40 CFR 62.14690 - What monitoring equipment must I install and what parameters must I monitor?

Code of Federal Regulations, 2012 CFR

2012-07-01

... each baghouse compartment or cell. For negative pressure or induced air fabric filters, the bag leak... ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) APPROVAL AND PROMULGATION OF STATE PLANS... subpart, you must install, calibrate, maintain, and continuously operate a bag leak detection system as...

40 CFR 62.14690 - What monitoring equipment must I install and what parameters must I monitor?

Code of Federal Regulations, 2014 CFR

2014-07-01

... each baghouse compartment or cell. For negative pressure or induced air fabric filters, the bag leak... ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) APPROVAL AND PROMULGATION OF STATE PLANS... subpart, you must install, calibrate, maintain, and continuously operate a bag leak detection system as...

40 CFR 62.14690 - What monitoring equipment must I install and what parameters must I monitor?

Code of Federal Regulations, 2013 CFR

2013-07-01

... each baghouse compartment or cell. For negative pressure or induced air fabric filters, the bag leak... ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) APPROVAL AND PROMULGATION OF STATE PLANS... subpart, you must install, calibrate, maintain, and continuously operate a bag leak detection system as...

29 CFR 1915.1001 - Asbestos.

Code of Federal Regulations, 2010 CFR

2010-07-01

... ACM from straight runs of piping and elbows and other connections with the following specifications... or other device used to prevent collapse of bag during removal shall run continually during the... pressure glove box systems. Negative pressure glove boxes may be used to remove ACM or PACM from pipe runs...

29 CFR 1915.1001 - Asbestos.

Code of Federal Regulations, 2014 CFR

2014-07-01

... ACM from straight runs of piping and elbows and other connections with the following specifications... or other device used to prevent collapse of bag during removal shall run continually during the... pressure glove box systems. Negative pressure glove boxes may be used to remove ACM or PACM from pipe runs...

29 CFR 1915.1001 - Asbestos.

Code of Federal Regulations, 2013 CFR

2013-07-01

... ACM from straight runs of piping and elbows and other connections with the following specifications... or other device used to prevent collapse of bag during removal shall run continually during the... pressure glove box systems. Negative pressure glove boxes may be used to remove ACM or PACM from pipe runs...

29 CFR 1915.1001 - Asbestos.

Code of Federal Regulations, 2012 CFR

2012-07-01

... ACM from straight runs of piping and elbows and other connections with the following specifications... or other device used to prevent collapse of bag during removal shall run continually during the... pressure glove box systems. Negative pressure glove boxes may be used to remove ACM or PACM from pipe runs...

29 CFR 1915.1001 - Asbestos.

Code of Federal Regulations, 2011 CFR

2011-07-01

... ACM from straight runs of piping and elbows and other connections with the following specifications... or other device used to prevent collapse of bag during removal shall run continually during the... pressure glove box systems. Negative pressure glove boxes may be used to remove ACM or PACM from pipe runs...

Neural control of vascular reactions: impact of emotion and attention.

PubMed

Okon-Singer, Hadas; Mehnert, Jan; Hoyer, Jana; Hellrung, Lydia; Schaare, Herma Lina; Dukart, Juergen; Villringer, Arno

2014-03-19

This study investigated the neural regions involved in blood pressure reactions to negative stimuli and their possible modulation by attention. Twenty-four healthy human subjects (11 females; age = 24.75 ± 2.49 years) participated in an affective perceptual load task that manipulated attention to negative/neutral distractor pictures. fMRI data were collected simultaneously with continuous recording of peripheral arterial blood pressure. A parametric modulation analysis examined the impact of attention and emotion on the relation between neural activation and blood pressure reactivity during the task. When attention was available for processing the distractor pictures, negative pictures resulted in behavioral interference, neural activation in brain regions previously related to emotion, a transient decrease of blood pressure, and a positive correlation between blood pressure response and activation in a network including prefrontal and parietal regions, the amygdala, caudate, and mid-brain. These effects were modulated by attention; behavioral and neural responses to highly negative distractor pictures (compared with neutral pictures) were smaller or diminished, as was the negative blood pressure response when the central task involved high perceptual load. Furthermore, comparing high and low load revealed enhanced activation in frontoparietal regions implicated in attention control. Our results fit theories emphasizing the role of attention in the control of behavioral and neural reactions to irrelevant emotional distracting information. Our findings furthermore extend the function of attention to the control of autonomous reactions associated with negative emotions by showing altered blood pressure reactions to emotional stimuli, the latter being of potential clinical relevance.

The estimated sensitivity and specificity of compartment pressure monitoring for acute compartment syndrome.

PubMed

McQueen, Margaret M; Duckworth, Andrew D; Aitken, Stuart A; Court-Brown, Charles M

2013-04-17

The aim of our study was to document the estimated sensitivity and specificity of continuous intracompartmental pressure monitoring for the diagnosis of acute compartment syndrome. From our prospective trauma database, we identified all patients who had sustained a tibial diaphyseal fracture over a ten-year period. A retrospective analysis of 1184 patients was performed to record and analyze the documented use of continuous intracompartmental pressure monitoring and the use of fasciotomy. A diagnosis of acute compartment syndrome was made if there was escape of muscles at fasciotomy and/or color change in the muscles or muscle necrosis intraoperatively. A diagnosis of acute compartment syndrome was considered incorrect if it was possible to close the fasciotomy wounds primarily at forty-eight hours. The absence of acute compartment syndrome was confirmed by the absence of neurological abnormality or contracture at the time of the latest follow-up. Of 979 monitored patients identified, 850 fit the inclusion criteria with a mean age of thirty-eight years (range, twelve to ninety-four years), and 598 (70.4%) were male (p < 0.001). A total of 152 patients (17.9%) underwent fasciotomy for the treatment of acute compartment syndrome: 141 had acute compartment syndrome (true positives), six did not have it (false positives), and five underwent fasciotomy despite having a normal differential pressure reading, with subsequent operative findings consistent with acute compartment syndrome (false negatives). Of the 698 patients (82.1%) who did not undergo fasciotomy, 689 had no evidence of any late sequelae of acute compartment syndrome (true negatives) at a mean follow-up time of fifty-nine weeks. The estimated sensitivity of intracompartmental pressure monitoring for suspected acute compartment syndrome was 94%, with an estimated specificity of 98%, an estimated positive predictive value of 93%, and an estimated negative predictive value of 99%. The estimated sensitivity and specificity of continuous intracompartmental pressure monitoring for the diagnosis of acute compartment syndrome following tibial diaphyseal fracture are high; continuous intracompartmental pressure monitoring should be considered for patients at risk for acute compartment syndrome.

Regulation of landslide motion by dilatancy and pore pressure feedback

USGS Publications Warehouse

Iverson, R.M.

2005-01-01

A new mathematical model clarifies how diverse styles and rates of landslide motion can result from regulation of Coulomb friction by dilation or contraction of water-saturated basal shear zones. Normalization of the model equations shows that feedback due to coupling between landslide motion, shear zone volume change, and pore pressure change depends on a single dimensionless parameter ??, which, in turn, depends on the dilatancy angle ?? and the intrinsic timescales for pore pressure generation and dissipation. If shear zone soil contracts during slope failure, then ?? 0, and negative feedback permits slow, steady landslide motion to occur while positive pore pressure is supplied by rain infiltration. Steady state slip velocities v0 obey v0 = -(K/??) p*e, where K is the hydraulic conductivity and p*e is the normalized (dimensionless) negative pore pressure generated by dilation. If rain infiltration and attendant pore pressure growth continue unabated, however, their influence ultimately overwhelms the stabilizing influence of negative p*e. Then, unbounded landslide acceleration occurs, accentuated by an instability that develops if ?? diminishes as landslide motion proceeds. Nonetheless, numerical solutions of the model equations show that slow, nearly steady motion of a clay-rich landslide may persist for many months as a result of negative pore pressure feedback that regulates basal Coulomb friction. Similarly stabilized motion is less likely to occur in sand-rich landslides that are characterized by weaker negative feedback.

Cervical spine disease may result in a negative lumbar spinal drainage trial in normal pressure hydrocephalus: case report.

PubMed

Komotar, Ricardo J; Zacharia, Brad E; Mocco, J; Kaiser, Michael G; Frucht, Stephen J; McKhann, Guy M

2008-10-01

In this case report, we present a patient with normal pressure hydrocephalus in whom a lumbar drainage trial yielded a false-negative result secondary to cervical spondylosis. An 80-year-old woman presented with classic symptoms of normal pressure hydrocephalus as well as evidence of cervical myelopathy. Magnetic resonance imaging of the brain and spine showed enlarged ventricles and single-level cervical canal narrowing. An initial lumbar drainage trial was performed, which revealed negative results. The patient then underwent cervical decompression and fusion. Despite this procedure, the patient's symptoms continued to worsen. A repeat lumbar drainage trial was performed with positive results. Subsequently, a ventriculoperitoneal shunt was placed, resulting in significant improvement of her symptoms. This case report illustrates how altered cerebrospinal fluid flow dynamics may impact the accuracy of the lumbar spinal drainage trial in patients with normal pressure hydrocephalus.

Magnetization and Hall effect under high pressure in NaV 6O 11

NASA Astrophysics Data System (ADS)

Naka, T.; Matsumoto, T.; Kanke, Y.; Murata, K.

1995-02-01

We have investigated the pressure dependences of magnetization and the Hall coefficient in the ferromagnetic vanadium oxide NaV 6O 11 up to 1.2 GPa. Structural transitions (hexagonal-hexagonal-orthorhombic) occur at TH = 245 K and TL = 35 K at ambient pressure. Meanwhile, the susceptibility obeys the Curie-Weiss law X = C/( T - θ) with antiferromagnetic correlation of θ < 0 at T > TH, with ferromagnetic correlation of θ < 0 at T < TH. The spontaneous magnetization appears below Tc = 64.2 K. With increasing pressure, Tc and magnetization M( T < Tc) decrease, while TH increases. The sign of the Hall coefficient changes continuously (negative-positive-negative) at around T ≈ 170 K and 75 K.

Randomized clinical trial to compare negative-pressure wound therapy approaches with low and high pressure, silicone-coated dressing, and polyurethane foam dressing.

PubMed

Lavery, Lawrence A; La Fontaine, Javier; Thakral, Gaurav; Kim, Paul J; Bhavan, Kavita; Davis, Kathryn E

2014-03-01

This study was designed to compare two approaches to negative-pressure wound therapy: 125-mmHg pressure with a polyurethane foam dressing and 75-mmHg pressure with a silicone-coated dressing. Forty patients with diabetic foot wounds, after incision and drainage or amputation for infection, were assigned randomly to negative-pressure wound therapy with 75-mmHg continuous pressure with a silicone-covered dressing (75-mmHg group) or 125-mmHg with a polyurethane foam dressing (125-mmHg group) for up to 4 weeks or until surgical closure. There was no difference in the proportion of wounds that were closed surgically (75-mmHg group, 50 percent; 125-mmHg group, 60 percent), wounds that demonstrated 50 percent wound area reduction (75-mmHg group, 65 percent; 125-mmHg group, 80 percent), or wounds that demonstrated 50 percent wound volume reduction after 4 weeks of therapy (75-mmHg group, 95 percent; 125-mmHg group, 90 percent). The authors' results suggest that there was no difference in outcomes in wounds treated with low pressure (75 mmHg) with a silicone-coated interface and high pressure (125 mmHg) with a polyurethane foam interface. Therapeutic, II.

Spinal cord injury pressure ulcer treatment: an experience-based approach.

PubMed

Sunn, Gabriel

2014-08-01

Pressure ulcers continue to impact the lives of spinal cord injury patients severely. Pressure ulcers must be accurately staged according to National Pressure Ulcer Advisory recommendations before treatment design. The first priority in treatment of pressure ulcers is offloading. Intact skin ulcers may be treated with noncontact nonthermal low-frequency ultrasound. Superficial pressure ulcers may be treated with a combination of collagenase and foam dressings. Deeper pressure ulcers warrant negative-pressure wound therapy dressings along with biologic adjuncts to fill in wound depth. Discovery and treatment of osteomyelitis is a high priority when initially evaluating pressure ulcers. Surgical intervention must always be considered. Published by Elsevier Inc.

High pressure vaginography to diagnose vaginal ureteral ectopia in patients with continuous urinary incontinence.

PubMed

Zuckerman, Jack M; Shekarriz, Bijan; Upadhyay, Jyoti

2013-02-01

Continuous urinary incontinence in female patients can be a diagnostic dilemma if traditional imaging fails to identify a source. Vaginography has been used to diagnose vaginal ectopic ureters in the past with mixed results. Institutional review board approval was obtained for a retrospective review. Five teenage females with continuous incontinence and prior negative imaging work ups underwent high pressure vaginography. Their findings and treatment outcomes are reviewed. A vaginal ectopic ureter was diagnosed in each of the five patients at a mean age 15.8 years. Each had undergone prior magnetic resonance urography that was non-diagnostic. Four of the five were managed surgically with resolution of their incontinence. One was lost to follow up. High pressure vaginogram should be considered during the work up of female patients with continuous urinary incontinence, especially when other imaging modalities fail to identify an etiology.

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.

[POSSIBILITIES OF VACUUM THERAPY APPLICATION IN DISORDERS OF VENOUS OUTFLOW IN ISLET GRAFTS].

PubMed

Badyul, P O; Samoylenko, G E; Nor, N M; Slesarenko, K S

2015-07-01

The experience of "distressed" (problematic) flaps application in 33 patients with soft tissue defects over 2010-2014 years were analysed. It was proposed to use the local negative pressure for the prevention and treatment of complications associated with venous insufficiency or trombosis in using of plastics with vascularised complexes of tissues. Vacuum-therapy was conducted with the help of negative pressure apparatus "AGATE-Dnepr" (Ukraine) by attaching silver-containing polyurethane sponge on the operating zone, covering the flap with the surrounding skin netting band "Grassolind". The recommended standard of negative pressure of 75-125 mm Hg, both in impulse and in continuous mode was used. The high efficiency of vacuum-therapy for survival of grafts has been demonstrated. Thus, it might be considered as an effective element of prevention and treatment of complications associated with venous insufficiency or trombosis using of vascularised tissue complex plastics of defects.

Automated electronic monitoring of circuit pressures during continuous renal replacement therapy: a technical report.

PubMed

Zhang, Ling; Baldwin, Ian; Zhu, Guijun; Tanaka, Aiko; Bellomo, Rinaldo

2015-03-01

Automated electronic monitoring and analysis of circuit pressures during continuous renal replacement therapy (CRRT) has the potential to predict failure and allow intervention to optimise function. Current CRRT machines can measure and store pressure readings for downloading into databases and for analysis. We developed a procedure to obtain such data at intervals of 1 minute and analyse them using the Prismaflex CRRT machine, and we present an example of such analysis. We obtained data on pressures obtained at intervals of 1 minute in a patient with acute kidney injury and sepsis treated with continuous haemofiltration at 2 L/hour of ultrafiltration and a blood flow of 200 mL/minute. Data analysis identified progressive increases in transmembrane pressure (TMP) and prefilter pressure (PFP) from time 0 until 33 hours or clotting. TMP increased from 104 mmHg to 313 mmHg and PFP increased from from 131 mmHg to 185 mmHg. Effluent pressure showed a progressive increase in the negative pressure applied to achieve ultrafiltration from 0 mmHg to -168 mmHg. The inflection point for such changes was also identified. Blood pathway pressures for access and return remained unchanged throughout. Automated electronic monitoring of circuit pressure during CRRT is possible and provides useful information on the evolution of circuit clotting.

Rate of rise in diastolic blood pressure influences vascular sympathetic response to mental stress.

PubMed

El Sayed, Khadigeh; Macefield, Vaughan G; Hissen, Sarah L; Joyner, Michael J; Taylor, Chloe E

2016-12-15

Research indicates that individuals may experience a rise (positive responders) or fall (negative responders) in muscle sympathetic nerve activity (MSNA) during mental stress. In this study, we examined the early blood pressure responses (including the peak, time of peak and rate of rise in blood pressure) to mental stress in positive and negative responders. Negative MSNA responders to mental stress exhibit a more rapid rise in diastolic pressure at the onset of the stressor, suggesting a baroreflex-mediated suppression of MSNA. In positive responders there is a more sluggish rise in blood pressure during mental stress, which appears to be MSNA-driven. This study suggests that whether MSNA has a role in the pressor response is dependent upon the reactivity of blood pressure early in the task. Research indicates that individuals may experience a rise (positive responders) or fall (negative responders) in muscle sympathetic nerve activity (MSNA) during mental stress. The aim was to examine the early blood pressure response to stress in positive and negative responders and thus its influence on the direction of change in MSNA. Blood pressure and MSNA were recorded continuously in 21 healthy young males during 2 min mental stressors (mental arithmetic, Stroop test) and physical stressors (cold pressor, handgrip exercise, post-exercise ischaemia). Participants were classified as negative or positive responders according to the direction of the mean change in MSNA during the stressor tasks. The peak changes, time of peak and rate of changes in blood pressure were compared between groups. During mental arithmetic negative responders experienced a significantly greater rate of rise in diastolic blood pressure in the first minute of the task (1.3 ± 0.5 mmHg s -1 ) compared with positive responders (0.4 ± 0.1 mmHg s -1 ; P = 0.03). Similar results were found for the Stroop test. Physical tasks elicited robust parallel increases in blood pressure and MSNA across participants. It is concluded that negative MSNA responders to mental stress exhibit a more rapid rise in diastolic pressure at the onset of the stressor, suggesting a baroreflex-mediated suppression of MSNA. In positive responders there is a more sluggish rise in blood pressure during mental stress, which appears to be MSNA-driven. This study suggests that whether MSNA has a role in the pressor response is dependent upon the reactivity of blood pressure early in the task. © 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.

Rate of rise in diastolic blood pressure influences vascular sympathetic response to mental stress

PubMed Central

El Sayed, Khadigeh; Macefield, Vaughan G.; Hissen, Sarah L.; Joyner, Michael J.

2016-01-01

Key points Research indicates that individuals may experience a rise (positive responders) or fall (negative responders) in muscle sympathetic nerve activity (MSNA) during mental stress.In this study, we examined the early blood pressure responses (including the peak, time of peak and rate of rise in blood pressure) to mental stress in positive and negative responders.Negative MSNA responders to mental stress exhibit a more rapid rise in diastolic pressure at the onset of the stressor, suggesting a baroreflex‐mediated suppression of MSNA. In positive responders there is a more sluggish rise in blood pressure during mental stress, which appears to be MSNA‐driven.This study suggests that whether MSNA has a role in the pressor response is dependent upon the reactivity of blood pressure early in the task. Abstract Research indicates that individuals may experience a rise (positive responders) or fall (negative responders) in muscle sympathetic nerve activity (MSNA) during mental stress. The aim was to examine the early blood pressure response to stress in positive and negative responders and thus its influence on the direction of change in MSNA. Blood pressure and MSNA were recorded continuously in 21 healthy young males during 2 min mental stressors (mental arithmetic, Stroop test) and physical stressors (cold pressor, handgrip exercise, post‐exercise ischaemia). Participants were classified as negative or positive responders according to the direction of the mean change in MSNA during the stressor tasks. The peak changes, time of peak and rate of changes in blood pressure were compared between groups. During mental arithmetic negative responders experienced a significantly greater rate of rise in diastolic blood pressure in the first minute of the task (1.3 ± 0.5 mmHg s−1) compared with positive responders (0.4 ± 0.1 mmHg s−1; P = 0.03). Similar results were found for the Stroop test. Physical tasks elicited robust parallel increases in blood pressure and MSNA across participants. It is concluded that negative MSNA responders to mental stress exhibit a more rapid rise in diastolic pressure at the onset of the stressor, suggesting a baroreflex‐mediated suppression of MSNA. In positive responders there is a more sluggish rise in blood pressure during mental stress, which appears to be MSNA‐driven. This study suggests that whether MSNA has a role in the pressor response is dependent upon the reactivity of blood pressure early in the task. PMID:27690366

Phase behavior of metastable liquid silicon at negative pressure: Ab initio molecular dynamics

NASA Astrophysics Data System (ADS)

Zhao, G.; Yu, Y. J.; Yan, J. L.; Ding, M. C.; Zhao, X. G.; Wang, H. Y.

2016-04-01

Extensive first-principle molecular dynamics simulations are performed to study the phase behavior of metastable liquid Si at negative pressure. Our results show that the high-density liquid (HDL) and HDL-vapor spinodals indeed form a continuous reentrant curve and the liquid-liquid critical point seems to just coincide with its minimum. The line of density maxima also has a strong tendency to pass through this minimum. The phase behaviour of metastable liquid Si therefore tends to be a critical-point-free scenario rather than a second-critical-point one based on SW potential.

40 CFR 63.1184 - What do I need to know about the design specifications, installation, and operation of a bag leak...

Code of Federal Regulations, 2013 CFR

2013-07-01

..., each compartment or cell must have a bag leak detector. For a negative-pressure or induced-air fabric... design specifications, installation, and operation of a bag leak detection system? 63.1184 Section 63.1184 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED...

40 CFR 63.1184 - What do I need to know about the design specifications, installation, and operation of a bag leak...

Code of Federal Regulations, 2014 CFR

2014-07-01

..., each compartment or cell must have a bag leak detector. For a negative-pressure or induced-air fabric... design specifications, installation, and operation of a bag leak detection system? 63.1184 Section 63.1184 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED...

40 CFR 63.1184 - What do I need to know about the design specifications, installation, and operation of a bag leak...

Code of Federal Regulations, 2012 CFR

2012-07-01

..., each compartment or cell must have a bag leak detector. For a negative-pressure or induced-air fabric... design specifications, installation, and operation of a bag leak detection system? 63.1184 Section 63.1184 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED...

A Graphical Method for Estimation of Barometric Efficiency from Continuous Data - Concepts and Application to a Site in the Piedmont, Air Force Plant 6, Marietta, Georgia

USGS Publications Warehouse

Gonthier, Gerard

2007-01-01

A graphical method that uses continuous water-level and barometric-pressure data was developed to estimate barometric efficiency. A plot of nearly continuous water level (on the y-axis), as a function of nearly continuous barometric pressure (on the x-axis), will plot as a line curved into a series of connected elliptical loops. Each loop represents a barometric-pressure fluctuation. The negative of the slope of the major axis of an elliptical loop will be the ratio of water-level change to barometric-pressure change, which is the sum of the barometric efficiency plus the error. The negative of the slope of the preferred orientation of many elliptical loops is an estimate of the barometric efficiency. The slope of the preferred orientation of many elliptical loops is approximately the median of the slopes of the major axes of the elliptical loops. If water-level change that is not caused by barometric-pressure change does not correlate with barometric-pressure change, the probability that the error will be greater than zero will be the same as the probability that it will be less than zero. As a result, the negative of the median of the slopes for many loops will be close to the barometric efficiency. The graphical method provided a rapid assessment of whether a well was affected by barometric-pressure change and also provided a rapid estimate of barometric efficiency. The graphical method was used to assess which wells at Air Force Plant 6, Marietta, Georgia, had water levels affected by barometric-pressure changes during a 2003 constant-discharge aquifer test. The graphical method was also used to estimate barometric efficiency. Barometric-efficiency estimates from the graphical method were compared to those of four other methods: average of ratios, median of ratios, Clark, and slope. The two methods (the graphical and median-of-ratios methods) that used the median values of water-level change divided by barometric-pressure change appeared to be most resistant to error caused by barometric-pressure-independent water-level change. The graphical method was particularly resistant to large amounts of barometric-pressure-independent water-level change, having an average and standard deviation of error for control wells that was less than one-quarter that of the other four methods. When using the graphical method, it is advisable that more than one person select the slope or that the same person fits the same data several times to minimize the effect of subjectivity. Also, a long study period should be used (at least 60 days) to ensure that loops affected by large amounts of barometric-pressure-independent water-level change do not significantly contribute to error in the barometric-efficiency estimate.

Renal effects of continuous negative pressure breathing

NASA Technical Reports Server (NTRS)

Kinney, M. J.; Discala, V. A.

1975-01-01

Continuous negative pressure breathing (CNPB) was utilized to simulate the thoracic vascular distension of zero g or space, in 11 anesthetized rats. The animals underwent renal clearance and micropuncture renal nephron studies before, during, and after CNPB. Rats were pretreated with a high salt diet and I-M desoxycorticosterone (DOCA) in excess. None of these rats diuresed with CNPB. In contrast 5 of the 7 remaining rats increased the fraction of the filtered sodium excreted (C sub Na/GFR, p .05) and their urinary flow rate (V, p .05). Potassium excretion increased (U sub k V, p .05). End proximal tubular fluid specimen's TF/P inulin ratios were unchanged. Whole kidney and single nephron glomerular filtration rates fell 10%. CNPB, a mechanism for atrial distension, appears to cause, in rats, a decrease in distal tubular sodium, water and potassium reabsorption. Exogenous mineral-corticoid prevents the diuresis, saluresis, and kaluresis.

Differential effects of lower body negative pressure and upright tilt on splanchnic blood volume

PubMed Central

Taneja, Indu; Moran, Christopher; Medow, Marvin S.; Glover, June L.; Montgomery, Leslie D.; Stewart, Julian M.

2015-01-01

Upright posture and lower body negative pressure (LBNP) both induce reductions in central blood volume. However, regional circulatory responses to postural changes and LBNP may differ. Therefore, we studied regional blood flow and blood volume changes in 10 healthy subjects undergoing graded lower-body negative pressure (−10 to −50 mmHg) and 8 subjects undergoing incremental head-up tilt (HUT; 20°, 40°, and 70°) on separate days. We continuously measured blood pressure (BP), heart rate, and regional blood volumes and blood flows in the thoracic, splanchnic, pelvic, and leg segments by impedance plethysmography and calculated regional arterial resistances. Neither LBNP nor HUT altered systolic BP, whereas pulse pressure decreased significantly. Blood flow decreased in all segments, whereas peripheral resistances uniformly and significantly increased with both HUT and LBNP. Thoracic volume decreased while pelvic and leg volumes increased with HUT and LBNP. However, splanchnic volume changes were directionally opposite with stepwise decreases in splanchnic volume with LBNP and stepwise increases in splanchnic volume during HUT. Splanchnic emptying in LBNP models regional vascular changes during hemorrhage. Splanchnic filling may limit the ability of the splanchnic bed to respond to thoracic hypovolemia during upright posture. PMID:17085534

Benchtop evaluation of pressure barrier insufflator and standard insufflator systems.

PubMed

Nepple, Kenneth G; Kallogjeri, Dorina; Bhayani, Sam B

2013-01-01

Previous experimental research has reported minimal differences in pressure maintenance between different versions of standard insufflators (SI). However, a recent report identified potential clinical benefits with a valveless pressure barrier insufflator (PBI). We sought to perform a benchtop objective evaluation of SI and PBI systems. A rigid box system with continuous pressure manometry was used to evaluate a PBI (Surgiquest Airseal) and two SIs (SI1 = Stryker PneumoSure High Flow Insufflator and SI2 = Storz SCB Thermoflator). Pressure maintenance of 15 mmHg was evaluated during experimental conditions of leakage from a 5 mm port site, leakage from a 12 mm port site, and continuous suction. With leakage from the 5 mm port site, the PBI maintained pressure of >13 mmHg whereas the pressures dropped moderately with the SI1 (7-13 mmHg) and SI2 insufflators (3-7 mmHg) and did not regain goal pressure until leakage was stopped. With leakage from 12 mm port site, the PBI pressure decreased to 9-11 mmHg, whereas the SI1 and SI2 lost insufflation pressures completely. The PBI maintained pressure of >11 mmHg during continuous suction while the SI1 and SI2 lost pressure entirely, and actually showed negative pressure from air suction into the rigid box system. When evaluated statistically with the mixed model repeated measures ANOVA, the SI1 and SI2 performed similarly while the PBI maintained increased pressure. In the experimental rigid box system, the PBI more successfully maintained pressure in response to leakage and suction than SIs.

Effect of continuous negative-pressure breathing on skin blood flow during exercise in a hot environment.

PubMed

Nagashima, K; Nose, H; Takamata, A; Morimoto, T

1998-06-01

To assess the impact of continuous negative-pressure breathing (CNPB) on the regulation of skin blood flow, we measured forearm blood flow (FBF) by venous-occlusion plethysmography and laser-Doppler flow (LDF) at the anterior chest during exercise in a hot environment (ambient temperature = 30 degreesC, relative humidity = approximately 30%). Seven male subjects exercised in the upright position at an intensity of 60% peak oxygen consumption rate for 40 min with and without CNPB after 20 min of exercise. The esophageal temperature (Tes) in both conditions increased to 38.1 degreesC by the end of exercise, without any significant differences between the two trials. Mean arterial pressure (MAP) increased by approximately 15 mmHg by 8 min of exercise, without any significant difference between the two trials before CNPB. However, CNPB reduced MAP by approximately 10 mmHg after 24 min of exercise (P < 0.05). The increase in FBF and LDF in the control condition leveled off after 18 min of exercise above a Tes of 37.7 degreesC, whereas in the CNPB trial the increase continued, with a rise in Tes despite the decrease in MAP. These results suggest that CNPB enhances vasodilation of skin above a Tes of approximately 38 degrees C by stretching intrathoracic baroreceptors such as cardiopulmonary baroreceptors.

[The numerical simulation of the internal flow field inside the pressure generator of a continuous positive airway pressure ventilator].

PubMed

Cheng, Yunzhang; Zhu, Lihua; Zhang, Weiguo; Wu, Wenquan

2011-12-01

The problem of noise in ventilator has always been an important topic to study in the development of the ventilator. A great number of data are showing that there are still large gaps of research and application levels in noise control of the ventilator between China and some more advanced foreign countries. In this study, with cooperation of the Shanghai Medical Equipment Limited Liability Company, we used the computational fluid dynamics (CFD), software FLUENT, adopted the standard k-epsilon turbulence model and the SIMPLE algorithm to simulate the inner flow field of the continuous positive airway pressure (CPAP) ventilator's pressure generator. After a detailed analysis, we figured out that there are several deficiencies in this ventilator, like local reflow in volute, uneven velocity distribution and local negative pressure in inlet of the impeller, which easily lead to noise and affect the ventilator's performances. So, it needs to be improved to a certain extent.

The predictive value of external continuous lumbar drainage, with cerebrospinal fluid outflow controlled by medium pressure valve, in normal pressure hydrocephalus.

PubMed

Panagiotopoulos, V; Konstantinou, D; Kalogeropoulos, A; Maraziotis, T

2005-09-01

Although sporadic studies have described temporary external cerebrospinal fluid (CSF) lumbar drainage as a highly accurate test for predicting the outcome after ventricular shunting in normal pressure hydrocephalus (NPH) patients, a more recent study reports that the positive predictive value of external lumbar drainage (ELD) is high but the negative predictive value is deceptively low. Therefore, we conducted a prospective study in order to evaluate the predictive value of a continuous ELD, with CSF outflow controlled by medium pressure valve, in NPH patients. Twenty-seven patients with presumed NPH were admitted to our department and CSF drainage was carried out by a temporary (ELD) with CSF outflow controlled by a medium pressure valve for five days. All patients received a ventriculoperitoneal shunt using a medium pressure valve based upon preoperative clinical and radiographic criteria of NPH, regardless of ELD outcome. Clinical evaluation of gait disturbances, urinary incontinence and mental status, and radiological evaluation with brain CT was performed prior to and after ELD test, as well as three months after shunting. Twenty-two patients were finally shunted and included in this study. In a three-month follow-up, using a previously validated score system, overall improvement after permanent shunting correlated well to improvement after ELD test (Spearman's rho = 0.462, p = 0.03). When considering any degree of improvement as a positive response, ELD test yielded high positive predictive values for all individual parameters (gait disturbances 94%, 95% CI 71%-100%, urinary incontinence 100%, 95% CI 66%-100%, and mental status 100%, 95% CI 66%-100%) but negative predictive values were low (< 50%) except for cognitive impairment (85%, 95% CI 55%-98%). This study suggests that a positive ELD-valve system test should be considered a reliable criterion for preoperative selection of shunt-responsive NPH patients. In case of a negative ELD-valve system test, further investigation of the presumed NPH patients with additional tests should be performed.

Control Techtronics International

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

West, J.

1995-12-31

Polish graded coal can be burned in existing stoker boilers and meet the 1998 Air Quality standard. This is accomplished with the Control Techtronics microprocessor-based combustion controller accurately and repeatedly: (a) matching the combustion air to the coal firing rate, with continuous stack sensor feedback; (b) continuously varying the boiler`s firing rate based on output water temperature or steam pressure; (c) continuously varying the exhaust fan`s speed to maintain minimum negative pressure in the boiler`s combustion chamber; and recirculating a portion of the flue gas, at varying amounts throughout the boiler`s firing rate. Systems for five boilers have been installedmore » and are operating on MPEC`s Balicka plant in Krakow. Control Techtronics International has $10 million of U.S. Export-Import Bank funds available for similar projects throughout Poland.« less

Therapeutic effect of continuous exercise training program on serum creatinine concentration in men with hypertension: a randomized controlled trial.

PubMed

Sikiru, L; Okoye, G C

2014-09-01

Creatinine (Cr) has been implicated as an independent predictor of hypertension and exercise has been reported as adjunct therapy for hypertension. The purpose of the present study was to investigate the effect of continuous training programme on blood pressure and serum creatinine concentration in black African subjects with hypertension. Three hundred and fifty seven male patients with mild to moderate (systolic blood pressure [SBP] between 140-180 & diastolic blood pressure [DBP] between 90-109 mmHg) essential hypertension were age matched and randomly grouped into continuous & control groups. The continuous group involved in an 8 weeks continuous training (60-79% HR reserve) of between 45 minutes to 60 minutes, 3 times per week, while the control group remain sedentary. SBP, DBP, VO2max, serum Cr, body mass index (BMI), waist hip ratio (WHR) and percent (%) body fat. Analysis of covariance (ANCOVA) and Pearson correlation tests were used in data analysis. Findings of the study revealed significant decreased effects of continuous training programme on SBP, DBP, Cr, BMI, WHR, % body fat and significant increase in VO2max at p< 0.05. Serum Cr is significantly and negatively correlated with SBP (-.335), DBP (.194), BMI (.268), WHR (-.258) and % body fat (-.190) at p<0.05. The present study demonstrated a rationale bases for the adjunct therapeutic role of moderate intensity continuous exercise training as a multi-therapy in the down regulation of blood pressure, serum Cr, body size and body fat in hypertension.

Renal effects of continuous negative pressure breathing

NASA Technical Reports Server (NTRS)

Kinney, M. J.

1975-01-01

Continuous negative pressure breathing (CNPB) was utilized to simulate the thoracic vascular distension of zero G in 11 anesthetized rats. The animals underwent renal clearance and micropuncture renal nephron studies before, during, and after CNPB. Four rats were pretreated with a high salt diet and I-M desoxycorticosterone (DOCA) in excess. None of these rats diuresed with CNPB. In contrast, five of the seven remaining rats increased the fraction of the filtered sodium excreted and their urinary flow rate. Potassium excretion increased. End proximal tubular fluid specimen's TF/P inulin ratios were unchanged. Whole kidney and single nephron glomerular filtration rates fell 10%. CNPB, a mechanism for atrial distension, appears to cause in the rat a decrease in distal tubular sodium and water reabsorption. Exogenous mineral-corticoid prevents the diuresis, saluresis, and kaluresis. The adequacy of other nonatrial volume control mechanisms in regulating renal salt and water conservation in opposition to the studied atrial-renal (Henry-Gauer) reflex of thoracic vascular distension is confirmed.

Obstructive sleep apnea syndrome and hypertension: mechanism of the linkage and 24-h blood pressure control.

PubMed

Kario, Kazuomi

2009-07-01

Hypertensive patients with obstructive sleep apnea syndrome (OSAS) constitute a high-risk group for metabolic syndrome. OSAS directly induces negative intrathoracic pressure and decreases pulmonary stretch receptor stimulation, chemoreceptor stimulation, hypoxemia, hypercapnia and microarousal. These changes potentiate various risk factors, including the sympathetic nervous system, renin-angiotensin-aldosterone system and inflammation. Early detection and treatment of OSAS in asymptomatic hypertensive patients is essentially important to prevent hypertensive target organ damage and subsequent cardiovascular events. Continuous positive airway pressure (CPAP) therapy, a first-line treatment in hypertensive patients with moderate to severe OSAS, reduces ambulatory BP level, particularly during the sleep period, and midnight BP surge. However, individual differences in the BP-lowering effect of CPAP have been observed. OSAS hypertensive patients who do not tolerate CPAP remain at a high risk for cardiovascular disease because of negative intrathoracic pressure and need more aggressive antihypertensive treatment to achieve 24-h BP control with nocturnal BP <120/70 mm Hg.

Hemodynamic differences between continual positive and two types of negative pressure ventilation.

PubMed

Lockhat, D; Langleben, D; Zidulka, A

1992-09-01

In seven anesthetized dogs, ventilated with matching lung volumes, tidal volumes, and respiratory rates, we compared the effects on cardiac output (CO), arterial venous oxygen saturation difference (SaO2 - SVO2), and femoral and inferior vena cava pressure (1) intermittent positive pressure ventilation with positive end-expiratory pressure (CPPV); (2) iron-lung ventilation with negative end-expiratory pressure (ILV-NEEP); (3) grid and wrap ventilation with NEEP applied to the thorax and upper abdomen (G&W-NEEP). The values of CO and SaO2 - SVO2 with ILV-NEEP were similar to those with CPPV. However, with G&W-NEEP as compared with ILV-NEEP, mean CO was greater (2.9 versus 2.6 L/min, p = 0.02) and mean (SaO2 - SVO2) was lower (26.6% versus 28.3%, p = NS). Mean PFEM-IVC was higher with G&W-NEEP than with the other types of ventilation. We conclude that (1) ILV-NEEP is hemodynamically equivalent to CPPV and (2) G&W-NEEP has less adverse hemodynamic consequences. has less adverse hemodynamic consequences.

Improvement of wound healing by regulated oxygen-enriched negative pressure-assisted wound therapy in a rabbit model.

PubMed

Li, Y Z; Hu, X D; Lai, X M; Li, Y F; Lei, Y

2018-01-01

Development of drug therapies and other techniques for wound care have resulted in significant improvement of the cure rate and shortening of the healing time for wounds. A modified technique of regulated oxygen-enriched negative pressure-assisted wound therapy (RO-NPT) has been reported. To evaluate the efficacy and impact of RO-NPT on wound recovery and inflammation. Infected wounds were established on 40 adult female white rabbits, which were then randomized to one of four groups: O 2 group, regulated negative pressure-assisted wound therapy (RNPT) group, regulated oxygen-enriched negative pressure-assisted wound therapy (RO-NPT) group and healthy control (HC) group. Each day, the O 2 group was treated with a constant oxygen supply (1 L/min) to the wound, while the RNPT group was treated with continuous regulated negative pressure (70 ± 5 mmHg) and the RNPT + O 2 group was treated with both. The HC group was treated with gauze dressing alone, which was changed every day. Leucocyte count, colony count and wound-healing rate were calculated. Levels of tumour necrosis factor (TNF)-α, interleukin (IL)-1β and IL-8 were evaluated by ELISA. RO-RNPT significantly decreased bacterial count and TNF-α level, and increased the wound-healing rate. IL-1β, IL-8 and leucocyte count had a tendency to increase in the early phase of inflammation and a tendency to decrease in the later phase of inflammation in the RO-RNPT group. RO-NPT therapy assisted wound recovery and inflammation control compared with the RNPT and oxygen-enriched therapies. RO-NPT therapy also increased levels of IL-1β and IL-8 and attenuated expression of TNF-α in the early phase of inflammation. © 2017 British Association of Dermatologists.

Ultrafast cavitation induced by an X-ray laser in water drops

NASA Astrophysics Data System (ADS)

Stan, Claudiu; Willmott, Philip; Stone, Howard; Koglin, Jason; Liang, Mengning; Aquila, Andrew; Robinson, Joseph; Gumerlock, Karl; Blaj, Gabriel; Sierra, Raymond; Boutet, Sebastien; Guillet, Serge; Curtis, Robin; Vetter, Sharon; Loos, Henrik; Turner, James; Decker, Franz-Josef

2016-11-01

Cavitation in pure water is determined by an intrinsic heterogeneous cavitation mechanism, which prevents in general the experimental generation of large tensions (negative pressures) in bulk liquid water. We developed an ultrafast decompression technique, based on the reflection of shock waves generated by an X-ray laser inside liquid drops, to stretch liquids to large negative pressures in a few nanoseconds. Using this method, we observed cavitation in liquid water at pressures below -100 MPa. These large tensions exceed significantly those achieved previously, mainly due to the ultrafast decompression. The decompression induced by shock waves generated by an X-ray laser is rapid enough to continue to stretch the liquid phase after the heterogeneous cavitation occurs in water, despite the rapid growth of cavitation nanobubbles. We developed a nucleation-and-growth hydrodynamic cavitation model that explains our results and estimates the concentration of heterogeneous cavitation nuclei in water.

40 CFR 62.14454 - How must I monitor the required parameters?

Code of Federal Regulations, 2014 CFR

2014-07-01

... installed in each baghouse compartment or cell. (7) For negative pressure or induced air FF, the bag leak...) AIR PROGRAMS (CONTINUED) APPROVAL AND PROMULGATION OF STATE PLANS FOR DESIGNATED FACILITIES AND... use an air pollution control device that includes a FF and are not demonstrating compliance using PM...

40 CFR 62.14454 - How must I monitor the required parameters?

Code of Federal Regulations, 2013 CFR

2013-07-01

... installed in each baghouse compartment or cell. (7) For negative pressure or induced air FF, the bag leak...) AIR PROGRAMS (CONTINUED) APPROVAL AND PROMULGATION OF STATE PLANS FOR DESIGNATED FACILITIES AND... use an air pollution control device that includes a FF and are not demonstrating compliance using PM...

An apparatus for altering the mechanical load of the respiratory system.

PubMed

Younes, M; Bilan, D; Jung, D; Kroker, H

1987-06-01

We describe an apparatus for altering the mechanical load against which the respiratory muscles operate in humans. A closed system incorporates a rolling seal spirometer. The spirometer piston shaft is coupled to a fast-responding linear actuator that develops force in proportion to desired command signals. The command signal may be flow (resistive loading or unloading), volume (elastic loading or unloading), constant voltage (continuous positive or negative pressure), or any external function. Combinations of loads can be applied. Logic circuits permit application of the load at specific times during the respiratory cycle, and the magnitude of the loads is continuously adjustable. Maximum pressure output is +/- 20 cmH2O. The apparatus permits loading or unloading over a range of ventilation extending from resting levels to those observed during high levels of exercise (over 100 l/min). In response to a square-wave input, pressure rises exponentially with a time constant of 20 ms.

Effects of feedstock availability on the negative ion behavior in a C{sub 4}F{sub 8} inductively coupled plasma

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

Zhao, Shu-Xia; Research group PLASMANT, Dept. Chemistry, University of Antwerp, Universiteitsplein 1, B-2610 Antwerp; Gao, Fei

2015-07-21

In this paper, the negative ion behavior in a C{sub 4}F{sub 8} inductively coupled plasma (ICP) is investigated using a hybrid model. The model predicts a non-monotonic variation of the total negative ion density with power at low pressure (10–30 mTorr), and this trend agrees well with experiments that were carried out in many fluorocarbon (fc) ICP sources, like C{sub 2}F{sub 6}, CHF{sub 3}, and C{sub 4}F{sub 8}. This behavior is explained by the availability of feedstock C{sub 4}F{sub 8} gas as a source of the negative ions, as well as by the presence of low energy electrons due tomore » vibrational excitation at low power. The maximum of the negative ion density shifts to low power values upon decreasing pressure, because of the more pronounced depletion of C{sub 4}F{sub 8} molecules, and at high pressure (∼50 mTorr), the anion density continuously increases with power, which is similar to fc CCP sources. Furthermore, the negative ion composition is identified in this paper. Our work demonstrates that for a clear understanding of the negative ion behavior in radio frequency C{sub 4}F{sub 8} plasma sources, one needs to take into account many factors, like the attachment characteristics, the anion composition, the spatial profiles, and the reactor configuration. Finally, a detailed comparison of our simulation results with experiments is conducted.« less

Standardization of Negative Controls in Diagnostic Immunohistochemistry: Recommendations From the International Ad Hoc Expert Panel

PubMed Central

Torlakovic, Emina E.; Francis, Glenn; Garratt, John; Gilks, Blake; Hyjek, Elizabeth; Ibrahim, Merdol; Miller, Rodney; Nielsen, Søren; Petcu, Eugen B.; Swanson, Paul E.; Taylor, Clive R.; Vyberg, Mogens

2014-01-01

Standardization of controls, both positive and negative controls, is needed for diagnostic immunohistochemistry (dIHC). The use of IHC-negative controls, irrespective of type, although well established, is not standardized. As such, the relevance and applicability of negative controls continues to challenge both pathologists and laboratory budgets. Despite the clear theoretical notion that appropriate controls serve to demonstrate the sensitivity and specificity of the dIHC test, it remains unclear which types of positive and negative controls are applicable and/or useful in day-to-day clinical practice. There is a perceived need to provide “best practice recommendations” for the use of negative controls. This perception is driven not only by logistics and cost issues, but also by increased pressure for accurate IHC testing, especially when IHC is performed for predictive markers, the number of which is rising as personalized medicine continues to develop. Herein, an international ad hoc expert panel reviews classification of negative controls relevant to clinical practice, proposes standard terminology for negative controls, considers the total evidence of IHC specificity that is available to pathologists, and develops a set of recommendations for the use of negative controls in dIHC based on “fit-for-use” principles. PMID:24714041

Seasonal emanation of radon at Ghuttu, northwest Himalaya: Differentiation of atmospheric temperature and pressure influences.

PubMed

Kamra, Leena

2015-11-01

Continuous monitoring of radon along with meteorological parameters has been carried out in a seismically active area of Garhwal region, northwest Himalaya, within the frame work of earthquake precursory research. Radon measurements are carried out by using a gamma ray detector installed in the air column at a depth of 10m in a 68m deep borehole. The analysis of long time series for 2006-2012 shows strong seasonal variability masked by diurnal and multi-day variations. Isolation of a seasonal cycle by minimising short-time by 31 day running average shows a strong seasonal variation with unambiguous dependence on atmospheric temperature and pressure. The seasonal characteristics of radon concentrations are positively correlated to atmospheric temperature (R=0.95) and negatively correlated to atmospheric pressure (R=-0.82). The temperature and pressure variation in their annual progressions are negatively correlated. The calculations of partial correlation coefficient permit us to conclude that atmospheric temperature plays a dominant role in controlling the variability of radon in borehole, 71% of the variability in radon arises from the variation in atmospheric temperature and about 6% of the variability is contributed by atmospheric pressure. The influence of pressure variations in an annual cycle appears to be a pseudo-effect, resulting from the negative correlation between temperature and pressure variations. Incorporation of these results explains the varying and even contradictory claims regarding the influence of the pressure variability on radon changes in the published literature. Temperature dependence, facilitated by the temperature gradient in the borehole, controls the transportation of radon from the deep interior to the surface. Copyright © 2015 Elsevier Ltd. All rights reserved.

Can single use negative pressure wound therapy be an alternative method to manage keloid scarring? A preliminary report of a clinical and ultrasound/colour-power-doppler study.

PubMed

Fraccalvieri, Marco; Sarno, Antonino; Gasperini, Stefano; Zingarelli, Enrico; Fava, Raffaella; Salomone, Marco; Bruschi, Stefano

2013-06-01

Keloid scarring represents a pathological healing where primary healing phenomenon is deviated from normal. Pico is a single use negative pressure wound therapy system originally introduced to manage open or just closed wounds. Pico dressing is made of silicone, and distributes an 80 mmHg negative pressure across wound bed. Combination of silicon layer and continuous compression could be a valid method to manage keloid scarring. Since November 2011, three patients were enrolled and evaluated before negative pressure treatment, at end of treatment (1 month) and 2 months later, through Vancouver Scar Scale (VSS), Visual Analog Scale (VAS) and a scoring system for itching. Ultrasound (US) and colour-power-doppler (CPD) examination was performed to evaluate thickness and vascularisation of the scar. One patient was discharged from study after 1 week. In last two patients, VSS, VAS and itching significantly improved after 1 month therapy and the results were stable after 2 months without any therapy. At end of therapy, the 'appearance of palisade vessels' disappeared in both cases at CPD exam; US showed a thickness reduction (average 43·8%). We propose a well-tolerated, non invasive treatment to manage keloid scarring. Prospective studies are necessary to investigate whether these preliminary observations are confirmed. © 2012 The Authors. International Wound Journal © 2012 John Wiley & Sons Ltd and Medicalhelplines.com Inc.

Cryogenic wind tunnels: Problems of continuous operation at low temperatures

NASA Technical Reports Server (NTRS)

Faulmann, D.

1986-01-01

The design of a cryogenic wind tunnel which operates continuously, and is capable of attaining transonic speeds at generating pressures of about 3 bars is described. Its stainless steel construction with inside insulation allows for very rapid temperature variations promoted by rapid changes in the liquid nitrogen flow. A comparative study of temperature measuring probes shows a good reliability of thin sheet thermocouples. To measure fluctuations, only a cold wire makes it possible to record frequencies of about 300 Hz. The use of an integral computer method makes it possible to determine the impact of the wall temperature ratio to the adiabatic wall temperature for the various parameters characterizing the boundary layer. These cases are processed with positive and negative pressure gradients.

40 CFR 60.2165 - What monitoring equipment must I install and what parameters must I monitor?

Code of Federal Regulations, 2013 CFR

2013-07-01

... installed in each baghouse compartment or cell. For negative pressure or induced air fabric filters, the bag... test. (g) For waste-burning kilns not equipped with a wet scrubber, in place of hydrogen chloride..., maintain, and operate a continuous emission monitoring system for monitoring hydrogen chloride emissions...

Therapeutic Strategies for Sleep Apnea in Hypertension and Heart Failure

PubMed Central

Noda, Akiko; Miyata, Seiko; Yasuda, Yoshinari

2013-01-01

Sleep-disordered breathing (SDB) causes hypoxemia, negative intrathoracic pressure, and frequent arousal, contributing to increased cardiovascular disease mortality and morbidity. Obstructive sleep apnea syndrome (OSAS) is linked to hypertension, ischemic heart disease, and cardiac arrhythmias. Successful continuous positive airway pressure (CPAP) treatment has a beneficial effect on hypertension and improves the survival rate of patients with cardiovascular disease. Thus, long-term compliance with CPAP treatment may result in substantial blood pressure reduction in patients with resistant hypertension suffering from OSAS. Central sleep apnea and Cheyne-Stokes respiration occur in 30–50% of patients with heart failure (HF). Intermittent hypoxemia, nocturnal surges in sympathetic activity, and increased left ventricular preload and afterload due to negative intrathoracic pressure all lead to impaired cardiac function and poor life prognosis. SDB-related HF has been considered the potential therapeutic target. CPAP, nocturnal O2 therapy, and adaptive servoventilation minimize the effects of sleep apnea, thereby improving cardiac function, prognosis, and quality of life. Early diagnosis and treatment of SDB will yield better therapeutic outcomes for hypertension and HF. PMID:23509623

Sensitization of Upper Airway Mechanoreceptors as a New Pharmacologic Principle to Treat Obstructive Sleep Apnea: Investigations with AVE0118 in Anesthetized Pigs

PubMed Central

Wirth, Klaus J.; Steinmeyer, Klaus; Ruetten, Hartmut

2013-01-01

Study Objectives: Drug treatment for obstructive sleep apnea (OSA) is desirable because at least 30% of patients do not tolerate continuous positive airway pressure (CPAP) treatment. The negative pressure reflex (NPR) involving superficially located mechanoreceptors in the upper airway (UA) is an important mechanism for UA patency inhibitable by topical UA anesthesia (lidocaine). The NPR may serve as a target for pharmacological intervention for a topical treatment of OSA. The objective was to determine the effect of pharmacological augmentation of the NPR on UA collapsibility. Design: We developed a model of UA collapsibility in which application of negative pressures caused UA collapses in spontaneously breathing α-chloralose-urethane anesthetized pigs as indicated by characteristic tracheal pressure and air flow changes. Setting: N/A. Patients or Participants: N/A. Interventions: N/A. Measurements and Results: The potassium channel blocker AVE0118 administered topically to the UA in doses of 1, 3, and 10 mg per nostril sensitized the NPR, shifting the mechanoreceptor response threshold for the genioglossus muscle to more positive pressures (P < 0.001; n = 6 per group) and dose-dependently inhibited UA collapsibility. Ten mg of AVE0118 prevented UA collapses against negative pressures of -150 mbar (P < 0.01) for > 4 h in all pigs, while in control pigs the UA collapsed at -50 mbar or less negative pressures. The effect of AVE0118 was abolished by UA lidocaine anesthesia. Acute intravenous administration of naloxone or acetazolamide was ineffective; paroxetine and mirtazepine were weakly effective and fluoxetine was moderately effective in line with reported clinical efficacy. Conclusion: Topical administration of AVE0118 to the UA is a promising pharmacologic approach for the treatment of OSA. Citation: Wirth KJ; Steinmeyer K; Ruetten H. Sensitization of upper airway mechanoreceptors as a new pharmacologic principle to treat obstructive sleep apnea: investigations with AVE0118 in anesthetized pigs. SLEEP 2013;36(5):699-708. PMID:23633752

The effect of positive and negative message framing on short term continuous positive airway pressure compliance in patients with obstructive sleep apnea

PubMed Central

Czaban, Marcin; Berry, Marc P.; Nirmalan, Prajeshan; Brown, Richard; Birdseye, Adam; Woroszyl, Asia; Chapman, Julia; Kent, Brian D.; Hart, Nicholas; Rossi, Gian Paolo; Steier, Joerg

2018-01-01

Background Continuous positive airway pressure (CPAP), the best available treatment for obstructive sleep apnea (OSA), requires long-term compliance to be effective. Behavioral interventions may be used to improve adherence to CPAP. We aimed to investigate whether positive or negative message framing impacts on CPAP compliance in patients with OSA, when compared to standard care. Methods Consenting patients with confirmed OSA were randomly allocated to receive along with their CPAP either positively or negatively framed messages (Pos; Neg), or standard care (Con). Standardized motivational messages were read out to patients during an initial teaching session and through weekly telephone calls. Patients’ compliance data were reviewed 2 and 6 weeks following CPAP initiation. Results We randomized 112 patients to groups that were matched for age, BMI, and OSA severity. The positively framed group (Pos) showed greater CPAP usage after 2 weeks (total use 53.7±31.4 hours) as compared to the negatively framed and the control group (35.6±27.4 and 40.8±33.5 hours, P<0.05); however, no differences were seen at 6 weeks. There were more dropouts in the control group than in either framed groups (Pos n=5; Neg n=8; Con n=11; P<0.05). Conclusions Positively framed messages can improve CPAP adherence in patients with OSA in the short-term; however, strategies for implementing its long-term use need to be developed. PMID:29445540

The effect of positive and negative message framing on short term continuous positive airway pressure compliance in patients with obstructive sleep apnea.

PubMed

Pengo, Martino F; Czaban, Marcin; Berry, Marc P; Nirmalan, Prajeshan; Brown, Richard; Birdseye, Adam; Woroszyl, Asia; Chapman, Julia; Kent, Brian D; Hart, Nicholas; Rossi, Gian Paolo; Steier, Joerg

2018-01-01

Continuous positive airway pressure (CPAP), the best available treatment for obstructive sleep apnea (OSA), requires long-term compliance to be effective. Behavioral interventions may be used to improve adherence to CPAP. We aimed to investigate whether positive or negative message framing impacts on CPAP compliance in patients with OSA, when compared to standard care. Consenting patients with confirmed OSA were randomly allocated to receive along with their CPAP either positively or negatively framed messages (Pos; Neg), or standard care (Con). Standardized motivational messages were read out to patients during an initial teaching session and through weekly telephone calls. Patients' compliance data were reviewed 2 and 6 weeks following CPAP initiation. We randomized 112 patients to groups that were matched for age, BMI, and OSA severity. The positively framed group (Pos) showed greater CPAP usage after 2 weeks (total use 53.7±31.4 hours) as compared to the negatively framed and the control group (35.6±27.4 and 40.8±33.5 hours, P<0.05); however, no differences were seen at 6 weeks. There were more dropouts in the control group than in either framed groups (Pos n=5; Neg n=8; Con n=11; P<0.05). Positively framed messages can improve CPAP adherence in patients with OSA in the short-term; however, strategies for implementing its long-term use need to be developed.

Open and closed-circuit endotracheal suctioning in acute lung injury: efficiency and effects on gas exchange.

PubMed

Lasocki, Sigismond; Lu, Qin; Sartorius, Alfonso; Fouillat, Dominique; Remerand, Francis; Rouby, Jean-Jacques

2006-01-01

Closed-circuit endotracheal suctioning (CES) is advocated for preventing hypoxemia caused by the loss of lung volume resulting from open endotracheal suctioning (OES). However, the efficiency of CES and OES on tracheal secretion removal has never been compared in patients with acute lung injury. The authors designed a two-part study aimed at comparing gas exchange and efficiency between OES and CES performed at two levels of negative pressure. Among 18 patients with acute lung injury, 9 underwent CES and OES at 3-h intervals in a random order using a negative pressure of -200 mmHg. Nine other patients underwent CES twice using two levels of negative pressure (-200 and -400 mmHg) applied in a random order. After each CES, a recruitment maneuver was performed using 20 consecutive hyperinflations. Tracheal aspirates were weighed after each suctioning procedure. Arterial blood gases were continuously recorded using an intravascular sensor. Open endotracheal suctioning induced a significant 18% decrease in arterial oxygen tension (Pa(O2)) (range, +13 to -71%) and an 8% increase in arterial carbon dioxide tension (Pa(CO2)) (range, -2 to +16%) that persisted 15 min after the end of the procedure. CES using -200 cm H2O did not change Pa(O2), but tracheal aspirate mass was lower compared with OES (0.6 +/- 1.0 vs. 3.2 +/- 5.1 g; P = 0.03). Increasing negative pressure to -400 cm H2O during CES did not change Pa(O2) but increased the tracheal aspirate mass (1.7 +/- 1.6 vs. 1.0 +/- 1.3 g; P = 0.02). Closed-circuit endotracheal suctioning followed by a recruitment maneuver prevents hypoxemia resulting from OES but decreases secretion removal. Increasing suctioning pressure enhances suctioning efficiency without impairing gas exchange.

High negative pressure subcutaneous suction drain for managing debilitating subcutaneous emphysema secondary to tube thoracostomy for an iatrogenic post computed tomography guided transthoracic needle biopsy pneumothorax: Case report and review of literature.

PubMed

Ahmed, Zeeshan; Patel, Pinakin; Singh, Suresh; Sharma, Raj Govind; Somani, Pankaj; Gouri, Abdul Rauf; Singh, Shiv

2016-01-01

Subcutaneous emphysema is a common complication of tube thoracostomy. Though self-limiting, it should be treated when it causes palpebral closure, dyspnea, dysphagia or undue disfigurement resulting in anxiety and distress to the patient. A 72year old man who was a known case of COPD on bronchodilators developed a large pneumothorax and respiratory distress after a CT guided transthoracic lung biopsy done for a lung opacity (approx. 3×3cm) at the right hilar region on Chest X-ray. Within 24h of an urgent tube thoracostomy, patient developed intractable subcutaneous emphysema with closure of palpebral fissure and dyspnea unresponsive to increasing suction on chest tube. A subcutaneous fenestrated drain was placed mid-way between the nipple and clavicle in the mid-clavicular line bilaterally. Continuous negative suction (-150mmHg) resulted in immediate, sustained relief and complete resolution within 5days. Extensive and debilitating SE (subcutaneous emphysema) has to be treated promptly to relieve patient discomfort, dysphagia or imminent respiratory compromise. A variety of treatment have been tried including infraclavicular blow-hole incisions, subcutaneous drains +/- negative pressure suction, fenestrated angiocatheters, Vacuum assisted dressings and increasing suction on a pre-existing chest tube. We describe a high negative pressure subcutaneous suction drain which provides immediate and sustained relief in debilitating SE. Debilitating subcutaneous emphysema which causes distress, anxiety, palpebral closure, dyspnoea or dysphagia requires intervention. High negative pressure subcutaneous suction drain provides immediate and sustained relief in extensive and debilitating SE. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Reducing WBC background in cancer cell separation products by negative acoustic contrast particle immuno-acoustophoresis.

PubMed

Cushing, Kevin; Undvall, Eva; Ceder, Yvonne; Lilja, Hans; Laurell, Thomas

2018-02-13

Cancer cells display acoustic properties enabling acoustophoretic separation from white blood cells (WBCs) with 2-3 log suppression of the WBC background. However, a subset of WBCs has overlapping acoustic properties with cancer cells, which is why label-free acoustophoretic cancer cell isolation needs additional purification prior to analysis. This paper reports for the first time a proof of concept for continuous flow acoustophoretic negative selection of WBCs from cancer cells using negative acoustic contrast elastomeric particles (EPs) activated with CD45-antibodies that specifically bind to WBCs. The EP/WBC complexes align at the acoustic pressure anti-nodes along the channel walls while unbound cancer cells focus to the pressure node in the channel center, enabling continuous flow based depletion of WBC background in a cancer cell product. The method does not provide a single process solution for the CTC separation challenge, but provides an elegant part to a multi-step process by further reducing the WBC background in cancer cell separation products derived from an initial step of label-free acoustophoresis. We report the recorded performance of the negative selection immuno-acoustophoretic WBC depletion and cancer cell recovery. To eliminate the negative impact of the separation due to the known problems of aggregation of negative acoustic contrast particles along the sidewalls of the acoustophoresis channel and to enable continuous separation of EP/WBC complexes from cancer cells, a new acoustic actuation method has been implemented where the ultrasound frequency is scanned (1.991MHz ± 100 kHz, scan rate 200 kHz ms -1 ). Using this frequency scanning strategy EP/WBC complexes were acoustophoretically separated from mixtures of WBCs spiked with breast and prostate cancer cells (DU145 and MCF-7). An 86-fold (MCF-7) and 52-fold (DU145) reduction of WBCs in the cancer cell fractions were recorded with separation efficiencies of 98.6% (MCF-7) and 99.7% (DU145) and cancer cell recoveries of 89.8% (MCF-7) and 85.0% (DU145). Copyright © 2017 Elsevier B.V. All rights reserved.

Oscillation-Mark Formation and Liquid-Slag Consumption in Continuous Casting Mold

NASA Astrophysics Data System (ADS)

Yang, Jie; Meng, Xiangning; Wang, Ning; Zhu, Miaoyong

2017-04-01

Traditional understanding on the complex multiphysics phenomenon of the meniscus in the oscillating mold for continuously cast steel, including oscillation-mark formation and liquid-slag consumption, has never considered the shape influence of the flux channel between the mold wall and the solidifying shell surface. Based on the reciprocating oscillation of mold, this study was carried out to calculate theoretically the periodic pressure and the liquid-slag layer thickness in the flux channel for the upper and the lower meniscus that possess different shapes in combination with a transient equilibrium profile of the flux channel as well as the sinusoidal and the nonsinusoidal oscillation modes of mold. The effect of flux channel shape on the multiphysics phenomenon in the meniscus was determined by the physical oscillation simulation by using an experimental cold model mold. The results show that the shape difference between the upper and the lower meniscus leads to the opposite direction of pressure in the flux channel. The pressure in the opposite direction plays a respective role in oscillation-mark formation and liquid-slag consumption in an oscillation cycle of mold, and thus, it makes a new mechanism for explaining the multiphysics phenomenon in the meniscus. The oscillation mark is initially formed by the rapid increase of positive channel pressure in the upper meniscus, and most of the liquid slag is infiltrated into the flux channel by the negative channel pressure in the lower meniscus from the end of a positive strip time to the beginning of the next positive strip time, including the negative strip time in between. Furthermore, the physical characteristics of the lubrication behavior in the meniscus are summarized, including liquid-slag infiltration, solidifying shell deformation, and the thickness change of the liquid-slag layer.

Effects of reduced-impact logging and forest physiognomy on bat populations of lowland Amazonian forest.

Treesearch

Steven J. Presley; Michael R. Willig; Wunderle Jr. Joseph M.; Luis Nélio Saldanha

2008-01-01

1.As human population size increases, demand for natural resources will increase. Logging pressure related to increasing demands continues to threaten remote areas of Amazonian forest. A harvest protocol is required to provide renewable timber resources that meet consumer needs while minimizing negative effects on biodiversity and ecosystem services. Reduced-impact...

A Nurse-Initiated Perioperative Pressure Injury Risk Assessment and Prevention Protocol.

PubMed

Meehan, Anita J; Beinlich, Nancy R; Hammonds, Tracy L

2016-12-01

Pressure injuries negatively affect patients physically, emotionally, and economically. Studies report that pressure injuries occur in 69% of inpatients who have undergone a surgical procedure while hospitalized. In 2012, we created a nurse-initiated, perioperative pressure injury risk assessment measure for our midwestern, urban, adult teaching hospital. We retrospectively applied the risk assessment to a random sample of 350 surgical patients which validated the measure. The prospective use of the risk assessment and prevention measures in 350 surgical patients resulted in a 60% reduction in pressure injuries compared with the retrospective group. Our findings support the use of a multipronged approach for the prevention of health care-associated pressure injuries in the surgical population, which includes assessment of risk, implementation of evidence-based prevention interventions for at-risk patients, and continuation of prevention beyond the perioperative setting to the nursing care unit. Copyright © 2016 AORN, Inc. Published by Elsevier Inc. All rights reserved.

[Effects of long time different negative pressures on osteogenic differentiation of rabbit bone mesenchymal stem cells].

PubMed

Zhao, Bowen; Zhang, Hongwei; Xu, Qiang; Ge, Quanhu; Li, Bolong; Peng, Xinyu; Wu, Xiangwei

2017-05-01

To investigate the effects of long time different negative pressures on osteogenic diffe-rentiation of rabbit bone mesenchymal stem cells (BMSCs). The rabbit BMSCs were isolated and cultured by density gradient centrifugation. Flow cytometry was used to analyze expression of surface markers. The third passage cells cultured under condition of osteogenic induction and under different negative pressure of 0 mm Hg (control group), 75 mm Hg (low negative pressure group), and 150 mm Hg (high negative pressure group) (1 mm Hg=0.133 kPa), and the negative pressure time was 30 min/h. Cell growth was observed under phase contrast microscopy, and the growth curve was drawn; alkaline phosphatase (ALP) activity was detected by ELISA after induced for 3, 7, and 14 days. The mRNA and protein expressions of collagen type I (COL-I) and osteocalcin (OC) in BMSCs were analyzed by real-time fluorescence quantitative PCR and Western blot. The cultured cells were identified as BMSCs by flow cytometry. The third passage BMSCs exhibited typical long shuttle and irregular shape. Cell proliferation was inhibited with the increase of negative pressure. After induced for 4 days, the cell number of high negative pressure group was significantly less than that in control group and low negative pressure group ( P <0.05), but there was no significant difference between the low negative pressure group and the control group ( P >0.05); at 5-7 days, the cell number showed significant difference between 3 groups ( P <0.05). The greater the negative pressure was, the greater the inhibition of cell proliferation was. There was no significant difference in ALP activity between groups at 3 days after induction ( P >0.05); the ALP activity showed significant difference ( P <0.05) between the high negative pressure group and the control group at 7 days after induction; and significant difference was found in the ALP activity between 3 groups at 14 days after induction ( P <0.05). The greater the negative pressure was, the higher the ALP activity was. Real-time fluorescence quantitative PCR and Western blot detection showed that the mRNA and protein expressions of COL-I and OC protein were significantly higher in low negative pressure group and high negative pressure group than control group ( P <0.05), and in the high negative pressure group than the low negative pressure group ( P <0.05). With the increase of the negative pressure, the osteogenic differentiation ability of BMSCs increases gradually, but the cell proliferation is inhibited.

The acute effects of lower limb intermittent negative pressure on foot macro- and microcirculation in patients with peripheral arterial disease.

PubMed

Sundby, Øyvind Heiberg; Høiseth, Lars Øivind; Mathiesen, Iacob; Weedon-Fekjær, Harald; Sundhagen, Jon O; Hisdal, Jonny

2017-01-01

Intermittent negative pressure (INP) applied to the lower leg and foot increases foot perfusion in healthy volunteers. The aim of the present study was to describe the effects of INP to the lower leg and foot on foot macro- and microcirculation in patients with lower extremity peripheral arterial disease (PAD). In this experimental study, we analyzed foot circulation during INP in 20 patients [median (range): 75 (63-84yrs)] with PAD. One leg was placed inside an air-tight vacuum chamber connected to an INP-generator. During application of INP (alternating 10s of -40mmHg/7s of atmospheric pressure), we continuously recorded blood flow velocity in a distal foot artery (ultrasound Doppler), skin blood flow on the pulp of the first toes (laser Doppler), heart rate (ECG), and systemic blood pressure (Finometer). After a 5-min baseline sequence (no pressure), a 10-min INP sequence was applied, followed by 5-min post-INP (no pressure). To compare and quantify blood flow fluctuations between sequences, we calculated cumulative up-and-down fluctuations in arterial blood flow velocity per minute. Onset of INP induced an increase in arterial flow velocity and skin blood flow. Peak blood flow velocity was reached 3s after the onset of negative pressure, and increased 46% [(95% CI 36-57), P<0.001] above baseline. Peak skin blood flow was reached 2s after the onset of negative pressure, and increased 89% (95% CI 48-130), P<0.001) above baseline. Cumulative fluctuations per minute were significantly higher during INP-sequences compared to baseline [21 (95% CI 12-30)cm/s/min to 41 (95% CI 32-51)cm/s/min, P<0.001]. Mean INP blood flow velocity increased significantly ~12% above mean baseline blood flow velocity [(6.7 (95% CI 5.2-8.3)cm/s to 7.5 (95% CI 5.9-9.1)cm/s, P = 0.03)]. INP increases foot macro- and microcirculatory flow pulsatility in patients with PAD. Additionally, application of INP resulted in increased mean arterial blood flow velocity.

The acute effects of lower limb intermittent negative pressure on foot macro- and microcirculation in patients with peripheral arterial disease

PubMed Central

Høiseth, Lars Øivind; Mathiesen, Iacob; Weedon-Fekjær, Harald; Sundhagen, Jon O.; Hisdal, Jonny

2017-01-01

Background Intermittent negative pressure (INP) applied to the lower leg and foot increases foot perfusion in healthy volunteers. The aim of the present study was to describe the effects of INP to the lower leg and foot on foot macro- and microcirculation in patients with lower extremity peripheral arterial disease (PAD). Methods In this experimental study, we analyzed foot circulation during INP in 20 patients [median (range): 75 (63-84yrs)] with PAD. One leg was placed inside an air-tight vacuum chamber connected to an INP-generator. During application of INP (alternating 10s of -40mmHg/7s of atmospheric pressure), we continuously recorded blood flow velocity in a distal foot artery (ultrasound Doppler), skin blood flow on the pulp of the first toes (laser Doppler), heart rate (ECG), and systemic blood pressure (Finometer). After a 5-min baseline sequence (no pressure), a 10-min INP sequence was applied, followed by 5-min post-INP (no pressure). To compare and quantify blood flow fluctuations between sequences, we calculated cumulative up-and-down fluctuations in arterial blood flow velocity per minute. Results Onset of INP induced an increase in arterial flow velocity and skin blood flow. Peak blood flow velocity was reached 3s after the onset of negative pressure, and increased 46% [(95% CI 36–57), P<0.001] above baseline. Peak skin blood flow was reached 2s after the onset of negative pressure, and increased 89% (95% CI 48–130), P<0.001) above baseline. Cumulative fluctuations per minute were significantly higher during INP-sequences compared to baseline [21 (95% CI 12–30)cm/s/min to 41 (95% CI 32–51)cm/s/min, P<0.001]. Mean INP blood flow velocity increased significantly ~12% above mean baseline blood flow velocity [(6.7 (95% CI 5.2–8.3)cm/s to 7.5 (95% CI 5.9–9.1)cm/s, P = 0.03)]. Conclusion INP increases foot macro- and microcirculatory flow pulsatility in patients with PAD. Additionally, application of INP resulted in increased mean arterial blood flow velocity. PMID:28591174

The Age-Dependent Relationship between Blood Pressure and Cognitive Impairment: A Cross-Sectional Study in a Rural Area of Xi'an, China.

PubMed

Shang, Suhang; Li, Pei; Deng, Meiying; Jiang, Yu; Chen, Chen; Qu, Qiumin

2016-01-01

Hypertension is a modifiable risk factor for cognitive impairment, although the relationship between hypertension and cognitive impairment is not fully understood. The objective of this study was to investigate the effect of age on the relationship between blood pressure and cognitive impairment. Blood pressure and global cognitive function information was collected from 1799 participants (age 40-85) who lived in a village in the suburbs of Xi'an, China, during in-person interviews. Cognitive impairment was defined as a Mini-Mental State Examination (MMSE) score lower than the cutoff value. The effect of age on the relationship between blood pressure parameters [systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MABP), and high blood pressure (HBP, SBP≥140 mm Hg and/or DBP≥90 mm Hg)] and cognitive impairment was analyzed by logistic regression models using interaction and stratified analysis. Blood pressure and age were regarded as both continuous and categorical data. A total of 231 participants were diagnosed as having cognitive impairment based on our criteria. Interaction analysis for the total population showed that SBP (when regarded as continuous data) was positively correlated with cognitive impairment (OR = 1.130 [95% CI, 1.028-1.242] per 10mmHg, P = 0.011); however, the age by SBP interaction term was negatively correlated with cognitive impairment (OR = 0.989 [95% CI, 0.982-0.997] per 10mmHg×year, P = 0.006), indicating that the relationship between SBP and cognitive impairment was age-dependent (OR = 1.130×0.989(age-55.5) per 10mmHg,40 ≤age≤85). When the blood pressure and age were considered as binary data, the results were similar to those obtained when they were considered as continuous variables. Stratified multivariate analysis revealed that the relationship between SBP (when regarded as continuous data) and cognitive impairment was positive for patients aged 40-49 years (OR = 1.349 [95% CI: 1.039-1.753] per 10mmHg, P = 0.025) and 50-59 years (OR = 1.185 [95% CI: 1.028-1.366] per 10mmHg, P = 0.019), whereas it tended to be negative for patients aged 60-69 years (OR = 0.878 [95% CI: 0.729-1.058] per 10mmHg, P = 0.171) and ≥70 years (OR = 0.927 [95% CI: 0.772-1.113] per 10mmHg, P = 0.416). Results similar to those for SBP were obtained for DBP, MABP and HBP as well. Subsequently, SBP, DBP and MABP were transformed into categorical data (SBP<140mmHg, 140mmHg≤SBP<160mmHg, and SBP≥160mmHg; DBP<90mmHg, 90mmHg≤DBP<100mmHg, and DBP≥100mmHg; MABP<100mmHg, 100mmHg≤MABP<110mmHg, and MABP≥110mmHg), and the stratified multivariate analysis was repeated. This analysis showed that the age-dependent association continued to exist and was especially prominent in the SBP≥160 mmHg, DBP≥90 mmHg and MABP≥110 mmHg groups. Elevated blood pressure is positively correlated with cognitive impairment in the middle-aged, but this positive association declines with increasing age. These results indicated that specific blood pressure management strategies for various age groups may be crucial for maintaining cognitive vitality.

The Age-Dependent Relationship between Blood Pressure and Cognitive Impairment: A Cross-Sectional Study in a Rural Area of Xi'an, China

PubMed Central

Shang, Suhang; Li, Pei; Deng, Meiying; Jiang, Yu; Chen, Chen; Qu, Qiumin

2016-01-01

Background Hypertension is a modifiable risk factor for cognitive impairment, although the relationship between hypertension and cognitive impairment is not fully understood. The objective of this study was to investigate the effect of age on the relationship between blood pressure and cognitive impairment. Methods Blood pressure and global cognitive function information was collected from 1799 participants (age 40–85) who lived in a village in the suburbs of Xi'an, China, during in-person interviews. Cognitive impairment was defined as a Mini-Mental State Examination (MMSE) score lower than the cutoff value. The effect of age on the relationship between blood pressure parameters [systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MABP), and high blood pressure (HBP, SBP≥140 mm Hg and/or DBP≥90 mm Hg)] and cognitive impairment was analyzed by logistic regression models using interaction and stratified analysis. Blood pressure and age were regarded as both continuous and categorical data. Results A total of 231 participants were diagnosed as having cognitive impairment based on our criteria. Interaction analysis for the total population showed that SBP (when regarded as continuous data) was positively correlated with cognitive impairment (OR = 1.130 [95% CI, 1.028–1.242] per 10mmHg, P = 0.011); however, the age by SBP interaction term was negatively correlated with cognitive impairment (OR = 0.989 [95% CI, 0.982–0.997] per 10mmHg×year, P = 0.006), indicating that the relationship between SBP and cognitive impairment was age-dependent (OR = 1.130×0.989(age-55.5) per 10mmHg,40 ≤age≤85). When the blood pressure and age were considered as binary data, the results were similar to those obtained when they were considered as continuous variables. Stratified multivariate analysis revealed that the relationship between SBP (when regarded as continuous data) and cognitive impairment was positive for patients aged 40–49 years (OR = 1.349 [95% CI: 1.039–1.753] per 10mmHg, P = 0.025) and 50–59 years (OR = 1.185 [95% CI: 1.028–1.366] per 10mmHg, P = 0.019), whereas it tended to be negative for patients aged 60–69 years (OR = 0.878 [95% CI: 0.729–1.058] per 10mmHg, P = 0.171) and ≥70 years (OR = 0.927 [95% CI: 0.772–1.113] per 10mmHg, P = 0.416). Results similar to those for SBP were obtained for DBP, MABP and HBP as well. Subsequently, SBP, DBP and MABP were transformed into categorical data (SBP<140mmHg, 140mmHg≤SBP<160mmHg, and SBP≥160mmHg; DBP<90mmHg, 90mmHg≤DBP<100mmHg, and DBP≥100mmHg; MABP<100mmHg, 100mmHg≤MABP<110mmHg, and MABP≥110mmHg), and the stratified multivariate analysis was repeated. This analysis showed that the age-dependent association continued to exist and was especially prominent in the SBP≥160 mmHg, DBP≥90 mmHg and MABP≥110 mmHg groups. Conclusions Elevated blood pressure is positively correlated with cognitive impairment in the middle-aged, but this positive association declines with increasing age. These results indicated that specific blood pressure management strategies for various age groups may be crucial for maintaining cognitive vitality. PMID:27438476

Comparative effect of interval and continuous training programs on serum uric acid in management of hypertension: a randomized controlled trial.

PubMed

Lamina, Sikiru

2011-03-01

The purpose of the study was to investigate the effect of interval and continuous training program on blood pressure and serum uric acid (SUA) levels in subjects with hypertension. Three hundred and fifty-seven male patients with mild to moderate systolic blood pressure (SBP) between 140 and 179 and diastolic blood pressure (DBP) between 90 and 109 mm Hg essential hypertension were age-matched and grouped into interval, continuous, and control groups. The interval (work:rest ratio of 1:1) and continuous groups were involved in an 8-week interval and continuous training program of 45-60 minutes, at intensities of 60-79% of heart rate maximum, whereas the control group remained sedentary during this period. SBP, DBP, maximum oxygen uptake (VO2max) and SUA concentration were assessed. One-way analysis of variance and Scheffe and Pearson correlation tests were used in data analysis. Findings of the study revealed significant effect of exercise training program on VO2max, SBP, DBP, and SUA. However, there was no significant difference between the interval and continuous groups. Changes in VO2max negatively correlated with changes in SUA (r = -0.220) at p < 0.05. It was concluded that both moderate-intensity interval and continuous training programs are effective and neither seems superior to the other in the nonpharmacological management of hypertension and may prevent cardiovascular events through the downregulation of SUA in hypertension. Findings of the study support the recommendations of moderate-intensity interval and continuous training programs as adjuncts for nonpharmacological management of essential hypertension.

Cuff-Free Blood Pressure Estimation Using Pulse Transit Time and Heart Rate.

PubMed

Wang, Ruiping; Jia, Wenyan; Mao, Zhi-Hong; Sclabassi, Robert J; Sun, Mingui

2014-10-01

It has been reported that the pulse transit time (PTT), the interval between the peak of the R-wave in electrocardiogram (ECG) and the fingertip photoplethysmogram (PPG), is related to arterial stiffness, and can be used to estimate the systolic blood pressure (SBP) and diastolic blood pressure (DBP). This phenomenon has been used as the basis to design portable systems for continuously cuff-less blood pressure measurement, benefiting numerous people with heart conditions. However, the PTT-based blood pressure estimation may not be sufficiently accurate because the regulation of blood pressure within the human body is a complex, multivariate physiological process. Considering the negative feedback mechanism in the blood pressure control, we introduce the heart rate (HR) and the blood pressure estimate in the previous step to obtain the current estimate. We validate this method using a clinical database. Our results show that the PTT, HR and previous estimate reduce the estimated error significantly when compared to the conventional PTT estimation approach (p<0.05).

The therapeutic effect of negative pressure in treating femoral head necrosis in rabbits.

PubMed

Zhang, Yin-gang; Wang, Xuezhi; Yang, Zhi; Zhang, Hong; Liu, Miao; Qiu, Yushen; Guo, Xiong

2013-01-01

Because negative pressure can stimulate vascular proliferation, improve blood circulation and promote osteogenic differentiation of bone marrow stromal cells, we investigated the therapeutic effect of negative pressure on femoral head necrosis (FHN) in a rabbit model. Animals were divided into four groups (n = 60/group): [1] model control, [2] core decompression, [3] negative pressure and [4] normal control groups. Histological investigation revealed that at 4 and 8 weeks postoperatively, improvements were observed in trabecular bone shape, empty lacunae and numbers of bone marrow hematopoietic cells and fat cells in the negative pressure group compared to the core decompression group. At week 8, there were no significant differences between the negative pressure and normal control groups. Immunohistochemistry staining revealed higher expression of vascular endothelial growth factor (VEGF) and bone morphogenetic protein-2 (BMP-2) in the femoral heads in the negative pressure group compared with the core decompression group. Transmission electron microscopy revealed that cell organelles were further developed in the negative pressure group compared with the core decompression group. Microvascular ink staining revealed an increased number of bone marrow ink-stained blood vessels, a thicker vascular lumen and increased microvascular density in the negative pressure group relative to the core decompression group. Real-time polymerase chain reaction revealed that expression levels of both VEGF and BMP-2 were higher in the negative pressure group compared with the core decompression group. In summary, negative pressure has a therapeutic effect on FHN. This effect is superior to core decompression, indicating that negative pressure is a potentially valuable method for treating early FHN.

The Therapeutic Effect of Negative Pressure in Treating Femoral Head Necrosis in Rabbits

PubMed Central

Zhang, Yin-gang; Wang, Xuezhi; Yang, Zhi; Zhang, Hong; Liu, Miao; Qiu, Yushen; Guo, Xiong

2013-01-01

Because negative pressure can stimulate vascular proliferation, improve blood circulation and promote osteogenic differentiation of bone marrow stromal cells, we investigated the therapeutic effect of negative pressure on femoral head necrosis (FHN) in a rabbit model. Animals were divided into four groups (n = 60/group): [1] model control, [2] core decompression, [3] negative pressure and [4] normal control groups. Histological investigation revealed that at 4 and 8 weeks postoperatively, improvements were observed in trabecular bone shape, empty lacunae and numbers of bone marrow hematopoietic cells and fat cells in the negative pressure group compared to the core decompression group. At week 8, there were no significant differences between the negative pressure and normal control groups. Immunohistochemistry staining revealed higher expression of vascular endothelial growth factor (VEGF) and bone morphogenetic protein-2 (BMP-2) in the femoral heads in the negative pressure group compared with the core decompression group. Transmission electron microscopy revealed that cell organelles were further developed in the negative pressure group compared with the core decompression group. Microvascular ink staining revealed an increased number of bone marrow ink-stained blood vessels, a thicker vascular lumen and increased microvascular density in the negative pressure group relative to the core decompression group. Real-time polymerase chain reaction revealed that expression levels of both VEGF and BMP-2 were higher in the negative pressure group compared with the core decompression group. In summary, negative pressure has a therapeutic effect on FHN. This effect is superior to core decompression, indicating that negative pressure is a potentially valuable method for treating early FHN. PMID:23383276

Design and evaluation of a novel subatmospheric pressure bioreactor for the preconditioning of tissue-engineered vascular constructs.

PubMed

Coakley, Daniel N; Shaikh, Faisal M; O'Sullivan, Kathleen; Kavanagh, Eamon G; Grace, Pierce A; McGloughlin, Tim M

2016-02-01

The pre-conditioning of tissue-engineered vascular scaffolds with mechanical stimuli is being recognised as an essential step in producing a functional vascular construct. In this study we design and evaluate a novel bioreactor, which exerts a mechanical strain on developing vascular scaffolds via subatmospheric pressure. We design and construct a bioreactor, which exerts subatmospheric pressure via a vacuum assisted closure unit. Vascular scaffolds seeded with human umbilical endothelial cells were evaluated for structural integrity, microbial contamination, cellular viability, von Willebrand factor (VWF) production, cell proliferation and morphology under a range of subatmospheric pressures (75-200mmHg). The bioreactor produced sustained subatmospheric pressures, which exerted a mechanical strain on the vascular scaffold. No microbial contamination was found during the study. The structural integrity of the vascular construct was maintained. There was no difference in cellular viability between control or subatmospheric pressure groups (p = 0.817). Cells continued to produce VWF under a range of subatmospheric pressures. Cells subjected to subatmospheric pressures of 125mmHg and 200mmHg exhibited higher levels of growth than cells in atmospheric pressure at 24 (p≤0.016) and 48 hour (p≤0.001). Negative pressure affected cellular morphology, which were more organised, elongated and expanded when exposed to subatmospheric pressure. We have constructed and validated a novel subatmospheric bioreactor. The bioreactor maintained a continuous subatmospheric pressure to the vascular scaffolds in a stable, sterile and constant environment. The bioreactor exerted a strain on the vascular sheets, which was shown to alter cellular morphology and enhance cellular proliferation.

Utilizing the VeraFlo™ Instillation Negative Pressure Wound Therapy System with Advanced Care for a Case Study

PubMed Central

2016-01-01

Background: Mankind has always suffered wounds throughout time due to trauma, disease, and lifestyles. Many wounds are non-healing and have continued to be challenging. However, utilizing advanced wound care treatments, such as negative pressure wound treatment with instillation and dwell time (NPWTi-d), has proven beneficial. NPWTi-d is indicated in a variety of wounds, such as trauma, surgical, acute, pressure injuries, diabetic foot ulcers, and venous leg ulcers. Bacteria and bioburden interrupts wound healing by increasing the metabolic needs, ingesting, and robbing the necessary nutrients and oxygen. Instillation therapy is the technique of intermittently washing out a wound with a liquid solution. The mechanism of action is instilling fluid into the wound bed, soaking for a determined time, loosening and cleaning of exudate, contaminants, and/or infection, removing fluid via negative pressure, thus promoting tissue growth. Case study: The patient was diagnosed with a large lymphedema mass on the right upper thigh. Surgical removal of the lymphedema mass was indicated due to interference with quality of life. After a failed flap and surgical debridement, NPWTi-d with normal saline was implemented. Results: The patient had excellent results, with obvious forming of red, beefy granulation, epithelization tissue development, and a cleaner, healthier wound bed. Settings for the NPWTi-d was 18 minutes dwell time, every 2.5 hours with a constant pressure of 125 mm/hg pressure. Conclusion: The NPWTi-d demonstrated to be an instrumental treatment in supporting and stimulating healing. Early application of the treatment with normal saline as the instillation fluid prepared the previously failed wound for quicker healing. PMID:28070472

The influence of low and high pressure levels during negative-pressure wound therapy on wound contraction and fluid evacuation.

PubMed

Borgquist, Ola; Ingemansson, Richard; Malmsjö, Malin

2011-02-01

Negative-pressure wound therapy promotes healing by drainage of excessive fluid and debris and by mechanical deformation of the wound. The most commonly used negative pressure, -125 mmHg, may cause pain and ischemia, and the pressure often needs to be reduced. The aim of the present study was to examine wound contraction and fluid removal at different levels of negative pressure. Peripheral wounds were created in 70-kg pigs. The immediate effects of negative-pressure wound therapy (-10 to -175 mmHg) on wound contraction and fluid removal were studied in eight pigs. The long-term effects on wound contraction were studied in eight additional pigs during 72 hours of negative-pressure wound therapy at -75 mmHg. Wound contraction and fluid removal increased gradually with increasing levels of negative pressure until reaching a steady state. Maximum wound contraction was observed at -75 mmHg. When negative-pressure wound therapy was discontinued, after 72 hours of therapy, the wound surface area was smaller than before therapy. Maximum wound fluid removal was observed at -125 mmHg. Negative-pressure wound therapy facilitates drainage of wound fluid and exudates and results in mechanical deformation of the wound edge tissue, which is known to stimulate granulation tissue formation. Maximum wound contraction is achieved already at -75 mmHg, and this may be a suitable pressure for most wounds. In wounds with large volumes of exudate, higher pressure levels may be needed for the initial treatment period.

Ice nucleation triggered by negative pressure.

PubMed

Marcolli, Claudia

2017-11-30

Homogeneous ice nucleation needs supercooling of more than 35 K to become effective. When pressure is applied to water, the melting and the freezing points both decrease. Conversely, melting and freezing temperatures increase under negative pressure, i.e. when water is stretched. This study presents an extrapolation of homogeneous ice nucleation temperatures from positive to negative pressures as a basis for further exploration of ice nucleation under negative pressure. It predicts that increasing negative pressure at temperatures below about 262 K eventually results in homogeneous ice nucleation while at warmer temperature homogeneous cavitation, i. e. bubble nucleation, dominates. Negative pressure occurs locally and briefly when water is stretched due to mechanical shock, sonic waves, or fragmentation. The occurrence of such transient negative pressure should suffice to trigger homogeneous ice nucleation at large supercooling in the absence of ice-nucleating surfaces. In addition, negative pressure can act together with ice-inducing surfaces to enhance their intrinsic ice nucleation efficiency. Dynamic ice nucleation can be used to improve properties and uniformity of frozen products by applying ultrasonic fields and might also be relevant for the freezing of large drops in rainclouds.

Study on hydraulic characteristics of mine dust-proof water supply network

NASA Astrophysics Data System (ADS)

Deng, Quanlong; Jiang, Zhongan; Han, Shuo; Fu, Enqi

2018-01-01

In order to study the hydraulic characteristics of mine dust-proof water supply network and obtain the change rule of water consumption and water pressure, according to the similarity principle and the fluid continuity equation and energy equation, the similarity criterion of mine dust-proof water supply network is deduced, and a similar model of dust-proof water supply network is established based on the prototype of Kailuan Group, the characteristics of hydraulic parameters in water supply network are studied experimentally. The results show that water pressure at each point is a dynamic process, and there is a negative correlation between water pressure and water consumption. With the increase of water consumption, the pressure of water points show a decreasing trend. According to the structure of the pipe network and the location of the water point, the influence degree on the pressure of each point is different.

Apparatus and process to eliminate diffusional limitations in a membrane biological reactor by pressure cycling

DOEpatents

Efthymiou, George S.; Shuler, Michael L.

1989-08-29

An improved multilayer continuous biological membrane reactor and a process to eliminate diffusional limitations in membrane reactors in achieved by causing a convective flux of nutrient to move into and out of an immobilized biocatalyst cell layer. In a pressure cycled mode, by increasing and decreasing the pressure in the respective layers, the differential pressure between the gaseous layer and the nutrient layer is alternately changed from positive to negative. The intermittent change in pressure differential accelerates the transfer of nutrient from the nutrient layers to the biocatalyst cell layer, the transfer of product from the cell layer to the nutrient layer and the transfer of byproduct gas from the cell layer to the gaseous layer. Such intermittent cycling substantially eliminates mass transfer gradients in diffusion inhibited systems and greatly increases product yield and throughput in both inhibited and noninhibited systems.

Elements of an improved model of debris‐flow motion

USGS Publications Warehouse

Iverson, Richard M.

2009-01-01

A new depth‐averaged model of debris‐flow motion describes simultaneous evolution of flow velocity and depth, solid and fluid volume fractions, and pore‐fluid pressure. Non‐hydrostatic pore‐fluid pressure is produced by dilatancy, a state‐dependent property that links the depth‐averaged shear rate and volumetric strain rate of the granular phase. Pore‐pressure changes caused by shearing allow the model to exhibit rate‐dependent flow resistance, despite the fact that the basal shear traction involves only rate‐independent Coulomb friction. An analytical solution of simplified model equations shows that the onset of downslope motion can be accelerated or retarded by pore‐pressure change, contingent on whether dilatancy is positive or negative. A different analytical solution shows that such effects will likely be muted if downslope motion continues long enough, because dilatancy then evolves toward zero, and volume fractions and pore pressure concurrently evolve toward steady states.

Elements of an improved model of debris-flow motion

USGS Publications Warehouse

Iverson, R.M.

2009-01-01

A new depth-averaged model of debris-flow motion describes simultaneous evolution of flow velocity and depth, solid and fluid volume fractions, and pore-fluid pressure. Non-hydrostatic pore-fluid pressure is produced by dilatancy, a state-dependent property that links the depth-averaged shear rate and volumetric strain rate of the granular phase. Pore-pressure changes caused by shearing allow the model to exhibit rate-dependent flow resistance, despite the fact that the basal shear traction involves only rate-independent Coulomb friction. An analytical solution of simplified model equations shows that the onset of downslope motion can be accelerated or retarded by pore-pressure change, contingent on whether dilatancy is positive or negative. A different analytical solution shows that such effects will likely be muted if downslope motion continues long enough, because dilatancy then evolves toward zero, and volume fractions and pore pressure concurrently evolve toward steady states. ?? 2009 American Institute of Physics.

Instantaneous stroke volume in man during lower body negative pressure /LBNP/

NASA Technical Reports Server (NTRS)

Loeppky, J. A.; Richards, K. L.; Greene, E. R.; Eldridge, M. W.; Hoekenga, D. E.; Venters, M. D.; Luft, U. C.

1982-01-01

Results of an examination of the instantaneous time course of the stroke volume (SV) and cardiac output (Q) in response to the onset and release of -50 torr lower body negative pressure (LBNP) are reported. Six male subjects were sealed into a LBNP box up to the iliac crest while being monitored by echocardiograph for centerlamina blood velocity, fluid displacement, stroke volume, heart rate, and leg volume. Particular use was made of pulsed ultrasonic Doppler velocity meters for measuring the blood velocities and flow dynamics. Measurements were made of the subjects continuously beginning from 20 sec prior to and one min after LBNP onset and release. A linear fall in the SV was observed with LBNP at 49% of the baseline value after 33 sec. A 62% drop, the lowest, was detected after 8 min of LBNP. The leg volume was inversely related to Q for the duration of the experiment.

Formation of collapsed tetragonal phase in EuCo₂As₂ under high pressure.

PubMed

Bishop, Matthew; Uhoya, Walter; Tsoi, Georgiy; Vohra, Yogesh K; Sefat, Athena S; Sales, Brian C

2010-10-27

The structural properties of EuCo₂As₂ have been studied up to 35 GPa, through the use of x-ray diffraction in a diamond anvil cell at a synchrotron source. At ambient conditions, EuCo₂As₂ ) (I4/mmm) has a tetragonal lattice structure with a bulk modulus of 48 ± 4 GPa. With the application of pressure, the a axis exhibits negative compressibility with a concurrent sharp decrease in c-axis length. The anomalous compressibility of the a axis continues until 4.7 GPa, at which point the structure undergoes a second-order phase transition to a collapsed tetragonal (CT) state with a bulk modulus of 111 ± 2 GPa. We found a strong correlation between the ambient pressure volume of 122 parents of superconductors and the corresponding tetragonal to collapsed tetragonal phase transition pressures.

Impact of continuous positive airway pressure (CPAP) on the respiratory capacity of chronic kidney disease patients under hemodialysis treatment.

PubMed

Xavier, Vivian Bertoni; Roxo, Renata Spósito; Miorin, Luiz Antônio; Dos Santos Alves, Vera Lúcia; Dos Santos Sens, Yvoty Alves

2015-06-01

Chronic kidney disease (CKD) patients on long-term dialysis present changes in pulmonary function and respiratory muscle strength, negatively influencing physical capacity. To analyze the impact of a continuous positive airway pressure (CPAP) protocol on the respiratory capacity of CKD patients under hemodialysis. A randomized clinical trial was conducted involving 40 CKD patients 19-83 years old divided into two groups: control (n = 20) and CPAP (n = 20). Subjects were assessed on the respiratory muscle function test, maximal respiratory pressures, peak flow and 6-min walk test, at baseline and again at the 2-month follow-up. CPAP group patients were submitted to CPAP protocol (PEEP: 5 cm H2O, flow: 15 L/min, FiO2: 33 %) three times per week during hemodialysis sessions. The CPAP group showed higher forced vital capacity, forced expiratory volume in one second, peak expiratory flow, maximal inspiratory pressure, peak flow, as well as lower systolic blood pressure, heart rate, respiratory rate and Borg scale, in addition to a longer distance travelled on the 6-min walk test, compared with the control group. The introduction of a CPAP protocol during hemodialysis sessions had a positive impact on pulmonary function and physical capacity in CKD patients.

Cannabis use in people with severe mental illness: The association with physical and mental health--a cohort study. A Pharmacotherapy Monitoring and Outcome Survey study.

PubMed

Bruins, Jojanneke; Pijnenborg, Marieke G H M; Bartels-Velthuis, Agna A; Visser, Ellen; van den Heuvel, Edwin R; Bruggeman, Richard; Jörg, Frederike

2016-04-01

In the general population cannabis use is associated with better cardiometabolic outcomes. Patients with severe mental illness frequently use cannabis, but also present increased cardiometabolic risk factors. We explore the association between cannabis use and cardiometabolic risk factors in patients with severe mental illness. A total of 3169 patients with severe mental illness from a Dutch cohort were included in the study. The association of cannabis use with body mass index, waist circumference, blood pressure, cholesterol, triglycerides, glucose, glycated hemoglobin and Positive and Negative Syndrome Scale was examined with separate univariate AN(C)OVA. Changes in metabolic risk factors and Positive and Negative Syndrome Scale were examined after a follow-up interval of 9-24 months, for patients who continued, discontinued, started or were never using cannabis between the two assessments. Cannabis users at baseline had lower body mass index, smaller waist circumference, lower diastolic blood pressure, and more severe psychotic symptoms than non-users. Patients who discontinued their cannabis use after the first assessment had a greater increase in body mass index, waist circumference, diastolic blood pressure and triglyceride concentrations than other patients, and the severity of their psychotic symptoms had decreased more compared to continued users and non-users. Extra attention should be paid to the monitoring and treatment of metabolic parameters in patients who discontinue their cannabis use. © The Author(s) 2016.

The Economic Impact of Closed-Incision Negative-Pressure Therapy in High-Risk Abdominal Incisions: A Cost-Utility Analysis.

PubMed

Chopra, Karan; Gowda, Arvind U; Morrow, Chris; Holton, Luther; Singh, Devinder P

2016-04-01

Complex abdominal wall reconstruction is beset by postoperative complications. A recent meta-analysis comparing the use of closed-incision negative-pressure therapy to standard dressings found a statistically significant reduction in surgical-site infection. The use of closed-incision negative-pressure therapy is gaining acceptance in this population; however, the economic impact of this innovative dressing remains unknown. In this study, a cost-utility analysis was performed assessing closed-incision negative-pressure therapy and standard dressings following closure of abdominal incisions in high-risk patients. Cost-utility methodology involved reviewing literature related to closed-incision negative-pressure therapy in abdominal wall surgery, obtaining utility estimates to calculate quality-adjusted life-year scores for successful surgery and surgery complicated by surgical-site infection, summing costs using Medicare Current Procedural Terminology codes, and creating a decision tree illuminating the most cost-effective dressing strategy. One-way sensitivity analysis was performed to assess the robustness of the results. The aforementioned meta-analysis comparing closed-incision negative-pressure therapy to standard dressings included a subset of five studies assessing abdominal wall surgery in 829 patients (260 closed-incision negative-pressure therapy and 569 standard dressings). Decision tree analysis revealed an estimated savings of $1546.52 and a gain of 0.0024 quality-adjusted life-year with closed-incision negative-pressure therapy compared with standard dressings; therefore, closed-incision negative-pressure therapy is a dominant treatment strategy. One-way sensitivity analysis revealed that closed-incision negative-pressure therapy is a cost-effective option when the surgical-site infection rate is greater than 16.39 percent. The use of closed-incision negative-pressure therapy is cost-saving following closure of abdominal incisions in high-risk patients.

Association of Severe Traumatic Brain Injury Patient Outcomes With Duration of Cerebrovascular Autoregulation Impairment Events.

PubMed

Preiksaitis, Aidanas; Krakauskaite, Solventa; Petkus, Vytautas; Rocka, Saulius; Chomskis, Romanas; Dagi, Teodoro Forcht; Ragauskas, Arminas

2016-07-01

Cerebrovascular autoregulation (CA) is an important hemodynamic mechanism that protects the brain against inappropriate fluctuations in cerebral blood flow in the face of changing cerebral perfusion pressure. Temporal CA failure is associated with worse outcomes in various acute neurological diseases. An integrative approach is presently used according to the existing paradigm for the association of series of temporal CA impairments with the outcomes of patients with traumatic brain injury (TBI). To explore the influence of the duration of CA impairment events on severe TBI patient outcomes. Patient age was also included in the analysis of the prospectively collected clinical data. CA monitoring included 33 prospective severe TBI patients. The pressure reactivity index [PRx(t)] was continuously monitored to collect information on the dynamics of CA status and to analyze associations between the duration of the longest CA impairment event and patient outcomes. The Glasgow outcome scale and the duration of the longest CA impairment were negatively correlated. The duration of autoregulation impairment significantly correlated with worse outcomes. Multidimensional representation of Glasgow outcome scale plots showed that better outcomes were obtained for younger patients (age < 47 years) and those whose longest CA impairment event was shorter than 40 minutes if PRx(t) was above 0.7 in the CA impairment event. Unfavorable outcomes for TBI patients are more significantly associated with the duration of the single longest CA impairment episode at a high PRx(t) value, rather than with averaged PRx(t) values or the average time of all CA impairment episodes. ABP, arterial blood pressureABP(t), continuous reference arterial blood pressureCA, cerebrovascular autoregulationCBF, cerebral blood flowCPP, cerebral perfusion pressureGOS, Glasgow outcome scaleGOSHD, Glasgow outcome scale after hospital dischargeGOS6M, Glasgow outcome scale at 6 months after dischargeICP, intracranial pressureICP(t), continuously monitored intracranial pressureLCAI, longest CA impairmentoptCPP, optimal cerebral perfusion pressurePRx(t), pressure reactivity indexTBI, traumatic brain injury.

Brain tissue partial pressure of oxygen predicts the outcome of severe traumatic brain injury under mild hypothermia treatment.

PubMed

Sun, Hongtao; Zheng, Maohua; Wang, Yanmin; Diao, Yunfeng; Zhao, Wanyong; Wei, Zhengjun

2016-01-01

The aim of this study was to investigate the clinical significance and changes of brain tissue partial pressure of oxygen (PbtO2) in the course of mild hypothermia treatment (MHT) for treating severe traumatic brain injury (sTBI). There were 68 cases with sTBI undergoing MHT. PbtO2, intracranial pressure (ICP), jugular venous oxygen saturation (SjvO2), and cerebral perfusion pressure (CPP) were continuously monitored, and clinical outcomes were evaluated using the Glasgow Outcome Scale score. Of 68 patients with sTBI, PbtO2, SjvO2, and CPP were obviously increased, but decreased ICP level was observed throughout the MHT. PbtO2 and ICP were negatively linearly correlated, while there was a positive linear correlation between PbtO2 and SjvO2. Monitoring CPP and SjvO2 was performed under normal circumstances, and a large proportion of patients were detected with low PbtO2. Decreased PbtO2 was also found after MHT. Continuous PbtO2 monitoring could be introduced to evaluate the condition of regional cerebral oxygen metabolism, thereby guiding the clinical treatment and predicting the outcome.

Dissociative Identity Disorder CPAP Adherence: An Uncommon Factor in Obstructive Sleep Apnea.

PubMed

Gandotra, Kamal; Golish, Joseph; Rosenberg, Carl; Strohl, Kingman

2018-04-15

We present a case of a patient with dissociative identity disorder and symptomatic sleep apnea who was treated with continuous positive airway pressure (CPAP). CPAP use depended upon which personality the patient exhibited but apnea reduction did not. This case illustrates in one individual how personality can positively or negatively affect CPAP adherence. © 2018 American Academy of Sleep Medicine.

Bulk Viscosity of Bubbly Magmas and the Amplification of Pressure Waves

NASA Astrophysics Data System (ADS)

Navon, O.; Lensky, N. G.; Neuberg, J. W.; Lyakhovsky, V.

2001-12-01

The bulk viscosity of magma is needed in order to describe the dynamics of a compressible bubbly magma flowing in conduits and to follow the attenuation of pressure waves travelling through a compressible magma. We developed a model for the bulk viscosity of a suspension of gas bubbles in an incompressible Newtonian liquid that exsolves volatiles (e.g. magma). The suspension is modeled as a close pack of spherical cells, consisting of gas bubbles centered in spherical shells of a volatile-bearing liquid. Following a drop in the ambient pressure the resulting dilatational motion and driving pressure are obtained in terms of the two-phase cell parameters, i.e. bubble radius and gas pressure. By definition, the bulk viscosity of a fluid is the relation between changes of the driving pressure with respect to changes in the resulted expansion strain-rate. Thus, we can use the two-phase solution to define the bulk viscosity of a hypothetical cell, composed of a homogeneously compressible, one-phase, continuous fluid. The resulted bulk viscosity is highly non-linear. At the beginning of the expansion process, when gas exsolution is efficient, the expansion rate grows exponentially while the driving pressure decreases slightly. That means that bulk viscosity is formally negative. The negative value reflects the release of the energy stored in the supersaturated liquid (melt) and its conversion to mechanical work during exsolution. Later, when bubbles are large enough and the gas influx decreases significantly, the strain rate decelerates and the bulk viscosity becomes positive as expected in a dissipative system. We demonstrate that amplification of seismic wave travelling through a volcanic conduit filled with a volatile saturated magma may be attributed to the negative bulk viscosity of the compressible magma. Amplification of an expansion wave may, at some level in the conduit, damage the conduit walls and initiate opening of new pathways for magma to erupt.

Recording blood pressure and eGFR in primary care after the Belgrade screening study.

PubMed

Lezaic, Visnja; Marinkovic, Jelena; Milutinovic, Zoran; Jovanovic-Vasiljevic, Nada; Vujicic, Vesna; Pejovic, Branka; Kalabic, Snezana; Djukanovic, Ljubica

2018-11-01

In 2009, Belgrade nephrologists and general practitioners from thirteen health centers carried out screening for chronic kidney disease (CKD). Three years later, medical records of patients from four health centers participating in the screening study were retrospectively analyzed in order to check whether general practitioners had continued to control patients at risk for CKD in accordance with the recommendations provided. The study included 460 patients who visited their doctor at least once in the three-year period. Data on blood pressure, ACEI use, estimated glomerular filtration rate (eGFR) and comorbidities were taken from patients' medical records. Blood pressure was not recorded in any of the three years in 42.8% and eGFR in 36.7% of the patients, but blood pressure was registered every year in 7.8% and eGFR in 4.3% of them. Over the three years, the relative number of patients with recorded blood pressure decreased from 41.7% to 17.8%, and with recorded eGFR from 41.7% to 21.5%. Multivariate linear regression found that Health Center, systolic and diastolic blood pressure and presence of hypertension were negatively associated with number of years with recorded blood pressure. Health Center, systolic blood pressure and sum of years with recorded eGFR below 60 ml/min/1.73m 2 were associated with number of years with recorded eGFR. Under-recording of blood pressure and eGFR in primary care health centers suggests lack of adherence to current guidelines and insufficient care of CKD patients. This implies the necessity for continuous education of physicians.

Electron-less negative ion extraction from ion-ion plasmas

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

Rafalskyi, Dmytro; Aanesland, Ane

2015-03-09

This paper presents experimental results showing that continuous negative ion extraction, without co-extracted electrons, is possible from highly electronegative SF{sub 6} ion-ion plasma at low gas pressure (1 mTorr). The ratio between the negative ion and electron densities is more than 3000 in the vicinity of the two-grid extraction and acceleration system. The measurements are conducted by both magnetized and non-magnetized energy analyzers attached to the external grid. With these two analyzers, we show that the extracted negative ion flux is almost electron-free and has the same magnitude as the positive ion flux extracted and accelerated when the grids aremore » biased oppositely. The results presented here can be used for validation of numerical and analytical models of ion extraction from ion-ion plasma.« less

Involvement of nitric oxide in the wound bed microcirculatory change during negative pressure wound therapy.

PubMed

Sano, Hitomi; Ichioka, Shigeru

2015-08-01

This study investigated the role of nitric oxide (NO) in the mechanism of blood flow increase in the wound bed during negative pressure wound therapy (NPWT). We developed an improved experimental model that allowed visualisation of the wound bed microcirculation under NPWT. Wounds were created on the mouse ear, taking care to preserve the subdermal vascular plexus, because the wound bed microcirculation was visualised using an intravital microscope system. We investigated whether application of a NO synthase inhibitor (N(G) -nitro-l-arginine methyl ester: L-NAME) might diminish the effect of the NPWT in increasing the wound blood flow. The experimental animals were divided into a negative pressure group (negative pressure of -125 mmHg applied to the wound for 5 minutes; n = 8), and a negative pressure plus L-NAME group (administration of L-NAME prior to application of the negative pressure; n = 8). In the negative pressure group, significant increase of blood flow was observed at 1 minute after the negative pressure application, which was sustained until 5 minutes. On the contrary, in the negative pressure plus L-NAME group, no significant changes were observed throughout the period of observation. These findings suggest that NO synthesis is involved in the wound bed microcirculatory change induced by NPWT. © 2013 The Authors. International Wound Journal © 2013 Medicalhelplines.com Inc and John Wiley & Sons Ltd.

[Progress of researches on the mechanism of cupping therapy].

PubMed

Cui, Shuai; Cui, Jin

2012-12-01

Cupping therapy of Chinese medicine is able to relieve a variety of diseases or clinical conditions, which results from the comprehensive effects of multiple types of stimulation exerted onto the regional acupoint areas. Among the stimuli, the negative pressure from cupping is one of the main factors inducing therapeutic effects. In the present paper, the authors review development of researches on the underlying mechanism of therapeutic effects of cupping-negative pressure from 1) the factor of intra-cup negative pressure; 2) influence of intra-cup negative pressure on cup-blackspot formation; 3) influence of cupping on regional blood vessels and blood flow; 4) effect of cupping on regional ultrastructure of the capillary in the raw-surface tissue; 5) effect of cupping-negative pressure on regional endothelial cells; and 6) biological effects of negative pressure drainage. Generally, cupping induced negative pressure can dilate local blood vessels to improve microcirculation, promote capillary endothelial cells repair, accelerate granulation and angiogenesis, etc., in the regional tissues, normalizing the patients' functional state at last.

The relationships between air exposure, negative pressure, and hemolysis.

PubMed

Pohlmann, Joshua R; Toomasian, John M; Hampton, Claire E; Cook, Keith E; Annich, Gail M; Bartlett, Robert H

2009-01-01

The purpose of this study was to describe the hemolytic effects of both negative pressure and an air-blood interface independently and in combination in an in vitro static blood model. Samples of fresh ovine or human blood (5 ml) were subjected to a bubbling air interface (0-100 ml/min) or negative pressure (0-600 mm Hg) separately, or in combination, for controlled periods of time and analyzed for hemolysis. Neither negative pressure nor an air interface alone increased hemolysis. However, when air and negative pressure were combined, hemolysis increased as a function of negative pressure, the air interface, and time. Moreover, when blood samples were exposed to air before initiating the test, hemolysis was four to five times greater than samples not preexposed to air. When these experiments were repeated using freshly drawn human blood, the same phenomena were observed, but the hemolysis was significantly higher than that observed in sheep blood. In this model, hemolysis is caused by combined air and negative pressure and is unrelated to either factor alone.

Measurements of emission-propagation phenomena in low-energy atmospheric-pressure helium plasma

NASA Astrophysics Data System (ADS)

Yamada, Hiromasa; Shimizu, Tetsuji; Fujiwara, Masanori; Kato, Susumu; Fujiwara, Yutaka; Itagaki, Hirotomo; Kiyama, Satoru; Kim, Jaeho; Ikehara, Sanae; Shimizu, Nobuyuki; Nakanishi, Hayao; Ikehara, Yuzuru; Sakakita, Hajime

2018-05-01

In a low-temperature atmospheric pressure plasma jet using helium gas, emission-propagation phenomena, such as streamers and striations were measured using a high-speed intensified charge-coupled device camera. A particular focus was placed on the study of the dependence of the phenomena on the distance between the nozzle of the plasma device and a target plate. When the distance decreased, a transition from the positive streamer to a spatially continuous emission resulted. A further distance reduction resulted in a new propagation mode in which the positive and negative streamers appeared alternately with different current waveforms over two cycles of applied voltage. This phenomenon may be related to residual charges of the preceding cycle when streamer propagation begins. Striation structures were observed in the tail of the positive streamer head and in the successive spatially continuous-emission region. These structures can be measured only within a shorter period than one voltage cycle.

Negative-pressure wound therapy I: the paradox of negative-pressure wound therapy.

PubMed

Kairinos, Nicolas; Solomons, Michael; Hudson, Donald A

2009-02-01

Does negative-pressure wound therapy reduce or increase the pressure of wound tissues? This seemingly obvious question has never been addressed by a study on living tissues. The aim of this study was to evaluate the nature of tissue pressure changes in relation to negative-pressure wound therapy. Three negative-pressure wound therapy dressing configurations were evaluated-circumferential, noncircumferential, and those within a cavity-on 15 human wounds, with five wounds in each category. Tissue pressure changes were recorded (using a strain gauge sensor) for each 75-mmHg increment in suction, up to -450 mmHg. In the circumferential and noncircumferential groups, tissue pressure was also measured over a 48-hour period at a set suction pressure of -125 mmHg (n = 10). In all three groups, mean tissue pressure increased proportionately to the amount of suction applied (p < 0.0005). Mean tissue pressure increments resulting from the circumferential dressings were significantly higher than those resulting from the noncircumferential (p < 0.0005) or cavity group (p < 0.0005); however, there was no significant difference between the latter two groups (p = 0.269). Over the 48-hour period, there was a significant mean reduction in the (increased) tissue pressure (p < 0.04 for circumferential and p < 0.0005 for noncircumferential), but in only three of 10 cases did this reduce to pressures less than those before dressing application. Negative-pressure wound therapy increases tissue pressure proportionately to the amount of suction, although this becomes less pronounced over 48 hours. This suggests that negative-pressure wound therapy dressings should be used with caution on tissues with compromised perfusion, particularly when they are circumferential.

In Vitro Evaluation of Evacuated Blood Collection Tubes as a Closed-Suction Surgical Drain Reservoir.

PubMed

Heiser, Brian; Okrasinski, E B; Murray, Rebecca; McCord, Kelly

The initial negative pressures of evacuated blood collection tubes (EBCT) and their in vitro performance as a rigid closed-suction surgical drain (CSSD) reservoir has not been evaluated in the scientific literature despite being described in both human and veterinary texts and journals. The initial negative pressures of EBCT sized 3, 6, 10, and 15 mL were measured and the stability of the system monitored. The pressure-to-volume curve as either air or water was added and maximal filling volumes were measured. Evacuated blood collection tubes beyond the manufacture's expiration date were evaluated for initial negative pressures and maximal filling volumes. Initial negative pressure ranged from -214 mm Hg to -528 mm Hg for EBCT within the manufacturer's expiration date. Different pressure-to-volume curves were found for air versus water. Optimal negative pressures of CSSD are debated in the literature. Drain purpose and type of exudates are factors that should be considered when deciding which EBCT size to implement. Evacuated blood collection tubes have a range of negative pressures and pressure-to-volume curves similar to previously evaluated CSSD rigid reservoirs. Proper drain management and using EBCT within labeled expiration date are important to ensure that expected negative pressures are generated.

A comparative study of negative pressure wound therapy with and without instillation of saline on wound healing.

PubMed

Omar, M; Gathen, M; Liodakis, E; Suero, E M; Krettek, C; Zeckey, C; Petri, M

2016-08-01

Negative pressure wound therapy (NPWT) has become an established treatment of traumatic and infected wounds. Negative pressure wound therapy with instillation (NPWTi) is a further development that combines the conventional NPWT with instillation of different fluids which continuously administer therapeutic reagents to the wound. The aim of this study was to compare the impact of additional saline instillation in NPWTi to NPWT alone. Between January and July 2014, consecutive patients with acute wounds of the lower limb were treated with NPWTi with saline instillation. The number of revision surgeries, length of hospital stay, and duration of treatment until final healing were recorded and compared with matched patients undergoing NPWT without instillation. There were 10 patients recruited with 10 matched controls examined restrospectivley. Patients who received NPWTi were found to have decreased time of hospitalisation (21.5 versus 26.5 days, p=0.43), and accelerated wound healing (9.0 versus 12.5 days, p=0.36) than patients who received NPWT. However, the difference in the outcomes of the patients who received NPWTi and patients who received NPWT was not found to be statisticallly significant. NPWTi with instillation of saline is a promising method and its effectiveness needs to be tested in a randomised controlled trial compared with NPWT alone. This study obtained support by KCI (Wiebsaden, Germany) for the surgical material.

Continuous negative external pressure (cNEP) reduces respiratory impairment during screening colonoscopy: a pilot study.

PubMed

Kais, Susan S; Klein, Kenneth B; Rose, Richard M; Endemann, Sarah; Coyle, Walter J

2016-06-01

Drugs administered during gastrointestinal procedures cause increased collapsibility of the upper airway, which may lead to respiratory impairment. We evaluated the ability of continuous negative external pressure (cNEP) to lessen respiratory impairment during screening colonoscopy. The initial 24 patients served as controls, while the next 30 received cNEP. cNEP was delivered by a soft silicone collar placed over the anterior neck. The primary endpoint was the frequency of respiratory impairment, defined as either: (i) a decline from baseline of > 4 % in oxygen saturation, or (ii) apnea lasting ≥ 20 seconds. Mean respiratory impairment episodes were 3.50 in the no-cNEP group vs. 1.92 in the cNEP group, a reduction of 45 % (P = 0.022). Apneas ≥ 20 seconds occurred in 74 % of the no-cNEP group and 28 % of the cNEP group (P = 0.002). While 42 % of the no-cNEP group required increased supplemental oxygen, this was true for only 10 % of the cNEP group (P = 0.01). cNEP adverse events were minimal. During screening colonoscopy, sedation-related respiratory impairment is significantly reduced by cNEP.ClinicalTrials.gov NCT01895062. © Georg Thieme Verlag KG Stuttgart · New York.

Collapsing avian community on a Hawaiian island.

PubMed

Paxton, Eben H; Camp, Richard J; Gorresen, P Marcos; Crampton, Lisa H; Leonard, David L; VanderWerf, Eric A

2016-09-01

The viability of many species has been jeopardized by numerous negative factors over the centuries, but climate change is predicted to accelerate and increase the pressure of many of these threats, leading to extinctions. The Hawaiian honeycreepers, famous for their spectacular adaptive radiation, are predicted to experience negative responses to climate change, given their susceptibility to introduced disease, the strong linkage of disease distribution to climatic conditions, and their current distribution. We document the rapid collapse of the native avifauna on the island of Kaua'i that corresponds to changes in climate and disease prevalence. Although multiple factors may be pressuring the community, we suggest that a tipping point has been crossed in which temperatures in forest habitats at high elevations have reached a threshold that facilitates the development of avian malaria and its vector throughout these species' ranges. Continued incursion of invasive weeds and non-native avian competitors may be facilitated by climate change and could also contribute to declines. If current rates of decline continue, we predict multiple extinctions in the coming decades. Kaua'i represents an early warning for the forest bird communities on the Maui and Hawai'i islands, as well as other species around the world that are trapped within a climatic space that is rapidly disappearing.

Collapsing avian community on a Hawaiian island

USGS Publications Warehouse

Paxton, Eben H.; Camp, Richard J.; Gorresen, P. Marcos; Crampton, Lisa H.; Leonard, David L.; VanderWerf, Eric

2016-01-01

The viability of many species has been jeopardized by numerous negative factors over the centuries, but climate change is predicted to accelerate and increase the pressure of many of these threats, leading to extinctions. The Hawaiian honeycreepers, famous for their spectacular adaptive radiation, are predicted to experience negative responses to climate change, given their susceptibility to introduced disease, the strong linkage of disease distribution to climatic conditions, and their current distribution. We document the rapid collapse of the native avifauna on the island of Kaua‘i that corresponds to changes in climate and disease prevalence. Although multiple factors may be pressuring the community, we suggest that a tipping point has been crossed in which temperatures in forest habitats at high elevations have reached a threshold that facilitates the development of avian malaria and its vector throughout these species’ ranges. Continued incursion of invasive weeds and non-native avian competitors may be facilitated by climate change and could also contribute to declines. If current rates of decline continue, we predict multiple extinctions in the coming decades. Kaua‘i represents an early warning for the forest bird communities on the Maui and Hawai‘i islands, as well as other species around the world that are trapped within a climatic space that is rapidly disappearing.

Acceleration of tendon-bone healing of anterior cruciate ligament graft using intermittent negative pressure in rabbits.

PubMed

Sun, Zhengming; Wang, Xiaoqing; Ling, Ming; Wang, Wei; Chang, Yanhai; Yang, Guang; Dong, Xianghui; Wu, Shixun; Wu, Xueyuan; Yang, Bo; Chen, Ming

2017-04-18

The purpose of this study was to test effects of negative pressure on tendon-bone healing after reconstruction of anterior cruciate ligament (ACL) in rabbits. Hind legs of 24 New Zealand White rabbits were randomly selected as negative pressure group and the contralateral hind legs as control. Reconstruction of the ACL was done. Joints of the negative pressure side were placed with drainage tubes connecting the micro-negative pressure aspirator. Control side was placed with ordinary drainage tubes. Drainage tubes on both sides were removed at the same time 5 days after operation. After 6 weeks, joint fluid was drawn to detect the expression levels of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α); at the same time, femur-ligament-tibia complex was obtained to determine tendon graft tension and to observe the histomorphology, blood vessels of the tendon-bone interface, and expression of vascular endothelial growth factor (VEGF). The maximum load breakage of tendon graft was significantly greater in the negative pressure group than in the control group (P < 0.05). Histological studies of the tendon-bone interface found that there was more new bone formation containing chondroid cells and aligned connective tissue in the negative pressure group than in the control group. Expression of VEGF was higher in the negative pressure group than in the control group (P < 0.01). Content of IL-1β and TNF-α in synovial fluid is lower in the negative pressure group than in the control group (P < 0.01). Intermittent negative pressure plays an active role in tendon-bone healing and creeping substitution of ACL reconstruction in the rabbits.

Hemolysis During Open-Heart Surgery With Vacuum-Assisted Venous Drainage at Different Negative Pressures in Pediatric Patients Weighing Less Than 10 kilograms.

PubMed

Kwak, Jae Gun; Lee, Jinkwon; Park, Minkyoung; Seo, Yu-Jin; Lee, Chang-Ha

2017-03-01

This study examined the degree of hemolysis during vacuum-assisted venous drainage at different negative pressures to identify an adequate negative pressure that provides effective venous drainage without significant hemolysis in open-heart surgery in children weighing less than 10 kg. Patients weighing less than 10 kg who underwent surgery for ventricular septal defect or atrial septal defect from 2011 to 2014 were enrolled. We used one of four negative pressures (20, 30, 40, or 60 mm Hg) for each patient. We measured haptoglobin, plasma hemoglobin, aspartate aminotransferase, and lactate dehydrogenase levels in the patients' blood three times perioperatively and determined the potential correlation between the change in each parameter with the level of negative pressure. Forty-six patients were enrolled in this study (mean age: 7.1 ± 7.0 months, mean body weight: 6.1 ± 1.8 kg). There were no significant differences according to the degree of negative pressure with respect to patient age, body weight, cardiopulmonary bypass (CPB) time, aorta cross-clamping time, blood flow during CPB, or lowest body temperature. All parameters that we measured reflected progression of hemolysis during CPB; however, the degree of change in the parameters did not correlate with negative pressure. In pediatric patients weighing less than 10 kg, the change in the degree of hemolysis did not differ with the amount of negative pressure. We may apply negative pressures up to 60 mm Hg without increasing the risk of hemolysis, with almost same the level of hemolysis using negative pressures of 20, 30, and 40 mm Hg for effective venous drainage and an ideal operative field during open-heart surgery.

The use of isoprene as a novel dopant in negative ion atmospheric pressure photoionization mass spectrometry coupled to high-performance liquid chromatography.

PubMed

Dousty, Faezeh; O'Brien, Rob

2015-06-15

As in the case with positive ion atmospheric pressure photoionization (PI-APPI), the addition of dopants significantly improves the sensitivity of negative ion APPI (NI-APPI). However, the research on dopant-assisted-NI-APPI has been quite limited compared to the studies on dopant-assisted PI-APPI. This work presents the potential of isoprene as a novel dopant for NI-APPI. Thirteen compounds, possessing suitable gas-phase ion energetic properties in order to make stable negative ions, were selected. Dopants were continuously introduced into a tee junction prior to the ion source through a fused-silica capillary, while analytes were directly injected into the same tee. Then both were mixed with the continuous solvent from high-performance liquid chromatography (HPLC), nebulized, and entered the source. The nebulized stream was analyzed by APPI tandem quadrupole mass spectrometry in the negative ion mode. The results obtained using isoprene were compared with those obtained by using toluene as a dopant and dopant-free NI-APPI. Isoprene enhanced the ionization intensities of the studied compounds, which were found to be comparable and, in some cases, more effective than toluene. The mechanisms leading to the observed set of negative analyte ions were also discussed. Because in NI-APPI, thermal electrons, which are produced during the photoionization of a dopant, are considered the main reagent ions, both isoprene and toluene promoted the ionization of analytes through the same mechanisms, as expected. Isoprene was shown to perform well as a novel dopant for NI-APPI. Isoprene has a high photoabsorption cross section in the VUV region; therefore, its photoionization leads to a highly effective production of thermal electrons, which further promotes the ionization of analytes. In addition, isoprene is environmentally benign and less toxic compared to currently used dopants. Copyright © 2015 John Wiley & Sons, Ltd.

Evaluation of Cutaneous Blood Flow During Lower Body Negative Pressure to Prevent Orthostatic Intolerance of Bedrest

NASA Technical Reports Server (NTRS)

Rubin, Marilyn

1991-01-01

Orthostatic tolerance is markedly impaired in most of the crewmembers during space flight and could seriously compromise crew safety during and immediately after landing. NASA investigators are studying the use of lower body negative pressure (LBNP) as a countermeasure to this intolerance. It is hypothesized that the continuously changing vascular pressure induced by sinusoidal LBNP with an additional countermeasure of salt and water will help crewmembers to be in a more acceptable physiologic condition to enter the earth's atmosphere. In ground based studies, subjects on bedrest provide the model for studying the physiologic effects of weightlessness. When subjects are treated with sinusoidal LBNP, negative pressures ranging from 0 to -60 mm/Hg are administered during a two hour period. This increases body fluids in the legs and lower body. This paper reports the results of two subjects who were placed on bedrest for six days. The subjects were randomly selected for either the control or treatment mode. The subject receiving the treatment mode ingested salt tablets and water on day 4 of the bedrest period. A ramp LBNP of two hours was next administered to this subject. The control subject did not receive anything during the bedrest period. Laser Doppler was used to measure the cutaneous blood flow of the forearm and calf to monitor vasoconstrictor effects of the baroreceptor reflex. Data indicated that skin blood flow in the treatment subject was higher than baseline in the forearm while the skin blood flow was decreased in the control subject.

Continuous Positive Airway Pressure During Exercise Improves Walking Time in Patients Undergoing Inpatient Cardiac Rehabilitation After Coronary Artery Bypass Graft Surgery: A RANDOMIZED CONTROLLED TRIAL.

PubMed

Pantoni, Camila Bianca Falasco; Di Thommazo-Luporini, Luciana; Mendes, Renata Gonçalves; Caruso, Flávia Cristina Rossi; Mezzalira, Daniel; Arena, Ross; Amaral-Neto, Othon; Catai, Aparecida Maria; Borghi-Silva, Audrey

2016-01-01

Continuous positive airway pressure (CPAP) has been used as an effective support to decrease the negative pulmonary effects of coronary artery bypass graft (CABG) surgery. However, it is unknown whether CPAP can positively influence patients undergoing CABG during exercise. This study evaluated the effectiveness of CPAP on the first day of ambulation after CABG in patients undergoing inpatient cardiac rehabilitation (CR). Fifty-four patients after CABG surgery were randomly assigned to receive either inpatient CR and CPAP (CPG) or standard CR without CPAP (CG). Cardiac rehabilitation included walking and CPAP pressures were set between 10 to 12 cmH2O. Participants were assessed on the first day of walking at rest and during walking. Outcome measures included breathing pattern variables, exercise time in seconds (ETs), dyspnea/leg effort ratings, and peripheral oxygen saturation (SpO2). Twenty-seven patients (13 CPG vs 14 CG) completed the study. Compared with walking without noninvasive ventilation assistance, CPAP increased ETs by 43.4 seconds (P = .040) during walking, promoted better thoracoabdominal coordination, increased ventilation during walking by 12.5 L/min (P = .001), increased SpO2 values at the end of walking by 2.6% (P = .016), and reduced dyspnea ratings by 1 point (P = .008). Continuous positive airway pressure can positively influence exercise tolerance, ventilatory function, and breathing pattern in response to a single bout of exercise after CABG.

The phase diagram of water at negative pressures: virtual ices.

PubMed

Conde, M M; Vega, C; Tribello, G A; Slater, B

2009-07-21

The phase diagram of water at negative pressures as obtained from computer simulations for two models of water, TIP4P/2005 and TIP5P is presented. Several solid structures with lower densities than ice Ih, so-called virtual ices, were considered as possible candidates to occupy the negative pressure region of the phase diagram of water. In particular the empty hydrate structures sI, sII, and sH and another, recently proposed, low-density ice structure. The relative stabilities of these structures at 0 K was determined using empirical water potentials and density functional theory calculations. By performing free energy calculations and Gibbs-Duhem integration the phase diagram of TIP4P/2005 was determined at negative pressures. The empty hydrates sII and sH appear to be the stable solid phases of water at negative pressures. The phase boundary between ice Ih and sII clathrate occurs at moderate negative pressures, while at large negative pressures sH becomes the most stable phase. This behavior is in reasonable agreement with what is observed in density functional theory calculations.

The Relationships between Air Exposure, Negative Pressure and Hemolysis

PubMed Central

Pohlmann, Joshua R.; Toomasian, John M.; Hampton, Claire E.; Cook, Keith E.; Annich, Gail M.; Bartlett, Robert H.

2013-01-01

The purpose of this study was to describe the hemolytic effects of both negative pressure and an air-blood interface independently and in combination in an in-vitro static blood model. Samples of fresh ovine or human blood (5 mL) were subjected to a bubbling air interface (0–100 mL/min) or negative pressure (0–600 mmHg) separately, or in combination, for controlled periods of time, and analyzed for hemolysis. Neither negative pressure nor an air interface alone increased hemolysis. However, when air and negative pressure were combined, hemolysis increased as a function of negative pressure, the air interface, and time. Moreover, when blood samples were exposed to air prior to initiating the test, hemolysis was 4–5 times greater than samples not pre-exposed to air. When these experiments were repeated using freshly drawn human blood the same phenomena were observed, but the hemolysis was significantly higher than that observed in sheep blood. In this model, hemolysis is caused by combined air and negative pressure and is unrelated to either factor alone. PMID:19730004

Negative-pressure and low-pressure hydrocephalus: the role of cerebrospinal fluid leaks resulting from surgical approaches to the cranial base.

PubMed

Filippidis, Aristotelis S; Kalani, M Yashar S; Nakaji, Peter; Rekate, Harold L

2011-11-01

Negative-pressure and low-pressure hydrocephalus are rare clinical entities that are frequently misdiagnosed. They are characterized by recurrent episodes of shunt failure because the intracranial pressure is lower than the opening pressure of the valve. In this report the authors discuss iatrogenic CSF leaks as a cause of low- or negative-pressure hydrocephalus after approaches to the cranial base. The authors retrospectively reviewed cases of low-pressure or negative-pressure hydrocephalus presenting after cranial approaches complicated with a CSF leak at their institution. Three patients were identified. Symptoms of high intracranial pressure and ventriculomegaly were present, although the measured pressures were low or negative. A blocked communication between the ventricles and the subarachnoid space was documented in 2 of the cases and presumed in the third. Shunt revisions failed repeatedly. In all cases, temporary clinical and radiographic improvement resulted from external ventricular drainage at subatmospheric pressures. The CSF leaks were sealed and CSF communication was reestablished operatively. In 1 case, neck wrapping was used with temporary success. Negative-pressure or low-pressure hydrocephalus associated with CSF leaks, especially after cranial base approaches, is difficult to treat. The solution often requires the utilization of subatmospheric external ventricular drains to establish a lower ventricular drainage pressure than the drainage pressure created in the subarachnoid space, where the pressure is artificially lowered by the CSF leak. Treatment involves correction of the CSF leak, neck wrapping to increase brain turgor and allow the pressure in the ventricles to rise to the level of the opening pressure of the valve, and reestablishing the CSF route.

Incisional Negative Pressure Wound Therapy in High Risk Patients Undergoing Panniculectomy: A Prospective Randomized Controlled Trial

ClinicalTrials.gov

2018-01-16

Complications Wounds; Negative Pressure Wound Therapy; Wound Healing Delayed; Incisional; Panniculectomy; Incisional Negative Pressure Wound Therapy; Incisional Vac; Wound Vac; Obese; Renal Failure; Kidney Transplant; Complications; Wound Healing Complication

Effects of Aerobic Exercise Training on Psychosocial Status and Serum Uric Acid in Men with Essential Hypertension: A Randomized Controlled Trial

PubMed Central

Lamina, S; Okoye, GC

2012-01-01

Background: Chronic psychosocial stress and serum uric acid (SUA) level have been implicated in the etiology and cardiovascular events risk factors in hypertension. Studies have reported significant benefit of exercise in the overall management of hypertension. However, studies on the effect of exercise on psychosocial stress and SUA in the management of hypertension seem scanty. Aim: The aim of this study was to determine the effect of continuous training program on SUA and psychosocial status of black African (Nigerian) population with hypertension. Subjects and Methods: Age-matched randomized controlled trial was used; subjects with diagnosis of hypertension attending the hypertensive clinic of Murtala Muhammed Specialist Hospital (MMSH), Kano, Nigeria form the population for the study. Two hundred and seventeen subjects with mild to moderate (systolic blood pressure (SBP) between 140 and180 and diastolic blood pressure (DBP) between 90 and 109 mmHg) essential hypertension were grouped into continuous (112) and control groups (105). The continuous group involved in an 8 weeks continuous training (60%-79% HR max) of between 45 and 60 min, 3 times per week, while the controls group remain sedentary. SBP, DBP, SUA, VO2 max and psychosocial status were assessed. Student t-test and Pearson correlation test were used in data analysis. Results: The study revealed significant beneficial effect of continuous training programs on VO2 max, SBP, DBP, SUA, and psychosocial status (P < 0.05). Psychosocial status and SUA was significantly and positively and negatively correlated respectively with VO2 max at P < 0.01. Conclusions: This study concludes and supports the recommendations of moderate intensity (continuous) training program in blood pressure reduction, SUA and psychosocial stress management in hypertension. PMID:23439606

Negative pressure wound therapy for the treatment of infected wounds with exposed knee joint after patellar fracture.

PubMed

Lee, Sang Yang; Niikura, Takahiro; Miwa, Masahiko; Sakai, Yoshitada; Oe, Keisuke; Fukazawa, Takahiro; Kawakami, Yohei; Kurosaka, Masahiro

2011-06-14

Treatment of soft tissue defects with exposed bones and joints, resulting from trauma, infection, and surgical complications, represents a major challenge. The introduction of negative pressure wound therapy has changed many wound management practices. Negative pressure wound therapy has recently been used in the orthopedic field for management of traumatic or open wounds with exposed bone, nerve, tendon, and orthopedic implants. This article describes a case of a patient with a large soft tissue defect and exposed knee joint, in which negative pressure wound therapy markedly improved wound healing. A 50-year-old man presented with an ulceration of his left knee with exposed joint, caused by severe wound infections after open reduction and internal fixation of a patellar fracture. After 20 days of negative pressure wound therapy, a granulated wound bed covered the exposed bones and joint.To our knowledge, this is the first report of negative pressure wound therapy used in a patient with a large soft tissue defect with exposed knee joint. Despite the chronic wound secondary to infection, healing was achieved through the use of the negative pressure wound therapy, thus promoting granulation tissue formation and closing the joint. We suggest negative pressure wound therapy as an alternative option for patients with lower limb wounds containing exposed bones and joints when free flap transfer is contraindicated. Our result added to the growing evidence that negative pressure wound therapy is a useful adjunctive treatment for open wounds around the knee joint. Copyright 2011, SLACK Incorporated.

An association of platelet indices with blood pressure in Beijing adults: Applying quadratic inference function for a longitudinal study.

PubMed

Yang, Kun; Tao, Lixin; Mahara, Gehendra; Yan, Yan; Cao, Kai; Liu, Xiangtong; Chen, Sipeng; Xu, Qin; Liu, Long; Wang, Chao; Huang, Fangfang; Zhang, Jie; Yan, Aoshuang; Ping, Zhao; Guo, Xiuhua

2016-09-01

The quadratic inference function (QIF) method becomes more acceptable for correlated data because of its advantages over generalized estimating equations (GEE). This study aimed to evaluate the relationship between platelet indices and blood pressure using QIF method, which has not been studied extensively in real data settings.A population-based longitudinal study was conducted in Beijing from 2007 to 2012, and the median of follow-up was 6 years. A total of 6515 cases, who were aged between 20 and 65 years at baseline and underwent routine physical examinations every year from 3 Beijing hospitals were enrolled to explore the association between platelet indices and blood pressure by QIF method. The original continuous platelet indices were categorized into 4 levels (Q1-Q4) using the 3 quartiles of P25, P50, and P75 as a critical value. GEE was performed to make a comparison with QIF.After adjusting for age, usage of drugs, and other confounding factors, mean platelet volume was negatively associated with diastolic blood pressure (DBP) (Equation is included in full-text article.)in males and positively linked with systolic blood pressure (SBP) (Equation is included in full-text article.). Platelet distribution width was negatively associated with SBP (Equation is included in full-text article.). Blood platelet count was associated with DBP (Equation is included in full-text article.)in males.Adults in Beijing with prolonged exposure to extreme value of platelet indices have elevated risk for future hypertension and evidence suggesting using some platelet indices for early diagnosis of high blood pressure was provided.

Treatment of hardware infection after osteosynthesis of lower leg using negative pressure wound therapy and transforming powder dressing.

PubMed

Marinović, Marin; Ivandcić, Aldo; Spanjol, Josip; Pina, Maja; Bakota, Bore; Bandalović, Ante; Cukeljs, Fabijan

2014-12-01

Fractures of the distal part of the lower leg are more common in everyday practice and traumatology. In young and active patients these injuries are mainly caused by high energy trauma. They are treated with external fixator in first step, and in second step, after sanation of the soft tissue, with open reduction and internal fixation (ORIF). It is very safe and effective method of treatment. Treatment of the infections that occur in the early postoperative period after open reduction and internal fixation represents a great problem and challenge for surgeons. It is widely accepted that the presence of deep infection can't be cured in the presence of hardware. However, removal of hardware in the presence of unhealed fractures significantly complicates sanation of infection and fracture itself We have decided to present a 35-years-old patient with a hardware infection with present chronic wound with hardware exposed eight months after the first operation and six months after second operation. The wound measured one centimeter in diameter with cell detritus and bad granulations tissue inside the wound. Hardwre was exposed in the depth of the wound.The secretion was minimal. Negative Pressure Wound Therapy (NPWT) was applicated after debridemet and lavage performed in ambulatory conditions. The starting therapy was continuously -125 mm Hg of vacuum. After five days of NPWT the defect was partially filled with granula- tion tissue. For another five days we continue with NPWT with the same values of-125 mm Hg pressure but in the inter- mitent mode. After that period we used transforming powder dressing for covering and protection of the wound with was filled with granulation tissue. Five days later, wound was completely healed with epithelisation. After four months of patient follow-up, we found the wound is completely repaired. The patient denies pain and has continued orderly flow of fracture healing, with no signs of infection.

Experimental evidence for negative turgor pressure in small leaf cells of Robinia pseudoacacia L versus large cells of Metasequoia glyptostroboides Hu et W.C.Cheng. 1. Evidence from pressure-volume curve analysis of dead tissue.

PubMed

Yang, Dongmei; Pan, Shaoan; Ding, Yiting; Tyree, Melvin T

2017-03-01

This paper provides a mini-review of evidence for negative turgor pressure in leaf cells starting with experimental evidence in the late 1950s and ending with biomechanical models published in 2014. In the present study, biomechanical models were used to predict how negative turgor pressure might be manifested in dead tissue, and experiments were conducted to test the predictions. The main findings were as follows: (i) Tissues killed by heating to 60 or 80 °C or by freezing in liquid nitrogen all became equally leaky to cell sap solutes and all seemed to pass freely through the cell walls. (ii) Once cell sap solutes could freely pass the cell walls, the shape of pressure-volume curves was dramatically altered between living and dead cells. (iii) Pressure-volume curves of dead tissue seem to measure negative turgor defined as negative when inside minus outside pressure is negative. (iv) Robinia pseudoacacia leaves with small palisade cells had more negative turgor than Metasequoia glyptostroboides with large cells. (v) The absolute difference in negative turgor between R. pseudoacacia and M. glyptostroboides approached as much as 1.0 MPa in some cases. The differences in the manifestation of negative turgor in living versus dead tissue are discussed. © 2016 John Wiley & Sons Ltd.

Non-linear Heart Rate and Blood Pressure Interaction in Response to Lower-Body Negative Pressure

PubMed Central

Verma, Ajay K.; Xu, Da; Garg, Amanmeet; Cote, Anita T.; Goswami, Nandu; Blaber, Andrew P.; Tavakolian, Kouhyar

2017-01-01

Early detection of hemorrhage remains an open problem. In this regard, blood pressure has been an ineffective measure of blood loss due to numerous compensatory mechanisms sustaining arterial blood pressure homeostasis. Here, we investigate the feasibility of causality detection in the heart rate and blood pressure interaction, a closed-loop control system, for early detection of hemorrhage. The hemorrhage was simulated via graded lower-body negative pressure (LBNP) from 0 to −40 mmHg. The research hypothesis was that a significant elevation of causal control in the direction of blood pressure to heart rate (i.e., baroreflex response) is an early indicator of central hypovolemia. Five minutes of continuous blood pressure and electrocardiogram (ECG) signals were acquired simultaneously from young, healthy participants (27 ± 1 years, N = 27) during each LBNP stage, from which heart rate (represented by RR interval), systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) were derived. The heart rate and blood pressure causal interaction (RR↔SBP and RR↔MAP) was studied during the last 3 min of each LBNP stage. At supine rest, the non-baroreflex arm (RR→SBP and RR→MAP) showed a significantly (p < 0.001) higher causal drive toward blood pressure regulation compared to the baroreflex arm (SBP→RR and MAP→RR). In response to moderate category hemorrhage (−30 mmHg LBNP), no change was observed in the traditional marker of blood loss i.e., pulse pressure (p = 0.10) along with the RR→SBP (p = 0.76), RR→MAP (p = 0.60), and SBP→RR (p = 0.07) causality compared to the resting stage. Contrarily, a significant elevation in the MAP→RR (p = 0.004) causality was observed. In accordance with our hypothesis, the outcomes of the research underscored the potential of compensatory baroreflex arm (MAP→RR) of the heart rate and blood pressure interaction toward differentiating a simulated moderate category hemorrhage from the resting stage. Therefore, monitoring baroreflex causality can have a clinical utility in making triage decisions to impede hemorrhage progression. PMID:29114227

Temporal evolution of atmosphere pressure plasma jets driven by microsecond pulses with positive and negative polarities

NASA Astrophysics Data System (ADS)

Shao, Tao; Yang, Wenjin; Zhang, Cheng; Fang, Zhi; Zhou, Yixiao; Schamiloglu, Edl

2014-09-01

Current-voltage characteristics, discharge images, and optical spectra of atmospheric pressure plasma jets (APPJs) are studied using a microsecond pulse length generator producing repetitive output pulses with different polarities. The experimental results show that the APPJs excited by the pulses with positive polarity have longer plume, faster propagation speed, higher power, and more excited species, such as \\text{N}2 , O, He, \\text{N}2+ , than that with the negatively excited APPJs. The images taken using an intensified charge-coupled device show that the APPJs excited by pulses with positive polarity are characterized by a bullet-like structure, while the APPJs excited by pulses with negative polarity are continuous. The propagation speed of the APPJs driven by a microsecond pulse length generator is about tens of km/s, which is similar to the APPJs driven by a kHz frequency sinusoidal voltage source. The analysis shows that the space charge accumulation effect plays an important role during the discharge. The transient enhanced electric field induced by the accumulated ions between the needle-like electrode and the nozzle in the APPJs excited by pulses with negative polarity enhances electron field emission from the cathode, which is illustrated by the bright line on the time-integrated images. This makes the shape of the APPJ excited using pulses with negative polarity different from the bullet-like shape of the APPJs excited by pulses with positive polarity.

Use of a portable, single-use negative pressure wound therapy device in home care patients with low to moderately exuding wounds: a case series.

PubMed

Hurd, Theresa; Trueman, Paul; Rossington, Alan

2014-03-01

Negative pressure wound therapy (NPWT) is widely used in the management of acute and chronic wounds. The purpose of this 8-week study was to evaluate outcomes of using a new canisterless, portable, single-use NPWT system in patients with wounds treated in a Canadian community healthcare setting. The device is designed to provide negative pressure at 80±20 mm Hg, 24 hours a day of continuous usage, for a maximum wear time of 7 days. Data on wound outcomes, including exudate levels, wound appearance, and wound area, were collected weekly by a Registered Nurse as part of routine practice. When treatment was discontinued, patients and nurses were asked to rate their satisfaction with the device. Data from patients who had used a conventional NPWT device to manage their wounds were retrospectively abstracted from their medical records. In the prospective study, conducted between October 2011 and July 2012, 326 patients (median age=61 years; range 17-91 years) with wounds of mixed etiology (53 pressure ulcers, 21 venous leg ulcers, 16 diabetic foot ulcers, and 15 traumatic and 221 surgical wounds) were treated for a maximum of 8 weeks with the portable NPWT device. The majority of patients (228 out of 326; 68%) achieved complete wound closure within 8 weeks of treatment. The Kaplan-Meier estimate of median time to healing of all wounds was 9 weeks. The majority of patients (318 patients, 97%) reported they were pleased or satisfied with the dressing performance. Nurses indicated satisfaction with the dressing performance for all but two patients (99%). The majority (89%) of patients managed with conventional NPWT (n=539) had an open surgical wound with moderate or high levels of exudate. Healing rates in the portable and conventional NPWT group were similar (10% to 11% per week). Portable, single-use NPWT has the potential to deliver good wound outcomes in community care settings and simplify the use of negative pressure for nurses and patients. Additional research is needed to evaluate treatment efficacy and cost effectiveness.

Social judgment of abortion: a black-sheep effect in a Catholic sheepfold.

PubMed

Bègue, L

2001-10-01

French Catholic participants (N = 340) with high or low religious identification read 1 of 8 scenarios presented as an interview with a female target 2 months after she had had an abortion. The experimental device varied situational pressure (pressure vs. no pressure), the target's religious social identity (Catholic vs. neutral), and the consequences of abortion for the target (positive vs. negative). The participants then rated the acceptability of the target's decision. The participants judged abortion more negatively in the no-pressure condition. Moreover, the participants with high religious identification judged abortion more negatively than did those with low religious identification. In partial support of a black-sheep effect, the participants with high religious identification judged the Catholic target more negatively than they judged the neutral one in some conditions (pressure, negative consequences). In other conditions (no pressure, both positive and negative consequences), the participants with low religious identification judged the Catholic target more positively than they judged the neutral one.

Skin blood flow with elastic compressive extravehicular activity space suit.

PubMed

Tanaka, Kunihiko; Gotoh, Taro M; Morita, Hironobu; Hargens, Alan R

2003-10-01

During extravehicular activity (EVA), current space suits are pressurized with 100% oxygen at approximately 222 mmHg. A tight elastic garment, or mechanical counter pressure (MCP) suit that generates pressure by compression, may have several advantages over current space suit technology. In this study, we investigated local microcirculatory effects produced with negative ambient pressure with an MCP sleeve. The MCP glove and sleeve generated pressures similar to the current space suit. MCP remained constant during negative pressure due to unchanged elasticity of the material. Decreased skin capillary blood flow and temperature during MCP compression was counteracted by greater negative pressure or a smaller pressure differential.

Two-structure thermodynamics for the TIP4P/2005 model of water covering supercooled and deeply stretched regions.

PubMed

Biddle, John W; Singh, Rakesh S; Sparano, Evan M; Ricci, Francesco; González, Miguel A; Valeriani, Chantal; Abascal, José L F; Debenedetti, Pablo G; Anisimov, Mikhail A; Caupin, Frédéric

2017-01-21

One of the most promising frameworks for understanding the anomalies of cold and supercooled water postulates the existence of two competing, interconvertible local structures. If the non-ideality in the Gibbs energy of mixing overcomes the ideal entropy of mixing of these two structures, a liquid-liquid phase transition, terminated at a liquid-liquid critical point, is predicted. Various versions of the "two-structure equation of state" (TSEOS) based on this concept have shown remarkable agreement with both experimental data for metastable, deeply supercooled water and simulations of molecular water models. However, existing TSEOSs were not designed to describe the negative pressure region and do not account for the stability limit of the liquid state with respect to the vapor. While experimental data on supercooled water at negative pressures may shed additional light on the source of the anomalies of water, such data are very limited. To fill this gap, we have analyzed simulation results for TIP4P/2005, one of the most accurate classical water models available. We have used recently published simulation data, and performed additional simulations, over a broad range of positive and negative pressures, from ambient temperature to deeply supercooled conditions. We show that, by explicitly incorporating the liquid-vapor spinodal into a TSEOS, we are able to match the simulation data for TIP4P/2005 with remarkable accuracy. In particular, this equation of state quantitatively reproduces the lines of extrema in density, isothermal compressibility, and isobaric heat capacity. Contrary to an explanation of the thermodynamic anomalies of water based on a "retracing spinodal," the liquid-vapor spinodal in the present TSEOS continues monotonically to lower pressures upon cooling, influencing but not giving rise to density extrema and other thermodynamic anomalies.

Accuracy of continuous noninvasive arterial pressure monitoring in living-liver donors during transplantation.

PubMed

Araz, Coskun; Zeyneloglu, Pinar; Pirat, Arash; Veziroglu, Nukhet; Camkiran Firat, Aynur; Arslan, Gulnaz

2015-04-01

Hemodynamic monitoring is vital during liver transplant surgeries because distinct hemodynamic changes are expected. The continuous noninvasive arterial pressure (CNAP) monitor is a noninvasive device for continuous arterial pressure measurement by a tonometric method. This study compared continuous noninvasive arterial pressure monitoring with invasive direct arterial pressure monitoring in living-liver donors during transplant. There were 40 patients analyzed while undergoing hepatic lobectomy for liver transplant. Invasive pressure monitoring was established at the radial artery and continuous noninvasive arterial pressure monitoring using a finger sensor was recorded simultaneously from the contralateral arm. Systolic, diastolic, and mean arterial pressures from the 2 methods were compared. Correlation between the 2 methods was calculated. A total of 5433 simultaneous measurements were obtained. For systolic arterial blood pressure, 55% continuous noninvasive arterial pressure measurements were within 10% direct arterial measurement; the correlation was 0.479, continuous noninvasive arterial pressure bias was -0.3 mm Hg, and limits of agreement were 32.0 mm Hg. For diastolic arterial blood pressure, 50% continuous noninvasive arterial pressure measurements were within 10% direct arterial measurement; the correlation was 0.630, continuous noninvasive arterial pressure bias was -0.4 mm Hg, and limits of agreement were 21.1 mm Hg. For mean arterial blood pressure, 60% continuous noninvasive arterial pressure measurements were within 10% direct arterial measurement; the correlation was 0.692, continuous noninvasive arterial pressure bias was +0.4 mm Hg, and limits of agreement were 20.8 mm Hg. The 2 monitoring techniques did not show acceptable agreement. Our results suggest that continuous noninvasive arterial pressure monitoring is not equivalent to invasive arterial pressure monitoring in donors during living-donor liver transplant.

21 CFR 868.5935 - External negative pressure ventilator.

Code of Federal Regulations, 2010 CFR

2010-04-01

... ventilator. (a) Identification. An external negative pressure ventilator (e.g., iron lung, cuirass) is a device chamber that is intended to support a patient's ventilation by alternately applying and releasing external negative pressure over the diaphragm and upper trunk of the patient. (b) Classification. Class II...

A possible cause of the AO polarity reversal from winter to summer in 2010 and its relation to hemispheric extreme summer weather

NASA Astrophysics Data System (ADS)

Otomi, Yuriko; Tachibana, Yoshihiro; Nakamura, Tetsu

2013-04-01

In 2010, the Northern Hemisphere, in particular Russia and Japan, experienced an abnormally hot summer characterized by record-breaking warm temperatures and associated with a strongly positive Arctic Oscillation (AO), that is, low pressure in the Arctic and high pressure in the midlatitudes. In contrast, the AO index the previous winter and spring (2009/2010) was record-breaking negative. The AO polarity reversal that began in summer 2010 can explain the abnormally hot summer. The winter sea surface temperatures (SST) in the North Atlantic Ocean showed a tripolar anomaly pattern—warm SST anomalies over the tropics and high latitudes and cold SST anomalies over the midlatitudes—under the influence of the negative AO. The warm SST anomalies continued into summer 2010 because of the large oceanic heat capacity. A model simulation strongly suggested that the AO-related summertime North Atlantic oceanic warm temperature anomalies remotely caused blocking highs to form over Europe, which amplified the positive summertime AO. Thus, a possible cause of the AO polarity reversal might be the "memory" of the negative winter AO in the North Atlantic Ocean, suggesting an interseasonal linkage of the AO in which the oceanic memory of a wintertime negative AO induces a positive AO in the following summer. Understanding of this interseasonal linkage may aid in the long-term prediction of such abnormal summer events.

A possible cause of the AO polarity reversal from winter to summer in 2010 and its relation to hemispheric extreme hot summer

NASA Astrophysics Data System (ADS)

Tachibana, Yoshihiro; Otomi, Yuriko; Nakamura, Tetsu

2013-04-01

In 2010, the Northern Hemisphere, in particular Russia and Japan, experienced an abnormally hot summer characterized by record-breaking warm temperatures and associated with a strongly positive Arctic Oscillation (AO), that is, low pressure in the Arctic and high pressure in the midlatitudes. In contrast, the AO index the previous winter and spring (2009/2010) was record-breaking negative. The AO polarity reversal that began in summer 2010 can explain the abnormally hot summer. The winter sea surface temperatures (SST) in the North Atlantic Ocean showed a tripolar anomaly pattern—warm SST anomalies over the tropics and high latitudes and cold SST anomalies over the midlatitudes—under the influence of the negative AO. The warm SST anomalies continued into summer 2010 because of the large oceanic heat capacity. A model simulation strongly suggested that the AO-related summertime North Atlantic oceanic warm temperature anomalies remotely caused blocking highs to form over Europe, which amplified the positive summertime AO. Thus, a possible cause of the AO polarity reversal might be the "memory" of the negative winter AO in the North Atlantic Ocean, suggesting an interseasonal linkage of the AO in which the oceanic memory of a wintertime negative AO induces a positive AO in the following summer. Understanding of this interseasonal linkage may aid in the long-term prediction of such abnormal summer events.

Effect of Negative Pressure on Proliferation, Virulence Factor Secretion, Biofilm Formation, and Virulence-Regulated Gene Expression of Pseudomonas aeruginosa In Vitro

PubMed Central

Wang, Guo-Qi; Li, Tong-Tong; Li, Zhi-Rui; Zhang, Li-Cheng

2016-01-01

Objective. To investigate the effect of negative pressure conditions induced by NPWT on P. aeruginosa. Methods. P. aeruginosa was cultured in a Luria–Bertani medium at negative pressure of −125 mmHg for 24 h in the experimental group and at atmospheric pressure in the control group. The diameters of the colonies of P. aeruginosa were measured after 24 h. ELISA kit, orcinol method, and elastin-Congo red assay were used to quantify the virulence factors. Biofilm formation was observed by staining with Alexa Fluor® 647 conjugate of concanavalin A (Con A). Virulence-regulated genes were determined by quantitative RT-PCR. Results. As compared with the control group, growth of P. aeruginosa was inhibited by negative pressure. The colony size under negative pressure was significantly smaller in the experimental group than that in the controls (p < 0.01). Besides, reductions in the total amount of virulence factors were observed in the negative pressure group, including exotoxin A, rhamnolipid, and elastase. RT-PCR results revealed a significant inhibition in the expression level of virulence-regulated genes. Conclusion. Negative pressure could significantly inhibit the growth of P. aeruginosa. It led to a decrease in the virulence factor secretion, biofilm formation, and a reduction in the expression level of virulence-regulated genes. PMID:28074188

The SNaP system: biomechanical and animal model testing of a novel ultraportable negative-pressure wound therapy system.

PubMed

Fong, Kenton D; Hu, Dean; Eichstadt, Shaundra; Gupta, Deepak M; Pinto, Moshe; Gurtner, Geoffrey C; Longaker, Michael T; Lorenz, H Peter

2010-05-01

Negative-pressure wound therapy is traditionally achieved by attaching an electrically powered pump to a sealed wound bed and applying subatmospheric pressure by means of gauze or foam. The Smart Negative Pressure (SNaP) System (Spiracur, Inc., Sunnyvale, Calif.) is a novel ultraportable negative-pressure wound therapy system that does not require an electrically powered pump. Negative pressure produced by the SNaP System, and a powered pump, the wound vacuum-assisted closure advanced-therapy system (Kinetic Concepts, Inc., San Antonio, Texas), were compared in vitro using bench-top pressure sensor testing and microstrain and stress testing with pressure-sensitive film and micro-computed tomographic scan analysis. In addition, to test in vivo efficacy, 10 rats underwent miniaturized SNaP (mSNaP) device placement on open wounds. Subject rats were randomized to a system activation group (approximately -125 mmHg) or a control group (atmospheric pressure). Wound measurements and histologic data were collected for analysis. Bench measurement revealed nearly identical negative-pressure delivery and mechanical strain deformation patterns between both systems. Wounds treated with the mSNaP System healed faster, with decreased wound size by postoperative day 7 (51 percent versus 12 percent reduction; p < 0.05) and had more rapid complete reepithelialization (21 days versus 32 days; p < 0.05). The mSNaP device also induced robust granulation tissue formation. The SNaP System and an existing electrically powered negative-pressure wound therapy system have similar biomechanical properties and functional wound-healing benefits. The potential clinical efficacy of the SNaP device for the treatment of wounds is supported.

Impacts and Risks of Migration and Refugee Flows in Africa

DTIC Science & Technology

2012-03-12

In Africa, as in other parts of the world , border management systems are coming under increasing pressure from large flows of persons moving across...management globally have been and will continue to be strongly affected by security concerns. Some regions in the world have been the subject of attacks...and many parts of the world . Also, the presence of large numbers of displaced persons in refugee camps and IDP hosting areas can have negative

A technological advance for 21st century obstetricians: the electronically-controlled vacuum extractor.

PubMed

Perone, Nicola

2018-04-25

To describe an innovative electronically-controlled vacuum extractor (VE) in detail and to illustrate its performance characteristics, as observed in a laboratory study. Thirty simulated, vacuum-assisted deliveries. (1) The ability to measure in real-time of the pull applied and to sound an alert, when the traction approaches the negative pressure under the cup, to prevent its detachment. (2) The recording and printing of a graphic representation of the pull applied (vacuum delivery graph). (3) The emission of a warning signal when the 15-min time limit of continuous cup application on the fetal scalp, is reached. No cup detachment occurred in any of the 15 vacuum-assisted deliveries, in which traction was kept below the adhesive force of the cup [44 lb (20 kg)], except in three cases, due to loss of negative pressure. In the remaining 15 tests, in which traction was greater than the adhesive force of the cup, "pull-offs" inevitably occurred. Furthermore, upon reaching the 15-min time limit of continuous cup application on the fetal cephalic model, a warning signal was emitted, as programmed. Conclusions We demonstrated that the electronically-controlled VE, with its distinctive pull-sensing handle, performs suitably for its intended purposes. The ability of the modernized device to decrease the incidence of cup detachment, secondary to the inadvertent application of excessive traction, may result in considerable safety, medico-legal and didactic advantages.

Factors affecting plant growth in membrane nutrient delivery

NASA Technical Reports Server (NTRS)

Dreschel, T. W.; Wheeler, R. M.; Sager, J. C.; Knott, W. M.

1990-01-01

The development of the tubular membrane plant growth unit for the delivery of water and nutrients to roots in microgravity has recently focused on measuring the effects of changes in physical variables controlling solution availability to the plants. Significant effects of membrane pore size and the negative pressure used to contain the solution were demonstrated. Generally, wheat grew better in units with a larger pore size but equal negative pressure and in units with the same pore size but less negative pressure. Lettuce also exhibited better plant growth at less negative pressure.

Contrastive Analysis and Research on Negative Pressure Beam Tube System and Positive Pressure Beam Tube System for Mine Use

NASA Astrophysics Data System (ADS)

Wang, Xinyi; Shen, Jialong; Liu, Xinbo

2018-01-01

Against the technical defects of universally applicable beam tube monitoring system at present, such as air suction in the beam tube, line clogging, long sampling time, etc., the paper analyzes the current situation of the spontaneous combustion fire disaster forecast of mine in our country and these defects one by one. On this basis, the paper proposes a research thought that improving the positive pressure beam tube so as to substitute the negative pressure beam tube. Then, the paper introduces the beam tube monitoring system based on positive pressure technology through theoretical analysis and experiment. In the comparison with negative pressure beam tube, the paper concludes the advantage of the new system and draws the conclusion that the positive pressure beam tube is superior to the negative pressure beam tube system both in test result and test time. At last, the paper proposes prospect of the beam tube monitoring system based on positive pressure technology.

Human induced coastal changes and their impact on the coastal urban landscape. The case of Heraklion, Crete

NASA Astrophysics Data System (ADS)

Rempis, Nikolaos; Alexandrakis, George; Kampanis, Nikolaos

2017-04-01

Coastal zone is a vital part of human society due to sea activities. Α variety of activities and uses are present and are further developing in the coastal and marine are. Coastal ecosystems and landscape are under severe pressure due to population growth and continuous expansion of human activities and supplemented from the effects of climate change (e.g. coastal flooding, erosion). Heraklion is the largest urban center in Crete. Its suburban and coastal area receives intensive urban sprawl pressures, changing the urban landscape and resulting negative impacts on the human and natural environment. The saturation of coastal area of Heraklion creates the need for new development interventions (e.g. new marina, coastal protection, urban regeneration). This study examine the impacts of the new programmed coastal development intervention in the coastal landscape of Heraklion. A decision analytic approach was implemented, based on the need of stakeholders for the protection and further development of coastal area of Heraklion. In this direction, local authorities have proposed the realization of several development interventions which include a new marina, expansion of bathing beaches and coastal regeneration project in a large beach. The results indicate that the realization of any coastal development projects, also increases the negative effects that are related to land-sea interaction. The negative effects are a result of the interaction between different human activities but also between human activities and the environment. The development of the marina in the selected location, increases the pressure on the sea area as the navigation will increase, but also increases the pressure on land space, as traffic flows will change, creating new pressures in urban areas. The extension of bathing beaches implies larger number of bathers, thus creating greater needs for infrastructures in land area for their service. Coastal protection projects, as planned, will upgrade the inland section of the city coastal walls and upgrade them as tourist attraction.

Type of mask may impact on continuous positive airway pressure adherence in apneic patients.

PubMed

Borel, Jean Christian; Tamisier, Renaud; Dias-Domingos, Sonia; Sapene, Marc; Martin, Francis; Stach, Bruno; Grillet, Yves; Muir, Jean François; Levy, Patrick; Series, Frederic; Pepin, Jean-Louis

2013-01-01

In obstructive sleep apnea patients (OSA), continuous positive airway pressure (CPAP) adherence is crucial to improve symptoms and cardiometabolic outcomes. The choice of mask may influence CPAP adherence but this issue has never been addressed properly. To evaluate the impact of nasal pillows, nasal and oronasal masks on CPAP adherence in a cohort of OSA. Newly CPAP treated OSA participating in "Observatoire Sommeil de la Fédération de Pneumologie", a French national prospective cohort, were included between March 2009 and December 2011. Anthropometric data, medical history, OSA severity, sleepiness, depressive status, treatment modalities (auto-CPAP versus fixed pressure, pressure level, interface type, use of humidifiers) and CPAP-related side effects were included in multivariate analysis to determine independent variables associated with CPAP adherence. 2311 OSA (age = 57(12) years, apnea+hypopnea index = 41(21)/h, 29% female) were included. Nasal masks, oronasal masks and nasal pillows were used by 62.4, 26.2 and 11.4% of the patients, respectively. In univariate analysis, oronasal masks and nasal pillows were associated with higher risk of CPAP non-adherence. CPAP non-adherence was also associated with younger age, female gender, mild OSA, gastroesophageal reflux, depression status, low effective pressure and CPAP-related side effects. In multivariate analysis, CPAP non-adherence was associated with the use of oronasal masks (OR = 2.0; 95%CI = 1.6; 2.5), depression, low effective pressure, and side effects. As oronasal masks negatively impact on CPAP adherence, a nasal mask should be preferred as the first option. Patients on oronasal masks should be carefully followed.

A novel vacuum assisted closure therapy model for use with percutaneous devices.

PubMed

Cook, Saranne J; Nichols, Francesca R; Brunker, Lucille B; Bachus, Kent N

2014-06-01

Long-term maintenance of a dermal barrier around a percutaneous prosthetic device remains a common clinical problem. A technique known as Negative Pressure Wound Therapy (NPWT) uses negative pressure to facilitate healing of impaired and complex soft tissue wounds. However, the combination of using negative pressure with percutaneous prosthetic devices has not been investigated. The goal of this study was to develop a methodology to apply negative pressure to the tissues surrounding a percutaneous device in an animal model; no tissue healing outcomes are presented. Specifically, four hairless rats received percutaneous porous coated titanium devices implanted on the dorsum and were bandaged with a semi occlusive film dressing. Two of these animals received NPWT; two animals received no NPWT and served as baseline controls. Over a 28-day period, both the number of dressing changes required between the two groups as well as the pressures were monitored. Negative pressures were successfully applied to the periprosthetic tissues in a clinically relevant range with a manageable number of dressing changes. This study provides a method for establishing, maintaining, and quantifying controlled negative pressures to the tissues surrounding percutaneous devices using a small animal model. Published by Elsevier Ltd.

21 CFR 878.4683 - Non-Powered suction apparatus device intended for negative pressure wound therapy.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Non-Powered suction apparatus device intended for... Surgical Devices § 878.4683 Non-Powered suction apparatus device intended for negative pressure wound therapy. (a) Identification. A non-powered suction apparatus device intended for negative pressure wound...

Enhanced extraction of astragalosides from Radix Astragali by negative pressure cavitation-accelerated enzyme pretreatment.

PubMed

Yan, Ming-Ming; Chen, Cai-Yun; Zhao, Bao-Shan; Zu, Yuan-Gang; Fu, Yu-Jie; Liu, Wei; Efferth, Thomas

2010-10-01

The optimal conditions for extraction of astragalosides III and IV (AGs III and IV) in Radix Astragali by negative pressure cavitation-accelerated enzyme pretreatment were studied on the basis of a Box-Behnken design and response surface methodology. Experimental results showed that negative pressure, amount of enzyme and incubation temperature were the main factors governing the enzyme pretreatment of Radix Astragali. The optimum parameters were obtained as follows: negative pressure -0.08 Mpa, amount of enzyme 1.48% (w/w of materials) and incubation temperature 45 degrees C. Under the optimal conditions, the maximal extraction yields of AGs III and IV were 0.103 and 0.325 mg/g, which were 41.67% and 65.31% increased as compared to those without enzyme pretreatment, respectively. The effect of negative pressure cavitation and enzyme pretreatment on the structural changes of plant cells was observed by scanning electron microscopy. In conclusion, negative pressure cavitation-accelerated enzyme pretreatment was proved to be environment-friendly and economical, and could be used in secondary metabolites production. Copyright 2010 Elsevier Ltd. All rights reserved.

Baroreflex Responses to Acute Changes in Blood Volume in Humans

NASA Technical Reports Server (NTRS)

Thompson, Cynthia A.; Tatro, Dana L.; Ludwig, David A.; Convertino, Victor A.

1990-01-01

To test the hypothesis that acute changes in plasma volume affect the stimulus-response relations of high- and low- pressure baroreflexes, eight men (27-44 yr old) underwent measurements for carotid-cardiac and cardiopulmonary baro-reflex responses under the following three volemic conditions: hypovolemic, normovolemic, and hypervolemic. The stimulus- response relation of the carotid-cardiac response curve was generated using a neck cuff device, which delivered pressure changes between +40 and -65 mmHg in continuous steps of 15 mmHg. The stimulus-response relationship, of the cardio-pulmonary baroreflex were studied by measurements of Forearm Vascular Resistance (FVR) and Peripheral Venous Pressure (PVP) during low levels of lower body negative pressure (O to -20 mmHg). The results indicate greater demand for vasoconstriction for equal reductions in venous pressure during progressive hypovolemia; this condition may compromise the capacity to provide adequate peripheral resistance during severe orthostatic stress. Fluid loading before reentry after spaceflight may act to restore vasoconstrictive capacity of the cardiopulmonary baroreflex but may not be an effective countermeasure against potential post- flight impairment of the carotid-cardiac baroreflex.

Analysis on Experimental Investigation and Mathematical Modeling of Incompressible Flow Through Ceramic Foam Filters

NASA Astrophysics Data System (ADS)

Akbarnejad, Shahin; Jonsson, Lage Tord Ingemar; Kennedy, Mark William; Aune, Ragnhild Elizabeth; Jönsson, Pӓr Göran

2016-08-01

This paper presents experimental results of pressure drop measurements on 30, 50, and 80 pores per inch (PPI) commercial alumina ceramic foam filters (CFF) and compares the obtained pressure drop profiles to numerically modeled values. In addition, it is aimed at investigating the adequacy of the mathematical correlations used in the analytical and the computational fluid dynamics (CFD) simulations. It is shown that the widely used correlations for predicting pressure drop in porous media continuously under-predict the experimentally obtained pressure drop profiles. For analytical predictions, the negative deviations from the experimentally obtained pressure drop using the unmodified Ergun and Dietrich equations could be as high as 95 and 74 pct, respectively. For the CFD predictions, the deviation to experimental results is in the range of 84.3 to 88.5 pct depending on filter PPI. Better results can be achieved by applying the Forchheimer second-order drag term instead of the Brinkman-Forchheimer drag term. Thus, the final deviation of the CFD model estimates lie in the range of 0.3 to 5.5 pct compared to the measured values.

Contextual influences on safer sex negotiation among female sex workers (FSWs) in Hong Kong: the role of non-governmental organizations (NGOs), FSWs' managers, and clients.

PubMed

Cheng, Shannon S Y; Mak, Winnie W S

2010-05-01

Despite social-cognitive interventions to increase safer sex awareness, condom use among female sex workers (FSWs) continued to be inconsistent. To account for the possible influences of contextual factors that may hinder or promote FSWs' safer sex negotiation and condom use, the present study examined the effects of non-governmental organizations (NGOs), FSWs' managers, and clients on FSWs' negotiation efficacy and condom-use efficacy, and the effects of efficacy on condom use. One hundred and nineteen FSWs in Hong Kong completed a questionnaire that focused on their perceived influences of NGOs, managers, and clients toward safer sex negotiation and condom use. Hierarchical regression results showed that whereas NGOs' influence and clients' support were positively related to negotiation self-efficacy, managers' pressure, and clients' pressure were negatively related to negotiation self-efficacy. Managers' pressure was negatively related to condom-use self-efficacy. Logistic regression results showed that FSWs with high condom-use self-efficacy was 24 times more likely to use condom in the previous six months than their counterparts. The present study indicated the importance of social contexts in affecting FSWs' safer sex negotiation and condom-use self-efficacy. Implications on preventive programs for FSWs, managers, and clients were discussed.

Negative pressure wound therapy combined with acoustic pressure wound therapy for infected post surgery wounds: a case series.

PubMed

Howell-Taylor, Melania; Hall, Macy G; Brownlee Iii, William J; Taylor, Mary

2008-09-01

Acute infection of surgical incision sites often requires specialized wound care in preparation for surgical closure. Optimal therapy for preparing such wounds for a secondary closure procedure remains uncertain. The authors report wound outcomes after administering acoustic pressure wound therapy in conjunction with negative pressure wound therapy with reticulated open-cell foam dressing changes to assist with bacteria removal from open, infected surgical-incision sites in preparation for secondary surgical closure in three patients. Before incorporating acoustic pressure wound therapy at the authors' facility, the average negative pressure wound therapy with reticulated open-cell foam dressing course prior to secondary surgical closure was 30 days; with its addition, two of three patients underwent successful surgical closure with no postoperative complications after 21 and 14 days, respectively; one patient succumbed to nonwound-related complications before wound closure. Larger, prospective studies are needed to evaluate combining negative pressure wound therapy with reticulated open-cell foam dressing and acoustic pressure wound therapy for infected, acute post surgery wounds.

Use of Negative-Pressure Wound Therapy in Orthopaedic Trauma

DTIC Science & Technology

2012-09-01

sponge, and continuous suction is applied at −50 mm Hg. NPWT is discontinued after 2 to 5 days. Split-thickness Skin Graft When placing a NPWT dressing...over a split-thickness skin graft (STSG), we apply a single sheet of nonadher- ent dressing to the wound to provide a barrier between the STSG and the...trauma, including surgical incisions at increased risk of breakdown or in- fection, skin grafts , and infected wounds.21,22 Wounds With Associated Soft

A novel APPI-MS setup for in situ degradation product studies of atmospherically relevant compounds: capillary atmospheric pressure photo ionization (cAPPI).

PubMed

Kersten, Hendrik; Derpmann, Valerie; Barnes, Ian; Brockmann, Klaus J; O'Brien, Rob; Benter, Thorsten

2011-11-01

We report on the development of a novel atmospheric pressure photoionization setup and its applicability for in situ degradation product studies of atmospherically relevant compounds. A custom miniature spark discharge lamp was embedded into an ion transfer capillary, which separates the atmospheric pressure from the low pressure region in the first differential pumping stage of a conventional atmospheric pressure ionization mass spectrometer. The lamp operates with a continuous argon flow and produces intense light emissions in the VUV. The custom lamp is operated windowless and efficiently illuminates the sample flow through the transfer capillary on an area smaller than 1 mm(2). Limits of detection in the lower ppbV range, a temporal resolution of milliseconds in the positive as well as the quasi simultaneously operating negative ion mode, and a significant reduction of ion transformation processes render this system applicable to real time studies of rapidly changing chemical systems. The method termed capillary atmospheric pressure photo ionization (cAPPI) is characterized with respect to the lamp emission properties as a function of the operating conditions, temporal response, and its applicability for in situ degradation product studies of atmospherically relevant compounds, respectively.

Abdominal drainage following cholecystectomy: high, low, or no suction?

PubMed Central

McCormack, T. T.; Abel, P. D.; Collins, C. D.

1983-01-01

A prospective trial to assess the effect of suction in an abdominal drain following cholecystectomy was carried out. Three types of closed drainage system were compared: a simple tube drain, a low negative pressure drain, and a high negative pressure drain: 120 consecutive patients undergoing cholecystectomy were randomly allocated to one of the three drainage groups. There was no significant difference in postoperative pyrexia, wound infection, chest infection, or hospital stay. This study failed to demonstrate any clinically useful difference between high negative pressure, low negative pressure, and static drainage system were compared: a simple tube drain, a low negative used, suction is not necessary and a simple tube drain (greater than 6 mm internal diameter) is the most effective form of drainage. PMID:6614773

Effects of negative pressures on epithelial tight junctions and migration in wound healing.

PubMed

Hsu, Chih-Chin; Tsai, Wen-Chung; Chen, Carl Pai-Chu; Lu, Yun-Mei; Wang, Jong-Shyan

2010-08-01

Negative-pressure wound therapy has recently gained popularity in chronic wound care. This study attempted to explore effects of different negative pressures on epithelial migration in the wound-healing process. The electric cell-substrate impedance sensing (ECIS) technique was used to create a 5 x 10(-4) cm(2) wound in the Madin-Darby canine kidney (MDCK) and human keratinocyte (HaCaT) cells. The wounded cells were cultured in a negative pressure incubator at ambient pressure (AP) and negative pressures of 75 mmHg (NP(75)), 125 mmHg (NP(125)), and 175 mmHg (NP(175)). The effective time (ET), complete wound healing time (T(max)), healing rate (R(heal)), cell diameter, and wound area over time at different pressures were evaluated. Traditional wound-healing assays were prepared for fluorescent staining of cells viability, cell junction proteins, including ZO-1 and E-cadherin, and actins. Amount of cell junction proteins at AP and NP(125) was also quantified. In MDCK cells, the ET (1.25 +/- 0.27 h), T(max) (1.76 +/- 0.32 h), and R(heal) (2.94 +/- 0.62 x 10(-4) cm(2)/h) at NP(125) were significantly (P < 0.01) different from those at three other pressure conditions. In HaCaT cells, the T(max) (7.34 +/- 0.29 h) and R(heal) (6.82 +/- 0.26 x 10(-5) cm(2)/h) at NP(125) were significantly (P < 0.01) different from those at NP(75). Prominent cell migration features were identified in cells at the specific negative pressure. Cell migration activities at different pressures can be documented with the real-time wound-healing measurement system. Negative pressure of 125 mmHg can help disassemble the cell junction to enhance epithelial migration and subsequently result in quick wound closure.

Measuring high pressure baroreceptor sensitivity in the rat.

PubMed

Shiry, L J; Hamlin, R L

2011-01-01

The high pressure baroreceptor reflex rapidly buffers changes in systemic arterial pressure in response to postural changes, altered gravitational conditions, diseases, and pharmacological agents. Drug-induced exaggeration of changes in heart rate and in systemic arterial pressure is a leading cause of adverse events and of patients terminating use of drugs, particularly in the aging population. This paper presents a facile method for monitoring the high pressure baroreceptor reflex in rats, and presents an alternative to quantifying the magnitude of this reflex using 2 dependent variables, heart rate and systemic arterial pressure, rather than merely change in heart rate. Twenty-four rats were allocated to 3 groups: group I anesthetized with 100mg/kg thiopental, group II anesthetized with 2% isoflurane given by inhalation, group III anesthetized with thiopental but pretreated for 2weeks with 2μg/kg aldosterone given SQ bid. After induction to anesthesia, hair was clipped from the ventral aspect of the neck, and petrolatum was applied to the skin to permit an air-tight seal with a glass funnel attached to a source of variable and controllable negative pressure. Systemic arterial pressure, ECG, heart rate, and a force of suction applied to the neck were all recorded continuously. After baseline recordings, a force of -20mmHg was applied for 20s over the carotid artery. In rats receiving thiopental, the average changes in heart rate and systemic arterial pressure following the application of -20mmHg neck suction were 30±11bpm and 45±14mmHg, respectively. The ratios of change in heart and change in systemic arterial pressure to application of negative force over the carotid sinus are 1.5±0.6bpm/mmHg and 0.7±04mmHg/mmHg, respectively. Mean values for heart rate and for mean systemic arterial pressure during baseline and after application of neck suction for 20s showed little to no decrease (i.e., blunting) in rats anesthetized with isoflurane or pretreated with aldosterone. Thus this methodology was able to detect, in rats, blunting of baroreceptor function for at least 2 perturbations of this important homeostatic control system. Copyright © 2011. Published by Elsevier Inc.

Ni-MH storage test and cycle life test

NASA Technical Reports Server (NTRS)

Dell, R. Dan; Klein, Glenn C.; Schmidt, David F.

1994-01-01

Gates Aerospace Batteries is conducting two long term test programs to fully characterize the NiMH cell technology for aerospace applications. The first program analyzes the effects of long term storage upon cell performance. The second program analyzes cycle life testing and preliminary production lot testing. This paper summarizes these approaches to testing the NiMH couple and culminates with initial storage and testing recommendations. Long term storage presents challenges to deter the adverse condition of capacity fade in NiMH cells. Elevated but stabilized pressures and elevated but stabilized end-of-charge voltages also appear to be a characteristic phenomenon of long term storage modes. However, the performance degradation is dependent upon specific characteristics of the metal-hydride alloy. To date, there is no objective evidence with which to recommend the proper method for storage and handling of NiMH cells upon shipment. This is particularly critical due to limited data points that indicate open circuit storage at room temperature for 60 to 90 days will result in irrecoverable capacity loss. Accordingly a test plan was developed to determine what method of mid-term to long-term storage will prevent irrecoverable capacity loss. The explicit assumption is that trickle charging at some rate above the self-discharge rate will prevent the irreversible chemical changes to the negative electrode that result in the irrecoverable capacity loss. Another premise is that lower storage temperatures, typically 0 C for aerospace customers, will impede any negative chemical reactions. Three different trickle charge rates are expected to yield a fairly flat response with respect to recoverable capacity versus baseline cells in two different modes of open circuit. Specific attributes monitored include: end-of-charge voltage, end-of-charge pressure, mid-point discharge voltage, capacity, and end-of-discharge pressure. Cycle life testing and preliminary production lot testing continue to dominate the overall technology development effort at GAB. The cell life test program reflects continuing improvements in baseline cell designs. Performance improvements include lower and more stable charge voltages and pressures. The continuing review of production lot testing assures conformance to the design criteria and expectations. This is especially critical during this period of transferring technology from research and development status to production.

Lower Body Negative Pressure: Historical Perspective, Research Findings, and Clinical Applications.

PubMed

Crystal, George J; Salem, M Ramez

2015-04-01

Lower body negative pressure (LBNP) is a technique that redistributes blood from the upper body to the dependent regions of the pelvis and legs, thus reducing central venous pressure and venous return. The subject is placed in a cylindrical air-tight metal tank, which is sealed at the level of the iliac crests, and subatmospheric pressure is produced using a vacuum pump. This article reviews the historical background, physiological effects, research findings, and clinical applications of LBNP. LBNP is found in both the basic science and clinical literature, encompassing its diverse investigational and clinical applications. The first references to LBNP were in 1952 describing its effectiveness in inducing hypotensive anesthesia. Major interest in LBNP began in the mid 1960s when it was used to characterize the cardiovascular responses to hemorrhage and orthostatic stress, especially that associated with the weightlessness of space flight; these studies have continued to the present day. Advantages of LBNP for such experimental studies include the following: (1) The degree of central hypovolemia is easily controlled and has a rapid onset and reversal. (2) The technique is repeatable, reproducible, and noninvasive. (3) No exogenous pharmacologic agent is required to produce venous pooling. (4) The findings are independent of gravity. In recent years, a few institutions have applied LBNP clinically to diagnose abnormalities in cardiovascular autonomic function and, when combined with echocardiography, to uncover changes in cardiac performance through analysis of Starling curves. Copyright © 2015 Anesthesia History Association. Published by Elsevier Inc. All rights reserved.

Who Chokes Under Pressure? The Big Five Personality Traits and Decision-Making under Pressure.

PubMed

Byrne, Kaileigh A; Silasi-Mansat, Crina D; Worthy, Darrell A

2015-02-01

The purpose of the present study was to examine whether the Big Five personality factors could predict who thrives or chokes under pressure during decision-making. The effects of the Big Five personality factors on decision-making ability and performance under social (Experiment 1) and combined social and time pressure (Experiment 2) were examined using the Big Five Personality Inventory and a dynamic decision-making task that required participants to learn an optimal strategy. In Experiment 1, a hierarchical multiple regression analysis showed an interaction between neuroticism and pressure condition. Neuroticism negatively predicted performance under social pressure, but did not affect decision-making under low pressure. Additionally, the negative effect of neuroticism under pressure was replicated using a combined social and time pressure manipulation in Experiment 2. These results support distraction theory whereby pressure taxes highly neurotic individuals' cognitive resources, leading to sub-optimal performance. Agreeableness also negatively predicted performance in both experiments.

Resting Sympathetic Baroreflex Sensitivity in Subjects with Low and High Tolerance to Central Hypovolemia Induced by Lower Body Negative Pressure

DTIC Science & Technology

2014-06-01

high tolerance to central hypovolemia induced by lower body negative pressure Carmen Hinojosa-Laborde1*, Kathy L. Ryan1, Caroline A. Rickards2 and...patients with high tolerance. Using lower body negative pressure (LBNP) as an experimental model to induce central hypovolemia, we have shown that...hypovolemia is associated with mainte- nance of adequate perfusion pressure (i.e., arterial blood pres- sure) to vital organs. Therefore, we hypothesize that

Water quality effects of intermittent water supply in Arraiján, Panama.

PubMed

Erickson, John J; Smith, Charlotte D; Goodridge, Amador; Nelson, Kara L

2017-05-01

Intermittent drinking water supply is common in low- and middle-income countries throughout the world and can cause water quality to degrade in the distribution system. In this study, we characterized water quality in one study zone with continuous supply and three zones with intermittent supply in the drinking water distribution network in Arraiján, Panama. Low or zero pressures occurred in all zones, and negative pressures occurred in the continuous zone and two of the intermittent zones. Despite hydraulic conditions that created risks for backflow and contaminant intrusion, only four of 423 (0.9%) grab samples collected at random times were positive for total coliform bacteria and only one was positive for E. coli. Only nine of 496 (1.8%) samples had turbidity >1.0 NTU and all samples had ≥0.2 mg/L free chlorine residual. In contrast, water quality was often degraded during the first-flush period (when supply first returned after an outage). Still, routine and first-flush water quality under intermittent supply was much better in Arraiján than that reported in a previous study conducted in India. Better water quality in Arraiján could be due to better water quality leaving the treatment plant, shorter supply outages, higher supply pressures, a more consistent and higher chlorine residual, and fewer contaminant sources near pipes. The results illustrate that intermittent supply and its effects on water quality can vary greatly between and within distribution networks. The study also demonstrated that monitoring techniques designed specifically for intermittent supply, such as continuous pressure monitoring and sampling the first flush, can detect water quality threats and degradation that would not likely be detected with conventional monitoring. Copyright © 2017 Elsevier Ltd. All rights reserved.

Pressure Ulcers in the United States' Inpatient Population From 2008 to 2012: Results of a Retrospective Nationwide Study.

PubMed

Bauer, Karen; Rock, Kathryn; Nazzal, Munier; Jones, Olivia; Qu, Weikai

2016-11-01

Pressure ulcers are common, increase patient morbidity and mortality, and costly for patients, their families, and the health care system. A retrospective study was conducted to evaluate the impact of pressure ulcers on short-term outcomes in United States inpatient populations and to identify patient characteristics associated with having 1 or more pressure ulcers. The US Nationwide Inpatient Sample (NIS) database was analyzed using the International Classification of Disease, 9th Revision, Clinical Modification (ICD-9 CM) diagnosis codes as the screening tool for all inpatient pressure ulcers recorded from 2008 to 2012. Patient demographics and comorbid conditions, as identified by ICD-9 code, were extracted, along with primary outcomes of length of stay (LOS), total hospital charge (TC), inhospital mortality, and discharge disposition. Continuous variables with normal distribution were expressed in terms of mean and standard deviation. Group comparisons were performed using t-test or ANOVA test. Continuous nonnormal distributed variables such as LOS and TC were expressed in terms of median, and nonparametric tests were used to compare the differences between groups. Categorical data were presented in terms of percentages of the number of cases within each group. Chi-squared tests were used to compare categorical data in different groups. For multivariate analysis, linear regressions (for continuous variable) and logistic regression (for categorical variables) were used to analyze the possible risk factors for the investigated outcomes of LOS, TC, inhospital mortality, and patient disposition. Coefficients were calculated with multivariate regression with all included patients versus patients with pressure ulcers alone. The 5-year average number of admitted patients with at least 1 pressure ulcer was determined to be 670 767 (average overall rate: 1.8%). Statistically significant differences between patients with and without pressure ulcers were observed for median LOS (7 days [mean 11.1 ± 15] compared to 3 days [mean 4.6 ± 6.8]) and median TC ($36 500 [mean $72 000 ± $122 900] compared to $17 200 [mean $32 200 ± $57 500]). The mortality rate in patients with a pressure ulcer was significantly higher than in patients without a pressure ulcer (9.1% versus 1.8%, OR = 5.08, CI: 5.03-5.1, P <0.001). Pressure ulcers were significantly more common in patients who were older or had malnutrition. The results of this study confirm the importance of prevention initiatives to help reduce the negative impact of pressure ulcers on patient outcomes and costs of care.

Adverse effects of social pressure to be thin on young women: an experimental investigation of the effects of "fat talk".

PubMed

Stice, Eric; Maxfield, Jennifer; Wells, Tony

2003-07-01

Experiments have found that pressure to be thin from the media promotes body dissatisfaction and negative affect, but the effects of social pressure to be thin have not been examined experimentally. Thus, this study tested whether social pressure to be thin fosters body dissatisfaction and negative affect. Young women (N = 120) were randomly assigned to a condition wherein an ultra-thin confederate complained about how fat she felt and voiced intentions to lose weight or a control condition wherein she discussed a neutral topic. Exposure to social pressure to be thin resulted in increased body dissatisfaction but not negative affect. The effects were not moderated by initial thin-ideal internalization, body dissatisfaction, or social support. Results support the assertion that peer pressure to be thin promotes body dissatisfaction but suggest that this factor may not contribute to negative affect. Copyright 2003 by Wiley Periodicals, Inc.

Cavitation clouds created by shock scattering from bubbles during histotripsy

PubMed Central

Maxwell, Adam D.; Wang, Tzu-Yin; Cain, Charles A.; Fowlkes, J. Brian; Sapozhnikov, Oleg A.; Bailey, Michael R.; Xu, Zhen

2011-01-01

Histotripsy is a therapy that focuses short-duration, high-amplitude pulses of ultrasound to incite a localized cavitation cloud that mechanically breaks down tissue. To investigate the mechanism of cloud formation, high-speed photography was used to observe clouds generated during single histotripsy pulses. Pulses of 5−20 cycles duration were applied to a transparent tissue phantom by a 1-MHz spherically focused transducer. Clouds initiated from single cavitation bubbles that formed during the initial cycles of the pulse, and grew along the acoustic axis opposite the propagation direction. Based on these observations, we hypothesized that clouds form as a result of large negative pressure generated by the backscattering of shockwaves from a single bubble. The positive-pressure phase of the wave inverts upon scattering and superimposes on the incident negative-pressure phase to create this negative pressure and cavitation. The process repeats with each cycle of the incident wave, and the bubble cloud elongates toward the transducer. Finite-amplitude propagation distorts the incident wave such that the peak-positive pressure is much greater than the peak-negative pressure, which exaggerates the effect. The hypothesis was tested with two modified incident waves that maintained negative pressure but reduced the positive pressure amplitude. These waves suppressed cloud formation which supported the hypothesis. PMID:21973343

[Curative effects of platelet-rich plasma combined with negative-pressure wound therapy on sternal osteomyelitis and sinus tract after thoracotomy].

PubMed

Hao, Daifeng; Feng, Guang; Li, Tao; Chu, Wanli; Chen, Zequn; Li, Shanyou; Zhang, Xinjian; Zhao, Jingfeng; Zhao, Fan

2016-06-01

To observe the curative effects of platelet-rich plasma (PRP) combined with negative-pressure wound therapy (NPWT) on patients with sternal osteomyelitis and sinus tract after thoracotomy. Sixty-two patients with sternal osteomyelitis and sinus tract after thoracotomy, hospitalized from March 2011 to June 2015, were retrospectively analyzed. Based on whether receiving PRP or not, patients were divided into two groups, group NPWT ( 22 patients hospitalized from March 2011 to December 2012) and combination treatment group (CT, 40 patients hospitalized from January 2013 to June 2015). After debridement, patients in group NPWT were treated with continuous NPWT (negative pressure values from -15.96 to -13.30 kPa), while those in group CT were treated with PRP gel (blood platelet counts in PRP ranged from 1 450×10(9)/L to 1 800×10(9)/L, with 10-15 mL in each dosage) made on the surgery day to fill the sinus tract and wound, followed by NPWT. Negative pressure materials were changed every 5 days until 20 days after surgery in patients of both groups. PRP gel was replenished before changing of negative pressure materials in patients of group CT. The sinus tract sealing time, wound healing time, number of patients who had secondary repair surgery, number of patients who had recurrence of sinus tract within three months after wound healing, and length of hospital stay were recorded. Data were processed with t test, Fisher's exact test, and chi-square test. The sinus tract sealing time, wound healing time, and length of hospital stay in patients of group CT were (16±8), (27±13), and (43±13) d respectively, which were all significantly shorter than those in group NPWT [(29±14), (41±17), and (60±20) d, with t values from 3.88 to 4.67, P values below 0.01]. The number of patients who had secondary repair surgery in group CT was less than that in group NPWT (P<0.01). There was no statistically significant difference in the number of patients who had recurrence of sinus tract between two groups (P>0.05). Compared with NPWT only, PRP combined with NPWT has great curative effects on patients with sternal osteomyelitis and sinus tract after thoracotomy, for it shortens sinus tract sealing time, wound healing time, and length of hospital stay, and avoids the secondary repair surgery. This method is simple and safe with little injury.

Understanding motivation for substance use treatment: the role of social pressure during the transition to adulthood.

PubMed

Goodman, Ilana; Peterson-Badali, Michele; Henderson, Joanna

2011-06-01

Research has shown that social pressure is related to treatment motivation and plays an important role in treatment engagement in adults with problematic substance use. Despite the shifts in autonomy and decision-making in emerging adulthood, the factors affecting treatment motivation (e.g., readiness to comply with treatment) during this period have been largely ignored. In this cross sectional study, 134 youth (83 males and 51 females) presenting to an outpatient substance abuse program completed questionnaires regarding substance use history, mental health, social pressure to reduce use and enter treatment, and treatment motivation. Age was positively related to identification of internal reasons for seeking treatment and negatively related to external coercive social pressures as a motivator for treatment. Peer pressure accounted for significant variance in Identified (e.g., personal choice and commitment to the program) and Introjected (e.g., guilt about continued substance use) treatment motivation. Family pressure was related only to External treatment motivation when peer pressure was considered in the regression model. These results highlight the importance of emerging adult peers as motivators of youths' treatment seeking. Limitations, directions for future research and treatment implications are discussed. Crown Copyright © 2011. Published by Elsevier Ltd. All rights reserved.

Type of Mask May Impact on Continuous Positive Airway Pressure Adherence in Apneic Patients

PubMed Central

Borel, Jean Christian; Tamisier, Renaud; Dias-Domingos, Sonia; Sapene, Marc; Martin, Francis; Stach, Bruno; Grillet, Yves; Muir, Jean François; Levy, Patrick; Series, Frederic; Pepin, Jean-Louis

2013-01-01

Rationale In obstructive sleep apnea patients (OSA), continuous positive airway pressure (CPAP) adherence is crucial to improve symptoms and cardiometabolic outcomes. The choice of mask may influence CPAP adherence but this issue has never been addressed properly. Objective To evaluate the impact of nasal pillows, nasal and oronasal masks on CPAP adherence in a cohort of OSA. Methods Newly CPAP treated OSA participating in “Observatoire Sommeil de la Fédération de Pneumologie”, a French national prospective cohort, were included between March 2009 and December 2011. Anthropometric data, medical history, OSA severity, sleepiness, depressive status, treatment modalities (auto-CPAP versus fixed pressure, pressure level, interface type, use of humidifiers) and CPAP-related side effects were included in multivariate analysis to determine independent variables associated with CPAP adherence. Results 2311 OSA (age = 57(12) years, apnea+hypopnea index = 41(21)/h, 29% female) were included. Nasal masks, oronasal masks and nasal pillows were used by 62.4, 26.2 and 11.4% of the patients, respectively. In univariate analysis, oronasal masks and nasal pillows were associated with higher risk of CPAP non-adherence. CPAP non-adherence was also associated with younger age, female gender, mild OSA, gastroesophageal reflux, depression status, low effective pressure and CPAP-related side effects. In multivariate analysis, CPAP non-adherence was associated with the use of oronasal masks (OR = 2.0; 95%CI = 1.6; 2.5), depression, low effective pressure, and side effects. Conclusion As oronasal masks negatively impact on CPAP adherence, a nasal mask should be preferred as the first option. Patients on oronasal masks should be carefully followed. PMID:23691209

Preventing Seal Leak During Negative Pressure Wound Therapy Near External Fixators: A Technical Tip.

PubMed

Mannino, Brian J; Pullen, Michael W; Gaines, Robert

2017-03-01

Negative pressure wound therapy is an effective tool for the treatment of open wounds. Occasionally these wounds are associated with injuries or procedures that require treatment with an external fixator. This article shows how a simple, inexpensive, and commercially available product can be used to prevent loss of suction around external fixator pins within the negative pressure wound treatment area.

Negative-pressure polymorphs made by heterostructural alloying

PubMed Central

Perkins, John D.

2018-01-01

The ability of a material to adopt multiple structures, known as polymorphism, is a fascinating natural phenomenon. Various polymorphs with unusual properties are routinely synthesized by compression under positive pressure. However, changing a material’s structure by applying tension under negative pressure is much more difficult. We show how negative-pressure polymorphs can be synthesized by mixing materials with different crystal structures—a general approach that should be applicable to many materials. Theoretical calculations suggest that it costs less energy to mix low-density structures than high-density structures, due to less competition for space between the atoms. Proof-of-concept experiments confirm that mixing two different high-density forms of MnSe and MnTe stabilizes a Mn(Se,Te) alloy with a low-density wurtzite structure. This Mn(Se,Te) negative-pressure polymorph has 2× to 4× lower electron effective mass compared to MnSe and MnTe parent compounds and has a piezoelectric response that none of the parent compounds have. This example shows how heterostructural alloying can lead to negative-pressure polymorphs with useful properties—materials that are otherwise nearly impossible to make. PMID:29725620

Negative-pressure polymorphs made by heterostructural alloying.

PubMed

Siol, Sebastian; Holder, Aaron; Steffes, James; Schelhas, Laura T; Stone, Kevin H; Garten, Lauren; Perkins, John D; Parilla, Philip A; Toney, Michael F; Huey, Bryan D; Tumas, William; Lany, Stephan; Zakutayev, Andriy

2018-04-01

The ability of a material to adopt multiple structures, known as polymorphism, is a fascinating natural phenomenon. Various polymorphs with unusual properties are routinely synthesized by compression under positive pressure. However, changing a material's structure by applying tension under negative pressure is much more difficult. We show how negative-pressure polymorphs can be synthesized by mixing materials with different crystal structures-a general approach that should be applicable to many materials. Theoretical calculations suggest that it costs less energy to mix low-density structures than high-density structures, due to less competition for space between the atoms. Proof-of-concept experiments confirm that mixing two different high-density forms of MnSe and MnTe stabilizes a Mn(Se,Te) alloy with a low-density wurtzite structure. This Mn(Se,Te) negative-pressure polymorph has 2× to 4× lower electron effective mass compared to MnSe and MnTe parent compounds and has a piezoelectric response that none of the parent compounds have. This example shows how heterostructural alloying can lead to negative-pressure polymorphs with useful properties-materials that are otherwise nearly impossible to make.

Effects of a continuous lateral turning device on pressure relief.

PubMed

Do, Nam Ho; Kim, Deog Young; Kim, Jung-Hoon; Choi, Jong Hyun; Joo, So Young; Kang, Na Kyung; Baek, Yoon Su

2016-01-01

[Purpose] The purpose of this study was to examine the pressure-relieving effects of a continuous lateral turning device on common pressure ulcer sites. [Subjects] Twenty-four healthy adults participated. [Methods] The design of our continuous lateral turning device was motivated by the need for an adequate pressure-relieving device for immobile and/or elderly people. The procedure of manual repositioning is embodied in our continuous lateral turning device. The interface pressure and time were measured, and comfort grade was evaluated during sessions of continuous lateral turning at 0°, 15°, 30°, and 45°. We quantified the pressure-relieving effect using peak pressure, mean pressure, and pressure time integration. [Results] Participants demonstrated pressure time integration values below the pressure-time threshold at 15°, 30°, and 45° at all the common pressure ulcer sites. Moreover, the most effective angles for pressure relief at the common pressure ulcer sites were 30° at the occiput, 15° at the left scapula, 45° at the right scapula, 45° at the sacrum, 15° at the right heel, and 30° at the left heel. However, angles greater than 30° induced discomfort. [Conclusion] Continuous lateral turning with our specially designed device effectively relieved the pressure of targeted sites. Moreover, the suggested angles of continuous lateral turning can be used to relieve pressure at targeted sites.

Residual Negative Pressure in Vacuum Tubes Might Increase the Risk of Spurious Hemolysis.

PubMed

Xiao, Tong-Tong; Zhang, Qiao-Xin; Hu, Jing; Ouyang, Hui-Zhen; Cai, Ying-Mu

2017-05-01

We planned a study to establish whether spurious hemolysis may occur when negative pressure remains in vacuum tubes. Four tubes with different vacuum levels (-54, -65, -74, and -86 kPa) were used to examine blood drawn from one healthy volunteer; the tubes were allowed to stand for different times (1, 2, 3, and 4 hours). The plasma was separated and immediately tested for free hemoglobin (FHb). Thirty patients were enrolled in a verification experiment. The degree of hemolysis observed was greater when the remaining negative pressure was higher. Significant differences were recorded in the verification experiment. The results suggest that residual negative pressure might increase the risk of spurious hemolysis.

Advances in wound healing: topical negative pressure therapy

PubMed Central

Jones, S; Banwell, P; Shakespeare, P

2005-01-01

In clinical practice many wounds are slow to heal and difficult to manage. The recently introduced technique of topical negative pressure therapy (TNP) has been developed to try to overcome some of these difficulties. TNP applies a controlled negative pressure to the surface of a wound that has potential advantages for wound treatment and management. Although the concept itself, of using suction in wound management is not new, the technique of applying a negative pressure at the surface of the wound is. This paper explores the origins and proposed mechanisms of action of TNP therapy and discusses the types of wounds that are thought to benefit most from use of this system. PMID:15937199

In-Flight Lower Body Negative Pressure - Skylab Experiment M092

NASA Technical Reports Server (NTRS)

1973-01-01

This chart details Skylab's In-Flight Lower Body Negative Pressure experiment facility, a medical evaluation designed to monitor changes in astronauts' cardiovascular systems during long-duration space missions. This experiment collected in-flight data for predicting the impairment of physical capacity and the degree of orthostatic intolerance to be expected upon return to Earth. Data to be collected were blood pressure, heart rate, body temperature, vectorcardiogram, lower body negative pressure, leg volume changes, and body mass. The Marshall Space Flight Center had program management responsibility for the development of Skylab hardware and experiments.

Origin of negative thermal expansion in Zn2GeO4 revealed by high pressure study

NASA Astrophysics Data System (ADS)

Cheng, Xuerui; Yuan, Jie; Zhu, Xiang; Yang, Kun; Liu, Miao; Qi, Zeming

2018-03-01

Zn2GeO4, as an open-framework structure compound, exhibits negative thermal expansion (NTE) below room temperature. In this work, we investigated the structural stability and phonon modes employing the x-ray diffraction and Raman spectroscopy under high pressure up to 23.0 GPa within a diamond anvil cell, and we observed that a pressure-induced irreversible amorphization took place around 10.1 GPa. Bulk modulus, pressure coefficients, and Grüneisen parameters were measured for the initial rhombohedral structure. Several low-frequency rigid-unit modes are found to have negative Grüneisen parameter, which accounts for the primary part of NTE in Zn2GeO4. These results further confirm the hypothesis that the pressure-induced amorphization and the negative thermal expansion are correlated phenomena.

Skin microvascular flow during hypobaric exposure with and without a mechanical counter-pressure space suit glove

NASA Technical Reports Server (NTRS)

Tanaka, Kunihiko; Waldie, James; Steinbach, Gregory C.; Webb, Paul; Tourbier, Dietmar; Knudsen, Jeffrey; Jarvis, Christine W.; Hargens, Alan R.

2002-01-01

INTRODUCTION: Current space suits are rigid, gas-pressurized shells that protect astronauts from the vacuum of space. A tight elastic garment or mechanical-counter-pressure (MCP) suit generates pressure by compression and may have several advantages over current space suit technology. In this study, we investigated local microcirculatory effects produced with and without a prototype MCP glove. METHODS: The right hand of eight normal volunteers was studied at normal ambient pressure and during exposure to -50, -100 and -150 mm Hg with and without the MCP glove. Measurements included the pressure against the hand, skin microvascular flow, temperature on the dorsum of the hand, and middle finger girth. RESULTS: Without the glove, skin microvascular flow and finger girth significantly increased with negative pressure, and the skin temperature decreased compared with the control condition. The MCP glove generated approximately 200 mm Hg at the skin surface; all measured values remained at control levels during exposure to negative pressure. DISCUSSION: Without the glove, skin microvascular flow and finger girth increased with negative pressure, probably due to a blood shift toward the hand. The elastic compression of the material of the MCP glove generated pressure on the hand similar to that in current gas-pressurized space suit gloves. The MCP glove prevented the apparent blood shift and thus maintained baseline values of the measured variables despite exposure of the hand to negative pressure.

Optofluidic lens with tunable focal length and asphericity

PubMed Central

Mishra, Kartikeya; Murade, Chandrashekhar; Carreel, Bruno; Roghair, Ivo; Oh, Jung Min; Manukyan, Gor; van den Ende, Dirk; Mugele, Frieder

2014-01-01

Adaptive micro-lenses enable the design of very compact optical systems with tunable imaging properties. Conventional adaptive micro-lenses suffer from substantial spherical aberration that compromises the optical performance of the system. Here, we introduce a novel concept of liquid micro-lenses with superior imaging performance that allows for simultaneous and independent tuning of both focal length and asphericity. This is achieved by varying both hydrostatic pressures and electric fields to control the shape of the refracting interface between an electrically conductive lens fluid and a non-conductive ambient fluid. Continuous variation from spherical interfaces at zero electric field to hyperbolic ones with variable ellipticity for finite fields gives access to lenses with positive, zero, and negative spherical aberration (while the focal length can be tuned via the hydrostatic pressure). PMID:25224851

Investigation of the relationship between neutrophil-to-lymphocyte ratio and obstructive sleep apnoea syndrome.

PubMed

Yenigun, A; Karamanli, H

2015-09-01

To investigate the neutrophil-to-lymphocyte ratio and sleep apnoea severity relationship. Patients (n = 178) were assigned to five groups according to apnoea-hypopnea indices and continuous positive airway pressure use. White blood cell, neutrophil, lymphocyte and neutrophil-to-lymphocyte ratio values were compared for each group. The neutrophil-to-lymphocyte ratio values of severe obstructive sleep apnoea syndrome patients (group 4) were significantly higher than those of: control patients (group 1), mild obstructive sleep apnoea syndrome patients (group 2) and patients treated with continuous positive airway pressure (group 5) (p = 0.008, p = 0.008 and p = 0.003). Minimum oxygen saturation values of group 4 were significantly lower than those of groups 1, 2 and 5 (p = 0.0005, p = 0.011 and p = 0.001). There was a positive correlation between apnoea-hypopnea index and neutrophil-to-lymphocyte ratio (r = 0.758, p = 0.034), and a negative correlation between apnoea-hypopnea index and minimum oxygen saturation (r = -0.179, p = 0.012). Neutrophil-to-lymphocyte ratio may be used to determine disease severity, complementing polysomnography.

Hypertonic Glucose Combined with Negative Pressure Wound Therapy to Prepare Wounds with Pseudomonas aeruginosa Infection for Skin Grafting: A Report of 3 Cases.

PubMed

Zhao, Jing-Chun; Xian, Chun-Jing; Yu, Jia-Ao; Shi, Kai; Hong, Lei

2015-06-01

Soft tissue losses from acute or chronic trauma are a challenge for surgeons. To explore a method to expedite granulation tissue formation in preparation for a split-thickness skin graft (STSG), the medical records of 3 patients - 2 adult men with wounds related to trauma injury and 1 infant with necrotizing fasciitis, all infected with Pseudomonas aeruginosa - were reviewed. All wounds were surgically debrided and managed by applying gauze soaked in 50% glucose followed by continuous negative pressure wound therapy (NPWT) before definitive skin grafting. NPWT pressure was applied at -80 mm Hg for the 2 adult males (ages 39 and 25 years) and -50 mm Hg for the 7-month-old male infant. The dressings were changed every 2 to 3 days. No adverse events occurred, and wounds were successfully closed with a STSG after an average of 7 days. In 1 case, NPWT was able to help affix dressings in a difficult-to-dress area (genital region). The combination of hypertonic glucose and hand-made, gauze-based NPWT was found to be safe, well-tolerated, and effective in preparing the wound bed for grafting. Prospective, randomized, controlled clinical studies are needed to compare the safety, effectiveness, and efficacy of this method to other treatment approaches for P. aeruginosa-infected wounds.

Metastable superheated ice in liquid-water inclusions under high negative pressure

USGS Publications Warehouse

Roedder, E.

1967-01-01

In some microscopic inclusions (consisting of aqueous liquid and vapor) in minerals, freezing eliminates the vapor phase because of greater volume occupied by the resulting ice. When vapor fails to nucleate again on partial melting, the resulting negative pressure (hydrostatic tension) inside the inclusions permits the existence of ice I crystals under reversible, metastable equilibrium, at temperatures as high as +6.5??C and negative pressures possibly exceeding 1000 bars.

Delayed extubation to nasal continuous positive airway pressure in the immature baboon model of bronchopulmonary dysplasia: lung clinical and pathological findings.

PubMed

Thomson, Merran A; Yoder, Bradley A; Winter, Vicki T; Giavedoni, Luis; Chang, Ling Yi; Coalson, Jacqueline J

2006-11-01

Using the 125-day baboon model of bronchopulmonary dysplasia treated with prenatal steroid and exogenous surfactant, we hypothesized that a delay of extubation from low tidal volume positive pressure ventilation to nasal continuous positive airway pressure at 5 days (delayed nasal continuous positive airway pressure group) would not induce more lung injury when compared with baboons aggressively weaned to nasal continuous positive airway pressure at 24 hours (early nasal continuous positive airway pressure group), because both received positive pressure ventilation. After delivery by cesarean section at 125 days (term: 185 days), infants received 2 doses of Curosurf (Chiesi Farmaceutica S.p.A., Parma, Italy) and daily caffeine citrate. The delay in extubation to 5 days resulted in baboons in the delayed nasal continuous positive airway pressure group having a lower arterial to alveolar oxygen ratio, high PaCO2, and worse respiratory function. The animals in the delayed nasal continuous positive airway pressure group exhibited a poor respiratory drive that contributed to more reintubations and time on mechanical ventilation. A few animals in both groups developed necrotizing enterocolitis and/or sepsis, but infectious pneumonias were not documented. Cellular bronchiolitis and peribronchiolar alveolar wall thickening were more frequently seen in the delayed nasal continuous positive airway pressure group. Bronchoalveolar lavage levels of interleukin-6, interleukin-8, monocyte chemotactic protein-1, macrophage inflammatory protein-1 alpha, and growth-regulated oncogene-alpha were significantly increased in the delayed nasal continuous positive airway pressure group. Standard and digital morphometric analyses showed no significant differences in internal surface area and nodal measurements between the groups. Platelet endothelial cell adhesion molecule vascular staining was not significantly different between the 2 nasal continuous positive airway pressure groups. Volutrauma and/or low-grade colonization of airways secondary to increased reintubations and ventilation times are speculated to play causative roles in the delayed nasal continuous positive airway pressure group findings.

Negative-pressure polymorphs made by heterostructural alloying

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

Siol, Sebastian; Holder, Aaron; Steffes, James

The ability of a material to adopt multiple structures, known as polymorphism, is a fascinating natural phenomenon. Various polymorphs with unusual properties are routinely synthesized by compression under positive pressure. However, changing a material's structure by applying tension under negative pressure is much more difficult. We show how negative-pressure polymorphs can be synthesized by mixing materials with different crystal structures - a general approach that should be applicable to many materials. Theoretical calculations suggest that it costs less energy to mix low-density structures than high-density structures, due to less competition for space between the atoms. Proof-of-concept experiments confirm that mixingmore » two different high-density forms of MnSe and MnTe stabilizes a Mn(Se,Te) alloy with a low-density wurtzite structure. This Mn(Se,Te) negative-pressure polymorph has 2x to 4x lower electron effective mass compared to MnSe and MnTe parent compounds and has a piezoelectric response that none of the parent compounds have. Lastly, this example shows how heterostructural alloying can lead to negative-pressure polymorphs with useful properties - materials that are otherwise nearly impossible to make.« less

Negative-pressure polymorphs made by heterostructural alloying

DOE PAGES

Siol, Sebastian; Holder, Aaron; Steffes, James; ...

2018-04-20

The ability of a material to adopt multiple structures, known as polymorphism, is a fascinating natural phenomenon. Various polymorphs with unusual properties are routinely synthesized by compression under positive pressure. However, changing a material's structure by applying tension under negative pressure is much more difficult. We show how negative-pressure polymorphs can be synthesized by mixing materials with different crystal structures - a general approach that should be applicable to many materials. Theoretical calculations suggest that it costs less energy to mix low-density structures than high-density structures, due to less competition for space between the atoms. Proof-of-concept experiments confirm that mixingmore » two different high-density forms of MnSe and MnTe stabilizes a Mn(Se,Te) alloy with a low-density wurtzite structure. This Mn(Se,Te) negative-pressure polymorph has 2x to 4x lower electron effective mass compared to MnSe and MnTe parent compounds and has a piezoelectric response that none of the parent compounds have. Lastly, this example shows how heterostructural alloying can lead to negative-pressure polymorphs with useful properties - materials that are otherwise nearly impossible to make.« less

Negative pressures and spallation in water drops subjected to nanosecond shock waves

DOE PAGES

Stan, Claudiu A.; Willmott, Philip R.; Stone, Howard A.; ...

2016-05-16

Most experimental studies of cavitation in liquid water at negative pressures reported cavitation at tensions significantly smaller than those expected for homogeneous nucleation, suggesting that achievable tensions are limited by heterogeneous cavitation. We generated tension pulses with nanosecond rise times in water by reflecting cylindrical shock waves, produced by X-ray laser pulses, at the internal surface of drops of water. Depending on the X-ray pulse energy, a range of cavitation phenomena occurred, including the rupture and detachment, or spallation, of thin liquid layers at the surface of the drop. When spallation occurred, we evaluated that negative pressures below –100 MPamore » were reached in the drops. As a result, we model the negative pressures from shock reflection experiments using a nucleation-and-growth model that explains how rapid decompression could outrun heterogeneous cavitation in water, and enable the study of stretched water close to homogeneous cavitation pressures.« less

Hydrodynamic performance and heat generation by centrifugal pumps.

PubMed

Ganushchak, Y; van Marken Lichtenbelt, W; van der Nagel, T; de Jong, D S

2006-11-01

For over a century, centrifugal pumps (CP) have been used in various applications, from large industrial pumps to flow pumps for aquariums. However, the use of CP as blood pumps has a rather short history. Consequently, the hydraulic performance data for a blood CP are limited. The aim of our investigation was to study the hydraulic performance and the heat generation of three commercially available CP: Bio-Medicus Bio-Pump BP80 (Medtronic), Rotaflow (Jostra Medizintechnik), and DeltaStream DP2 (MEDOS Medizintechnik AQ). The study was performed using a circuit primed with a water-glycerin mixture with a dynamic viscosity of 0.00272 pa/s. Pressure-flow curves were obtained by a stepwise stagnation of the pump outlet or inlet. The temperature changes were observed using ThermaCAM SC2000 (Flir Systems). The pumps' performance in close to clinical conditions ('operating region') was analysed in this report. The 'operating region' in the case of the BP80 is positioned around the pressure-flow curve at a pump speed of 3000 rpm. In the case of the Rotaflow, the 'operating region' was between the pump pressure-flow curves at a speed of 3000 and 4000 rpm, and the DP2 was found between 7000 and 8000 rpm. The standard deviation of mean pressure through the pump was used to characterise the stability of the pump. In experiments with outlet stagnation, the BP80 demonstrated high negative association between flow and pressure variability (r = -0.68, p < 0.001). In experiments with the DP2, this association was positive (r = 0.68, p < 0.001). All pumps demonstrated significantly higher variability of pressure in experiments with inlet stagnation in comparison to the experiments with outlet stagnation. The rise of relative temperature in the inlet of a pump was closely related to the flow rate. The heating of fluid was more pronounced in the 'zero-flow' mode, especially in experiments with inlet stagnation. In summary, (1) the 'zero-flow' regime, which is described in the manuals of some commercially-available pumps, is the use of the pump outside the allowable operating region. It is potentially dangerous and should, therefore, never be used in clinical settings. (2) Using centrifugal pumps for kinetic-assisted venous return can only be performed safely when the negative pressure at the inlet of the pump is monitored continuously. The maximum allowable negative pressure has to be defined for each type of pump, and must be based on pump performance.

Use of Closed Incision Management with Negative Pressure Therapy for Complex Cardiac Patients.

PubMed

Reddy, V Sreenath Seenu

2016-02-23

In patients with major comorbidities undergoing complex cardiothoracic surgery, incision management is critical. This retrospective review evaluated negative pressure over closed sternal incisions in cardiac patients with multiple comorbidities within 30 days post-median sternotomy. Records of post-sternotomy patients treated with Prevena™ Incision Management System (KCI, an Acelity company, San Antonio, TX), a closed incision negative pressure therapy (ciNPT), were reviewed from September 2010 through September 2014. Data collected included demographics, major comorbidities, types of surgery, relevant medical history, incision length, therapy duration, time to follow-up, and incision complications. Descriptive statistics were computed for continuous variables, frequency, and percentages for categorical variables. Twenty-seven patients were treated with ciNPT between September 2010 and September 2014. The mean patient age was 62.5 (SD 7.9), and the mean body mass index (BMI) was 38.5 (SD 4.4) kg/m(2). Risk factors included obesity (BMI ≥ 30 kg/m(2), 27/27; 100%), diabetes (25/27; 92.6%), hypertension (16/27; 59.3%), and 20/27 patients (74%) had ≥ 5 comorbidities. Mean ciNPT duration was 5.6 (SD 0.9) days. Within 30 days post-surgery, 21/27 (77.8%) patients had intact incisions with good reapproximation. Two patients experienced minor dehiscences; four cases of superficial cellulitis were treated and resolved. One patient with a dehiscence was readmitted for intravenous antibiotics and five patients were managed successfully with antibiotics as outpatients. All patients had intact incisions with good skin approximation at final follow-up. In this retrospective study of post-sternotomy patients at high risk of developing complications, ciNPT over closed sternal incisions resulted in favorable outcomes within 30 days of surgery.

Outcome of domiciliary nasal intermittent positive pressure ventilation in restrictive and obstructive disorders.

PubMed Central

Simonds, A. K.; Elliott, M. W.

1995-01-01

BACKGROUND--Nasal intermittent positive pressure ventilation (NIPPV) is a new technique which has rapidly supplanted other non-invasive methods of ventilation over the last 5-10 years. Data on its effectiveness are limited. METHODS--The outcome of long term domiciliary NIPPV has been analysed in 180 patients with hypercapnic respiratory failure predominantly due to chest wall restriction, neuromuscular disorders, or chronic obstructive lung disease. One hundred and thirty eight patients were started on NIPPV electively, and 42 following an acute hypercapnic exacerbation. Outcome measures were survival (five year probability of continuing NIPPV), pulmonary function, and health status. A crossover study from negative pressure ventilation to NIPPV was carried out in a subgroup of patients. RESULTS--Five year acturial probability of continuing NIPPV for individuals with early onset scoliosis (n = 47), previous poliomyelitis (n = 30), following tuberculous lung disease (n = 20), general neuromuscular disorders (n = 29), and chronic obstructive pulmonary disease (n = 33) was 79% (95% CI 66 to 92), 100%, 94% (95% CI 83 to 100), 81% (95% CI 61 to 100), 43% (95% CI 6 to 80), respectively. Most of the patients with bronchiectasis died within two years. One year after starting NIPPV electively the mean (SD) PaO2 compared with the pretreatment value was +1.8 (1.9) kPa, mean PaCO2 -1.4 (1.3) kPa in patients with extrapulmonary restrictive disorders, and PaO2 +0.8 (1.0) kPa, PaCO2 -0.9 (0.8) kPa in patients with obstructive lung disease. Arterial blood gas tensions improved in patients transferred from negative pressure ventilation to NIPPV. Health status was ranked highest in patients with early onset scoliosis, previous poliomyelitis, and following tuberculous lung disease. In the group as a whole health perception was comparable to outpatients with other chronic disorders. CONCLUSIONS--The long term outcome of domiciliary NIPPV in patients with chronic respiratory failure due to scoliosis, previous poliomyelitis, and chest wall and pulmonary disease secondary to tuberculosis is encouraging. The results of NIPPV in patients with COPD and progressive neuromuscular disorders show benefit in some subgroups. The outcome in end stage bronchiectasis is poor. Images PMID:7638799

Outcome of domiciliary nasal intermittent positive pressure ventilation in restrictive and obstructive disorders.

PubMed

Simonds, A K; Elliott, M W

1995-06-01

Nasal intermittent positive pressure ventilation (NIPPV) is a new technique which has rapidly supplanted other non-invasive methods of ventilation over the last 5-10 years. Data on its effectiveness are limited. The outcome of long term domiciliary NIPPV has been analysed in 180 patients with hypercapnic respiratory failure predominantly due to chest wall restriction, neuromuscular disorders, or chronic obstructive lung disease. One hundred and thirty eight patients were started on NIPPV electively, and 42 following an acute hypercapnic exacerbation. Outcome measures were survival (five year probability of continuing NIPPV), pulmonary function, and health status. A crossover study from negative pressure ventilation to NIPPV was carried out in a subgroup of patients. Five year acturial probability of continuing NIPPV for individuals with early onset scoliosis (n = 47), previous poliomyelitis (n = 30), following tuberculous lung disease (n = 20), general neuromuscular disorders (n = 29), and chronic obstructive pulmonary disease (n = 33) was 79% (95% CI 66 to 92), 100%, 94% (95% CI 83 to 100), 81% (95% CI 61 to 100), 43% (95% CI 6 to 80), respectively. Most of the patients with bronchiectasis died within two years. One year after starting NIPPV electively the mean (SD) PaO2 compared with the pretreatment value was +1.8 (1.9) kPa, mean PaCO2 -1.4 (1.3) kPa in patients with extrapulmonary restrictive disorders, and PaO2 +0.8 (1.0) kPa, PaCO2 -0.9 (0.8) kPa in patients with obstructive lung disease. Arterial blood gas tensions improved in patients transferred from negative pressure ventilation to NIPPV. Health status was ranked highest in patients with early onset scoliosis, previous poliomyelitis, and following tuberculous lung disease. In the group as a whole health perception was comparable to outpatients with other chronic disorders. The long term outcome of domiciliary NIPPV in patients with chronic respiratory failure due to scoliosis, previous poliomyelitis, and chest wall and pulmonary disease secondary to tuberculosis is encouraging. The results of NIPPV in patients with COPD and progressive neuromuscular disorders show benefit in some subgroups. The outcome in end stage bronchiectasis is poor.

[Canopy conductance characteristics of poplar in agroforestry system in west Liaoning Province of Northeast China].

PubMed

Li, Zheng; Niu, Li-Hua; Yuan, Feng-Hui; Guan, De-Xin; Wang, An-Zhi; Jin, Chang-Jie; Wu, Jia-Bing

2012-11-01

By using Granier' s thermal dissipation probe, the sap flow of poplar in a poplar-maize agroforestry system in west Liaoning was continuously measured, and as well, the environmental factors such as air temperature, air humidity, net radiation, wind speed, soil temperature, and soil moisture content were synchronically measured. Based on the sap flow data, the canopy conductance of poplar was calculated with simplified Penman-Monteith equation. In the study area, the diurnal variation of poplar' s canopy conductance showed a "single peak" curve, whereas the seasonal variation showed a decreasing trend. There was a negative logarithm relationship between the canopy conductance and vapor pressure deficit, with the sensitivity of canopy conductance to vapor pressure deficit change decreased gradually from May to September. The canopy conductance had a positive relationship with solar radiation. In different months, the correlation degree of canopy conductance with environmental factors differed. The vapor pressure deficit in the whole growth period of poplar was the most significant environmental factor correlated with the canopy conductance.

Complementary Effects of Negative-Pressure Wound Therapy and Pulsed Radiofrequency Energy on Cutaneous Wound Healing in Diabetic Mice.

PubMed

Chen, Bin; Kao, Huang-Kai; Dong, Ziqing; Jiang, Zhaohua; Guo, Lifei

2017-01-01

Negative-pressure wound therapy and pulsed radiofrequency energy are two clinical modalities used to treat soft-tissue wounds. They are purported to affect healing differently. The aim of this experimental study was to contrast the two modalities at a mechanistic level and to investigate whether their combined therapy could achieve additive and complementary effects on wound healing. Full-thickness dorsal cutaneous wounds of diabetic, db/db, mice were treated with either negative-pressure wound therapy, pulsed radiofrequency energy, or combined therapies. Macroscopic healing kinetics were examined. Epidermal regeneration (proliferation rate and length of reepithelialization) and neovascularization (blood vessel density) were investigated. Messenger RNA levels indicative of angiogenic (basic fibroblast growth factor), profibrotic (transforming growth factor-β), epidermal proliferative (keratinocyte growth factor), and extracellular matrix remodeling (collagen 1) processes were measured in wound tissues. All three treatment groups displayed faster wound healing. The negative-pressure wound therapy/pulsed radiofrequency energy combined therapy led to significantly faster healing than either the negative-pressure wound therapy or pulsed radiofrequency energy therapy alone. Epidermal regeneration and neovascularization were enhanced in all three groups. The two negative-pressure wound therapy groups (alone and combined with pulsed radiofrequency energy) demonstrated more significant increases in expression of all assayed growth factors than the pulsed radiofrequency energy group. Furthermore, the combined therapy exhibited a more profound elevation in collagen 1 expression than either of the two therapies alone. Combining the negative-pressure wound therapy and pulsed radiofrequency energy modalities can achieve additive benefits in cutaneous healing, and the two therapies can be easily used together to complement each other in clinical wound treatments.

Blood pressure responses to LBNP in nontrained and trained hypertensive rats

NASA Technical Reports Server (NTRS)

Bedford, T. G.; Tipton, C. M.

1992-01-01

To study the influences of 16 wk of endurance training on the reflex regulation of resting blood pressure, nontrained (NT) and trained (T) female hypertensive rats (SHR) were subjected to conditions of lower body negative pressure (LBNP). Measurements of muscle cytochrome oxidase activity and run time to exhaustion indicated that the animals were endurance trained. The rats (NT = 6, T = 7) were tranquilized with 300-600 micrograms.kg-1 diazepam (IV) before heart rates and blood pressures were measured over a range of 2.5-10.0 mm Hg of negative pressure. When subjected to conditions of LBNP, the reflex tachycardia of the T group was greater than the NT at the lower (-2.5 and -5.0 mm Hg) negative pressures. Although arterial pressure declines were similar in both groups, the T group experienced significantly less of a decline in central venous pressure than the NT animals. When chlorisondamine was used as a ganglionic blocker (2.5 mg.kg-1, IV), the fall in CVP at 10 mm Hg negative pressure was greater for the NT group while the fall in the initial systemic arterial pressure was more for the T group. From these results we concluded that training had altered the interaction between cardiopulmonary and arterial baroreflexes in these hypertensive rats and a nonneural component had been altered such as cardiac function.

Vectorcardiographic results from Skylab medical experiment M092: Lower body negative pressure

NASA Technical Reports Server (NTRS)

Hoffler, G. W.; Johnson, R. L.; Nicogossian, A. E.; Bergman, S. A., Jr.; Jackson, M. M.

1974-01-01

Vectorcardiograms were recorded via a modified Frank lead system from all crewmen of the three Skylab missions in conjuction with the Lower Body Negative Pressure - M092 Experiment. Data were analyzed by a specially developed computer program (VECTAN). Design of the test sequences allowed direct comparisons of supine resting, Earth based (reference) vectorcardiograms with those taken during lower body negative pressure stress and those obtained at rest in orbit, as well as combinations of these conditions. Results revealed several statistically significant space flight related changes; namely, increased testing and lower body negative pressure stressed heart rates, modestly increased PR interval and corrected QTC interval, and greatly increased P and QPS loop maximal amplitudes. In addition, orientation changes in the QRS maximum vector and the J-vector at rest in space seem quite consistent among crewmen and different from those caused by the application of lower body negative pressure. No clinical abnormalities were observed. Etiology of these findings is conjectured to be, at least in part, related to fluid mass shifts occurring in weightlessness and attendant alterations in cardiovascular dynamics and myocardial autonomic control mechanisms.

Neurohumoral Mechanisms Associated with Orthostasis: Reaffirmation of the Significant Contribution of the Heart Rate Response

DTIC Science & Technology

2014-06-30

baroreceptor stimu- lation (i.e., lower arterial blood pressure ) suggests an association between a depressed baroreflex response and development of...orthostatic tolerance, blood pressure regulation, lower body negative pressure , parasympathetic activity, sympathetic activity, propranolol, atropine...body negative pressure (LBNP) so that comparisons of physiology in individuals with high and low tolerance to central hypovolemia could be studied at

Tongue pressure profile training for dysphagia post stroke (TPPT): study protocol for an exploratory randomized controlled trial.

PubMed

Steele, Catriona M; Bayley, Mark A; Péladeau-Pigeon, Melanie; Stokely, Shauna L

2013-05-07

It is estimated that approximately 50% of stroke survivors will experience swallowing difficulty, or dysphagia. The associated sequelae of dysphagia include dehydration, malnutrition, and aspiration pneumonia, all of which have can have serious medical consequences. To improve swallowing safety and efficiency, alternative nutritional intake methods (for example, a feeding tube) or a modified diet texture (such as pureed foods or thickened liquids) may be recommended but these modifications may negatively affect quality of life. An alternative approach to treating dysphagia has emerged over the past few years, targeting stronger lingual muscles through maximal isometric pressure tasks. Although these studies have shown promising results, thin-liquid bolus control continues to be challenging for patients with dysphagia. Previous work investigating lingual pressures when healthy participants swallow has suggested that greater task specificity in lingual exercises may yield improved results with thin liquids. This is a small, exploratory randomized clinical trial being conducted with post-stroke patients 4 to 20 weeks after onset of dysphagia secondary to impaired lingual control. At enrollment, participants are randomly assigned to one of two treatment protocols, either tongue pressure profile training (TPPT) or the control treatment, tongue pressure strength-and-accuracy training (TPSAT). Each treatment protocol consists of 24 sessions of treatment over 8 to 12 weeks with monitoring of tongue pressure as well as a baseline and outcome videofluoroscopic swallowing study. Tongue pressure measures, videofluoroscopic measures, and functional outcome measures will be obtained following training of 60 participants (30 in each condition), to determine whether TPPT yields better outcomes. This study will continue to explore options beyond tube feeding and modified diets for people with neurogenic dysphagia following stroke. Should the novel protocol, TPPT, prove to be more effective than the TPSAT protocol, this may influence standards of care and best practices for patients with dysphagia involving impaired thin-liquid control as a result of stroke. Clinicaltrials.gov http://NCT01370083.

75 FR 70112 - Medical Devices; General and Plastic Surgery Devices; Classification of Non-Powered Suction...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-11-17

... Suction Apparatus Device Intended for Negative Pressure Wound Therapy AGENCY: Food and Drug Administration...- powered suction apparatus device intended for negative pressure wound therapy (NPWT) into class II... ``Class II Special Controls Guidance Document: Non-Powered Suction Apparatus Device Intended for Negative...

Heated, humidified high-flow nasal cannula therapy: yet another way to deliver continuous positive airway pressure?

PubMed

Kubicka, Zuzanna J; Limauro, Joseph; Darnall, Robert A

2008-01-01

The goal was to estimate the level of delivered continuous positive airway pressure by measuring oral cavity pressure with the mouth closed in infants of various weights and ages treated with heated, humidified high-flow nasal cannula at flow rates of 1-5 L/minute. We hypothesized that clinically relevant levels of continuous positive airway pressure would not be achieved if a nasal leak is maintained. After performing bench measurements and demonstrating that oral cavity pressure closely approximated levels of traditionally applied nasal continuous positive airway pressure, we successfully measured oral cavity pressure during heated, humidified, high-flow nasal cannula treatment in 27 infants. Small (outer diameter: 0.2 cm) cannulae were used for all infants, and flow rates were left as ordered by providers. Bench measurements showed that, for any given leak size, there was a nearly linear relationship between flow rate and pressure. The highest pressure achieved was 4.5 cmH2O (flow rate: 8 L/minute; leak: 3 mm). In our study infants (postmenstrual age: 29.1-44.7 weeks; weight: 835-3735 g; flow rate: 1-5 L/minute), no pressure was generated with the mouth open at any flow rate. With the mouth closed, the oral cavity pressure was related to both flow rate and weight. For infants of < or = 1500 g, there was a linear relationship between flow rate and oral cavity pressure. Oral cavity pressure can estimate the level of continuous positive airway pressure. Continuous positive airway pressure generated with heated, humidified, high-flow nasal cannula treatment depends on the flow rate and weight. Only in the smallest infants with the highest flow rates, with the mouth fully closed, can clinically significant but unpredictable levels of continuous positive airway pressure be achieved. We conclude that heated, humidified high-flow nasal cannula should not be used as a replacement for delivering continuous positive airway pressure.

The importance of clinical monitoring for compliance with Continuous Positive Airway Pressure.

PubMed

Pelosi, Lucas B; Silveira, Mariana L C; Eckeli, Alan L; Chayamiti, Emilia M P C; Almeida, Leila A; Sander, Heidi H; Küpper, Daniel S; Valera, Fabiana C P

Obstructive sleep apnea syndrome is currently a public health problem of great importance. When misdiagnosed or improperly treated, it can lead to serious consequences on patients' quality of life. The gold standard treatment for cases of obstructive sleep apnea syndrome, especially in mild to severe and symptomatic cases, is continuous positive airway pressure therapy. Compliance with continuous positive airway pressure therapy is directly dependent on the active participation of the patient, which can be influenced by several factors. The objective of this study is to describe the factors related to compliance with continuous positive airway pressure therapy, and to analyze which associated factors directly influence the efficiency of the treatment. Patients who received continuous positive airway pressure therapy through the Municipal Health Department of the city of Ribeirão Preto were recruited. A structured questionnaire was administered to the patients. Compliance with continuous positive airway pressure therapy was assessed by average hours of continuous positive airway pressure therapy usage per night. Patients with good compliance (patients using continuous positive airway pressure therapy ≥4h/night) were compared to those with poor compliance (patients using <4h/night). 138 patients were analyzed: 77 (55.8%) were considered compliant while 61 (44.2%) were non-compliant. The comparison between the two groups showed that regular monitoring by a specialist considerably improved compliance with continuous positive airway pressure therapy (odds ratio, OR=2.62). Compliance with continuous positive airway pressure therapy is related to educational components, which can be enhanced with continuous and individualized care to patients with obstructive sleep apnea syndrome. Copyright © 2016 Associação Brasileira de Otorrinolaringologia e Cirurgia Cérvico-Facial. Published by Elsevier Editora Ltda. All rights reserved.

Final report on EURAMET.M.P-S12 — Bilateral supplementary comparison of the national pressure standards of CMI and INRIM in the range 300 Pa to 15 kPa of negative gauge pressure

NASA Astrophysics Data System (ADS)

Krajícek, Zdenek; Bergoglio, Mercede; Pražák, Dominik; Pasqualin, Stefano

2014-01-01

This report describes a EURAMET bilateral supplementary comparison between Czech CMI and Italian INRIM in low negative gauge pressure in gas (nitrogen), denoted as EURAMET.M.P-S12. The digital non-rotating pressure balance FPG8601 manufactured by Fluke/DH-Instruments, USA is normally used for gauge and absolute pressures in the range from 1 Pa to 15 kPa, but with some modifications it can be used also for the negative gauge pressures in the same range. During the preparation of the visit of INRIM at CMI for the last comparison within the framework of EURAMET.M.P-K4.2010, it was agreed to also perform an additional comparison in the range from 300 Pa to 15 kPa of negative gauge pressure. The measurements were performed in October 2012. Both institutes successfully proved their equivalence in all the tested points in the range from 300 Pa to 15 kPa of negative gauge pressure in a comparison that had, so far, been unique. . Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Pump out the volume--The effect of tracheal and subelytral pressure pulses on convective gas exchange in a dung beetle, Circellium bacchus (Fabricus).

PubMed

Duncan, Frances D; Förster, Thomas D; Hetz, Stefan K

2010-05-01

Many flightless beetles like the large apterous dung beetle Circellium bacchus, possess a subelytral cavity (SEC) providing an extra air space below the elytra which connects to the tracheal system (TS) via metathoracic and abdominal spiracles. By measuring subelytral and intratracheal pressure as well as body movements and gas exchange simultaneously in a flow-through setup, we investigated the contribution of convection on Circellium respiratory gas exchange. No constriction phase was observed. TS and SEC pressures were always around atmospheric values. During interburst phase open abdominal spiracles and a leaky SEC led to small CO(2)-peaks on a continuous CO(2) baseline, driven by intermittent positive tracheal pressure peaks in anti-phase with small negative subelytral pressure peaks caused by dorso-ventral tergite action. Spiracle opening was accompanied by two types of body movements. Higher frequency telescoping body movements at the beginning of opening resulted in high amplitude SEC and TS pressure peaks. High frequency tergite movements caused subelytral pressure peaks and led to a saw tooth like CO(2) release pattern in a burst. We propose that during the burst open mesothoracic spiracles increase the compliance of the subelytral cavity allowing big volumes of tracheal air being pulled out by convection. Copyright 2009 Elsevier Ltd. All rights reserved.

Polymyxin B moderates acidosis and hypotension in established, experimental gram-negative septicemia.

PubMed

Flynn, P M; Shenep, J L; Stokes, D C; Fairclough, D; Hildner, W K

1987-11-01

Polymyxin B (PMB), an antibiotic, and sodium deoxycholate (NaD), a bile salt, are surface-active agents. Each protected mice against an otherwise lethal challenge with purified endotoxin (P less than .001). To determine if either of these agents was effective in treating established, overwhelming gram-negative septicemia, we infected rabbits by intraperitoneal injection of Escherichia coli K1. Animals were treated with moxalactam 1 hr after infection, then randomly assigned to groups receiving either saline, PMB, or NaD. Serial samples of blood were assayed for bacterial concentration, levels of plasma endotoxin, arterial blood gases, and complete blood cell counts. Physiologic functions were monitored continuously. Although levels of bacteremia and endotoxemia were similar in all three groups, rabbits receiving PMB had significantly higher mean arterial blood pressure, blood pH, and bicarbonate concentrations than did control rabbits (P less than .05). Rabbits receiving NaD fared no better than controls. In this model, PMB moderates some of the deleterious effects of established, overwhelming gram-negative bacterial sepsis.

Experimental evidence for negative turgor pressure in small leaf cells of Robinia pseudoacacia L versus large cells of Metasequoia glyptostroboides Hu et W.C. Cheng. 2. Höfler diagrams below the volume of zero turgor and the theoretical implication for pressure-volume curves of living cells.

PubMed

Yang, Dongmei; Li, Junhui; Ding, Yiting; Tyree, Melvin T

2017-03-01

The physiological advantages of negative turgor pressure, P t , in leaf cells are water saving and homeostasis of reactants. This paper advances methods for detecting the occurrence of negative P t in leaves. Biomechanical models of pressure-volume (PV) curves predict that negative P t does not change the linearity of PV curve plots of inverse balance pressure, P B , versus relative water loss, but it does predict changes in either the y-intercept or the x-intercept of the plots depending on where cell collapse occurs in the P B domain because of negative P t . PV curve analysis of Robinia leaves revealed a shift in the x-intercept (x-axis is relative water loss) of PV curves, caused by negative P t of palisade cells. The low x-intercept of the PV curve was explained by the non-collapse of palisade cells in Robinia in the P B domain. Non-collapse means that P t smoothly falls from positive to negative values with decreasing cell volume without a dramatic change in slope. The magnitude of negative turgor in non-collapsing living cells was as low as -1.3 MPa and the relative volume of the non-collapsing cell equaled 58% of the total leaf cell volume. This study adds to the growing evidence for negative P t . © 2016 John Wiley & Sons Ltd.

Influence of hypoxia induced by sleep disordered breathing in case of hypertension and atrial fibrillation.

PubMed

Ando, Shin-Ichi

2018-07-01

Sleep disordered breathing (SDB) has been recognized as one of the important causes or factors of worsening for various cerebro- and cardiovascular diseases. On the other hand, a recent large randomized study and meta-analysis about the effect of continuous positive airway pressure (CPAP) indicated no or only minor effects to improve the outcome of SDB patients. Accumulating evidence has indicated that the key factor of the link between SDB and cardiovascular diseases might be hypoxia caused during repetitive long apneic episodes. Hypertension and atrial fibrillation (AF) are two important cardiovascular diseases that relate to SDB and the therapeutic consequences by CPAP treatment have been studied. As for the mechanism that elevates blood pressure during night, stimulation of chemoreceptors by hypoxia and the resultant increase in sympathetic nervous activity is the first step and repetitive hypoxic stimulation changes the characteristics of chemoreceptors and baroreceptors resulting in daytime hypertension. Pathological changes in the atrial muscle in SDB patients might be a result of repetitive hypoxia and atrial expansion. As for triggering AF, several animal studies revealed that the changes in autonomic nervous system caused by hypoxia and negative intra-thoracic pressure might be crucial. However, a recent observational study could not show the relation between SDB and AF. The difference between the previous studies and this negative study seems to exist in the difference of the severity of SDB or the degree of hypoxia. Such a difference might be also one of the reasons why a recent randomized trial to prove the effect of CPAP in cardio- or cerebrovascular patients failed to improve the patient prognosis. Hence, in this review, the relationship between hypoxia and onset or continuation of hypertension and AF will be reconsidered to understand the fundamental and robust relationship between SDB and these cardiovascular diseases. Copyright © 2018 Japanese College of Cardiology. Published by Elsevier Ltd. All rights reserved.

A pressure-amplifying framework material with negative gas adsorption transitions.

PubMed

Krause, Simon; Bon, Volodymyr; Senkovska, Irena; Stoeck, Ulrich; Wallacher, Dirk; Többens, Daniel M; Zander, Stefan; Pillai, Renjith S; Maurin, Guillaume; Coudert, François-Xavier; Kaskel, Stefan

2016-04-21

Adsorption-based phenomena are important in gas separations, such as the treatment of greenhouse-gas and toxic-gas pollutants, and in water-adsorption-based heat pumps for solar cooling systems. The ability to tune the pore size, shape and functionality of crystalline porous coordination polymers--or metal-organic frameworks (MOFs)--has made them attractive materials for such adsorption-based applications. The flexibility and guest-molecule-dependent response of MOFs give rise to unexpected and often desirable adsorption phenomena. Common to all isothermal gas adsorption phenomena, however, is increased gas uptake with increased pressure. Here we report adsorption transitions in the isotherms of a MOF (DUT-49) that exhibits a negative gas adsorption; that is, spontaneous desorption of gas (methane and n-butane) occurs during pressure increase in a defined temperature and pressure range. A combination of in situ powder X-ray diffraction, gas adsorption experiments and simulations shows that this adsorption behaviour is controlled by a sudden hysteretic structural deformation and pore contraction of the MOF, which releases guest molecules. These findings may enable technologies using frameworks capable of negative gas adsorption for pressure amplification in micro- and macroscopic system engineering. Negative gas adsorption extends the series of counterintuitive phenomena such as negative thermal expansion and negative refractive indices and may be interpreted as an adsorptive analogue of force-amplifying negative compressibility transitions proposed for metamaterials.

Bayes to the Rescue: Continuous Positive Airway Pressure Has Less Mortality Than High-Flow Oxygen.

PubMed

Modesto I Alapont, Vicent; Khemani, Robinder G; Medina, Alberto; Del Villar Guerra, Pablo; Molina Cambra, Alfred

2017-02-01

The merits of high-flow nasal cannula oxygen versus bubble continuous positive airway pressure are debated in children with pneumonia, with suggestions that randomized controlled trials are needed. In light of a previous randomized controlled trial showing a trend for lower mortality with bubble continuous positive airway pressure, we sought to determine the probability that a new randomized controlled trial would find high-flow nasal cannula oxygen superior to bubble continuous positive airway pressure through a "robust" Bayesian analysis. Sample data were extracted from the trial by Chisti et al, and requisite to "robust" Bayesian analysis, we specified three prior distributions to represent clinically meaningful assumptions. These priors (reference, pessimistic, and optimistic) were used to generate three scenarios to represent the range of possible hypotheses. 1) "Reference": we believe bubble continuous positive airway pressure and high-flow nasal cannula oxygen are equally effective with the same uninformative reference priors; 2) "Sceptic on high-flow nasal cannula oxygen": we believe that bubble continuous positive airway pressure is better than high-flow nasal cannula oxygen (bubble continuous positive airway pressure has an optimistic prior and high-flow nasal cannula oxygen has a pessimistic prior); and 3) "Enthusiastic on high-flow nasal cannula oxygen": we believe that high-flow nasal cannula oxygen is better than bubble continuous positive airway pressure (high-flow nasal cannula oxygen has an optimistic prior and bubble continuous positive airway pressure has a pessimistic prior). Finally, posterior empiric Bayesian distributions were obtained through 100,000 Markov Chain Monte Carlo simulations. In all three scenarios, there was a high probability for more death from high-flow nasal cannula oxygen compared with bubble continuous positive airway pressure (reference, 0.98; sceptic on high-flow nasal cannula oxygen, 0.982; enthusiastic on high-flow nasal cannula oxygen, 0.742). The posterior 95% credible interval on the difference in mortality identified a future randomized controlled trial would be extremely unlikely to find a mortality benefit for high-flow nasal cannula oxygen over bubble continuous positive airway pressure, regardless of the scenario. Interpreting these findings using the "range of practical equivalence" framework would recommend rejecting the hypothesis that high-flow nasal cannula oxygen is superior to bubble continuous positive airway pressure for these children. For children younger than 5 years with pneumonia, high-flow nasal cannula oxygen has higher mortality than bubble continuous positive airway pressure. A future randomized controlled trial in this population is unlikely to find high-flow nasal cannula oxygen superior to bubble continuous positive airway pressure.

Stereotype threat engenders neural attentional bias toward negative feedback to undermine performance.

PubMed

Forbes, Chad E; Leitner, Jordan B

2014-10-01

Stereotype threat, a situational pressure individuals experience when they fear confirming a negative group stereotype, engenders a cascade of physiological stress responses, negative appraisals, and performance monitoring processes that tax working memory resources necessary for optimal performance. Less is known, however, about how stereotype threat biases attentional processing in response to performance feedback, and how such attentional biases may undermine performance. Women received feedback on math problems in stereotype threatening compared to stereotype-neutral contexts while continuous EEG activity was recorded. Findings revealed that stereotype threatened women elicited larger midline P100 ERPs, increased phase locking between anterior cingulate cortex and dorsolateral prefrontal cortex (two regions integral for attentional processes), and increased power in left fusiform gyrus in response to negative feedback compared to positive feedback and women in stereotype-neutral contexts. Increased power in left fusiform gyrus in response to negative feedback predicted underperformance on the math task among stereotype threatened women only. Women in stereotype-neutral contexts exhibited the opposite trend. Findings suggest that in stereotype threatening contexts, neural networks integral for attention and working memory are biased toward negative, stereotype confirming feedback at very early speeds of information processing. This bias, in turn, plays a role in undermining performance. Copyright © 2014 Elsevier B.V. All rights reserved.

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

2014-10-01

pulse oximeter (Cardiocap/5; Datex-Ohmeda, Louisville, CO). The EKG and pulse oximeter tracings were interfaced with a personal computer for con- tinuous...responses to reduced central venous pressure (CVP) and pulse pressure (PP) elicited during graded lower body negative pressure (LBNP) to those observed...Johnson BD, Curry TB, Convertino VA, & Joyner MJ. The association between pulse pressure and stroke volume during lower body negative pressure and

Prophylactic negative-pressure wound therapy after cesarean is associated with reduced risk of surgical site infection: a systematic review and meta-analysis.

PubMed

Yu, Lulu; Kronen, Ryan J; Simon, Laura E; Stoll, Carolyn R T; Colditz, Graham A; Tuuli, Methodius G

2018-02-01

The objective of the study was to assess the effect of prophylactic negative-pressure wound therapy on surgical site infections and other wound complications in women after cesarean delivery. We searched Ovid Medline, Embase, SCOPUS, Cochrane Database of Systematic Reviews, and ClinicalTrials.gov. We included randomized controlled trials and observational studies comparing prophylactic negative-pressure wound therapy with standard wound dressing for cesarean delivery. The primary outcome was surgical site infection after cesarean delivery. Secondary outcomes were composite wound complications, wound dehiscence, wound seroma, endometritis, and hospital readmission. Heterogeneity was assessed using Higgin's I 2 . Relative risks with 95% confidence intervals were calculated using random-effects models. Six randomized controlled trials and 3 cohort studies in high-risk mostly obese women met inclusion criteria and were included in the meta-analysis. Six were full-text articles, 2 published abstracts, and 1 report of trial results in ClinicalTrials.gov. Studies were also heterogeneous in the patients included and type of negative-pressure wound therapy device. The risk of surgical site infection was significantly lower with the use of prophylactic negative-pressure wound therapy compared with standard wound dressing (7 studies: pooled risk ratio, 0.45; 95% confidence interval, 0.31-0.66; adjusted risk ratio, -6.0%, 95% confidence interval, -10.0% to -3.0%; number needed to treat, 17, 95% confidence interval, 10-34). There was no evidence of significant statistical heterogeneity (I 2  = 9.9%) or publication bias (Egger P = .532). Of the secondary outcomes, only composite wound complications were significantly reduced in patients receiving prophylactic negative-pressure wound therapy compared with standard dressing (9 studies: pooled risk ratio, 0.68, 95% confidence interval, 0.49-0.94). Studies on the effectiveness of prophylactic negative-pressure wound therapy at cesarean delivery are heterogeneous but suggest a reduction in surgical site infection and overall wound complications. Larger definitive trials are needed to clarify the clinical utility of prophylactic negative-pressure wound therapy after cesarean delivery. Copyright © 2017 Elsevier Inc. All rights reserved.

Partner Pressure, Victimization History, and Alcohol: Women’s Condom-Decision Abdication Mediated by Mood and Anticipated Negative Partner Reaction

PubMed Central

George, William H.; Davis, Kelly Cue; Masters, N. Tatiana; Kajumulo, Kelly F.; Stappenbeck, Cynthia A.; Norris, Jeanette; Heiman, Julia R.; Staples, Jennifer M.

2015-01-01

Highly intoxicated versus sober women were evaluated using multi-group path analyses to test the hypothesis that sexual victimization history would interact with partner pressure to forgo condom use, resulting in greater condom-decision abdication – letting the man decide whether or not to use a condom. After beverage administration, community women (n=408) projected themselves into a scenario depicting a male partner exerting high or low pressure for unprotected sex. Mood, anticipated negative reactions from the partner, and condom-decision abdication were assessed. In both control and alcohol models, high pressure increased anticipated negative partner reaction, and positive mood was associated with increased abdication. In the alcohol model, victimization predicted abdication via anticipated negative partner reaction, and pressure decreased positive mood and abdication. In the control model, under high pressure, victimization history severity was positively associated with abdication. Findings implicate condom-decision abdication as an important construct in understanding how women’s sexual victimization histories may exert sustained impact on sexual interactions. PMID:26340952

Stress and Negative Relationship Quality among Older Couples: Implications for Blood Pressure

PubMed Central

Newton, Nicky J.; Cranford, James A.; Ryan, Lindsay H.

2016-01-01

Objectives: The cardiovascular system may represent a significant pathway by which marriage and stress influence health, but research has focused on married individuals cross-sectionally. This study examined associations among chronic stress, negative spousal relationship quality, and systolic blood pressure over time among middle-aged and older husbands and wives. Method: Participants were from the nationally representative longitudinal Health and Retirement Study. A total of 1,356 (N = 2,712) married and cohabitating couples completed psychosocial and biomeasure assessments in waves 2006 and 2010. Analyses examined whether Wave 1 (2006) relationship quality and stress were associated with changes in blood pressure over time. Results: The effects of stress and negative relationship quality were dyadic and varied by gender. Husbands had increased blood pressure when wives reported greater stress, and this link was exacerbated by negative spousal relationship quality. Negative relationship quality predicted increased blood pressure when both members of the couple reported negative quality relations. Discussion: Findings support the dyadic biopsychosocial model of marriage and health indicating: (a) stress and relationship quality directly effect the cardiovascular system, (b) relationship quality moderates the effect of stress, and (c) the dyad rather than only the individual should be considered when examining marriage and health. PMID:25852106

Gasdynamic Inlet Isolation in Rotating Detonation Engine

DTIC Science & Technology

2010-12-01

2D Total Variation Diminishing (TVD): Continuous Riemann Solver Minimum Dissipation: LHS & RHS Activate pressure switch : Supersonic Activate...Total Variation Diminishing (TVD) limiter: Continuous Riemann Solver Minimum Dissipation: LHS & RHS Activate pressure switch : Supersonic Activate...Continuous 94 Riemann Solver Minimum Dissipation: LHS & RHS Activate pressure switch : Supersonic Activate pressure gradient switch: Normal

Efficacy of a pressure-sensing mattress cover system for reducing interface pressure: study protocol for a randomized controlled trial.

PubMed

Wong, Holly; Kaufman, Jaime; Baylis, Barry; Conly, John M; Hogan, David B; Stelfox, Henry T; Southern, Danielle A; Ghali, William A; Ho, Chester H

2015-09-29

Interface pressure is a key risk factor in the development of pressure ulcers. Visual feedback of continuous interface pressure between the body and support surface could inform clinicians on repositioning strategies and play a key role in an overall strategy for the prevention and management of pressure ulcers. A parallel two-group randomized controlled clinical trial will be conducted to study the effect of continuous pressure imaging on reducing interface pressure and on the incidence of pressure ulcers in vulnerable hospital patients. A total of 678 eligible consenting inpatients at risk of pressure ulcer development in a tertiary acute care institution will be randomly allocated to either having the ForeSite PT™ system with the liquid-crystal display monitor turned on to provide visual feedback to the clinicians while also collecting continuous interface pressure data (intervention group) or to having the ForeSite PT™ system with monitor turned off (that is, not providing visual feedback) but still collecting continuous interface pressure data (control group), in a ratio of 1:1. Continuous interface pressure data will be collected in both groups for 3 days (72 h). Data collection will continue until discharge for a subset of approximately 60 patients. The primary outcome will be the differences in the two groups' interface pressure analysis. Interface pressure readings will be collected through hourly samplings of continuous interface pressure recordings. Secondary outcomes will be the differences between the two groups in pressure-related skin and soft tissue changes in areas at risk of pressure ulcer (obtained at baseline within 24 h of admission) and on the third day of the trial or at discharge and perceptions of the intervention by patients and clinicians (obtained on the third day or at discharge). This will be the first randomized controlled trial to investigate the effect of visual feedback with continuous interface pressure of vulnerable hospital patients across different care settings, and the association between interface pressure and development of pressure-related skin and soft tissue changes. The results could provide important information to guide clinical practice in the prevention and management of pressure ulcers. ClinicalTrials.gov NCT02325388 (date of registration: 24 December 2014).

Does teacher evaluation based on student performance predict motivation, well-being, and ill-being?

PubMed

Cuevas, Ricardo; Ntoumanis, Nikos; Fernandez-Bustos, Juan G; Bartholomew, Kimberley

2018-06-01

This study tests an explanatory model based on self-determination theory, which posits that pressure experienced by teachers when they are evaluated based on their students' academic performance will differentially predict teacher adaptive and maladaptive motivation, well-being, and ill-being. A total of 360 Spanish physical education teachers completed a multi-scale inventory. We found support for a structural equation model that showed that perceived pressure predicted teacher autonomous motivation negatively, predicted amotivation positively, and was unrelated to controlled motivation. In addition, autonomous motivation predicted vitality positively and exhaustion negatively, whereas controlled motivation and amotivation predicted vitality negatively and exhaustion positively. Amotivation significantly mediated the relation between pressure and vitality and between pressure and exhaustion. The results underline the potential negative impact of pressure felt by teachers due to this type of evaluation on teacher motivation and psychological health. Copyright © 2018 Society for the Study of School Psychology. Published by Elsevier Ltd. All rights reserved.

The Temporal Dynamics of Two Response-Focused Forms of Emotion Regulation: Experiential, Expressive, and Autonomic Consequences

PubMed Central

Dan-Glauser, Elise S.; Gross, James J.

2011-01-01

This study examines the early affective consequences of two close forms of suppression. Participants (N=37) were shown negative, positive, and neutral pictures and cued either to attend to the pictures, or to perform expressive or physiological suppression (i.e. reduce body reactions). Continuous measures of experience, expressivity, and autonomic responses showed that both suppression strategies produced rapid response modulation. Common effects of the two strategies included a transient increase in negative feeling, a durable decrease in positive feeling, and a decrease in expressivity, cardiovascular activity, and oxygenation. The two strategies were significantly different only in response to positive stimuli, with physiological suppression showing a larger decrease in experience intensity and blood pressure. These results suggest a strong overlap between the two suppression strategies in terms of their early impact on emotional responses. PMID:21361967

Use of negative-pressure dressings and split-thickness skin grafts following penile shaft reduction and reduction scrotoplasty in the management of penoscrotal elephantiasis.

PubMed

Stokes, Tracey H; Follmar, Keith E; Silverstein, Ari D; Weizer, Alon Z; Donatucci, Craig F; Anderson, Everett E; Erdmann, Detlev

2006-06-01

From 1988 to 2005, 8 men who presented with penoscrotal elephantiasis underwent penile shaft degloving and reduction scrotoplasty, followed by transplantation of a split-thickness skin graft (STSG) to the penile shaft. The etiology of elephantiasis in these patients included self-injection of viscous fluid and postsurgical obstructive lymphedema. In the 6 most recent cases, negative-pressure dressings were applied over the STSG to promote graft take, and STSG take rate was 100%. The results of our series corroborate those of a previous report, which showed circumferential negative-pressure dressings to be safe and efficacious in bolstering STSGs to the penile shaft. Furthermore, these results suggest that the use of negative-pressure dressings may improve graft take in this patient population.

A review of negative-pressure wound therapy in the management of burn wounds.

PubMed

Kantak, Neelesh A; Mistry, Riyam; Halvorson, Eric G

2016-12-01

Negative pressure has been employed in various aspects of burn care and the aim of this study was to evaluate the evidence for each of those uses. The PubMed and Cochrane CENTRAL databases were queried for articles in the following areas: negative pressure as a dressing for acute burns, intermediate treatment prior to skin grafting, bolster for skin autografts, dressing for integration of dermal substitutes, dressing for skin graft donor sites, and integrated dressing in large burns. Fifteen studies met our inclusion criteria. One study showed negative pressure wound therapy improved perfusion in acute partial-thickness burns, 8 out of 9 studies showed benefits when used as a skin graft bolster dressing, 1 out of 2 studies showed improved rate of revascularization when used over dermal substitutes, and 1 study showed increased rate of re-epithelialization when used over skin graft donor sites. Negative pressure can improve autograft take when used as a bolster dressing. There is limited data to suggest that it may also improve the rate of revascularization of dermal substitutes and promote re-epithelialization of skin graft donor sites. Other uses suggested by studies that did not meet our inclusion criteria include improving vascularity in acute partial-thickness burns and as an integrated dressing for the management of large burns. Further studies are warranted for most clinical applications to establish negative pressure as an effective adjunct in burn wound care. Copyright © 2016 Elsevier Ltd and ISBI. All rights reserved.

Age-Related Variability in Tongue Pressure Patterns for Maximum Isometric and Saliva Swallowing Tasks

PubMed Central

Peladeau-Pigeon, Melanie

2017-01-01

Purpose The ability to generate tongue pressure plays a major role in bolus transport in swallowing. In studies of motor control, stability or variability of movement is a feature that changes with age, disease, task complexity, and perturbation. In this study, we explored whether age and tongue strength influence the stability of the tongue pressure generation pattern during isometric and swallowing tasks in healthy volunteers. Method Tongue pressure data, collected using the Iowa Oral Performance Instrument, were analyzed from 84 participants in sex-balanced and decade age-group strata. Tasks included maximum anterior and posterior isometric pressures and regular-effort saliva swallows. The cyclic spatiotemporal index (cSTI) was used to capture stability (vs. variability) in patterns of pressure generation. Mixed-model repeated measures analyses of covariance were performed separately for each task (anterior and posterior isometric pressures, saliva swallows) with between-participant factors of age group and sex, a within-participant factor of task repetition, and a continuous covariate of tongue strength. Results Neither age group nor sex effects were found. There was no significant relationship between tongue strength and the cSTI on the anterior isometric tongue pressure task (r = −.11). For the posterior isometric tongue pressure task, a significant negative correlation (r = −.395) was found between tongue strength and the cSTI. The opposite pattern of a significant positive correlation (r = .29) between tongue strength and the cSTI was seen for the saliva swallow task. Conclusions Tongue pressure generation patterns appear highly stable across repeated maximum isometric and saliva swallow tasks, despite advancing age. Greater pattern variability is seen with weaker posterior isometric pressures. Overall, saliva swallows had the lowest pressure amplitudes and highest pressure pattern variability as measured by the cSTI. PMID:29114767

[Development of a continuous blood pressure monitoring and recording system].

PubMed

Zhang, Yang; Li, Yong; Gao, Shumei; Song, Yilin

2012-09-01

A small experimental system is constructed with working principle of continuous blood pressure monitoring based on the volume compensation method. The preliminary experimental results show that the system can collect blood pressure signals at the radial artery effectively. The digital PID algorithm can track the variation of blood pressure. And the accuracy of continuous blood pressure detecting achieve the level of same kind of product.

Application of low-pressure negative pressure wound therapy to ischaemic wounds.

PubMed

Kasai, Yoshiaki; Nemoto, Hitoshi; Kimura, Naohiro; Ito, Yoshinori; Sumiya, Noriyoshi

2012-03-01

Negative pressure wound therapy (NPWT) is a useful wound dressing that can be applied to a wide variety of wounds. Patients with ischaemic wounds, however, may experience further necrosis with NPWT at the commonly recommended pressure of -125 mm Hg. We hypothesized that with a suction pressure of -125 mm Hg, tissue pressure will likely occlude most of the capillaries adjacent to the wound edge. Therefore, we treated three patients with ischaemic wounds using low-pressure NPWT at -50 mm Hg. All wounds healed successfully without further necrosis at the wound edge. Crown Copyright © 2011. Published by Elsevier Ltd. All rights reserved.

The effects of altered intrathoracic pressure on resting cerebral blood flow and its response to visual stimulation

PubMed Central

Hayen, Anja; Herigstad, Mari; Kelly, Michael; Okell, Thomas W.; Murphy, Kevin; Wise, Richard G.; Pattinson, Kyle T.S.

2013-01-01

Investigating how intrathoracic pressure changes affect cerebral blood flow (CBF) is important for a clear interpretation of neuroimaging data in patients with abnormal respiratory physiology, intensive care patients receiving mechanical ventilation and in research paradigms that manipulate intrathoracic pressure. Here, we investigated the effect of experimentally increased and decreased intrathoracic pressures upon CBF and the stimulus-evoked CBF response to visual stimulation. Twenty healthy volunteers received intermittent inspiratory and expiratory loads (plus or minus 9 cmH2O for 270 s) and viewed an intermittent 2 Hz flashing checkerboard, while maintaining stable end-tidal CO2. CBF was recorded with transcranial Doppler sonography (TCD) and whole-brain pseudo-continuous arterial spin labeling magnetic resonance imaging (PCASL MRI). Application of inspiratory loading (negative intrathoracic pressure) showed an increase in TCD-measured CBF of 4% and a PCASL-measured increase in grey matter CBF of 5%, but did not alter mean arterial pressure (MAP). Expiratory loading (positive intrathoracic pressure) did not alter CBF, while MAP increased by 3%. Neither loading condition altered the perfusion response to visual stimulation in the primary visual cortex. In both loading conditions localized CBF increases were observed in the somatosensory and motor cortices, and in the cerebellum. Altered intrathoracic pressures, whether induced experimentally, therapeutically or through a disease process, have possible significant effects on CBF and should be considered as a potential systematic confound in the interpretation of perfusion-based neuroimaging data. PMID:23108273

Decreased cardiopulmonary baroreflex sensitivity in Chagas' heart disease.

PubMed

Consolim-Colombo, F M; Filho, J A; Lopes, H F; Sobrinho, C R; Otto, M E; Riccio, G M; Mady, C; Krieger, E M

2000-12-01

No study has been performed on reflexes originating from receptors in the heart that might be involved in the pathological lesions of Chagas' heart disease. Our study was undertaken to analyze the role of cardiopulmonary reflex on cardiovascular control in Chagas' disease. We studied 14 patients with Chagas' disease without heart failure and 12 healthy matched volunteers. Central venous pressure, arterial blood pressure, heart rate, forearm blood flow, and forearm vascular resistance were recorded during deactivation of cardiopulmonary receptors. By reducing central venous pressure by applying -10 and -15 mm Hg of negative pressure to the lower body, we observed (a) a similar decrease of central venous pressure in both groups; (b) a marked increase in forearm vascular resistance in the control group but a blunted increase in the Chagas' group; and (c) no significant changes in blood pressure and heart rate. To analyze cardiopulmonary and arterial receptors, we applied -40 mm Hg of lower-body negative pressure. As a consequence, (a) central venous pressure decreased similarly in both groups; (b) blood pressure was maintained in the control group, whereas in patients with Chagas' disease, a decrease in systolic and mean arterial pressure occurred; (c) heart rate increased in both groups; and (d) forearm vascular resistance increased significantly and similarly in both groups. Unloading of receptors with low levels of lower-body negative pressure did not increase forearm vascular resistance in patients with Chagas' disease, which suggests that the reflex mediated by cardiopulmonary receptors is impaired in patients with Chagas' disease without heart failure. Overall control of circulation appears to be compromised because patients did not maintain blood pressure under high levels of lower-body negative pressure.

Left ventricular function during lower body negative pressure

NASA Technical Reports Server (NTRS)

Ahmad, M.; Blomqvist, C. G.; Mullins, C. B.; Willerson, J. T.

1977-01-01

The response of the human left ventricle to lower body negative pressure (LBNP) and the relation between left ventricular function and hemodynamic response were investigated. Ventricular function curves relating stroke volume to end-diastolic volume were obtained in 12 normal men. Volume data were derived from echocardiographic measurements of left ventricular end-systolic and end-diastolic diameters at rest and during lower body negative pressure (LBNP) at minus 40 mm Hg. End-diastolic volume decreased by 19% and stroke volume by 22%. There were no significant changes in heart rate, arterial blood pressure, or end-systolic volume. Thus, moderate levels of LBNP significantly reduce preload and stroke volume without affecting contractile state. The absence of significant changes in heart rate and arterial blood pressure in the presence of a significant reduction in stroke volume is consistent with an increase in systemic peripheral resistance mediated by low-pressure baroreceptors.

The cerebral hemodynamics of normotensive hypovolemia during lower-body negative pressure

NASA Technical Reports Server (NTRS)

Giller, C. A.; Levine, B. D.; Meyer, Y.; Buckey, J. C.; Lane, L. D.; Borchers, D. J.

1992-01-01

Although severe hypovolemia can lead to hypotension and neurological decline, many patients with neurosurgical disorders experience a significant hypovolemia while autonomic compensatory mechanisms maintain a normal blood pressure. To assess the effects of normotensive hypovolemia upon cerebral hemodynamics, transcranial Doppler ultrasound monitoring of 13 healthy volunteers was performed during graded lower-body negative pressure of up to -50 mm Hg, an accepted laboratory model for reproducing the physiological effects of hypovolemia. Middle cerebral artery flow velocity declined by 16% +/- 4% (mean +/- standard error of the mean) and the ratio between transcranial Doppler ultrasound pulsatility and systemic pulsatility rose 22% +/- 8%, suggesting cerebral small-vessel vasoconstriction in response to the sympathetic activation unmasked by lower-body negative pressure. This vasoconstriction may interfere with the autoregulatory response to a sudden fall in blood pressure, and may explain the common observation of neurological deficit during hypovolemia even with a normal blood pressure.

[Instrumentation support in respiratory kinesiotherapy].

PubMed

Vandevenne, A; Sergysels, R; Ravez, P; Worth, H; De Coster, A

1988-01-01

The points of impact of instrumental support in respiratory physiotherapy are numerous; they concern primarily the pulmonary expansion, bronchial drainage and function of respiratory muscles. The pulmonary expansion may be helped by incitant spirometry and either intermittent or continuous positive pressure respiration, or indirectly by the utilisation of respiration against resistance (expiratory bottles, masks with uni-directional valves and expiratory resistances etc.). These different techniques may be used in the presence of instability of the respiratory units, secondary to an alteration of surfactant or to closure of the small airways induced by a transitory reduction (in the post-operative period) or permanent reduction (such as parietal wall disease of mechanical or neuro-muscular origin) of the functional residual capacity (CRF). If the continuous positive airway pressure (CPAP) seems particularly helpful for the CRF to recover to the pre-operative level it also appears on the contrary as the least efficacious technique to increase trans-pulmonary pressure. The instrumental support for bronchial drainage may theoretically affect the tension activity of the transport (instrumental help in the pulmonary expansion and in hyperventilation), muco-ciliary transport (external parietal vibration or internal vibrations applied to the upper airways), the biphasic flow (expiratory assistance by negative pressure and humidifiers). The function of the respiratory muscles may in certain cases be improved by the use of abdominal pneumatic cuirasses, by hyperventilation exercises in an isocapnoeic milieu or in breathing exercises against an additional inspiratory or expiratory resistance. If the physiological foundation of mechanical support in respiratory education may be frequently identified, the clinical results reported in the literature are often contradictory.

Self-generating oscillating pressure exercise device

NASA Technical Reports Server (NTRS)

Watenpaugh, Donald E. (Inventor)

1994-01-01

An exercise device, especially suitable for zero gravity workouts, has a collapsible chamber which generates negative pressure on the lower portion of a body situated therein. The negative pressure is generated by virtue of leg, hand and shoulder interaction which contracts and expands the chamber about the person and by virtue of air flow regulation by valve action.

Effect of amplitude and duration of impulsive pressure on endothelial permeability in in vitro fluid percussion trauma.

PubMed

Nakadate, Hiromichi; Inuzuka, Koji; Akanuma, Suguru; Kakuta, Akira; Aomura, Shigeru

2014-04-16

Intracranial pressure changes during head impact cause brain injuries such as vasogenic edema and cerebral contusion. However, the influence of impulsive pressure on endothelial function has not yet been fully studied in vitro. In this study, we developed a pressure loading device that produced positive and negative pressures by modifying an in vitro fluid percussion model and examined the effects of the amplitude and duration of the pressures on endothelial permeability. Human umbilical vein endothelial cells were subjected to three types of positive pressure (average amplitude/average duration of 352 kPa/23 ms, 73 kPa/27 ms, and 70 kPa/44 ms) and three types of negative pressure (-72 kPa/41 ms, -67 kPa/104 ms, and -91 kPa/108 ms), and the transendothelial electrical resistance (TEER) was measured between 15 min and 24 h after pressure loading for quantifying the formation of an integral monolayer of endothelial cells. After loading, vascular endothelial- (VE-) cadherin, an endothelium-specific cell-cell adhesion molecule involved in endothelial barrier function, was stained and observed using fluorescence microscopy. The pressure loading device could produce positive pressure pulses with amplitudes of 53-1348 kPa and durations of 9-29.1 ms and negative pressure pulses with amplitudes of -52 - -93 kPa and durations of 42.9-179.5 ms. The impulsive pressure reduced the TEER associated with the change in VE-cadherin localization. Additionally, TEER decreased considerably at 15 min and 6 h post-loading, with these changes being significant in positive pressure with larger amplitude and shorter duration and in all types of negative pressures compared to pre-loading. The changes in intracranial pressure during head impact impair endothelial barrier function by the disruption of the integrity of endothelial cell-cell junctions, and the degree of increase in endothelial permeability depends on the amplitude, duration, and direction (compressive and tensile) of the impulsive pressure.

Management of patients infected with airborne-spread diseases: an algorithm for infection control professionals.

PubMed

Rebmann, Terri

2005-12-01

Many US hospitals lack the capacity to house safely a surge of potentially infectious patients, increasing the risk of secondary transmission. Respiratory protection and negative-pressure rooms are needed to prevent transmission of airborne-spread diseases, but US hospitals lack available and/or properly functioning negative-pressure rooms. Creating new rooms or retrofitting existing facilities is time-consuming and expensive. Safe methods of managing patients with airborne-spread diseases and establishing temporary negative-pressure and/or protective environments were determined by a literature review. Relevant data were analyzed and synthesized to generate a response algorithm. Ideal patient management and placement guidelines, including instructions for choosing respiratory protection and creating temporary negative-pressure or other protective environments, were delineated. Findings were summarized in a treatment algorithm. The threat of bioterrorism and emerging infections increases health care's need for negative-pressure and/or protective environments. The algorithm outlines appropriate response steps to decrease transmission risk until an ideal protective environment can be utilized. Using this algorithm will prepare infection control professionals to respond more effectively during a surge of potentially infectious patients following a bioterrorism attack or emerging infectious disease outbreak.

Measurement and Modeling of Acoustic Fields in a Gel Phantom at High Intensities

NASA Astrophysics Data System (ADS)

Canney, Michael S.; Bailey, Michael R.; Khokhlova, Vera A.; Crum, Lawrence A.

2006-05-01

The goal of this work was to compare measured and numerically predicted HIFU pressure waveforms in water and a tissue-mimicking phantom. Waveforms were measured at the focus of a 2-MHz HIFU transducer with a fiber optic hydrophone. The transducer was operated with acoustic powers ranging from 2W to 300W. A KZK-type equation was used for modeling the experimental conditions. Strongly asymmetric nonlinear waves with peak positive pressure up to 80 MPa and peak negative pressure up to 20 MPa were measured in water, while waves up to 50 MPa peak positive pressure and 15 MPa peak negative pressure were measured in tissue phantoms. The values of peak negative pressure corresponded well with numerical simulations and were significantly smaller than predicted by linear extrapolation from low-level measurements. The values of peak positive pressures differed only at high levels of excitation where bandwidth limitations of the hydrophone failed to fully capture the predicted sharp shock fronts.

The potential for health risks from intrusion of contaminants into the distribution system from pressure transients.

PubMed

LeChevallier, Mark W; Gullick, Richard W; Karim, Mohammad R; Friedman, Melinda; Funk, James E

2003-03-01

The potential for public health risks associated with intrusion of contaminants into water supply distribution systems resulting from transient low or negative pressures is assessed. It is shown that transient pressure events occur in distribution systems; that during these negative pressure events pipeline leaks provide a potential portal for entry of groundwater into treated drinking water; and that faecal indicators and culturable human viruses are present in the soil and water exterior to the distribution system. To date, all observed negative pressure events have been related to power outages or other pump shutdowns. Although there are insufficient data to indicate whether pressure transients are a substantial source of risk to water quality in the distribution system, mitigation techniques can be implemented, principally the maintenance of an effective disinfectant residual throughout the distribution system, leak control, redesign of air relief venting, and more rigorous application of existing engineering standards. Use of high-speed pressure data loggers and surge modelling may have some merit, but more research is needed.

Within-Breath Control of Genioglossal Muscle Activation in Humans: Effect of Sleep-Wake State

PubMed Central

Fogel, Robert B; Trinder, John; Malhotra, Atul; Stanchina, Michael; Edwards, Jill K; Schory, Karen E; White, David P

2003-01-01

Pharyngeal dilator muscles are clearly important in the pathogenesis of obstructive sleep apnoea syndrome. Substantial data support the role of a local negative pressure reflex in modifying genioglossal activation across inspiration during wakefulness. Using a model of passive negative pressure ventilation, we have previously reported a tight relationship between varying intrapharyngeal negative pressures and genioglossal muscle activation (GGEMG) during wakefulness. In this study, we used this model to examine the slope of the relationship between epiglottic pressure (Pepi) and GGEMG, during stable NREM sleep and the transition from wakefulness to sleep. We found that there was a constant relationship between negative epiglottic pressure and GGEMG during both basal breathing (BB) and negative pressure ventilation (NPV) during wakefulness (slope GGEMG/Pepi 1.86 ± 0.3 vs. 1.79 ± 0.3 arbitrary units (a.u.) cmH2O−1). However, while this relationship remained stable during NREM sleep during BB, it was markedly reduced during NPV during sleep (2.27 ± 0.4 vs. 0.58 ± 0.1 a.u. cmH2O−1). This was associated with a markedly higher pharyngeal airflow resistance during sleep during NPV. At the transition from wakefulness to sleep there was also a greater reduction in peak GGEMG seen during NPV than during BB. These data suggest that while the negative pressure reflex is able to maintain GGEMG during passive NPV during wakefulness, this reflex is unable to do so during sleep. The loss of this protective mechanism during sleep suggests that an airway dependent upon such mechanisms (as in the patient with sleep apnoea) will be prone to collapse during sleep. PMID:12807995

Continuous electroencephalogram monitoring in the intensive care unit.

PubMed

Friedman, Daniel; Claassen, Jan; Hirsch, Lawrence J

2009-08-01

Because of recent technical advances, it is now possible to record and monitor the continuous digital electroencephalogram (EEG) of many critically ill patients simultaneously. Continuous EEG monitoring (cEEG) provides dynamic information about brain function that permits early detection of changes in neurologic status, which is especially useful when the clinical examination is limited. Nonconvulsive seizures are common in comatose critically ill patients and can have multiple negative effects on the injured brain. The majority of seizures in these patients cannot be detected without cEEG. cEEG monitoring is most commonly used to detect and guide treatment of nonconvulsive seizures, including after convulsive status epilepticus. In addition, cEEG is used to guide management of pharmacological coma for treatment of increased intracranial pressure. An emerging application for cEEG is to detect new or worsening brain ischemia in patients at high risk, especially those with subarachnoid hemorrhage. Improving quantitative EEG software is helping to make it feasible for cEEG (using full scalp coverage) to provide continuous information about changes in brain function in real time at the bedside and to alert clinicians to any acute brain event, including seizures, ischemia, increasing intracranial pressure, hemorrhage, and even systemic abnormalities affecting the brain, such as hypoxia, hypotension, acidosis, and others. Monitoring using only a few electrodes or using full scalp coverage, but without expert review of the raw EEG, must be done with extreme caution as false positives and false negatives are common. Intracranial EEG recording is being performed in a few centers to better detect seizures, ischemia, and peri-injury depolarizations, all of which may contribute to secondary injury. When cEEG is combined with individualized, physiologically driven decision making via multimodality brain monitoring, intensivists can identify when the brain is at risk for injury or when neuronal injury is already occurring and intervene before there is permanent damage. The exact role and cost-effectiveness of cEEG at the current time remains unclear, but we believe it has significant potential to improve neurologic outcomes in a variety of settings.

The burden of the 'RA RA' positive: survivors' and hospice patients' reflections on maintaining a positive attitude to serious illness.

PubMed

McGrath, Pam

2004-01-01

This article seeks to make a contribution to fostering work on the neglected area of research about how individuals maintain a positive outlook during their confrontation with serious illness. Insights are presented from both haematology survivors and hospice patients about the factors that hinder and facilitate their capacity to 'be positive'. Open-ended interviews with 14 hospice patients and 12 haematology survivors on their construction of meaning in the face of serious illness were audio-recorded, transcribed verbatim and thematically analysed. The findings on the topic of maintaining a positive outlook are presented in this article. Although the participants affirmed the value of a positive perspective on their illness experience, they were critical of unwanted pressure from others to be positive: a phenomenon they called the 'RA RA' positive. Such pressure interfered with the natural process of continually having to re-negotiate a positive outlook through exploring the fullness of feeling, both positive and negative. The participants indicated that at times of relapse or worsening physical condition they had to cycle through a process of despair/negativity and re-adjustment before they were able to find the positive. The process could not be rushed and required freedom from an imposed pressure to be positive. The essential message is that a positive outlook cannot be imposed but requires a nurturing orientation that allows the expression of a full range of feelings in a supportive environment.

Correlation between lumbo-ventricular perfusion and MRI-CSF flow studies in idiopathic normal pressure hydrocephalus.

PubMed

Hakim, R; Black, P M

1998-01-01

After the initial description of normal pressure hydrocephalus (NPH) and its clinical triad, there has been a continuous interest from clinicians and researchers to set different diagnostic criteria that would make the selection of candidates for shunt surgery easier and more precise. A preliminary group of 12 patients was given a diagnosis of idiopathic normal pressure hydrocephalus by clinical and radiologic criteria. Each patient underwent two different tests: a magnetic resonance imaging-cerebrospinal fluid (MRI-CSF) flow study and a lumbo-ventricular perfusion test. The purpose was to compare the correlation of the results obtained with these tests and the clinical results obtained after CSF diversion. Eleven patients were given shunts and one was managed with lumbar punctures. One year after treatment, 10 of the 12 patients had improved with good results. The MRI-CSF flow studies were reliable in six patients; there were five false negatives and one false positive. The lumbo-ventricular perfusion test showed reliability in nine patients; there were two false negatives and one false positive. In only three patients were the results of both of these tests in accordance with the outcome. Even though there are few patients in this study so far, the data suggests that at the present time the most predictive guides for the diagnosis of NPH and its outcome after shunting are the clinical criteria and the radiological findings in computed tomography (CT) and/or MRI rather than lumbo-ventricular perfusion and CSF flow studies.

[Clinical factors relating to the arterial elastic function measured by PWV, C1/C2 and AI in hypertensive patients].

PubMed

Cai, Kai-yu; Zhang, Wei-zhong; Qiu, Hui-li; Wu, Mei-zhi

2007-03-01

To analyze the clinical factors relating to arterial elastic function measured with pulse wave velocity (PWV), large and small arterial elastic indexes (C(1) and C(2)) and augmentation index (AI) in hypertensive patients. A total of 2176 hypertensive patients were enrolled and divided into three groups: Elastic function was measured in 1100 subjects by (PWV), in 647 subjects by C(1) and C(2) and in 429 by AI. PWV was positively correlated with age, systolic pressure, pulse pressure and negatively correlated with body height and weights (all P < 0.05). C(1) and C(2) values were higher in male than that in female patients (P < 0.01) and negatively correlated with age, systolic pressure, pulse pressure and heart rate while positively correlated with body height, weight and body mass index. In hypercholesterolemia patients (n = 168), C(1) and C(2) were negatively correlated with serum cholesterol level (P < 0.05). AI value was higher in female than that in male patients (P < 0.01) and positively correlated with age, systolic pressure, diastolic pressure, pulse pressure while negatively correlated with body height, weight and heart rate. Age, systolic and pulse pressure as well as body height and weights are the main factors correlated to arterial elastic function measured by PWV, C(1) and C(2) and AI.

Negative pressure wound therapy-assisted dermatotraction for the closure of large open wounds in a patient with non-clostridial gas gangrene.

PubMed

Ishida, Kenichiro; Noborio, Mitsuhiro; Nishimura, Tetsuro; Ieki, Yohei; Shimahara, Yumiko; Sogabe, Taku; Ehara, Naoki; Saoyama, Yuki; Sadamitsu, Daikai

2016-04-01

A 53-year-old woman developed septic shock associated with non-clostridial gas gangrene. She presented to the emergency department with two large open wounds on both thighs and in her sacral region. Non-enhanced computed tomography showed air density in contact with the right iliopsoas, which extended to the posterior compartment of the thigh. We made repeated efforts at surgical debridement of the wound with resection of necrotic tissues. Using negative pressure wound therapy-assisted dermatotraction, the pus pockets and the wound dehiscence decreased in size. Using this method we were successful in achieving delayed closure without skin grafts. Negative pressure wound therapy can be an effective treatment for large and infected open contoured wounds. Negative pressure wound therapy-assisted dermatotraction might be beneficial for poorly healing, large, open wounds in patients in poor condition and with insufficient reserve to tolerate reconstructive surgery.

Respiratory Distress

NASA Technical Reports Server (NTRS)

1976-01-01

The University of Miami School of Medicine asked the Research Triangle Institute for assistance in improvising the negative pressure technique to relieve respiratory distress in infants. Marshall Space Flight Center and Johnson Space Center engineers adapted this idea to the lower-body negative-pressure system seals used during the Skylab missions. Some 20,000 babies succumb to respiratory distress in the U.S. each year, a condition in which lungs progressively lose their ability to oxygenate blood. Both positive and negative pressure techniques have been used - the first to force air into lungs, the second to keep infant's lungs expanded. Negative pressure around chest helps the baby expand his lungs and maintain proper volume of air. If doctors can keep the infant alive for four days, the missing substance in the lungs will usually form in sufficient quantity to permit normal breathing. The Skylab chamber and its leakproof seals were adapted for medical use.

Evaluation program for secondary spacecraft cells. Initial evaluation tests of General Electric Company standard and teflonated negative electrode 20.0 ampere-hour, nickel-cadmium spacecraft cells with auxiliary electrodes

NASA Technical Reports Server (NTRS)

1974-01-01

The standard plate cells exhibited higher average end-of-charge (EOC) voltages than the cells with teflonated negative plates; they also delivered a higher capacity output in ampere hours following these charges. All the cells reached a pressure of 20 psia before reaching the voltage limit of 1.550 volts during the pressure versus capacity test. The average ampere hours in and voltages at this pressure were 33.6 and 1.505 volts respectively for the teflonated negative plate cells and 35.5 and 1.523 volts for the standard plate cells. All cells exhibited pressure decay in the range of 1 to 7 psia during the last 30 minutes of the 1-hour open circuit stand. Average capacity out for the teflonated and standard negative plate cells was 29.4 and 29.9 ampere hours respectively.

Computational Models Reveal a Passive Mechanism for Cell Migration in the Crypt

PubMed Central

Dunn, Sara-Jane; Näthke, Inke S.; Osborne, James M.

2013-01-01

Cell migration in the intestinal crypt is essential for the regular renewal of the epithelium, and the continued upward movement of cells is a key characteristic of healthy crypt dynamics. However, the driving force behind this migration is unknown. Possibilities include mitotic pressure, active movement driven by motility cues, or negative pressure arising from cell loss at the crypt collar. It is possible that a combination of factors together coordinate migration. Here, three different computational models are used to provide insight into the mechanisms that underpin cell movement in the crypt, by examining the consequence of eliminating cell division on cell movement. Computational simulations agree with existing experimental results, confirming that migration can continue in the absence of mitosis. Importantly, however, simulations allow us to infer mechanisms that are sufficient to generate cell movement, which is not possible through experimental observation alone. The results produced by the three models agree and suggest that cell loss due to apoptosis and extrusion at the crypt collar relieves cell compression below, allowing cells to expand and move upwards. This finding suggests that future experiments should focus on the role of apoptosis and cell extrusion in controlling cell migration in the crypt. PMID:24260407

Stress and Negative Relationship Quality among Older Couples: Implications for Blood Pressure.

PubMed

Birditt, Kira S; Newton, Nicky J; Cranford, James A; Ryan, Lindsay H

2016-09-01

The cardiovascular system may represent a significant pathway by which marriage and stress influence health, but research has focused on married individuals cross-sectionally. This study examined associations among chronic stress, negative spousal relationship quality, and systolic blood pressure over time among middle-aged and older husbands and wives. Participants were from the nationally representative longitudinal Health and Retirement Study. A total of 1,356 (N = 2,712) married and cohabitating couples completed psychosocial and biomeasure assessments in waves 2006 and 2010. Analyses examined whether Wave 1 (2006) relationship quality and stress were associated with changes in blood pressure over time. The effects of stress and negative relationship quality were dyadic and varied by gender. Husbands had increased blood pressure when wives reported greater stress, and this link was exacerbated by negative spousal relationship quality. Negative relationship quality predicted increased blood pressure when both members of the couple reported negative quality relations. Findings support the dyadic biopsychosocial model of marriage and health indicating: (a) stress and relationship quality directly effect the cardiovascular system, (b) relationship quality moderates the effect of stress, and (c) the dyad rather than only the individual should be considered when examining marriage and health. © The Author 2015. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Barometric pressure forcing on radon-222 and temperature in fumarolic gases: a tool to describe flow-rate dynamics

NASA Astrophysics Data System (ADS)

Richon, P.; Salaun, A.; Boudon, G.; Villemant, B.; Crispi, O.; Sabroux, J.

2010-12-01

We propose two conceptual models for the dynamics of fumarolic gases, during their ascent through the volcano plumbing, based on radon-222 and temperature data collected on fumaroles of La Soufrière volcano (Guadeloupe,FWI) together with local barometric pressure, and on a new interpretation of older data collected on Merapi volcano (1), Indonesia. All these in-situ measurements prove that the diurnal (24h, S1 barometric wave) and semidiurnal (12h, S2 barometric wave) variations in radon concentration are clearly observable, and positively or negatively correlated with barometric pressure variation. Two models are used to interpret this correlation. The first model, called “Accumulation mode”, is characterized by an initial and negligible deep radon-222 source and by a major contribution of radon-222 from conduit walls and connected fractures (emanation and exhalation mechanisms) during the gas ascent through the fumarolic system. This model is substantiated by a positive correlation between radon and pressure in the Merapi fumaroles. The second model, or “Decay mode”, is exemplified by a negative correlation between radon and pressure as measured in fumaroles at La Soufrière volcano. It is characterized by radioactive decay of a strong initial radon-222 source generated by a deeper reservoir (hydrothermal system or magmatic chamber) whereas contribution by conduit walls and connected fractures to the total radon-222 activity in the fumarole is comparatively minor during the transit time of the gas. In these two modes, it is possible to infer that, for transit times longer than ca. 21 days, the barometric pressure does not modulate the radon signal. Thus, the simultaneous monitoring of radon-222, temperature and barometric pressure provides a precise fumarole flowmeter. In addition, it is a tool to decipher shallow versus deep feeding of volcanic fumaroles that should prove useful for volcano monitoring. (1)Zimmer, M. & Erzinger, J. Continuous H2O, CO2, 222Rn and temperature measurements on Merapi Volcano, Indonesia. J. Volcanol. Geoth. Res. 125, 25-38 (2003).

Normal values for high-resolution anorectal manometry in healthy women: effects of age and significance of rectoanal gradient.

PubMed

Noelting, Jessica; Ratuapli, Shiva K; Bharucha, Adil E; Harvey, Doris M; Ravi, Karthik; Zinsmeister, Alan R

2012-10-01

High-resolution manometry (HRM) is used to measure anal pressures in clinical practice but normal values have not been available. Although rectal evacuation is assessed by the rectoanal gradient during simulated evacuation, there is substantial overlap between healthy people and defecatory disorders, and the effects of age are unknown. We evaluated the effects of age on anorectal pressures and rectal balloon expulsion in healthy women. Anorectal pressures (HRM), rectal sensation, and balloon expulsion time (BET) were evaluated in 62 asymptomatic women ranging in age from 21 to 80 years (median age 44 years) without risk factors for anorectal trauma. In total, 30 women were aged <50 years. Age is associated with lower (r=-0.47, P<0.01) anal resting (63 (5) (≥50 years), 88 (3) (<50 years), mean (s.e.m.)) but not squeeze pressures; higher rectal pressure and rectoanal gradient during simulated evacuation (r=0.3, P<0.05); and a shorter (r=-0.4, P<0.01) rectal BET (17 (9) s (≥50 years) vs. 31 (10) s (<50 years)). Only 5 women had a prolonged (>60 s) rectal BET but 52 had higher anal than rectal pressures (i.e., negative gradient) during simulated evacuation. The gradient was more negative in younger (-41 (6) mm Hg) than older (-12 (6) mm Hg) women and negatively (r=-0.51, P<0.0001) correlated with rectal BET but only explained 16% of the variation in rectal BET. These observations provide normal values for anorectal pressures by HRM. Increasing age is associated with lower anal resting pressure, a more positive rectoanal gradient during simulated evacuation, and a shorter BET in asymptomatic women. Although the rectoanal gradient is negatively correlated with rectal BET, this gradient is negative even in a majority of asymptomatic women, undermining the utility of a negative gradient for diagnosing defecatory disorders by HRM.

Evaluation of the Boussignac Cardiac arrest device (B-card) during cardiopulmonary resuscitation in an animal model.

PubMed

Moore, Johanna C; Lamhaut, Lionel; Hutin, Alice; Dodd, Kenneth W; Robinson, Aaron E; Lick, Michael C; Salverda, Bayert J; Hinke, Mason B; Labarere, José; Debaty, Guillaume; Segal, Nicolas

2017-10-01

The purpose of this study was to examine continuous oxygen insufflation (COI) in a swine model of cardiac arrest. The primary hypothesis was COI during standard CPR (S-CPR) should result in higher intrathoracic pressure (ITP) during chest compression and lower ITP during decompression versus S-CPR alone. These changes with COI were hypothesized to improve hemodynamics. The second hypothesis was that changes in ITP with S-CPR+COI would result in superior hemodynamics compared with active compression decompression (ACD) + impedance threshold device (ITD) CPR, as this method primarily lowers ITP during chest decompression. After 6min of untreated ventricular fibrillation, S-CPR was initiated in 8 female swine for 4min, then 3min of S-CPR+COI, then 3min of ACD+ITD CPR, then 3min of S-CPR+COI. ITP and hemodynamics were continuously monitored. During S-CPR+COI, ITP was always positive during the CPR compression and decompression phases. ITP compression values with S-CPR+COI versus S-CPR alone were 5.5±3 versus 0.2±2 (p<0.001) and decompression values were 2.8±2 versus -1.3±2 (p<0.001), respectively. With S-CPR+COI versus ACD+ITD the ITP compression values were 5.5±3 versus 1.5±2 (p<0.01) and decompression values were 2.8±2 versus -4.7±3 (p<0.001), respectively. COI during S-CPR created a continuous positive pressure in the airway during both the compression and decompression phase of CPR. At no point in time did COI generate a negative intrathoracic pressures during CPR in this swine model of cardiac arrest. Copyright © 2017 Elsevier B.V. All rights reserved.

A brief clinical case of monitoring of oxygenator performance and patient-machine interdependency during prolonged veno-venous extracorporeal membrane oxygenation.

PubMed

Belliato, Mirko; Degani, Antonella; Buffa, Antonino; Sciutti, Fabio; Pagani, Michele; Pellegrini, Carlo; Iotti, Giorgio Antonio

2017-10-01

Monitoring veno-venous extracorporeal membrane oxygenation (vvECMO) during 76 days of continuous support in a 42-years old patient with end-stage pulmonary disease, listed for double-lung transplantation. Applying a new monitor (Landing ® , Eurosets, Medolla, Italy) and describing how measured and calculated parameters can be used to understand the variable interdependency between artificial membrane lung (ML) and patient native lung (NL). During vvECMO, in order to understand how the respiratory function is shared between ML and NL, ideally we should obtain data about oxygen transfer and CO 2 removal, both by ML and NL. Measurements for NL can be made on the mechanical ventilator. Measurements for ML are typically made from gas analysis on blood samples drawn from the ECMO system before and after the oxygenator, and therefore are non-continuous. Differently, the Landing monitor provides a continuous measurement of the oxygen transfer from the ML, combined with hemoglobin level, saturation of drained blood and saturation of reinfused blood. Moreover, the Landing monitor provides hemodynamics data about circulation through the ECMO system, with blood flow, pre-oxygenator pressure and post-oxygenator pressure. Of note, measurements include the drain negative pressure, whose monitoring may be particularly useful to prevent hemolysis. Real-time monitoring of vvECMO provides data helpful to understand the complex picture of a patient with severely damaged lungs on one side and an artificial lung on the other side. Data from vvECMO monitoring may help to adapt the settings of both mechanical ventilator and vvECMO. Data about oxygen transfer by the oxygenator are important to evaluate the performance of the device and may help to avoid unnecessary replacements, thus reducing risks and costs.

Long-term Response of Cerebrospinal Fluid Pressure in Patients with Idiopathic Intracranial Hypertension - A Prospective Observational Study.

PubMed

Gafoor, V Abdul; Smita, B; Jose, James

2017-01-01

Idiopathic intracranial hypertension (IIH) is increased intracranial pressure (ICP) with normal cerebrospinal fluid (CSF) contents, in the absence of an intracranial mass, hydrocephalus, or other identifiable causes. The current knowledge of the treatment outcome of IIH is limited, and the data on the natural history of this entity are scant. The objective of the study is to study the treatment response of IIH by serially measuring the CSF opening pressure and to delineate the factors influencing the same. A prospective observational study in a cohort of fifty patients with IIH in whom CSF opening pressure was serially measured at pre-specified intervals. The mean CSF opening pressure at baseline was 302.4 ± 51.69 mm of H 2 O (range: 220-410). Even though a higher body mass index (BMI) showed a trend toward a higher CSF opening pressure, the association was not significant ( P = 0.168). However, the age of the patient had a significant negative correlation with the CSF pressure ( P = 0.006). The maximum reduction in CSF pressure occurred in the first 3 months of treatment, and thereafter it plateaued. Remission was attained in 12 (24%) patients. BMI had the strongest association with remission ( P = 0.001). In patients with IIH, treatment response is strongly related to BMI. However, patients with normal BMI are also shown to relapse and hence should have continuous, long-term follow-up. The reduction in CSF pressure attained in the first 3 months could reflect the long-term response to treatment.

Suppression effects of negative pressure on the proliferation and metastasis in human pancreatic cancer cells.

PubMed

Yang, Xiujiang; Sun, Bo; Zhu, Haihang; Jiang, Ziting

2015-01-01

The aim was to explore the effect of negative pressure on the proliferation and metastasis of human pancreatic cancer SW1990 cells. Three groups were conducted in the work: normal control group (NC group, 0 mm Hg), low negative pressure group (LN group, -300 mm Hg), and high negative pressure group (HN group, -600 mm Hg). Cell morphological assay was conducted using an inverted Nikon TE2000-S microscope. Cell viability was assayed using cell counting kit-8 solution. Cell apoptosis was evaluated with flow cytometry. Cell migration was investigated using transwell assay. Compared to LN and HN groups, SW1990 cells in NC group grew quite well, showing a higher density. The NC group represented the highest cell viability. The HN group represented the lowest cell viability, which was lower than that of the LN group (P < 0.01). The apoptosis rate in NC group, LN group and HN group was 1.91% ± 0.13%, 2.31% ± 0.06% and 15.22% ± 0.81%, respectively (P < 0.05). The average number of migration cells in NC group was 53.60 ± 4.14 (× 200), which was decreased to 18.93 ± 3.67 and 11.07 ± 3.01 in LN group and HN group, respectively (P < 0.01). The negative pressure shows suppression effects on the proliferation and metastasis of human pancreatic cancer SW1990 cells. It is indicated that negative pressure may be involved in the development of human pancreatic cancer by influencing cell biological characteristics.

Extubation success in premature infants with respiratory distress syndrome treated with bi-level nasal continuous positive airway pressure versus nasal intermittent positive pressure ventilation.

PubMed

Thomas, Patricia E; LeFlore, Judy

2013-01-01

Infants born prematurely with respiratory distress syndrome are at high risk for complications from mechanical ventilation. Strategies are needed to minimize their days on the ventilator. The purpose of this study was to compare extubation success rates in infants treated with 2 different types of continuous positive airway pressure devices. A retrospective cohort study design was used. Data were retrieved from electronic medical records for patients in a large, metropolitan, level III neonatal intensive care unit. A sample of 194 premature infants with respiratory distress syndrome was selected, 124 of whom were treated with nasal intermittent positive pressure ventilation and 70 with bi-level variable flow nasal continuous positive airway pressure (bi-level nasal continuous positive airway pressure). Infants in both groups had high extubation success rates (79% of nasal intermittent positive pressure ventilation group and 77% of bi-level nasal continuous positive airway pressure group). Although infants in the bi-level nasal continuous positive airway pressure group were extubated sooner, there was no difference in duration of oxygen therapy between the 2 groups. Promoting early extubation and extubation success is a vital strategy to reduce complications of mechanical ventilation that adversely affect premature infants with respiratory distress syndrome.

Numerical study of a confocal ultrasonic setup for creation of cavitation

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

Lafond, Maxime, E-mail: maxime.lafond@inserm.fr; Chavrier, Françoise; Prieur, Fabrice

2015-10-28

Acoustic cavitation is used for various therapeutic applications such as local enhancement of drug delivery, histotripsy or hyperthermia. One of the utmost important parameter for cavitation creation is the rarefaction pressure. The typical magnitude of the rarefaction pressure required to initiate cavitation from gas dissolved in tissue is beyond the range of the megapascal. Because nonlinear effects need to be taken into account, a numerical simulator based on the Westervelt equation was used to study the pressure waveform and the acoustic field generated by a setup for creation of cavitation consisting of two high intensity focused ultrasound transducers mounted confocally.more » At constant acoustic power, simulations with only one and both transducers from the confocal setup showed that the distortion of the pressure waveform due to the combined effects of nonlinearity and diffraction is less pronounced when both confocal transducers are used. Consequently, the confocal setup generates a greater peak negative pressure at focus which is more favorable for cavitation initiation. Comparison between the confocal setup and a single transducer with the same total emitting surface puts in evidence the role of the spatial separation of the two beams. Furthermore, it has been previously shown that the location of the peak negative pressure created by a single transducer shifts from focus towards the transducers in the presence of nonlinear effects. The simulator was used to study a configuration where the acoustical axes of transducers intersect on the peak negative pressure instead of the geometrical focus. For a representative confocal setup, namely moderate nonlinear effects, a 2% increase of the peak negative pressure and 8% decrease of the peak positive pressure resulted from this configuration. These differences tend to increase by increasing nonlinear effects. Although the optimal position of the transducers varies with the nonlinear regimen, the intersection point remains the location of the peak negative pressure in any case. Thus, unlike the location of the peak negative pressure for a single transducer can shift by a few millimeters, the focal point of a confocal device is independent of the power. This point is particularly important for therapeutic applications, frequently requiring high spatial accuracy. An experiment conducted shows that cavitation creation can be achieved easier with confocal ultrasound.« less

Hubble and the Language of Images

NASA Astrophysics Data System (ADS)

Levay, Z. G.

2005-12-01

Images released from the Hubble Space Telescope have been very highly regarded by the astronomy-attentive public for at least a decade. Due in large part to these images, Hubble has become an iconic figure, even among the general public. This iconic status is both a boon and a burden for those who produce the stream of images fl owing from this telescope. While the benefits of attention are fairly obvious, the negative aspects are less visible. One of the most persistent challenges is the need to continue to deliver images that "top" those released before. In part this can be accomplished because of Hubble's upgraded instrumentation. But it can also be a source of pressure that could, if left unchecked, erode ethical boundaries in our communication with the public. These pressures are magnified in an atmosphere of uncertainty with regard to the future of the mission.

Pressurized tundish for controlling a continuous flow of molten metal

DOEpatents

Lewis, T.W.; Hamill, P.E. Jr.; Ozgu, M.R.; Padfield, R.C.; Rego, D.N.; Brita, G.P.

1990-07-24

A pressurized tundish for controlling a continuous flow of molten metal is characterized by having a pair of principal compartments, one being essentially unpressurized and receiving molten metal introduced thereto, and the other being adapted for maintaining a controlled gaseous pressure over the surface of the fluid metal therein, whereby, by controlling the pressure within the pressurized chamber, metal exiting from the tundish is made to flow continually and at a controlled rate. 1 fig.

Negative Suction Drain Through a Mini Periareolar Incision for the Treatment of Lactational Breast Abscess Shortens Hospital Stay and Increases Breastfeeding Rates.

PubMed

Wei, Jinli; Zhang, Jiaxin; Fu, Deyuan

2016-06-01

Although breast abscess is a serious uncommon complication of mastitis with high morbidity rate, there is a lack of high-quality randomized trial to demonstrate the best treatments. We reported a novel way of applying negative suction drain through a mini periareolar incision. We retrospectively analyzed and compared the clinical characteristics of 62 patients with lactational breast abscess in our department from August 2012 to April 2015. Thirty-two patients went through traditional incision and drainage (Group A) and 30 patients were placed on negative suction drain through mini periareolar incision (Group B). There is no significant difference between the two groups in terms of age, white blood cell (WBC) count, size of the abscess cavity, and positive rate of Staphylococcus aureus (SA) or methicillin-resistant Staphylococcus aureus (MRSA). Patients in Group B had a shorter hospitalized stay (p = 0.003) and had a higher rate of continuation of breastfeeding (p < 0.005). Applying drain with negative suction pressure through a mini periareolar incision is an effective modality for treating lactational breast abscess and maintaining breastfeeding.

Chronic antihypertensive treatment improves pulse pressure but not large artery mechanics in a mouse model of congenital vascular stiffness

PubMed Central

Halabi, Carmen M.; Broekelmann, Thomas J.; Knutsen, Russell H.; Ye, Li; Mecham, Robert P.

2015-01-01

Increased arterial stiffness is a common characteristic of humans with Williams-Beuren syndrome and mouse models of elastin insufficiency. Arterial stiffness is associated with multiple negative cardiovascular outcomes, including myocardial infarction, stroke, and sudden death. Therefore, identifying therapeutic interventions that improve arterial stiffness in response to changes in elastin levels is of vital importance. The goal of this study was to determine the effect of chronic pharmacologic therapy with different classes of antihypertensive medications on arterial stiffness in elastin insufficiency. Elastin-insufficient mice 4–6 wk of age and wild-type littermates were subcutaneously implanted with osmotic micropumps delivering a continuous dose of one of the following: vehicle, losartan, nicardipine, or propranolol for 8 wk. At the end of treatment period, arterial blood pressure and large artery compliance and remodeling were assessed. Our results show that losartan and nicardipine treatment lowered blood pressure and pulse pressure in elastin-insufficient mice. Elastin and collagen content of abdominal aortas as well as ascending aorta and carotid artery biomechanics were not affected by any of the drug treatments in either genotype. By reducing pulse pressure and shifting the working pressure range of an artery to a more compliant region of the pressure-diameter curve, antihypertensive medications may mitigate the consequences of arterial stiffness, an effect that is drug class independent. These data emphasize the importance of early recognition and long-term management of hypertension in Williams-Beuren syndrome and elastin insufficiency. PMID:26232234

Method and apparatus for simulating gravitational forces on a living organism

NASA Technical Reports Server (NTRS)

Thornton, W. E. (Inventor)

1983-01-01

A method and apparatus for simulating gravitational forces on a living organism wherein a series of negative pressures are externally applied to successive length-wise sections of a lower limb of the organism. The pressures decreasing progressively with distance of said limb sections from the heart of the organism. A casing defines a chamber adapted to contain the limb of the organism and is rigidified to resist collapse upon the application of negative pressures to the interior of the chamber. Seals extend inwardly from the casing for effective engagement with the limb of the organism and, in cooperation with the limb, subdivide the chamber into a plurality of compartments each in negative pressure communicating relation with the limb.

Negative pressure wound therapy and external fixation device: a simple way to seal the dressing.

PubMed

Bulla, Antonio; Farace, Francesco; Uzel, André-Pierre; Casoli, Vincent

2014-07-01

Negative pressure therapy is widely applied to treat lower limb trauma. However, sealing a negative pressure dressing in the presence of an external fixation device may be difficult and time consuming. Therefore, screws, pins, wires, etc, may preclude the vacuum, preventing the plastic drape to perfectly adhere to the foam. To maintain the vacuum, we tried to prevent air leaking around the screws putting bone wax at the junction between the pins and the plastic drape. This solution, in our hands, avoids air leakage and helps maintain vacuum in a fast and inexpensive way.

The use of negative pressure in critical necrotizing fasciitis treatment: a case presentation.

PubMed

Ge, Kui; Xu, Bing; Wu, Jia-Jun; Wu, Minjie; Lu, Shuliang; Xie, Ting

2014-09-01

Surgery complemented by antibiotics forms the backbone of the successful management of necrotizing fasciitis. But it will be very difficult to clear away extensive necrotizing tissue thoroughly in critically ill patients when their vital signs are unstable. The authors report the case of a 33-year-old woman who had extensive necrotizing fasciitis of the right lower limb with septic shock. The patient was severely anemic and malnutrition and had been given conservative debridement at bedside, that is, only detached necrotizing tissues was taken away while some other necrotizing tissue still remained, so that the skin tissue within the same area could be saved as much as possible. After debridement, negative pressure was applied at 125 mm Hg. Broad-spectrum antibiotics and effective supplementation were also complemented, thus controlling the septic shock. All necrotizing tissues were detached, and the sparing vital skin on necrotizing fascia was preserved successfully after negative pressure treatment. The patient was finally saved. In conclusion, negative pressure treatment may help diminish toxin absorbance, detach gangrene tissue, and preserve sparing vital tissue. This case suggests the value of combined use of negative pressure therapy and conservative debridement in critically ill patients with extensive necrotizing fasciitis. © The Author(s) 2014.

Fabrication of Artificial Leaf to Develop Fluid Pump Driven by Surface Tension and Evaporation

NASA Astrophysics Data System (ADS)

Lee, Minki; Lim, Hosub; Lee, Jinkee

2017-11-01

Plants transport water from roots to leaves via xylem through transpiration, which is an evaporation process that occurs at the leaves. During transpiration, negative pressure can be generated by the porous structure of mesophyll cells in the leaves. Here, an artificial leaf mimicking structure using hydrogel, which has a nanoporous structure is fabricated. The cryogel method is used to develop a hierarchy structure on the nano- and microscale in the hydrogel media that is similar to the mesophyll cells and veins of a leaf, respectively. The theoretical model is analyzed to calculate the flow resistance in the artificial leaf, and compare the model with the experimental results. The experiment involves connecting a glass capillary tube at the bottom of the artificial leaf to observe the fluid velocity in the glass capillary tube generated by the negative pressure. The use of silicone oil as fluid instead of water to increase the flow resistance enables the measurement of negative pressure. The negative pressure of the artificial leaf is affected by several variables (e.g., pore size, wettability of the structure). Finally, by decreasing the pore size and increasing the wettability, the maximum negative pressure of the artificial leaf, -7.9 kPa is obtained.

Origin of superconductivity in KFe2As2 under positive and negative pressures and relation to other Fe-based families

NASA Astrophysics Data System (ADS)

Valenti, Roser

KFe2As2 shows an intricate behavior as a function of pressure. At ambient pressure the system is superconductor with a low critical temperature Tc=3.4 K and follows a V-shaped pressure dependence of Tc for moderate pressures with a local minimum at a pressure of 1.5 GPa. Under high pressures Pc=15 GPa, KFe2As2 exhibits a structural phase transition from a tetragonal to a collapsed tetragonal phase accompanied by a boost of the superconducting critical temperature up to 12 K. On the other hand, negative pressures realized through substitution of K by Cs or Rb decrease Tc down to 2.25K. In this talk we will discuss recent progress on the understanding of the microscopic origin of this pressure-dependent behavior by considering a combination of ab initio density functional theory with dynamical mean field theory and spin fluctuation theory calculations. We will argue that a Lifshitz transition associated with the structural collapse changes the pairing symmetry from d-wave (tetragonal) to s+/- (collapsed tetragonal) at high pressures while at ambient and negative pressures correlation effects appear to be detrimental for superconductivity. Further, we shall establish cross-links to the chalcogenide family, in particular FeSe under pressure. The Deutsche Forschungsgemeinschaft (DFG) is gratefully acknowledged for financial support.

The effects of superimposed tilt and lower body negative pressure on anterior and posterior cerebral circulations.

PubMed

Tymko, Michael M; Rickards, Caroline A; Skow, Rachel J; Ingram-Cotton, Nathan C; Howatt, Michael K; Day, Trevor A

2016-09-01

Steady-state tilt has no effect on cerebrovascular reactivity to increases in the partial pressure of end-tidal carbon dioxide (PETCO2). However, the anterior and posterior cerebral circulations may respond differently to a variety of stimuli that alter central blood volume, including lower body negative pressure (LBNP). Little is known about the superimposed effects of head-up tilt (HUT; decreased central blood volume and intracranial pressure) and head-down tilt (HDT; increased central blood volume and intracranial pressure), and LBNP on cerebral blood flow (CBF) responses. We hypothesized that (a) cerebral blood velocity (CBV; an index of CBF) responses during LBNP would not change with HUT and HDT, and (b) CBV in the anterior cerebral circulation would decrease to a greater extent compared to posterior CBV during LBNP when controlling PETCO2 In 13 male participants, we measured CBV in the anterior (middle cerebral artery, MCAv) and posterior (posterior cerebral artery, PCAv) cerebral circulations using transcranial Doppler ultrasound during LBNP stress (-50 mmHg) in three body positions (45°HUT, supine, 45°HDT). PETCO2 was measured continuously and maintained at constant levels during LBNP through coached breathing. Our main findings were that (a) steady-state tilt had no effect on CBV responses during LBNP in both the MCA (P = 0.077) and PCA (P = 0.583), and (b) despite controlling for PETCO2, both the MCAv and PCAv decreased by the same magnitude during LBNP in HUT (P = 0.348), supine (P = 0.694), and HDT (P = 0.407). Here, we demonstrate that there are no differences in anterior and posterior circulations in response to LBNP in different body positions. © 2016 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.

Industrially induced changes in Earth structure at the geysers geothermal area, California

USGS Publications Warehouse

Foulger, G.R.; Grant, C.C.; Ross, A.; Julian, B.R.

1997-01-01

Industrial exploitation is causing clearly-measurable changes in Earth structure at The Geysers geothermal area, California. Production at The Geysers peaked in the late 1980s at ???3.5 ?? 103 kg s-1 of steam and 1800 MW of electricity. It subsequently decreased by about 10% per year [Barker et al., 1992] because of declining reservoir pressure. The steam reservoir coincides with a strong negative anomaly (???0.16, ???9%) in the compressional-to-shear seismic wave speed ratio vP/vS, consistent with the expected effects of low-pressure vapor-phase pore fluid [Julian et al., 1996]. Between 1991 and 1994 this anomaly increased in amplitude by up to about 0.07 (???4%). This is consistent with the expected effects of continued pressure reduction and conversion of pore water to steam as a result of exploitation. These unique results show that vP/vS tomography can easily detect saturation changes caused by exploitation of reservoirs, and is a potentially valuable technique for monitoring environmental change. They also provide geophysical observational evidence that geothermal energy is not a renewable energy source.

Industrially induced changes in Earth structure at the Geysers Geothermal Area, California

NASA Astrophysics Data System (ADS)

Foulger, G. R.; Grant, C. C.; Ross, A.; Julian, B. R.

Industrial exploitation is causing clearly-measurable changes in Earth structure at The Geysers geothermal area, California. Production at The Geysers peaked in the late 1980s at ˜3.5 × 10³ kg s-1 of steam and 1800 MW of electricity. It subsequently decreased by about 10% per year [Barker et al., 1992] because of declining reservoir pressure. The steam reservoir coincides with a strong negative anomaly (˜0.16, ˜9%) in the compressional-to-shear seismic wave speed ratio VP/ VS, consistent with the expected effects of low-pressure vapor-phase pore fluid [Julian et al., 1996]. Between 1991 and 1994 this anomaly increased in amplitude by up to about 0.07 (˜4%). This is consistent with the expected effects of continued pressure reduction and conversion of pore water to steam as a result of exploitation. These unique results show that VP/VS tomography can easily detect saturation changes caused by exploitation of reservoirs, and is a potentially valuable technique for monitoring environmental change. They also provide geophysical observational evidence that geothermal energy is not a renewable energy source.

Control of upper airway muscle activity in younger versus older men during sleep onset

PubMed Central

Fogel, Robert B; White, David P; Pierce, Robert J; Malhotra, Atul; Edwards, Jill K; Dunai, Judy; Kleverlaan, Darci; Trinder, John

2003-01-01

Pharyngeal dilator muscles are clearly important in the pathophysiology of obstructive sleep apnoea syndrome (OSA). We have previously shown that the activity of both the genioglossus (GGEMG) and tensor palatini (TPEMG) are decreased at sleep onset, and that this decrement in muscle activity is greater in the apnoea patient than in healthy controls. We have also previously shown this decrement to be greater in older men when compared with younger ones. In order to explore the mechanisms responsible for this decrement in muscle activity nasal continuous positive airway pressure (CPAP) was applied to reduce negative pressure mediated muscle activation. We then investigated the effect of sleep onset (transition from predominantly α to predominantly θ EEG activity) on ventilation, upper airway muscle activation and upper airway resistance (UAR) in middle-aged and younger healthy men. We found that both GGEMG and TPEMG were reduced by the application of nasal CPAP during wakefulness, but that CPAP did not alter the decrement in activity in either muscle seen in the first two breaths following an α to θ transition. However, CPAP prevented both the rise in UAR at sleep onset that occurred on the control night, and the recruitment in GGEMG seen in the third to fifth breaths following the α to θ transition. Further, GGEMG was higher in the middle-aged men than in the younger men during wakefulness and was decreased more in the middle-aged men with the application of nasal CPAP. No differences were seen in TPEMG between the two age groups. These data suggest that the initial sleep onset reduction in upper airway muscle activity is due to loss of a ‘wakefulness’ stimulus, rather than to loss of responsiveness to negative pressure. In addition, it suggests that in older men, higher wakeful muscle activity is due to an anatomically more collapsible upper airway with more negative pressure driven muscle activation. Sleep onset per se does not appear to have a greater effect on upper airway muscle activity as one ages. PMID:12963804

Comparison of the effects of continuous positive airway pressure and mandibular advancement devices on sleepiness in patients with obstructive sleep apnoea: a network meta-analysis.

PubMed

Bratton, Daniel J; Gaisl, Thomas; Schlatzer, Christian; Kohler, Malcolm

2015-11-01

Excessive daytime sleepiness is the most important symptom of obstructive sleep apnoea and can affect work productivity, quality of life, and the risk of road traffic accidents. We aimed to quantify the effects of the two main treatments for obstructive sleep apnoea (continuous positive airway pressure and mandibular advancement devices) on daytime sleepiness and to establish predictors of response to continuous positive airway pressure. We searched MEDLINE and the Cochrane Library from inception to May 31, 2015, to identify randomised controlled trials comparing the effects of continuous positive airway pressure, mandibular advancement devices or an inactive control (eg, placebo or no treatment) on the Epworth Sleepiness Scale (ESS, range 0-24 points) in patients with obstructive sleep apnoea. We did a network meta-analysis using multivariate random-effects meta-regression to assess the effect of each treatment on ESS. We used meta-regression to assess the association of the reported effects of continuous positive airway pressure versus inactive controls with the characteristics of trials and their risk of bias. We included 67 studies comprising 6873 patients in the meta-analysis. Compared with an inactive control, continuous positive airway pressure was associated with a reduction in ESS score of 2·5 points (95% CI 2·0-2·9) and mandibular advancement devices of 1·7 points (1·1-2·3). We estimated that, on average, continuous positive airway pressure reduced the ESS score by a further 0·8 points compared with mandibular advancement devices (95% CI 0·1-1·4; p=0·015). However, there was a possibility of publication bias in favour of continuous positive airway pressure that might have resulted in this difference. We noted no evidence that studies reporting higher continuous positive airway pressure adherence also reported larger treatment effects (p=0·70). Continuous positive airway pressure and mandibular advancement devices are effective treatments for reducing daytime sleepiness in patients with obstructive sleep apnoea. Continuous positive airway pressure seemed to be a more effective treatment than mandibular advancement devices, and had an increasingly larger effect in more severe or sleepier obstructive sleep apnoea patients when compared with inactive controls. However, mandibular advancement devices are an effective alternative treatment should continuous positive airway pressure not be tolerated. Swiss National Science Foundation and the University of Zurich Clinical Research Priority Program Sleep and Health. Copyright © 2015 Elsevier Ltd. All rights reserved.

The influence of systemic hemodynamics and oxygen transport on cerebral oxygen saturation in neonates after the Norwood procedure.

PubMed

Li, Jia; Zhang, Gencheng; Holtby, Helen; Guerguerian, Anne-Marie; Cai, Sally; Humpl, Tilman; Caldarone, Christopher A; Redington, Andrew N; Van Arsdell, Glen S

2008-01-01

Ischemic brain injury is an important morbidity in neonates after the Norwood procedure. Its relationship to systemic hemodynamic oxygen transport is poorly understood. Sixteen neonates undergoing the Norwood procedure were studied. Continuous cerebral oxygen saturation was measured by near-infrared spectroscopy. Continuous oxygen consumption was measured by respiratory mass spectrometry. Pulmonary and systemic blood flow, systemic vascular resistance, oxygen delivery, and oxygen extraction ratio were derived with measurements of arterial, and superior vena cava and pulmonary venous gases and pressures at 2- to 4-hour intervals during the first 72 hours in the intensive care unit. Mean cerebral oxygen saturation was 66% +/- 12% before the operation, reduced to 51% +/- 13% on arrival in the intensive care unit, and remained low during the first 8 hours; it increased to 56% +/- 9% at 72 hours, still significantly lower than the preoperative level (P < .05). Postoperatively, cerebral oxygen saturation was closely and positively correlated with systemic arterial pressure, arterial oxygen saturation, and arterial oxygen tension and negatively with oxygen extraction ratio (P < .0001 for all). Cerebral oxygen saturation was moderately and positively correlated with systemic blood flow and oxygen delivery (P < .0001 for both). It was weakly and positively correlated with pulmonary blood flow (P = .001) and hemoglobin (P = .02) and negatively correlated with systemic vascular resistance (P = .003). It was not correlated with oxygen consumption (P > .05). Cerebral oxygen saturation decreased significantly in neonates during the early postoperative period after the Norwood procedure and was significantly influenced by systemic hemodynamic and metabolic events. As such, hemodynamic interventions to modify systemic oxygen transport may provide further opportunities to reduce the risk of cerebral ischemia and improve neurodevelopmental outcomes.

Traction-assisted Internal Negative Pressure Wound Therapy With Bridging Retention Sutures to Facilitate Staged Closure of High-risk Wounds Under Tension.

PubMed

DeFazio, Michael V; Economides, James M; Anghel, Ersilia L; Mathis, Ryan K; Barbour, John R; Attinger, Christopher E

2017-10-01

Loss of domain often complicates attempts at delayed wound closure in regions of high tension. Wound temporization with traction-assisted internal negative pressure wound therapy (NPWT), using bridging retention sutures, can minimize the effects of edema and elastic recoil that contribute to progressive tissue retraction over time. The investigators evaluated the safety and efficacy of this technique for complex wound closure. Between May 2015 and November 2015, 18 consecutive patients underwent staged reconstruction of complex and/or contaminated soft tissue defects utilizing either conventional NPWT or modified NPWT with instillation and continuous dermatotraction via bridging retention sutures. Instillation of antimicrobial solution was reserved for wounds containing infected/exposed hardware or prosthetic devices. Demographic data, wound characteristics, reconstructive outcomes, and complications were reviewed retrospectively. Eighteen wounds were treated with traction-assisted internal NPWT using the conventional (n = 11) or modified instillation (n = 7) technique. Defects involved the lower extremity (n = 14), trunk (n = 3), and proximal upper extremity (n = 1), with positive cultures identified in 12 wounds (67%). Therapy continued for 3 to 8 days (mean, 4.3 days), resulting in an average wound surface area reduction of 78% (149 cm² vs. 33 cm²) at definitive closure. Seventeen wounds (94%) were closed directly, whereas the remaining defect required coverage with a local muscle flap and skin graft. At final follow-up (mean, 12 months), 89% of wounds remained closed. In 2 patients with delayed, recurrent periprosthetic infection (mean, 7.5 weeks), serial debridement/hardware removal mandated free tissue transfer for composite defect reconstruction. Traction-assisted internal NPWT provides a safe and effective alternative to reduce wound burden and facilitate definitive closure in cases where delayed reconstruction of high-tension wounds is planned.

Effect of amplitude and duration of impulsive pressure on endothelial permeability in in vitro fluid percussion trauma

PubMed Central

2014-01-01

Background Intracranial pressure changes during head impact cause brain injuries such as vasogenic edema and cerebral contusion. However, the influence of impulsive pressure on endothelial function has not yet been fully studied in vitro. In this study, we developed a pressure loading device that produced positive and negative pressures by modifying an in vitro fluid percussion model and examined the effects of the amplitude and duration of the pressures on endothelial permeability. Methods Human umbilical vein endothelial cells were subjected to three types of positive pressure (average amplitude/average duration of 352 kPa/23 ms, 73 kPa/27 ms, and 70 kPa/44 ms) and three types of negative pressure (−72 kPa/41 ms, −67 kPa/104 ms, and −91 kPa/108 ms), and the transendothelial electrical resistance (TEER) was measured between 15 min and 24 h after pressure loading for quantifying the formation of an integral monolayer of endothelial cells. After loading, vascular endothelial- (VE-) cadherin, an endothelium-specific cell-cell adhesion molecule involved in endothelial barrier function, was stained and observed using fluorescence microscopy. Results The pressure loading device could produce positive pressure pulses with amplitudes of 53–1348 kPa and durations of 9–29.1 ms and negative pressure pulses with amplitudes of −52–−93 kPa and durations of 42.9–179.5 ms. The impulsive pressure reduced the TEER associated with the change in VE-cadherin localization. Additionally, TEER decreased considerably at 15 min and 6 h post-loading, with these changes being significant in positive pressure with larger amplitude and shorter duration and in all types of negative pressures compared to pre-loading. Conclusions The changes in intracranial pressure during head impact impair endothelial barrier function by the disruption of the integrity of endothelial cell-cell junctions, and the degree of increase in endothelial permeability depends on the amplitude, duration, and direction (compressive and tensile) of the impulsive pressure. PMID:24739360

Topological phase transition and evolution of edge states in In-rich InGaN/GaN quantum wells under hydrostatic pressure

NASA Astrophysics Data System (ADS)

Łepkowski, S. P.; Bardyszewski, W.

2017-02-01

Combining the k · p method with the third-order elasticity theory, we perform a theoretical study of the pressure-induced topological phase transition and the pressure evolution of topologically protected edge states in InN/GaN and In-rich InGaN/GaN quantum wells. We show that for a certain range of the quantum well parameters, thanks to a negative band gap pressure coefficient, it is possible to continuously drive the system from the normal insulator state through the topological insulator into the semimetal phase. The critical pressure for the topological phase transition depends not only on the quantum well thickness but also on the width of the Hall bar, which determines the coupling between the edge states localized at the opposite edges. We also find that in narrow Hall bar structures, near the topological phase transition, a significant Rashba-type spin splitting of the lower and upper branches of the edge state dispersion curve appears. This effect originates from the lack of the mirror symmetry of the quantum well potential caused by the built-in electric field, and can be suppressed by increasing the Hall bar width. When the pressure increases, the energy dispersion of the edge states becomes more parabolic-like and the spin splitting decreases. A further increase of pressure leads to the transition to a semimetal phase, which occurs due to the closure of the indirect 2D bulk band gap. The difference between the critical pressure at which the system becomes semimetallic, and the pressure for the topological phase transition, correlates with the variation of the pressure coefficient of the band gap in the normal insulator state.

Topological phase transition and evolution of edge states in In-rich InGaN/GaN quantum wells under hydrostatic pressure.

PubMed

Łepkowski, S P; Bardyszewski, W

2017-02-08

Combining the k · p method with the third-order elasticity theory, we perform a theoretical study of the pressure-induced topological phase transition and the pressure evolution of topologically protected edge states in InN/GaN and In-rich InGaN/GaN quantum wells. We show that for a certain range of the quantum well parameters, thanks to a negative band gap pressure coefficient, it is possible to continuously drive the system from the normal insulator state through the topological insulator into the semimetal phase. The critical pressure for the topological phase transition depends not only on the quantum well thickness but also on the width of the Hall bar, which determines the coupling between the edge states localized at the opposite edges. We also find that in narrow Hall bar structures, near the topological phase transition, a significant Rashba-type spin splitting of the lower and upper branches of the edge state dispersion curve appears. This effect originates from the lack of the mirror symmetry of the quantum well potential caused by the built-in electric field, and can be suppressed by increasing the Hall bar width. When the pressure increases, the energy dispersion of the edge states becomes more parabolic-like and the spin splitting decreases. A further increase of pressure leads to the transition to a semimetal phase, which occurs due to the closure of the indirect 2D bulk band gap. The difference between the critical pressure at which the system becomes semimetallic, and the pressure for the topological phase transition, correlates with the variation of the pressure coefficient of the band gap in the normal insulator state.

A lower body negative pressure box for +Gz simulation in the upright seated position.

DOT National Transportation Integrated Search

1979-02-01

The cost of purchasing and operating a human centrifuge is substantial. Lower body negative pressure (LBNP) is considered an acceptable experimental substitute for the +Gz stress of the centrifuge. Since civil aviation pilots are usually subjected to...

Analytical solution for tension-saturated and unsaturated flow from wicking porous pipes in subsurface irrigation: The Kornev-Philip legacies revisited

NASA Astrophysics Data System (ADS)

Kacimov, A. R.; Obnosov, Yu. V.

2017-03-01

The Russian engineer Kornev in his 1935 book raised perspectives of subsurface "negative pressure" irrigation, which have been overlooked in modern soil science. Kornev's autoirrigation utilizes wicking of a vacuumed water from a porous pipe into a dry adjacent soil. We link Kornev's technology with a slightly modified Philip (1984)'s analytical solutions for unsaturated flow from a 2-D cylindrical pipe in an infinite domain. Two Darcian flows are considered and connected through continuity of pressure along the pipe-soil contact. The first fragment is a thin porous pipe wall in which water seeps at tension saturation; the hydraulic head is a harmonic function varying purely radially across the wall. The Thiem solution in this fragment gives the boundary condition for azimuthally varying suction pressure in the second fragment, ambient soil, making the exterior of the pipe. The constant head, rather than Philip's isobaricity boundary condition, along the external wall slightly modifies Philip's formulae for the Kirchhoff potential and pressure head in the soil fragment. Flow characteristics (magnitudes of the Darcian velocity, total flow rate, and flow net) are explicitly expressed through series of Macdonald's functions. For a given pipe's external diameter, wall thickness, position of the pipe above a free water datum in the supply tank, saturated conductivities of the wall and soil, and soil's sorptive number, a nonlinear equation with respect to the total discharge from the pipe is obtained and solved by a computer algebra routine. Efficiency of irrigation is evaluated by computation of the moisture content within selected zones surrounding the porous pipe.