the forest and the estuary. Processes that enhance exchange of O2 and other materials across the sediment-water interface could have a profound impact on the environmental response to larger scale processes such as sea level rise and climate change. Compounding the material budgets of the SRSE are additional inputs from groundwater from the Biscayne Aquifer, which were identified using radium isotopes. Quantification of the deep groundwater component is not obtainable, but isotopic data suggest a more prevalent signal in the dry season. These findings highlight the important role that both tidal- and seasonal-scale forcings play on groundwater movement in low-gradient hydrologic systems.

Noninvasive CPAP with face mask: comparison among new air-entrainment masks and the Boussignac valve.

PubMed

Mistraletti, Giovanni; Giacomini, Matteo; Sabbatini, Giovanni; Pinciroli, Riccardo; Mantovani, Elena S; Umbrello, Michele; Palmisano, Debora; Formenti, Paolo; Destrebecq, Anne L L; Iapichino, Gaetano

2013-02-01

The performances of 2 noninvasive CPAP systems (high flow and low flow air-entrainment masks) were compared to the Boussignac valve in 3 different scenarios. Scenario 1: pneumatic lung simulator with a tachypnea pattern (tidal volume 800 mL at 40 breaths/min). Scenario 2: Ten healthy subjects studied during tidal breaths and tachypnea. Scenario 3: Twenty ICU subjects enrolled for a noninvasive CPAP session. Differences between set and effective CPAP level and F(IO(2)), as well as the lowest airway pressure and the pressure swing around the imposed CPAP level, were analyzed. The lowest airway pressure and swing were correlated to the pressure-time product (area of the airway pressure curve below the CPAP level) measured with the simulator. P(aO(2)) was a subject's further performance index. Lung simulator: Boussignac F(IO(2)) was 0.54, even if supplied with pure oxygen. The air-entrainment masks had higher swing than the Boussignac (P = .007). Pressure-time product correlated better with pressure swing (Spearman correlation coefficient [ρ] = 0.97) than with lowest airway pressure (ρ = 0.92). In healthy subjects, the high-flow air-entrainment mask showed lower difference between set and effective F(IO(2)) (P < .001), and lowest airway pressure (P < .001), compared to the Boussignac valve. In all measurements the Boussignac valve showed higher than imposed CPAP level (P < .001). In ICU subjects the high-flow mask had lower swing than the Boussignac valve (P = .03) with similar P(aO(2)) increase. High-flow air-entrainment mask showed the best performance in human subjects. During high flow demand, the Boussignac valve delivered lower than expected F(IO(2)) and showed higher dynamic hyper-pressurization than the air-entrainment masks. © 2013 Daedalus Enterprises.

Tidally averaged circulation in Puget Sound sub-basins: Comparison of historical data, analytical model, and numerical model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khangaonkar, Tarang; Yang, Zhaoqing; Kim, Tae Yun

2011-07-20

Through extensive field data collection and analysis efforts conducted since the 1950s, researchers have established an understanding of the characteristic features of circulation in Puget Sound. The pattern ranges from the classic fjordal behavior in some basins, with shallow brackish outflow and compensating inflow immediately below, to the typical two-layer flow observed in many partially mixed estuaries with saline inflow at depth. An attempt at reproducing this behavior by fitting an analytical formulation to past data is presented, followed by the application of a three-dimensional circulation and transport numerical model. The analytical treatment helped identify key physical processes and parameters,more » but quickly reconfirmed that response is complex and would require site-specific parameterization to include effects of sills and interconnected basins. The numerical model of Puget Sound, developed using unstructured-grid finite volume method, allowed resolution of the sub-basin geometric features, including presence of major islands, and site-specific strong advective vertical mixing created by bathymetry and multiple sills. The model was calibrated using available recent short-term oceanographic time series data sets from different parts of the Puget Sound basin. The results are compared against (1) recent velocity and salinity data collected in Puget Sound from 2006 and (2) a composite data set from previously analyzed historical records, mostly from the 1970s. The results highlight the ability of the model to reproduce velocity and salinity profile characteristics, their variations among Puget Sound subbasins, and tidally averaged circulation. Sensitivity of residual circulation to variations in freshwater inflow and resulting salinity gradient in fjordal sub-basins of Puget Sound is examined.« less

A Cooperative Test of the Load/Unload Response Ratio Proposed Method of Earthquake Prediction

NASA Astrophysics Data System (ADS)

Trotta, J. E.; Tullis, T. E.

2004-12-01

The Load/Unload Response Ratio (LURR) method is a proposed technique to predict earthquakes that was first put forward by Yin in 1984 (Yin, 1987). LURR is based on the idea that when a region is near failure, there is an increase in the rate of seismic activity during loading of the tidal cycle relative to the rate of seismic activity during unloading of the tidal cycle. Typically the numerator of the LURR ratio is the number, or the sum of some measure of the size (e.g. Benioff strain), of small earthquakes that occur during loading of the tidal cycle, whereas the denominator is the same as the numerator except it is calculated during unloading. LURR method suggests this ratio should increase in the months to year preceding a large earthquake. Regions near failure have tectonic stresses nearly high enough for a large earthquake to occur, thus it seems more likely that smaller earthquakes in the region would be triggered when the tidal stresses add to the tectonic ones. However, until recently even the most careful studies suggested that the effect of tidal stresses on earthquake occurrence is very small and difficult to detect. New studies have shown that there is a tidal triggering effect on shallow thrust faults in areas with strong tides from ocean loading (Tanaka et al., 2002; Cochran et al., 2004). We have been conducting an independent test of the LURR method, since there would be important scientific and social implications if the LURR method were proven to be a robust method of earthquake prediction. Smith and Sammis (2003) also undertook a similar study. Following both the parameters of Yin et al. (2000) and the somewhat different ones of Smith and Sammis (2003), we have repeated calculations of LURR for the Northridge and Loma Prieta earthquakes in California. Though we have followed both sets of parameters closely, we have been unable to reproduce either set of results. A general agreement was made at the recent ACES Workshop in China between research groups studying LURR to work cooperatively to discover what is causing these differences in results. All parties will share codes and data sets, be more specific regarding the calculation parameters, and develop a synthetic data set for which we know the expected LURR value. Each research group will then test their codes and the codes of other groups on this synthetic data set. The goal of this cooperative effort is to resolve the differences in methods and results and permit more definitive conclusions on the potential usefulness of LURR in earthquake prediction.

Can tidal energy farms create temperature fronts in the coastal ocean?

NASA Astrophysics Data System (ADS)

Shapiro, G. I.

2012-04-01

Although an industrial scale tidal farm comprising a large set of submerged turbines has not been built yet, tidal power is considered to be one of potential sources of renewable energy in the future. For example, India plans to install a 50MW tidal farm in the Gulf of Kutch which could be further expanded to deliver more than 200MW. As tidal stream generators extract kinetic energy from the ocean currents, they change the circulation pattern and hence affect the marine environment. Recent research has shown ( Shapiro, 2011, Neill et al., 2009) that a tidal farm can modify currents and sediment transport outside the farm as far as up to a hundred kilometres. This paper studies the potential effect of a tidal farm on the temperature structure in a shallow sea using a 3D ocean model POLCOMS which was modified to include effects of kinetic energy extraction as detailed in (Shapiro, 2011). The model is set up in the Celtic Sea known for its high levels of tidal energy. The model is driven by 15 tidal constituents and the meteo forcing. Effects of tidal farms of varying sizes and power capacities (from 50 MW to 1500MW) have been studied during summer months. The simulated farms are placed in various locations north of the Cornish coast. It has been shown that even smaller farms can modify temperature distribution as far as a few tens of kilometres from the farm, and sometimes generate localised temperature fronts. This effect is particularly strong during the month of June when the fronts penetrate from surface to the seabed. The fronts are more pronounced during the spring tides, however they are still seen during the neaps. As the seasonal thermocline strengthens towards the end of summer, the fronts are mostly seen in the upper ocean layer, with warmer waters in the area of the farm and cooler waters outside the farm. The physical mechanism of front generation is linked to abrupt changes in the current patterns due to energy extraction from the ocean. The currents inside the farm become weaker, whilst the currents outside the farm ( at a scale comparable to the baroclinic Rossby radius) become stronger. Such stronger currents enhance the mixing of the water column outside the farm, and weaker currents inside the farm reduce turbulent mixing and facilitate formation of a stronger thermocline. The overall effect is generally similar to the formation of fronts between tidally mixed and stratified areas of a shallow sea (Simpson and Hunter, 1974). Effect of geometrically smaller farms is less pronounced as the water particles travel in and out the affected zone during the tidal cycle (over the length of the tidal excursion) and hence are influenced by the above mechanism only during a proportion of the tidal cycle. Reduced vertical mixing within the area of the farm and positive heat balance explains higher temperatures at the surface. In the beginning of summer when thermal stratification is relatively week, the thermocline is significantly altered and the fronts propagate to a greater depth. Development of a stronger thermocline towards the end of summer inhibits the effect of mixing and the fluctuations of the depth of the upper mixed layer due to energy extraction are suppressed .

Sea level rise drives increased tidal flooding frequency at tide gauges along the U.S. East and Gulf Coasts: Projections for 2030 and 2045.

PubMed

Dahl, Kristina A; Fitzpatrick, Melanie F; Spanger-Siegfried, Erika

2017-01-01

Tidal flooding is among the most tangible present-day effects of global sea level rise. Here, we utilize a set of NOAA tide gauges along the U.S. East and Gulf Coasts to evaluate the potential impact of future sea level rise on the frequency and severity of tidal flooding. Using the 2001-2015 time period as a baseline, we first determine how often tidal flooding currently occurs. Using localized sea level rise projections based on the Intermediate-Low, Intermediate-High, and Highest projections from the U.S. National Climate Assessment, we then determine the frequency and extent of such flooding at these locations for two near-term time horizons: 2030 and 2045. We show that increases in tidal flooding will be substantial and nearly universal at the 52 locations included in our analysis. Long before areas are permanently inundated, the steady creep of sea level rise will force many communities to grapple with chronic high tide flooding in the next 15 to 30 years.

Sea level rise drives increased tidal flooding frequency at tide gauges along the U.S. East and Gulf Coasts: Projections for 2030 and 2045

PubMed Central

Fitzpatrick, Melanie F.; Spanger-Siegfried, Erika

2017-01-01

Tidal flooding is among the most tangible present-day effects of global sea level rise. Here, we utilize a set of NOAA tide gauges along the U.S. East and Gulf Coasts to evaluate the potential impact of future sea level rise on the frequency and severity of tidal flooding. Using the 2001–2015 time period as a baseline, we first determine how often tidal flooding currently occurs. Using localized sea level rise projections based on the Intermediate-Low, Intermediate-High, and Highest projections from the U.S. National Climate Assessment, we then determine the frequency and extent of such flooding at these locations for two near-term time horizons: 2030 and 2045. We show that increases in tidal flooding will be substantial and nearly universal at the 52 locations included in our analysis. Long before areas are permanently inundated, the steady creep of sea level rise will force many communities to grapple with chronic high tide flooding in the next 15 to 30 years. PMID:28158209

Gas dispersal potential of infant bedding of sudden death cases. (I): CO2 accumulation around the face of infant mannequin model.

PubMed

Sakai, Jun; Takahashi, Shirushi; Funayama, Masato

2009-04-01

We assessed CO(2) gas dispersal potential of bedding that had actually been used by 26 infants diagnosed with sudden unexpected infant death using a baby mannequin model. The age of victims ranged from 1 to 12 months. In some cases, the parents alleged that the infant faces were not covered with bedding when they were found. The parent's memories, however, may not have been accurate; therefore, we examined the potential for gas dispersal based on the supposition that the bedding had covered their faces. The mannequin was connected with a respirator set on the tidal volume and respiratory rates matched with the baby's age. Before measuring, CO(2) flow was regulated in 5%+/-0.1% of end-tidal PCO(2). After the model was placed on each bedding condition, measurements were performed at least five times under each respiratory condition. Four cases showed a plateau of FiCO(2) <4.8%, 15 were 4.8-12%, and the other seven were 12% or more, when they reached a plateau. Of course, our model does not take large tissue stores of CO(2) into account. However, our model could show the potential gas dispersal ability of bedding. Especially, the latter seven bedding could have high rebreathing potential if they covered the infant's faces and the probability of environmental asphyxia should be considered.

Capnography in the Emergency Department: A Review of Uses, Waveforms, and Limitations.

PubMed

Long, Brit; Koyfman, Alex; Vivirito, Michael A

2017-12-01

Capnography has many uses in the emergency department (ED) and critical care setting, most commonly cardiac arrest and procedural sedation. This review evaluates several indications concerning capnography beyond cardiac arrest and procedural sedation in the ED, as well as limitations and specific waveforms. Capnography includes the noninvasive measurement of CO 2 , providing information on ventilation, perfusion, and metabolism in intubated and spontaneously breathing patients. Since the 1990s, capnography has been utilized extensively for cardiac arrest and procedural sedation. Qualitative capnography includes a colorimetric device, changing color on the amount of CO 2 present. Quantitative capnography provides a numeric value (end-tidal CO 2 ), and capnography most commonly includes a waveform as a function of time. Conditions in which capnography is informative include cardiac arrest, procedural sedation, mechanically ventilated patients, and patients with metabolic acidemia. Patients with seizure, trauma, and respiratory conditions, such as pulmonary embolism and obstructive airway disease, can benefit from capnography, but further study is needed. Limitations include use of capnography in conditions with mixed pathophysiology, patients with low tidal volumes, and equipment malfunction. Capnography should be used in conjunction with clinical assessment. Capnography demonstrates benefit in cardiac arrest, procedural sedation, mechanically ventilated patients, and patients with metabolic acidemia. Further study is required in patients with seizure, trauma, and respiratory conditions. It should only be used in conjunction with other patient factors and clinical assessment. Published by Elsevier Inc.

A comparison of two finite element models of tidal hydrodynamics using a North Sea data set

USGS Publications Warehouse

Walters, R.A.; Werner, F.E.

1989-01-01

Using the region of the English Channel and the southern bight of the North Sea, we systematically compare the results of two independent finite element models of tidal hydrodynamics. The model intercomparison provides a means for increasing our understanding of the relevant physical processes in the region in question as well as a means for the evaluation of certain algorithmic procedures of the two models. ?? 1989.

Twenty Years of Progress on Global Ocean Tide: The Impact of Satellite Altimetry

NASA Astrophysics Data System (ADS)

Egbert, Gary D.; Ray, Richard D.

2013-09-01

At the dawn of the era of high-precision altimetry, before the launch of TOPEX/Poseidon, ocean tides were properly viewed as a source of noise-tidal variations in ocean height would represent a very substantial fraction of what the altimeter measures, and would have to be accurately predicted and subtracted if altimetry were to achieve its potential for ocean and climate studies. But to the extent that the altimetry could be severely contaminated by tides, it also represented an unprecedented global-scale tidal data set. These new data, together with research stimulated by the need for accurate tidal corrections, led to a renaissance in tidal studies in the oceanographic community. In this paper we review contributions of altimetry to tidal science over the past 20 years, emphasizing recent progress. Mapping of tides has now been extended from the early focus on major constituents in the open ocean to include minor constituents, (e.g., long-period tides; non-linear tides in shelf waters, and in the open ocean), and into shallow and coastal waters. Global and spatially local estimates of tidal energy balance have been refined, and the role of internal tide conversion in dissipating barotropic tidal energy is now well established through modeling, altimetry, and in situ observations. However, energy budgets for internal tides, and the role of tidal dissipation in vertical ocean mixing remain controversial topics. Altimetry may contribute to resolving some of these important questions through improved mapping of low-mode internal tides. This area has advanced significantly in recent years, with several global maps now available, and progress on constraining temporally incoherent components. For the future, new applications of altimetry (e.g., in the coastal ocean, where barotropic tidal models remain inadequate), and new mission concepts (studies of the sub-mesoscale with SWOT, which will require correction for internal tides) may bring us full circle, again pushing further development of tidal models as corrections.

Twenty Years of Progress on Global Ocean Tides: The Impact of Satellite Altimetry

NASA Technical Reports Server (NTRS)

Egbert, Gary; Ray, Richard

2012-01-01

At the dawn of the era of high-precision altimetry, before the launch of TOPEX/Poseidon, ocean tides were properly viewed as a source of noise--tidal variations in ocean height would represent a very substantial fraction of what the altimeter measures, and would have to be accurately predicted and subtracted if altimetry were to achieve its potential for ocean and climate studies. But to the extent that the altimetry could be severely contaminated by tides, it also represented an unprecedented global-scale tidal data set. These new data, together with research stimulated by the need for accurate tidal corrections, led to a renaissance in tidal studies in the oceanographic community. In this paper we review contributions of altimetry to tidal science over the past 20 years, emphasizing recent progress. Mapping of tides has now been extended from the early focus on major constituents in the open ocean to include minor constituents, (e.g., long-period tides; non-linear tides in shelf waters, and in the open ocean), and into shallow and coastal waters. Global and spatially local estimates of tidal energy balance have been refined, and the role of internal tide conversion in dissipating barotropic tidal energy is now well established through modeling, altimetry, and in situ observations. However, energy budgets for internal tides, and the role of tidal dissipation in vertical ocean mixing remain controversial topics. Altimetry may contribute to resolving some of these important questions through improved mapping of low-mode internal tides. This area has advanced significantly in recent years, with several global maps now available, and progress on constraining temporally incoherent components. For the future, new applications of altimetry (e.g., in the coastal ocean, where barotropic tidal models remain inadequate), and new mission concepts (studies of the submesoscale with SWOT, which will require correction for internal tides) may bring us full circle, again pushing further development of tidal models as corrections.

Beyond the Golden Hours: Caring for Septic Patients After the Initial Resuscitation.

PubMed

Gelinas, Jean P; Walley, Keith R

2016-06-01

Recognition and management of agitation, delirium, and pain are key areas. Reduced use of sedatives is an important measure that must be coupled with increased patient engagement, mobilization, and exercise. Use of low tidal volumes and low mean airway pressures during mechanical ventilation is helpful. A key hemodynamic principle following early aggressive volume resuscitation is subsequent careful assessment to avoid unnecessary additional volume administration and adverse consequences of frank volume overload. Substantial evidence now supports a lower hemoglobin transfusion threshold of 7 g/dL. A rush to initiate enteral or parenteral feeds is not clearly supported by the current evidence. Copyright © 2016 Elsevier Inc. All rights reserved.

Use of volume-targeted non-invasive bilevel positive airway pressure ventilation in a patient with amyotrophic lateral sclerosis*,**

PubMed Central

Diaz-Abad, Montserrat; Brown, John Edward

2014-01-01

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease in which most patients die of respiratory failure. Although volume-targeted non-invasive bilevel positive airway pressure (BPAP) ventilation has been studied in patients with chronic respiratory failure of various etiologies, its use in ALS has not been reported. We present the case of a 66-year-old woman with ALS and respiratory failure treated with volume-targeted BPAP ventilation for 15 weeks. Weekly data downloads showed that disease progression was associated with increased respiratory muscle weakness, decreased spontaneous breathing, and increased use of non-invasive positive pressure ventilation, whereas tidal volume and minute ventilation remained relatively constant. PMID:25210968

Dynamics of the Local Supercluster: 2017

NASA Astrophysics Data System (ADS)

Shaya, Edward; Tully, R. Brent; Hoffman, Yehuda; Pomarede, Daniel

2018-01-01

The fully nonlinear gravitationally induced trajectories of a nearly complete set of galaxies, groups, and clusters in the Local Supercluster (LSC) are constructed in a Numerical Action Method (NAM) model constrained by recent data from the CosmicFlows survey and various distance indicators. We add the gravity field due to the inhomogeneities external to the sample sphere by linear analysis of larger scale peculiar flow measurements. The best fit, when setting the value of Ho to the CosmicFlows value of 75 /km/s/Mpc and the WMAP value of Ωm = 0.244 consistent with that Ho, occurs with the following parameter settings: ΩIGM = 0.077±0.016, M/LK = 40±2 L100.15 M⊙/L⊙ (L10 is K-band luminosity in units of 1010L⊙), a Virgo mass of 6.3±0.8 x1014 M⊙ (M/LK = 113±15 M⊙/L⊙), and a sum for the mass of M31 and MW of 5.15±0.35 x 1012 M⊙. When a constant value mass-to-light ratio is used, its best value is M/LK = 58±3 M⊙/L⊙, and the other parameters are only slightly changed.Patterns in the orbits reveal the main properties of the region within 38 Mpc. Across the entire volume, every galaxy above the supergalactic equator has a peculiar velocity of descent toward the equatorial plane, a manifestation of the pervasive low densities at positive supergalactic latitudes. Another global feature is the tidal flow toward the Centaurus‑Norma Great Attractor that lies just beyond the study volume.

The relationship between wheezing and lung mechanics during methacholine-induced bronchoconstriction in asthmatic subjects.

PubMed

Spence, D P; Graham, D R; Jamieson, G; Cheetham, B M; Calverley, P M; Earis, J E

1996-08-01

Wheeze is a classic sign of airflow obstruction but relatively little is known of its mechanism of production or its relationship to the development of airflow obstruction. We studied eight asthmatic subjects age (mean +/- 5D) 42 +/- 5 yr, FEV1 2.46 +/- 0.36 L during an extended, symptom-limited methacholine challenge test. Breath sounds were detected by a microphone over the right upper anterior chest. Spectral analysis was by a fast Fourier transform algorithm. Mean FEV1 fell by 51 +/- 14% to 1.28 +/- 0.61 L during the challenge and airways resistance increased by 119 +/- 50%. There were no consistent changes in breathing pattern or tidal volume during the challenge. Wheeze occurred late in the challenge at the highest concentration of methacholine administered and only after expiratory tidal flow limitation had been reached. Five subjects developed wheeze on tidal breathing, the remaining three only wheezed on deep breathing. Wheezing sounds were reproducible between breaths, coefficient of variation of starting sound frequency was 4.2% and ending frequency 12%. Mean frequency of expiratory wheezes was 669 +/- 100 Hz and inspiratory wheezes 710 +/- 76 Hz. Expiratory wheeze fell in pitch during a breath (mean fall in sound frequency 187 +/- 43 Hz) but inspiratory wheezes were more variable. Expiratory wheezes occurred late in the respiratory cycle at a mean of 58% of the maximal tidal expiratory flow, whereas inspiratory wheezes occurred around maximal tidal inspiratory flows, suggesting that the mechanisms of production of inspiratory and expiratory wheezes may be different. In this model, the presence of wheeze during tidal breathing was a sign of severe airflow limitation.

Design and Evaluation of Scour for Bridges Using HEC-18 (Volume 3 of 3).

DOT National Transportation Integrated Search

2017-07-04

The overall objective of this research is the development of a new approach for evaluating bridge scour for New Jersey's bridges on non-tidal waterways. The study commenced with a web-based survey of scour practice within the U.S. and a literature re...

Design and Evaluation of Scour for Bridges Using HEC-18 (Volume 1 of 3).

DOT National Transportation Integrated Search

2017-07-04

The overall objective of this research is the development of a new approach for evaluating bridge scour for New Jersey's bridges on non-tidal waterways. The study commenced with a web-based survey of scour practice within the U.S. and a literature re...

High-Frequency Percussive Ventilation: Pneumotachograph Validation and Tidal Volume Analysis

DTIC Science & Technology

2010-06-01

protocol, preliminary experience has shown that the flow sensor is amenable to near-automated “plug-and- play ” adaptability, permitting clinicians the...400. 6. Velmahos GC, Chan LS, Tatevossian R, Cornwell EE 3rd, Dough - erty WR, Escudero J, Demetriades D. High-frequency percussive ventilation

Design and Evaluation of Scour for Bridges Using HEC-18 (Volume 2 of 3).

DOT National Transportation Integrated Search

2017-07-04

The overall objective of this research is the development of a new approach for evaluating bridge scour for New Jersey's bridges on non-tidal waterways. The study commenced with a web-based survey of scour practice within the U.S. and a literature re...

Effects of Simulated Pathophysiology on the Performance of a Decision Support Medical Monitoring System for Early Detection of Hemodynamic Decompensation in Humans

DTIC Science & Technology

2015-10-01

Arterial oxygen saturation was monitored 130 using a finger pulse oximeter and end-tidal CO2 (ETCO2) was collected from a nasal cannula 131 (Cardiocap/5...Johnson et al, J Appl Physiol 2014 PMID 24876357. 5 Keywords Trauma, coagulation, central venous pressure, stroke volume, pulse pressure...Johnson BD, Curry TB, Convertino VA, & Joyner MJ. The association between pulse pressure and stroke volume during lower body negative pressure and

Dredging Optimization of an Inlet System for Adjacent Shore Protection Projects Using CMS and GenCade

DTIC Science & Technology

2012-07-01

Beaches + Anastasia cu y d/ yr Table 1. Measured Ebb-delta Volume of St. Augustine Inlet, Florida at the 30ft contour (Legault et al. 2012...along Anastasia State Park). The permeability of the terminal groins (between 0% and 100%) were estimated based on visual inspection of sand...lft) Percent volume change for the three reaches and the ebb-tidal delta are shown in Figure 15 for all modeled alternatives. Anastasia State

Tidal-bundle sequences in the Jordan Sandstone (Upper Cambrian), southeastern Minnesota, U.S.A.: Evidence for tides along inboard shorelines of the Sauk Epicontinental Sea

USGS Publications Warehouse

Tape, C.H.; Cowan, Clinton A.; Runkel, Anthony C.

2003-01-01

This study documents for the first time tidal bundling in a lower Paleozoic sheet sandstone from the cratonic interior of North America, providing insights into the hydrodynamics of ancient epicontinental seas. The Jordan Sandstone (Upper Cambrian) in the Upper Mississippi Valley contains large-scale planar tabular cross-sets with tidal-bundle sequences, which were analyzed in detail at an exceptional exposure. Tidal-bundle sequences (neap-spring-neap cycles) were delineated by foreset thickening-thinning patterns and composite shale drapes, the latter of which represent accumulations of mud during the neap tides of neap-spring-neap tidal cycles. Fourier analysis of the bundle thickness data from the 26 measurable bundle sequences revealed cycles ranging from 15 to 34 bundles per sequence, which suggests a semidiurnal or mixed tidal system along this part of the Late Cambrian shoreline. We extend the tidal interpretation to widespread occurrences of the same facies in outcrops of lesser quality, where the facies is recognizable but too few bundles are exposed for tidal cycles to be measured. By doing so, this study shows that tidally generated deposits have a significant geographic and temporal extent in Upper Cambrian strata of central mid-continent North America. The deposition and preservation of tidal facies was related to the intermittent development of shoreline embayments during transgressions. The tidally dominated deposits filled ravined topographies that were repeatedly developed on the updip parts of the shoreface. Resulting coastal geomorphologies, accompanied perhaps by larger-scale changes in basinal conditions and/or configuration, led to changes in depositional conditions from wave-dominated to tide-dominated. Outcrops of the Jordan Sandstone tidal facies in the Upper Mississippi Valley represent the farthest inboard recorded transmission of ocean-generated tides in the Laurentian epicontinental seas, demonstrating that tidal currents were significant agents in the transport of sand along the far cratonic interior shorelines of Cambrian North America. The results of this study improve the facies-level understanding of the genesis of sheet sandstones. Furthermore, tidalites documented here occur in a specific position within a sequence stratigraphic architecture for the Jordan Sandstone. This provides a framework to compare these ancient deposits and processes to younger (e.g., Carboniferous) epicontinental systems where stratal and sediment dynamics are better documented. ?? 2003, SEPM (Society for Sedimentary Geology).

Tidal and residual currents across the northern Ryukyu Island chain observed by ferryboat ADCP

NASA Astrophysics Data System (ADS)

Liu, Zhao-Jun; Nakamura, Hirohiko; Zhu, Xiao-Hua; Nishina, Ayako; Dong, Menghong

2017-09-01

Ferryboat Acoustic Doppler Current Profiler (ADCP) data from 2003 to 2012 are used to estimate the tidal and residual currents across the northern Ryukyu Island chain (RIC) between the islands of Okinawa and Amamioshima. In this region, the M2 tide current is the strongest tidal component, and the K1 tide current is the strongest diurnal tidal component. The corresponding maximum amplitudes are 40 and 34 cm s-1, respectively. After removal of the tidal currents, the mean volume transport, 1.5 ± 2.7 Sv, flows into the East China Sea (ECS) from the western North Pacific through four channels in this area. In an empirical orthogonal function (EOF) analysis performed to clarify the temporal and spatial variability of currents through the four channels, the first two EOF modes account for 71% and 18% of the total variance, respectively. The EOF1 mode shows a clear bottom-intensified mode through the deep channel, which is likely to be formed by the propagation of bottom-trapped long topographic Rossby wave caused by the impingement of westward-propagating mesoscale eddies upon the eastern slope of the northern RIC. The EOF2 mode has significant seasonal variability and may be driven by the wind stress prevailing over the Kuroshio flow region around the northern RIC in October-November. This study provides observational evidence of the water exchanges across the northern RIC, which is essential for constructing a circulation scheme in the North Pacific subtropical western boundary region.

Holocene depocenter migration and sediment accumulation in Delaware Bay: A submerging marginal marine sedimentary basin

USGS Publications Warehouse

Fletcher, C. H.; Knebel, H.J.; Kraft, J.C.

1992-01-01

The Holocene transgression of the Delaware Bay estuary and adjacent Atlantic coast results from the combined effect of regional crustal subsidence and eustasy. Together, the estuary and ocean coast constitute a small sedimentary basin whose principal depocenter has migrated with the transgression. A millenial time series of isopach and paleogeographic reconstructions for the migrating depocenter outlines the basin-wide pattern of sediment distribution and accumulation. Upland sediments entering the basin through the estuarine turbidity maximum accumulate in tidal wetland or open water sedimentary environments. Wind-wave activity at the edge of the tidal wetlands erodes the aggraded Holocene section and builds migrating washover barriers. Along the Atlantic and estuary coasts of Delaware, the area of the upland environment decreases from 2.0 billion m2 to 730 million m2 during the transgression. The area of the tidal wetland environment increases from 140 million to 270 million m2, and due to the widening of the estuary the area of open water increases from 190 million to 1.21 billion m2. Gross uncorrected rates of sediment accumulation for the tidal wetlands decrease from 0.64 mm/yr at 6 ka to 0.48 mm/yr at 1 ka. In the open water environments uncorrected rates decrease from 0.50 mm/yr to 0.04 mm/yr over the same period. We also present data on total sediment volumes within the tidal wetland and open water environments at specific intervals during the Holocene. 

Methods for accurate estimation of net discharge in a tidal channel

USGS Publications Warehouse

Simpson, M.R.; Bland, R.

2000-01-01

Accurate estimates of net residual discharge in tidally affected rivers and estuaries are possible because of recently developed ultrasonic discharge measurement techniques. Previous discharge estimates using conventional mechanical current meters and methods based on stage/discharge relations or water slope measurements often yielded errors that were as great as or greater than the computed residual discharge. Ultrasonic measurement methods consist of: 1) the use of ultrasonic instruments for the measurement of a representative 'index' velocity used for in situ estimation of mean water velocity and 2) the use of the acoustic Doppler current discharge measurement system to calibrate the index velocity measurement data. Methods used to calibrate (rate) the index velocity to the channel velocity measured using the Acoustic Doppler Current Profiler are the most critical factors affecting the accuracy of net discharge estimation. The index velocity first must be related to mean channel velocity and then used to calculate instantaneous channel discharge. Finally, discharge is low-pass filtered to remove the effects of the tides. An ultrasonic velocity meter discharge-measurement site in a tidally affected region of the Sacramento-San Joaquin Rivers was used to study the accuracy of the index velocity calibration procedure. Calibration data consisting of ultrasonic velocity meter index velocity and concurrent acoustic Doppler discharge measurement data were collected during three time periods. Two sets of data were collected during a spring tide (monthly maximum tidal current) and one of data collected during a neap tide (monthly minimum tidal current). The relative magnitude of instrumental errors, acoustic Doppler discharge measurement errors, and calibration errors were evaluated. Calibration error was found to be the most significant source of error in estimating net discharge. Using a comprehensive calibration method, net discharge estimates developed from the three sets of calibration data differed by less than an average of 4 cubic meters per second, or less than 0.5% of a typical peak tidal discharge rate of 750 cubic meters per second.

A description of the tides in the Eastern North Atlantic

NASA Astrophysics Data System (ADS)

Fanjul, Enrique Alvarez; Gómez, Begoña Pérez; Sánchez-Arévalo, Ignacio Rodríguez

A description of the Eastern North Atlantic tidal dynamics (in a region spanning from 20°N to 48°N in latitude and from 34°W to 0° in longitude) is obtained by means of new in situ measurements and numerical modelling based on TOPEX/POSEIDON-derived data sets. The main source of measurements is the tide gauge network REDMAR (RED de MAReógrafos de Puertos del Estado), operative since July 1992 and managed by Clima Marítimo (Puertos del Estado). Results derived from the harmonic analysis of the first years of measurements are presented and compared with model results. In order to obtain a global picture of the tides in the region, a large compilation of harmonic constants obtained from other institutes is included. The availability of new TOPEX/POSEIDON-derived harmonic constants data sets provides a chance to include the benefits derived from satellite altimetry in high resolution regional applications of numerical models. Richard Ray's tidal model (Ray et al., 1994), based on a response type tidal analysis of TOPEX/POSEIDON data, was employed within a model of the studied area. The numerical model employed is HAMSOM, a 3-D finite difference code developed both by the Institut für Meereskunde (Hamburg University) and Clima Marítimo. Results from simulations of seven major harmonics are presented, providing a comprehensive view of tidal dynamics, including current information. The results of tidal simulations show good agreement between semidiurnal harmonic components and the values measured by both coastal and pelagic tidal gauges and by current meters. The modelled diurnal constituents show larger relative differences with measurements than semidiurnal harmonics, especially concerning the phase lags. The non-linear transfer of energy from semidiurnal to higher order harmonics, such as M 4 and M 6, was mapped. Those transfers were found to be important only in two areas: the French continental shelf in the Bay of Biscay and the widest part of the African shelf, south of Cabo Bojador.

Tidal breathing parameters measured using structured light plethysmography in healthy children and those with asthma before and after bronchodilator.

PubMed

Hmeidi, Hamzah; Motamedi-Fakhr, Shayan; Chadwick, Edward; Gilchrist, Francis J; Lenney, Warren; Iles, Richard; Wilson, Rachel C; Alexander, John

2017-03-01

Structured light plethysmography (SLP) is a light-based, noncontact technique that measures tidal breathing by monitoring displacements of the thoracoabdominal (TA) wall. We used SLP to measure tidal breathing parameters and their within-subject variability (v) in 30 children aged 7-16 years with asthma and abnormal spirometry (forced expiratory volume in 1 sec [FEV1] <80% predicted) during a routine clinic appointment. As part of standard care, the reversibility of airway obstruction was assessed by repeating spirometry after administration of an inhaled bronchodilator. In this study, SLP was performed before and after bronchodilator administration, and also once in 41 age-matched controls. In the asthma group, there was a significant increase in spirometry-assessed mean FEV1 after administration of bronchodilator. Of all measured tidal breathing parameters, the most informative was the inspiratory to expiratory TA displacement ratio (IE50 SLP , calculated as TIF50 SLP /TEF50 SLP , where TIF50 SLP is tidal inspiratory TA displacement rate at 50% of inspiratory displacement and TEF50 SLP is tidal expiratory TA displacement rate at 50% of expiratory displacement). Median (m) IE50 SLP and its variability (vIE50 SLP ) were both higher in children with asthma (prebronchodilator) compared with healthy children (mIE50 SLP : 1.53 vs. 1.22, P  <   0.001; vIE50 SLP : 0.63 vs. 0.47, P  <   0.001). After administration of bronchodilators to the asthma group, mIE50 SLP decreased from 1.53 to 1.45 ( P  =   0.01) and vIE50 SLP decreased from 0.63 to 0.60 ( P  =   0.04). SLP-measured tidal breathing parameters could differentiate between children with and without asthma and indicate a response to bronchodilator. © 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

Studies of Tidal and Planetary Wave Variability in the Middle Atmosphere using UARS and Correlative MF Radar Data

NASA Technical Reports Server (NTRS)

Fritts, David C.

1996-01-01

The goals of this research effort have been to use MF radar and UARS/HRDI wind measurements for correlative studies of large-scale atmospheric dynamics, focusing specifically on the tidal and various planetary wave structures occurring in the middle atmosphere. We believed that the two data sets together would provide the potential for much more comprehensive studies than either by itself, since they jointly would allow the removal of ambiguities in wave structure that are difficult to resolve with either data set alone. The joint data were to be used for studies of wave structure, variability, and the coupling of these motions to mean and higher-frequency motions.

Establishing Functional Relationships between Abiotic Environment, Macrophyte Coverage, Resource Gradients and the Distribution of Mytilus trossulus in a Brackish Non-Tidal Environment.

PubMed

Kotta, Jonne; Oganjan, Katarina; Lauringson, Velda; Pärnoja, Merli; Kaasik, Ants; Rohtla, Liisa; Kotta, Ilmar; Orav-Kotta, Helen

2015-01-01

Benthic suspension feeding mussels are an important functional guild in coastal and estuarine ecosystems. To date we lack information on how various environmental gradients and biotic interactions separately and interactively shape the distribution patterns of mussels in non-tidal environments. Opposing to tidal environments, mussels inhabit solely subtidal zone in non-tidal waterbodies and, thereby, driving factors for mussel populations are expected to differ from the tidal areas. In the present study, we used the boosted regression tree modelling (BRT), an ensemble method for statistical techniques and machine learning, in order to explain the distribution and biomass of the suspension feeding mussel Mytilus trossulus in the non-tidal Baltic Sea. BRT models suggested that (1) distribution patterns of M. trossulus are largely driven by separate effects of direct environmental gradients and partly by interactive effects of resource gradients with direct environmental gradients. (2) Within its suitable habitat range, however, resource gradients had an important role in shaping the biomass distribution of M. trossulus. (3) Contrary to tidal areas, mussels were not competitively superior over macrophytes with patterns indicating either facilitative interactions between mussels and macrophytes or co-variance due to common stressor. To conclude, direct environmental gradients seem to define the distribution pattern of M. trossulus, and within the favourable distribution range, resource gradients in interaction with direct environmental gradients are expected to set the biomass level of mussels.

Establishing Functional Relationships between Abiotic Environment, Macrophyte Coverage, Resource Gradients and the Distribution of Mytilus trossulus in a Brackish Non-Tidal Environment

PubMed Central

Kotta, Jonne; Oganjan, Katarina; Lauringson, Velda; Pärnoja, Merli; Kaasik, Ants; Rohtla, Liisa; Kotta, Ilmar; Orav-Kotta, Helen

2015-01-01

Benthic suspension feeding mussels are an important functional guild in coastal and estuarine ecosystems. To date we lack information on how various environmental gradients and biotic interactions separately and interactively shape the distribution patterns of mussels in non-tidal environments. Opposing to tidal environments, mussels inhabit solely subtidal zone in non-tidal waterbodies and, thereby, driving factors for mussel populations are expected to differ from the tidal areas. In the present study, we used the boosted regression tree modelling (BRT), an ensemble method for statistical techniques and machine learning, in order to explain the distribution and biomass of the suspension feeding mussel Mytilus trossulus in the non-tidal Baltic Sea. BRT models suggested that (1) distribution patterns of M. trossulus are largely driven by separate effects of direct environmental gradients and partly by interactive effects of resource gradients with direct environmental gradients. (2) Within its suitable habitat range, however, resource gradients had an important role in shaping the biomass distribution of M. trossulus. (3) Contrary to tidal areas, mussels were not competitively superior over macrophytes with patterns indicating either facilitative interactions between mussels and macrophytes or co-variance due to common stressor. To conclude, direct environmental gradients seem to define the distribution pattern of M. trossulus, and within the favourable distribution range, resource gradients in interaction with direct environmental gradients are expected to set the biomass level of mussels. PMID:26317668

First-time imaging of effects of inspired oxygen concentration on regional lung volumes and breathing pattern during hypergravity.

PubMed

Borges, João Batista; Hedenstierna, Göran; Bergman, Jakob S; Amato, Marcelo B P; Avenel, Jacques; Montmerle-Borgdorff, Stéphanie

2015-02-01

Aeroatelectasis can develop in aircrew flying the latest generation high-performance aircraft. Causes alleged are relative hyperoxia, increased gravity in the head-to-foot direction (+Gz), and compression of legs and stomach by anti-G trousers (AGT). We aimed to assess, in real time, the effects of hyperoxia, +Gz accelerations and AGT inflation on changes in regional lung volumes and breathing pattern evaluated in an axial plane by electrical impedance tomography (EIT). The protocol mimicked a routine peacetime flight in combat aircraft. Eight subjects wearing AGT were studied in a human centrifuge during 1 h 15 min exposure of +1 to +3.5Gz. They performed this sequence three times, breathing AIR, 44.5 % O2 or 100 % O2. Continuous recording of functional EIT enabled uninterrupted assessment of regional lung volumes at the 5th intercostal level. Breathing pattern was also monitored. EIT data showed that +3.5Gz, compared with any moment without hypergravity, caused an abrupt decrease in regional tidal volume (VT) and regional end-expiratory lung volume (EELV) measured in the EIT slice, independently of inspired oxygen concentration. Breathing AIR or 44.5 % O2, sub-regional EELV measured in the EIT slice decreased similarly in dorsal and ventral regions, but sub-regional VT measured in the EIT slice decreased significantly more dorsally than ventrally. Breathing 100 % O2, EELV and VT decreased similarly in both regions. Inspired tidal volume increased in hyperoxia, whereas breathing frequency increased in hypergravity and hyperoxia. Our findings suggest that hypergravity and AGT inflation cause airway closure and air trapping in gravity-dependent lung regions, facilitating absorption atelectasis formation, in particular during hyperoxia.

Upper airway CO2 receptors in tegu lizards: localization and ventilatory sensitivity.

PubMed

Coates, E L; Ballam, G O

1987-01-01

1. Tidal volume, end-tidal CO2, and ventilatory frequency in Tupinambis nigropunctatus were measured in response to CO2 (1-4%) delivered to either the mouth or nares. Additionally, the sensitivity of the ventilatory response to nasal CO2 was evaluated at CO2 concentrations less than 1%. The ventilatory parameters were also measured in response to CO2 (1-4%) delivered to the nares after the olfactory peduncle was transected. 2. It was found that (0.4-4%) nasal CO2 depressed ventilatory frequency by 9% to 83% respectively, while tidal volume was not significantly altered. CO2 (1-4%) delivered to the mouth produced no apparent changes in any of the ventilatory parameters. Following transection of the olfactory peduncle, nasal CO2 was ineffective in producing any change in ventilatory frequency or depth. 3. These findings indicate that CO2-sensitive receptors are located in either the nasal or vomeronasal membranes of tegu lizards and that the olfactory peduncle must be intact for these receptors to affect ventilatory changes in response to elevated CO2 concentrations. The receptors are capable of mediating a ventilatory response to CO2 concentrations lower than those found in either expired air or in confined spaces such as occupied burrows. 4. The discrepancies in the ventilatory responses of lizards and snakes to inspired CO2 reported in past experiments may be partially explained by the presence of nasal or vomeronasal CO2-sensitive receptors.

Tides and deltaic morphodynamics

NASA Astrophysics Data System (ADS)

Plink-Bjorklund, Piret

2016-04-01

Tide-dominated and tide-influenced deltas are not widely recognized in the ancient record, despite the numerous modern and Holocene examples, including eight of the twelve modern largest deltas in the world, like the Ganges-Brahmaputra, Amazon, Chang Jiang, and Irrawadi. Furthermore, tide-dominated or tide-influenced deltas are suggested to be more common in inner-shelf or embayment settings rather than close to or at a shelf edge, primarily because wave energy is expected to be higher and tidal energy lower in outer shelf and shelf-edge areas. Thus, most shelf-edge deltas are suggested to be fluvial or wave dominated. However, there are ancient examples of tide-influenced shelf-edge deltas, indicating that the controls on tidal morphodynamics in deltas are not yet well understood. This paper asks the following questions: (1) How do tides influence delta deposition, beyond creating recognizable tidal facies? (2) Does tidal reworking create specific geometries in delta clinoforms? (3) Does tidal reworking change progradation rates of deltas? (4) Is significant tidal reworking of deltas restricted to inner-shelf deltas only? (5) What are the conditions at which deltas may be tidally influenced or tide-dominated in outer-shelf areas or at the shelf edge? (6) What are the main morphodynamic controls on the degree of tidal reworking of deltas? The paper utilizes a dataset of multiple ancient and modern deltas, situated both on the shelf and shelf edge. We show that beyond the commonly recognized shore-perpendicular morphological features and the recognizable tidal facies, the main effects of tidal reworking of deltas are associated with delta clinoform morphology, morphodynamics of delta lobe switching, delta front progradation rates, and the nature of the delta plain. Strong tidal influence is here documented to promote subaqueous, rapid progradation of deltas, by efficiently removing sediment from river mouth and thus reducing mouth bar aggradation and fluvial delta plain construction rates. Such subaqueous progradation of the delta front is decoupled from shoreline progradation. The delta plain of such tide-dominated deltas consists of a few distributary channels and tidal flats on top of the emerged tidal bars. The delta front clinoforms become gentler and longer, as ebb tidal currents together with river effluent efficiently transport sediment to the basin. Tide-dominated deltas tend to maintain a funnel shape and show low lobe switching rates, compared to fluvial-dominated and tide-influenced deltas. The funnel and thus river mouth position is further stabilized by fine-grained sediment accumulation on marginal tidal flats due to the flood current sediment transport. However, all these effect weaken as the deltas prograde to the shelf edge, due to the loss of vertical (and lateral) restriction and tidal amplification. Here significant tidal reworking tends to be restricted to topographic irregularities, caused by incision, delta-lobe or mouth bar deposition and avulsions, or tectonic processes. The role of such topographic restrictions is twofold, by reducing wave energy and amplifying tidal energy.

Loss of CDKL5 disrupts respiratory function in mice.

PubMed

Lee, Kun-Ze; Liao, Wenlin

2018-01-01

Cyclin-dependent kinase-like 5 (CDKL5) is an X-linked gene encoding a serine-threonine kinase that is highly expressed in the central nervous system. Mutations in CDKL5 cause neurological and psychiatric symptoms, including early-onset seizures, motor dysfunction, autistic features and sleep breathing abnormalities in patients. It remains to be addressed whether loss of CDKL5 causes respiratory dysfunction in mice. Here, we examined the respiratory pattern of male Cdkl5 -/y mice at 1-3 months of age during resting breathing and respiratory challenge (i.e., hypoxia and hypercapnia) via whole body plethysmography. The results demonstrated that the resting respiratory frequency and tidal volume of Cdkl5 -/y mice was unaltered compared to that of WT mice at 1 month of age. However, these mutant mice exhibit transient reduction in tidal volume during respiratory challenge even the reduction was restored at 2 months of age. Notably, the sigh-breathing pattern was changed in Cdkl5 -/y mice, showing a transient reduction in sigh volume at 1-2 month of age and long-term attenuation of peak expiratory airflow from 1 to 3 month of age. Therefore, loss of CDKL5 causes breathing deficiency, supporting a CDKL5-mediated regulation of respiratory function in mice. Copyright © 2017 Elsevier B.V. All rights reserved.

Inspiratory flow rate, not type of incentive spirometry device, influences chest wall motion in healthy individuals.

PubMed

Chang, Angela T; Palmer, Kerry R; McNaught, Jessie; Thomas, Peter J

2010-08-01

This study investigated the effect of flow rates and spirometer type on chest wall motion in healthy individuals. Twenty-one healthy volunteers completed breathing trials to either two times tidal volume (2xV(T)) or inspiratory capacity (IC) at high, low, or natural flow rates, using a volume- or flow-oriented spirometer. The proportions of rib cage movement to tidal volume (%RC/V(T)), chest wall diameters, and perceived level of exertion (RPE) were compared. Low and natural flow rates resulted in significantly lower %RC/V(T) compared to high flow rate trials (p=0.001) at 2xV(T). Low flow trials also resulted in significantly less chest wall motion in the upper anteroposterior direction than high and natural flow rates (p<0.001). At IC, significantly greater movement occurred in the abdominal lateral direction during low flow compared to high and natural flow trials (both p<0.003). RPE was lower for the low flow trials compared to high flow trials at IC and 2xV(T) (p<0.01). In healthy individuals, inspiratory flow (not device type) during incentive spirometry determines the resultant breathing pattern. High flow rates result in greater chest wall motion than low flow rates.

Respiratory muscles stretching acutely increases expansion in hemiparetic chest wall.

PubMed

Rattes, Catarina; Campos, Shirley Lima; Morais, Caio; Gonçalves, Thiago; Sayão, Larissa Bouwman; Galindo-Filho, Valdecir Castor; Parreira, Verônica; Aliverti, Andrea; Dornelas de Andrade, Armèle

2018-08-01

Individuals post-stroke may present restrictive ventilatory pattern generated from changes in the functionality of respiratory system due to muscle spasticity and contractures. Objective was to assess the acute effects after respiratory muscle stretching on the ventilatory pattern and volume distribution of the chest wall in stroke subjects. Ten volunteers with right hemiparesis after stroke and a mean age of 60 ± 5.7 years were randomised into the following interventions: respiratory muscle stretching and at rest (control). The ventilatory pattern and chest wall volume distribution were evaluated through optoelectronic plethysmography before and immediately after each intervention. Respiratory muscle stretching promoted a significant acute increase of 120 mL in tidal volume, with an increase in minute ventilation, mean inspiratory flow and mean expiratory flow compared with the control group. Pulmonary ribcage increased 50 mL after stretching, with 30 mL of contribution to the right pulmonary rib cage (hemiparetic side) in comparison to the control group. Respiratory muscle stretching in patients with right hemiparesis post-stroke demonstrated that acute effects improve the expansion of the respiratory system during tidal breathing. NCT02416349 (URL: https://clinicaltrials.gov/ct2/show/ NCT02416349). Copyright © 2018 Elsevier B.V. All rights reserved.

Breathing patterns in preterm and term infants immediately after birth.

PubMed

te Pas, Arjan B; Wong, Connie; Kamlin, C Omar F; Dawson, Jennifer A; Morley, Colin J; Davis, Peter G

2009-03-01

There is limited data describing how preterm and term infants breathe spontaneously immediately after birth. We studied spontaneously breathing infants >or=29 wk immediately after birth. Airway flow and tidal volume were measured for 90 s using a hot wire anemometer attached to a facemask. Twelve preterm and 13 term infants had recordings suitable for analysis. The median (interquartile range) proportion of expiratory braking was very high in both groups (preterm 90 [74-99] vs. term 87 [74-94]%; NS). Crying pattern was the predominant breathing pattern for both groups (62 [36-77]% vs. 64 [46-79]%; NS). Preterm infants showed a higher incidence of expiratory hold pattern (9 [4-17]% vs. 2 [0-6]%; p = 0.02). Both groups had large tidal volumes (6.7 [3.9] vs. 6.5 [4.1] mL/kg), high peak inspiratory flows (5.7 [3.8] vs. 8.0 [5] L/min), lower peak expiratory flow (3.6 [2.4] vs. 4.8 [3.2] L/min), short inspiration time (0.31 [0.13] vs. 0.32 [0.16] s) and long expiration time (0.93 [0.64] vs. 1.14 [0.86] s). Directly after birth, both preterm and term infants frequently brake their expiration, mostly by crying. Preterm infants use significantly more expiratory breath holds to defend their lung volume.

A possible formation channel for blue hook stars in globular cluster - II. Effects of metallicity, mass ratio, tidal enhancement efficiency and helium abundance

NASA Astrophysics Data System (ADS)

Lei, Zhenxin; Zhao, Gang; Zeng, Aihua; Shen, Lihua; Lan, Zhongjian; Jiang, Dengkai; Han, Zhanwen

2016-12-01

Employing tidally enhanced stellar wind, we studied in binaries the effects of metallicity, mass ratio of primary to secondary, tidal enhancement efficiency and helium abundance on the formation of blue hook (BHk) stars in globular clusters (GCs). A total of 28 sets of binary models combined with different input parameters are studied. For each set of binary model, we presented a range of initial orbital periods that is needed to produce BHk stars in binaries. All the binary models could produce BHk stars within different range of initial orbital periods. We also compared our results with the observation in the Teff-logg diagram of GC NGC 2808 and ω Cen. Most of the BHk stars in these two GCs locate well in the region predicted by our theoretical models, especially when C/N-enhanced model atmospheres are considered. We found that mass ratio of primary to secondary and tidal enhancement efficiency have little effects on the formation of BHk stars in binaries, while metallicity and helium abundance would play important roles, especially for helium abundance. Specifically, with helium abundance increasing in binary models, the space range of initial orbital periods needed to produce BHk stars becomes obviously wider, regardless of other input parameters adopted. Our results were discussed with recent observations and other theoretical models.

Measurements of evaporated perfluorocarbon during partial liquid ventilation by a zeolite absorber.

PubMed

Proquitté, Hans; Rüdiger, Mario; Wauer, Roland R; Schmalisch, Gerd

2004-01-01

During partial liquid ventilation (PLV) the knowledge of the quantity of exhaled perfluorocarbon (PFC) allows a continuous substitution of the PFC loss to achieve a constant PFC level in the lungs. The aim of our in vitro study was to determine the PFC loss in the mixed expired gas by an absorber and to investigate the effect of the evaporated PFC on ventilatory measurements. To simulate the PFC loss during PLV, a heated flask was rinsed with a constant airflow of 4 L min(-1) and PFC was infused by different speeds (5, 10, 20 mL h(-1)). An absorber filled with PFC selective zeolites was connected with the flask to measure the PFC in the gas. The evaporated PFC volume and the PFC concentration were determined from the weight gain of the absorber measured by an electronic scale. The PFC-dependent volume error of the CO2SMO plus neonatal pneumotachograph was measured by manual movements of a syringe with volumes of 10 and 28 mL with a rate of 30 min(-1). Under steady state conditions there was a strong correlation (r2 = 0.999) between the infusion speed of PFC and the calculated PFC flow rate. The PFC flow rate was slightly underestimated by 4.3% (p < 0.01). However, this bias was independent from PFC infusion rate. The evaporated PFC volume was precisely measured with errors < 1%. The volume error of the CO2SMO-Plus pneumotachograph increased with increasing PFC content for both tidal volumes (p < 0.01). However for PFC flow rates up to 20 mL/h the error of the measured tidal volumes was < 5%. PFC selective zeolites can be used to quantify accurately the evaporated PFC volume during PLV. With increasing PFC concentrations in the exhaled air the measurement errors of ventilatory parameters have to be taken into account.

Suspended particulate matter flocculation in a natural tidal wetland located in the San Francisco Estuary

NASA Astrophysics Data System (ADS)

Saraceno, J.; Bergamaschi, B. A.; Wright, S. A.; Boss, E.; Downing, B. D.; Fleck, J.; Ganju, N. K.

2011-12-01

Suspended mineral and algal particles together comprise suspended particulate matter (SPM). The SPM size distribution influences the quantity and color of light penetration and the adsorption and transport of contaminants such as pesticides and metals. It is widely known that interaction with wetlands alters the size distribution and quality of particles through local primary production, differential settling and particle aggregation, however, our understanding of how tidal wetland processes affect SPM quantity and size spectra has been hampered by the difficulty of directly observing these parameters at tidal time scales. To evaluate how SPM concentration and size varied over tidal time scales and to better understand the relationship between organic matter and sediment characteristics, simultaneous measurements of dissolved organic matter, SPM concentration and organic content as well as in situ surrogates of particle concentration (turbidity, particulate attenuation, volume concentration) and particle size (laser diffraction) were carried out with measurements of current velocity (acoustic Doppler velocity meter) in the main channel of Brown's Island located in the western San Joaquin/Sacramento River Delta, CA. The study period coincided with high estuary sediment levels following a significant precipitation runoff event. In the Brown Island wetland, particle concentration and size dynamics were tied to variations in water level and velocity. Turbidity and attenuation covaried with the volume concentration of particles smaller than 33 um, which on average represented greater than 50% of particle population by volume. On average, these SPM concentration surrogates were three times higher in flood water than in ebb water; consistent with a loss of fine particles on the island. Following the highest flood tide, the decrease in fine particles was coincident with an increase in the concentration of particles larger than 130 um; a finding consistent with particle flocculation. Additionally, the timing of flocculation was coincident with periods of elevated dissolved organic matter, suggesting organic matter played a role in the formation of large aggregates. Measurements of SPM organic content in ebb water revealed that SPM was enriched in organic matter by up to 50% following interaction with the wetland. Newly formed aggregates were carried out to the estuary with the ebb tide. These results indicate that the Browns Island wetland (and presumably other similar wetlands throughout the San Francisco Bay-Delta) plays an important role in estuarine biogeochemistry and particle cycling because flocculated particles have higher settling velocities and optical properties than their component particles and will behave differently. The implications of these findings are relevant to several tidal wetland management concerns such as the maintenance of marsh elevation, the cycling and transport of contaminants, and water clarity.

Consequences of Expiratory Flow Limitation at Rest in Subjects with Cystic Fibrosis.

PubMed

Vilozni, Daphna; Lavie, Moran; Ofek, Miryam; Sarouk, Ifat; Bar-Aluma, Bat-El; Dagan, Adi; Ashkenazi, Moshe; Segel, Michael J; Efrati, Ori

2016-06-01

Expiratory flow limitation at resting tidal volume (EFLTV) presents a severe mechanical constraint in chronic lung diseases and has not yet been studied longitudinally in cystic fibrosis. To study the effect of EFLTV as it emerged from simple spirometry on lung function and clinical status in cystic fibrosis. Best year spirometry that included tidal flow/volume curves and the related clinical data were retrospectively collected over 12 ± 3.0 yr/person from 108 subjects with cystic fibrosis. The year in which forced expiratory flow, midexpiratory phase (FEF25-75%, L/s) was equal to tidal peak expiratory flow (L/s) was defined as EFLTV-onset year. EFLTV occurred in 55 (51%) subjects, at age 23 ± 6 years. At EFLTV onset, tidal peak expiratory flow and FEF25-75% values were 1.44 ± 0.23 L/s and FEV1 was 62 ± 10% predicted. Within the following 2 years, FEV1 dropped to 48 ± 11% predicted, and 35 (63%) of the subjects reported shortness of breath at rest. Hospital days increased from 5.3 ± 24.6 to 24.12 ± 9.0 d/yr (P = 0.0001). Of the 55 subjects, 29 (53%) received transplant or died, with survival time being 6.9 ± 3.9 years. EFLTV onset may be an important pathophysiological event that could influence the natural history of lung function decline in subjects with cystic fibrosis. This may lead to a significant deterioration in lung function in the following 2 years alongside an increase in the number of hospitalization days. The monitoring of FEV1 alone does not offer as good a threshold signal, because values are only moderately reduced. Therefore, identifying EFLTV appearance is potentially a signal for therapeutic intervention. Further studies are warranted to confirm our findings.

Modeling tidal hydrodynamics of San Diego Bay, California

USGS Publications Warehouse

Wang, P.-F.; Cheng, R.T.; Richter, K.; Gross, E.S.; Sutton, D.; Gartner, J.W.

1998-01-01

In 1983, current data were collected by the National Oceanic and Atmospheric Administration using mechanical current meters. During 1992 through 1996, acoustic Doppler current profilers as well as mechanical current meters and tide gauges were used. These measurements not only document tides and tidal currents in San Diego Bay, but also provide independent data sets for model calibration and verification. A high resolution (100-m grid), depth-averaged, numerical hydrodynamic model has been implemented for San Diego Bay to describe essential tidal hydrodynamic processes in the bay. The model is calibrated using the 1983 data set and verified using the more recent 1992-1996 data. Discrepancies between model predictions and field data in beth model calibration and verification are on the order of the magnitude of uncertainties in the field data. The calibrated and verified numerical model has been used to quantify residence time and dilution and flushing of contaminant effluent into San Diego Bay. Furthermore, the numerical model has become an important research tool in ongoing hydrodynamic and water quality studies and in guiding future field data collection programs.

The effects of intraoperative lung protective ventilation with positive end-expiratory pressure on blood loss during hepatic resection surgery: A secondary analysis of data from a published randomised control trial (IMPROVE).

PubMed

Neuschwander, Arthur; Futier, Emmanuel; Jaber, Samir; Pereira, Bruno; Eurin, Mathilde; Marret, Emmanuel; Szymkewicz, Olga; Beaussier, Marc; Paugam-Burtz, Catherine

2016-04-01

During high-risk abdominal surgery the use of a multi-faceted lung protective ventilation strategy composed of low tidal volumes, positive end-expiratory pressure (PEEP) and recruitment manoeuvres, has been shown to improve clinical outcomes. It has been speculated, however, that mechanical ventilation using PEEP might increase intraoperative bleeding during liver resection. To study the impact of mechanical ventilation with PEEP on bleeding during hepatectomy. Post-hoc analysis of a randomised controlled trial. Seven French university teaching hospitals from January 2011 to August 2012. Patients scheduled for liver resection surgery. In the Intraoperative Protective Ventilation trial, patients scheduled for major abdominal surgery were randomly assigned to mechanical ventilation using low tidal volume, PEEP between 6 and 8  cmH2O and recruitment manoeuvres (lung protective ventilation strategy) or higher tidal volume, zero PEEP and no recruitment manoeuvres (non-protective ventilation strategy). The primary endpoint was intraoperative blood loss volume. A total of 79 (19.8%) patients underwent liver resections (41 in the lung protective and 38 in the non-protective group). The median (interquartile range) amount of intraoperative blood loss was 500 (200 to 800)  ml and 275 (125 to 800)  ml in the non-protective and lung protective ventilation groups, respectively (P = 0.47). Fourteen (35.0%) and eight (21.5%) patients were transfused in the non-protective and lung protective groups, respectively (P = 0.17), without a statistically significant difference in the median (interquartile range) number of red blood cells units transfused [2.5 (2 to 4) units and 3 (2 to 6) units in the two groups, respectively; P = 0.54]. During hepatic surgery, mechanical ventilation using PEEP within a multi-faceted lung protective strategy was not associated with increased bleeding compared with non-protective ventilation using zero PEEP. The current study was not registered. The original Intraoperative Protective Ventilation study was registered on clinicaltrials.gov; number NCT01282996.

Susceptibility to ventilator induced lung injury is increased in senescent rats

PubMed Central

2013-01-01

Introduction The principal mechanisms of ventilator induced lung injury (VILI) have been investigated in numerous animal studies. However, prospective data on the effect of old age on VILI are limited. Under the hypothesis that susceptibility to VILI is increased in old age, we investigated the pulmonary and extrapulmonary effects of mechanical ventilation with high tidal volume (VT) in old compared to young adult animals. Interventions Old (19.1 ± 3.0 months) and young adult (4.4 ± 1.3 months) male Wistar rats were anesthetized and mechanically ventilated (positive end-expiratory pressure 5 cmH2O, fraction of inspired oxygen 0.4, respiratory rate 40/minute) with a tidal volume (VT) of either 8, 16 or 24 ml/kg for four hours. Respiratory and hemodynamic variables, including cardiac output, and markers of systemic inflammation were recorded throughout the ventilation period. Lung histology and wet-to-dry weight ratio, injury markers in lung lavage and respiratory system pressure-volume curves were assessed post mortem. Basic pulmonary characteristics were assessed in non-ventilated animals. Results Compared to young adult animals, high VT (24 ml/kg body weight) caused more lung injury in old animals as indicated by decreased oxygenation (arterial oxygen tension (PaO2): 208 ± 3 vs. 131 ± 20 mmHg; P <0.05), increased lung wet-to-dry-weight ratio (5.61 ± 0.29 vs. 7.52 ± 0.27; P <0.05), lung lavage protein (206 ± 52 mg/l vs. 1,432 ± 101; P <0.05) and cytokine (IL-6: 856 ± 448 vs. 3,283 ± 943 pg/ml; P <0.05) concentration. In addition, old animals ventilated with high VT had more systemic inflammation than young animals (IL-1β: 149 ± 44 vs. 272 ± 36 pg/ml; P <0.05 - young vs. old, respectively). Conclusions Ventilation with unphysiologically large tidal volumes is associated with more lung injury in old compared to young rats. Aggravated pulmonary and systemic inflammation is a key finding in old animals developing VILI. PMID:23710684

Fidelity of life and death molluscan assemblages from carbonate tidal flats in the Persian (Arabian) Gulf

NASA Astrophysics Data System (ADS)

García-Ramos, Diego A.; Albano, Paolo G.; Harzhauser, Mathias; Piller, Werner E.; Zuschin, Martin

2016-04-01

Live-dead (LD) studies aim to help understand how faithfully fossil assemblages can be used to quantitatively infer the structure of the original living communities that generated them. To this purpose, LD comparisons have been conducted in different terrestrial and aquatic environments to assess how environment-specific differences in quality and intensity of taphonomic factors affect LD fidelity. In sub-tropical and tropical settings, most LD studies have focused on hard substrates or seagrass bottoms. Here we present results on molluscan assemblages from soft carbonate sediments in tidal flats of the Persian (Arabian) Gulf (Indo-West Pacific biogeographic province). We analyzed a total of 7193 mollusks collected from six sites comprising time-averaged death assemblages (DAs) and snapshot living assemblages (LAs). All analyses were performed at site and at habitat scales after correcting for sample-size differences. We found a good match in proportional abundance and a notable mismatch in species composition. In fact, species richness in DAs is 6 times larger than in LAs at site scale, and 4 times at habitat scale. Additionally, we found a good fidelity of evenness, and rank abundance of feeding guilds. Other studies have shown that molluscan DAs from subtidal carbonate environments can display lower time-averaging than those from siliciclastic environments due to high rates of shell loss to bioerosion and dissolution. For our case study of tidal flat carbonate settings, we interpret that despite temporal autocorrelation (good fidelity of proportional abundance), substantial differences in species richness and composition can be explained by early cementation, lateral mixing, intense bioturbation and moderate sedimentation rates. Our results suggest that tidal flat carbonate environments can potentially lead to a wider window of time-averaging in comparison with subtidal carbonate settings.

Tidal River Elbe - a sediment budget for the grain size fraction of medium sand

NASA Astrophysics Data System (ADS)

Winterscheid, Axel

2016-04-01

Human interventions have a historic and ongoing impact on estuarine sediment budgets across many estuaries worldwide. An early inference was the construction of embankments resulting in a constant loss of intertidal flats. Additionally, settlement activities and large scale land use changes in the upstream catchment areas had also an effect on sediment inflow rates. Today, the navigation channels in estuaries have been deepened for larger and more efficient vessels to reach a well-developed infrastructure of harbors and industrial areas often located far inland. In the past few years and just within the North-East Atlantic, the total annual amount of dredged sediments dumped at sea varied from 80 to 130 million tons (OSPAR Commission). In most estuaries across Europe the resulting human impact on the sediment fluxes and morphodynamics is significant. A good understanding of estuarine processes is essential for determining useful and meaningful measures to mitigate negative effects and to improve the current situation. Maintenance dredging and its environmental effects are therefore in the focus of public attention. Against this background, it is the aim of the presentation to identify and therefore to separate the particular effect that maintenance dredging has on sediment fluxes and budgets in the estuarine environment. Case study is the Tidal River Elbe in Germany, and here we set the focus on the grain size fraction of medium sand. In the past, river engineering measures forced the natural dynamics to form a concentrated stream flow along a fixed channel, except at a number of locations where side channels still exist. In addition to that, the main channel was deepened several times. The last deepening was in 1999/2000. The most significant deepening, however, took place from 1957 to 1962. Until then, an erosion-stable layer of marine clay (in German called "Klei") formed a flat bottom along most sections of the main channel. After removal of this layer of marine clay by capital dredging, Weichselion sandy deposits, which formed the geological layer underneath, now became part of the sediment transport regime. Nowadays, most sections of the main channel are morphologically characterized by a medium sandy river bed and subaquatic dunes of several meters height followed by sections of a poorly structured river bed caused by the sedimentation of silty sediments. By setting up the sediment balance for medium sand, the fluxes entering the estuary from the inland Elbe is one source term in the equation. The average annual load for the medium sand is estimated to be 110,000 m³/year (1996 - 2008, measurement station Neu Darchau). Further downstream in the tidal part of the river there are no further measurement stations located, but the analysis of a time series of multibeam sonar data (2000 to 2014) shows that large amounts of medium sand episodically pass the tidal weir at Geesthacht only in the event of extreme flood. This is due to a significant increase in bed volume between Geesthacht and the Port of Hamburg in the aftermath of a singular extreme event. Until the next extreme event the bed volume (functions as temporary storage for medium sand) is eroding again, which is the second source term. By comparing the information on bed load fluxes, the evolution of bed volumes over time and the dredging statistics we can conclude for the longer term that the total amount of medium sand that has been dredged and taken out of the system for constructional purposes is the same order of magnitude compared to the sum of both source terms. Hence, there is no or very limited net transport of medium sand passing the port area and entering the downstream river section. From the subsequent analysis of multibeam sonar data (2008 - 2014) we know for the river section from Hamburg to Brunsbuettel (total distance of 40 km) that there has been a continuous loss of about 1 Mio. m³/a in bed volumes, which means a deficit situation for medium sand. Currently, the Weichselion deposit is the active source for medium sand, but due to the lack of medium sand fluxes from upstream this at the cost of having an ongoing deepening of the main channel. The presumed cause for this deficit situation is the current management of the sandy dredged material. First of all, dredging and subsequent extraction of the dredged material is strongly affecting the longitudinal transport of medium sandy sediments from upstream through the Port of Hamburg in seaward direction. Further downstream in the river section in deficit, all dredged material, which is about 1 Mio m³/a solely for the fraction of medium sand, is transported by hopper dredgers over a long distance up to 40 km in seaward direction and disposed on a single site near Brunsbuettel. This 1 Mio m³/a is a similar volume in comparison to the loss in bed volume. From an analysis of the geometry of the subaquatic dunes we know for sandy sediments a seaward net transport that exists for large parts of this river section. All in one, there is an irretrievable and ongoing loss of medium sandy sediments. Vice versa for the river section next to Brunsbuettel, which is the location of the disposal site, the data show an increase of bed volumes and dredging amounts at the same time. For the Elbe case study we could demonstrate that maintenance dredging (and the subsequent disposal) could have a significant impact on the large scale sediment budget. Appropriate measures to stabilize the sediment budget in the inner part of the Tidal River Elbe for medium sand is (a) to dispose all medium sandy dredged material as close as possible to the location of dredging and (b) to reduce the extraction of medium sand in the Hamburg Port area.

A Global Ocean Tide Model From TOPEX/POSEIDON Altimetry: GOT99.2

NASA Technical Reports Server (NTRS)

Ray, Richard D.

1999-01-01

Goddard Ocean Tide model GOT99.2 is a new solution for the amplitudes and phases of the global oceanic tides, based on over six years of sea-surface height measurements by the TOPEX/POSEIDON satellite altimeter. Comparison with deep-ocean tide-gauge measurements show that this new tidal solution is an improvement over previous global models, with accuracies for the main semidiurnal lunar constituent M2 now below 1.5 cm (deep water only). The new solution benefits from use of prior hydrodynamic models, several in shallow and inland seas as well as the global finite-element model FES94.1. This report describes some of the data processing details involved in handling the altimetry, and it provides a comprehensive set of global cotidal charts of the resulting solutions. Various derived tidal charts are also provided, including tidal loading deformation charts, tidal gravimetric charts, and tidal current velocity (or transport) charts. Finally, low-degree spherical harmonic coefficients are computed by numerical quadrature and are tabulated for the major short-period tides; these are useful for a variety of geodetic and geophysical purposes, especially in combination with similar estimates from satellite laser ranging.

Influence of changes in hydrodynamic conditions on cadmium transport in tidal river network of the Pearl River Delta, China.

PubMed

Dou, Ming; Zuo, Qiting; Zhang, Jinping; Li, Congying; Li, Guiqiu

2013-09-01

With rapid economic development, the Pearl River Delta (PRD) of China has experienced a series of serious heavy metal pollution events. Considering complex hydrodynamic and pollutants transport process, one-dimensional hydrodynamic model and heavy metal transport model were developed for tidal river network of the PRD. Then, several pollution emergency scenarios were designed by combining with the upper inflow, water quality and the lower tide level boundary conditions. Using this set of models, the temporal and spatial change process of cadmium (Cd) concentration was simulated. The influence of change in hydrodynamic conditions on Cd transport in tidal river network was assessed, and its transport laws were summarized. The result showed the following: Flow changes in the tidal river network were influenced remarkably by tidal backwater action, which further influenced the transport process of heavy metals; Cd concentrations in most sections while encountering high tide were far greater than those while encountering middle or low tides; and increased inflows from upper reaches could intensify water pollution in the West River (while encountering high tide) or the North River (while encountering middle or low tides).

[Airway Obstruction Caused by Heat and Moisture Exchange Filter Used during General Anesthesia: A Case Report and an In Vitro Study].

PubMed

Yoshidome, Aya; Shinomiya, Ayako; Iwagaki, Tamao; Sano, Haruhiko; Aoyama, Kazuyoshi; Takenaka, Yukari; Takenaka, Ichiro

2015-08-01

A previously healthy 54-year-old woman underwent a resection of the acoustic tumor. Following induction of general anesthesia and tracheal intubation, volume-controlled ventilation was started and the patient was placed in the left park bench position. The heat and moisture exchange filter (HMEF) was placed within the ventilatory circuit and positioned below the patient's head to avoid unintentional extubation. Six hours after the start of surgery, peak inspiratory pressure gradually rose, and 2 hours later ventilation of the patient's lung became increasingly difficult. When the HMEF was replaced, normal breathing was promptly restored. We reproduced this scenario with a similar HMEF under the same ventilator settings by adding 0-8 g of normal saline into the HMEF housing, and measured the inspiratory pressure and tidal volume across the HMEF. When instilling 4 g of saline, an increase in inspiratory pressure occurred. This case shows a potential risk of unexpectedly early occurrence of obstruction of the HMEF due to accumulation of condensed water within the device when the HMEF was positioned below the patient's head. We recommend selection of the appropriate HMEF and suitable mounting to avoid this problem.

Comparison of different functional EIT approaches to quantify tidal ventilation distribution.

PubMed

Zhao, Zhanqi; Yun, Po-Jen; Kuo, Yen-Liang; Fu, Feng; Dai, Meng; Frerichs, Inez; Möller, Knut

2018-01-30

The aim of the study was to examine the pros and cons of different types of functional EIT (fEIT) to quantify tidal ventilation distribution in a clinical setting. fEIT images were calculated with (1) standard deviation of pixel time curve, (2) regression coefficients of global and local impedance time curves, or (3) mean tidal variations. To characterize temporal heterogeneity of tidal ventilation distribution, another fEIT image of pixel inspiration times is also proposed. fEIT-regression is very robust to signals with different phase information. When the respiratory signal should be distinguished from the heart-beat related signal, or during high-frequency oscillatory ventilation, fEIT-regression is superior to other types. fEIT-tidal variation is the most stable image type regarding the baseline shift. We recommend using this type of fEIT image for preliminary evaluation of the acquired EIT data. However, all these fEITs would be misleading in their assessment of ventilation distribution in the presence of temporal heterogeneity. The analysis software provided by the currently available commercial EIT equipment only offers either fEIT of standard deviation or tidal variation. Considering the pros and cons of each fEIT type, we recommend embedding more types into the analysis software to allow the physicians dealing with more complex clinical applications with on-line EIT measurements.

Preliminary assessment of channel stability and bed-material transport in the Tillamook Bay tributaries and Nehalem River basin, northwestern Oregon

USGS Publications Warehouse

Jones, Krista L.; Keith, Mackenzie K.; O'Connor, Jim E.; Mangano, Joseph F.; Wallick, J. Rose

2012-01-01

This report summarizes a preliminary study of bed-material transport, vertical and lateral channel changes, and existing datasets for the Tillamook (drainage area 156 square kilometers [km2]), Trask (451 km2), Wilson (500 km2), Kilchis (169 km2), Miami (94 km2), and Nehalem (2,207 km2) Rivers along the northwestern Oregon coast. This study, conducted in coopera-tion with the U.S. Army Corps of Engineers and Oregon Department of State Lands to inform permitting decisions regarding instream gravel mining, revealed that: * Study areas along the six rivers can be divided into reaches based on tidal influence and topography. The fluvial (nontidal or dominated by riverine processes) reaches vary in length (2.4-9.3 kilometer [km]), gradient (0.0011-0.0075 meter of elevation change per meter of channel length [m/m]), and bed-material composition (a mixture of alluvium and intermittent bedrock outcrops to predominately alluvium). In fluvial reaches, unit bar area (square meter of bar area per meter of channel length [m2/m]) as mapped from 2009 photographs ranged from 7.1 m2/m on the Tillamook River to 27.9 m2/m on the Miami River. * In tidal reaches, all six rivers flow over alluvial deposits, but have varying gradients (0.0001-0.0013 m/m) and lengths affected by tide (1.3-24.6 km). The Miami River has the steepest and shortest tidal reach and the Nehalem River has the flattest and longest tidal reach. Bars in the tidal reaches are generally composed of sand and mud. Unit bar area was greatest in the Tidal Nehalem Reach, where extensive mud flats flank the lower channel. * Background factors such as valley and channel confinement, basin geology, channel slope, and tidal extent control the spatial variation in the accumulation and texture of bed material. Presently, the Upper Fluvial Wilson and Miami Reaches and Fluvial Nehalem Reach have the greatest abundance of gravel bars, likely owing to local bed-material sources in combination with decreasing channel gradient and valley confinement. * Natural and human-caused disturbances such as mass movements, logging, fire, channel modifications for navigation and flood control, and gravel mining also have varying effects on channel condition, bed-material transport, and distribution and area of bars throughout the study areas and over time. * Existing datasets include at least 16 and 18 sets of aerial and orthophotographs that were taken of the study areas in the Tillamook Bay tributary basins and Nehalem River basin, respectively, from 1939 to 2011. These photographs are available for future assessments of long-term changes in channel condition, bar area, and vegetation establishment patterns. High resolution Light Detection And Ranging (LiDAR) surveys acquired in 2007-2009 could support future quantitative analyses of channel morphology and bed-material transport in all study areas. * A review of deposited and mined gravel volumes reported for instream gravel mining sites shows that bed-material deposition tends to rebuild mined bar surfaces in most years. Mean annual deposition volumes on individual bars exceeded 3,000 cubic meters (m3) on Donaldson Bar on the Wilson River, Dill Bar on the Kilchis River, and Plant and Winslow Bars on the Nehalem River. Cumulative reported volumes of bed-material deposition were greatest at Donaldson and Dill Bars, totaling over 25,000 m3 per site from 2004 to 2011. Within this period, reported cumulative mined volumes were greatest for the Donaldson, Plant, and Winslow Bars, ranging from 24,470 to 33,940 m3. * Analysis of historical stage-streamflow data collected by the U.S. Geological Survey on the Wilson River near Tillamook (14301500) and Nehalem River near Foss (14301000) shows that these rivers have episodically aggraded and incised, mostly following high flow events, but they do not exhibit systematic, long-term trends in bed elevation. * Multiple cross sections show that channels near bridge crossings in all six study areas are dynamic with many subject to incision and aggradation as well as lateral shifts in thalweg position and bank deposition and erosion. * In fluvial reaches, unit bar area declined a net 5.3-83.6 percent from 1939 to 2009. The documented reduction in bar area may be attributable to several factors, including vegetation establishment and stabilization of formerly active bar surfaces, lateral channel changes and resulting alterations in sediment deposition and erosion patterns, and streamflow and/or tide differences between photographs. Other factors that may be associated with the observed reduction in bar area but not assessed in this reconnaissance level study include changes in the sediment and hydrology regimes of these rivers over the analysis period. * In tidal reaches, unit bar area increased on the Tillamook and Nehalem Rivers (98.0 and 14.7 percent, respectively), but declined a net 24.2 to 83.1 percent in the other four tidal reaches. Net increases in bar area in the Tidal Tillamook and Nehalem Reaches were possibly attributable to tidal differences between the photographs as well as sediment deposition behind log booms and pile structures on the Tillamook River between 1939 and 1967. * The armoring ratio (ratio of the median grain sizes of a bar's surface and subsurface layers) was 1.6 at Lower Waldron Bar on the Miami River, tentatively indicating a relative balance between transport capacity and sediment supply at this location. Armoring ratios, however, ranged from 2.4 to 5.5 at sites on the Trask, Wilson, Kilchis, and Nehalem Rivers; these coarse armor layers probably reflect limited bed-material supply at these sites. * On the basis of mapping results, measured armoring ratios, and channel cross section surveys, preliminary conclusions are that the fluvial reaches on the Tillamook, Trask, Kilchis, and Nehalem Rivers are currently sediment supply-limited in terms of bed material - that is, the transport capacity of the channel generally exceeds the supply of bed material. The relation between transport capacity and sediment is more ambiguous for the fluvial reaches on the Wilson and Miami Rivers, but transport-limited conditions are likely for at least parts of these reaches. Some of these reaches have possibly evolved from sediment supply-limited to transport-limited over the last several decades in response to changing basin and climate conditions. * Because of exceedingly low gradients, all the tidal reaches are transport-limited. Bed material in these reaches, however, is primarily sand and finer grain-size material and probably transported as suspended load from upstream reaches. These reaches will be most susceptible to watershed conditions affecting the supply and transport of fine sediment. * Compared to basins on the southwestern Oregon coast, such as the Chetco and Rogue River basins, these six basins likely transport overall less gravel bed material. Although tentative in the absence of actual transport measurements, this conclusion is supported by the much lower area and frequency of bars and longer tidal reaches along all the northcoast rivers examined in this study. * Previous studies suggest that the expansive and largely unvegetated bars visible in the 1939 photographs are primarily associated with voluminous sedimentation starting soon after the first Tillamook Burn fire in 1933. However, USGS studies of temporal bar trends in other Oregon coastal rivers unaffected by the Tillamook Burn show similar declines in bar area over approximately the same analysis period. In the Umpqua and Chetco River basins, historical declines in bar area are associated with long-term decreases in flood magnitude. Other factors may include changes in the type and volume of large wood and riparian vegetation. Further characterization of hydrology patterns in these basins and possible linkages with climate factors related to flood peaks, such as the Pacific Decadal Oscillation, could support inferences of expected future changes in vegetation establishment and channel planform and profile. * More detailed investigations of bed-material transport rates and channel morphology would support assessments of lateral and vertical channel condition and longitudinal trends in bed material. Such assessments would be most practical for the fluvial study areas on the Wilson, Kilchis, Miami, and Nehalem Rivers and relevant to several ongoing management and ecological issues pertaining to sand and gravel transport. Tidal reaches may also be logical subjects for indepth analysis where studies would be more relevant to the deposition and transport of fine sediment (and associated channel and riparian conditions and processes) rather than coarse bed material.

The effect of lung deformation on the spatial distribution of pulmonary blood flow.

PubMed

Arai, Tatsuya J; Theilmann, Rebecca J; Sá, Rui Carlos; Villongco, Michael T; Hopkins, Susan R

2016-11-01

Pulmonary perfusion measurement using magnetic resonance imaging combined with deformable image registration enabled us to quantify the change in the spatial distribution of pulmonary perfusion at different lung volumes. The current study elucidated the effects of tidal volume lung inflation [functional residual capacity (FRC) + 500 ml and FRC + 1 litre] on the change in pulmonary perfusion distribution. Changes in hydrostatic pressure distribution as well as transmural pressure distribution due to the change in lung height with tidal volume inflation are probably bigger contributors to the redistribution of pulmonary perfusion than the changes in pulmonary vasculature resistance caused by lung tissue stretch. Tidal volume lung inflation results in structural changes in the pulmonary circulation, potentially affecting pulmonary perfusion. We hypothesized that perfusion is recruited to regions receiving the greatest deformation from a tidal breath, thus ensuring ventilation-perfusion matching. Density-normalized perfusion (DNP) magnetic resonance imaging data were obtained in healthy subjects (n = 7) in the right lung at functional residual capacity (FRC), FRC+500 ml, and FRC+1.0 l. Using deformable image registration, the displacement of a sagittal lung slice acquired at FRC to the larger volumes was calculated. Registered DNP images were normalized by the mean to estimate perfusion redistribution (nDNP). Data were evaluated across gravitational regions (dependent, middle, non-dependent) and by lobes (upper, RUL; middle, RML; lower, RLL). Lung inflation did not alter mean DNP within the slice (P = 0.10). The greatest expansion was seen in the dependent region (P < 0.0001: dependent vs non-dependent, P < 0.0001: dependent vs middle) and RLL (P = 0.0015: RLL vs RUL, P < 0.0001: RLL vs RML). Neither nDNP recruitment to RLL [+500 ml = -0.047(0.145), +1 litre = 0.018(0.096)] nor to dependent lung [+500 ml = -0.058(0.126), +1 litre = -0.023(0.106)] were found. Instead, redistribution was seen in decreased nDNP in the non-dependent [+500 ml = -0.075(0.152), +1 litre = -0.137(0.167)) and increased nDNP in the gravitational middle lung [+500 ml = 0.098(0.058), +1 litre = 0.093(0.081)] (P = 0.01). However, there was no significant lobar redistribution (P < 0.89). Contrary to our hypothesis, based on the comparison between gravitational and lobar perfusion data, perfusion was not redistributed to the regions of the most inflation. This suggests that either changes in hydrostatic pressure or transmural pressure distribution in the gravitational direction are implicated in the redistribution of perfusion away from the non-dependent lung. © 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.

The effect of lung deformation on the spatial distribution of pulmonary blood flow

PubMed Central

Arai, Tatsuya J.; Theilmann, Rebecca J.; Sá, Rui Carlos; Villongco, Michael T.

2016-01-01

Key points Pulmonary perfusion measurement using magnetic resonance imaging combined with deformable image registration enabled us to quantify the change in the spatial distribution of pulmonary perfusion at different lung volumes.The current study elucidated the effects of tidal volume lung inflation [functional residual capacity (FRC) + 500 ml and FRC + 1 litre] on the change in pulmonary perfusion distribution.Changes in hydrostatic pressure distribution as well as transmural pressure distribution due to the change in lung height with tidal volume inflation are probably bigger contributors to the redistribution of pulmonary perfusion than the changes in pulmonary vasculature resistance caused by lung tissue stretch. Abstract Tidal volume lung inflation results in structural changes in the pulmonary circulation, potentially affecting pulmonary perfusion. We hypothesized that perfusion is recruited to regions receiving the greatest deformation from a tidal breath, thus ensuring ventilation–perfusion matching. Density‐normalized perfusion (DNP) magnetic resonance imaging data were obtained in healthy subjects (n = 7) in the right lung at functional residual capacity (FRC), FRC+500 ml, and FRC+1.0 l. Using deformable image registration, the displacement of a sagittal lung slice acquired at FRC to the larger volumes was calculated. Registered DNP images were normalized by the mean to estimate perfusion redistribution (nDNP). Data were evaluated across gravitational regions (dependent, middle, non‐dependent) and by lobes (upper, RUL; middle, RML; lower, RLL). Lung inflation did not alter mean DNP within the slice (P = 0.10). The greatest expansion was seen in the dependent region (P < 0.0001: dependent vs non‐dependent, P < 0.0001: dependent vs middle) and RLL (P = 0.0015: RLL vs RUL, P < 0.0001: RLL vs RML). Neither nDNP recruitment to RLL [+500 ml = −0.047(0.145), +1 litre = 0.018(0.096)] nor to dependent lung [+500 ml = −0.058(0.126), +1 litre = −0.023(0.106)] were found. Instead, redistribution was seen in decreased nDNP in the non‐dependent [+500 ml = −0.075(0.152), +1 litre = −0.137(0.167)) and increased nDNP in the gravitational middle lung [+500 ml = 0.098(0.058), +1 litre = 0.093(0.081)] (P = 0.01). However, there was no significant lobar redistribution (P < 0.89). Contrary to our hypothesis, based on the comparison between gravitational and lobar perfusion data, perfusion was not redistributed to the regions of the most inflation. This suggests that either changes in hydrostatic pressure or transmural pressure distribution in the gravitational direction are implicated in the redistribution of perfusion away from the non‐dependent lung. PMID:27273807

Graph-based retrospective 4D image construction from free-breathing MRI slice acquisitions

NASA Astrophysics Data System (ADS)

Tong, Yubing; Udupa, Jayaram K.; Ciesielski, Krzysztof C.; McDonough, Joseph M.; Mong, Andrew; Campbell, Robert M.

2014-03-01

4D or dynamic imaging of the thorax has many potential applications [1, 2]. CT and MRI offer sufficient speed to acquire motion information via 4D imaging. However they have different constraints and requirements. For both modalities both prospective and retrospective respiratory gating and tracking techniques have been developed [3, 4]. For pediatric imaging, x-ray radiation becomes a primary concern and MRI remains as the de facto choice. The pediatric subjects we deal with often suffer from extreme malformations of their chest wall, diaphragm, and/or spine, as such patient cooperation needed by some of the gating and tracking techniques are difficult to realize without causing patient discomfort. Moreover, we are interested in the mechanical function of their thorax in its natural form in tidal breathing. Therefore free-breathing MRI acquisition is the ideal modality of imaging for these patients. In our set up, for each coronal (or sagittal) slice position, slice images are acquired at a rate of about 200-300 ms/slice over several natural breathing cycles. This produces typically several thousands of slices which contain both the anatomic and dynamic information. However, it is not trivial to form a consistent and well defined 4D volume from these data. In this paper, we present a novel graph-based combinatorial optimization solution for constructing the best possible 4D scene from such data entirely in the digital domain. Our proposed method is purely image-based and does not need breath holding or any external surrogates or instruments to record respiratory motion or tidal volume. Both adult and children patients' data are used to illustrate the performance of the proposed method. Experimental results show that the reconstructed 4D scenes are smooth and consistent spatially and temporally, agreeing with known shape and motion of the lungs.

Upper Airway Collapsibility During REM Sleep in Children with the Obstructive Sleep Apnea Syndrome

PubMed Central

Huang, Jingtao; Karamessinis, Laurie R.; Pepe, Michelle E.; Glinka, Stephen M.; Samuel, John M.; Gallagher, Paul R.; Marcus, Carole L.

2009-01-01

Study Objectives: In children, most obstructive events occur during rapid eye movement (REM) sleep. We hypothesized that children with the obstructive sleep apnea syndrome (OSAS), in contrast to age-matched control subjects, would not maintain airflow in the face of an upper airway inspiratory pressure drop during REM sleep. Design: During slow wave sleep (SWS) and REM sleep, we measured airflow, inspiratory time, inspiratory time/total respiratory cycle time, respiratory rate, tidal volume, and minute ventilation at a holding pressure at which flow limitation occurred and at 5 cm H2O below the holding pressure in children with OSAS and in control subjects. Setting: Sleep laboratory. Participants: Fourteen children with OSAS and 23 normal control subjects. Results: In both sleep states, control subjects were able to maintain airflow, whereas subjects with OSAS preserved airflow in SWS but had a significant decrease in airflow during REM sleep (change in airflow of 18.58 ± 12.41 mL/s for control subjects vs −44.33 ± 14.09 mL/s for children with OSAS, P = 0.002). Although tidal volume decreased, patients with OSAS were able to maintain minute ventilation by increasing the respiratory rate and also had an increase in inspiratory time and inspiratory time per total respiratory cycle time Conclusion: Children with OSAS do not maintain airflow in the face of upper-airway inspiratory-pressure drops during REM sleep, indicating a more collapsible upper airway, compared with that of control subjects during REM sleep. However, compensatory mechanisms exist to maintain minute ventilation. Local reflexes, central control mechanisms, or both reflexes and control mechanisms need to be further explored to better understand the pathophysiology of this abnormality and the compensation mechanism. Citation: Huang J; Karamessinis LR; Pepe ME; Glinka SM; Samuel JM; Gallagher PR; Marcus CL. Upper airway collapsibility during REM sleep in children with the obstructive sleep apnea syndrome. SLEEP 2009;32(9):1173-1181. PMID:19750922

Development of real time abdominal compression force monitoring and visual biofeedback system

NASA Astrophysics Data System (ADS)

Kim, Tae-Ho; Kim, Siyong; Kim, Dong-Su; Kang, Seong-Hee; Cho, Min-Seok; Kim, Kyeong-Hyeon; Shin, Dong-Seok; Suh, Tae-Suk

2018-03-01

In this study, we developed and evaluated a system that could monitor abdominal compression force (ACF) in real time and provide a surrogating signal, even under abdominal compression. The system could also provide visual-biofeedback (VBF). The real-time ACF monitoring system developed consists of an abdominal compression device, an ACF monitoring unit and a control system including an in-house ACF management program. We anticipated that ACF variation information caused by respiratory abdominal motion could be used as a respiratory surrogate signal. Four volunteers participated in this test to obtain correlation coefficients between ACF variation and tidal volumes. A simulation study with another group of six volunteers was performed to evaluate the feasibility of the proposed system. In the simulation, we investigated the reproducibility of the compression setup and proposed a further enhanced shallow breathing (ESB) technique using VBF by intentionally reducing the amplitude of the breathing range under abdominal compression. The correlation coefficient between the ACF variation caused by the respiratory abdominal motion and the tidal volume signal for each volunteer was evaluated and R 2 values ranged from 0.79 to 0.84. The ACF variation was similar to a respiratory pattern and slight variations of ACF ranges were observed among sessions. About 73-77% average ACF control rate (i.e. compliance) over five trials was observed in all volunteer subjects except one (64%) when there was no VBF. The targeted ACF range was intentionally reduced to achieve ESB for VBF simulation. With VBF, in spite of the reduced target range, overall ACF control rate improved by about 20% in all volunteers except one (4%), demonstrating the effectiveness of VBF. The developed monitoring system could help reduce the inter-fraction ACF set up error and the intra fraction ACF variation. With the capability of providing a real time surrogating signal and VBF under compression, it could improve the quality of respiratory tumor motion management in abdominal compression radiation therapy.

A pilot study to examine the effect of the Tulip oropharyngeal airway on ventilation immediately after mask ventilation following the induction of anaesthesia.

PubMed

Robinson, P N; Shaikh, A; Sabir, N M; Vaughan, D J A; Kynoch, M; Hasan, M

2014-07-01

The Tulip airway is an adult, disposable, single-sized oropharyngeal airway, that is connectable to an anaesthetic circuit. After a standardised induction of anaesthesia in 75 patients, the ease of insertion, intracuff pressure and intracuff volume were measured, as were the end-tidal carbon dioxide levels, airway pressures and tidal volumes over three breaths. Successful first-time insertion was achieved in 72 patients (96%, CI 88.8-99.2%) and after two attempts in 74 patients (99%, CI 92.8-100%). There was outright failure only in one patient. In 60 patients (80%, CI 72.2-90.4%), the Tulip airway provided a patent airway without additional manoeuvres, but in 14 patients, jaw thrust or head extension was necessary for airway patency. The main need for these adjuncts appeared to be an initial under-inflation of the cuff. These promising results are consistent with recent manikin studies using this device. © 2014 The Association of Anaesthetists of Great Britain and Ireland.

Effects of mechanical ventilation on gene expression profiles in renal allografts from brain dead rats.

PubMed

Hottenrott, Maximilia C; Krebs, Joerg; Pelosi, Paolo; Luecke, Thomas; Rocco, Patricia R M; Sticht, Carsten; Breedijk, Annette; Yard, Benito; Tsagogiorgas, Charalambos

2017-12-01

Pathophysiological changes of brain death (BD) are impairing distal organ function and harming potential renal allografts. Whether ventilation strategies influence the quality of renal allografts from BD donors has not been thoroughly studied. 28 adult male Wistar rats were randomly assigned to four groups: 1) no brain death (NBD) with low tidal volume/low positive endexpiratory pressure (PEEP) titrated to minimal static elastance of the respiratory system (LVT/OLPEEP); 2) NBD with high tidal volume/low PEEP (HVT/LPEEP); 3) brain death (BD) with LVT/OLPEEP; and 4) BD with HVT/LPEEP. We hypothesized that HVT/LPEEP in BD leads to increased interleukin 6 (IL-6) gene expression and impairs potential renal allografts after six hours of mechanical ventilation. We assessed inflammatory cytokines in serum, genome wide gene expression profiles and quantitative PCR (qPCR) in kidney tissue. The influence of BD on renal gene-expression profiles was greater than the influence of the ventilation strategy. In BD, LVT ventilation did not influence the inflammatory parameters or kidney function in our experimental model. Copyright © 2017. Published by Elsevier B.V.

The nucleus reticularis gigantocellularis modulates the cardiopulmonary responses to central and peripheral drives related to exercise.

PubMed

Richard, C A; Waldrop, T G; Bauer, R M; Mitchell, J H; Stremel, R W

1989-03-13

It is known that muscle afferents and the hypothalamic locomotor region (HLR) both project to the nucleus reticularis gigantocellularis (NGC) and that the NGC is capable of influencing cardiovascular and respiratory variables. Therefore, the role of NGC in the cardiovascular and respiratory response to exercise-related signals was investigated in anesthetized cats. These signals were generated by stimulation of: (1) spinal ventral roots to induce hindlimb muscle contraction (MC) and (2) the HLR. Bilateral electrolytic lesion of the NGC at the pontomedullary border caused tidal volume, respiratory frequency and heart rate responses to HLR stimulation to be greater than the responses recorded prior to lesioning. Lesioning had no effect on the ventilatory or cardiovascular responses to MC but did decrease phrenic responsiveness; lesion had no effect on any resting values. In this preparation, the pontomedullary NGC acts as an inhibitory influence on tidal volume, breathing frequency and heart rate responses to the central command for exercise. In addition, NGC modulation of ventilation would appear to be selective for certain respiratory muscle groups.

Volume guarantee ventilation during surgical closure of patent ductus arteriosus.

PubMed

Keszler, Martin; Abubakar, Kabir

2015-01-01

Surgical closure of patent ductus arteriosus (PDA) is associated with adverse outcomes. Surgical exposure requires retraction of the lung, resulting in decreased aeration and compliance. Optimal respiratory support for PDA surgery is unknown. Experience with volume guarantee (VG) ventilation at our institution led us to hypothesize that surgery would be better tolerated with automatic adjustment of pressure by VG to maintain tidal volume (VT) during retraction. The objective of this study was to describe ventilator support, VT, and oxygenation of infants supported with VG during PDA surgery. Ventilator variables, oxygen saturation, and heart rate were recorded during PDA surgery in a convenience sample of infants during PDA closure on VG. Pressure limit increased 11% and set VT was 26% lower during lung retraction. Fentanyl and pancuronium/vecuronium were used for anesthesia/muscle relaxation. Longitudinal data were analyzed by analysis of variance for repeated measures. Seven infants, 25.4 ± 1.5 weeks and 723 ± 141 g, underwent closure of PDA on VG at a mean age 29.9 days. No air leak, bradycardia, or death occurred. Target VT was maintained with a modest increase in inflation pressure. Oxygenation remained adequate. VG avoided hypoxemia and maintained adequate VT with only a modest increase in peak inflation pressure and thus may be a useful mode during PDA surgery. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Heliox Improves Carbon Dioxide Removal during Lung Protective Mechanical Ventilation.

PubMed

Beurskens, Charlotte J; Brevoord, Daniel; Lagrand, Wim K; van den Bergh, Walter M; Vroom, Margreeth B; Preckel, Benedikt; Horn, Janneke; Juffermans, Nicole P

2014-01-01

Introduction. Helium is a noble gas with low density and increased carbon dioxide (CO2) diffusion capacity. This allows lower driving pressures in mechanical ventilation and increased CO2 diffusion. We hypothesized that heliox facilitates ventilation in patients during lung-protective mechanical ventilation using low tidal volumes. Methods. This is an observational cohort substudy of a single arm intervention study. Twenty-four ICU patients were included, who were admitted after a cardiac arrest and mechanically ventilated for 3 hours with heliox (50% helium; 50% oxygen). A fixed protective ventilation protocol (6 mL/kg) was used, with prospective observation for changes in lung mechanics and gas exchange. Statistics was by Bonferroni post-hoc correction with statistical significance set at P < 0.017. Results. During heliox ventilation, respiratory rate decreased (25 ± 4 versus 23 ± 5 breaths min(-1), P = 0.010). Minute volume ventilation showed a trend to decrease compared to baseline (11.1 ± 1.9 versus 9.9 ± 2.1 L min(-1), P = 0.026), while reducing PaCO2 levels (5.0 ± 0.6 versus 4.5 ± 0.6 kPa, P = 0.011) and peak pressures (21.1 ± 3.3 versus 19.8 ± 3.2 cm H2O, P = 0.024). Conclusions. Heliox improved CO2 elimination while allowing reduced minute volume ventilation in adult patients during protective mechanical ventilation.

Interplay of diverse environmental settings and their influence on the plankton community off Myanmar during the Spring Intermonsoon

NASA Astrophysics Data System (ADS)

Jyothibabu, R.; Win, Ni Ni; Shenoy, D. M.; Swe, U. Tint; Pratik, M.; Thwin, Swe; Jagadeesan, L.

2014-11-01

The northern Andaman Sea including the Myanmar waters is one of the least studied regions of the northern Indian Ocean. The freshwater and suspended sediments carried by Ayeyawady/Irrawaddy, the peculiar surface circulation, coastline morphology and shallow bathymetry in the Gulf of Mottama facilitate several diverse environmental settings in the study region. In order to understand the environmental settings and their linkages to the plankton community in the study region, this paper combined in situ data of 'First India-Myanmar Joint Oceanographic Expedition' with satellite oceanography observations. The study period was the Spring Intermonsoon (March-May), which was characterized by high tidal activity in the Gulf of Mottama region (tidal height 6-8 m) causing strong tidal currents and re-suspension of sediments. The tidal currents and eastward advection of Ayeyawady influx caused the lowest salinity, highest concentration of nutrients, suspended sediments and chlorophyll a in the Gulf of Mottama region. Conversely, high salinity, highest temperature, lowest nutrients and suspended sediments prevalent in the offshore waters of the northern Andaman Sea induced a massive bloom of Trichodesmium erythraeum, which was mostly in the declining phase during the observation. The in situ and satellite remote sensing data clearly showed that the T. erythraeum bloom observed in the offshore waters was closely linked to a warm core eddy. The decomposition of the bloom favored swarms of siphonophores and hydromedusae through a trophic link involving copepods and appendicularians. Aided by satellite remote sensing data and multivariate statistical tools, five diverse environmental settings have been identified in the study domain. The analysis showed a close coupling between phytoplankton biomass and nutrients with their higher values in the Gulf of Mottama, off Rakhine, Ayeyawady and Thanintharyi region as compared to the offshore waters in the northern Andaman Sea. The zooplankton community dominated by copepods and chaetognaths preferred regions with high salinity, chlorophyll, deep mixed layer and low suspended sediments as existed off Rakhine, Ayeyawady and Thanintharyi regions. The study evidences, for the first time, the spatial segregation of environmental settings and its linkages to the plankton community off Myanmar during the Spring Intermonsoon.

A massive early atmosphere on Triton

NASA Technical Reports Server (NTRS)

Lunine, Jonathan I.; Nolan, Michael C.

1992-01-01

The idea of an early greenhouse atmosphere for Triton is presented and the conditions under which it may have been sustained are quantified. The volatile content of primordial Triton is modeled, and tidal heating rates are assessed to set bounds on the available energy. The atmospheric model formalism is presented, and it is shown how a massive atmosphere could have been raised by modest tidal heating fluxes. The implications of the model atmospheres for the atmospheric escape rates, the chemical evolution, and the cratering record are addressed.

Tropospheric - Stratospheric Tidal Investigations. Part 2. The Vertical Structure of Atmospheric Oscillations Formulated by Classical Tidal Theory

DTIC Science & Technology

1981-02-28

in a form that may be applied to a numerical integracion scheme (Lindzen, 1968). It is now possible to express the upward energy flux at x >X L in...from tre setting up of a dependence on multiple reflexions between tiorizontal surfaces at different heights which are critically dependent on basic...longer horizontal and by integratJiw of the non-classical equations multiple reflexions and resuLtinr sensitivities are found to oe largely removed

Semi-isolated, flat-topped carbonate platform (Oligo-Miocene, Sardinia, Italy): Sedimentary architecture and processes

NASA Astrophysics Data System (ADS)

Andreucci, Stefano; Pistis, Marco; Funedda, Antonio; Loi, Alfredo

2017-11-01

The Chattian-Aquitanian carbonate system of Isili sub-basin (SE Sardinia, Italy) were studied to better understand the hydrodynamic processes controlling the formation of landward-downlapping, rhodolith-rich, giant clinoforms. The studied flat-topped platform was attached to an island (semi-isolated) and migrated onshore (landward) over a shallow marine, protected embayment. The depositional profile is characterized by four, sea to land, zones: seaward slope, flat-topped platform (submerged flat), landward slope and mixed siliciclastic-carbonate embayment. In particular, these zones record different levels, from high to moderate, of hydrodynamic energy and persistency. The paleodepth of the studied succession, based on T/D test on Amphistegina specimens, red-algal genera and geometric reconstruction of the overall system, ranges from - 10 to - 30 m for the platform up to around - 40 m for the landward slope base. Thus, the flat-topped platform was permanently submerged and an extensive carbonate (sea grass, algal and bryozoan-algal) factory along with oyster framestones developed. The widespread presence in the barren zones of rhodolith-to-shell rich small to very small compound dunes (high-energy zone) suggests that the flat-topped platform was periodically swept by unidirectional, landward-directed currents. These currents allow the formation of large-scale, rhodolith-rich clinobeds along the landward slope (washover fan-like system). The presence of rodolith pavements developed along the flat-topped platform at or slightly below the fairweather wave base suggests that clinobeds were formed in a nearshore, shallow subtidal setting. Finally, the shallow marine, protected embayment (moderate-energy zone) represents the widening distal reaches of the currents flowing or along the clinoforms or from the coast basinward (river floods and/or ebb tidal currents). Despite few tidal-related sedimentary structures such as bi-directional ripples and small compound dunes separated by finer-grained ;drapes; or reactivation surfaces were observed, the prevailing processes acting over the platform are unidirectional, landward-directed currents possibly associated with longshore currents and/or wave actions. However, the resultant migration of the whole system onshore (landward) cannot be easily explained with storm or wind-related processes. Thus the studied flat-topped platform seems to be controlled by long term tidal regulation within a meso to macro tidal regime. In particular, such meso/macro tidal environments experience multiannual to multidecennial phases of stronger/weaker tidal range fluctuations resembling periods of relatively sea highs and lows with respect to the mean sea level (0 m). All the (wind, storm, wave and tidal) currents sweeping the flat-topped platform were maxima during phases of strong tidal fluctuations generating erosion and sediment transportation over the flat and accumulation on the landward slope (clinobeds). Conversely, during phases of weaker tidal range fluctuations overall currents were minima, clinoforms did not develop and factories widespread re-colonized the submerged flat. Therefore, the studied platform developed in a current-dominated and tidal modulated setting. Finally, the studied carbonates of Sardinia suggest that the Sardinian seaway and the incipient Provençal basin during the Chattian-Aquitanian were, locally, capable to generate meso to macro tidal conditions.

TIDAL FRICTION AND TIDAL LAGGING. APPLICABILITY LIMITATIONS OF A POPULAR FORMULA FOR THE TIDAL TORQUE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Efroimsky, Michael; Makarov, Valeri V., E-mail: michael.efroimsky@usno.navy.mil, E-mail: vvm@usno.navy.mil

Tidal torques play a key role in rotational dynamics of celestial bodies. They govern these bodies' tidal despinning and also participate in the subtle process of entrapment of these bodies into spin-orbit resonances. This makes tidal torques directly relevant to the studies of habitability of planets and their moons. Our work begins with an explanation of how friction and lagging should be built into the theory of bodily tides. Although much of this material can be found in various publications, a short but self-consistent summary on the topic has been lacking in the hitherto literature, and we are filling themore » gap. After these preparations, we address a popular concise formula for the tidal torque, which is often used in the literature, for planets or stars. We explain why the derivation of this expression, offered in the paper by Goldreich and in the books by Kaula (Equation (4.5.29)) and Murray and Dermott (Equation (4.159)), implicitly sets the time lag to be frequency independent. Accordingly, the ensuing expression for the torque can be applied only to bodies having a very special (and very hypothetical) rheology which makes the time lag frequency independent, i.e., the same for all Fourier modes in the spectrum of tide. This expression for the torque should not be used for bodies of other rheologies. Specifically, the expression cannot be combined with an extra assertion of the geometric lag being constant, because at finite eccentricities the said assumption is incompatible with the constant-time-lag condition.« less

The role of bank collapse on tidal creek ontogeny: A novel process-based model for bank retreat

NASA Astrophysics Data System (ADS)

Gong, Zheng; Zhao, Kun; Zhang, Changkuan; Dai, Weiqi; Coco, Giovanni; Zhou, Zeng

2018-06-01

Bank retreat in coastal tidal flats plays a primary role on the planimetric shape of tidal creeks and is commonly driven by both flow-induced bank erosion and gravity-induced bank collapse. However, existing modelling studies largely focus on bank erosion and overlook bank collapse. We build a bank retreat model coupling hydrodynamics, bank erosion and bank collapse. To simulate the process of bank collapse, a stress-deformation model is utilized to calculate the stress variation of bank soil after bank erosion, and the Mohr-Coulomb failure criterion is then applied to evaluate the stability of the tidal creek bank. Results show that the bank failure process can be categorized into three stages, i.e., shear failure at the bank toe (stage I), tensile failure on the bank top (stage II), and sectional cracking from the bank top to the toe (stage III). With only bank erosion, the planimetric shapes of tidal creeks are funneled due to the gradually seaward increasing discharge. In contrast to bank erosion, bank collapse is discontinuous, and the contribution of bank collapse to bank retreat can reach 85%, highlighting that the expansion of tidal creeks can be dominated by bank collapse process. The planimetric shapes of tidal creeks are funneled with a much faster expansion rate when bank collapse is considered. Overall, this study makes a further step toward more physical and realistic simulation of bank retreat in estuarine and coastal settings and the developed bank collapse module can be readily included in other morphodynamic models.

The Power Coefficient in the Theory of Energy Extraction from Tidal Channels

NASA Astrophysics Data System (ADS)

Cummins, P. F.

2014-12-01

The maximum average power available from a fence of turbines deployed in a tidal channel is given by the simple formula, Ρ=γρgaQmax, where ρga is the amplitude of pressure difference across ends of the channel, Qmax is the maximum volume flux through the channel in the undisturbed state (i.e., before turbines are deployed), and γ is a numerical coefficient. The latter depends only weakly on the underlying dynamical balance of the channel. This is shown to be consequence of quadratic drag and changes to the natural impedance of the channel as deployment of turbines impedes the flow. Additionally, it is shown that the power coefficient γ is relatively insensitive to the form of the turbine drag.

Low-tidal volume mechanical ventilation in patients with acute respiratory distress syndrome caused by pandemic influenza A/H1N1 infection.

PubMed

Oh, Dong Kyu; Lee, Myung Goo; Choi, Eun Young; Lim, Jaemin; Lee, Hyun-Kyung; Kim, Seok Chan; Lim, Chae-Man; Koh, Younsuck; Hong, Sang-Bum

2013-08-01

Low-tidal volume (TV) mechanical ventilation is an important manipulation in managing patients with acute respiratory distress syndrome (ARDS). However, there is no definite evidence to support the use of this intervention in patients with viral etiologies. A retrospective observational study of 104 patients with ARDS caused by pandemic influenza A/H1N1 infection admitted to 28 intensive care units (ICUs) in Korea was performed. Patients were categorized into 3 groups according to the TV they received: TV less than or equal to 7 mL/kg, TV greater than 7 mL/kg but less than or equal to 9 mL/kg, or TV greater than 9 mL/kg. The mean age was 55.1 years, and 55.8% were male (n = 58). Patients with TV greater than 9 mL/kg showed higher 28-day ICU mortality than the 2 other groups (vs TV < 7 mL/kg, P = .007 and vs 7 mL/kg < TV ≤ 9 mL/kg, P = .004, respectively). Patients with TV less than or equal to 7 mL/kg required ventilators, ICU admissions, and hospitalizations for fewer days than those with TV greater than 7 mL/kg (11.4 vs 6.1 days for 28-day ventilator-free days, 9.7 vs 4.9 days for 28-day ICU-free days, and 5.2 vs 2.4 days for 28-day hospital-free days, respectively). Tidal volume greater than 9 mL/kg (hazard rate, 2.459; P = .003) and Sequential Organ Failure Assessment score (hazard rate, 1.158; P = .014) were significant predictors of 28-day ICU mortality. Low-TV mechanical ventilation still benefits patients with ARDS caused by viral pneumonia. Copyright © 2013 Elsevier Inc. All rights reserved.

[Efficacy of preoxygenation using tidal volume breathing: a comparison of Mapleson A, Bain's and Circle system].

PubMed

Arora, Suman; Gupta, Priyanka; Arya, Virender Kumar; Bhatia, Nidhi

Efficacy of preoxygenation depends upon inspired oxygen concentration, its flow rate, breathing system configuration and patient characteristics. We hypothesized that in actual clinical scenario, where breathing circuit is not primed with 100% oxygen, patients may need more time to achieve EtO 2 ≥90%, and this duration may be different among various breathing systems. We thus studied the efficacy of preoxygenation using unprimed Mapleson A, Bain's and Circle system with tidal volume breathing at oxygen flow rates of 5L.min -1 and 10L.min -1 . Patients were randomly allocated into one of the six groups, wherein they were preoxygenated using either Mapleson A, Bain's or Circle system at O 2 flow rate of either 5L.min -1 or 10L.min -1 . The primary outcome measure of our study was the time taken to achieve EtO 2 ≥90% at 5 and 10L.min -1 flow rates. At oxygen flow rate of 5L.min -1 , time to reach EtO 2 ≥90% was significantly longer with Bain's system (3.7±0.67min) than Mapleson A and Circle system (2.9±0.6, 3.3±0.97min, respectively). However at oxygen flow rate of 10L.min -1 this time was significantly shorter and comparable among all the three breathing systems (2.33±0.38min with Mapleson, 2.59±0.50min with Bain's and 2.60±0.47min with Circle system). With spontaneous normal tidal volume breathing at oxygen flow rate of 5L.min -1 , Mapleson A can optimally preoxygenate patients within 3min while Bain's and Circle system require more time. However at O 2 flow rate of 10L.min -1 all the three breathing systems are capable of optimally preoxygenating the patients in less than 3min. Copyright © 2017 Sociedade Brasileira de Anestesiologia. Publicado por Elsevier Editora Ltda. All rights reserved.

Tidal Heating in Multilayered Terrestrial Exoplanets

NASA Technical Reports Server (NTRS)

Henning, Wade G.; Hurford, Terry

2014-01-01

The internal pattern and overall magnitude of tidal heating for spin-synchronous terrestrial exoplanets from 1 to 2.5 R(sub E) is investigated using a propagator matrix method for a variety of layer structures. Particular attention is paid to ice-silicate hybrid super-Earths, where a significant ice mantle is modeled to rest atop an iron-silicate core, and may or may not contain a liquid water ocean. We find multilayer modeling often increases tidal dissipation relative to a homogeneous model, across multiple orbital periods, due to the ability to include smaller volume low viscosity regions, and the added flexure allowed by liquid layers. Gradations in parameters with depth are explored, such as allowed by the Preliminary Earth Reference Model. For ice-silicate hybrid worlds, dramatically greater dissipation is possible beyond the case of a silicate mantle only, allowing non-negligible tidal activity to extend to greater orbital periods than previously predicted. Surface patterns of tidal heating are found to potentially be useful for distinguishing internal structure. The influence of ice mantle depth and water ocean size and position are shown for a range of forcing frequencies. Rates of orbital circularization are found to be 10-100 times faster than standard predictions for Earth-analog planets when interiors are moderately warmer than the modern Earth, as well as for a diverse range of ice-silicate hybrid super-Earths. Circularization rates are shown to be significantly longer for planets with layers equivalent to an ocean-free modern Earth, as well as for planets with high fractions of either ice or silicate melting.

Comparison of intraoperative volume and pressure-controlled ventilation modes in patients who undergo open heart surgery.

PubMed

Hoşten, Tülay; Kuş, Alparslan; Gümüş, Esra; Yavuz, Şadan; İrkil, Serhat; Solak, Mine

2017-02-01

Respiratory problems occur more frequently in patients who undergo open heart surgery. Intraoperative and postoperative ventilation strategies can prevent these complications and reduce mortality. We hypothesized that PCV would have better effects on gas exchange, lung mechanics and hemodynamics compared to VCV in CABG surgery. Our primary outcome was to compare the PaO 2 /FiO 2 ratio. Patients were randomized into two groups, (VCV, PCV) consisting of 30 individuals each. Two patients were excluded from the study. I/E ratio was adjusted to 1:2 and, RR:10/min fresh air gas flow was set at 3L/min in all patients. In the VCV group TV was set at 8 mL/kg of the predicted body weight. In the PCV group, peak inspiratory pressure was adjusted to the same tidal volume with the VCV group. PaO2/FiO2 was found to be higher with PCV at the end of the surgery. Time to extubation and ICU length of stay was shorter with PCV. Ppeak was similar in both groups. Pplateau was lower and Pmean was higher at the and of the surgery with PCV compared to VCV. The hemodynamic effects of both ventilation modes were found to be similar. PVC may be preferable to VCV in patients who undergo open heart surgery. However, it would be convenient if our findings are supported by similar studies.

Changes in surfzone morphodynamics driven by multi-decadel contraction of a large ebb-tidal delta

USGS Publications Warehouse

Hansen, Jeff E.; Elias, Edwin; Barnard, Patrick L.; Barnard, P.L.; Jaffee, B.E.; Schoellhamer, D.H.

2013-01-01

The impact of multi-decadal, large-scale deflation (76 million m3 of sediment loss) and contraction (~ 1 km) of a 150 km2 ebb-tidal delta on hydrodynamics and sediment transport at adjacent Ocean Beach in San Francisco, CA (USA), is examined using a coupled wave and circulation model. The model is forced with representative wave and tidal conditions using recent (2005) and historic (1956) ebb-tidal delta bathymetry data sets. Comparison of the simulations indicates that along north/south trending Ocean Beach the contraction and deflation of the ebb-tidal delta have resulted in significant differences in the flow and sediment dynamics. Between 1956 and 2005 the transverse bar (the shallow attachment point of the ebb-tidal delta to the shoreline) migrated northward ~ 1 km toward the inlet while a persistent alongshore flow and transport divergence point migrated south by ~ 500 m such that these features now overlap. A reduction in tidal prism and sediment supply over the last century has resulted in a net decrease in offshore tidal current-generated sediment transport at the mouth of San Francisco Bay, and a relative increase in onshore-directed wave-driven transport toward the inlet, accounting for the observed contraction of the ebb-tidal delta. Alongshore migration of the transverse bar and alongshore flow divergence have resulted in an increasing proportion of onshore migrating sediment from the ebb-tidal delta to be transported north along the beach in 2005 versus south in 1956. The northerly migrating sediment is then trapped by Pt. Lobos, a rocky headland at the northern extreme of the beach, consistent with the observed shoreline accretion in this area. Conversely, alongshore migration of the transverse bar and divergence point has decreased the sediment supply to southern Ocean Beach, consistent with the observed erosion of the shoreline in this area. This study illustrates the utility of applying a high-resolution coupled circulation-wave model for understanding coastal response to large-scale bathymetric changes over multi-decadal timescales, common to many coastal systems adjacent to urbanized estuaries and watersheds worldwide.

Dead space and slope indices from the expiratory carbon dioxide tension-volume curve.

PubMed

Kars, A H; Bogaard, J M; Stijnen, T; de Vries, J; Verbraak, A F; Hilvering, C

1997-08-01

The slope of phase 3 and three noninvasively determined dead space estimates derived from the expiratory carbon dioxide tension (PCO2) versus volume curve, including the Bohr dead space (VD,Bohr), the Fowler dead space (VD,Fowler) and pre-interface expirate (PIE), were investigated in 28 healthy control subjects, 12 asthma and 29 emphysema patients (20 severely obstructed and nine moderately obstructed) with the aim to establish diagnostic value. Because breath volume and frequency are closely related to CO2 elimination, the recording procedures included varying breath volumes in all subjects during self-chosen/natural breathing frequency, and fixed frequencies of 10, 15 and 20 breaths x min(-1) with varying breath volumes only in the healthy controls. From the relationships of the variables with tidal volume (VT), the values at 1 L were estimated to compare the groups. The slopes of phase 3 and VD,Bohr at 1 L VT showed the most significant difference between controls and patients with asthma or emphysema, compared to the other two dead space estimates, and were related to the degree of airways obstruction. Discrimination between no-emphysema (asthma and controls) and emphysema patients was possible on the basis of a plot of intercept and slope of the relationship between VD,Bohr and VT. A combination of both the slope of phase 3 and VD,Bohr of a breath of 1 L was equally discriminating. The influence of fixed frequencies in the controls did not change the results. The conclusion is that Bohr dead space in relation to tidal volume seems to have diagnostic properties separating patients with asthma from patients with emphysema with the same degree of airways obstruction. Equally discriminating was a combination of both phase 3 and Bohr dead space of a breath of 1 L. The different pathophysiological mechanisms in asthma and emphysema leading to airways obstruction are probably responsible for these results.

Further development and testing of the metabolic gas analyzer

NASA Technical Reports Server (NTRS)

1973-01-01

Continued development of a metabolic monitor utilizing a mass spectrometer and digital computer to perform measurements and data reduction, is reported. The device prints-out breath-by-breath values for 02 consumption, C02 production, minute volume and tidal volume. The flow is measured by introduction of a tracer gas to the expired gas stream. Design modifications to reduce pressure drop in the flow splitter to one inch of water at 600 liters/min flow and to extend the range of linear flow measurement to 1000 liters/min are discussed.

Lidocaine use for pain management during paediatric dental rehabilitation under general anaesthesia.

PubMed

El Batawi, H Y

2013-12-01

Dental rehabilitation under general anaesthesia is gaining more popularity among parents as a result of increasing safety margins of new anaesthetic drugs and the adoption of strict policies and procedures that target patient safety and comfort. Harmony between members of the anaesthesia team and the dental team is a must to produce full dental service with least discomfort to our child patients. To investigate the possible effect of using local analgesia (lidocaine) during general anaesthesia sessions on stabilising heart rate, respiratory rate and tidal CO2 levels during painful dental procedures. Eighty ASA class I children undergoing full dental rehabilitation under general anaesthesia were divided into two groups of 40 each. Group A had the dental procedures carried out without lidocaine local analgesia, and group B had the procedures done with lidocaine local analgesia prior to painful dental procedures. Patient monitor readings were recorded by a group-allocation blinded anaesthesia technician and the two groups were compared statistically. Group A showed a statistically significant increase in heart rates and respiratory rates during dentine cutting, dental extractions and pulpotomies. No significant difference was observed between the two groups for changes in CO2 end-tidal volume during cavity preparations. During dental extractions and pulpotomies, Group A showed significantly lower carbon dioxide end-tidal volume. Use of local analgesia prior to performing pain-provoking dental procedures under general anaesthesia seems to help patient's homeostasis and stabilises vital signs. This may help in providing a safer anaesthesia environment for medically compromised children undergoing the same procedures under general anaesthesia.

Simulation of the effects of proposed tide gates on circulation, flushing, and water quality in residential canals, Cape Coral Florida

USGS Publications Warehouse

Goodwin, Carl R.

1991-01-01

Decades of dredging and filling of Florida's low-lying coastal wetlands have produced thousands of miles of residential tidal canals and adjacent waterfront property. Typically, these canals are poorly flushed, and over time, accumulated organic-rich bottom materials, contribute to an increasingly severe degraded water quality. One-dimensional hydrodynamic and constituent-transport models were applied to two dead-end canal systems to determine the effects of canal system interconnection using tide gates on water circulation and constituent flushing. The model simulates existing and possible future circulation and flushing conditions in about 29 miles of the approximately 130 miles of tidally influenced canals in Cape Coral, located on the central west coast of peninsular Florida. Model results indicate that tidal water-level differences between the two canal systems can be converted to kinetic energy, in the form of increased water circulation, but the use of one-way tide gate interconnections. Computations show that construction of from one to four tide gates will cause replacement of a volume of water equivalent to the total volume of canals in both systems in 15 to 9 days, respectively. Because some canals flush faster than others, 47 and 21 percent of the original canal water will remain in both systems 50 days after start of operation of one and four tide gates, respectively. Some of the effects that such increased flushing are expected to have include reduced density stratification and associated dissolved-oxygen depletion in canal bottom waters, increased localized reaeration, and more efficient discharge of stormwater runoff entering the canals.

Development of a Reference Coastal Wetland set in Southern New England (USA)

EPA Science Inventory

Various measures of plants, soils, and invertebrates were described for a reference set of tidal coastal wetlands in southern New England in order to provide a framework for assessing the condition of other similar wetlands in the region. The condition of the ten coastal wetland...

Effects of 27-day averaged tidal forcing on the thermosphere-ionosphere as examined by the TIEGCM

NASA Astrophysics Data System (ADS)

Maute, A. I.; Forbes, J. M.; Hagan, M. E.

2016-12-01

The variability of the ionosphere and thermosphere is influenced by solar and geomagnetic forcing and by lower atmosphere coupling. During the last solar minimum low- and mid-latitude ionospheric observations have shown strong longitudinal signals which are associated with upward propagating tides. Progress has been made in explaining observed ionospheric and thermospheric variations by investigating possible coupling mechanisms e.g., wind dynamo, propagation of tides into the upper thermosphere, global circulation changes, and compositional effects. To fully understand the vertical coupling a comprehensive set of simultaneous measurements of key quantities is missing. The Ionospheric Connection (ICON) explorer will provide such a data set and the data interpretation will be supported by numerical modeling to investigate the lower to upper atmosphere coupling. Due to ICON's orbit, 27 days of measurements are needed to cover all longitudes and local times and to be able to derive tidal components. In this presentation we employ the Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM) to evaluate the influence of the 27-day processing window on the ionosphere and thermosphere state. Specifically, we compare TIEGCM simulations that are forced at its 97 km lower boundary by daily tidal fields from 2009 MERRA-forced TIME-GCM output [Häusler et al., 2015], and by the corresponding 27-day mean tidal fields. Apart from the expected reduced day-to-day variability when using 27-day averaged tidal forcing, the simulations indicate net NmF2 changes at low latitudes, which vary with season. First results indicate that compositional effects may influence the Nmf2 modifications. We will quantify the effect of using a 27-day averaged diurnal tidal forcing versus daily ones on the equatorial vertical drift, low and mid-latitude NmF2 and hmF2, global circulation, and composition. The possible causes for the simulated changes will be examined. The result of this study will be important for the comparison of the ICON observations with the accompanying ICON-TIEGCM simulations and guide the model-data interpretation.

Cardiopulmonary function and oxygen delivery during total liquid ventilation.

PubMed

Tsagogiorgas, Charalambos; Alb, Markus; Herrmann, Peter; Quintel, Michael; Meinhardt, Juergen P

2011-10-01

Total liquid ventilation (TLV) with perfluorocarbons has shown to improve cardiopulmonary function in the injured and immature lung; however there remains controversy over the normal lung. Hemodynamic effects of TLV in the normal lung currently remain undetermined. This study compared changes in cardiopulmonary and circulatory function caused by either liquid or gas tidal volume ventilation. In a prospective, controlled study, 12 non-injured anesthetized, adult New Zealand rabbits were primarily conventionally gas-ventilated (CGV). After instrumentation for continuous recording of arterial (AP), central venous (CVP), left artrial (LAP), pulmonary arterial pressures (PAP), and cardiac output (CO) animals were randomized into (1) CGV group and (2) TLV group. In the TLV group partial liquid ventilation was initiated with instillation of perfluoroctylbromide (12 ml/kg). After 15 min, TLV was established for 3 hr applying a volume-controlled, pressure-limited, time-cycled ventilation mode using a double-piston configured TLV. Controls (CGV) remained gas-ventilated throughout the experiment. During TLV, heart rate, CO, PAP, MAP, CVP, and LAP as well as derived hemodynamic variables, arterial and mixed venous blood gases, oxygen delivery, PVR, and SVR did not differ significantly compared to CGV. Liquid tidal volumes suitable for long-term TLV in non-injured rabbits do not significantly impair CO, blood pressure, and oxygen dynamics when compared to CGV. Copyright © 2011 Wiley-Liss, Inc.

Variable versus conventional lung protective mechanical ventilation during open abdominal surgery: study protocol for a randomized controlled trial.

PubMed

Spieth, Peter M; Güldner, Andreas; Uhlig, Christopher; Bluth, Thomas; Kiss, Thomas; Schultz, Marcus J; Pelosi, Paolo; Koch, Thea; Gama de Abreu, Marcelo

2014-05-02

General anesthesia usually requires mechanical ventilation, which is traditionally accomplished with constant tidal volumes in volume- or pressure-controlled modes. Experimental studies suggest that the use of variable tidal volumes (variable ventilation) recruits lung tissue, improves pulmonary function and reduces systemic inflammatory response. However, it is currently not known whether patients undergoing open abdominal surgery might benefit from intraoperative variable ventilation. The PROtective VARiable ventilation trial ('PROVAR') is a single center, randomized controlled trial enrolling 50 patients who are planning for open abdominal surgery expected to last longer than 3 hours. PROVAR compares conventional (non-variable) lung protective ventilation (CV) with variable lung protective ventilation (VV) regarding pulmonary function and inflammatory response. The primary endpoint of the study is the forced vital capacity on the first postoperative day. Secondary endpoints include further lung function tests, plasma cytokine levels, spatial distribution of ventilation assessed by means of electrical impedance tomography and postoperative pulmonary complications. We hypothesize that VV improves lung function and reduces systemic inflammatory response compared to CV in patients receiving mechanical ventilation during general anesthesia for open abdominal surgery longer than 3 hours. PROVAR is the first randomized controlled trial aiming at intra- and postoperative effects of VV on lung function. This study may help to define the role of VV during general anesthesia requiring mechanical ventilation. Clinicaltrials.gov NCT01683578 (registered on September 3 3012).

Does the dwarf galaxy system of the Milky Way originate from Andromeda?

NASA Astrophysics Data System (ADS)

Fouquet, Sylvain; Hammer, François; Yang, Yanbin; Puech, Mathieu; Flores, Hector

2012-12-01

The Local Group is often seen to be a quiescent environment without significant merger events. However, an ancient major merger may have occurred in the most massive galaxy as suggested by the M31 classical bulge and its halo haunted by numerous stellar streams. Numerical simulations have shown that tidal tails formed during gas-rich major mergers are long-lived and could be responsible for old stellar streams and likely induce the formation of tidal dwarf galaxies (TDGs). Using several hydrodynamical simulations we have investigated the most prominent tidal tail formed during the first passage, which is gas rich and contains old and metal-poor stars. We discovered several striking coincidences after comparing its location and motion to those of the Milky Way (MW) and of the Magellanic Clouds (MCs). First, the tidal tail is sweeping a relatively small volume in which the MW precisely lies. Because the geometry of the merger is somehow fixed by the anisotropic properties of the giant stream (GS), we evaluate the chance of the MW to be at such a rendezvous with this gigantic tidal tail to be 5 per cent. Secondly, the velocity of the tidal tail matches the Large Magellanic Cloud (LMC) proper motion, and reproduces quite well the geometrical and angular momentum properties of the MW dwarfs, that is, the so-called disc of satellites, also known as the vast polar structure (VPOS). Thirdly, the simulation of the tidal tail reveals one of the formed TDGs with the mass and location almost comparable to those of the LMC. Our present modelling is, however, too limited to study the detailed interaction of gas-rich TDGs with the potential of the MW, and a complementary study is required to test whether the dwarf intrinsic properties can be accounted for by our scenario. Nevertheless this study suggests a causal link between an expected event, an ancient, gas-rich major merger at the M31 location, and several enigmas in the Local Group, namely the GS in the M31 outskirts, the VPOS almost perpendicular to the MW disc, and the presence of the MCs, two Irr galaxies near the MW.

Anthropogenic influences on shoreline and nearshore evolution in the San Francisco Bay coastal system

USGS Publications Warehouse

Dallas, K.L.; Barnard, P.L.

2011-01-01

Analysis of four historical bathymetric surveys over a 132-year period has revealed significant changes to the morphology of the San Francisco Bar, an ebb-tidal delta at the mouth of San Francisco Bay estuary. From 1873 to 2005 the San Francisco Bar vertically-eroded an average of 80 cm over a 125 km2 area, which equates to a total volume loss of 100 ± 52 million m3 of fine- to coarse-grained sand. Comparison of the surveys indicates the entire ebb-tidal delta contracted radially, with the crest moving landward an average of 1 km. Long-term erosion of the ebb-tidal delta is hypothesized to be due to a reduction in the tidal prism of San Francisco Bay and a decrease in coastal sediment supply, both as a result of anthropogenic activities. Prior research indicates that the tidal prism of the estuary was reduced by 9% from filling, diking, and sedimentation. Compilation of historical records dating back to 1900 reveals that a minimum of 200 million m3 of sediment has been permanently removed from the San Francisco Bay coastal system through dredging, aggregate mining, and borrow pit mining. Of this total, ~54 million m3 of sand-sized or coarser sediment was removed from central San Francisco Bay. With grain sizes comparable to the ebb-tidal delta, and its direct connection to the bay mouth, removal of sediments from central San Francisco Bay may limit the sand supply to the delta and open coast beaches. SWAN wave modeling illustrates that changes to the morphology of the San Francisco Bar have altered the alongshore wave energy distribution at adjacent Ocean Beach, and thus may be a significant factor in a persistent beach erosion ‘hot spot’ occurring in the area. Shoreline change analyses show that the sandy shoreline in the shadow of the ebb-tidal delta experienced long-term (1850s/1890s to 2002) and short-term (1960s/1980s to 2002) accretion while the adjacent sandy shoreline exposed to open-ocean waves experienced long-term and short-term erosion. Therefore, the recently observed accelerating rates of bay sediment removal, ebb-tidal delta erosion, and open coast beach erosion are all correlated temporally.

Acquired tracheoesophageal fistula due to high intracuff pressure.

PubMed

Hameed, Akmal A; Mohamed, Hasan; Al-Mansoori, Motasem

2008-01-01

High-compliance endotracheal tube cuffs are used to prevent gas leak and also pulmonary aspiration in mechanically ventilated patients. However, the use of the usual cuff inflation volumes may cause tracheal damage and lead to tracheoesophageal fistula.Tracheostomy tube cuffs seal against the tracheal wall and prevent leakage of air around the tube, assuring that the tidal volume is delivered to the lungs. In the past, high-pressure cuffs were used, but these contributed to tracheal injury and have been replaced by high-volume, low-pressure cuffs. For long-term applications, some newer tubes have low-profile (tight to shaft) cuffs that facilitate the tracheostomy tube changes by eliminating the lip that forms when standard cuffs are deflated.

On the ecogeomorphological feedbacks that control tidal channel network evolution in a sandy mangrove setting

PubMed Central

van Maanen, B.; Coco, G.; Bryan, K. R.

2015-01-01

An ecomorphodynamic model was developed to study how Avicennia marina mangroves influence channel network evolution in sandy tidal embayments. The model accounts for the effects of mangrove trees on tidal flow patterns and sediment dynamics. Mangrove growth is in turn controlled by hydrodynamic conditions. The presence of mangroves was found to enhance the initiation and branching of tidal channels, partly because the extra flow resistance in mangrove forests favours flow concentration, and thus sediment erosion in between vegetated areas. The enhanced branching of channels is also the result of a vegetation-induced increase in erosion threshold. On the other hand, this reduction in bed erodibility, together with the soil expansion driven by organic matter production, reduces the landward expansion of channels. The ongoing accretion in mangrove forests ultimately drives a reduction in tidal prism and an overall retreat of the channel network. During sea-level rise, mangroves can potentially enhance the ability of the soil surface to maintain an elevation within the upper portion of the intertidal zone, while hindering both the branching and headward erosion of the landward expanding channels. The modelling results presented here indicate the critical control exerted by ecogeomorphological interactions in driving landscape evolution. PMID:26339195

Three-Dimensional Dynamics of Baroclinic Tides Over a Seamount

NASA Astrophysics Data System (ADS)

Vlasenko, Vasiliy; Stashchuk, Nataliya; Nimmo-Smith, W. Alex M.

2018-02-01

The Massachusetts Institute of Technology general circulation model is used for the analysis of baroclinic tides over Anton Dohrn Seamount (ADS), in the North Atlantic. The model output is validated against in situ data collected during the 136th cruise of the RRS "James Cook" in May-June 2016. The observational data set includes velocity time series recorded at two moorings as well as temperature, salinity, and velocity profiles collected at 22 hydrological stations. Synthesis of observational and model data enabled the reconstruction of the details of baroclinic tidal dynamics over ADS. It was found that the baroclinic tidal waves are generated in the form of tidal beams radiating from the ADS periphery to its center, focusing tidal energy in a surface layer over the seamount's summit. This energy focusing enhances subsurface water mixing and the local generation of internal waves. The tidal beams interacting with the seasonal pycnocline generate short-scale internal waves radiating from the ADS center. An important ecological outcome from this study concerns the pattern of residual currents generated by tides. The rectified flows over ADS have the form of a pair of dipoles, cyclonic and anticyclonic eddies located at the seamount's periphery. These eddies are potentially an important factor in local larvae dispersion and their escape from ADS.

New Model for Europa's Tidal Response Based after Laboratory Measurements

NASA Astrophysics Data System (ADS)

Castillo, J. C.; McCarthy, C.; Choukroun, M.; Rambaux, N.

2009-12-01

We explore the application of the Andrade model to the modeling of Europa’s tidal response at the orbital period and for different librations. Previous models have generally assumed that the satellite behaves as a Maxwell body. However, at the frequencies exciting Europa’s tides and librations, material anelasticity tends to dominate the satellite’s response for a wide range of temperatures, a feature that is not accounted for by the Maxwell model. Many experimental studies on the anelasticity of rocks, ice, and hydrates, suggest that the Andrade model usually provides a good fit to the dissipation spectra obtained for a wide range of frequencies, encompassing the tidal frequencies of most icy satellites. These data indicate that, at Europa’s orbital frequency, the Maxwell model overestimates water ice attenuation at temperature warmer than ~240 K, while it tends to significantly underestimate it at lower temperatures. Based on the available data we suggest an educated extrapolation of available data to Europa’s conditions. We compute the tidal response of a model of Europa differentiated in a rocky core and a water-rich shell. We assume various degrees of stratification of the core involving hydrated and anhydrous silicates, as well as an iron core. The water-rich shell of Europa is assumed to be fully frozen, or to have preserved a deep liquid layer. In both cases we consider a range of thermal structures, based on existing models. These structures take into account the presence of non-ice materials, especially hydrated salts. This new approach yields a greater tidal response (amplitude and phase lag) than previously expected. This is due to the fact that a greater volume of material dissipates tidal energy in comparison to models assuming a Maxwell body. Another feature of interest is that the tidal stress expected in Europa is at about the threshold between a linear and non-linear mechanical response of water ice as a function of stress. Increased stress at a time when Europa’s eccentricity was greater than its current value is likely to have resulted in significant dissipation increase. We will assess how this new approach affects our understanding of Europa, and we will quantify the tidal response of this satellite and the amount of tidal heating available to its evolution. Acknowledgements: Part of this work has been conducted at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. Government sponsorship acknowledged. Part of the experimental work was conducted at Brown University, funded by NASA. MC is supported by a NASA Postdoctoral Fellowship, administered by Oak Ridge Associated Universities.

A spatial characterization of the Sagittarius dwarf galaxy tidal tails

DOE Office of Scientific and Technical Information (OSTI.GOV)

Newby, Matthew; Cole, Nathan; Newberg, Heidi Jo

2013-06-01

We measure the spatial density of F turnoff stars in the Sagittarius dwarf tidal stream, from Sloan Digital Sky Survey data, using statistical photometric parallax. We find a set of continuous, consistent parameters that describe the leading Sgr stream's position, direction, and width for 15 stripes in the north Galactic cap, and three stripes in the south Galactic cap. We produce a catalog of stars that has the density characteristics of the dominant leading Sgr tidal stream that can be compared with simulations. We find that the width of the leading (north) tidal tail is consistent with recent triaxial andmore » axisymmetric halo model simulations. The density along the stream is roughly consistent with common disruption models in the north, but possibly not in the south. We explore the possibility that one or more of the dominant Sgr streams has been misidentified, and that one or more of the ''bifurcated'' pieces is the real Sgr tidal tail, but we do not reach definite conclusions. If two dwarf progenitors are assumed, fits to the planes of the dominant and ''bifurcated'' tidal tails favor an association of the Sgr dwarf spheroidal galaxy with the dominant southern stream and the ''bifurcated'' stream in the north. In the north Galactic cap, the best fit Hernquist density profile for the smooth component of the stellar halo is oblate, with a flattening parameter q = 0.53, and a scale length of r {sub 0} = 6.73. The southern data for both the tidal debris and the smooth component of the stellar halo do not match the model fits to the north, although the stellar halo is still overwhelmingly oblate. Finally, we verify that we can reproduce the parameter fits on the asynchronous MilkyWay@home volunteer computing platform.« less

Marine Hydrokinetic Energy Site Identification and Ranking Methodology Part II: Tidal Energy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kilcher, Levi; Thresher, Robert; Tinnesand, Heidi

Marine hydrokinetic energy is a promising and growing piece of the renewable energy sector that offers high predictability and additional energy sources for a diversified energy economy. This report investigates the market opportunities for tidal energy along the U.S. coastlines. It is part one of a two-part investigation into the United States' two largest marine hydrokinetic resources (wave and tidal). Tidal energy technology is still an emerging form of renewable energy for which large-scale grid-connected project costs are currently poorly defined. Ideally, device designers would like to know the resource conditions at economical project sites so they can optimize devicemore » designs. On the other hand, project developers need detailed device cost data to identify sites where projects are economical. That is, device design and siting are, to some extent, a coupled problem. This work describes a methodology for identifying likely deployment locations based on a set of criteria that tidal energy experts in industry, academia, and national laboratories agree are likely to be important factors for all technology types. Several factors that will affect tidal project costs and siting have not been considered here -- including permitting constraints, conflicting use, seasonal resource variability, extreme event likelihood, and distance to ports -- because consistent data are unavailable or technology-independent scoring could not be identified. As the industry continues to mature and converge around a subset of device archetypes with well-defined costs, more precise investigations of project siting that include these factors will be possible. For now, these results provide a high-level guide pointing to the regions where markets and resource will one day support commercial tidal energy projects.« less

Tidally driven pore water exchange within offshore intertidal sandbanks: Part II numerical simulations

NASA Astrophysics Data System (ADS)

Gibbes, B.; Robinson, C.; Li, L.; Lockington, D.; Li, H.

2008-12-01

Field measurements presented by [Gibbes, B., Robinson, C., Li, L., Lockington, D.A., Carey, H., 2008. Tidally driven pore water exchange within offshore intertidal sandbanks: Part I Field measurements. Estuarine, Coastal and Shelf Science 79, pp. 121-132.] revealed a tidally driven pore water flow system within an offshore intertidal sandbank in Moreton Bay, Australia. The field data suggested that this flow system might be capable of delivering nutrients, and in particular bio-available iron, across the sediment-water interface. Bio-available iron has been implicated as a key nutrient in the growth of the toxic marine cyanobacteria Lyngbya majuscula and therefore this pore water exchange process is of interest at sites where L. majuscula blooms have been observed. In this study two-dimensional numerical simulations were used in conjunction with hydraulic data from field measurements to further investigate the tidally induced pore water flow patterns. Simulation results generally showed good agreement with the field data and revealed a more complex residual pore water flow system in the sandbank than shown by the field data. The flow system, strongly influenced by the geometry of the sandbank, was characterized by two circulation cells which resulted in pore water discharge at the bank edge and also to a permanently ponded area within the sandbank interior. Simulated discharge volumes in these two zones were in the order of 0.813 m 3 and 0.143 m 3 per meter width (along shore) of sandbank per tidal cycle at the bank edge and sandbank interior respectively. Transit times of pore water circulating through these cells were found to range from ≈ 17 days to > 60 years with an average time of 780 days. The results suggest that the tidally driven flow systems might provide a mechanism for transport of bio-available iron across the sediment-water interface. This flow could constitute a previously unrecognized source of bio-available iron for L. majuscula blooms in the Bay.

Breathing strategy of the adult horse (Equus caballus) at rest.

PubMed

Koterba, A M; Kosch, P C; Beech, J; Whitlock, T

1988-01-01

To investigate the mechanism underlying the polyphasic airflow pattern of the equine species, we recorded airflow, tidal volum, rib cage and abdominal motion, and the sequence of activation of the diaphragm, intercostal, and abdominal muscles during quiet breathing in nine adult horses standing at rest. In addition, esophageal, abdominal, and transdiaphragmatic pressures were simultaneously recorded using balloon-tipped catheters. Analysis of tidal flow-volume loops showed that, unlike humans, the horse at rest breathes around, rather than from, the relaxed volume of the respiratory system (Vrx). Analysis of the pattern of electromyographic activities and changes in generated pressures during the breathing cycle indicate that the first part of expiration is passive, as in humans, with deflation toward Vrx, but subsequent abdominal activity is responsible for a second phase of expiration: active deflation to below Vrx. From this end-expiratory volume, passive inflation occurs toward Vrx, followed by a second phase of inspiration: active inflation to above Vrx, brought about by inspiratory muscle contraction. Under these conditions the abdominal muscles appear to share the principal pumping duties with the diaphragm. Adoption of this breathing strategy by the horse may relate to its peculiar thoracoabdominal anatomic arrangement and to its very low passive chest wall compliance. We conclude that there is a passive and active phase to both inspiration and expiration due to the coordinated action of the respiratory pump muscles responsible for the resting adult horse's biphasic inspiratory and expiratory airflow pattern. This unique breathing pattern perhaps represents a strategy of minimizing the high elastic work of breathing in this species, at least at resting breathing frequencies.

Sedimentary fabrics of the macrotidal, mud-dominated, inner estuary to fluvio-tidal transition zone, Petitcodiac River estuary, New Brunswick, Canada

NASA Astrophysics Data System (ADS)

Shchepetkina, Alina; Gingras, Murray K.; Zonneveld, John-Paul; Pemberton, S. George

2016-03-01

The study provides a detailed description of mud-dominated sedimentary fabrics and their application for the rock record within the inner estuary to the fluvial zone of the Petitcodiac River estuary, New Brunswick, Canada. Sedimentological characteristics and facies distributions of the clay- and silt-rich deposits are reported. The inner estuary is characterized by thick accumulations of interbedded silt and silty clay on intertidal banks that flank the tidally influenced channel. The most common sedimentary structures observed are parallel and wavy lamination, small-scale soft-sediment deformation with microfaults, and clay and silt current ripples. The tidal channel contains sandy silt and clayey silt with planar lamination, massive and convolute bedding. The fluvio-tidal transition zone is represented by interbedded trough cross-stratified sand and gravel beds with planar laminated to massive silty mud. The riverine, non-tidal reach of the estuary is characterized by massive, planar tabular and trough cross-stratified gravel-bed deposits. The absence of bioturbation within the inner estuary to the fluvio-tidal transition zone can be explained by the following factors: low water salinities (0-5 ppt), amplified tide and current speeds, and high concentrations of flocculated material in the water body. Notably, downstream in the middle and outer estuary, bioturbation is seasonally pervasive: in those locales the sedimentary conditions are similar, but salinity is higher. In this study, the sedimentological (i.e., grain size, bedding characters, sedimentary structures) differences between the tidal estuary and the fluvial setting are substantial, and those changes occur over only a few hundred meters. This suggests that the widely used concept of an extensive fluvio-tidal transition zone and its depositional character may not be a geographically significant component of fluvial or estuary deposits, which can go unnoticed in the study of the ancient rocks.

Eddy Covariance Measurements of CO2 and CH4 before and after a Wetland Restoration, Tomago NSW, Australia: A Blue Carbon Investigation

NASA Astrophysics Data System (ADS)

Macsween, K.; Edwards, G. C.; Saintilan, N.; Negandhi, K.; Kelleway, J.; Rogers, K.; Safari, D.; Tewari, K.

2017-12-01

Australia holds 33% of the world's tidal marsh area. Scientific and policy interest has recently turned to the value of coastal wetlands for carbon sequestration ("Blue Carbon"). These coastal mangrove and saltmarsh restorations are now at the forefront of developments for ecosystem-based climate change mitigation and adaptation. The Tomago wetland located near Newcastle, NSW, Australia is undergoing rehabilitation restoring tidal inundation to a previously leveed floodplain. It is hypothesised that the restoration of tidal inundation would convert a methane source into a sink as a consequence of soil salinization. At Tomago a Before-After-Control-Impact experimental design has been undertaken to measure the impact of tidal reinstatement on wetland floodplain accretion and gas flux. Prior to tidal reinstatement, eddy covariance towers (CO2 and CH4) were installed as well as surface elevation tables, and continuous water level and water quality loggers. Hydrodynamic modelling identified the sites within the wetland predicted to remain disconnected from tidal flow. Concurrent with the micrometeorological energy balance and gas flux measurements environmental variables such as soil water salinity, inundation regime, and soil microbial communities were undertaken. This comprehensive set of data facilitated the predictive power to explain variation in greenhouse gas flux. Results showed the average CO2 and CH4 fluxes before tidal reinstatement to be -22.70 and 0.25 mg m-2 hr-1 respectively and after tidal reinstatement to be 6.41 and 0.16 mg m-2 hr-1. Over the year the average CO2 and CH4 fluxes were -3.29 and 0.20 mg m-2 hr-1. Results showed CO2 is driving the system in terms of net carbon. Two extreme precipitation events during the measurement period had significant influence on the carbon pool. It was shown that it is possible to regulate CH4 flux through management of water and salinity levels.

Neopuff T-piece resuscitator mask ventilation: Does mask leak vary with different peak inspiratory pressures in a manikin model?

PubMed

Maheshwari, Rajesh; Tracy, Mark; Hinder, Murray; Wright, Audrey

2017-08-01

The aim of this study was to compare mask leak with three different peak inspiratory pressure (PIP) settings during T-piece resuscitator (TPR; Neopuff) mask ventilation on a neonatal manikin model. Participants were neonatal unit staff members. They were instructed to provide mask ventilation with a TPR with three PIP settings (20, 30, 40 cm H 2 O) chosen in a random order. Each episode was for 2 min with 2-min rest period. Flow rate and positive end-expiratory pressure (PEEP) were kept constant. Airway pressure, inspiratory and expiratory tidal volumes, mask leak, respiratory rate and inspiratory time were recorded. Repeated measures analysis of variance was used for statistical analysis. A total of 12 749 inflations delivered by 40 participants were analysed. There were no statistically significant differences (P > 0.05) in the mask leak with the three PIP settings. No statistically significant differences were seen in respiratory rate and inspiratory time with the three PIP settings. There was a significant rise in PEEP as the PIP increased. Failure to achieve the desired PIP was observed especially at the higher settings. In a neonatal manikin model, the mask leak does not vary as a function of the PIP when the flow rate is constant. With a fixed rate and inspiratory time, there seems to be a rise in PEEP with increasing PIP. © 2017 Paediatrics and Child Health Division (The Royal Australasian College of Physicians).

A Lower Permian sandwave-containing shelf sequence exposed at Zungwini Mountain, Republic of South Africa

NASA Astrophysics Data System (ADS)

Smith, A. M.

1989-08-01

As a result of railway excavations the Pietermaritzburg Shale-Vryheid Formation transition is spectacularly exposed on the southern slope of Zungwini Mountain. Nine facies and three facies associations are recognised. Deposition occurred in a palaeoshelf and offshore setting. The reconstructed coastline was SW-NE with land to the northwest. The inner shelf was tide- and the outer-shelf storm-influenced. Fluvial input supplied sediment which was reworked into flood-tidal sandwaves, probably within the confines of an estuary. A rising sea level brought the sandwaves into the realm of a more distal, coast-parallel, storm-tidal current regime where reworking of the sediment occurred. Intense storm-augmented tidal currents swept some of the better-sorted material seaward to be deposited as storm layers in the inner and outer shelf. These same currents formed the low-density turbidites and sediment plumes from which the offshore argillaceous deposits were formed. The shelf edge poorly sorted rhythmite facies may have developed from sediment flushed out of the rivers during flood or from the flood-tidal sandwave system as a result of exceptional coastal storms.

In Search for Sustainable Coastal Management: A Case Study of Semarang, Indonesia

NASA Astrophysics Data System (ADS)

Hadi, Sudharto P.

2017-02-01

As a coastal town, Semarang is currently facing environmental problems such as flood, tidal flood (locally called rob), coastal abrasion, emerging land, land subsidence and sea water intrusion. These phenomena severely affect to citizen, community and corporate, disrupting day to day activities, threatening people’s health, causing economics’ burden and reducing property value. Government policies in dealing with these problem are focused on its phenomena such as normalizing river for flood and building polder systems for tidal flood. Impacted people have been implementing various initiatives. People in Tanah Mas Estate set up collective efforts to reduce tidal flood by building pumping system project, while people in Kampong Tambaklorok conduct a regular mutual assistance in cleaning of waste and sedimentation, rehabilitating of local drainages and dikes, reconstructing of local streets and also maintaining of pumping system. People in Mangunharjo, the district of Tugu build a coastal belt and cultivate mangrove. Various government and local initiatives have been effective in dealing with flood and tidal flood temporarily. More comprehensive approaches and focused on the sources of problems are required to achieve sustainable coastal management.

Stellar Death by Black Hole: How Tidal Disruption Events Unveil the High Energy Universe

NASA Astrophysics Data System (ADS)

Coughlin, Eric Robert

2017-08-01

When a star comes very close to a supermassive black hole, the tidal field of the hole can be strong enough to deform and stretch the star into a stream of debris. Half of this stellar debris stream returns to the black hole and forms an accretion disk, briefly lighting up the black hole and, in the most extreme cases, launching relativistic jets. These ``tidal disruption events,'' from the initial stellar destruction to the eventual jet production, are the focus of my thesis, and during this talk I will describe some of the theoretical advances we have made in understanding them. I will also discuss more recent work that shows how this relatively simple picture can be more complicated when the disrupting black hole is part of a binary system. Despite the added complexity, I will argue that there is a timescale over which one expects to see variation in the luminosity of a tidal disruption event from a binary supermassive black hole system. Using these predictions and a set of simulations, I will motivate such an interpretation for the superluminous supernova ASASSN-15lh.

Vapor cycle energy system for implantable circulatory assist devices. Annual progress report Jul 1974--Jun 1975. [Tidal regenerator engine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hagen, K.G.

1975-06-01

The report describes the development status of a heart assist system driven by a nuclear fueled, electronically controlled vapor cycle engine termed the tidal regenerator engine (TRE). The TRE pressurization (typically from 5-160 psia) is controlled by a torque motor coupled to a displacer. The electrical power for the sensor, electronic logic and actuator is provided by a thermoelectric module interposed between the engine superheater and boiler. The TRE is direct coupled to an assist blood pump which also acts as a blood-cooled heat exchanger, pressure-volume transformer and sensor for the electronic logic. Engine efficiencies in excess of 14% havemore » been demonstrated. Efficiency values as high as 13% have been achieved to date.« less

Impacts of Sea Level Rise and Morphological Changes on Tidal Hydrodynamics in the Northern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Passeri, D. L.; Hagen, S. C.; Plant, N. G.; Bilskie, M. V.

2014-12-01

Sea level rise (SLR) threatens coastal environments with increased erosion, inundation of wetlands, and changes in hydrodynamic patterns. Planning for the effects of SLR requires understanding the coupled response of SLR, geomorphic and hydrodynamic processes; this will provide crucial information for managers to make informed decisions for human and natural communities. Evaluating changes in tidal hydrodynamics under future scenarios is a key aspect for understanding the effects of SLR on coastal systems; tidal hydrodynamics influence inundation, circulation patterns, sediment transport processes, shoreline erosion, and productivity of marshes and other species. This study evaluates the dynamic effects of SLR and morphologic change on tidal hydrodynamics along the Northern Gulf of Mexico (NGOM) coast from Mississippi to the Florida panhandle. A large-scale hydrodynamic model is used to simulate astronomic tides under present (circa 2005), and future conditions (circa 2050 and 2100). The model is modified with specific SLR scenarios, morphology, and shorelines that represent the conditions at each of the time periods. Future sea levels for the years 2050 and 2100 are determined using the Parris et al. (2012) projections. To make projections of future morphology, a Bayesian Network (BN) is implemented. The BN is used to define relationships between forcing mechanisms and coastal responses based on long-term relative SLR, mean wave height, long-term shoreline change rates, mean tidal range, geomorphic setting and coastal slope. Probabilistic predictions of future shoreline positions and dune heights are developed for each SLR scenario for the years 2050 and 2100. The Digital Elevation Model (DEM) is then updated to reflect the future morphologic changes. Comparison of present and future conditions illustrates the hydrodynamic response of the system to the changing landscape. Changes in variables such as harmonic tidal constituents, tidal range, tidal prism, tidal datums, circulation patterns and inundation areas are examined. This provides a better understanding of the physical processes of the current state of the NGOM and gives insight into how future SLR and coastal landscape changes may affect hydrodynamics within the NGOM estuary systems.

Classifying terrestrial surface water systems using integrated residence time

NASA Astrophysics Data System (ADS)

Jones, Allan; Hodges, Ben; McClelland, James; Hardison, Amber; Moffett, Kevan

2017-04-01

Linkages between ecology and hydrology in terrestrial surface water often invoke a discussion of lentic (reservoir) vs. lotic (riverine) system behaviors. However, the literature shows a wide range of thresholds separating lentic/lotic regimes and little agreement on a quantitative, repeatable classification metric that can be broadly and reliably applied across a range of systems hosting various flow regimes and suspended/benthic taxa. We propose an integrated Residence Time (iTR) metric as part of a new Freshwater Continuum Classification (FCC) to address this issue. The iTR is computed as the transit time of a water parcel across a system given observed temporal variations in discharge and volume, which creates a temporally-varying metric applicable across a defined system length. This approach avoids problems associated with instantaneous residence times or average residence times that can lead to misleading characterizations in seasonally- or episodically-dynamic systems. The iTR can be directly related to critical flow thresholds and timescales of ecology (e.g., zooplankton growth). The FCC approach considers lentic and lotic to be opposing end-members of a classification continuum and also defines intermediate regimes that blur the line between the two ends of the spectrum due to more complex hydrological system dynamics. We also discover the potential for "oscillic" behavior, where a system switches between lentic and lotic classifications either episodically or regularly (e.g., seasonally). Oscillic behavior is difficult to diagnose with prior lentic/lotic classification schemes, but can be readily identified using iTR. The FCC approach was used to analyze 15 tidally-influenced river segments along the Texas (USA) coast of the Gulf of Mexico. The results agreed with lentic/lotic designations using prior approaches, but also identified more nuanced intermediate and oscillic regimes. Within this set of systems, the oscillic nature of some of the river reaches was due to flash floods that temporarily turned the primarily lentic stream reaches into lotic systems (not dominantly due to tidal influences). Because the FCC approach is based on system volume and flow characteristics, it is broadly applicable across an entire river reach, pond, or reservoir volume, and so may provide a useful and quantitative common reference point for hydrological and ecological studies going forward. [This work was supported in part by the United States National Science Foundation under grant number 1417433.

User-Friendly Predictive Modeling of Greenhouse Gas (GHG) Fluxes and Carbon Storage in Tidal Wetlands

NASA Astrophysics Data System (ADS)

Ishtiaq, K. S.; Abdul-Aziz, O. I.

2015-12-01

We developed user-friendly empirical models to predict instantaneous fluxes of CO2 and CH4 from coastal wetlands based on a small set of dominant hydro-climatic and environmental drivers (e.g., photosynthetically active radiation, soil temperature, water depth, and soil salinity). The dominant predictor variables were systematically identified by applying a robust data-analytics framework on a wide range of possible environmental variables driving wetland greenhouse gas (GHG) fluxes. The method comprised of a multi-layered data-analytics framework, including Pearson correlation analysis, explanatory principal component and factor analyses, and partial least squares regression modeling. The identified dominant predictors were finally utilized to develop power-law based non-linear regression models to predict CO2 and CH4 fluxes under different climatic, land use (nitrogen gradient), tidal hydrology and salinity conditions. Four different tidal wetlands of Waquoit Bay, MA were considered as the case study sites to identify the dominant drivers and evaluate model performance. The study sites were dominated by native Spartina Alterniflora and characterized by frequent flooding and high saline conditions. The model estimated the potential net ecosystem carbon balance (NECB) both in gC/m2 and metric tonC/hectare by up-scaling the instantaneous predicted fluxes to the growing season and accounting for the lateral C flux exchanges between the wetlands and estuary. The entire model was presented in a single Excel spreadsheet as a user-friendly ecological engineering tool. The model can aid the development of appropriate GHG offset protocols for setting monitoring plans for tidal wetland restoration and maintenance projects. The model can also be used to estimate wetland GHG fluxes and potential carbon storage under various IPCC climate change and sea level rise scenarios; facilitating an appropriate management of carbon stocks in tidal wetlands and their incorporation into a potential carbon market.

Estimates of the dissipative heat and axial torque generated by ocean tides on icy satellites in the outer solar system.

NASA Astrophysics Data System (ADS)

Tyler, R.

2012-09-01

The tidal flow response generated in a satellite ocean depends strongly on the ocean configuration parameters as these parameters control the form and frequencies of the ocean's natural modes of oscillation; if there is a near match between the form and frequency of one of these natural modes and that of one of the available tidal forcing constituents, the ocean can be resonantly excited, producing a strong tidal response. The fundamental elements of the response are described by the tidal flow and surface fluctuations. Derivative elements of the response include the associated dissipative heat, stress, and forces/torques. The dissipative heat has received much previous attention as it may be important in explaining the heat budget on several of the satellites in the Outer Solar System. While these estimates will be reviewed and compared with the tidal dissipation estimates compiled in Hussman et al. (2010), the primary goal in this presentation is to extend the analysis to consider the tidally generated axial torque on the satellites and the potential consquences for rotation. Interestingly, even a synchronously rotating satellite will, if a global fluid layer is included, experience a complex set of opportunities for torques in both the prograde and retrograde sense. The amplitude and sense of the torque sensitively depends on the ocean parameters controlling the tidal response. This sensitivity, combined with expected feedbacks whereby the tides affect the orbital parameters, suggests that the evolution of the satellite system will experience phases of both prograde and retrograde tidal torques during its evolution. A related point is that parameters of the ocean might be inferred from inferences or observations of torque or rotational deviations. In the panels to the right we show the nondimensional tidal torques associated with obliquity (top) and eccentricity (bottom). The parameters described in the labeling are the fluid density ρ, surface gravity g, ocean surface area A, tidal equilibrium height ηF, dissipation quality factor Q,and c=(gh)1/2, cr=Ωa, with ocean thickness h, rotation rate Ω, and radius a. Torque due to tides forced by obliquity as a function of the parameters c/cr and Q. Retrograde ("Westward") and prograde ("Eastward") components shown in left and right panels, respectively. Log10 scale shown in colorbar.

Morphologic and hydrodynamic controls on the occurrence of tidal bundles in an open-coast macrotidal environment, northern Gyeonggi Bay, west coast of Korea

NASA Astrophysics Data System (ADS)

Choi, Kyungsik; Kim, Do Hyeong

2016-06-01

Tidal dunes with well-defined rhythmic tidal bundles are documented from the lower intertidal zone of an open-coast macrotidal environment in Gyeonggi Bay, Korea. Based on combined morphologic, sedimentologic and hydrodynamic datasets, this study aims to characterize the factors that govern the temporal and spatial variability of tidal bundles in a non-barred, unconfined macrotidal environment. The tidal dunes are flood-asymmetric and of longer wavelength (10-20 m) with small ebb caps on the upper bank, and symmetric to slightly ebb-asymmetric and of shorter wavelength (5-10 m) with larger ebb caps on the lower bank. The upper-bank dunes are characterized by more steeply dipping flood-directed planar cross-beds and thinner mud drapes than the lower-bank dunes. Each tidal bundle consists of a single mud drape that is stratified to cross-stratified, rich in silt and very fine sand. It overlies ebb-directed ripples and represents dynamic mud deposition during the ebb tidal phase. The presence of strong rotary currents (up to 0.25 m/s) and low suspended-sediment concentration of flood currents prevent deposition of mud drapes during the high-tide slack-water period. The distinct asymmetry in the water elevation at which the velocity peaks during the ebb and flood phases results in the preferential preservation of flood-directed cross-beds in the lower intertidal zone, where the ebb current - although stronger than the flood currents - is of shorter duration and hence unable to reverse the dune profile. The pronounced time-velocity asymmetry at the higher elevation combined with the distinct velocity peak asymmetry leads to a better preservation of hierarchical tidal cycles in the upper-bank dunes. The present study suggests that the persistent occurrence of single, stratified to cross-stratified mud drapes, which reflect dynamic mud deposition during the ebb phase, and the dominance of flood-directed cross-beds are diagnostic features of tidal bundles in the intertidal zone of unbarred, open-coast macrotidal environments. A proposed model for mud drape deposition provides a new perspective on the origin of tidal bundles together with useful criteria for reconstructing the paleo-depositional setting.

National Trauma Institute: A National Coordinating Center for Trauma Research Funding

DTIC Science & Technology

2016-12-01

comparing the effectiveness of modern ventilator modalities upon patients with ARDS/ALI does not exist. Low-tidal volume ventilation (ARDSNet...associated with better oxygenation , less sedative usage, and less ventilator -associated pneumonia compared with other ventilator modes. However, questions...hypercoagulable at baseline, and that further investigations into the effects of platelet activation and obesity, time-to-enoxaparin administration, and

43 CFR Appendix II to Part 11 - Format for Data Inputs and Modifications to the NRDAM/CME

Code of Federal Regulations, 2010 CFR

2010-10-01

... of water that does not contain vegetation (e.g., wetland, seagrass, or kelp) or invertebrate reef (e... kelp) or invertebrate reef (e.g., coral reef) and is classified as “seaward” in Table 6.2, Volume I of..., seagrass, or kelp) or invertebrate reef (e.g., coral reef). Tidal current—currents caused by alternating...

Breathing response of the tegu lizard to 1-4% CO2 in the mouth and nose or inspired into the lungs.

PubMed

Ballam, G O

1985-12-01

This study investigated the influence on ventilation of elevated CO2 in the nasal and buccal cavities (NaBuCO2) vs the effect of elevated CO2 levels inspired into the lungs (LuCO2). Separate gas sources were used to independently alter NaBuCO2 and LuCO2. As little as 1% NaBuCO2 or LuCO2 significantly increased the pause duration between the active expiratory-inspiratory cycles. Elevated NaBuCO2 caused minor changes in tidal volume, mean inspiratory and expiratory flow, and inspiratory and expiratory durations with a significant reduction in total ventilation. Elevated LuCO2 had little effect on inspiratory or expiratory durations but unlike CO2 in the upper airways, significantly increased tidal volume and mean inspiratory and expiratory flows. This study demonstrates that the increased pause duration seen in the tegu lizard to elevated environmental CO2 is due to a receptor response in the buccal or nasal cavities and also to elevated CO2 concentrations inspired into the lungs. Sensitivity of the ventilatory responses to CO2 in the upper airways is well within a physiologically relevant range.

Human sinus arrhythmia as an index of vagal cardiac outflow

NASA Technical Reports Server (NTRS)

Eckberg, D. L.

1983-01-01

The human central vagal mechanisms were investigated by measuring the intervals between heartbeats during controlled breathing (at breathing intervals of 2.5-10 s and nominal tidal volumes of 1000 and 1500 ml) in six young men and women. It was found that as the breathing interval increased, the longest heart periods became longer, the shortest heart periods became shorter, and the peak-valley P-P intervals increased asymptotically. Peak-valley intervals also increased in proportion to tidal volume, although this influence was small. The phase angles between heart period changes and respiration were found to vary as linear functions of breathing interval. Heart period shortening began in inspiration at short breathing intervals and in expiration at long breathing intervals, while heart period lengthening began in early expiration at all breathing intervals studied. It is concluded that a close relationship exists between variations of respiratory depth and interval and the quantity, periodicity, and timing of vagal cardiac outflow in conscious humans. The results indicate that at usual breathing rates, phasic respiration-related changes of vagal motoneuron activity begin in expiration, progress slowly, and are incompletely expressed at fast breathing ratges.

Propranolol blocks the stimulatory effects of naloxone on ventilation and oxygen consumption in hamsters.

PubMed

Schlenker, E H; Eikanger, J

1997-06-01

The purposes of these studies were: 1) to determine the effects of various doses of propranolol, a nonspecific beta-adrenergic antagonist, on ventilation, oxygen consumption, and body temperature in hamsters, and 2) to test the hypothesis that in hamsters the stimulatory effects of naloxone, an opioid receptor antagonist, on ventilation and oxygen consumption occur, at least in part, through the release of catecholamines that act via beta-adrenergic receptors. Propranolol, a non-specific beta adrenergic receptor antagonist, at a 20 mg/kg depressed body temperature, oxygen consumption, tidal volume, and ventilation relative to saline. The lower dose of 10 mg/kg had only transitory effects on tidal volume at 60 min and ventilation at 30 min post-injection-Naloxone (1 mg/kg) relative to saline stimulated ventilation and oxygen consumption. These effects were blocked by propranolol pretreatment. The results of these experiments demonstrate that in the hamster, 1) body temperature, oxygen consumption, and ventilation appear to be modulated by beta-adrenergic receptors, and 2) the stimulatory effects of naloxone on oxygen consumption and ventilation may occur through the interaction of endogenous opioids and beta-adrenergic receptor systems.