Design of a tissue oxygenation monitor and verification on human skin

NASA Astrophysics Data System (ADS)

Liu, Hongyuan; Kohl-Bareis, Matthias; Huang, Xiabing

2011-07-01

We report the design of a tissue oxygen and temperature monitor. The non-invasive, fibre based device monitors tissue haemoglobin (Hb) and oxygen saturation (SO2) and is based on white-light reflectance spectroscopy.Visible light with wavelengths in the 500 - 650nm range is utilized. The spectroscopic algorithm takes into account the tissue scattering and melanin absorption for the calculation of tissue haemoglobin concentration and oxygen saturation. The monitor can probe superficial layers of tissue with a high spatial resolution (mm3) and a high temporal resolution (40 Hz). It provides an accurate measurement with the accuracy of SO2 at 2 % and high reliability with less than 2 % variation of continuous SO2 measurement over 12 hours. It can also form a modular system when used in conjunction with a laser Doppler monitor, enabling simultaneous measurements of Hb, SO2 and blood flow. We found experimentally that the influence of the source-detector separation on the haemoglobin parameters is small. This finding is discussed by Monte Carlo simulations for the depth sensitivity profile. The influence of probe pressure and the skin pigmentation on the measurement parameters are assessed before in vivo experimental data is presented. The combination with laser Doppler flowmetry demonstrates the importance of a measurement of both the haemoglobin and the blood flow parameters for a full description of blood tissue perfusion. This is discussed in experimental data on human skin during cuff occlusion and after hyperemisation by a pharmacological cream. Strong correlation is observed between tissue oxygen (Hb and SO2) and blood flow measurements.

Direct tissue oxygen monitoring by in vivo photoacoustic lifetime imaging (PALI)

NASA Astrophysics Data System (ADS)

Shao, Qi; Morgounova, Ekaterina; Ashkenazi, Shai

2014-03-01

Tissue oxygen plays a critical role in maintaining tissue viability and in various diseases, including response to therapy. Images of oxygen distribution provide the history of tissue hypoxia and evidence of oxygen availability in the circulatory system. Currently available methods of direct measuring or imaging tissue oxygen all have significant limitations. Previously, we have reported a non-invasive in vivo imaging modality based on photoacoustic lifetime. The technique maps the excited triplet state of oxygen-sensitive dye, thus reflects the spatial and temporal distribution of tissue oxygen. We have applied PALI on tumor hypoxia in small animals, and the hypoxic region imaged by PALI is consistent with the site of the tumor imaged by ultrasound. Here, we present two studies of applying PALI to monitor changes of tissue oxygen by modulations. The first study involves an acute ischemia model using a thin thread tied around the hind limb of a normal mouse to reduce the blood flow. PALI images were acquired before, during, and after the restriction. The drop of muscle pO2 and recovery from hypoxia due to reperfusion were observed by PALI tracking the same region. The second study modulates tissue oxygen by controlling the percentage of oxygen the mouse inhales. We demonstrate that PALI is able to reflect the change of oxygen level with respect to both hyperbaric and hypobaric conditions. We expect this technique to be very attractive for a range of clinical applications in which tissue oxygen mapping would improve therapy decision making and treatment planning.

Two-photon microscopy measurement of cerebral metabolic rate of oxygen using periarteriolar oxygen concentration gradients.

PubMed

Sakadžić, Sava; Yaseen, Mohammad A; Jaswal, Rajeshwer; Roussakis, Emmanuel; Dale, Anders M; Buxton, Richard B; Vinogradov, Sergei A; Boas, David A; Devor, Anna

2016-10-01

The cerebral metabolic rate of oxygen ([Formula: see text]) is an essential parameter for evaluating brain function and pathophysiology. However, the currently available approaches for quantifying [Formula: see text] rely on complex multimodal imaging and mathematical modeling. Here, we introduce a method that allows estimation of [Formula: see text] based on a single measurement modality-two-photon imaging of the partial pressure of oxygen ([Formula: see text]) in cortical tissue. We employed two-photon phosphorescence lifetime microscopy (2PLM) and the oxygen-sensitive nanoprobe PtP-C343 to map the tissue [Formula: see text] distribution around cortical penetrating arterioles. [Formula: see text] is subsequently estimated by fitting the changes of tissue [Formula: see text] around arterioles with the Krogh cylinder model of oxygen diffusion. We measured the baseline [Formula: see text] in anesthetized rats and modulated tissue [Formula: see text] levels by manipulating the depth of anesthesia. This method provides [Formula: see text] measurements localized within [Formula: see text] and it may provide oxygen consumption measurements in individual cortical layers or within confined cortical regions, such as in ischemic penumbra and the foci of functional activation.

Simultaneous measurement of brain tissue oxygen partial pressure, temperature, and global oxygen consumption during hibernation, arousal, and euthermy in non-sedated and non-anesthetized Arctic ground squirrels.

PubMed

Ma, Yilong; Wu, Shufen

2008-09-30

This study reports an online temperature correction method for determining tissue oxygen partial pressure P(tO2) in the striatum and a novel simultaneous measurement of brain P(tO2) and temperature (T(brain)) in conjunction with global oxygen consumption V(O2) in non-sedated and non-anesthetized freely moving Arctic ground squirrels (AGS, Spermophilus parryii). This method fills an important research gap-the lack of a suitable method for physiologic studies of tissue P(O2) in hibernating or other cool-blooded species. P(tO2) in AGS brain during euthermy (21.22+/-2.06 mmHg) is significantly higher (P=0.016) than during hibernation (13.21+/-0.46 mmHg) suggests brain oxygenation in the striatum is normoxic during euthermy and hypoxic during hibernation. These results in P(tO2) are different from blood oxygen partial pressure P(aO2) in AGS, which are significantly lower during euthermy than during hibernation and are actually hypoxic during euthermy and normoxic during hibernation in our previous study. This intriguing difference between the P(O2) of brain tissue and blood during these two physiological states suggests that regional mechanisms in the brain play a role in maintaining tissue oxygenation and protect against hypoxia during hibernation.

Optoacoustic measurements of human placenta and umbilical blood oxygenation

NASA Astrophysics Data System (ADS)

Nanovskaya, T. N.; Petrov, I. Y.; Petrov, Y.; Patrikeeva, S. L.; Ahmed, M. S.; Hankins, G. D. V.; Prough, D. S.; Esenaliev, R. O.

2016-03-01

Adequate oxygenation is essential for normal embryogenesis and fetal growth. Perturbations in the intrauterine oxidative environment during pregnancy are associated with several pathophysiological disorders such as pregnancy loss, preeclampsia, and intrauterine growth restriction. We proposed to use optoacoustic technology for monitoring placental and fetal umbilical blood oxygenation. In this work, we studied optoacoustic monitoring of oxygenation in placenta and umbilical cord blood ex vivo using technique of placenta perfusion. We used a medical grade, nearinfrared, tunable, optoacoustic system developed and built for oxygenation monitoring in blood vessels and in tissues. First, we calibrated the system for cord blood oxygenation measurements by using a CO-Oximeter (gold standard). Then we performed validation in cord blood circulating through the catheters localized on the fetal side of an isolated placental lobule. Finally, the oxygenation measurements were performed in the perfused placental tissue. To increase or decrease blood oxygenation, we used infusion of a gas mixture of 95% O2 + 5% CO2 and 95% N2 + 5% CO2, respectively. In placental tissue, up to four cycles of changes in oxygenation were performed. The optoacoustically measured oxygenation in circulating cord blood and in placental lobule closely correlated with the actual oxygenation data measured by CO-Oximeter. We plan to further test the placental and cord blood oxygenation monitoring with optoacoustics in animal and clinical studies.

Hemodynamic parameters change earlier than tissue oxygen tension in hemorrhage.

PubMed

Pestel, Gunther J; Fukui, Kimiko; Kimberger, Oliver; Hager, Helmut; Kurz, Andrea; Hiltebrand, Luzius B

2010-05-15

Untreated hypovolemia results in impaired outcome. This study tests our hypothesis whether general hemodynamic parameters detect acute blood loss earlier than monitoring parameters of regional tissue beds. Eight pigs (23-25 kg) were anesthetized and mechanically ventilated. A pulmonary artery catheter and an arterial catheter were inserted. Tissue oxygen tension was measured with Clark-type electrodes in the jejunal and colonic wall, in the liver, and subcutaneously. Jejunal microcirculation was assessed by laser Doppler flowmetry (LDF). Intravascular volume was optimized using difference in pulse pressure (dPP) to keep dPP below 13%. Sixty minutes after preparation, baseline measurements were taken. At first, 5% of total blood volume was withdrawn, followed by another 5% increment, and then in 10% increments until death. After withdrawal of 5% of estimated blood volume, dPP increased from 6.1% +/- 3.0% to 20.8% +/- 2.7% (P < 0.01). Mean arterial pressure (MAP), mean pulmonary artery pressure (PAP) and pulmonary artery occlusion pressure (PAOP) decreased with a blood loss of 10% (P < 0.01). Cardiac output (CO) changed after a blood loss of 20% (P < 0.05). Tissue oxygen tension in central organs, and blood flow in the jejunal muscularis decreased (P < 0.05) after a blood loss of 20%. Tissue oxygen tension in the skin, and jejunal mucosa blood flow decreased (P < 0.05) after a blood loss of 40% and 50%, respectively. In this hemorrhagic pig model systemic hemodynamic parameters were more sensitive to detect acute hypovolemia than tissue oxygen tension measurements or jejunal LDF measurements. Acute blood loss was detected first by dPP. Copyright (c) 2010 Elsevier Inc. All rights reserved.

Fetal oxygenation measurement using wireless near infrared spectroscopy

NASA Astrophysics Data System (ADS)

Macnab, Andrew; Shadgan, Babak; Janssen, Patricia; Rurak, Dan

2012-03-01

Background: Fetal well-being is determined in large part by how well the placenta is able to supply oxygen and nutrients, but current technology is unable to directly measure how well a placenta functions. Near-infrared spectroscopy (NIRS) utilizes optical methods to measure tissue oxygenation. This pilot project evaluated the feasibility of NIRS for fetal monitoring through the maternal abdominal wall using a sheep model. Methods: A miniature wireless 2-wavelength NIRS device was placed on the abdominal skin over the placenta of a pregnant ewe whose fetus had been chronically catheterized to allow arterial sampling for measurement of arterial oxygen saturation. The NIRS device has 3-paired light emitting diodes and a single photodiode detector; allowing measurement of an index of tissue oxygen saturation (TSI%). Fetal limb TSI% values were compared before and during fetal breathing movements. Correlation was made during these events between arterial values and placental TSI% monitored continuously in real time. Results: Serial measurements were obtained in a single experiment. The correlation between transcutaneous NIRS derived TSI% and direct arterial oxygen saturation was very high (R2=0.86). Measures of fetal limb TSI% were declined after episodes of fetal breathing (P<0.005). Conclusions: This correlation suggests that NIRS is sensitive enough to detect changes in fetal tissue oxygenation noninvasively through the maternal abdominal wall in real-time in a sheep model. NIRS data confirmed that fetal breathing movements decrease arterial oxygen saturation in fetal lambs. If validated by further study this optical methodology could be applied as means of monitoring fetal wellbeing in humans.

High-spatial-resolution mapping of the oxygen concentration in cortical tissue (Conference Presentation)

NASA Astrophysics Data System (ADS)

Jaswal, Rajeshwer S.; Yaseen, Mohammad A.; Fu, Buyin; Boas, David A.; Sakadžic, Sava

2016-03-01

Due to a lack of imaging tools for high-resolution imaging of cortical tissue oxygenation, the detailed maps of the oxygen partial pressure (PO2) around arterioles, venules, and capillaries remain largely unknown. Therefore, we have limited knowledge about the mechanisms that secure sufficient oxygen delivery in microvascular domains during brain activation, and provide some metabolic reserve capacity in diseases that affect either microvascular networks or the regulation of cerebral blood flow (CBF). To address this challenge, we applied a Two-Photon PO2 Microscopy to map PO2 at different depths in mice cortices. Measurements were performed through the cranial window in the anesthetized healthy mice as well as in the mouse models of microvascular dysfunctions. In addition, microvascular morphology was recorded by the two-photon microscopy at the end of each experiment and subsequently segmented. Co-registration of the PO2 measurements and exact microvascular morphology enabled quantification of the tissue PO2 dependence on distance from the arterioles, capillaries, and venules at various depths. Our measurements reveal significant spatial heterogeneity of the cortical tissue PO2 distribution that is dominated by the high oxygenation in periarteriolar spaces. In cases of impaired oxygen delivery due to microvascular dysfunction, significant reduction in tissue oxygenation away from the arterioles was observed. These tissue domains may be the initial sites of cortical injury that can further exacerbate the progression of the disease.

Influence of Negative-Pressure Wound Therapy on Tissue Oxygenation in Diabetic Feet.

PubMed

Jung, Jae-A; Yoo, Ki-Hyun; Han, Seung-Kyu; Lee, Ye-Na; Jeong, Seong-Ho; Dhong, Eun-Sang; Kim, Woo-Kyung

2016-08-01

Negative-pressure wound therapy (NPWT) has become a common wound care treatment modality for a variety of wounds. Several previous studies have reported that NPWT increases blood flow in the wound bed. However, NPWT might decrease tissue oxygenation in the wound bed because the foam sponge of NPWT compresses the wound bed under the influence of the applied negative pressure. Adequate tissue oxygenation is an essential consideration during diabetic foot management, and the foot is more sensitive to ischemia than any other region. Furthermore, the issue as to whether NPWT reduces or increases tissue oxygenation in diabetic feet has never been correctly addressed. The aim of this study was to evaluate the influence of NPWT on tissue oxygenation in diabetic feet. Transcutaneous partial oxygen pressures (TcPO2) were measured to determine tissue oxygenation levels beneath NPWT dressings on 21 feet of 21 diabetic foot ulcer patients. A TcPO2 sensor was fixed at the tarsometatarsal area of contralateral unwounded feet. A suction pressure of -125 mm Hg was applied until TcPO2 reached a steady state. The TcPO2 values for diabetic feet were measured before, during, and after NPWT. The TcPO2 levels decreased significantly after applying NPWT in all patients. Mean TcPO2 values before, during, and after therapy were 44.6 (SD, 15.2), 6.0 (SD, 7.1), and 40.3 (SD, 16.4) mm Hg (P < .01), respectively. These results show that NPWT significantly reduces tissue oxygenation levels in diabetic feet.

Change of oxygen pressure in glioblastoma tissue under various conditions.

PubMed

Beppu, Takaaki; Kamada, Katsura; Yoshida, Yuki; Arai, Hiroshi; Ogasawara, Kuniaki; Ogawa, Akira

2002-05-01

Measurement of oxygen pressure (pO2) in tumor tissue is important, because pO2 is a major factor for radiosensitivity in malignant glioma treatment. We attempted to elucidate the changes in pO2 level in glioblastoma tissue of patients under various conditions. Eighteen patients with newly diagnosed glioblastoma were recruited to this study. Disposable Clark-type electrodes were inserted using CT guided stereotactic surgery under local anesthesia and left in the intra- and peritumoral regions. pO2 was measured in patients under conditions of being awake and asleep, inhaling 100% O2, being administered osmotic diuretics and following hyperbaric oxygen exposure (HBO). Peritumoral tissue had a significantly higher pO2 value in both awake and sleeping patients. O2 inhalation could not significantly increase the pO2 level, whereas administration of osmotic diuretics induced an increase in pO2 levels in peritumoral tissue alone. The pO2 levels were significantly increased in both regions after HBO, and a high pO2 level was maintained until 15 min after HBO in both regions. It is possible that the pO2 level in peritumoral tissue is affected by intracranial pressure, whereas that in the intratumoral tissue is usually low. HBO was the optimal procedure for oxygenation, but its benefit was reduced over time.

Oxygen-Releasing Antioxidant Cryogel Scaffolds with Sustained Oxygen Delivery for Tissue Engineering Applications.

PubMed

Shiekh, Parvaiz A; Singh, Anamika; Kumar, Ashok

2018-06-06

With the advancement in biomaterial sciences, tissue-engineered scaffolds are developing as a promising strategy for the regeneration of damaged tissues. However, only a few of these scaffolds have been translated into clinical applications. One of the primary drawbacks of the existing scaffolds is the lack of adequate oxygen supply within the scaffolds. Oxygen-producing biomaterials have been developed as an alternate strategy but are faced with two major concerns. One is the control of the rate of oxygen generation, and the other is the production of reactive oxygen species (ROS). To address these concerns, here, we report the development of an oxygen-releasing antioxidant polymeric cryogel scaffold (PUAO-CPO) for sustained oxygen delivery. PUAO-CPO scaffold was fabricated using the cryogelation technique by the incorporation of calcium peroxide (CPO) in the antioxidant polyurethane (PUAO) scaffolds. The PUAO-CPO cryogels attenuated the ROS and showed a sustained release of oxygen over a period of 10 days. An in vitro analysis of the PUAO-CPO cryogels showed their ability to sustain H9C2 cardiomyoblast cells under hypoxic conditions, with cell viability being significantly better than the normal polyurethane (PU) scaffolds. Furthermore, in vivo studies using an ischemic flap model showed the ability of the oxygen-releasing cryogel scaffolds to prevent tissue necrosis upto 9 days. Histological examination indicated the maintenance of tissue architecture and collagen content, whereas immunostaining for proliferating cell nuclear antigen confirmed the viability of the ischemic tissue with oxygen delivery. Our study demonstrated an advanced approach for the development of oxygen-releasing biomaterials with sustained oxygen delivery as well as attenuated production of residual ROS and free radicals because of ischemia or oxygen generation. Hence, the oxygen-releasing PUAO-CPO cryogel scaffolds may be used with cell-based therapeutic approaches for the regeneration of

Factors Affecting Tissue Oxygenation in Erythrocyte Transfusions

PubMed Central

Aykut, Güçlü; Yürük, Koray; İnce, Can

2014-01-01

Red blood cell transfusions are used to increase the oxygen-carrying capacity of blood in anemic states. But, because of the changes during storage of blood components and the specifics of preparation, erythrocytes may have controversial effects on tissue oxygenation and microcirculation. Also, the patient situation may play a role in the differing responses in oxygenation and microcirculation. In this review, the studies concerning the effects of banked blood and patient characteristics on microcirculation and tissue oxygenation are summarized. PMID:27366403

Non-invasive MRI measurements of venous oxygenation, oxygen extraction fraction and oxygen consumption in neonates.

PubMed

De Vis, J B; Petersen, E T; Alderliesten, T; Groenendaal, F; de Vries, L S; van Bel, F; Benders, M J N L; Hendrikse, J

2014-07-15

Brain oxygen consumption reflects neuronal activity and can therefore be used to investigate brain development or neuronal injury in neonates. In this paper we present the first results of a non-invasive MRI method to evaluate whole brain oxygen consumption in neonates. For this study 51 neonates were included. The T1 and T2 of blood in the sagittal sinus were fitted using the 'T2 prepared tissue relaxation inversion recovery' pulse sequence (T2-TRIR). From the T1 and the T2 of blood, the venous oxygenation and the oxygen extraction fraction (OEF) were calculated. The cerebral metabolic rate of oxygen (CMRO2) was the resultant of the venous oxygenation and arterial spin labeling whole brain cerebral blood flow (CBF) measurements. Venous oxygenation was 59±14% (mean±sd), OEF was 40±14%, CBF was 14±5ml/100g/min and CMRO2 was 30±12μmol/100g/min. The OEF in preterms at term-equivalent age was higher than in the preterms and in the infants with hypoxic-ischemic encephalopathy (p<0.01). The OEF, CBF and CMRO2 increased (p<0.01, <0.05 and <0.01, respectively) with postnatal age. We presented an MRI technique to evaluate whole-brain oxygen consumption in neonates non-invasively. The measured values are in line with reference values found by invasive measurement techniques. Preterms and infants with HIE demonstrated significant lower oxygen extraction fraction than the preterms at term-equivalent age. This could be due to decreased neuronal activity as a reflection of brain development or as a result of tissue damage, increased cerebral blood flow due to immature or impaired autoregulation, or could be caused by differences in postnatal age. Copyright © 2014 Elsevier Inc. All rights reserved.

Non-Invasive Tissue Oxygenation Measurement Systems. Phase 1.

DTIC Science & Technology

1995-10-01

vessels was shown ( in vivo hamster studies) to be a significant factor causing considerable variability in SaO2 in vessels ...shows that trends in blood oxygenation are tracked. The nearly universal applicability and turnkey type measurement capability of pulse oximeters are...approach early in Phase I that might be compatible with laser doppler blood flow measurements. Both methods depend on laser irradiation of the sample

Mapping tissue oxygen in vivo by photoacoustic lifetime imaging

NASA Astrophysics Data System (ADS)

Shao, Qi; Morgounova, Ekaterina; Choi, Jeung-Hwan; Jiang, Chunlan; Bischof, John; Ashkenazi, Shai

2013-03-01

Oxygen plays a key role in the energy metabolism of living organisms. Any imbalance in the oxygen levels will affect the metabolic homeostasis and lead to pathophysiological diseases. Hypoxia, a status of low tissue oxygen, is a key factor in tumor biology as it is highly prominent in tumor tissues. However, clinical tools for assessing tissue oxygenation are limited. The gold standard is polarographic needle electrode which is invasive and not capable of mapping (imaging) the oxygen content in tissue. We applied the method of photoacoustic lifetime imaging (PALI) of oxygen-sensitive dye to small animal tissue hypoxia research. PALI is new technology for direct, non-invasive imaging of oxygen. The technique is based on mapping the oxygen-dependent transient optical absorption of Methylene Blue (MB) by pump-probe photoacoustic imaging. Our studies show the feasibility of imaging of dissolved oxygen distribution in phantoms. In vivo experiments demonstrate that the hypoxia region is consistent with the site of subcutaneously xenografted prostate tumor in mice with adequate spatial resolution and penetration depth.

Cerebral interstitial tissue oxygen tension, pH, HCO3, CO2.

PubMed

Charbel, F T; Hoffman, W E; Misra, M; Hannigan, K; Ausman, J I

1997-10-01

There are many techniques for monitoring the injured brain following trauma, subarachnoid hemorrhage, or surgery. It is thought that the major determinants for recovery of injured cerebral tissue are oxygen, glucose delivery, and the clearance of metabolites. These factors, at optimal levels, are probably responsible for the regaining of neuronal functions. These parameters are in turn dependent on the tissue's blood flow and metabolism. We have been using a single, compact, polyethylene sensor, the Paratrend 7 for the measurement of cerebral oxygen tension, CO2, pH, and temperature. This sensor is designed for continuous blood gas analysis to aid in monitoring neurosurgical patients, both during surgery and in the intensive care unit. Using the Paratrend 7 sensor, we found the normal range of values to be: PO2 33 +/- 11 mm Hg; PCO2 48 +/- 7 mm Hg; pH 7.19 +/- 0.11. Critical measurements are considered to be tissue PO2 < 10 mm Hg; PCO2 > 60 mm Hg, and pH < 6.8. We have had no complications with this device; the risks are similar to those of placing a parenchymal intracranial pressure monitor. We believe that assessment of interstitial cerebral oxygen saturation can be of great value both intraoperatively and postoperatively. In our experience, the Paratrend 7 system is an effective method of measuring tissue cerebral oxygen tension, along with carbon dioxide levels, pH, and temperature.

A pilot study of a new spectrophotometry device to measure tissue oxygen saturation.

PubMed

Abel, Gemma; Allen, John; Drinnan, Michael

2014-09-01

Tissue oxygen saturation (SO2) measurements have the potential for far wider use than at present but are limited by device availability and portability for many potential applications. A device based on a small, low-cost general-purpose spectrophotometer (the Harrison device) might facilitate wider use. The aim of this study was to compare the Harrison device with a commercial instrument, the LEA O2C.Measurements were carried out on the forearm and finger of 20 healthy volunteers, using a blood pressure cuff on the upper arm to induce different levels of oxygenation. Repeatability of both devices was assessed, and the Bland-Altman method was used to assess agreement between them.The devices showed agreement in overall tracking of changes in SO2. Test-retest agreement for the Harrison device was worse than for O2C, with SD repeatability of 10.6% (forearm) or 18.6% (finger). There was no overall bias between devices, but mean (SD) difference of 1.2 (11.8%) (forearm) or 4.4 (11.5%) (finger) were outside of a clinically acceptable range.Disagreements were attributed to the stability of the Harrison probe and the natural SO2 variations across the skin surface increasing the random error. Therefore, though not equivalent to the LEA O2C, a probe redesign and averaged measurements may help establish the Harrison device as a low cost alternative.

Planar implantable sensor for in vivo measurement of cellular oxygen metabolism in brain tissue.

PubMed

Tsytsarev, Vassiliy; Akkentli, Fatih; Pumbo, Elena; Tang, Qinggong; Chen, Yu; Erzurumlu, Reha S; Papkovsky, Dmitri B

2017-04-01

Brain imaging methods are continually improving. Imaging of the cerebral cortex is widely used in both animal experiments and charting human brain function in health and disease. Among the animal models, the rodent cerebral cortex has been widely used because of patterned neural representation of the whiskers on the snout and relative ease of activating cortical tissue with whisker stimulation. We tested a new planar solid-state oxygen sensor comprising a polymeric film with a phosphorescent oxygen-sensitive coating on the working side, to monitor dynamics of oxygen metabolism in the cerebral cortex following sensory stimulation. Sensory stimulation led to changes in oxygenation and deoxygenation processes of activated areas in the barrel cortex. We demonstrate the possibility of dynamic mapping of relative changes in oxygenation in live mouse brain tissue with such a sensor. Oxygenation-based functional magnetic resonance imaging (fMRI) is very effective method for functional brain mapping but have high costs and limited spatial resolution. Optical imaging of intrinsic signal (IOS) does not provide the required sensitivity, and voltage-sensitive dye optical imaging (VSDi) has limited applicability due to significant toxicity of the voltage-sensitive dye. Our planar solid-state oxygen sensor imaging approach circumvents these limitations, providing a simple optical contrast agent with low toxicity and rapid application. The planar solid-state oxygen sensor described here can be used as a tool in visualization and real-time analysis of sensory-evoked neural activity in vivo. Further, this approach allows visualization of local neural activity with high temporal and spatial resolution. Copyright © 2017 Elsevier B.V. All rights reserved.

Topical oxygen therapy & micro/nanobubbles: a new modality for tissue oxygen delivery.

PubMed

Sayadi, Lohrasb R; Banyard, Derek A; Ziegler, Mary E; Obagi, Zaidal; Prussak, Jordyne; Klopfer, Michael J; Evans, Gregory Rd; Widgerow, Alan D

2018-06-01

Up to 15 billion dollars of US health care expenditure each year is consumed by treatment of poorly healing wounds whose etiologies are often associated with aberrancies in tissue oxygenation. To address this issue, several modes of tissue oxygen delivery systems exist, including Hyperbaric Oxygen Therapy (HBOT) and Topical Oxygen Therapy (TOT), but their efficacies have yet to be fully substantiated. Micro/nanobubbles (MNBs), which range anywhere from 100 μm to <1 μm in diameter and are relatively stable for hours, offer a new mode of oxygen delivery to wounds. The aim of this article is to systematically review literature examining the use of TOT for wound healing and use of MNBs for tissue oxygenation using the MEDLINE database. The search yielded 87 articles (12 MNB articles and 75 TOT articles), of which 52 met the inclusion criteria for this literature review (12 MNB articles and 40 TOT articles). Additionally, we present an analysis on the efficacy of our MNB generating technology and propose its use as a wound healing agent. © 2018 Medicalhelplines.com Inc and John Wiley & Sons Ltd.

Near-infrared spectroscopy monitoring during immediate transition after birth: time to obtain cerebral tissue oxygenation.

PubMed

Ziehenberger, Evelyn; Urlesberger, Berndt; Binder-Heschl, Corinna; Schwaberger, Bernhard; Baik-Schneditz, Nariae; Pichler, Gerhard

2018-06-01

Feasibility of cerebral tissue oxygenation measurements immediately after birth has been published starting with first values 2 min after birth. Aim of this study was to evaluate, the time periods from birth and from arrival at the resuscitation table to obtain the first cerebral tissue oxygenation values with two different near infrared spectroscopy (NIRS) devices. The present study is an analysis of exploratory parameters of two prospective observational studies. Cerebral tissue oxygen saturation was measured by the NIRO 200NX measuring "cerebral-tissue-oxygenation-index" (cTOI) or the INVOS5100C measuring "cerebral-regional-oxygen-saturation" (crSO 2 ). Four time periods (T) were defined: T1 birth to arrival at resuscitation table, T2 arrival to application of NIRS sensor, T3 application to first displayed cTOI or crSO 2 value, and T4 from arrival at resuscitation table to first displayed values. Additionally, we compared first displayed values of cTOI and crSO 2 . Thirty neonates were included. Twenty-four were term and six late-preterm neonates. Fifteen neonates measured with NIRO were compared to 15 measured with INVOS. T1 was 49 (6-163) s with NIRO versus 59 (15-87) s with INVOS, T2 14 (4-20) s versus 12 (15-18) s, T3 33 (13-138) s versus 17 (6-290) s and T4 46 (20-153) s and 34 (14-300) s. The first displayed value tended to be higher for cTOI [54% (18-80)] compared to crSO 2 [35% (15-87)]. There were no significant differences between devices in time periods and first values displayed. Cerebral tissue oxygenation can be measured within 1 min after arriving at the resuscitation table in term and preterm neonates after birth without difference between devices.

Quantitative spatially resolved measurement of tissue chromophore concentrations using photoacoustic spectroscopy: application to the measurement of blood oxygenation and haemoglobin concentration.

PubMed

Laufer, Jan; Delpy, Dave; Elwell, Clare; Beard, Paul

2007-01-07

A new approach based on pulsed photoacoustic spectroscopy for non-invasively quantifying tissue chromophore concentrations with high spatial resolution has been developed. The technique is applicable to the quantification of tissue chromophores such as oxyhaemoglobin (HbO(2)) and deoxyhaemoglobin (HHb) for the measurement of physiological parameters such as blood oxygen saturation (SO(2)) and total haemoglobin concentration. It can also be used to quantify the local accumulation of targeted contrast agents used in photoacoustic molecular imaging. The technique employs a model-based inversion scheme to recover the chromophore concentrations from photoacoustic measurements. This comprises a numerical forward model of the detected time-dependent photoacoustic signal that incorporates a multiwavelength diffusion-based finite element light propagation model to describe the light transport and a time-domain acoustic model to describe the generation, propagation and detection of the photoacoustic wave. The forward model is then inverted by iteratively fitting it to measurements of photoacoustic signals acquired at different wavelengths to recover the chromophore concentrations. To validate this approach, photoacoustic signals were generated in a tissue phantom using nanosecond laser pulses between 740 nm and 1040 nm. The tissue phantom comprised a suspension of intralipid, blood and a near-infrared dye in which three tubes were immersed. Blood at physiological haemoglobin concentrations and oxygen saturation levels ranging from 2% to 100% was circulated through the tubes. The signal amplitude from different temporal sections of the detected photoacoustic waveforms was plotted as a function of wavelength and the forward model fitted to these data to recover the concentrations of HbO(2) and HHb, total haemoglobin concentration and SO(2). The performance was found to compare favourably to that of a laboratory CO-oximeter with measurement resolutions of +/-3.8 g l(-1) (+/-58

Quantitative spatially resolved measurement of tissue chromophore concentrations using photoacoustic spectroscopy: application to the measurement of blood oxygenation and haemoglobin concentration

NASA Astrophysics Data System (ADS)

Laufer, Jan; Delpy, Dave; Elwell, Clare; Beard, Paul

2007-01-01

A new approach based on pulsed photoacoustic spectroscopy for non-invasively quantifying tissue chromophore concentrations with high spatial resolution has been developed. The technique is applicable to the quantification of tissue chromophores such as oxyhaemoglobin (HbO2) and deoxyhaemoglobin (HHb) for the measurement of physiological parameters such as blood oxygen saturation (SO2) and total haemoglobin concentration. It can also be used to quantify the local accumulation of targeted contrast agents used in photoacoustic molecular imaging. The technique employs a model-based inversion scheme to recover the chromophore concentrations from photoacoustic measurements. This comprises a numerical forward model of the detected time-dependent photoacoustic signal that incorporates a multiwavelength diffusion-based finite element light propagation model to describe the light transport and a time-domain acoustic model to describe the generation, propagation and detection of the photoacoustic wave. The forward model is then inverted by iteratively fitting it to measurements of photoacoustic signals acquired at different wavelengths to recover the chromophore concentrations. To validate this approach, photoacoustic signals were generated in a tissue phantom using nanosecond laser pulses between 740 nm and 1040 nm. The tissue phantom comprised a suspension of intralipid, blood and a near-infrared dye in which three tubes were immersed. Blood at physiological haemoglobin concentrations and oxygen saturation levels ranging from 2% to 100% was circulated through the tubes. The signal amplitude from different temporal sections of the detected photoacoustic waveforms was plotted as a function of wavelength and the forward model fitted to these data to recover the concentrations of HbO2 and HHb, total haemoglobin concentration and SO2. The performance was found to compare favourably to that of a laboratory CO-oximeter with measurement resolutions of ±3.8 g l-1 (±58 µM) and ±4

Relationship of oxygen dose to angiogenesis induction in irradiated tissue

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

Marx, R.E.; Ehler, W.J.; Tayapongsak, P.

1990-11-01

This study was accomplished in an irradiated rabbit model to assess the angiogenic properties of normobaric oxygen and hyperbaric oxygen as compared with air-breathing controls. Results indicated that normobaric oxygen had no angiogenic properties above normal revascularization of irradiated tissue than did air-breathing controls (p = 0.89). Hyperbaric oxygen demonstrated an eight- to ninefold increased vascular density over both normobaric oxygen and air-breathing controls (p = 0.001). Irradiated tissue develops a hypovascular-hypocellular-hypoxic tissue that does not revascularize spontaneously. Results failed to demonstrate an angiogenic effect of normobaric oxygen. It is suggested that oxygen in this sense is a drug requiringmore » hyperbaric pressures to generate therapeutic effects on chronically hypovascular irradiated tissue.« less

In-vivo quantitative measurement of tissue oxygen saturation of human webbing using a transmission type continuous-wave near-infrared spectroscopy

NASA Astrophysics Data System (ADS)

Aizimu, Tuerxun; Adachi, Makoto; Nakano, Kazuya; Ohnishi, Takashi; Nakaguchi, Toshiya; Takahashi, Nozomi; Nakada, Taka-aki; Oda, Shigeto; Haneishi, Hideaki

2018-02-01

Near-infrared spectroscopy (NIRS) is a noninvasive method for monitoring tissue oxygen saturation (StO2). Many commercial NIRS devices are presently available. However, the precision of those devices is relatively poor because they are using the reflectance-model with which it is difficult to obtain the blood volume and other unchanged components of the tissue. Human webbing is a thin part of the hand and suitable to measure spectral transmittance. In this paper, we present a method for measuring StO2 of human webbing from a transmissive continuous-wave nearinfrared spectroscopy (CW-NIRS) data. The method is based on the modified Beer-Lambert law (MBL) and it consists of two steps. In the first step, we give a pressure to the upstream region of the measurement point to perturb the concentration of deoxy- and oxy-hemoglobin as remaining the other components and measure the spectral signals. From the measured data, spectral absorbance due to the components other than hemoglobin is calculated. In the second step, spectral measurement is performed at arbitrary time instance and the spectral absorbance obtained in the step 1 is subtracted from the measured absorbance. The tissue oxygen saturation (StO2) is estimated from the remained data. The method was evaluated on an arterial occlusion test (AOT) and a venous occlusion test (VOT). In the evaluation experiment, we confirmed that reasonable values of StO2 were obtained by the proposed method.

Quantitative assessment of brain tissue oxygenation in porcine models of cardiac arrest and cardiopulmonary resuscitation using hyperspectral near-infrared spectroscopy

NASA Astrophysics Data System (ADS)

Lotfabadi, Shahin S.; Toronov, Vladislav; Ramadeen, Andrew; Hu, Xudong; Kim, Siwook; Dorian, Paul; Hare, Gregory M. T.

2014-03-01

Near-infrared spectroscopy (NIRS) is a non-invasive tool to measure real-time tissue oxygenation in the brain. In an invasive animal experiment we were able to directly compare non-invasive NIRS measurements on the skull with invasive measurements directly on the brain dura matter. We used a broad-band, continuous-wave hyper-spectral approach to measure tissue oxygenation in the brain of pigs under the conditions of cardiac arrest, cardiopulmonary resuscitation (CPR), and defibrillation. An additional purpose of this research was to find a correlation between mortality due to cardiac arrest and inadequacy of the tissue perfusion during attempts at resuscitation. Using this technique we measured the changes in concentrations of oxy-hemoglobin [HbO2] and deoxy-hemoglobin [HHb] to quantify the tissue oxygenation in the brain. We also extracted cytochrome c oxidase changes Δ[Cyt-Ox] under the same conditions to determine increase or decrease in cerebral oxygen delivery. In this paper we proved that applying CPR, [HbO2] concentration and tissue oxygenation in the brain increase while [HHb] concentration decreases which was not possible using other measurement techniques. We also discovered a similar trend in changes of both [Cyt-Ox] concentration and tissue oxygen saturation (StO2). Both invasive and non-invasive measurements showed similar results.

Numerical simulation of oxygen delivery to muscle tissue in the presence of hemoglobin-based oxygen carriers.

PubMed

Patton, Jaqunda N; Palmer, Andre F

2006-01-01

This work represents a culmination of research on oxygen transport to muscle tissue, which takes into account oxygen transport due to convection, diffusion, and the kinetics of simultaneous reactions between oxygen and hemoglobin and myoglobin. The effect of adding hemoglobin-based oxygen carriers (HBOCs) to the plasma layer of blood in a single capillary surrounded by muscle tissue based on the geometry of the Krogh tissue cylinder is examined for a range of HBOC oxygen affinity, HBOC concentration, capillary inlet oxygen tension (pO(2)), and hematocrit. The full capillary length of the hamster retractor muscle was modeled under resting (V(max) = 1.57 x 10(-4) mLO(2) mL(-1) s(-1), cell velocity (v(c)) = 0.015 cm/s) and working (V(max) = 1.57 x 10(-3) mLO(2) mL(-1) s(-1), v(c) = 0.075 cm/s) conditions. Two spacings between the red blood cell (RBC) and the capillary wall were examined, corresponding to a capillary with and without an endothelial surface layer. Simulations led to the following conclusions, which lend physiological insight into oxygen transport to muscle tissue in the presence of HBOCs: (1) The reaction kinetics between oxygen and myoglobin in the tissue region, oxygen and HBOCs in the plasma, and oxygen and RBCs in the capillary lumen should not be neglected. (2) Simulation results yielded new insight into possible mechanisms of oxygen transport in the presence of HBOCs. (3) HBOCs may act as a source or sink for oxygen in the capillary and may compete with RBCs for oxygen. (4) HBOCs return oxygen delivery to muscle tissue to normal for varying degrees of hypoxia (inlet capillary pO(2) < 30 mmHg) and anemia (hematocrit < 46%) for the hamster model.

Non-invasive measurements of tissue hemodynamics with hybrid diffuse optical methods

NASA Astrophysics Data System (ADS)

Durduran, Turgut

Diffuse optical techniques were used to measure hemodynamics of tissues non-invasively. Spectroscopy and tomography of the brain, muscle and implanted tumors were carried out in animal models and humans. Two qualitatively different methods, diffuse optical tomography and diffuse correlation tomography, were hybridized permitting simultaneous measurement of total hemoglobin concentration, blood oxygen saturation and blood flow. This combination of information was processed further to derive estimates of oxygen metabolism (e.g. CMRO 2) in tissue. The diffuse correlation measurements of blood flow were demonstrated in human tissues, for the first time, demonstrating continous, non-invasive imaging of oxygen metabolism in large tissue volumes several centimeters below the tissue surface. The bulk of these investigations focussed on cerebral hemodynamics. Extensive validation of this methodology was carried out in in vivo rat brain models. Three dimensional images of deep tissue hemodynamics in middle cerebral artery occlusion and cortical spreading depression (CSD) were obtained. CSD hemodynamics were found to depend strongly on partial pressure of carbon dioxide. The technique was then adapted for measurement of human brain. All optical spectroscopic measurements of CMRO2 during functional activation were obtained through intact human skull non-invasively. Finally, a high spatio-temporal resolution measurement of cerebral blood flow due to somatosensory cortex activation following electrical forepaw stimulation in rats was carried out with laser speckle flowmetry. New analysis methods were introduced for laser speckle flowmetry. In other organs, deep tissue hemodynamics were measured on human calf muscle during exercise and cuff-ischemia and were shown to have some clinical utility for peripheral vascular disease. In mice tumor models, the measured hemodynamics were shown to be predictive of photodynamic therapy efficacy, again suggesting promise of clinical utility

Tissue Oxygenation in Obese and Non-obese Patients During Laparoscopy

PubMed Central

Fleischmann, Edith; Kurz, Andrea; Niedermayr, Monika; Schebesta, Karl; Kimberger, Oliver; Prager, Gerhard; Sessler, Daniel I.; Kabon, Barbara

2005-01-01

Background: Wound infection risk is inversely related to subcutaneous oxygenation, which is reduced in obese patients and may be reduced even more during laparoscopic procedures. Methods: We evaluated subcutaneous tissue oxygenation (PsqO2) in 20 patients with a body mass index (BMI) ≥40 kg·m–2 (obese) and 15 patients with BMI <30 kg·m-2 (non-obese) undergoing laparoscopic surgery with standardised anaesthesia technique and fluid administration. Arterial oxygen tension was maintained near 150 mmHg. PsqO2 was measured from a surrogate wound on the upper arm. Data were analyzed with unpaired two-tailed t or Wilcoxon rank-sum tests; P < 0.05 was statistically significant. Data are given as mean (SD). Results: An FIO2 of 51% (13%) was required in obese patients to reach an arterial oxygen tension of 150 mmHg; however, an FIO2 of only 40% (7%) was required to reach the same oxygen tension in non-obese patients (P=0.007). PsqO2 was significantly less in obese patients: 41 (10) vs. 57 (15) mmHg (P<0.001). Conclusion: Obesity reduces the amount of inspired oxygen required to obtain a given arterial partial pressure and tissue oxygenation. Both factors probably contribute to high infection risk in obese patients. PMID:15978153

Optical fiber probe spectroscopy for laparoscopic monitoring of tissue oxygenation during esophagectomies

NASA Astrophysics Data System (ADS)

Gareau, Daniel S.; Truffer, Frederic; Perry, Kyle; Pham, Thai; Enestvedt, C. Kristian; Dolan, James; Hunter, John G.; Jacques, Steven L.

2010-11-01

Anastomotic complication is a major morbidity associated with esophagectomy. Gastric ischemia after conduit creation contributes to anastomotic complications, but a reliable method to assess oxygenation in the gastric conduit is lacking. We hypothesize that fiber optic spectroscopy can reliably assess conduit oxygenation, and that intraoperative gastric ischemia will correlate with the development of anastomotic complications. A simple optical fiber probe spectrometer is designed for nondestructive laparoscopic measurement of blood content and hemoglobin oxygen saturation in the stomach tissue microvasculature during human esophagectomies. In 22 patients, the probe measured the light transport in stomach tissue between two fibers spaced 3-mm apart (500- to 650-nm wavelength range). The stomach tissue site of measurement becomes the site of a gastroesophageal anastamosis following excision of the cancerous esophagus and surgical ligation of two of the three gastric arteries that provide blood perfusion to the anastamosis. Measurements are made at each of five steps throughout the surgery. The resting baseline saturation is 0.51+/-0.15 and decreases to 0.35+/-0.20 with ligation. Seven patients develop anastomotic complications, and a decreased saturation at either of the last two steps (completion of conduit and completion of anastamosis) is predictive of complication with a sensitivity of 0.71 when the specificity equaled 0.71.

In vivo measurement of the tissue oxygenation by time-resolved luminescence spectroscopy of protoporphyrin IX: strategies to minimize artefacts associated with photoproducts

NASA Astrophysics Data System (ADS)

Gerelli, Emmanuel; Huntosova, Veronika; Horvath, Denis; Wagnières, Georges

2017-02-01

The determination of the oxygen partial pressure (pO2) in real time in living biological tissues is of high interest for numerous therapeutics, including photodynamic therapy (PDT) and radiotherapy. The minimally invasive and real-time measurement of the pO2 also enables to obtain interesting fundamental information regarding the metabolic activities in cells and tissues. The development of time-resolved luminescence measurement (TRLM) methods combined with the availability of new oxygen-sensitive molecular probes is at the origin of the significant progress that have been achieved during these past decades to measure the pO2 in living organisms. These probes include porphyrins, such as aminolevulinic acid-induced protoporphyrin IX (PPIX), which is an approved photosensitizer. Using the photosensitizer to probe the pO2 is of high interest in PDT since the level of oxygen is measured at the precise location where the phototoxic mechanisms take place. However, PPIX has drawbacks to measure the pO2 by TRLM, including its significant photobleaching. Since the PPIX excitation during pO2 measurements leads to the generation of its photoproducts, we studied the impact of their luminescence on the measurement of the PPIX triplet state lifetime in solution and in vivo on the Chick's Chorioallantoic Membrane (CAM) model. We performed this study under various oxygen conditions. Our results indicate that perturbations induced by these photoproducts can be avoided if the PPIX luminescence is detected between 620 and 640 nm, or if PPIX is excited at 405 nm with light doses < 1 J/cm2.

Imaging of oxygen and hypoxia in cell and tissue samples.

PubMed

Papkovsky, Dmitri B; Dmitriev, Ruslan I

2018-05-14

Molecular oxygen (O 2 ) is a key player in cell mitochondrial function, redox balance and oxidative stress, normal tissue function and many common disease states. Various chemical, physical and biological methods have been proposed for measurement, real-time monitoring and imaging of O 2 concentration, state of decreased O 2 (hypoxia) and related parameters in cells and tissue. Here, we review the established and emerging optical microscopy techniques allowing to visualize O 2 levels in cells and tissue samples, mostly under in vitro and ex vivo, but also under in vivo settings. Particular examples include fluorescent hypoxia stains, fluorescent protein reporter systems, phosphorescent probes and nanosensors of different types. These techniques allow high-resolution mapping of O 2 gradients in live or post-mortem tissue, in 2D or 3D, qualitatively or quantitatively. They enable control and monitoring of oxygenation conditions and their correlation with other biomarkers of cell and tissue function. Comparison of these techniques and corresponding imaging setups, their analytical capabilities and typical applications are given.

Use of near-infrared spectroscopy (NIRS) in cerebral tissue oxygenation monitoring in neonates.

PubMed

Gumulak, Rene; Lucanova, Lucia Casnocha; Zibolen, Mirko

2017-06-01

Near-infrared spectroscopy (NIRS) is a technology capable of non-invasive, continuous measuring of regional tissue oxygen saturation (StO 2 ). StO 2 represents a state of hemodynamic stability, which is influenced by many factors. Extensive research has been done in the field of measuring StO 2 of various organs. The current clinical availability of several NIRS-based devices reflects an important development in prevention, detection and correction of discrepancy in oxygen delivery to the brain and vital organs. Managing cerebral ischemia remains a significant issue in the neonatal intensive care units (NICU). Cerebral tissue oxygenation (cStO 2 ) and cerebral fractional tissue extraction (cFTOE) are reported in a large number of clinical studies. This review provides a summary of the concept of function, current variability of NIRS-based devices used in neonatology, clinical applications in continuous cStO 2 monitoring, limitations, disadvantages, and the potential of current technology.

Combined effect of protein and oxygen on reactive oxygen and nitrogen species in the plasma treatment of tissue

NASA Astrophysics Data System (ADS)

Gaur, Nishtha; Szili, Endre J.; Oh, Jun-Seok; Hong, Sung-Ha; Michelmore, Andrew; Graves, David B.; Hatta, Akimitsu; Short, Robert D.

2015-09-01

The influence of protein and molecular, ground state oxygen (O2) on the plasma generation, and transport of reactive oxygen and nitrogen species (RONS) in tissue are investigated. A tissue target, comprising a 1 mm thick gelatin film (a surrogate for real tissue), is placed on top of a 96-well plate; each well is filled with phosphate buffered saline (PBS, pH 7.4) containing one fluorescent or colorimetric reporter that is specific for one of three RONS (i.e., H2O2, NO2-, or OH•) or a broad spectrum reactive oxygen species reporter (2,7-dichlorodihydrofluorescein). A helium cold atmospheric plasma (CAP) jet contacts the top of the gelatin surface, and the concentrations of RONS generated in PBS are measured on a microplate reader. The data show that H2O2, NO2-, or OH• are generated in PBS underneath the target. Independently, measurements are made of the O2 concentration in the PBS with and without the gelatin target. Adding bovine serum albumin protein to the PBS or gelatin shows that protein either raises or inhibits RONS depending upon the O2 concentration. Our results are discussed in the context of plasma-soft tissue interactions that are important in the development of CAP technology for medicine, biology, and food manufacturing.

Mannitol Improves Brain Tissue Oxygenation in a Model of Diffuse Traumatic Brain Injury.

PubMed

Schilte, Clotilde; Bouzat, Pierre; Millet, Anne; Boucheix, Perrine; Pernet-Gallay, Karin; Lemasson, Benjamin; Barbier, Emmanuel L; Payen, Jean-François

2015-10-01

Based on evidence supporting a potential relation between posttraumatic brain hypoxia and microcirculatory derangements with cell edema, we investigated the effects of the antiedematous agent mannitol on brain tissue oxygenation in a model of diffuse traumatic brain injury. Experimental study. Neurosciences and physiology laboratories. Adult male Wistar rats. Thirty minutes after diffuse traumatic brain injury (impact-acceleration model), rats were IV administered with either a saline solution (traumatic brain injury-saline group) or 20% mannitol (1 g/kg) (traumatic brain injury-mannitol group). Sham-saline and sham-mannitol groups received no insult. Two series of experiments were conducted 2 hours after traumatic brain injury (or equivalent) to investigate 1) the effect of mannitol on brain edema and oxygenation, using a multiparametric magnetic resonance-based approach (n = 10 rats per group) to measure the apparent diffusion coefficient, tissue oxygen saturation, mean transit time, and blood volume fraction in the cortex and caudoputamen; 2) the effect of mannitol on brain tissue PO2 and on venous oxygen saturation of the superior sagittal sinus (n = 5 rats per group); and 3) the cortical ultrastructural changes after treatment (n = 1 per group, taken from the first experiment). Compared with the sham-saline group, the traumatic brain injury-saline group had significantly lower tissue oxygen saturation, brain tissue PO2, and venous oxygen saturation of the superior sagittal sinus values concomitant with diffuse brain edema. These effects were associated with microcirculatory collapse due to astrocyte swelling. Treatment with mannitol after traumatic brain injury reversed all these effects. In the absence of traumatic brain injury, mannitol had no effect on brain oxygenation. Mean transit time and blood volume fraction were comparable between the four groups of rats. The development of posttraumatic brain edema can limit the oxygen utilization by brain tissue

Measurement of Local Partial Pressure of Oxygen in the Brain Tissue under Normoxia and Epilepsy with Phosphorescence Lifetime Microscopy

PubMed Central

Zhang, Cong; Bélanger, Samuel; Pouliot, Philippe; Lesage, Frédéric

2015-01-01

In this work a method for measuring brain oxygen partial pressure with confocal phosphorescence lifetime microscopy system is reported. When used in conjunction with a dendritic phosphorescent probe, Oxyphor G4, this system enabled minimally invasive measurements of oxygen partial pressure (pO2) in cerebral tissue with high spatial and temporal resolution during 4-AP induced epileptic seizures. Investigating epileptic events, we characterized the spatio-temporal distribution of the "initial dip" in pO2 near the probe injection site and along nearby arterioles. Our results reveal a correlation between the percent change in the pO2 signal during the "initial dip" and the duration of seizure-like activity, which can help localize the epileptic focus and predict the length of seizure. PMID:26305777

Measurement of Local Partial Pressure of Oxygen in the Brain Tissue under Normoxia and Epilepsy with Phosphorescence Lifetime Microscopy.

PubMed

Zhang, Cong; Bélanger, Samuel; Pouliot, Philippe; Lesage, Frédéric

2015-01-01

In this work a method for measuring brain oxygen partial pressure with confocal phosphorescence lifetime microscopy system is reported. When used in conjunction with a dendritic phosphorescent probe, Oxyphor G4, this system enabled minimally invasive measurements of oxygen partial pressure (pO2) in cerebral tissue with high spatial and temporal resolution during 4-AP induced epileptic seizures. Investigating epileptic events, we characterized the spatio-temporal distribution of the "initial dip" in pO2 near the probe injection site and along nearby arterioles. Our results reveal a correlation between the percent change in the pO2 signal during the "initial dip" and the duration of seizure-like activity, which can help localize the epileptic focus and predict the length of seizure.

FRET excited ratiometric oxygen sensing in living tissue

PubMed Central

Ingram, Justin M.; Zhang, Chunfeng; Xu, Jian; Schiff, Steven J.

2013-01-01

Dynamic analysis of oxygen (O2) has been limited by the lack of a real-time, quantitative, and biocompatible sensor. To address these demands, we designed a ratiometric optode matrix consisting of the phosphorescence quenching dye platinum (II) octaethylporphine ketone (PtOEPK) and nanocystal quantum dots (NQDs), which when embedded within an inert polymer matrix allows long-term pre-designed excitation through fluorescence resonance energy transfer (FRET). Depositing this matrix on various glass substrates allowed the development of a series of optical sensors able to measure interstitial oxygen concentration [O2] with several hundred millisecond temporal resolution in varying biological microdomains of active brain tissue. PMID:23333398

A method for measuring brain partial pressure of oxygen in unanesthetized unrestrained subjects: the effect of acute and chronic hypoxia on brain tissue PO(2).

PubMed

Ortiz-Prado, E; Natah, Siraj; Srinivasan, Sathyanarayanan; Dunn, Jeff F

2010-11-30

The level of tissue oxygenation provides information related to the balance between oxygen delivery, oxygen utilization, tissue reactivity and morphology during physiological conditions. Tissue partial pressure of oxygen (PtO(2)) is influenced by the use of anesthesia or restraint. These factors may impact the absolute level of PtO(2). In this study we present a novel fiber optic method to measure brain PtO(2). This method can be used in unanesthetized, unrestrained animals, provides absolute values for PO(2), has a stable calibration, does not consume oxygen and is MRI compatible. Brain PtO(2) was studied during acute hypoxia, as well as before and after 28 days of high altitude acclimatization. A sensor was chronically implanted in the frontal cortex of eight Wistar rats. It is comprised of a fiber optic probe with a tip containing material that fluoresces with an oxygen dependent lifetime. Brain PtO(2) declines by 80% and 76% pre- and post-acclimatization, respectively, when the fraction of inspired oxygen declines from 0.21 to 0.08. In addition, a linear relationship between brain PtO(2) and inspired O(2) levels was demonstrated r(2)=0.98 and r(2)=0.99 (pre- and post-acclimatization). Hypoxia acclimatization resulted in an increase in the overall brain PtO(2) by approximately 35%. This paper demonstrates the use of a novel chronically implanted fiber optic based sensor for measuring absolute PtO(2). It shows a very strong linear relationship in awake animals between inspired O(2) and tissue O(2), and shows that there is a proportional increase in PtO(2) over a range of inspired values after exposure to chronic hypoxia. Copyright © 2010 Elsevier B.V. All rights reserved.

A validation method for near-infrared spectroscopy based tissue oximeters for cerebral and somatic tissue oxygen saturation measurements.

PubMed

Benni, Paul B; MacLeod, David; Ikeda, Keita; Lin, Hung-Mo

2018-04-01

We describe the validation methodology for the NIRS based FORE-SIGHT ELITE ® (CAS Medical Systems, Inc., Branford, CT, USA) tissue oximeter for cerebral and somatic tissue oxygen saturation (StO 2 ) measurements for adult subjects submitted to the United States Food and Drug Administration (FDA) to obtain clearance for clinical use. This validation methodology evolved from a history of NIRS validations in the literature and FDA recommended use of Deming regression and bootstrapping statistical validation methods. For cerebral validation, forehead cerebral StO 2 measurements were compared to a weighted 70:30 reference (REF CX B ) of co-oximeter internal jugular venous and arterial blood saturation of healthy adult subjects during a controlled hypoxia sequence, with a sensor placed on the forehead. For somatic validation, somatic StO 2 measurements were compared to a weighted 70:30 reference (REF CX S ) of co-oximetry central venous and arterial saturation values following a similar protocol, with sensors place on the flank, quadriceps muscle, and calf muscle. With informed consent, 25 subjects successfully completed the cerebral validation study. The bias and precision (1 SD) of cerebral StO 2 compared to REF CX B was -0.14 ± 3.07%. With informed consent, 24 subjects successfully completed the somatic validation study. The bias and precision of somatic StO 2 compared to REF CX S was 0.04 ± 4.22% from the average of flank, quadriceps, and calf StO 2 measurements to best represent the global whole body REF CX S . The NIRS validation methods presented potentially provide a reliable means to test NIRS monitors and qualify them for clinical use.

Quantification of tissue oxygenation levels using diffuse reflectance spectroscopy

NASA Astrophysics Data System (ADS)

B. S., Suresh Anand; N., Sujatha

2011-08-01

Tumor growth is characterized by increased metabolic activity. The light absorption profile of hemoglobin in dysplastic tissue is different from a normal tissue. Neovascularization is a hallmark of many diseases and can serve as a predictive biomarker for the detection of cancers. Spectroscopic techniques can provide information about the metabolic and morphological changes related to the progression of neoplasia. Diffuse reflectance spectroscopy (DRS) measures the absorption and scattering properties of a biological tissue and this method can provide clinically useful information for the early diagnosis of epithelial precancers. We used tissue simulating phantoms with absorbing and scattering molecules for the determination of total hemoglobin concentration, hemoglobin oxygen saturation and intensity difference between the deoxy and oxy hemoglobin bands. The results show promising approach for the differentiating normal and malignant states of a tissue.

Noninvasive Intracranial Pressure and Tissue Oxygen Measurements for Space and Earth

NASA Technical Reports Server (NTRS)

Hargens, A. R.; Ballard, R. E.; Murthy, G.; Watenpaugh, D. E.

1994-01-01

The paper discusses the following: Increasing intracranial pressure in humans during simulated microgravity. and near-infrared monitoring of model chronic compartment syndrome in exercising skeletal muscle. Compared to upright-seated posture, 0 deg. supine, 6 deg. HDT, and 15 deg. HDT produced TMD changes of 317 +/- 112, 403 +/- 114, and 474 +/- 112 n1 (means +/- S.E.), respectively. Furthermore, postural transitions from 0 deg. supine to 6 deg. HDT and from 6 deg. to 15 deg. HDT generated significant TMD changes (p less than 0.05). There was no hysteresis when postural transitions to HDT were compared to reciprocal transitions toward upright seated posture. Currently, diagnosis of chronic compartment syndrome (CCS) depends on measurement of intramuscular pressure by invasive catheterization. We hypothesized that this syndrome can be detected noninvasively by near-infrared (NIR) spectroscopy, which tracks variations in muscle hemoglobin/myoglobin oxygen saturation. CCS was simulated in the tibialis anterior muscle of 7 male and 3 female subjects by gradual inflation of a cuff placed around the leg to 40 mmHg during 14 minutes of cyclic isokinetic dorsiflexion exercise. On a separate day, subjects underwent the identical exercise protocol with no external compression. In both cases, tissue oxygenation (T(sub O2) was measured in the tibialis anterior by NIR spectroscopy and normalized to a percentage scale between baseline and a T(sub O2) nadir reached during exercise to ischemic exhaustion. Over the course of exercise, T(sub O2) declined at a rate of 1.4 +/- 0.3% per minute with model CCS, yet did not decrease during control exercise. Post-exercise recovery of T(sub O2) was slower with model CCS (2.5 +/- 0.6 min) than in control (1.3 +/- 0.2 min). These results demonstrate that NIR spectroscopy can detect muscle deoxygenation caused by pathologically elevated intramuscular pressure in exercising skeletal muscle. Consequently, this technique shows promise as a

Oxygen mapping: Probing a novel seeding strategy for bone tissue engineering.

PubMed

Westphal, Ines; Jedelhauser, Claudia; Liebsch, Gregor; Wilhelmi, Arnd; Aszodi, Attila; Schieker, Matthias

2017-04-01

Bone tissue engineering (BTE) utilizing biomaterial scaffolds and human mesenchymal stem cells (hMSCs) is a promising approach for the treatment of bone defects. The quality of engineered tissue is crucially affected by numerous parameters including cell density and the oxygen supply. In this study, a novel oxygen-imaging sensor was introduced to monitor the oxygen distribution in three dimensional (3D) scaffolds in order to analyze a new cell-seeding strategy. Immortalized hMSCs, pre-cultured in a monolayer for 30-40% or 70-80% confluence, were used to seed demineralized bone matrix (DBM) scaffolds. Real-time measurements of oxygen consumption in vitro were simultaneously performed by the novel planar sensor and a conventional needle-type sensor over 24 h. Recorded oxygen maps of the novel planar sensor revealed that scaffolds, seeded with hMSCs harvested at lower densities (30-40% confluence), exhibited rapid exponential oxygen consumption profile. In contrast, harvesting cells at higher densities (70-80% confluence) resulted in a very slow, almost linear, oxygen decrease due to gradual achieving the stationary growth phase. In conclusion, it could be shown that not only the seeding density on a scaffold, but also the cell density at the time point of harvest is of major importance for BTE. The new cell seeding strategy of harvested MSCs at low density during its log phase could be a useful strategy for an early in vivo implantation of cell-seeded scaffolds after a shorter in vitro culture period. Furthermore, the novel oxygen imaging sensor enables a continuous, two-dimensional, quick and convenient to handle oxygen mapping for the development and optimization of tissue engineered scaffolds. Biotechnol. Bioeng. 2017;114: 894-902. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Comparison of local adipose tissue content and SRS-derived NIRS muscle oxygenation measurements in 90 individuals.

PubMed

Cooper, Chris E; Penfold, Stacey-Marie; Elwell, Clare E; Angus, Caroline

2010-01-01

Adipose content in the region over the vastus lateralis muscle was measured in a young (21.1 +/- 3.1 years old, mean +/- SD) population of males (n = 62) and females (n = 28). Three techniques were used: skinfold thickness, ultrasound and near infrared spectroscopy. All techniques closely correlated with each other and all showed a significantly larger adipose content in females and a limited overlap with the range of values in males. Spatially resolved near infrared spectroscopy (SRS-NIRS) was then used to measure the tissue oxygenation index (TOI) at the same site. A source-detector separation of 4 cm was used to allow for significant light penetration into muscle tissue. TOI at rest was significantly higher in the female (65.3 +/- 7.0, mean +/- SD) than the male (61.9 +/- 5.1, mean +/- SD) group. There was a strong positive correlation between adipose content and TOI in male subjects. However, no correlation was seen in the female group. The possible optical and physiological explanations for these results are discussed.

[Several indicators of tissue oxygen during modeling of extravehicular activity of man].

PubMed

Lan'shina, O E; Loginov, V A; Akinfiev, A V; Kovalenko, E A

1995-01-01

Investigations of tissue oxygen indices during simulation of extravehicular activity (EVA) of cosmonauts demonstrated that breathing pure oxygen at approximately 280 mmHg elevates oxygen tension in capillary blood, and capillary-tissue gradient during physical work. Physical work alone stimulates tissue oxygenation due to, apparently, intensification of the processes of oxidative phosphorylation. The observed shifts in oxygen status reverse significantly within the first 5 min after completion of the experiment.

Study of tissue oxygen supply rate in a macroscopic photodynamic therapy singlet oxygen model

NASA Astrophysics Data System (ADS)

Zhu, Timothy C.; Liu, Baochang; Penjweini, Rozhin

2015-03-01

An appropriate expression for the oxygen supply rate (Γs) is required for the macroscopic modeling of the complex mechanisms of photodynamic therapy (PDT). It is unrealistic to model the actual heterogeneous tumor microvascular networks coupled with the PDT processes because of the large computational requirement. In this study, a theoretical microscopic model based on uniformly distributed Krogh cylinders is used to calculate Γs=g (1-[O]/[]0) that can replace the complex modeling of blood vasculature while maintaining a reasonable resemblance to reality; g is the maximum oxygen supply rate and [O]/[]0 is the volume-average tissue oxygen concentration normalized to its value prior to PDT. The model incorporates kinetic equations of oxygen diffusion and convection within capillaries and oxygen saturation from oxyhemoglobin. Oxygen supply to the tissue is via diffusion from the uniformly distributed blood vessels. Oxygen can also diffuse along the radius and the longitudinal axis of the cylinder within tissue. The relations of Γs to [3O2]/] are examined for a biologically reasonable range of the physiological parameters for the microvasculature and several light fluence rates (ϕ). The results show a linear relationship between Γs and [3O2]/], independent of ϕ and photochemical parameters; the obtained g ranges from 0.4 to 1390 μM/s.

In vivo preclinical cancer and tissue engineering applications of absolute oxygen imaging using pulse EPR

NASA Astrophysics Data System (ADS)

Epel, Boris; Kotecha, Mrignayani; Halpern, Howard J.

2017-07-01

The value of any measurement and a fortiori any measurement technology is defined by the reproducibility and the accuracy of the measurements. This implies a relative freedom of the measurement from factors confounding its accuracy. In the past, one of the reasons for the loss of focus on the importance of imaging oxygen in vivo was the difficulty in obtaining reproducible oxygen or pO2 images free from confounding variation. This review will briefly consider principles of electron paramagnetic oxygen imaging and describe how it achieves absolute oxygen measurements. We will provide a summary review of the progress in biomedical EPR imaging, predominantly in cancer biology research, discuss EPR oxygen imaging for cancer treatment and tissue graft assessment for regenerative medicine applications.

Feasibility of absolute cerebral tissue oxygen saturation during cardiopulmonary resuscitation.

PubMed

Meex, Ingrid; De Deyne, Cathy; Dens, Jo; Scheyltjens, Simon; Lathouwers, Kevin; Boer, Willem; Vundelinckx, Guy; Heylen, René; Jans, Frank

2013-03-01

Current monitoring during cardiopulmonary resuscitation (CPR) is limited to clinical observation of consciousness, breathing pattern and presence of a pulse. At the same time, the adequacy of cerebral oxygenation during CPR is critical for neurological outcome and thus survival. Cerebral oximetry, based on near-infrared spectroscopy (NIRS), provides a measure of brain oxygen saturation. Therefore, we examined the feasibility of using NIRS during CPR. Recent technologies (FORE-SIGHT™ and EQUANOX™) enable the monitoring of absolute cerebral tissue oxygen saturation (SctO2) values without the need for pre-calibration. We tested both FORE-SIGHT™ (five patients) and EQUANOX Advance™ (nine patients) technologies in the in-hospital as well as the out-of-hospital CPR setting. In this observational study, values were not utilized in any treatment protocol or therapeutic decision. An independent t-test was used for statistical analysis. Our data demonstrate the feasibility of both technologies to measure cerebral oxygen saturation during CPR. With the continuous, pulseless near-infrared wave analysis of both FORE-SIGHT™ and EQUANOX™ technology, we obtained SctO2 values in the absence of spontaneous circulation. Both technologies were able to assess the efficacy of CPR efforts: improved resuscitation efforts (improved quality of chest compressions with switch of caregivers) resulted in higher SctO2 values. Until now, the ability of CPR to provide adequate tissue oxygenation was difficult to quantify or to assess clinically due to a lack of specific technology. With both technologies, any change in hemodynamics (for example, ventricular fibrillation) results in a reciprocal change in SctO2. In some patients, a sudden drop in SctO2 was the first warning sign of reoccurring ventricular fibrillation. Both the FORE-SIGHT™ and EQUANOX™ technology allow non-invasive monitoring of the cerebral oxygen saturation during CPR. Moreover, changes in SctO2 values might be

Association of intraoperative tissue oxygenation with suspected risk factors for tissue hypoxia.

PubMed

Spruit, R J; Schwarte, L A; Hakenberg, O W; Scheeren, T W L

2013-10-01

Tissue hypoxia may cause organ dysfunction, but not much is known about tissue oxygenation in the intraoperative setting. We studied microcirculatory tissue oxygen saturation (StO₂) to determine representative values for anesthetized patients undergoing urological surgery and to test the hypothesis that StO₂ is associated with known perioperative risk factors for morbidity and mortality, conventionally monitored variables, and hypotension requiring norepinephrine. Using near-infrared spectroscopy, we measured StO₂ on the thenar eminence in 160 patients undergoing open urological surgery under general anesthesia (FiO2 0.35-0.4), and calculated its correlations with age, risk level for general perioperative complications and mortality (high if age ≥70 and procedure is radical cystectomy), mean arterial pressure (MAP), hemoglobin concentration (Hb), central venous oxygen saturation (ScvO₂), and norepinephrine use. The time averaged StO₂ was 86 ± 6 % (mean ± SD). In the multivariate analysis, Hb [standardized coefficient (SC) 0.21, p = 0.003], ScvO₂ (SC 0.53, p < 0.001) and high risk level (SC 0.06, p = 0.03) were significant independent variables correlated with StO₂. SStO₂ was partly dependent on MAP only when this was below 65 mmHg (lowest MAP SC 0.20, p = 0.006, MAP area under the curve <65 mmHg SC 0.03, p = 0.02). Finally, StO₂ was slightly lower in patients requiring norepinephrine (85 ± 6 vs. 89 ± 6 %, p = 0.001). Intraoperative StO₂ in urological patients was comparable to that of healthy volunteers breathing room air as reported in the literature and correlated with known perioperative risk factors. Further research should investigate its association with outcome and the effect of interventions aimed at optimizing StO₂.

Real-time quantitation of internal metabolic activity of three-dimensional engineered tissues using an oxygen microelectrode and optical coherence tomography.

PubMed

Kagawa, Yuki; Haraguchi, Yuji; Tsuneda, Satoshi; Shimizu, Tatsuya

2017-05-01

Recent progress in tissue engineering technology has enabled us to develop thick tissue constructs that can then be transplanted in regenerative therapies. In clinical situations, it is vital that the engineered tissues to be implanted are safe and functional before use. However, there is currently a limited number of studies on real-time quality evaluation of thick living tissue constructs. Here we developed a system for quantifying the internal activities of engineered tissues, from which we can evaluate its quality in real-time. The evaluation was achieved by measuring oxygen concentration profiles made along the vertical axis and the thickness of the tissues estimated from cross-sectional images obtained noninvasively by an optical coherence tomography system. Using our novel system, we obtained (i) oxygen concentration just above the tissues, (ii) gradient of oxygen along vertical axis formed above the tissues within culture medium, and (iii) gradient of oxygen formed within the tissues in real-time. Investigating whether these three parameters could be used to evaluate engineered tissues during culturing, we found that only the third parameter was a good candidate. This implies that the activity of living engineered tissues can be monitored in real-time by measuring the oxygen gradient within the tissues. The proposed measuring strategy can be applied to developing more efficient culturing methods to support the fabrication of engineered thick tissues, as well as providing methods to confirm the quality in real-time. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 855-864, 2017. © 2015 Wiley Periodicals, Inc.

Characterization of Adipose Tissue Product Quality Using Measurements of Oxygen Consumption Rate.

PubMed

Suszynski, Thomas M; Sieber, David A; Mueller, Kathryn; Van Beek, Allen L; Cunningham, Bruce L; Kenkel, Jeffrey M

2018-03-14

Fat grafting is a common procedure in plastic surgery but associated with unpredictable graft retention. Adipose tissue (AT) "product" quality is affected by the methods used for harvest, processing and transfer, which vary widely amongst surgeons. Currently, there is no method available to accurately assess the quality of AT. In this study, we present a novel method for the assessment of AT product quality through direct measurements of oxygen consumption rate (OCR). OCR has exhibited potential in predicting outcomes following pancreatic islet transplant. Our study aim was to reapportion existing technology for its use with AT preparations and to confirm that these measurements are feasible. OCR was successfully measured for en bloc and postprocessed AT using a stirred microchamber system. OCR was then normalized to DNA content (OCR/DNA), which represents the AT product quality. Mean (±SE) OCR/DNA values for fresh en bloc and post-processed AT were 149.8 (± 9.1) and 61.1 (± 6.1) nmol/min/mg DNA, respectively. These preliminary data suggest that: (1) OCR and OCR/DNA measurements of AT harvested using conventional protocol are feasible; and (2) standard AT processing results in a decrease in overall AT product quality. OCR measurements of AT using existing technology can be done and enables accurate, real-time, quantitative assessment of the quality of AT product prior to transfer. The availability and further validation of this type of assay could enable optimization of fat grafting protocol by providing a tool for the more detailed study of procedural variables that affect AT product quality.

Analysis of healthy sitting behavior: interface pressure distribution and subcutaneous tissue oxygenation.

PubMed

Reenalda, Jasper; Van Geffen, Paul; Nederhand, Marc; Jannink, Michiel; IJzerman, Maarten; Rietman, Hans

2009-01-01

Pressure ulcers are a large problem in individuals who use a wheelchair for their mobility and have limited trunk stability and motor function. Because no relation between interface pressure and pressure ulcer development has been established and no clinical threshold for pressure ulcer development can be given, looking at the sitting behavior of nondisabled individuals is important. Nondisabled individuals do not develop pressure ulcers because they continuously shift posture. We analyzed the sitting behavior of 25 nondisabled male subjects by using a combination of interface pressure measurement and subcutaneous tissue oxygenation measurement by means of the Oxygen to See. These subjects shifted posture on average 7.8 +/- 5.2 times an hour. These posture shifts were merely a combination of posture shifts in the frontal and sagittal plane. Subcutaneous oxygen saturation increased on average 2.2% with each posture adjustment, indicating a positive effect of posture shifts on tissue viability. The results of this study can be used as a reference for seating interventions aimed at preventing pressure ulcers. Changing the sitting load at least every 8 minutes is recommended for wheelchair users.

Longitudinal In Vivo Imaging to Assess Blood Flow and Oxygenation in Implantable Engineered Tissues

PubMed Central

White, Sean M.; Hingorani, Ryan; Arora, Rajan P.S.; Hughes, Christopher C.W.; George, Steven C.

2012-01-01

The functionality of vascular networks within implanted prevascularized tissues is difficult to assess using traditional analysis techniques, such as histology. This is largely due to the inability to visualize hemodynamics in vivo longitudinally. Therefore, we have developed dynamic imaging methods to measure blood flow and hemoglobin oxygen saturation in implanted prevascularized tissues noninvasively and longitudinally. Using laser speckle imaging, multispectral imaging, and intravital microscopy, we demonstrate that fibrin-based tissue implants anastomose with the host (severe combined immunodeficient mice) in as short as 20 h. Anastomosis results in initial perfusion with highly oxygenated blood, and an increase in average hemoglobin oxygenation of 53%. However, shear rates in the preformed vessels were low (20.8±12.8 s−1), and flow did not persist in the vast majority of preformed vessels due to thrombus formation. These findings suggest that designing an appropriate vascular network structure in prevascularized tissues to maintain shear rates above the threshold for thrombosis may be necessary to maintain flow following implantation. We conclude that wide-field and microscopic functional imaging can dynamically assess blood flow and oxygenation in vivo in prevascularized tissues, and can be used to rapidly evaluate and improve prevascularization strategies. PMID:22435776

A method for monitoring of oxygen saturation changes in brain tissue using diffuse reflectance spectroscopy.

PubMed

Rejmstad, Peter; Johansson, Johannes D; Haj-Hosseini, Neda; Wårdell, Karin

2017-03-01

Continuous measurement of local brain oxygen saturation (SO 2 ) can be used to monitor the status of brain trauma patients in the neurocritical care unit. Currently, micro-oxygen-electrodes are considered as the "gold standard" in measuring cerebral oxygen pressure (pO 2 ), which is closely related to SO 2 through the oxygen dissociation curve (ODC) of hemoglobin, but with the drawback of slow in response time. The present study suggests estimation of SO 2 in brain tissue using diffuse reflectance spectroscopy (DRS) for finding an analytical relation between measured spectra and the SO 2 for different blood concentrations. The P 3 diffusion approximation is used to generate a set of spectra simulating brain tissue for various levels of blood concentrations in order to estimate SO 2 . The algorithm is evaluated on optical phantoms mimicking white brain matter (blood volume of 0.5-2%) where pO 2 and temperature is controlled and on clinical data collected during brain surgery. The suggested method is capable of estimating the blood fraction and oxygen saturation changes from the spectroscopic signal and the hemoglobin absorption profile. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Validation of oxygen extraction fraction measurement by qBOLD technique.

PubMed

He, Xiang; Zhu, Mingming; Yablonskiy, Dmitriy A

2008-10-01

Measurement of brain tissue oxygen extraction fraction (OEF) in both baseline and functionally activated states can provide important information on brain functioning in health and disease. The recently proposed quantitative BOLD (qBOLD) technique is MRI-based and provides a regional in vivo OEF measurement (He and Yablonskiy, MRM 2007, 57:115-126). It is based on a previously developed analytical BOLD model and incorporates prior knowledge about the brain tissue composition including the contributions from grey matter, white matter, cerebrospinal fluid, interstitial fluid and intravascular blood. The qBOLD model also allows for the separation of contributions to the BOLD signal from OEF and the deoxyhemoglobin containing blood volume (DBV). The objective of this study is to validate OEF measurements provided by the qBOLD approach. To this end we use a rat model and compare qBOLD OEF measurements against direct measurements of the blood oxygenation level obtained from venous blood drawn directly from the superior sagittal sinus. The cerebral venous oxygenation level of the rat was manipulated by utilizing different anestheisa methods. The study demonstrates a very good agreement between qBOLD approach and direct measurements. (c) 2008 Wiley-Liss, Inc.

A Highly Sensitive Biocompatible Spin Probe for Imaging of Oxygen Concentration in Tissues

PubMed Central

Bratasz, Anna; Kulkarni, Aditi C.; Kuppusamy, Periannan

2007-01-01

The development of an injectable probe formulation, consisting of perchlorotriphenylmethyl triester radical dissolved in hexafluorobenzene, for in vivo oximetry and imaging of oxygen concentration in tissues using electron paramagnetic resonance (EPR) imaging is reported. The probe was evaluated for its oxygen sensitivity, biostability, and distribution in a radiation-induced fibrosarcoma tumor transplanted into C3H mice. Some of the favorable features of the probe are: a single narrow EPR peak (anoxic linewidth, 41 μT), high solubility in hexafluorobenzene (>12 mM), large linewidth sensitivity to molecular oxygen (∼1.8 μT/mmHg), good stability in tumor tissue (half-life: 3.3 h), absence of spin-spin broadening (up to 12 mM), and lack of power saturation effects (up to 200 mW). Three-dimensional spatial and spectral-spatial (spectroscopic) EPR imaging measurements were used to visualize the distribution of the probe, as well as to obtain spatially resolved pO2 information in the mice tumor subjected to normoxic and hyperoxic treatments. The new probe should enable unique opportunities for measurement of the oxygen concentration in tumors using EPR methods. PMID:17259268

Tissue oxygen demand in regulation of the behavior of the cells in the vasculature.

PubMed

Barvitenko, Nadezhda N; Aslam, Muhammad; Filosa, Jessica; Matteucci, Elena; Nikinmaa, Mikko; Pantaleo, Antonella; Saldanha, Carlota; Baskurt, Oguz K

2013-08-01

The control of arteriolar diameters in microvasculature has been in the focus of studies on mechanisms matching oxygen demand and supply at the tissue level. Functionally, important vascular elements include EC, VSMC, and RBC. Integration of these different cell types into functional units aimed at matching tissue oxygen supply with tissue oxygen demand is only achieved when all these cells can respond to the signals of tissue oxygen demand. Many vasoactive agents that serve as signals of tissue oxygen demand have their receptors on all these types of cells (VSMC, EC, and RBC) implying that there can be a coordinated regulation of their behavior by the tissue oxygen demand. Such functions of RBC as oxygen carrying by Hb, rheology, and release of vasoactive agents are considered. Several common extra- and intracellular signaling pathways that link tissue oxygen demand with control of VSMC contractility, EC permeability, and RBC functioning are discussed. © 2013 John Wiley & Sons Ltd.

Determination of oxygen tension in the subcutaneous tissue of cosmonauts during the Salyut-6 mission

NASA Technical Reports Server (NTRS)

Baranski, S.; Bloszczynski, R.; Hermaszewski, M.; Kubiczkowa, J.; Piorko, A.; Saganiak, R.; Sarol, Z.; Skibniewsky, F.; Stendera, J.; Walichnowski, W.

1982-01-01

A polarographic technique was used to measure the oxygen tension in subcutaneous tissue of the forearm of a cosmonaut prior to, after, and on the fourth day of a space mission performed by Salut-6. A drop in the oxygen exchange rate in the peripheral tissues during weightlessness was observed. The mechanisms of this change are studied, taking into consideration the blood distribution in the organism and microcirculation disorders reflected by a decreased blood flow rate in arterial-venous junctions.

Increased tissue oxygenation explains the attenuation of hyperemia upon repetitive pneumatic compression of the lower leg.

PubMed

Messere, Alessandro; Ceravolo, Gianluca; Franco, Walter; Maffiodo, Daniela; Ferraresi, Carlo; Roatta, Silvestro

2017-12-01

The rapid hyperemia evoked by muscle compression is short lived and was recently shown to undergo a rapid decrease even in spite of continuing mechanical stimulation. The present study aims at investigating the mechanisms underlying this attenuation, which include local metabolic mechanisms, desensitization of mechanosensitive pathways, and reduced efficacy of the muscle pump. In 10 healthy subjects, short sequences of mechanical compressions ( n = 3-6; 150 mmHg) of the lower leg were delivered at different interstimulus intervals (ranging from 20 to 160 s) through a customized pneumatic device. Hemodynamic monitoring included near-infrared spectroscopy, detecting tissue oxygenation and blood volume in calf muscles, and simultaneous echo-Doppler measurement of arterial (superficial femoral artery) and venous (femoral vein) blood flow. The results indicate that 1 ) a long-lasting (>100 s) increase in local tissue oxygenation follows compression-induced hyperemia, 2 ) compression-induced hyperemia exhibits different patterns of attenuation depending on the interstimulus interval, 3 ) the amplitude of the hyperemia is not correlated with the amount of blood volume displaced by the compression, and 4 ) the extent of attenuation negatively correlates with tissue oxygenation ( r  = -0,78, P < 0.05). Increased tissue oxygenation appears to be the key factor for the attenuation of hyperemia upon repetitive compressive stimulation. Tissue oxygenation monitoring is suggested as a useful integration in medical treatments aimed at improving local circulation by repetitive tissue compression. NEW & NOTEWORTHY This study shows that 1 ) the hyperemia induced by muscle compression produces a long-lasting increase in tissue oxygenation, 2 ) the hyperemia produced by subsequent muscle compressions exhibits different patterns of attenuation at different interstimulus intervals, and 3 ) the extent of attenuation of the compression-induced hyperemia is proportional to the level of

Determination of optical properties, drug concentration, and tissue oxygenation in human pleural tissue before and after Photofrin-mediated photodynamic therapy

NASA Astrophysics Data System (ADS)

Ong, Yi Hong; Padawer-Curry, Jonah; Finlay, Jarod C.; Kim, Michele M.; Dimofte, Andreea; Cengel, Keith; Zhu, Timothy C.

2018-02-01

PDT efficacy depends on the concentration of photosensitizer, oxygen, and light delivery in patient tissues. In this study, we measure the in-vivo distribution of important dosimetric parameters, namely the tissue optical properties (absorption μa (λ) and scattering μs ' (λ) coefficients), photofrin concentration (cphotofrin), blood oxygen saturation (%StO2), and total hemoglobin concentration (THC), before and after PDT. We characterize the inter- and intra-patient heterogeneity of these quantities and explore how these properties change as a result of PDT treatment. The result suggests the need for real-time dosimetry during PDT to optimize the treatment condition depending on the optical and physiological properties.

Cerebral arterial oxygen saturation measurements using a fiber-optic pulse oximeter.

PubMed

Phillips, J P; Langford, R M; Chang, S H; Maney, K; Kyriacou, P A; Jones, D P

2010-10-01

A pilot investigation was undertaken to assess the performance of a novel fiber-optic cerebral pulse oximetry system. A fiber-optic probe designed to pass through the lumen of a cranial bolt of the type used to make intracranial pressure measurements was used to obtain optical reflectance signals directly from brain tissue. Short-duration measurements were made in six patients undergoing neurosurgery. These were followed by a longer duration measurement in a patient recovering from an intracerebral hematoma. Estimations of cerebral arterial oxygen saturation derived from a frequency domain-based algorithm are compared with simultaneous pulse oximetry (SpO2) and hemoximeter (SaO2) blood samples. The short-duration measurements showed that reliable photoplethysmographic signals could be obtained from the brain tissue. In the long-duration study, the mean (±SD) difference between cerebral oxygen saturation (ScaO2) and finger SpO2 (in saturation units) was -7.47(±3.4)%. The mean (±SD) difference between ScaO2 and blood SaO2 was -7.37(±2.8)%. This pilot study demonstrated that arterial oxygen saturation may be estimated from brain tissue via a fiber-optic pulse oximeter used in conjunction with a cranial bolt. Further studies are needed to confirm the clinical utility of the technique.

Reference ranges for regional cerebral tissue oxygen saturation and fractional oxygen extraction in neonates during immediate transition after birth.

PubMed

Pichler, Gerhard; Binder, Corinna; Avian, Alexander; Beckenbach, Elisabeth; Schmölzer, Georg M; Urlesberger, Berndt

2013-12-01

To define reference ranges for regional cerebral tissue oxygen saturation (crSO2) and regional cerebral fractional tissue oxygen extraction (cFTOE) during the first 15 minutes after birth in neonates requiring no medical support. The crSO2 was measured using near infrared spectroscopy (Invos 5100 cerebral/somatic oximeter monitor; Somanetics Corp, Troy, Michigan) during the first 15 minutes after birth for term and preterm neonates. The near infrared spectroscopy sensor was placed on the left forehead. Peripheral oxygen saturation and heart rate were continuously measured by pulse oximetry, and cFTOE was calculated. Neonates were excluded if they required any medical support. A total of 381 neonates were included: 82 term neonates after vaginal delivery, 272 term neonates after cesarean delivery, and 27 preterm neonates after cesarean delivery. In all neonates, median (10th-90th percentiles) crSO2 was 41% (23-64) at 2 minutes, 68% (45-85) at 5 minutes, 79% (65-90) at 10 minutes, and 77% (63-89) at 15 minutes of age. In all neonates, median (10th-90th percentiles) cFTOE was 33% (11-70) at 2 minutes, 21% (6-45) at 5 minutes, 15% (5-31) at 10 minutes, and 18% (7-34) at 15 minutes of age. We report reference ranges of crSO2 and cFTOE in neonates requiring no medical support during transition immediately after birth. The use of cerebral oxygenation monitoring and use of these reference ranges in neonates during transition may help to guide oxygen delivery and avoid cerebral hypo-oxygenation and hyperoxygenation. Copyright © 2013 Mosby, Inc. All rights reserved.

Oxygen and tissue culture affect placental gene expression.

PubMed

Brew, O; Sullivan, M H F

2017-07-01

Placental explant culture is an important model for studying placental development and functions. We investigated the differences in placental gene expression in response to tissue culture, atmospheric and physiologic oxygen concentrations. Placental explants were collected from normal term (38-39 weeks of gestation) placentae with no previous uterine contractile activity. Placental transcriptomic expressions were evaluated with GeneChip ® Human Genome U133 Plus 2.0 arrays (Affymetrix). We uncovered sub-sets of genes that regulate response to stress, induction of apoptosis programmed cell death, mis-regulation of cell growth, proliferation, cell morphogenesis, tissue viability, and protection from apoptosis in cultured placental explants. We also identified a sub-set of genes with highly unstable pattern of expression after exposure to tissue culture. Tissue culture irrespective of oxygen concentration induced dichotomous increase in significant gene expression and increased enrichment of significant pathways and transcription factor targets (TFTs) including HIF1A. The effect was exacerbated by culture at atmospheric oxygen concentration, where further up-regulation of TFTs including PPARA, CEBPD, HOXA9 and down-regulated TFTs such as JUND/FOS suggest intrinsic heightened key biological and metabolic mechanisms such as glucose use, lipid biosynthesis, protein metabolism; apoptosis, inflammatory responses; and diminished trophoblast proliferation, differentiation, invasion, regeneration, and viability. These findings demonstrate that gene expression patterns differ between pre-culture and cultured explants, and the gene expression of explants cultured at atmospheric oxygen concentration favours stressed, pro-inflammatory and increased apoptotic transcriptomic response. Copyright © 2017 Elsevier Ltd. All rights reserved.

Evaluation of different near-infrared spectroscopy technologies for assessment of tissue oxygen saturation during a vascular occlusion test.

PubMed

Steenhaut, Kevin; Lapage, Koen; Bové, Thierry; De Hert, Stefan; Moerman, Annelies

2017-12-01

An increasing number of NIRS devices are used to provide measurements of peripheral tissue oxygen saturation (S t O 2 ). The aim of the present study is to test the hypothesis that despite technological differences between devices, similar trend values will be obtained during a vascular occlusion test. The devices compared are NIRO-200NX, which measures S t O 2 and oxyhemoglobin by spatially resolved spectroscopy and the Beer-Lambert law, respectively, and INVOS 5100C and Foresight Elite, which both measure S t O 2 with the Beer-Lambert law, enhanced with the spatial resolution technique. Forty consenting adults scheduled for CABG surgery were recruited. The respective sensors of the three NIRS devices were applied over the brachioradial muscle. Before induction of anesthesia, 3 min of ischemia were induced by inflating a blood pressure cuff at the upper arm, whereafter cuff pressure was rapidly released. Tissue oxygenation measurements included baseline, minimum and maximum values, desaturation and resaturation slopes, and rise time. Comparisons between devices were performed with the Kruskal-Wallis test with post hoc Mann-Whitney pairwise comparisons. Agreement was evaluated using Bland-Altman plots. Oxyhemoglobin measured with NIRO responded faster than the other NIRS technologies to changes in peripheral tissue oxygenation (20 vs. 27-40 s, p ≤ 0.01). When comparing INVOS with Foresight, oxygenation changes were prompter (upslope 311 [92-523]%/min vs. 114[65-199]%/min, p ≤ 0.01) and more pronounced (minimum value 36 [21-48] vs. 45 [40-51]%, p ≤ 0.01) with INVOS. Significant differences in tissue oxygen saturation measurements were observed, both within the same device as between different devices using the same measurement technology.

Perioperative Near-Infrared Spectroscopy Monitoring in Neonates With Congenital Heart Disease: Relationship of Cerebral Tissue Oxygenation Index Variability With Neurodevelopmental Outcome.

PubMed

Spaeder, Michael C; Klugman, Darren; Skurow-Todd, Kami; Glass, Penny; Jonas, Richard A; Donofrio, Mary T

2017-03-01

To evaluate the value of perioperative cerebral near-infrared spectroscopy monitoring using variability analysis in the prediction of neurodevelopmental outcomes in neonates undergoing surgery for congenital heart disease. Retrospective cohort study. Urban, academic, tertiary-care children's hospital. Neonates undergoing surgery with cardiopulmonary bypass for congenital heart disease. Perioperative monitoring of continuous cerebral tissue oxygenation index by near-infrared spectroscopy and subsequent neurodevelopmental testing at 6, 15, and 21 months of age. We developed a new measure, cerebral tissue oxygenation index variability, using the root mean of successive squared differences of averaged 1-minute cerebral tissue oxygenation index values for both the intraoperative and first 24-hours postoperative phases of monitoring. There were 62 neonates who underwent cerebral tissue oxygenation index monitoring during surgery for congenital heart disease and 44 underwent subsequent neurodevelopmental testing (12 did not survive until testing and six were lost to follow-up). Among the 44 monitored patients who underwent neurodevelopmental testing, 20 (45%) had abnormal neurodevelopmental indices. Patients with abnormal neurodevelopmental indices had lower postoperative cerebral tissue oxygenation index variability when compared with patients with normal indices (p = 0.01). Adjusting for class of congenital heart disease and duration of deep hypothermic circulatory arrest, lower postoperative cerebral tissue oxygenation index variability was associated with poor neurodevelopmental outcome (p = 0.02). We found reduced postoperative cerebral tissue oxygenation index variability in neonatal survivors of congenital heart disease surgery with poor neurodevelopmental outcomes. We hypothesize that reduced cerebral tissue oxygenation index variability may be a surrogate for impaired cerebral metabolic autoregulation in the immediate postoperative period. Further research is

Does the estimation of light attenuation in tissue increase the accuracy of reflectance pulse oximetry at low oxygen saturations in vivo?

PubMed

Kisch-Wedel, H; Bernreuter, P; Kemming, G; Albert, M; Zwissler, B

2009-09-01

A new technique was validated in vivo in reflectance pulse oximetry for measuring low oxygen saturations. Two pairs of light emitter/detector diodes allow for estimation of light attenuation (LA) in tissue, which is assumed to be responsible for the inaccuracy of pulse oximetry at less than 70 % arterial oxygen saturation. For validation, 17 newborn piglets were desaturated stepwise from 21 % to 1.25 % inspiratory oxygen concentration during general anesthesia, and arterial oxygen saturation was measured with the reflectance pulse oximeter adjusted for LA in tissue, with a standard transmission pulse oximeter and a hemoximeter. LA in tissue could be quantified and was different between snout and foreleg (probability level (p) < 0.05). At arterial oxygen saturations above 70 %, the bias between the methods was at 0 %-1 % and the variability 4 %-5 %. From 2 % to 100 % arterial oxygen saturation, the reflectance pulse oximeter estimated oxyhemoglobin saturation more accurately than a conventional transmission pulse oximeter (p < 0.05). At low oxygen saturations below 70 %, the bias and variability of the reflectance pulse oximeter calibration were closer to the hemoximeter measurements than the transmission pulse oximeter (p < 0.05). The variability of the reflectance pulse oximeter was slightly lower than the traditional oximeter by taking into account the LA in tissue (9 % versus 11 % -15 %, ns), and thus, the quality of the individual calibration lines improved (correlation coefficient, p < 0.05).

Localized increase of tissue oxygen tension by magnetic targeted drug delivery

NASA Astrophysics Data System (ADS)

Liong, Celine; Ortiz, Daniel; Ao-ieong, Eilleen; Navati, Mahantesh S.; Friedman, Joel M.; Cabrales, Pedro

2014-07-01

Hypoxia is the major hindrance to successful radiation therapy of tumors. Attempts to increase the oxygen (O2) tension (PO2) of tissue by delivering more O2 have been clinically disappointing, largely due to the way O2 is transported and released by the hemoglobin (Hb) within the red blood cells (RBCs). Systemic manipulation of O2 transport increases vascular resistance due to metabolic autoregulation of blood flow to prevent over oxygenation. This study investigates a new technology to increase O2 delivery to a target tissue by decreasing the Hb-O2 affinity of the blood circulating within the targeted tissue. As the Hb-O2 affinity decreases, the tissue PO2 to satisfy tissue O2 metabolic needs increases without increasing O2 delivery or extraction. Paramagnetic nanoparticles (PMNPs), synthetized using gadolinium oxide, were coated with the cell permeable Hb allosteric effector L35 (3,5-trichlorophenylureido-phenoxy-methylpropionic acid). L35 decreases Hb affinity for O2 and favors the release of O2. The L35-coated PMNPs (L35-PMNPs) were intravenously infused (10 mg kg-1) to hamsters instrumented with the dorsal window chamber model. A magnetic field of 3 mT was applied to localize the effects of the L35-PMNPs to the window chamber. Systemic O2 transport characteristics and microvascular tissue oxygenation were measured after administration of L35-PMNPs with and without magnetic field. The tissue PO2 in untreated control animals was 25.2 mmHg. L35-PMNPs without magnetic field decreased tissue PO2 to 23.4 mmHg, increased blood pressure, and reduced blood flow, largely due to systemic modification of Hb-O2 affinity. L35-PMNPs with magnetic field increased tissue PO2 to 27.9 mmHg, without systemic or microhemodynamic changes. These results indicate that localized modification of Hb-O2 affinity can increase PO2 of target tissue without affecting systemic O2 delivery or triggering O2 autoregulation mechanisms. This technology can be used to treat local hypoxia and to

Image-guided optical measurement of blood oxygen saturation within capillary vessels (Conference Presentation)

NASA Astrophysics Data System (ADS)

Akons, Kfir; Zeidan, Adel; Yeheskely-Hayon, Daniella; Minai, Limor; Yelin, Dvir

2016-03-01

Values of blood oxygenation levels are useful for assessing heart and lung conditions, and are frequently monitored during routine patient care. Independent measurement of the oxygen saturation in capillary blood, which is significantly different from that of arterial blood, is important for diagnosing tissue hypoxia and for increasing the accuracy of existing techniques that measure arterial oxygen saturation. Here, we developed a simple, non-invasive technique for measuring the reflected spectra from individual capillary vessels within a human lip, allowing local measurement of the blood oxygen saturation. The optical setup includes a spatially incoherent broadband light that was focused onto a specific vessel below the lip surface. Backscattered light was imaged by a camera for identifying a target vessel and pointing the illumination beam to its cross section. Scattered light from the vessel was then collected by a single-mode fiber and analyzed by a fast spectrometer. Spectra acquired from small capillary vessels within a volunteer lip showed the characteristic oxyhemoglobin absorption bands in real time and with a high signal-to-noise ratio. Measuring capillary oxygen saturation using this technique would potentially be more accurate compared to existing pulse oximetry techniques due to its insensitivity to the patient's skin color, pulse rate, motion, and medical condition. It could be used as a standalone endoscopic technique for measuring tissue hypoxia or in conjunction with conventional pulse oximetry for a more accurate measurement of oxygen transport in the body.

2,3-diphosphoglycerate and oxygen supply of tissues in cardiosurgical diabetics.

PubMed

Beder, I; Mataseje, A; Kittova, M; Carsky, J; Fischer, V

2005-01-01

The oxygen supply of tissues was studied under haemodilution in cardiosurgical diabetic and non-diabetic patients. There were 30 cardiosurgery patients examined, 9 were patients with diabetes mellitus.and 21 were non-diabetic patients. Venous blood samples were examined preoperatively, intraoperatively and for 10 days after operation. Haemodilution caused a decrease in haematocrit values in both groups, as well as in the erythrocyte count and haemoglobin concentration. Postoperatively, an increase was recorded in haematological values in both groups, the values had not reached the baseline even by 10th day. Increased values of blood oxygen saturation and partial oxygen pressure during the operation returned to baseline in both groups in the postoperative days. Values of p50 did not change in both groups for the period of observation. The obtained data suggest that sufficient oxygen supply to tissues was ensured under haemodilution in cardiosurgery patients in both groups. These results confirm multifactorial dependence of blood oxygen transport to tissues (Tab. 1, Fig. 3, Ref. 13).

Mixtures of tense and relaxed state polymerized human hemoglobin regulate oxygen affinity and tissue construct oxygenation

PubMed Central

Belcher, Donald Andrew; Banerjee, Uddyalok; Baehr, Christopher Michael; Richardson, Kristopher Emil; Cabrales, Pedro; Berthiaume, François

2017-01-01

Pure tense (T) and relaxed (R) quaternary state polymerized human hemoglobins (PolyhHbs) were synthesized and their biophysical properties characterized, along with mixtures of T- and R-state PolyhHbs. It was observed that the oxygen affinity of PolyhHb mixtures varied linearly with T-state mole fraction. Computational analysis of PolyhHb facilitated oxygenation of a single fiber in a hepatic hollow fiber (HF) bioreactor was performed to evaluate the oxygenation potential of T- and R-state PolyhHb mixtures. PolyhHb mixtures with T-state mole fractions greater than 50% resulted in hypoxic and hyperoxic zones occupying less than 5% of the total extra capillary space (ECS). Under these conditions, the ratio of the pericentral volume to the perivenous volume in the ECS doubled as the T-state mole fraction increased from 50 to 100%. These results show the effect of varying the T/R-state PolyhHb mole fraction on oxygenation of tissue-engineered constructs and their potential to oxygenate tissues. PMID:29020036

Perioperative fluid management: comparison of high, medium and low fluid volume on tissue oxygen pressure in the small bowel and colon.

PubMed

Hiltebrand, L B; Pestel, G; Hager, H; Ratnaraj, J; Sigurdsson, G H; Kurz, A

2007-11-01

Insufficient blood flow and oxygenation in the intestinal tract is associated with increased incidence of postoperative complications after bowel surgery. High fluid volume administration may prevent occult regional hypoperfusion and intestinal tissue hypoxia. We tested the hypothesis that high intraoperative fluid volume administration increases intestinal wall tissue oxygen pressure during laparotomy. In all, 27 pigs were anaesthetized, ventilated and randomly assigned to one of the three treatment groups (n = 9 in each) receiving low (3 mL kg-1 h-1), medium (7 mL kg-1 h-1) or high (20 mL kg-1 h-1) fluid volume treatment with lactated Ringer's solution. All animals received 30% and 100% inspired oxygen in random order. Cardiac index was measured with thermodilution and tissue oxygen pressure with a micro-oximetry system in the jejunum and colon wall and subcutaneous tissue. Groups receiving low and medium fluid volume treatment had similar systemic haemodynamics. The high fluid volume group had significantly higher mean arterial pressure, cardiac index and subcutaneous tissue oxygenation. Tissue oxygen pressures in the jejunum and colon were comparable in all three groups. The three different fluid volume regimens tested did not affect tissue oxygen pressure in the jejunum and colon, suggesting efficient autoregulation of intestinal blood flow in healthy subjects undergoing uncomplicated abdominal surgery.

Vascular responsiveness measured by tissue oxygen saturation reperfusion slope is sensitive to different occlusion durations and training status.

PubMed

McLay, Kaitlin M; Gilbertson, James E; Pogliaghi, Silvia; Paterson, Donald H; Murias, Juan M

2016-10-01

What is the central question of this study? Is the near-infrared spectroscopy-derived measure of tissue oxygen saturation (StO2) reperfusion slope sensitive to a range of ischaemic conditions, and do differences exist between trained and untrained individuals? What is the main finding and its importance? The StO2 reperfusion rate is sensitive to different occlusion durations, and changes in the reperfusion slope in response to a variety of ischaemic challenges can be used to detect differences between two groups. These data indicate that near-infrared spectroscopy-derived measures of StO2, specifically the reperfusion slope following a vascular occlusion, can be used as a sensitive measure of vascular responsiveness. The reperfusion rate of near-infrared spectroscopy-derived measures of tissue oxygen saturation (StO2) represents vascular responsiveness. This study examined whether the reperfusion slope of StO2 is sensitive to different ischaemic conditions (i.e. a dose-response relationship) and whether differences exist between two groups of different fitness levels. Nine healthy trained (T; age 25 ± 3 years; maximal oxygen uptake 63.4 ± 6.7 ml kg -1  min -1 ) and nine healthy untrained men (UT; age 21 ± 1 years; maximal oxygen uptake 46.6 ± 2.5 ml kg -1  min -1 ) performed a series of vascular occlusion tests of different durations (30 s, 1, 2, 3 and 5 min), each separated by 30 min. The StO2 was measured over the tibialis anterior using near-infrared spectroscopy, with the StO2 reperfusion slope calculated as the upslope during 10 s following cuff release. The reperfusion slope was steeper in T compared with UT at all occlusion durations (P < 0.05). For the T group, the reperfusion slopes for 30 s and 1 min occlusions were less than for all longer durations (P < 0.05). The reperfusion slope following 2 min occlusion was similar to that for 3 min (P > 0.05), but both were less steep than for 5 min of occlusion. In UT, the

Simulating tissue oxygenation by encapsulating hemoglobin in polymer microcapsules (Conference Presentation)

NASA Astrophysics Data System (ADS)

Liu, Guangli; Wu, Qiang; Shen, Shuwei; Zhao, Gang; Dong, Erbao; Xu, Ronald X.

2017-03-01

We describe a combination of liquid-jet microencapsulation and molding techniques to fabricate tissue-simulating phantoms that mimick functional characteristics of tissue oxygen saturation (StO2). Chicken hemoglobin (Hb) was encapsulated inside a photocurable resin by a coaxial flow focusing process. The microdroplets were cured by ultraviolet (UV) illumination to form Hb loaded polymersome microdroplets. The microdroplets were further freeze-dried to form semipermeable solid microcapules with an outer transparent polymeric shell and an inner core of Hb. The diameter of the microcapsules ranged from 50 to100 μm. The absorption spectrum of the microcapsules was measured by a UV/VIS spectrophotometer over a wavelength range from 400 nm to 1100 nm. To fabricate the tissue-simulating phantom, the Hb loaded microcapsules were dispersed in transparent polydimethylsiloxane (PDMS). The optical properties of the phantom were determined by an vertical double integrating sphere with a reconstruction algorithm. The experimental results showed that the tissue-simulating phantom exhibited the spectral characteristics closely resembling that of oxy-hemoglobin. The phantom had a long-term optical stability when stored in 4 ℃, indicating that microencapsulation effectively protected Hb and improved its shelf time. With the Hb loaded microcapsules, we will produce skin-simulating phantoms for quantitative validation of multispectral imaging techniques. To the best of the authors' knowledge, no solid phantom is able to mimick living tissue oxygenation with good agreement. Therefore, our work provided an engineering platform for validating and calibrating spectral optical devices in biomedical applications.

Oxygen demand of perfused heart preparations: how electromechanical function and inadequate oxygenation affect physiology and optical measurements.

PubMed

Kuzmiak-Glancy, Sarah; Jaimes, Rafael; Wengrowski, Anastasia M; Kay, Matthew W

2015-06-01

What is the topic of this review? This review discusses how the function and electrophysiology of isolated perfused hearts are affected by oxygenation and energy utilization. The impact of oxygenation on fluorescence measurements in perfused hearts is also discussed. What advances does it highlight? Recent studies have illuminated the inherent differences in electromechanical function, energy utilization rate and oxygen requirements between the primary types of excised heart preparations. A summary and analysis of how these variables affect experimental results are necessary to elevate the physiological relevance of these approaches in order to advance the field of whole-heart research. The ex vivo perfused heart recreates important aspects of in vivo conditions to provide insight into whole-organ function. In this review we discuss multiple types of ex vivo heart preparations, explain how closely each mimic in vivo function, and discuss how changes in electromechanical function and inadequate oxygenation of ex vivo perfused hearts may affect measurements of physiology. Hearts that perform physiological work have high oxygen demand and are likely to experience hypoxia when perfused with a crystalloid perfusate. Adequate myocardial oxygenation is critically important for obtaining physiologically relevant measurements, so when designing experiments the type of ex vivo preparation and the capacity of perfusate to deliver oxygen must be carefully considered. When workload is low, such as during interventions that inhibit contraction, oxygen demand is also low, which could dramatically alter a physiological response to experimental variables. Changes in oxygenation also alter the optical properties of cardiac tissue, an effect that may influence optical signals measured from both endogenous and exogenous fluorophores. Careful consideration of oxygen supply, working condition, and wavelengths used to acquire optical signals is critical for obtaining physiologically

Noninvasive assessment of tissue-engineered graft viability by oxygen-17 magnetic resonance spectroscopy.

PubMed

Einstein, Samuel A; Weegman, Bradley P; Kitzmann, Jennifer P; Papas, Klearchos K; Garwood, Michael

2017-05-01

Transplantation of macroencapsulated tissue-engineered grafts (TEGs) is being investigated as a treatment for type 1 diabetes, but there is a critical need to measure TEG viability both in vitro and in vivo. Oxygen deficiency is the most critical issue preventing widespread implementation of TEG transplantation and delivery of supplemental oxygen (DSO) has been shown to enhance TEG survival and function in vivo. In this study, we demonstrate the first use of oxygen-17 magnetic resonance spectroscopy ( 17 O-MRS) to measure the oxygen consumption rate (OCR) of TEGs and show that in addition to providing therapeutic benefits to TEGs, DSO with 17 O 2 can also enable measurements of TEG viability. Macroencapsulated TEGs containing βTC3 murine insulinoma cells were prepared with three fractional viabilities and provided with 17 O 2 . Cellular metabolism of 17 O 2 into nascent mitochondrial water (H 2 17 O) was monitored by 17 O-MRS and, from the measured data, OCR was calculated. For comparison, OCR was simultaneously measured on a separate, but equivalent sample of cells with a well-established stirred microchamber technique. OCR measured by 17 O-MRS agreed well with measurements made in the stirred microchamber device. These studies confirm that 17 O-MRS can quantify TEG viability noninvasively. Biotechnol. Bioeng. 2017;114: 1118-1121. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Reduced Adipose Tissue Oxygenation in Human Obesity

PubMed Central

Pasarica, Magdalena; Sereda, Olga R.; Redman, Leanne M.; Albarado, Diana C.; Hymel, David T.; Roan, Laura E.; Rood, Jennifer C.; Burk, David H.; Smith, Steven R.

2009-01-01

OBJECTIVE— Based on rodent studies, we examined the hypothesis that increased adipose tissue (AT) mass in obesity without an adequate support of vascularization might lead to hypoxia, macrophage infiltration, and inflammation. RESEARCH DESIGN AND METHODS— Oxygen partial pressure (AT pO2) and AT temperature in abdominal AT (9 lean and 12 overweight/obese men and women) was measured by direct insertion of a polarographic Clark electrode. Body composition was measured by dual-energy X-ray absorptiometry, and insulin sensitivity was measured by hyperinsulinemic-euglycemic clamp. Abdominal subcutaneous tissue was used for staining, quantitative RT-PCR, and chemokine secretion assay. RESULTS— AT pO2 was lower in overweight/obese subjects than lean subjects (47 ± 10.6 vs. 55 ± 9.1 mmHg); however, this level of pO2 did not activate the classic hypoxia targets (pyruvate dehydrogenase kinase and vascular endothelial growth factor [VEGF]). AT pO2 was negatively correlated with percent body fat (R = −0.50, P < 0.05). Compared with lean subjects, overweight/obese subjects had 44% lower capillary density and 58% lower VEGF, suggesting AT rarefaction (capillary drop out). This might be due to lower peroxisome proliferator–activated receptor γ1 and higher collagen VI mRNA expression, which correlated with AT pO2 (P < 0.05). Of clinical importance, AT pO2 negatively correlated with CD68 mRNA and macrophage inflammatory protein 1α secretion (R = −0.58, R = −0.79, P < 0.05), suggesting that lower AT pO2 could drive AT inflammation in obesity. CONCLUSIONS— Adipose tissue rarefaction might lie upstream of both low AT pO2 and inflammation in obesity. These results suggest novel approaches to treat the dysfunctional AT found in obesity. PMID:19074987

Assessment of Renal Hemodynamics and Oxygenation by Simultaneous Magnetic Resonance Imaging (MRI) and Quantitative Invasive Physiological Measurements.

PubMed

Cantow, Kathleen; Arakelyan, Karen; Seeliger, Erdmann; Niendorf, Thoralf; Pohlmann, Andreas

2016-01-01

In vivo assessment of renal perfusion and oxygenation under (patho)physiological conditions by means of noninvasive diagnostic imaging is conceptually appealing. Blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) and quantitative parametric mapping of the magnetic resonance (MR) relaxation times T 2* and T 2 are thought to provide surrogates of renal tissue oxygenation. The validity and efficacy of this technique for quantitative characterization of local tissue oxygenation and its changes under different functional conditions have not been systematically examined yet and remain to be established. For this purpose, the development of an integrative multimodality approaches is essential. Here we describe an integrated hybrid approach (MR-PHYSIOL) that combines established quantitative physiological measurements with T 2* (T 2) mapping and MR-based kidney size measurements. Standardized reversible (patho)physiologically relevant interventions, such as brief periods of aortic occlusion, hypoxia, and hyperoxia, are used for detailing the relation between the MR-PHYSIOL parameters, in particular between renal T 2* and tissue oxygenation.

Near-infrared spectroscopy for monitoring of tissue oxygenation of exercising skeletal muscle in a chronic compartment syndrome model

NASA Technical Reports Server (NTRS)

Breit, G. A.; Gross, J. H.; Watenpaugh, D. E.; Chance, B.; Hargens, A. R.

1997-01-01

Variations in the levels of muscle hemoglobin and of myoglobin oxygen saturation can be detected non-invasively with near-infrared spectroscopy. This technique could be applied to the diagnosis of chronic compartment syndrome, in which invasive testing has shown increased intramuscular pressure associated with ischemia and pain during exercise. We simulated chronic compartment syndrome in ten healthy subjects (seven men and three women) by applying external compression, through a wide inflatable cuff, to increase the intramuscular pressure in the anterior compartment of the leg. The tissue oxygenation of the tibialis anterior muscle was measured with near-infrared spectroscopy during gradual inflation of the cuff to a pressure of forty millimeters of mercury (5.33 kilopascals) during fourteen minutes of cyclic isokinetic dorsiflexion and plantar flexion of the ankle. The subjects exercised with and without external compression. The data on tissue oxygenation for each subject then were normalized to a scale of 100 per cent (the baseline value, or the value at rest) to 0 per cent (the physiological minimum, or the level of oxygenation achieved by exercise to exhaustion during arterial occlusion of the lower extremity). With external compression, tissue oxygenation declined at a rate of 1.4 +/- 0.3 per cent per minute (mean and standard error) during exercise. After an initial decrease at the onset, tissue oxygenation did not decline during exercise without compression. The recovery of tissue oxygenation after exercise was twice as slow with compression (2.5 +/- 0.6 minutes) than it was without the use of compression (1.3 +/- 0.2 minutes).

Red blood cell transfusions and tissue oxygenation in anemic hematology outpatients.

PubMed

Yuruk, Koray; Bartels, Sebastiaan A; Milstein, Dan M J; Bezemer, Rick; Biemond, Bart J; Ince, Can

2012-03-01

There is little clinical evidence that red blood cell (RBC) transfusions improve oxygen availability at the microcirculatory level. We tested the hypotheses that anemia in chronically anemic patients with relatively healthy microcirculation would be associated with low tissue hemoglobin (Hb) and tissue oxygenation levels and that these conditions would be improved after RBC transfusions. Near-infrared spectroscopy (NIRS) was used to determine tissue oxygen saturation (StO(2)) and tissue Hb index (THI; an index of the amount of Hb in the NIRS measurement volume) in the thenar eminence and sublingual tissue before and 30 minutes after RBC transfusions in 20 chronically anemic hematology outpatients. Data are presented as median (25%-75%). The patients received three (two to three) bags of RBCs in saline-adenine-glucose-mannitol with an age of 21 (7-21) days, which was infused intravenously at the rate of 0.7 bag/hr. RBC transfusions significantly increased hematocrit level from 26% (24%-28%) to 32% (30%-34%; p < 0.0001), Hb level from 8.2 (7.6-8.9) g/dL to 11.0 (9.9-11.8) g/dL (p < 0.0001), whole blood viscosity from 3.4 (3.1-3.5) mPa/sec to 4.2 (4.0-4.5) mPa/sec (p < 0.0001), thenar StO(2) from 81% (80%-84%) to 86% (81%-89%; p = 0.002), thenar THI from 11.2 (9.3-13.3) AU to 13.7 (9.7-15.3) AU (p = 0.024), sublingual StO(2) from 86% (81%-89%) to 91% (86%-92%; p < 0.0001), and sublingual THI from 15.2 (13.0-17.4) AU to 17.2 (13.5-19.7) AU (p = 0.040). Although anemia in chronically anemic hematology outpatients was not associated with low StO(2) and THI levels, RBC transfusions were successful in improving these variables. © 2011 American Association of Blood Banks.

Oxygen Gradients in the Microcirculation

PubMed Central

Pittman, Roland N.

2010-01-01

Early in the last century August Krogh embarked on a series of seminal studies to understand the connection between tissue metabolism and mechanisms by which the cardiovascular system supplied oxygen to meet those needs. Krogh recognized that oxygen was supplied from blood to the tissues by passive diffusion and that the most likely site for oxygen exchange was the capillary network. Studies of tissue oxygen consumption and diffusion coefficient, coupled with anatomical studies of capillarity in various tissues, led him to formulate a model of oxygen diffusion from a single capillary. Fifty years after the publication of this work, new methods were developed which allowed the direct measurement of oxygen in and around microvessels. These direct measurements have confirmed the predictions by Krogh and have led to extensions of his ideas resulting in our current understanding of oxygenation within the microcirculation. Developments during the last 40 years are reviewed, including studies of oxygen gradients in arterioles, capillaries, venules, microvessel wall and surrounding tissue. These measurements were made possible by the development and use of new methods to investigate oxygen in the microcirculation, so mention is made of oxygen microelectrodes, microspectrophotometry of haemoglobin and phosphorescence quenching microscopy. Our understanding of oxygen transport from the perspective of the microcirculation has gone from a consideration of oxygen gradients in capillaries and tissue to the realization that oxygen has the ability to diffuse from any microvessel to another location under the conditions that there exists a large enough PO2 gradient and that the permeability for oxygen along the intervening pathway is sufficient. PMID:21281453

Reaction of oxygen with the respiratory chain in cells and tissues.

PubMed

Chance, B

1965-09-01

This paper considers the way in which the oxygen reaction described by Dr. Nicholls and the ADP control reactions described by Dr. Racker could cooperate to establish a purposeful metabolic control phenomenon in vivo. This has required an examination of the kinetic properties of the respiratory chain with particular reference to methods for determinations of oxygen affinity (K(m)). The constant parameter for tissue respiration is k(1), the velocity constant for the reaction of oxygen with cytochrome oxidase. Not only is this quantity a constant for a particular tissue or mitochondria; it appears to vary little over a wide range of biological material, and for practical purposes a value of 5 x 10(7) at 25 degrees close to our original value (20) is found to apply with adequate accuracy for calculation of K(m) for mammalia. The quantity which will depend upon the tissue and its metabolic state is the value of K(m) itself, and K(m) may be as large as 0.5 microM and may fall to 0.05 microM or less in resting, controlled, or inhibited states. The control characteristic for ADP may depend upon the electron flux due to the cytochrome chain (40); less ADP is required to activate the slower electron transport at lower temperatures than at higher temperatures. The affinity constants for ADP control appear to be less dependent upon substrate supplied to the system. The balance of ADP and oxygen control in vivo is amply demonstrated experimentally and is dependent on the oxygen concentration as follows. In the presence of excess oxygen, control may be due to the ADP or phosphate (or substrate), and the kinetics of oxygen utilization will be independent of the oxygen concentration. As the oxygen concentration is diminished, hemoglobin becomes disoxygenated, deep gradients of oxygen concentration develop in the tissue, and eventually cytochrome oxidase becomes partially and then completely reduced. DPN at this point will become reduced and the electron flow diminished. The rate

Hemodynamic measurements in deep brain tissues of humans by near-infrared time-resolved spectroscopy

NASA Astrophysics Data System (ADS)

Suzuki, Hiroaki; Oda, Motoki; Yamaki, Etsuko; Suzuki, Toshihiko; Yamashita, Daisuke; Yoshimoto, Kenji; Homma, Shu; Yamashita, Yutaka

2014-03-01

Using near-infrared time-resolved spectroscopy (TRS), we measured the human head in transmittance mode to obtain the optical properties, tissue oxygenation, and hemodynamics of deep brain tissues in 50 healthy adult volunteers. The right ear canal was irradiated with 3-wavelengths of pulsed light (760, 795, and 835nm), and the photons passing through the human head were collected at the left ear canal. Optical signals with sufficient intensity could be obtained from 46 of the 50 volunteers. By analyzing the temporal profiles based on the photon diffusion theory, we successfully obtained absorption coefficients for each wavelength. The levels of oxygenated hemoglobin (HbO2), deoxygenated hemoglobin (Hb), total hemoglobin (tHb), and tissue oxygen saturation (SO2) were then determined by referring to the hemoglobin spectroscopic data. Compared with the SO2 values for the forehead measurements in reflectance mode, the SO2 values of the transmittance measurements of the human head were approximately 10% lower, and tHb values of the transmittance measurements were always lower than those of the forehead reflectance measurements. Moreover, the level of hemoglobin and the SO2 were strongly correlated between the human head measurements in transmittance mode and the forehead measurements in the reflectance mode, respectively. These results demonstrated a potential application of this TRS system in examining deep brain tissues of humans.

Implementing oxygen control in chip-based cell and tissue culture systems.

PubMed

Oomen, Pieter E; Skolimowski, Maciej D; Verpoorte, Elisabeth

2016-09-21

Oxygen is essential in the energy metabolism of cells, as well as being an important regulatory parameter influencing cell differentiation and function. Interest in precise oxygen control for in vitro cultures of tissues and cells continues to grow, especially with the emergence of the organ-on-a-chip and the desire to emulate in vivo conditions. This was recently discussed in this journal in a Critical Review by Brennan et al. (Lab Chip (2014). DOI: ). Microfluidics can be used to introduce flow to facilitate nutrient supply to and waste removal from in vitro culture systems. Well-defined oxygen gradients can also be established. However, cells can quickly alter the oxygen balance in their vicinity. In this Tutorial Review, we expand on the Brennan paper to focus on the implementation of oxygen analysis in these systems to achieve continuous monitoring. Both electrochemical and optical approaches for the integration of oxygen monitoring in microfluidic tissue and cell culture systems will be discussed. Differences in oxygen requirements from one organ to the next are a challenging problem, as oxygen delivery is limited by its uptake into medium. Hence, we discuss the factors determining oxygen concentrations in solutions and consider the possible use of artificial oxygen carriers to increase dissolved oxygen concentrations. The selection of device material for applications requiring precise oxygen control is discussed in detail, focusing on oxygen permeability. Lastly, a variety of devices is presented, showing the diversity of approaches that can be employed to control and monitor oxygen concentrations in in vitro experiments.

Oxygen gradients in the microcirculation.

PubMed

Pittman, R N

2011-07-01

Early in the last century August Krogh embarked on a series of seminal studies to understand the connection between tissue metabolism and mechanisms by which the cardiovascular system supplied oxygen to meet those needs. Krogh recognized that oxygen was supplied from blood to the tissues by passive diffusion and that the most likely site for oxygen exchange was the capillary network. Studies of tissue oxygen consumption and diffusion coefficient, coupled with anatomical studies of capillarity in various tissues, led him to formulate a model of oxygen diffusion from a single capillary. Fifty years after the publication of this work, new methods were developed which allowed the direct measurement of oxygen in and around microvessels. These direct measurements have confirmed the predictions by Krogh and have led to extensions of his ideas resulting in our current understanding of oxygenation within the microcirculation. Developments during the last 40 years are reviewed, including studies of oxygen gradients in arterioles, capillaries, venules, microvessel wall and surrounding tissue. These measurements were made possible by the development and use of new methods to investigate oxygen in the microcirculation, so mention is made of oxygen microelectrodes, microspectrophotometry of haemoglobin and phosphorescence quenching microscopy. Our understanding of oxygen transport from the perspective of the microcirculation has gone from a consideration of oxygen gradients in capillaries and tissue to the realization that oxygen has the ability to diffuse from any microvessel to another location under the conditions that there exists a large enough PO(2) gradient and that the permeability for oxygen along the intervening pathway is sufficient. © 2011 The Author. Acta Physiologica © 2011 Scandinavian Physiological Society.

Engineering large cartilage tissues using dynamic bioreactor culture at defined oxygen conditions.

PubMed

Daly, Andrew C; Sathy, Binulal N; Kelly, Daniel J

2018-01-01

Mesenchymal stem cells maintained in appropriate culture conditions are capable of producing robust cartilage tissue. However, gradients in nutrient availability that arise during three-dimensional culture can result in the development of spatially inhomogeneous cartilage tissues with core regions devoid of matrix. Previous attempts at developing dynamic culture systems to overcome these limitations have reported suppression of mesenchymal stem cell chondrogenesis compared to static conditions. We hypothesize that by modulating oxygen availability during bioreactor culture, it is possible to engineer cartilage tissues of scale. The objective of this study was to determine whether dynamic bioreactor culture, at defined oxygen conditions, could facilitate the development of large, spatially homogeneous cartilage tissues using mesenchymal stem cell laden hydrogels. A dynamic culture regime was directly compared to static conditions for its capacity to support chondrogenesis of mesenchymal stem cells in both small and large alginate hydrogels. The influence of external oxygen tension on the response to the dynamic culture conditions was explored by performing the experiment at 20% O 2 and 3% O 2 . At 20% O 2 , dynamic culture significantly suppressed chondrogenesis in engineered tissues of all sizes. In contrast, at 3% O 2 dynamic culture significantly enhanced the distribution and amount of cartilage matrix components (sulphated glycosaminoglycan and collagen II) in larger constructs compared to static conditions. Taken together, these results demonstrate that dynamic culture regimes that provide adequate nutrient availability and a low oxygen environment can be employed to engineer large homogeneous cartilage tissues. Such culture systems could facilitate the scaling up of cartilage tissue engineering strategies towards clinically relevant dimensions.

Correlation of oxygenation and perfusion sensitive MRI with invasive micro probe measurements in healthy mice brain.

PubMed

Sedlacik, Jan; Reitz, Matthias; Bolar, Divya S; Adalsteinsson, Elfar; Schmidt, Nils O; Fiehler, Jens

2015-03-01

The non-invasive assessment of (patho-)physiological parameters such as, perfusion and oxygenation, is of great importance for the characterization of pathologies e.g., tumors, which may be helpful to better predict treatment response and potential outcome. To better understand the influence of physiological parameters on the investigated oxygenation and perfusion sensitive MRI methods, MRI measurements were correlated with subsequent invasive micro probe measurements during free breathing conditions of air, air+10% CO2 and 100% O2 in healthy mice brain. MRI parameters were the irreversible (R2), reversible (R2') and effective (R2*) transverse relaxation rates, venous blood oxygenation level assessed by quantitative blood oxygenation level dependent (qBOLD) method and cerebral blood flow (CBF) assessed by arterial spin labeling (ASL) using a 7 T small animal MRI scanner. One to two days after MRI, tissue perfusion and pO2 were measured by Laser-Doppler flowmetry and fluorescence quenching micro probes, respectively. The tissue pO2 values were converted to blood oxygen saturation by using the Hill equation. The animals were anesthetized by intra peritoneal injection of ketamine-xylazine-acepromazine (10-2-0.3 mg/ml · kg). Results for normal/hypercapnia/hyperoxia conditions were: R2[s(∧)-1] = 20.7/20.4/20.1, R2*[s(∧)-1] = 31.6/29.6/25.9, R2'[s-(∧)1] = 10.9/9.2/5.7, qBOLD venous blood oxygenation level = 0.43/0.51/0.56, CBF[ml · min(∧)-1 · 100 g(∧)-1] = 70.6/105.5/81.8, Laser-Doppler flowmetry[a.u.] = 89.2/120.2/90.6 and pO2[mmHg] = 6.3/32.3/46.7. All parameters were statistically significantly different with P < 0.001 between all breathing conditions. All MRI and the corresponding micro probe measurements were also statistically significantly (P ≤ 0.03) correlated with each other. However, converting the tissue pO2 to blood oxygen saturation = 0.02/0.34/0.63, showed only very limited agreement with the qBOLD venous blood oxygenation level. We found

Noninvasive oxygen monitoring techniques.

PubMed

Wahr, J A; Tremper, K K

1995-01-01

As this article demonstrates, tremendous progress has been made in the techniques of oxygen measurement and monitoring over the past 50 years. From the early developments during and after World War II, to the most recent applications of solid state and microprocessor technology today, every patient in a critical care situation will have several continuous measurements of oxygenation applied simultaneously. Information therefore is available readily to alert personnel of acute problems and to guide appropriate therapy. The majority of effort to date has been placed on measuring oxygenation of arterial or venous blood. The next generation of devices will attempt to provide information about living tissue. Unlike the devices monitoring arterial or venous oxygen content, no "gold standards" exist for tissue oxygenation, so calibration will be difficult, as will interpretation of the data provided. The application of these devices ultimately may lead to a much better understanding of how disease (and the treatment of disease) alters the utilization of oxygen by the tissues.

Metabolic Prosthesis for Oxygenation of Ischemic Tissue

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

Greenbaum, Elias

2009-01-01

This communication discloses new ideas and preliminary results on the development of a "metabolic prosthesis" for local oxygenation of ischemic tissue under physiological neutral conditions. We report for the first time the selective electrolysis of physiological saline by repetitively pulsed charge-limited electrolysis for the production of oxygen and suppression of free chlorine. For example, using 800 A amplitude current pulses and <200 sec pulse durations, we demonstrated prompt oxygen production and delayed chlorine production at the surface of a shiny 0.85 mm diameter spherical platinum electrode. The data, interpreted in terms of the ionic structure of the electric double layer,more » suggest a strategy for in situ production of metabolic oxygen via a new class of "smart" prosthetic implants for dealing with ischemic disease such as diabetic retinopathy. We also present data indicating that drift of the local pH of the oxygenated environment can be held constant using a feedback-controlled three electrode electrolysis system that chooses anode and cathode pair based on pH data provided by local microsensors. The work is discussed in the context of diabetic retinopathy since surgical techniques for multielectrode prosthetic implants aimed at retinal degenerative diseases have been developed.« less

'Multi-associations': predisposed to misinterpretation of peripheral tissue oxygenation and circulation in neonates.

PubMed

Pichler, Gerhard; Pocivalnik, Mirjam; Riedl, Regina; Pichler-Stachl, Elisabeth; Morris, Nicholas; Zotter, Heinz; Müller, Wilhelm; Urlesberger, Berndt

2011-08-01

Interpretation of peripheral circulation in ill neonates is crucial but difficult. The aim was to analyse parameters potentially influencing peripheral oxygenation and circulation. In a prospective observational cohort study in 116 cardio-circulatory stable neonates, peripheral muscle near-infrared spectroscopy (NIRS) with venous occlusion was performed. Tissue oxygenation index (TOI), mixed venous oxygenation (SvO(2)), fractional oxygen extraction (FOE), fractional tissue oxygen extraction (FTOE), haemoglobin flow (Hbflow), oxygen delivery (DO(2)), oxygen consumption (VO(2)), and vascular resistance (VR) were assessed. Correlation coefficients between NIRS parameters and demographic parameters (gestational age, birth weight, age, actual weight, diameter of calf, subcutaneous adipose tissue), monitoring parameters (heart rate, arterial oxygen saturation (SaO(2)), mean blood pressure (MAP), core/peripheral temperature, central/peripheral capillary refill time) and laboratory parameters (haemoglobin concentration (Hb-blood), pCO(2)) were calculated. All demographic parameters except for Hbflow and DO(2) correlated with NIRS parameters. Heart rate correlated with TOI, SvO(2), VO(2) and VR. SaO(2) correlated with FOE/FTOE. MAP correlated with Hbflow, DO(2), VO(2) and VR. Core temperature correlated with FTOE. Peripheral temperature correlated with all NIRS parameters except VO(2). Hb-blood correlated with FOE and VR. pCO(2) levels correlated with TOI and SvO(2). The presence of multiple interdependent factors associated with peripheral oxygenation and circulation highlights the difficulty in interpreting NIRS data. Nevertheless, these findings have to be taken into account when analysing peripheral oxygenation and circulation data.

Cerebral oxygenation in traumatic brain injury; Can a non-invasive frequency domain near-infrared spectroscopy device detect changes in brain tissue oxygen tension as well as the established invasive monitor?

PubMed

Davies, David James; Clancy, Michael; Dehghani, Hamid; Lucas, Samuel John Edwin; Forcione, Mario; Yakoub, Kamal Makram; Belli, Antonio

2018-06-07

The cost and highly invasive nature of brain monitoring modality in traumatic brain injury patients currently restrict its utility to specialist neurological intensive care settings. We aim to test the abilities of a frequency domain near-infrared spectroscopy (FD-NIRS) device in predicting changes in invasively measured brain tissue oxygen tension. Individuals admitted to a United Kingdom specialist major trauma centre were contemporaneously monitored with an FD-NIRS device and invasively measured brain tissue oxygen tension probe. Area under the curve receiver operating characteristic (AUROC) statistical analysis was utilised to assess the predictive power of FD-NIRS in detecting both moderate and severe hypoxia (20 and 10 mmHg, respectively), as measured invasively. 16 individuals were prospectively recruited to the investigation. Severe hypoxic episodes were detected in 9 of these individuals, with the NIRS demonstrating a broad range of predictive abilities (AUROC 0.68-0.88) from relatively poor to good. Moderate hypoxic episodes were detected in seven individuals with similar predictive performance (AUROC 0.576 - 0.905). A variable performance in the predictive powers of this FD-NIRS device to detect changes in brain tissue oxygen was demonstrated. Consequently, this enhanced NIRS technology has not demonstrated sufficient ability to replace the established invasive measurement.

Method of measuring blood oxygenation based on spectroscopy of diffusely scattered light

NASA Astrophysics Data System (ADS)

Kleshnin, M. S.; Orlova, A. G.; Kirillin, M. Yu.; Golubyatnikov, G. Yu.; Turchin, I. V.

2017-05-01

A new approach to the measurement of blood oxygenation is developed and implemented, based on an original two-step algorithm reconstructing the relative concentration of biological chromophores (haemoglobin, water, lipids) from the measured spectra of diffusely scattered light at different distances from the radiation source. The numerical experiments and approbation of the proposed approach using a biological phantom have shown the high accuracy of the reconstruction of optical properties of the object in question, as well as the possibility of correct calculation of the haemoglobin oxygenation in the presence of additive noises without calibration of the measuring device. The results of the experimental studies in animals agree with the previously published results obtained by other research groups and demonstrate the possibility of applying the developed method to the monitoring of blood oxygenation in tumour tissues.

Intraoperative monitoring of brain tissue oxygenation during arteriovenous malformation resection.

PubMed

Arikan, Fuat; Vilalta, Jordi; Noguer, Montserrat; Olive, Montserrat; Vidal-Jorge, Marian; Sahuquillo, Juan

2014-10-01

In normal perfusion pressure breakthrough (NPPB) it is assumed that following arteriovenous malformation (AVM) resection, vasoparalysis persists in the margins of the lesion and that a sudden increase in cerebral blood flow (CBF) after AVM exclusion leads to brain swelling and postsurgical complications. However, the pathophysiology NPPB remains controversial.The aim of our study was to investigate the oxygenation status in tissue surrounding AVMs and in the distant brain using intraoperative monitoring of cerebral partial pressure of oxygen (PtiO(2)) to achieve a better understanding of NPPB pathophysiology. Patients with supratentorial AVMs were monitored intraoperatively using 2 polarographic Clark-type electrodes. To establish reference values, we also studied PtiO(2) in a group of patients who underwent surgery to treat incidental aneurysms. Twenty-two patients with supratentorial AVMs and 16 patients with incidentally found aneurysms were included. Hypoxic pattern was defined as PtiO(2)≤15 mm Hg and/or PtiO(2)/PaO(2) ratio ≤0.10. Tissue hypoxia was detected in 63.6% of the catheters placed in the perinidal area and in 43.8% of catheters placed in a distant area. AVM excision significantly improved oxygenation both around the AVM and in the distant area. The PtiO(2)/PaO(2) ratio is a better indicator than absolute PtiO(2) in detecting tissue hypoxia in mechanically ventilated patients. Intraoperative monitoring showed tissue hypoxia in the margins of AVMs and in the distant ipsilateral brain as the most common finding. Surgical removal of AVMs induces a significant improvement in the oxygenation status in both areas.

Tissue Oxygenation and Negative-Pressure Wound Therapy When Applied to the Feet of Persons With Diabetes Mellitus: An Observational Study.

PubMed

Lee, Ye-Na; Lee, Jong Seok; Han, Seung-Kyu; Jung, Hye-Kyung

Our group has reported that negative-pressure wound therapy (NPWT) decreases tissue oxygenation by 84% in the foot of diabetic patients because the pad of the connecting drainage tube and foam sponge of the NPWT system compress the wound bed. The purpose of this study was to determine whether an NPWT modified dressing application reduces tissue oxygenation in the feet of persons with diabetes mellitus. A prospective, clinical, observational study. We enrolled 30 patients with diabetic mellitus; their mean age was 63.9 ± 11.2 years (mean ± standard deviation). All were cared for at the diabetic wound center at an academic tertiary medical center in South Korea between 2014 and January 2015. Transcutaneous partial oxygen pressures (TcpO2) were measured to determine tissue oxygenation levels beneath modified NPWT dressings. A TcpO2 sensor was fixed at the tarsometatarsal area of the contralateral unwounded foot. A negative pressure of -125 mm Hg was applied until TcpO2 reached a plateau state; values were measured before, during, and after the modified NPWT. The Wilcoxon' and Mann-Whitney U tests were used to compare differences between these measurements. TcpO2 levels decreased by 26% during the modified NPWT. Mean TcpO2 values before, during, and after turning off the therapy were 54.3 ± 15.3 mm Hg, 41.6 ± 16.3 mm Hg, and 53.3 ± 15.6 mm Hg (P < .05), respectively. Applying NPWT without the pad of the connecting drainage tube significantly reduces the amount of tissue oxygenation loss beneath foam dressings on the skin of the foot dorsum in diabetic patients.

The Effects of Bougie Diameters on Tissue Oxygen Levels After Sleeve Gastrectomy: A Randomized Experimental Trial

PubMed

Konca, Can; Yılmaz, Ali Abbas; Çelik, Süleyman Utku; Kayılıoğlu, Selami Ilgaz; Paşaoğlu, Özge Tuğçe; Ceylan, Halil Arda; Genç, Volkan

2018-05-29

Staple-line leak is the most frightening complication of laparoscopic sleeve gastrectomy and several predisposing factors such as using improper staple sizes regardless of gastric wall thickness, narrower bougie diameter and ischemia of the staple line are asserted. To evaluate the effects of different bougie diameters on tissue oxygen partial pressure at the esophagogastric junction after sleeve gastrectomy. A randomized and controlled animal experiment with 1:1:1:1 allocation ratio. Thirty-two male Wistar Albino rats were randomly divided into 4 groups of 8 each. While 12-Fr bougies were used in groups 1 and 3, 8-Fr bougies were used in groups 2 and 4. Fibrin sealant application was also carried out around the gastrectomy line after sleeve gastrectomy in groups 3 and 4. Burst pressure of gastrectomy line, tissue oxygen partial pressure and hydroxyproline levels at the esophagogastric junction were measured and compared among groups. Mortality was detected in 2 out of 32 rats (6.25%) and one of them was in group 2 and the cause of this mortality was gastric leak. Gastric leak was detected in 2 out of 32 rats (6.25%). There was no significant difference in terms of burst pressures, tissue oxygen partial pressure and tissue hydroxyproline levels among the 4 groups. The use of narrower bougie along with fibrin sealant has not had a negative effect on tissue perfusion and wound healing.

A LED-based phosphorimeter for measurement of microcirculatory oxygen pressure.

PubMed

Guerci, Philippe; Ince, Yasin; Heeman, Paul; Faber, Dirk; Ergin, Bulent; Ince, Can

2017-02-01

Quantitative measurements of microcirculatory and tissue oxygenation are of prime importance in experimental research. The noninvasive phosphorescence quenching method has given further insight into the fundamental mechanisms of oxygen transport to healthy tissues and in models of disease. Phosphorimeters are devices dedicated to the study of phosphorescence quenching. The experimental applications of phosphorimeters range from measuring a specific oxygen partial pressure (Po 2 ) in cellular organelles such as mitochondria, finding values of Po 2 distributed over an organ or capillaries, to measuring microcirculatory Po 2 changes simultaneously in several organ systems. Most of the current phosphorimeters use flash lamps as a light excitation source. However, a major drawback of flash lamps is their inherent plasma glow that persists for tens of microseconds after the primary discharge. This complex distributed excitation pattern generated by the flash lamp can lead to inaccurate Po 2 readings unless a deconvolution analysis is performed. Using light-emitting diode (LED), a rectangular shaped light pulse can be generated that provides a more uniformly distributed excitation signal. This study presents the design and calibration process of an LED-based phosphorimeter (LED-P). The in vitro calibration of the LED-P using palladium(II)-meso-tetra(4-carboxyphenyl)-porphyrin (Pd-TCCP) as a phosphorescent dye is presented. The pH and temperature were altered to assess whether the decay times of the Pd-TCCP measured by the LED-P were significantly influenced. An in vivo validation experiment was undertaken to measure renal cortical Po 2 in a rat subjected to hypoxic ventilation conditions and ischemia/reperfusion. The benefits of using LEDs as a light excitation source are presented. Copyright © 2017 the American Physiological Society.

Predicting Intracranial Pressure and Brain Tissue Oxygen Crises in Patients With Severe Traumatic Brain Injury.

PubMed

Myers, Risa B; Lazaridis, Christos; Jermaine, Christopher M; Robertson, Claudia S; Rusin, Craig G

2016-09-01

To develop computer algorithms that can recognize physiologic patterns in traumatic brain injury patients that occur in advance of intracranial pressure and partial brain tissue oxygenation crises. The automated early detection of crisis precursors can provide clinicians with time to intervene in order to prevent or mitigate secondary brain injury. A retrospective study was conducted from prospectively collected physiologic data. intracranial pressure, and partial brain tissue oxygenation crisis events were defined as intracranial pressure of greater than or equal to 20 mm Hg lasting at least 15 minutes and partial brain tissue oxygenation value of less than 10 mm Hg for at least 10 minutes, respectively. The physiologic data preceding each crisis event were used to identify precursors associated with crisis onset. Multivariate classification models were applied to recorded data in 30-minute epochs of time to predict crises between 15 and 360 minutes in the future. The neurosurgical unit of Ben Taub Hospital (Houston, TX). Our cohort consisted of 817 subjects with severe traumatic brain injury. Our algorithm can predict the onset of intracranial pressure crises with 30-minute advance warning with an area under the receiver operating characteristic curve of 0.86 using only intracranial pressure measurements and time since last crisis. An analogous algorithm can predict the start of partial brain tissue oxygenation crises with 30-minute advanced warning with an area under the receiver operating characteristic curve of 0.91. Our algorithms provide accurate and timely predictions of intracranial hypertension and tissue hypoxia crises in patients with severe traumatic brain injury. Almost all of the information needed to predict the onset of these events is contained within the signal of interest and the time since last crisis.

Comparison of adenosine, isoflurane, and desflurane on myocardial tissue oxygen pressure during coronary artery constriction in dogs.

PubMed

Hoffman, William E; Albrecht, Ronald F; Jonjev, Zivojin S

2003-08-01

To compare adenosine-, isoflurane-, or desflurane-induced hypotension with and without left anterior descending (LAD) coronary artery constriction for the effects on myocardial tissue oxygen pressure (PmO(2)) in dogs. Prospective, randomized, nonblinded. University teaching hospital. Male nonpurpose-bred dogs (n = 18). Dogs were anesthetized with 1.5% isoflurane (n = 12) or 8% desflurane (n = 6). A flow probe and balloon occluder were placed on the LAD artery. A probe that measured myocardial oxygen pressure was inserted into the middle myocardium in the LAD region. Myocardial oxygen consumption (MVO(2)) was calculated as LAD flow x arterial minus coronary sinus oxygen content. Measures were made during hypotension produced by adenosine infusion, 2.8% isoflurane, or 14% desflurane with and without LAD constriction to decrease blood flow 30%. Without LAD artery constriction, adenosine infusion increased LAD flow 90% and MVO(2) 70%, 2.8% isoflurane produced no change in MVO(2), and 14% desflurane decreased MVO(2) 25%, but no treatment changed PmO(2). LAD artery constriction decreased PmO(2) 50% by itself. Adenosine infusion during LAD constriction decreased tissue oxygen pressure an additional 60%, 2.8% isoflurane produced no change, and 14% desflurane increased PmO(2) 100%. There was an inverse relationship between the effect of adenosine, 2.8% isoflurane, and 14% desflurane on MVO(2) and PmO(2) during ischemia. This is consistent with reports that increasing oxygen demand worsens myocardial ischemia.

Phosphorescent nanoparticles for quantitative measurements of oxygen profiles in vitro and in vivo

PubMed Central

Choi, Nak Won; Verbridge, Scott S.; Williams, Rebecca M.; Chen, Jin; Kim, Ju-Young; Schmehl, Russel; Farnum, Cornelia E.; Zipfel, Warren R.; Fischbach, Claudia; Stroock, Abraham D.

2012-01-01

We present the development and characterization of nanoparticles loaded with a custom phosphor; we exploit these nanoparticles to perform quantitative measurements of the concentration of oxygen within three-dimensional (3-D) tissue cultures in vitro and blood vessels in vivo. We synthesized a customized ruthenium (Ru)-phosphor and incorporated it into polymeric nanoparticles via self-assembly. We demonstrate that the encapsulated phosphor is non-toxic with and without illumination. We evaluated two distinct modes of employing the phosphorescent nanoparticles for the measurement of concentrations of oxygen: 1) in vitro, in a 3-D microfluidic tumor model via ratiometric measurements of intensity with an oxygen-insensitive fluorophore as a reference, and 2) in vivo, in mouse vasculature using measurements of phosphorescence lifetime. With both methods, we demonstrated micrometer-scale resolution and absolute calibration to the dissolved oxygen concentration. Based on the ease and customizability of the synthesis of the nanoparticles and the flexibility of their application, these oxygen-sensing polymeric nanoparticles will find a natural home in a range of biological applications, benefiting studies of physiological as well as pathological processes in which oxygen availability and concentration play a critical role. PMID:22240511

Effects of acupuncture on tissue oxygenation of the rat brain.

PubMed

Chen, G S; Erdmann, W

1978-04-01

Acupuncture has been claimed to be effective in restoring consciousness in some comatose patients. Possible mechanisms to explain alleged acupuncture-induced arousal may include vasodilatory effects caused by smypathetic stimulation which leads to an augmentation of cerebral microcirculation and thereby improves oxygen supply to the brain tissue. Experiments were performed in ten albino rats (Wistar) employing PO2 microelectrodes which were inserted into the cortex through small burholes. Brain tissue PO2 was continuously recorded before, during, and after acupuncture. Stimulation of certain acupuncture points (Go-26) resulted in immediate increase of PO2 in the frontal cortex of the rat brain. This effect was reproducible and was comparable to that obtained with increase of inspiratory CO2 known to induce arterial vasodilatation and thus capillary perfusion pressure. The effect was more significant as compared to tissue PO2 increases obtained after increase in inspiratory oxygen concentration from 21% to 100%. It appears that acupuncture causes increased brain tissue perfusion which may be, at least in part, responsible for arousal of unconscious patients.

Why is the partial oxygen pressure of human tissues a crucial parameter? Small molecules and hypoxia

PubMed Central

Carreau, Aude; Hafny-Rahbi, Bouchra El; Matejuk, Agata; Grillon, Catherine; Kieda, Claudine

2011-01-01

Abstract Oxygen supply and diffusion into tissues are necessary for survival. The oxygen partial pressure (pO2), which is a key component of the physiological state of an organ, results from the balance between oxygen delivery and its consumption. In mammals, oxygen is transported by red blood cells circulating in a well-organized vasculature. Oxygen delivery is dependent on the metabolic requirements and functional status of each organ. Consequently, in a physiological condition, organ and tissue are characterized by their own unique ‘tissue normoxia’ or ‘physioxia’ status. Tissue oxygenation is severely disturbed during pathological conditions such as cancer, diabetes, coronary heart disease, stroke, etc., which are associated with decrease in pO2, i.e. ‘hypoxia’. In this review, we present an array of methods currently used for assessing tissue oxygenation. We show that hypoxia is marked during tumour development and has strong consequences for oxygenation and its influence upon chemotherapy efficiency. Then we compare this to physiological pO2 values of human organs. Finally we evaluate consequences of physioxia on cell activity and its molecular modulations. More importantly we emphasize the discrepancy between in vivo and in vitro tissue and cells oxygen status which can have detrimental effects on experimental outcome. It appears that the values corresponding to the physioxia are ranging between 11% and 1% O2 whereas current in vitro experimentations are usually performed in 19.95% O2, an artificial context as far as oxygen balance is concerned. It is important to realize that most of the experiments performed in so-called normoxia might be dangerously misleading. PMID:21251211

[Tissue oxygen saturation in the critically ill patient].

PubMed

Gruartmoner, G; Mesquida, J; Baigorri, F

2014-05-01

Hemodynamic resuscitation seeks to correct global macrocirculatory parameters of pressure and flow. However, current evidence has shown that despite the normalization of these global parameters, microcirculatory and regional perfusion alterations can persist, and these alterations have been independently associated with a poorer patient prognosis. This in turn has lead to growing interest in new technologies for exploring regional circulation and microcirculation. Near infra-red spectroscopy allows us to monitor tissue oxygen saturation, and has been proposed as a noninvasive, continuous and easy-to-obtain measure of regional circulation. The present review aims to summarize the existing evidence on near infra-red spectroscopy and its potential clinical role in the resuscitation of critically ill patients in shock. Copyright © 2013 Elsevier España, S.L. and SEMICYUC. All rights reserved.

Contrast enhancement for in vivo visible reflectance imaging of tissue oxygenation.

PubMed

Crane, Nicole J; Schultz, Zachary D; Levin, Ira W

2007-08-01

Results are presented illustrating a straightforward algorithm to be used for real-time monitoring of oxygenation levels in blood cells and tissue based on the visible spectrum of hemoglobin. Absorbance images obtained from the visible reflection of white light through separate red and blue bandpass filters recorded by monochrome charge-coupled devices (CCDs) are combined to create enhanced images that suggest a quantitative correlation between the degree of oxygenated and deoxygenated hemoglobin in red blood cells. The filter bandpass regions are chosen specifically to mimic the color response of commercial 3-CCD cameras, representative of detectors with which the operating room laparoscopic tower systems are equipped. Adaptation of this filter approach is demonstrated for laparoscopic donor nephrectomies in which images are analyzed in terms of real-time in vivo monitoring of tissue oxygenation.

Tissue oxygen monitoring by photoacoustic lifetime imaging (PALI) and its application to image-guided photodynamic therapy (PDT)

NASA Astrophysics Data System (ADS)

Shao, Qi; Morgounova, Ekaterina; Ashkenazi, Shai

2015-03-01

The oxygen partial pressure (pO2), which results from the balance between oxygen delivery and its consumption, is a key component of the physiological state of a tissue. Images of oxygen distribution can provide essential information for identifying hypoxic tissue and optimizing cancer treatment. Previously, we have reported a noninvasive in vivo imaging modality based on photoacoustic lifetime. The technique maps the excited triplet state of oxygen-sensitive dye, thus reflects the spatial and temporal distribution of tissue oxygen. We have applied PALI on tumor on small animals to identify hypoxia area. We also showed that PALI is able monitor changes of tissue oxygen, in an acute ischemia and breathing modulation model. Here we present our work on developing a treatment/imaging modality (PDT-PALI) that integrates PDT and a combined ultrasound/photoacoustic imaging system. The system provides real-time feedback of three essential parameters namely: tissue oxygen, light penetration in tumor location, and distribution of photosensitizer. Tissue oxygen imaging is performed by applying PALI, which relies on photoacoustic probing of oxygen-dependent, excitation lifetime of Methylene Blue (MB) photosensitizer. Lifetime information can also be used to generate image showing the distribution of photosensitizer. The level and penetration depth of PDT illumination can be deduced from photoacoustic imaging at the same wavelength. All images will be combined with ultrasound B-mode images for anatomical reference.

Effects of different acute hypoxic regimens on tissue oxygen profiles and metabolic outcomes.

PubMed

Reinke, Christian; Bevans-Fonti, Shannon; Drager, Luciano F; Shin, Mi-Kyung; Polotsky, Vsevolod Y

2011-09-01

Obstructive sleep apnea (OSA) causes intermittent hypoxia (IH) during sleep. Both obesity and OSA are associated with insulin resistance and systemic inflammation, which may be attributable to tissue hypoxia. We hypothesized that a pattern of hypoxic exposure determines both oxygen profiles in peripheral tissues and systemic metabolic outcomes, and that obesity has a modifying effect. Lean and obese C57BL6 mice were exposed to 12 h of intermittent hypoxia 60 times/h (IH60) [inspired O₂ fraction (Fi(O₂)) 21-5%, 60/h], IH 12 times/h (Fi(O₂) 5% for 15 s, 12/h), sustained hypoxia (SH; Fi(O₂) 10%), or normoxia while fasting. Tissue oxygen partial pressure (Pti(O₂)) in liver, skeletal muscle and epididymal fat, plasma leptin, adiponectin, insulin, blood glucose, and adipose tumor necrosis factor-α (TNF-α) were measured. In lean mice, IH60 caused oxygen swings in the liver, whereas fluctuations of Pti(O₂) were attenuated in muscle and abolished in fat. In obese mice, baseline liver Pti(O₂) was lower than in lean mice, whereas muscle and fat Pti(O₂) did not differ. During IH, Pti(O₂) was similar in obese and lean mice. All hypoxic regimens caused insulin resistance. In lean mice, hypoxia significantly increased leptin, especially during SH (44-fold); IH60, but not SH, induced a 2.5- to 3-fold increase in TNF-α secretion by fat. Obesity was associated with striking increases in leptin and TNF-α, which overwhelmed effects of hypoxia. In conclusion, IH60 led to oxygen fluctuations in liver and muscle and steady hypoxia in fat. IH and SH induced insulin resistance, but inflammation was increased only by IH60 in lean mice. Obesity caused severe inflammation, which was not augmented by acute hypoxic regimens.

Effects of different acute hypoxic regimens on tissue oxygen profiles and metabolic outcomes

PubMed Central

Bevans-Fonti, Shannon; Drager, Luciano F.; Shin, Mi-Kyung; Polotsky, Vsevolod Y.

2011-01-01

Obstructive sleep apnea (OSA) causes intermittent hypoxia (IH) during sleep. Both obesity and OSA are associated with insulin resistance and systemic inflammation, which may be attributable to tissue hypoxia. We hypothesized that a pattern of hypoxic exposure determines both oxygen profiles in peripheral tissues and systemic metabolic outcomes, and that obesity has a modifying effect. Lean and obese C57BL6 mice were exposed to 12 h of intermittent hypoxia 60 times/h (IH60) [inspired O2 fraction (FiO2) 21–5%, 60/h], IH 12 times/h (FiO2 5% for 15 s, 12/h), sustained hypoxia (SH; FiO2 10%), or normoxia while fasting. Tissue oxygen partial pressure (PtiO2) in liver, skeletal muscle and epididymal fat, plasma leptin, adiponectin, insulin, blood glucose, and adipose tumor necrosis factor-α (TNF-α) were measured. In lean mice, IH60 caused oxygen swings in the liver, whereas fluctuations of PtiO2 were attenuated in muscle and abolished in fat. In obese mice, baseline liver PtiO2 was lower than in lean mice, whereas muscle and fat PtiO2 did not differ. During IH, PtiO2 was similar in obese and lean mice. All hypoxic regimens caused insulin resistance. In lean mice, hypoxia significantly increased leptin, especially during SH (44-fold); IH60, but not SH, induced a 2.5- to 3-fold increase in TNF-α secretion by fat. Obesity was associated with striking increases in leptin and TNF-α, which overwhelmed effects of hypoxia. In conclusion, IH60 led to oxygen fluctuations in liver and muscle and steady hypoxia in fat. IH and SH induced insulin resistance, but inflammation was increased only by IH60 in lean mice. Obesity caused severe inflammation, which was not augmented by acute hypoxic regimens. PMID:21737828

Effect of oxygen breathing on micro oxygen bubbles in nitrogen-depleted rat adipose tissue at sea level and 25 kPa altitude exposures.

PubMed

Randsoe, Thomas; Hyldegaard, Ole

2012-08-01

The standard treatment of altitude decompression sickness (aDCS) caused by nitrogen bubble formation is oxygen breathing and recompression. However, micro air bubbles (containing 79% nitrogen), injected into adipose tissue, grow and stabilize at 25 kPa regardless of continued oxygen breathing and the tissue nitrogen pressure. To quantify the contribution of oxygen to bubble growth at altitude, micro oxygen bubbles (containing 0% nitrogen) were injected into the adipose tissue of rats depleted from nitrogen by means of preoxygenation (fraction of inspired oxygen = 1.0; 100%) and the bubbles studied at 101.3 kPa (sea level) or at 25 kPa altitude exposures during continued oxygen breathing. In keeping with previous observations and bubble kinetic models, we hypothesize that oxygen breathing may contribute to oxygen bubble growth at altitude. Anesthetized rats were exposed to 3 h of oxygen prebreathing at 101.3 kPa (sea level). Micro oxygen bubbles of 500-800 nl were then injected into the exposed abdominal adipose tissue. The oxygen bubbles were studied for up to 3.5 h during continued oxygen breathing at either 101.3 or 25 kPa ambient pressures. At 101.3 kPa, all bubbles shrank consistently until they disappeared from view at a net disappearance rate (0.02 mm(2) × min(-1)) significantly faster than for similar bubbles at 25 kPa altitude (0.01 mm(2) × min(-1)). At 25 kPa, most bubbles initially grew for 2-40 min, after which they shrank and disappeared. Four bubbles did not disappear while at 25 kPa. The results support bubble kinetic models based on Fick's first law of diffusion, Boyles law, and the oxygen window effect, predicting that oxygen contributes more to bubble volume and growth during hypobaric conditions. As the effect of oxygen increases, the lower the ambient pressure. The results indicate that recompression is instrumental in the treatment of aDCS.

Assessment of tissue oxygenation of periodontal inflammation in smokers using optical spectroscopy.

PubMed

Liu, Kan-Zhi; Duarte, Poliana Mendes; Santos, Vanessa Renata; Xiang, Xiaoming; Xu, Minqi; Miranda, Tamires Szeremeske; Fermiano, Daiane; Gonçalves, Tiago Eduardo Dias; Sowa, Micheal G

2014-04-01

We have recently developed a periodontal diagnostic tool that was validated in non-smokers with periodontitis. Tobacco smoking is a recognized risk factor for periodontal diseases that can mask gingival bleeding and lead to a false negative diagnosis. Therefore, the purpose of current study is to further validate this instrument in smokers with periodontal diseases. Using a portable optical near-infrared spectrometer, optical spectra were obtained, processed and evaluated from healthy (n = 108), gingivitis (n = 100), and periodontitis (n = 79) sites of 54 systemically healthy smokers. A modified Beer-Lambert unmixing model that incorporates a non-parametric scattering loss function was used to determine the relative contribution of deoxygenated haemoglobin (Hb) and oxygenated haemoglobin (HbO2 ) to the overall spectrum. The balance between tissue oxygen delivery and utilization in periodontal tissues was then assessed. Tissue oxygen saturation was significantly decreased in the gingivitis (p = 0.016) and periodontitis (p = 0.007) sites, compared to the healthy sites. There was a trend towards increased concentration of Hb and decreased concentration of HbO2 from healthy to diseased sites, without statistical significance (p > 0.05). Optical spectroscopy can determine tissue oxygenation profiles of healthy and diseased sites in smokers. The spectral profile of periodontal sites in smokers generally resembles those from non-smoking patients. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Why is the partial oxygen pressure of human tissues a crucial parameter? Small molecules and hypoxia.

PubMed

Carreau, Aude; El Hafny-Rahbi, Bouchra; Matejuk, Agata; Grillon, Catherine; Kieda, Claudine

2011-06-01

Oxygen supply and diffusion into tissues are necessary for survival. The oxygen partial pressure (pO(2)), which is a key component of the physiological state of an organ, results from the balance between oxygen delivery and its consumption. In mammals, oxygen is transported by red blood cells circulating in a well-organized vasculature. Oxygen delivery is dependent on the metabolic requirements and functional status of each organ. Consequently, in a physiological condition, organ and tissue are characterized by their own unique 'tissue normoxia' or 'physioxia' status. Tissue oxygenation is severely disturbed during pathological conditions such as cancer, diabetes, coronary heart disease, stroke, etc., which are associated with decrease in pO(2), i.e. 'hypoxia'. In this review, we present an array of methods currently used for assessing tissue oxygenation. We show that hypoxia is marked during tumour development and has strong consequences for oxygenation and its influence upon chemotherapy efficiency. Then we compare this to physiological pO(2) values of human organs. Finally we evaluate consequences of physioxia on cell activity and its molecular modulations. More importantly we emphasize the discrepancy between in vivo and in vitro tissue and cells oxygen status which can have detrimental effects on experimental outcome. It appears that the values corresponding to the physioxia are ranging between 11% and 1% O(2) whereas current in vitro experimentations are usually performed in 19.95% O(2), an artificial context as far as oxygen balance is concerned. It is important to realize that most of the experiments performed in so-called normoxia might be dangerously misleading. © 2011 The Authors Journal of Cellular and Molecular Medicine © 2011 Foundation for Cellular and Molecular Medicine/Blackwell Publishing Ltd.

Axial oxygen diffusion in the Krogh model: modifications to account for myocardial oxygen tension in isolated perfused rat hearts measured by EPR oximetry.

PubMed

Grinberg, Oleg; Novozhilov, Boris; Grinberg, Stalina; Friedman, Bruce; Swartz, Harold M

2005-01-01

The cylindrical steady-state model developed by Krogh with Erlang has served as the basis of understanding oxygen supply in living tissue for over eighty years. Due to its simplicity and agreement with some observations, it has been extensively used and successfully extended to new fields, especially for situations such as drug diffusion, water transport, and ice formation in tissues. However, the applicability of the model to make even a qualitative prediction of the oxygen level of specific volumes of the tissue is still controversial. We recently have developed an approximate analytical solution of a steady-state diffusion equation for a Krogh cylinder, including oxygen concentration in the capillary. This model was used to explain our previous experimental data on myocardial pO2 in isolated perfused rat hearts measured by EPR oximetry. An acceptable agreement with the experimental data was obtained by assuming that a known limitation of the existing EPR methods--a tendency to over-weight low pO2 values--had resulted in an under-estimate of the pO2. These results are consistent with recent results of others, which stress the importance of taking into account the details of what is measured by various methods.

Development of an oxygen saturation measuring system by using near-infrared spectroscopy

NASA Astrophysics Data System (ADS)

Kono, K.; Nakamachi, E.; Morita, Y.

2017-08-01

Recently, the hypoxia imaging has been recognized as the advanced technique to detect cancers because of a strong relationship with the biological characterization of cancer. In previous studies, hypoxia imaging systems for endoscopic diagnosis have been developed. However, these imaging technologies using the visible light can observe only blood vessels in gastric mucous membrane. Therefore, they could not detect scirrhous gastric cancer which accounts for 10% of all gastric cancers and spreads rapidly into submucous membrane. To overcome this problem, we developed a measuring system of blood oxygen saturation in submucous membrane by using near-infrared (NIR) spectroscopy. NIR, which has high permeability for bio-tissues and high absorbency for hemoglobin, can image and observe blood vessels in submucous membrane. NIR system with LED lights and a CCD camera module was developed to image blood vessels. We measured blood oxygen saturation using the optical density ratio (ODR) of two wavelengths, based on Lambert-Beer law. To image blood vessel clearly and measure blood oxygen saturation accurately, we searched two optimum wavelengths by using a multilayer human gastric-like phantom which has same optical properties as human gastric one. By using Monte Carlo simulation of light propagation, we derived the relationship between the ODR and blood oxygen saturation and elucidated the influence of blood vessel depth on measuring blood oxygen saturation. The oxygen saturation measuring methodology was validated with experiments using our NIR system. Finally, it was confirmed that our system can detect oxygen saturation in various depth blood vessels accurately.

Oxygen measurement in interstitially perfused cellularized constructs cultured in a miniaturized bioreactor.

PubMed

Raimondi, Manuela T; Giordano, Carmen; Pietrabissa, Riccardo

2015-12-18

The possibility of developing engineered tissue in vitro and maintaining the cell viability and functionality is primarily related to the possibility of controlling key culture parameters such as oxygen concentration and cell-specific oxygen consumption. We measured these parameters in a three-dimensional (3D) cellularized construct maintained under interstitially perfused culture in a miniaturized bioreactor. MG63 osteosarcoma cells were seeded at high density on a 3D polystyrene scaffold. The 3D scaffolds were sensorized with sensor foils made of a polymer, which fluoresce with intensity proportional to the local oxygen tension. Images of the sensor foil in contact with the cellularized construct were acquired with a video camera every four hours for six culture days and were elaborated with analytical imaging software to obtain oxygen concentration maps. The data collected indicate a globally decreasing oxygen concentration profile, with a total drop of 28% after six days of culture and an average drop of 10.5% between the inlet and outlet of the perfused construct. Moreover, by importing the measured oxygen concentration data and the cell counts in a model of mass transport, we calculated the cell-specific oxygen consumption over the whole culture period. The consumption increased with oxygen availability and ranged from 0.1 to 0.7 µmol/h/106 cells. The sensors used here allowed a non-invasive, contamination-free and non-destructive oxygen measurement over the whole culture period. This study is the basis for optimization of the culture parameters involved in oxygen supply, in order to guarantee maintenance of cell viability in our system.

Reactive Oxygen Species in Inflammation and Tissue Injury

PubMed Central

Mittal, Manish; Siddiqui, Mohammad Rizwan; Tran, Khiem; Reddy, Sekhar P.

2014-01-01

Abstract Reactive oxygen species (ROS) are key signaling molecules that play an important role in the progression of inflammatory disorders. An enhanced ROS generation by polymorphonuclear neutrophils (PMNs) at the site of inflammation causes endothelial dysfunction and tissue injury. The vascular endothelium plays an important role in passage of macromolecules and inflammatory cells from the blood to tissue. Under the inflammatory conditions, oxidative stress produced by PMNs leads to the opening of inter-endothelial junctions and promotes the migration of inflammatory cells across the endothelial barrier. The migrated inflammatory cells not only help in the clearance of pathogens and foreign particles but also lead to tissue injury. The current review compiles the past and current research in the area of inflammation with particular emphasis on oxidative stress-mediated signaling mechanisms that are involved in inflammation and tissue injury. Antioxid. Redox Signal. 20, 1126–1167. PMID:23991888

Measuring Transcutaneous Oxygenation to Validate the Duration Required to Achieve Electrode Equilibration.

PubMed

Chiang, Nathaniel; Jain, Jitendra K; Sleigh, Jamie; Vasudevan, Thodur

2018-06-01

The transcutaneous oxygenation measurement (TCOM) system is useful in assessing tissue viability. There are no clear recommendations regarding the duration required for the electrode to equilibrate and reliably evaluate tissue oxygenation values. The objective of this study was to validate the duration required to achieve electrode equilibration in a clinical setting. Minute-by-minute recordings using TCOM (TCOM3; Radiometer Medical ApS, Brønshøj, Copenhagen) were obtained for 82 limbs in 50 participants. Twenty-five limbs were in patients with peripheral vascular disease; 30 were in patients with no known peripheral vascular disease; and 27 were in healthy volunteers. Transcutaneous partial pressure of oxygen and carbon dioxide (TcPO2 and TcPCO2) were recorded over a 15-minute period. Participants' TcPO2 decreased and TcPCO2 increased over time. Both changed in a nonlinear fashion, eventually settling at an "equilibrium" where the measurements became stable. The difference in proportional change of TcPO2 between minutes 14 and 15 was 0.8%, and for TcPCO2was 2.9%. Changes in TCOM measurements over time were similar among the 3 groups. This is the first study to target minute-by-minute variation in TcPO2 and TcPCO2 measurements. Recording for a minimum of 15 minutes allows a reliable period for the TCOM electrode to equilibrate to record absolute values and determine wound healing potential.

Oxygen consumption rate of early pre-antral follicles from vitrified human ovarian cortical tissue

PubMed Central

ISHIKAWA, Takayuki; KYOYA, Toshihiko; NAKAMURA, Yusuke; SATO, Eimei; TOMIYAMA, Tatsuhiro; KYONO, Koichi

2014-01-01

The study of human ovarian tissue transplantation and cryopreservation has advanced significantly. Autotransplantation of human pre-antral follicles isolated from cryopreserved cortical tissue is a promising option for the preservation of fertility in young cancer patients. The purpose of the present study was to reveal the effect of vitrification after low-temperature transportation of human pre-antral follicles by using the oxygen consumption rate (OCR). Cortical tissues from 9 ovaries of female-to-male transsexuals were vitrified after transportation (6 or 18 h). The follicles were enzymatically isolated from nonvitrified tissue (group I, 18 h of transportation), vitrified-warmed tissue (group II, 6 and 18 h of transportation) and vitrified-warmed tissue that had been incubated for 24 h (group III, 6 and 18 h of transportation). OCR measurement and the LIVE/DEAD viability assay were performed. Despite the ischemic condition, the isolated pre-antral follicles in group I consumed oxygen, and the mean OCRs increased with developmental stage. Neither the transportation time nor patient age seemed to affect the OCR in this group. Meanwhile, the mean OCR was significantly lower (P < 0.05) in group II but was comparable to that of group I after 24 h of incubation. The integrity of vitrified-warmed primordial and primary follicles was clearly corroborated by the LIVE/DEAD viability assay. These results demonstrate that the OCR can be used to directly estimate the effect of vitrification on the viability of primordial and primary follicles and to select the viable primordial and primary follicles from vitrified-warmed follicles. PMID:25262776

In Vivo Mitochondrial Oxygen Tension Measured by a Delayed Fluorescence Lifetime Technique

PubMed Central

Mik, Egbert G.; Johannes, Tanja; Zuurbier, Coert J.; Heinen, Andre; Houben-Weerts, Judith H. P. M.; Balestra, Gianmarco M.; Stap, Jan; Beek, Johan F.; Ince, Can

2008-01-01

Mitochondrial oxygen tension (mitoPO2) is a key parameter for cellular function, which is considered to be affected under various pathophysiological circumstances. Although many techniques for assessing in vivo oxygenation are available, no technique for measuring mitoPO2 in vivo exists. Here we report in vivo measurement of mitoPO2 and the recovery of mitoPO2 histograms in rat liver by a novel optical technique under normal and pathological circumstances. The technique is based on oxygen-dependent quenching of the delayed fluorescence lifetime of protoporphyrin IX. Application of 5-aminolevulinic acid enhanced mitochondrial protoporphyrin IX levels and induced oxygen-dependent delayed fluorescence in various tissues, without affecting mitochondrial respiration. Using fluorescence microscopy, we demonstrate in isolated hepatocytes that the signal is of mitochondrial origin. The delayed fluorescence lifetime was calibrated in isolated hepatocytes and isolated perfused livers. Ultimately, the technique was applied to measure mitoPO2 in rat liver in vivo. The results demonstrate mitoPO2 values of ∼30–40 mmHg. mitoPO2 was highly sensitive to small changes in inspired oxygen concentration around atmospheric oxygen level. Ischemia-reperfusion interventions showed altered mitoPO2 distribution, which flattened overall compared to baseline conditions. The reported technology is scalable from microscopic to macroscopic applications, and its reliance on an endogenous compound greatly enhances its potential field of applications. PMID:18641065

Oxygen Nanobubble Tracking by Light Scattering in Single Cells and Tissues.

PubMed

Bhandari, Pushpak; Wang, Xiaolei; Irudayaraj, Joseph

2017-03-28

Oxygen nanobubbles (ONBs) have significant potential in targeted imaging and treatment in cancer diagnosis and therapy. Precise localization and tracking of single ONBs is demonstrated based on hyperspectral dark-field microscope (HSDFM) to image and track single oxygen nanobubbles in single cells. ONBs were proposed as promising contrast-generating imaging agents due to their strong light scattering generated from nonuniformity of refractive index at the interface. With this powerful platform, we have revealed the trajectories and quantities of ONBs in cells, and demonstrated the relation between the size and diffusion coefficient. We have also evaluated the presence of ONBs in the nucleus with respect to an increase in incubation time and have quantified the uptake in single cells in ex vivo tumor tissues. Our results demonstrate that HSDFM can be a versatile platform to detect and measure cellulosic nanoparticles at the single-cell level and to assess the dynamics and trajectories of this delivery system.

Differences in GFR and Tissue Oxygenation, and Interactions between Stenotic and Contralateral Kidneys in Unilateral Atherosclerotic Renovascular Disease.

PubMed

Herrmann, Sandra M S; Saad, Ahmed; Eirin, Alfonso; Woollard, John; Tang, Hui; McKusick, Michael A; Misra, Sanjay; Glockner, James F; Lerman, Lilach O; Textor, Stephen C

2016-03-07

Atherosclerotic renal artery stenosis (ARAS) can reduce renal blood flow, tissue oxygenation, and GFR. In this study, we sought to examine associations between renal hemodynamics and tissue oxygenation with single-kidney function, pressor hormones, and inflammatory biomarkers in patients with unilateral ARAS undergoing medical therapy alone or stent revascularization. Nonrandomized inpatient studies were performed in patients with unilateral ARAS (>60% occlusion) before and 3 months after revascularization (n=10) or medical therapy (n=20) or patients with essential hypertension (n=32) under identical conditions. The primary study outcome was change in single-kidney GFR. Individual kidney hemodynamics and volume were measured using multidetector computed tomography. Tissue oxygenation (using R(2)* as a measure of deoxyhemoglobin) was determined by blood oxygen level-dependent magnetic resonance imaging at 3 T. Renal vein neutrophil gelatinase-associated lipocalin (NGAL), monocyte chemoattractant protein-1 (MCP-1), and plasma renin activity were measured. Total GFR did not change over 3 months in either group, but the stenotic kidney (STK) GFR rose over time in the stent compared with the medical group (+2.2[-1.8 to 10.5] versus -5.3[-7.3 to -0.3] ml/min; P=0.03). Contralateral kidney (CLK) GFR declined in the stent group (43.6±19.7 to 36.6±19.5 ml/min; P=0.03). Fractional tissue hypoxia fell in the STK (fraction R(2)* >30/s: 22.1%±20% versus 14.9%±18.3%; P<0.01) after stenting. Renal vein biomarkers correlated with the degree of hypoxia in the STK: NGAL(r=0.3; P=0.01) and MCP-1(r=0.3; P=0.02; more so after stenting). Renal vein NGAL was inversely related to renal blood flow in the STK (r=-0.65; P<0.001). Biomarkers were highly correlated between STK and CLK, NGAL (r=0.94; P<0.001), and MCP-1 (r=0.96; P<0.001). These results showed changes over time in single-kidney GFR that were not evident in parameters of total GFR. Furthermore, they delineate the relationship

Effects of acupuncture on tissue-oxygenation of the rat brain.

PubMed

Chen, G S; Erdmann, W

1977-01-01

Acupuncture has been claimed to be effective in restoring consciousness in some comatose patients. Possible mechanisms to explain alleged acupuncture-induced arousal may include vasodilatory effects caused by sympathetic stimulation which leads to an augmentation of cerebral microcirculation and thereby improves oxygen supply to the brain tissue. Experiments were performed in ten albino rats (Wistar) employing PO2 microelectrodes which were inserted into the cortex of the animals through small burholes. Brain tissue PO2 was continuously recorded before, during, and after acupuncture. Stimulation of certain acupuncture loci (Go-26) resulted in immediate increase of PO2 in the frontal cortex of the rat brain. This effect was reproducible. The effect was comparable to that obtained with increase of inspiratory CO2 known to induce arterial vasodilatation and thus capillary perfusion pressure. The effect was more significant as compared to tissue PO2 increases obtained after increase of inspiratory oxygen concentration from 21% to 100%. It appears that acupuncture causes an increase of brain tissue perfusion which may be, at least in part, responsible for arousal of unconscious patients. Dilatation of cerebral vascular vessels and improvement of autoregulation in the brain by acupuncture stimulation may also explain the effectiveness of acupuncture in the treatment of migraine headache.

Influence of tissue metabolism and capillary oxygen supply on arteriolar oxygen transport: a computational model.

PubMed

Moschandreou, T E; Ellis, C G; Goldman, D

2011-07-01

We present a theoretical model for steady-state radial and longitudinal oxygen transport in arterioles containing flowing blood (plasma and red blood cells) and surrounded by living tissue. This model combines a detailed description of convective and diffusive oxygen transport inside the arteriole with a novel boundary condition at the arteriolar lumen surface, and the results provide new mass transfer coefficients for computing arteriolar O(2) losses based on far-field tissue O(2) tension and in the presence of spatially distributed capillaries. A numerical procedure is introduced for calculating O(2) diffusion from an arteriole to a continuous capillary-tissue matrix immediately adjacent to the arteriole. The tissue O(2) consumption rate is assumed to be constant and capillaries act as either O(2) sources or sinks depending on the local O(2) environment. Using the model, O(2) saturation (SO(2)) and tension (PO(2)) are determined for the intraluminal region of the arteriole, as well as for the extraluminal region in the neighbouring tissue. Our model gives results that are consistent with available experimental data and previous intraluminal transport models, including appreciable radial decreases in intraluminal PO(2) for all vessel diameters considered (12-100 μm) and slower longitudinal decreases in PO(2) for larger vessels than for smaller ones, and predicts substantially less diffusion of O(2) from arteriolar blood than do models with PO(2) specified at the edge of the lumen. The dependence of the new mass transfer coefficients on vessel diameter, SO(2) and far-field PO(2) is calculated allowing their application to a wide range of physiological situations. This novel arteriolar O(2) transport model will be a vital component of future integrated models of microvascular regulation of O(2) supply to capillary beds and the tissue regions they support. Copyright © 2011 Elsevier Inc. All rights reserved.

Noninvasive oxygen partial pressure measurement of human body fluids in vivo using magnetic resonance imaging.

PubMed

Zaharchuk, Greg; Busse, Reed F; Rosenthal, Guy; Manley, Geoffery T; Glenn, Orit A; Dillon, William P

2006-08-01

The oxygen partial pressure (pO2) of human body fluids reflects the oxygenation status of surrounding tissues. All existing fluid pO2 measurements are invasive, requiring either microelectrode/optode placement or fluid removal. The purpose of this study is to develop a noninvasive magnetic resonance imaging method to measure the pO2 of human body fluids. We developed an imaging paradigm that exploits the paramagnetism of molecular oxygen to create quantitative images of fluid oxygenation. A single-shot fast spin echo pulse sequence was modified to minimize artifacts from motion, fluid flow, and partial volume. Longitudinal relaxation rate (R1 = 1/T1) was measured with a time-efficient nonequilibrium saturation recovery method and correlated with pO2 measured in phantoms. pO2 images of human and fetal cerebrospinal fluid, bladder urine, and vitreous humor are presented and quantitative oxygenation levels are compared with prior literature estimates, where available. Significant pO2 increases are shown in cerebrospinal fluid and vitreous following 100% oxygen inhalation. Potential errors due to temperature, fluid flow, and partial volume are discussed. Noninvasive measurements of human body fluid pO2 in vivo are presented, which yield reasonable values based on prior literature estimates. This rapid imaging-based measurement of fluid oxygenation may provide insight into normal physiology as well as changes due to disease or during treatment.

Supplemental Oxygen and Carbon Dioxide Each Increase Subcutaneous and Intestinal Intramural Oxygenation

PubMed Central

Ratnaraj, Jebadurai; Kabon, Barbara; Talcott, Michael R.; Sessler, Daniel I.

2005-01-01

Oxidative killing by neutrophils, a primary defense against surgical pathogens, is directly related to tissue oxygenation. We tested the hypothesis that supplemental inspired oxygen or mild hypercapnia (end-tidal PCO2 of 50 mmHg) improves intestinal oxygenation. Pigs (25±2.5 kg) were used in two studies in random order: 1) Oxygen Study — 30% vs. 100% inspired oxygen concentration at an end-tidal PCO2 of 40 mmHg, and 2) Carbon Dioxide Study — end-tidal PCO2 of 30 mmHg vs. 50 mmHg with 30% oxygen. Within each study, treatment order was randomized. Treatments were maintained for 1.5 hours; measurements were averaged over the final hour. A tonometer inserted in the subcutaneous tissue of the left upper foreleg measured subcutaneous oxygen tension. Tonometers inserted into the intestinal wall measured intestinal intramural oxygen tension from the small and large intestines. 100% oxygen administration doubled subcutaneous oxygen partial pressure (PO2) (57±10 to 107±48 mmHg, P=0.006) and large intestine intramural PO2 (53±14 to 118±72 mmHg, P=0.014); intramural PO2increased 40% in the small intestine (37±10 to 52±25 mmHg, P=0.004). An end-tidal PCO2 of 50 mmHg increased large intestinal PO2 approximately 16% (49±10 to 57±12 mmHg, P=0.039), while intramural PO2 increased by 45% in the small intestine (31±12 to 44±16 mmHg, P=0.002). Supplemental oxygen and mild hypercapnia each increased subcutaneous and intramural tissue PO2, with supplemental oxygen being most effective. PMID:15281531

Coupling between arterial pressure, cerebral blood velocity, and cerebral tissue oxygenation with spontaneous and forced oscillations.

PubMed

Rickards, Caroline A; Sprick, Justin D; Colby, Hannah B; Kay, Victoria L; Tzeng, Yu-Chieh

2015-04-01

We tested the hypothesis that transmission of arterial pressure to brain tissue oxygenation is low under conditions of arterial pressure instability. Two experimental models of hemodynamic instability were used in healthy human volunteers; (1) oscillatory lower body negative pressure (OLBNP) (N = 8; 5 male, 3 female), and; (2) maximal LBNP to presyncope (N = 21; 13 male, 8 female). Mean arterial pressure (MAP), middle cerebral artery velocity (MCAv), and cerebral tissue oxygen saturation (ScO2) were measured non-invasively. For the OLBNP protocol, between 0 and -60 mmHg negative pressure was applied for 20 cycles at 0.05 Hz, then 20 cycles at 0.1 Hz. For the maximal LBNP protocol, progressive 5 min stages of chamber decompression were applied until the onset of presyncope. Spectral power of MAP, mean MCAv, and ScO2 were calculated within the VLF (0.04-0.07 Hz), and LF (0.07-0.2 Hz) ranges, and cross-spectral coherence was calculated for MAP-mean MCAv, MAP-ScO2, and mean MCAv-ScO2 at baseline, during each OLBNP protocol, and at the level prior to pre-syncope during maximal LBNP (sub-max). The key findings are (1) both 0.1 Hz OLBNP and sub-max LBNP elicited increases in LF power for MAP, mean MCAv, and ScO2 (p ≤ 0.08); (2) 0.05 Hz OLBNP increased VLF power in MAP and ScO2 only (p ≤ 0.06); (3) coherence between MAP-mean MCAv was consistently higher (≥0.71) compared with MAP-ScO2, and mean MCAv-ScO2 (≤0.43) during both OLBNP protocols, and sub-max LBNP (p ≤ 0.04). These data indicate high linearity between pressure and cerebral blood flow variations, but reduced linearity between cerebral tissue oxygenation and both arterial pressure and cerebral blood flow. Measuring arterial pressure variability may not always provide adequate information about the downstream effects on cerebral tissue oxygenation, the key end-point of interest for neuronal viability.

The relative influence of hematocrit and red blood cell velocity on oxygen transport from capillaries to tissue

PubMed Central

Lücker, Adrien; Secomb, Timothy W.; Weber, Bruno; Jenny, Patrick

2016-01-01

Objective Oxygen transport to parenchymal cells occurs mainly at the microvascular level, and depends on convective red blood cell (RBC) flux, which is proportional in an individual capillary to the product of capillary hematocrit and red blood cell velocity. This study investigates the relative influence of these two factors on tissue oxygen partial pressure (Po2). Methods A simple analytical model is used to quantify the respective influences of hematocrit, RBC velocity and flow on tissue oxygenation around capillaries. Predicted tissue Po2 levels are compared with a detailed computational model. Results Hematocrit is shown to have a larger influence on tissue Po2 than RBC velocity. The effect of RBC velocity increases with distance from the arterioles. Good agreement between analytical and numerical results is obtained and the discrepancies are explained. Significant dependence of mass transfer coefficients on RBC velocity at low hematocrit is demonstrated. Conclusions For a given RBC flux in a capillary, the Po2 in the surrounding tissue increases with increasing hematocrit, as a consequence of decreasing intravascular resistance to diffusive oxygen transport from RBCs to tissue. These results contribute to understanding the effects of blood flow changes on oxygen transport, such as occur in functional hyperemia in the brain. PMID:27893186

Physiology, intervention, and outcome: three critical questions about cerebral tissue oxygen saturation monitoring.

PubMed

Meng, Lingzhong; Gruenbaum, Shaun E; Dai, Feng; Wang, Tianlong

2018-05-01

The balance between cerebral tissue oxygen consumption and supply can be continuously assessed by cerebral tissue oxygen saturation (SctO2) monitor. A construct consisting of three sequential questions, targeting the physiology monitored, the intervention implemented, and the outcomes affected, is proposed to critically appraise this monitor. The impact of the SctO2-guided care on patient outcome was examined through a systematic literature search and meta-analysis. We concluded that the physiology monitored by SctO2 is robust and dynamic, fragile (prone to derangement), and adversely consequential when deranged. The inter-individual variability of SctO2 measurement advocates for an intervention threshold based on a relative, not absolute, change. The intra-individual variability has multiple determinants which is the foundation of intervention. A variety of therapeutic options are available; however, none are 100% efficacious in treating cerebral dys-oxygenation. The therapeutic efficacy likely depends on both an appropriate differential diagnosis and the functional status of the regulatory mechanisms of cerebral blood flow. Meta-analysis based on five randomized controlled trials suggested a reduced incidence of early postoperative cognitive decline after major surgeries (RR= 0.53; 95% CI: 0.33-0.87; I2 =82%; P=0.01). However, its effects on other neurocognitive outcomes remain unclear. These results need to be interpreted with caution due to the high risks of bias. Quality RCTs based on improved intervention protocols and standardized outcome assessment are warranted in the future.

Three-dimensional spectral-spatial EPR imaging of free radicals in the heart: a technique for imaging tissue metabolism and oxygenation.

PubMed Central

Kuppusamy, P; Chzhan, M; Vij, K; Shteynbuk, M; Lefer, D J; Giannella, E; Zweier, J L

1994-01-01

It has been hypothesized that free radical metabolism and oxygenation in living organs and tissues such as the heart may vary over the spatially defined tissue structure. In an effort to study these spatially defined differences, we have developed electron paramagnetic resonance imaging instrumentation enabling the performance of three-dimensional spectral-spatial images of free radicals infused into the heart and large vessels. Using this instrumentation, high-quality three-dimensional spectral-spatial images of isolated perfused rat hearts and rabbit aortas are obtained. In the isolated aorta, it is shown that spatially and spectrally accurate images of the vessel lumen and wall could be obtained in this living vascular tissue. In the isolated rat heart, imaging experiments were performed to determine the kinetics of radical clearance at different spatial locations within the heart during myocardial ischemia. The kinetic data show the existence of regional and transmural differences in myocardial free radical clearance. It is further demonstrated that EPR imaging can be used to noninvasively measure spatially localized oxygen concentrations in the heart. Thus, the technique of spectral-spatial EPR imaging is shown to be a powerful tool in providing spatial information regarding the free radical distribution, metabolism, and tissue oxygenation in living biological organs and tissues. Images PMID:8159757

Evaluation of Visceral Adipose Tissue Oxygenation by Blood Oxygen Level-Dependent MRI in Zucker Diabetic Fatty Rats.

PubMed

Shi, Hong-Jian; Li, Yan-Feng; Ji, Wen-Jie; Lin, Zhi-Chun; Cai, Wei; Chen, Tao; Yuan, Bin; Niu, Xiu-Long; Li, Han-Ying; Shu, Wen; Li, Yu-Ming; Yuan, Fei; Zhou, Xin; Zhang, Zhuoli

2018-06-01

This study aimed to investigate the feasibility of blood oxygen level-dependent magnetic resonance imaging (BOLD-MRI) to evaluate visceral adipose tissue (VAT) oxygenation in Zucker diabetic fatty (ZDF) rats and its associations with systemic metaflammation. Five-week-old ZDF rats and Zucker lean (ZL) rats were fed a high-fat diet (HFD) for 18 weeks. A baseline BOLD-MRI scan of perirenal adipose tissue was performed after 8 weeks of HFD feeding, and then the rats were randomized to receive pioglitazone or a vehicle for the following 10 weeks. At sacrifice, BOLD-MRI scan, Hypoxyprobe-1 injection, and circulating T helper 17 (Th17), regulatory T (Treg) cells, and monocyte subtype flow cytometry analysis were performed. HFD feeding led to a significant increase in VAT BOLD-MRI R2* signals (20.14 ± 0.23 per second vs. 21.53 ± 0.20 per second; P = 0.012), an indicator for decreased oxygenation. R2* signal was significantly correlated with VAT pimonidazole adduct-positive area, insulin resistance, Th17 and Treg cells, CD43 + and CD43+ + monocyte subtypes, and VAT macrophage infiltration. Pioglitazone treatment improved the insulin resistance and was associated with a delayed progression of VAT oxygenation. This work demonstrated the feasibility of BOLD-MRI for detecting the VAT oxygenation status in ZDF rats, and the BOLD-MRI signals were associated with insulin resistance and systemic metaflammation in ZDF rats during the development of obesity. © 2018 The Obesity Society.

Oxygen consumption of keloids and hypertrophic scars.

PubMed

Ichioka, Shigeru; Ando, Taichi; Shibata, Masahiro; Sekiya, Naomi; Nakatsuka, Takashi

2008-02-01

The oxygen consumption of keloids and hypertrophic scars has never been quantitatively presented, although abnormal metabolic conditions must be associated with their pathophysiology. We invented an original measurement system equipped with a Clark oxygen electrode for ex vivo samples. The measurement of a mouse wound-healing model revealed immature repairing tissues consumed more oxygen than mature tissues. This finding is in accord with the current thinking and supported the validity of our measurement system. The analysis of fresh human samples clearly demonstrated the high oxygen consumption rate of keloid hypertrophic scars and the comparatively low consumption of mature scars. A high oxygen consuming potential, as well as insufficient oxygen diffusion, may possibly contribute to the pathophysiology of keloids and hypertrophic scars.

Changes in muscle tissue oxygenation during stagnant ischemia in septic patients.

PubMed

Pareznik, Roman; Knezevic, Rajko; Voga, Gorazd; Podbregar, Matej

2006-01-01

To determine changes in the rate of thenar muscles tissue deoxygenation during stagnant ischemia in patients with severe sepsis and septic shock. Prospective observational study in the medical ICU of a general hospital. Consecutive patients admitted to ICU with septic shock (n=6), severe sepsis (n=6), localized infection (n=3), and healthy volunteers (n=15). Upper limb ischemia was induced by rapid automatic pneumatic cuff inflation around upper arm. Thenar muscle tissue oxygen saturation (StO2) was measured continuously by near-infrared spectroscopy before and during upper limb ischemia. StO(2) before intervention was comparable in patients with septic shock, severe sepsis, or localized infection and healthy volunteers (89 [65, 92]% vs. 82 [72, 91]% vs. 87 [85, 92]% vs. 83 [79, 93]%, respectively; p>0.1). The rate of StO(2) decrease during stagnant ischemia after initial hemodynamic stabilization was slower in septic shock patients than in those with severe sepsis or localized infection and in controls (-7.0 [-3.6, -11.0] %/min vs. -10.4 [-7.8, -13.3] %/min vs. -19.5 [-12.3, -23.3] vs. -37.4 [-27.3, -56.2] %/min, respectively; p=0.041). At ICU discharge the rate of StO2 decrease did not differ between the septic shock, severe sepsis, and localized infection groups (-17.0 [-9.3, -28.9] %/min vs. -19.9 [-13.3, -23.6] %/min vs. -23.1 [-20.7, -26.2] %/min, respectively), but remained slower than in controls (p<0.01). The rate of StO2 decrease was correlated with Sequential Organ Failure Assessment (SOFA) score (r=0.739, p<0.001). After hemodynamic stabilization thenar muscle tissue oxygen saturation during stagnant ischemia decreases slower in septic shock patients than in patients with severe sepsis or localized infection and in healthy volunteers. During ICU stay and improvement of sepsis the muscle tissue deoxygenation rate increases in survivors of both septic shock and severe sepsis and was correlated with SOFA score.

A Stirred Microchamber for Oxygen Consumption Rate Measurements With Pancreatic Islets

PubMed Central

Papas, Klearchos K.; Pisania, Anna; Wu, Haiyan; Weir, Gordon C.; Colton, Clark K.

2010-01-01

Improvements in pancreatic islet transplantation for treatment of diabetes are hindered by the absence of meaningful islet quality assessment methods. Oxygen consumption rate (OCR) has previously been used to assess the quality of organs and primary tissue for transplantation. In this study, we describe and characterize a stirred microchamber for measuring OCR with small quantities of islets. The device has a titanium body with a chamber volume of about 200 µL and is magnetically stirred and water jacketed for temperature control. Oxygen partial pressure (pO2) is measured by fluorescence quenching with a fiber optic probe, and OCR is determined from the linear decrease of pO2 with time. We demonstrate that measurements can be made rapidly and with high precision. Measurements with βTC3 cells and islets show that OCR is directly proportional to the number of viable cells in mixtures of live and dead cells and correlate linearly with membrane integrity measurements made with cells that have been cultured for 24 h under various stressful conditions. PMID:17497731

Artificial membrane-binding proteins stimulate oxygenation of stem cells during engineering of large cartilage tissue

NASA Astrophysics Data System (ADS)

Armstrong, James P. K.; Shakur, Rameen; Horne, Joseph P.; Dickinson, Sally C.; Armstrong, Craig T.; Lau, Katherine; Kadiwala, Juned; Lowe, Robert; Seddon, Annela; Mann, Stephen; Anderson, J. L. Ross; Perriman, Adam W.; Hollander, Anthony P.

2015-06-01

Restricted oxygen diffusion can result in central cell necrosis in engineered tissue, a problem that is exacerbated when engineering large tissue constructs for clinical application. Here we show that pre-treating human mesenchymal stem cells (hMSCs) with synthetic membrane-active myoglobin-polymer-surfactant complexes can provide a reservoir of oxygen capable of alleviating necrosis at the centre of hyaline cartilage. This is achieved through the development of a new cell functionalization methodology based on polymer-surfactant conjugation, which allows the delivery of functional proteins to the hMSC membrane. This new approach circumvents the need for cell surface engineering using protein chimerization or genetic transfection, and we demonstrate that the surface-modified hMSCs retain their ability to proliferate and to undergo multilineage differentiation. The functionalization technology is facile, versatile and non-disruptive, and in addition to tissue oxygenation, it should have far-reaching application in a host of tissue engineering and cell-based therapies.

Estimating oxygen distribution from vasculature in three-dimensional tumour tissue.

PubMed

Grimes, David Robert; Kannan, Pavitra; Warren, Daniel R; Markelc, Bostjan; Bates, Russell; Muschel, Ruth; Partridge, Mike

2016-03-01

Regions of tissue which are well oxygenated respond better to radiotherapy than hypoxic regions by up to a factor of three. If these volumes could be accurately estimated, then it might be possible to selectively boost dose to radio-resistant regions, a concept known as dose-painting. While imaging modalities such as 18F-fluoromisonidazole positron emission tomography (PET) allow identification of hypoxic regions, they are intrinsically limited by the physics of such systems to the millimetre domain, whereas tumour oxygenation is known to vary over a micrometre scale. Mathematical modelling of microscopic tumour oxygen distribution therefore has the potential to complement and enhance macroscopic information derived from PET. In this work, we develop a general method of estimating oxygen distribution in three dimensions from a source vessel map. The method is applied analytically to line sources and quasi-linear idealized line source maps, and also applied to full three-dimensional vessel distributions through a kernel method and compared with oxygen distribution in tumour sections. The model outlined is flexible and stable, and can readily be applied to estimating likely microscopic oxygen distribution from any source geometry. We also investigate the problem of reconstructing three-dimensional oxygen maps from histological and confocal two-dimensional sections, concluding that two-dimensional histological sections are generally inadequate representations of the three-dimensional oxygen distribution. © 2016 The Authors.

Estimating oxygen distribution from vasculature in three-dimensional tumour tissue

PubMed Central

Kannan, Pavitra; Warren, Daniel R.; Markelc, Bostjan; Bates, Russell; Muschel, Ruth; Partridge, Mike

2016-01-01

Regions of tissue which are well oxygenated respond better to radiotherapy than hypoxic regions by up to a factor of three. If these volumes could be accurately estimated, then it might be possible to selectively boost dose to radio-resistant regions, a concept known as dose-painting. While imaging modalities such as 18F-fluoromisonidazole positron emission tomography (PET) allow identification of hypoxic regions, they are intrinsically limited by the physics of such systems to the millimetre domain, whereas tumour oxygenation is known to vary over a micrometre scale. Mathematical modelling of microscopic tumour oxygen distribution therefore has the potential to complement and enhance macroscopic information derived from PET. In this work, we develop a general method of estimating oxygen distribution in three dimensions from a source vessel map. The method is applied analytically to line sources and quasi-linear idealized line source maps, and also applied to full three-dimensional vessel distributions through a kernel method and compared with oxygen distribution in tumour sections. The model outlined is flexible and stable, and can readily be applied to estimating likely microscopic oxygen distribution from any source geometry. We also investigate the problem of reconstructing three-dimensional oxygen maps from histological and confocal two-dimensional sections, concluding that two-dimensional histological sections are generally inadequate representations of the three-dimensional oxygen distribution. PMID:26935806

In vivo imaging and analysis of cerebrovascular hemodynamic responses and tissue oxygenation in the mouse brain.

PubMed

Kisler, Kassandra; Lazic, Divna; Sweeney, Melanie D; Plunkett, Shane; El Khatib, Mirna; Vinogradov, Sergei A; Boas, David A; Sakadži, Sava; Zlokovic, Berislav V

2018-06-01

Cerebrovascular dysfunction has an important role in the pathogenesis of multiple brain disorders. Measurement of hemodynamic responses in vivo can be challenging, particularly as techniques are often not described in sufficient detail and vary between laboratories. We present a set of standardized in vivo protocols that describe high-resolution two-photon microscopy and intrinsic optical signal (IOS) imaging to evaluate capillary and arteriolar responses to a stimulus, regional hemodynamic responses, and oxygen delivery to the brain. The protocol also describes how to measure intrinsic NADH fluorescence to understand how blood O 2 supply meets the metabolic demands of activated brain tissue, and to perform resting-state absolute oxygen partial pressure (pO 2 ) measurements of brain tissue. These methods can detect cerebrovascular changes at far higher resolution than MRI techniques, although the optical nature of these techniques limits their achievable imaging depths. Each individual procedure requires 1-2 h to complete, with two to three procedures typically performed per animal at a time. These protocols are broadly applicable in studies of cerebrovascular function in healthy and diseased brain in any of the existing mouse models of neurological and vascular disorders. All these procedures can be accomplished by a competent graduate student or experienced technician, except the two-photon measurement of absolute pO 2 level, which is better suited to a more experienced, postdoctoral-level researcher.

The relative influence of hematocrit and red blood cell velocity on oxygen transport from capillaries to tissue.

PubMed

Lücker, Adrien; Secomb, Timothy W; Weber, Bruno; Jenny, Patrick

2017-04-01

Oxygen transport to parenchymal cells occurs mainly at the microvascular level and depends on convective RBC flux, which is proportional in an individual capillary to the product of capillary hematocrit and RBC velocity. This study investigates the relative influence of these two factors on tissue PO 2 . A simple analytical model is used to quantify the respective influences of hematocrit, RBC velocity, and RBC flow on tissue oxygenation around capillaries. Predicted tissue PO 2 levels are compared with a detailed computational model. Hematocrit is shown to have a larger influence on tissue PO 2 than RBC velocity. The effect of RBC velocity increases with distance from the arterioles. Good agreement between analytical and numerical results is obtained, and the discrepancies are explained. Significant dependence of MTCs on RBC velocity at low hematocrit is demonstrated. For a given RBC flux in a capillary, the PO 2 in the surrounding tissue increases with increasing hematocrit, as a consequence of decreasing IVR to diffusive oxygen transport from RBCs to tissue. These results contribute to understanding the effects of blood flow changes on oxygen transport, such as those that occur in functional hyperemia in the brain. © 2016 John Wiley & Sons Ltd.

[Specialties of singlet oxygen and ozone inhalations action on lipoperozydation and antioxidant system of rats blood and tissues].

PubMed

Martusevich, A A; Martusevich, A K; Peretiagin, S P

2013-09-01

The aim of this work was the analysis of singlet oxygen and the ozone effect on lipid peroxidation and antioxidant activity of rat organs and blood. Wistar rats were randomly divided into five groups: control group (without any manipulations; n = 10) and four main groups (n = 10 in each group) with inhalations by dry, moisture and oil-processed ozone-oxygen mixture (ozone concentration 60 micro g/l) or singlet oxygen, respectively. Activity of pro- and antioxidant systems was estimated in blood and tissues (lungs, heart, liver and kidney) by inducing biochemiluminescence. Singlet oxygen was shown to exert the "mildest" effect with stimulation of blood antioxidant potential and saving tissue oxidative potential without hyperactivation of lipid peroxidation. Use of moistened ozone-oxygen mixture caused moderate stimulating action on antioxidant re serves of blood and tissues. Dry ozone-oxygen mixture clearly decreased lipid peroxidation intensity.

Numerical simulation and analysis of accurate blood oxygenation measurement by using optical resolution photoacoustic microscopy

NASA Astrophysics Data System (ADS)

Yu, Tianhao; Li, Qian; Li, Lin; Zhou, Chuanqing

2016-10-01

Accuracy of photoacoustic signal is the crux on measurement of oxygen saturation in functional photoacoustic imaging, which is influenced by factors such as defocus of laser beam, curve shape of large vessels and nonlinear saturation effect of optical absorption in biological tissues. We apply Monte Carlo model to simulate energy deposition in tissues and obtain photoacoustic signals reaching a simulated focused surface detector to investigate corresponding influence of these factors. We also apply compensation on photoacoustic imaging of in vivo cat cerebral cortex blood vessels, in which signals from different lateral positions of vessels are corrected based on simulation results. And this process on photoacoustic images can improve the smoothness and accuracy of oxygen saturation results.

Optimization measurement of muscle oxygen saturation under isometric studies using FNIRS

NASA Astrophysics Data System (ADS)

Halim, A. A. A.; Laili, M. H.; Salikin, M. S.; Rusop, M.

2018-05-01

Development of functional near infrared spectroscopy (fNIRS) technologies has advanced quantification signal using multiple wavelength and detector to investigate hemodynamic response in human muscle. These non-invasive technologies have been widely used to solve the propagation of light inside the tissues including the absorption, scattering coefficient and to quantify the oxygenation level of haemoglobin and myoglobin in human muscle. The goal of this paper is to optimize the measurement of muscle oxygen saturation during isometric exercise using functional near infrared spectroscopy (fNIRS). The experiment was carried out on 15 sedentary healthy male volunteers. All volunteers are required to perform an isometric exercise at three assessment of muscular fatigue's level on flexor digitalis (FDS) muscle in the human forearm using fNIRS. The slopes of the signals have been highlighted to evaluate the muscle oxygen saturation of regional muscle fatigue. As a result, oxygen saturation slope from 10% exercise showed steeper than the first assessment at 30%-50% of fatigues level. The hemodynamic signal response showed significant value (p=0.04) at all three assessment of muscular fatigue's level which produce a p-value (p<0.05) measured by fNIRS. Thus, this highlighted parameter could be used to estimate fatigue's level of human and could open other possibilities to study muscle performance diagnosis.

Nanoparticle-enhanced spectral photoacoustic tomography: effect of oxygen saturation and tissue heterogeneity

NASA Astrophysics Data System (ADS)

Vogt, William C.; Jia, Congxian; Wear, Keith A.; Garra, Brian S.; Pfefer, T. Joshua

2016-03-01

Molecular imaging for breast cancer detection, infectious disease diagnostics and preclinical animal research may be achievable through combined use of targeted exogenous agents - such as nanoparticles - and spectral Photoacoustic Tomography (PAT). However, tissue heterogeneity can alter fluence distributions and acoustic propagation, corrupting measured PAT absorption spectra and complicating in vivo nanoparticle detection and quantitation. Highly absorptive vascular structures represent a common confounding factor, and variations in vessel hemoglobin saturation (SO2) may alter spectral content of signals from adjacent/deeper regions. To evaluate the impact of this effect on PAT nanoparticle detectability, we constructed heterogeneous phantoms with well-characterized channel-inclusion geometries and biologically relevant optical and acoustic properties. Phantoms contained an array of tubes at several depths filled with hemoglobin solutions doped with varying concentrations of gold nanorods with an absorption peak at 780 nm. Both overlying and target network SO2 was tuned using sodium dithionite. Phantoms were imaged from 700 to 900 nm using a custom PAT system comprised of a tunable pulsed laser and a research-grade ultrasound system. Recovered nanoparticle spectra were analyzed and compared with results from both spectrophotometry and PAT data from waterimmersed tubes containing blood and nanoparticle solutions. Results suggested that nanoparticle selection for a given PAT application should take into account expected oxygenation states of both target blood vessel and background tissue oxygenation to achieve optimal performance.

Oxygen matters: tissue culture oxygen levels affect mitochondrial function and structure as well as responses to HIV viroproteins.

PubMed

Tiede, L M; Cook, E A; Morsey, B; Fox, H S

2011-12-22

Mitochondrial dysfunction is implicated in a majority of neurodegenerative disorders and much study of neurodegenerative disease is done on cultured neurons. In traditional tissue culture, the oxygen level that cells experience is dramatically higher (21%) than in vivo conditions (1-11%). These differences can alter experimental results, especially, pertaining to mitochondria and oxidative metabolism. Our results show that primary neurons cultured at physiological oxygen levels found in the brain showed higher polarization, lower rates of ROS production, larger mitochondrial networks, greater cytoplasmic fractions of mitochondria and larger mitochondrial perimeters than those cultured at higher oxygen levels. Although neurons cultured in either physiological oxygen or atmospheric oxygen exhibit significant increases in mitochondrial reactive oxygen species (ROS) production when treated with the human immunodeficiency virus (HIV) virotoxin trans-activator of transcription, mitochondria of neurons cultured at physiological oxygen underwent depolarization with dramatically increased cell death, whereas those cultured at atmospheric oxygen became hyperpolarized with no increase in cell death. Studies with a second HIV virotoxin, negative regulation factor (Nef), revealed that Nef treatment also increased mitochondrial ROS production for both the oxygen conditions, but resulted in mitochondrial depolarization and increased death only in neurons cultured in physiological oxygen. These results indicate a role for oxidative metabolism in a mechanism of neurotoxicity during HIV infection and demonstrate the importance of choosing the correct, physiological, culture oxygen in mitochondrial studies performed in neurons.

Dynamic model for the tissue concentration and oxygen saturation of hemoglobin in relation to blood volume, flow velocity, and oxygen consumption: Implications for functional neuroimaging and coherent hemodynamics spectroscopy (CHS)

PubMed Central

Fantini, Sergio

2013-01-01

This article presents a dynamic model that quantifies the temporal evolution of the concentration and oxygen saturation of hemoglobin in tissue, as determined by time-varying hemodynamic and metabolic parameters: blood volume, flow velocity, and oxygen consumption. This multi-compartment model determines separate contributions from arterioles, capillaries, and venules that comprise the tissue microvasculature, and treats them as a complete network, without making assumptions on the details of the architecture and morphology of the microvascular bed. A key parameter in the model is the effective blood transit time through the capillaries and its associated probability of oxygen release from hemoglobin to tissue, as described by a rate constant for oxygen diffusion. The solution of the model in the time domain predicts the signals measured by hemodynamic-based neuroimaging techniques such as functional near-infrared spectroscopy (fNIRS) and functional magnetic resonance imaging (fMRI) in response to brain activation. In the frequency domain, the model yields an analytical solution based on a phasor representation that provides a framework for quantitative spectroscopy of coherent hemodynamic oscillations. I term this novel technique coherent hemodynamics spectroscopy (CHS), and this article describes how it can be used for the assessment of cerebral autoregulation and the study of hemodynamic oscillations resulting from a variety of periodic physiological challenges, brain activation protocols, or physical maneuvers. PMID:23583744

Dynamic model for the tissue concentration and oxygen saturation of hemoglobin in relation to blood volume, flow velocity, and oxygen consumption: Implications for functional neuroimaging and coherent hemodynamics spectroscopy (CHS).

PubMed

Fantini, Sergio

2014-01-15

This article presents a dynamic model that quantifies the temporal evolution of the concentration and oxygen saturation of hemoglobin in tissue, as determined by time-varying hemodynamic and metabolic parameters: blood volume, flow velocity, and oxygen consumption. This multi-compartment model determines separate contributions from arterioles, capillaries, and venules that comprise the tissue microvasculature, and treats them as a complete network, without making assumptions on the details of the architecture and morphology of the microvascular bed. A key parameter in the model is the effective blood transit time through the capillaries and its associated probability of oxygen release from hemoglobin to tissue, as described by a rate constant for oxygen diffusion. The solution of the model in the time domain predicts the signals measured by hemodynamic-based neuroimaging techniques such as functional near-infrared spectroscopy (fNIRS) and functional magnetic resonance imaging (fMRI) in response to brain activation. In the frequency domain, the model yields an analytical solution based on a phasor representation that provides a framework for quantitative spectroscopy of coherent hemodynamic oscillations. I term this novel technique coherent hemodynamics spectroscopy (CHS), and this article describes how it can be used for the assessment of cerebral autoregulation and the study of hemodynamic oscillations resulting from a variety of periodic physiological challenges, brain activation protocols, or physical maneuvers. Copyright © 2013 Elsevier Inc. All rights reserved.

Significance of Brain Tissue Oxygenation and the Arachidonic Acid Cascade in Stroke

PubMed Central

Rink, Cameron

2011-01-01

Abstract The significance of the hypoxia component of stroke injury is highlighted by hypermetabolic brain tissue enriched with arachidonic acid (AA), a 22:6n-3 polyunsaturated fatty acid. In an ischemic stroke environment in which cerebral blood flow is arrested, oxygen-starved brain tissue initiates the rapid cleavage of AA from the membrane phospholipid bilayer. Once free, AA undergoes both enzyme-independent and enzyme-mediated oxidative metabolism, resulting in the formation of number of biologically active metabolites which themselves contribute to pathological stroke outcomes. This review is intended to examine two divergent roles of molecular dioxygen in brain tissue as (1) a substrate for life-sustaining homeostatic metabolism of glucose and (2) a substrate for pathogenic metabolism of AA under conditions of stroke. Recent developments in research concerning supplemental oxygen therapy as an intervention to correct the hypoxic component of stroke injury are discussed. Antioxid. Redox Signal. 14, 1889–1903. PMID:20673202

A unique mode of tissue oxygenation and the adaptive radiation of teleost fishes.

PubMed

Randall, D J; Rummer, J L; Wilson, J M; Wang, S; Brauner, C J

2014-04-15

Teleost fishes constitute 95% of extant aquatic vertebrates, and we suggest that this is related in part to their unique mode of tissue oxygenation. We propose the following sequence of events in the evolution of their oxygen delivery system. First, loss of plasma-accessible carbonic anhydrase (CA) in the gill and venous circulations slowed the Jacobs-Stewart cycle and the transfer of acid between the plasma and the red blood cells (RBCs). This ameliorated the effects of a generalised acidosis (associated with an increased capacity for burst swimming) on haemoglobin (Hb)-O2 binding. Because RBC pH was uncoupled from plasma pH, the importance of Hb as a buffer was reduced. The decrease in buffering was mediated by a reduction in the number of histidine residues on the Hb molecule and resulted in enhanced coupling of O2 and CO2 transfer through the RBCs. In the absence of plasma CA, nearly all plasma bicarbonate ultimately dehydrated to CO2 occurred via the RBCs, and chloride/bicarbonate exchange was the rate-limiting step in CO2 excretion. This pattern of CO2 excretion across the gills resulted in disequilibrium states for CO2 hydration/dehydration reactions and thus elevated arterial and venous plasma bicarbonate levels. Plasma-accessible CA embedded in arterial endothelia was retained, which eliminated the localized bicarbonate disequilibrium forming CO2 that then moved into the RBCs. Consequently, RBC pH decreased which, in conjunction with pH-sensitive Bohr/Root Hbs, elevated arterial oxygen tensions and thus enhanced tissue oxygenation. Counter-current arrangement of capillaries (retia) at the eye and later the swim bladder evolved along with the gas gland at the swim bladder. Both arrangements enhanced and magnified CO2 and acid production and, therefore, oxygen secretion to those specialised tissues. The evolution of β-adrenergically stimulated RBC Na(+)/H(+) exchange protected gill O2 uptake during stress and further augmented plasma disequilibrium states

Transcutaneous oxygen tension monitoring in critically ill patients receiving packed red blood cells.

PubMed

Schlager, Oliver; Gschwandtner, Michael E; Willfort-Ehringer, Andrea; Kurz, Martin; Mueller, Markus; Koppensteiner, Renate; Heinz, Gottfried

2014-12-01

Whether transfusions of packed red blood cells (PRBCs) affect tissue oxygenation in stable critically ill patients is still matter of discussion. The microvascular capacity for tissue oxygenation can be determined noninvasively by measuring transcutaneous oxygen tension (tcpO2). The aim of this study was to assess tissue oxygenation by measuring tcpO2 in stable critically ill patients receiving PRBC transfusions. Nineteen stable critically ill patients, who received 2 units of PRBC, were prospectively included into this pilot study. Transcutaneous oxygen tension was measured continuously during PRBC transfusions using Clark's electrodes. In addition, whole blood viscosity and global hemodynamics were determined. Reliable measurement signals during continuous tcpO2 monitoring were observed in 17 of 19 included patients. Transcutaneous oxygen tension was related to the global oxygen consumption (r=-0.78; P=.003), the arterio-venous oxygen content difference (r=-0.65; P=.005), and the extraction rate (r=-0.71; P=.02). The transfusion-induced increase of the hemoglobin concentration was paralleled by an increase of the whole blood viscosity (P<.001). Microvascular tissue oxygenation by means of tcpO2 was not affected by PRBC transfusions (P=.46). Packed red blood cell transfusions resulted in an increase of global oxygen delivery (P=.02) and central venous oxygen saturation (P=.01), whereas oxygen consumption remained unchanged (P=.72). In stable critically ill patients, microvascular tissue oxygenation can be continuously monitored by Clark's tcpO2 electrodes. According to continuous tcpO2 measurements, the microvascular tissue oxygenation is not affected by PRBC transfusions. Copyright © 2014 Elsevier Inc. All rights reserved.

Biological tissue component evaluation by measuring photoacoustic spectrum

NASA Astrophysics Data System (ADS)

Namita, Takeshi; Murata, Yuya; Tokuyama, Junji; Kondo, Kengo; Yamakawa, Makoto; Shiina, Tsuyoshi

2017-03-01

Photoacoustic imaging has garnered constant attention as a non-invasive modality for visualizing details of the neovascularization structure of tumors, or the distribution of oxygen saturation, which is related to the tumor grade. However, photoacoustic imaging is applicable not only for vascular imaging but also for diagnosing properties of various tissues such as skin or muscle diseases, fat related to arteriosclerosis or fatty liver, cartilage related to arthritis, and fibrous tissues related to hepatitis. The photoacoustic signal intensity is wavelength-dependent and proportional to the absorption coefficient and thermal acoustic conversion efficiency (i.e. Grüneisen parameter) of the target biological tissue. To ascertain the appropriate wavelength range for biological tissue imaging and to evaluate tissue properties, photoacoustic spectra of various tissues (e.g., skin, muscle, and adipose tissue) were measured using a hydrophone (9 mm diameter) at 680-1600 nm wavelengths. Results confirmed that respective tissues have unique photoacoustic spectra. However, almost all samples have peaks around 1200 nm and 1400-1500 nm for wavelengths where the light absorbance of lipid or water is high. The main components of biological tissues are water, protein, and lipid. Results confirmed that photoacoustic spectra reflect the tissue components well. To evaluate the feasibility of the tissue characterization using photoacoustic methods, the photoacoustic signal intensity ratio between two wavelength regions was calculated as described above. Signal intensity ratios agreed well with the composition ratio between water and lipid in samples. These analyses verified the feasibility of evaluating tissue properties using photoacoustic methods.

Adipose tissue oxygenation is associated with insulin sensitivity independently of adiposity in obese men and women.

PubMed

Goossens, Gijs H; Vogel, Max A A; Vink, Roel G; Mariman, Edwin C; van Baak, Marleen A; Blaak, Ellen E

2018-04-23

Adipose tissue (AT) dysfunction contributes to the pathophysiology of insulin resistance and type 2 diabetes. Previous studies have shown that altered AT oxygenation affects adipocyte functionality, but it remains to be elucidated whether altered AT oxygenation is more strongly related to obesity or insulin sensitivity. In the present study, we tested the hypothesis that AT oxygenation is associated with insulin sensitivity rather than adiposity in humans. Thirty-five lean and obese individuals (21 men and 14 women, aged 40-65 years) with either normal or impaired glucose metabolism participated in a cross-sectional single-centre study. We measured abdominal subcutaneous AT oxygenation, body composition and insulin sensitivity. AT oxygenation was higher in obese insulin resistant as compared to obese insulin sensitive (IS) individuals with similar age, body mass index and body fat percentage, both in men and women. No significant differences in AT oxygenation were found between obese IS and lean IS men. Moreover, AT oxygenation was positively associated with insulin resistance (r = 0.465; P = .005), even after adjustment for age, sex and body fat percentage (standardized β = 0.479; P = .005). In conclusion, abdominal subcutaneous AT oxygenation is associated with insulin sensitivity both in men and women, independently of adiposity. AT oxygenation may therefore be a promising target to improve insulin sensitivity. © 2018 John Wiley & Sons Ltd.

Effect of hypobaric air, oxygen, heliox (50:50), or heliox (80:20) breathing on air bubbles in adipose tissue.

PubMed

Hyldegaard, O; Madsen, J

2007-09-01

The fate of bubbles formed in tissues during decompression to altitude after diving or due to accidental loss of cabin pressure during flight has only been indirectly inferred from theoretical modeling and clinical observations with noninvasive bubble-measuring techniques of intravascular bubbles. In this report we visually followed the in vivo resolution of micro-air bubbles injected into adipose tissue of anesthetized rats decompressed from 101.3 kPa to and held at 71 kPa corresponding to approximately 2.750 m above sea level, while the rats breathed air, oxygen, heliox (50:50), or heliox (80:20). During air breathing, bubbles initially grew for 30-80 min, after which they remained stable or began to shrink slowly. Oxygen breathing caused an initial growth of all bubbles for 15-85 min, after which they shrank until they disappeared from view. Bubble growth was significantly greater during breathing of oxygen compared with air and heliox breathing mixtures. During heliox (50:50) breathing, bubbles initially grew for 5-30 min, from which point they shrank until they disappeared from view. After a shift to heliox (80:20) breathing, some bubbles grew slightly for 20-30 min, then shrank until they disappeared from view. Bubble disappearance was significantly faster during breathing of oxygen and heliox mixtures compared with air. In conclusion, the present results show that oxygen breathing at 71 kPa promotes bubble growth in lipid tissue, and it is possible that breathing of heliox may be beneficial in treating decompression sickness during flight.

Simulation of oxygen saturation measurement in a single blood vein.

PubMed

Duadi, Hamootal; Nitzan, Meir; Fixler, Dror

2016-09-15

The value of oxygen saturation in venous blood, SvO₂, has important clinical significance since it is related to the tissue oxygen utilization, which is related to the blood flow to the tissue and to its metabolism rate. However, existing pulse oximetry techniques are not suitable for blood in veins. In the current study we examine the feasibility of difference oximetry to assess SvO₂ by using two near-infrared wavelengths and collecting the backscattered light from two photodetectors located at different distances from the light source.

Oxygen matters: tissue culture oxygen levels affect mitochondrial function and structure as well as responses to HIV viroproteins

PubMed Central

Tiede, L M; Cook, E A; Morsey, B; Fox, H S

2011-01-01

Mitochondrial dysfunction is implicated in a majority of neurodegenerative disorders and much study of neurodegenerative disease is done on cultured neurons. In traditional tissue culture, the oxygen level that cells experience is dramatically higher (21%) than in vivo conditions (1–11%). These differences can alter experimental results, especially, pertaining to mitochondria and oxidative metabolism. Our results show that primary neurons cultured at physiological oxygen levels found in the brain showed higher polarization, lower rates of ROS production, larger mitochondrial networks, greater cytoplasmic fractions of mitochondria and larger mitochondrial perimeters than those cultured at higher oxygen levels. Although neurons cultured in either physiological oxygen or atmospheric oxygen exhibit significant increases in mitochondrial reactive oxygen species (ROS) production when treated with the human immunodeficiency virus (HIV) virotoxin trans-activator of transcription, mitochondria of neurons cultured at physiological oxygen underwent depolarization with dramatically increased cell death, whereas those cultured at atmospheric oxygen became hyperpolarized with no increase in cell death. Studies with a second HIV virotoxin, negative regulation factor (Nef), revealed that Nef treatment also increased mitochondrial ROS production for both the oxygen conditions, but resulted in mitochondrial depolarization and increased death only in neurons cultured in physiological oxygen. These results indicate a role for oxidative metabolism in a mechanism of neurotoxicity during HIV infection and demonstrate the importance of choosing the correct, physiological, culture oxygen in mitochondrial studies performed in neurons. PMID:22190005

Quantitative real-time optical imaging of the tissue metabolic rate of oxygen consumption

NASA Astrophysics Data System (ADS)

Ghijsen, Michael; Lentsch, Griffin R.; Gioux, Sylvain; Brenner, Matthew; Durkin, Anthony J.; Choi, Bernard; Tromberg, Bruce J.

2018-03-01

The tissue metabolic rate of oxygen consumption (tMRO2) is a clinically relevant marker for a number of pathologies including cancer and arterial occlusive disease. We present and validate a noncontact method for quantitatively mapping tMRO2 over a wide, scalable field of view at 16 frames / s. We achieve this by developing a dual-wavelength, near-infrared coherent spatial frequency-domain imaging (cSFDI) system to calculate tissue optical properties (i.e., absorption, μa, and reduced scattering, μs‧, parameters) as well as the speckle flow index (SFI) at every pixel. Images of tissue oxy- and deoxyhemoglobin concentration ( [ HbO2 ] and [HHb]) are calculated from optical properties and combined with SFI to calculate tMRO2. We validate the system using a series of yeast-hemoglobin tissue-simulating phantoms and conduct in vivo tests in humans using arterial occlusions that demonstrate sensitivity to tissue metabolic oxygen debt and its repayment. Finally, we image the impact of cyanide exposure and toxicity reversal in an in vivo rabbit model showing clear instances of mitochondrial uncoupling and significantly diminished tMRO2. We conclude that dual-wavelength cSFDI provides rapid, quantitative, wide-field mapping of tMRO2 that can reveal unique spatial and temporal dynamics relevant to tissue pathology and viability.

The new Licox combined brain tissue oxygen and brain temperature monitor: assessment of in vitro accuracy and clinical experience in severe traumatic brain injury.

PubMed

Stewart, Campbell; Haitsma, Iain; Zador, Zsolt; Hemphill, J Claude; Morabito, Diane; Manley, Geoffrey; Rosenthal, Guy

2008-12-01

Monitoring of brain tissue oxygen tension is increasingly being used to monitor patients after severe traumatic brain injury and to guide therapies aimed at maintaining brain tissue oxygen tension above threshold levels. The new Licox PMO combined oxygen and temperature catheter (Integra LifeSciences, Plainsboro, NJ) combines measurements of oxygen tension and temperature in a single probe inserted through a bolt mechanism. In this study, we sought to evaluate the accuracy of the new Licox PMO probe under controlled laboratory conditions and to assess the accuracy of oxygen tension and temperature measurements and the new automated card calibration system. We also describe our clinical experience with the Licox PMO probe. Oxygen tension was measured in a 2-chambered apparatus at different oxygen tensions and temperatures. The new card calibration system was compared with a manually calibrated system. Rates of hematoma, infection, and dislodgement in our clinical experience were recorded. The new Licox PMO probe accurately measures oxygen tension over a wide range of oxygen concentrations and physiological temperatures, but it does have a small tendency to underestimate oxygen tension (mean error, -3.8 +/- 3.5%) that is more pronounced between the temperatures of 33 and 39 degrees C. The thermistor of the PMO probe also has a tendency to underestimate temperature when compared with a resistance thermometer (mean error, -0.67 +/- 0.22 degrees C). The card calibration system was also found to introduce some variability in measurements of oxygen tension when compared with a manually calibrated system. Clinical experience with the new probe indicates good placement within the white matter using the improved bolt system and low rates of hematoma (2.9%), infection (0%), and dislodgement (5.9%). The new Licox PMO probe is accurate but has a small, consistent tendency to under-read oxygen tension that is more pronounced at higher temperatures. The probe tends to under

Measurement of Reactive Oxygen Species, Reactive Nitrogen Species, and Redox-Dependent Signaling in the Cardiovascular System

PubMed Central

Griendling, Kathy K.; Touyz, Rhian M.; Zweier, Jay L.; Dikalov, Sergey; Chilian, William; Chen, Yeong-Renn; Harrison, David G.; Bhatnagar, Aruni

2017-01-01

Reactive oxygen species and reactive nitrogen species are biological molecules that play important roles in cardiovascular physiology and contribute to disease initiation, progression, and severity. Because of their ephemeral nature and rapid reactivity, these species are difficult to measure directly with high accuracy and precision. In this statement, we review current methods for measuring these species and the secondary products they generate and suggest approaches for measuring redox status, oxidative stress, and the production of individual reactive oxygen and nitrogen species. We discuss the strengths and limitations of different methods and the relative specificity and suitability of these methods for measuring the concentrations of reactive oxygen and reactive nitrogen species in cells, tissues, and biological fluids. We provide specific guidelines, through expert opinion, for choosing reliable and reproducible assays for different experimental and clinical situations. These guidelines are intended to help investigators and clinical researchers avoid experimental error and ensure high-quality measurements of these important biological species. PMID:27418630

Impaired Tissue Oxygenation in Metabolic Syndrome Requires Increased Microvascular Perfusion Heterogeneity

PubMed Central

McClatchey, P. Mason; Wu, Fan; Olfert, I. Mark; Ellis, Christopher G.; Goldman, Daniel; Reusch, Jane E. B.

2018-01-01

Metabolic syndrome (MS) in obese Zucker rats (OZR) is associated with impaired skeletal muscle performance and blunted hyperemia. Studies suggest that reduced O2 diffusion capacity is required to explain compromised muscle performance and that heterogeneous microvascular perfusion distribution is critical. We modeled tissue oxygenation during muscle contraction in control and OZR skeletal muscle using physiologically realistic relationships. Using a network model of Krogh cylinders with increasing perfusion asymmetry and increased plasma skimming, we predict increased perfusion heterogeneity and decreased muscle oxygenation in OZR, with partial recovery following therapy. Notably, increasing O2 delivery had less impact on VO2 than equivalent decreases in O2 delivery, providing a mechanism for previous empirical work associating perfusion heterogeneity and impaired O2 extraction. We demonstrate that increased skeletal muscle perfusion asymmetry is a defining characteristic of MS and must be considered to effectively model and understand blood-tissue O2 exchange in this model of human disease. PMID:28168652

Effect of supplemental oxygen versus dobutamine administration on liver oxygen tension in dPP-guided normovolemic pigs.

PubMed

Pestel, G; Fukui, K; Hager, H; Kurz, A; Hiltebrand, L

2009-01-01

Difference in pulse pressure (dPP) confirms adequate intravascular filling as a prerequisite for tissue perfusion. We hypothesized that both oxygen and dobutamine increase liver tissue oxygen tension (ptO(2)). Eight anesthetized pigs received dPP-guided fluid management. Hepatic pO(2) was measured with Clark-type electrodes placed subcapsularly, and on the liver surface. Pigs received: (1) supplemental oxygen (F(i)O(2) 1.0); (2) dobutamine 2.5 microg/kg/min, and (3) dobutamine 5 microg/kg/min. Data were analyzed using repeated-measures ANOVA followed by a Tukey post-test for multiple comparisons. ptO(2 )measured subcapsularly and at the liver surface were compared using the Bland-Altman plot. Variation in F(i)O(2) changed local hepatic tissue ptO(2) [subcapsular measurement: 39 +/- 12 (F(i)O(2) 0.3), 89 +/- 35 mm Hg (F(i)O(2) 1.0, p = 0.01 vs. F(i)O(2) 0.3), 44 +/- 10 mm Hg (F(i)O(2) 0.3, p = 0.05 vs. F(i)O(2) 1.0); surface measurement: 52 +/- 35 (F(i)O(2) 0.3), 112 +/- 24 mm Hg (F(i)O(2) 1.0, p = 0.001 vs. F(i)O(2) 0.3), 54 +/- 24 mm Hg (F(i)O(2) 0.3, p = 0.001 vs. F(i)O(2) 1.0)]. Surface measurements were widely scattered compared to subcapsular measurements (bias: -15 mm Hg, precision: 76.3 mm Hg). Dobutamine did not affect hepatic oxygenation. Supplemental oxygen increased hepatic tissue pO(2) while dobutamine did not. Although less invasive, the use of surface measurements is discouraged. Copyright 2009 S. Karger AG, Basel.

Long-term exposure to repetitive hyperbaric oxygen results in cumulative oxidative stress in rat lung tissue.

PubMed

Simsek, Kemal; Ay, Hakan; Topal, Turgut; Ozler, Mehmet; Uysal, Bulent; Ucar, Ergun; Acikel, Cengiz H; Yesilyurt, Ozgur; Korkmaz, Ahmet; Oter, Sukru; Yildiz, Senol

2011-02-01

Despite its known benefits, hyperbaric oxygen (HBO) is also reported to enhance the production of reactive oxygen species and can cause oxidative stress in several tissues. Previous studies had shown that HBO-induced oxidative stress is directly proportional to both its exposure pressure and duration. Nevertheless, these studies were usually performed with single-session HBO exposure but its clinical use commonly depends on long-term exposure periods. To clarify the oxidative effect of long-term repetitive HBO in the lung tissue of rats. Male Sprague-Dawley rats were divided into six study groups exposed to consecutive HBO sessions (2.8 atm/90  min) for 5, 10, 15, 20, 30, and 40 days. Animals were sacrificed 24  h after the last HBO session. An additional control group was set to obtain normal data. Lung malondialdehyde (MDA) and carbonylated protein (PCC) levels were determined as measures of oxidative stress along with the activities of the antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase. None of the measured parameters showed any changes among the groups exposed to 5-15 HBO sessions. However, MDA, PCC, and SOD were found to be significantly increased in the 20 to 40 session groups. These results indicate that repetitive treatment with HBO may cause oxidative stress in critical tissues including the lung. Although HBO-mediated free radicals are accepted to be responsible for the benefits of this therapeutic modality, especially in cases with prolonged exposure, possible injurious effects of supranormal values of bio-oxidative products need to be considered.

In vivo EPR oximetry using an isotopically-substituted nitroxide: Potential for quantitative measurement of tissue oxygen

PubMed Central

Weaver, John; Burks, Scott R.; Liu, Ke Jian; Kao, Joseph P.Y.; Rosen, Gerald M.

2017-01-01

Variations in brain oxygen (O2) concentration can have profound effects on brain physiology. Thus, the ability to quantitate local O2 concentrations noninvasively in vivo could significantly enhance understanding of several brain pathologies. However, quantitative O2 mapping in the brain has proven difficult. The electron paramagnetic resonance (EPR) spectra of nitroxides are sensitive to molecular O2 and can be used to estimate O2 concentrations in aqueous media. We recently synthesized labile-ester-containing nitroxides, such as 3-acetoxymethoxycarbonyl-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl (nitroxide 4), which accumulate in cerebral tissue after in situ hydrolysis, and thus enable spatial mapping of O2 concentrations in the mouse brain by EPR imaging. In an effort to improve O2 quantitation, we prepared 3-acetoxymethox ycarbonyl-2,2,5,5-tetra(2H3)methyl-1-(3,4,4-2H3,1-15N)pyrrolidinyloxyl (nitroxide 2), which proved to be a more sensitive probe than its normo-isotopic version for quantifying O2 in aqueous solutions of various O2 concentrations. We now demonstrate that this isotopically substituted nitroxide is ~2-fold more sensitive in vivo than the normo-isotopic nitroxide 4. Moreover, in vitro and in vivo EPR spectral-spatial imaging results with nitroxide 2 demonstrate significant improvement in resolution, reconstruction and spectral response to local O2 concentrations in cerebral tissue. Thus, isotopic-substituted nitroxides, such as 2, are excellent sensors for in vivo O2 quantitation in tissues, such as the brain. PMID:27567323

In vivo EPR oximetry using an isotopically-substituted nitroxide: Potential for quantitative measurement of tissue oxygen

NASA Astrophysics Data System (ADS)

Weaver, John; Burks, Scott R.; Liu, Ke Jian; Kao, Joseph P. Y.; Rosen, Gerald M.

2016-10-01

Variations in brain oxygen (O2) concentration can have profound effects on brain physiology. Thus, the ability to quantitate local O2 concentrations noninvasively in vivo could significantly enhance understanding of several brain pathologies. However, quantitative O2 mapping in the brain has proven difficult. The electron paramagnetic resonance (EPR) spectra of nitroxides are sensitive to molecular O2 and can be used to estimate O2 concentrations in aqueous media. We recently synthesized labile-ester-containing nitroxides, such as 3-acetoxymethoxycarbonyl-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl (nitroxide 4), which accumulate in cerebral tissue after in situ hydrolysis, and thus enable spatial mapping of O2 concentrations in the mouse brain by EPR imaging. In an effort to improve O2 quantitation, we prepared 3-acetoxymethoxycarbonyl-2,2,5,5-tetra(2H3)methyl-1-(3,4,4-2H3,1-15N)pyrrolidinyloxyl (nitroxide 2), which proved to be a more sensitive probe than its normo-isotopic version for quantifying O2 in aqueous solutions of various O2 concentrations. We now demonstrate that this isotopically substituted nitroxide is ∼2-fold more sensitive in vivo than the normo-isotopic nitroxide 4. Moreover, in vitro and in vivo EPR spectral-spatial imaging results with nitroxide 2 demonstrate significant improvement in resolution, reconstruction and spectral response to local O2 concentrations in cerebral tissue. Thus, isotopic-substituted nitroxides, such as 2, are excellent sensors for in vivo O2 quantitation in tissues, such as the brain.

USE OF OXYGEN-18 ISOTOPE LABELING FOR MEASUREMENT OF OXIDATIVE STRESS

EPA Science Inventory

Oxygen-18 (18-O) labeling provides a sensitive means for quantifying oxygen
binding that occurs during in vivo oxidations. Oxidants (ozone, nitrogen
oxides, hydrogen peroxide, etc.) are first synthesized using 18-O, then cells
or tissues are exposed to the labeled ...

Correlation of a Novel Noninvasive Tissue Oxygen Saturation Monitor to Serum Central Venous Oxygen Saturation in Pediatric Patients with Postoperative Congenital Cyanotic Heart Disease

PubMed Central

Yadlapati, Ajay; Grogan, Tristan; Elashoff, David; Kelly, Robert B.

2013-01-01

Abstract: Using a novel noninvasive, visible-light optical diffusion oximeter (T-Stat VLS Tissue Oximeter; Spectros Corporation, Portola Valley, CA) to measure the tissue oxygen saturation (StO2) of the buccal mucosa, the correlation between StO2 and central venous oxygen saturation (ScvO2) was examined in children with congenital cyanotic heart disease undergoing a cardiac surgical procedure. Paired StO2 and serum ScvO2 measurements were obtained postoperatively and statistically analyzed for agreement and association. Thirteen children (nine male) participated in the study (age range, 4 days to 18 months). Surgeries included Glenn shunt procedures, Norwood procedures, unifocalization procedures with Blalock-Taussig shunt placement, a Kawashima/Glenn shunt procedure, a Blalock-Taussig shunt placement, and a modified Norwood procedure. A total of 45 paired StO2-ScvO2 measurements was obtained. Linear regression demonstrated a Pearson’s correlation of .58 (95% confidence interval [CI], .35–.75; p < .0001). The regression slope coefficient estimate was .95 (95% CI, .54–1.36) with an interclass correlation coefficient of .48 (95% CI, .22–.68). Below a clinically relevant average ScvO2 value, a receiver operator characteristic analysis yielded an area under the curve of .78. Statistical methods to control for repeatedly measuring the same subjects produced similar results. This study shows a moderate relationship and agreement between StO2 and ScvO2 measurements in pediatric patients with a history of congenital cyanotic heart disease undergoing a cardiac surgical procedure. This real-time monitoring device can act as a valuable adjunct to standard noninvasive monitoring in which serum ScvO2 sampling currently assists in the diagnosis of low cardiac output after pediatric cardiac surgery. PMID:23691783

3D brain oxygenation measurements in awake hypertensive mice using two photon phosphorescence lifetime imaging

NASA Astrophysics Data System (ADS)

Lu, Xuecong; Moeini, Mohammad; Li, Baoqiang; Zhang, Cong; Sakadžić, Sava; Lesage, Frédéric

2018-02-01

Cardiovascular risk factors, such as hypertension, have been associated with cognitive decline, potentially due to their impact on brain tissue oxygenation. In this study, high spatial resolution imaging in three dimensions was used to understand changes in brain oxygenation with hypertension. Experiments were performed on Young (WT_Y, 3-4 months, n=8), Old (WT_O, 6-7 months, n=8), and Old with hypertension (HP_O, 6-7 months, n=8) C57bL/6 awake mice. Two photon phosphorescence lifetime microscopy using an O2-sensitive phosphorescent dye PtPC343 was employed to measure two dimensional grids of PO2 in capillary beds (400um*400um, 25*25 pixels, acquired in 4 mins) and decays from arterioles. Scans were obtained continuously at depths from 50 um to 300 um under the brain surface. Using 3D measurements and a 250 um depth stack, we removed the compounding effects on brain oxygenation diffusion from surrounding brain vessels. The entire measurement of each vasculature stack required less than 30 minutes. This study indicates that among vascular risk factors, hypertension can reduce oxygen delivery and could potentially contribute to cognition decline.

Visible light optical coherence tomography measures retinal oxygen metabolic response to systemic oxygenation

PubMed Central

Yi, Ji; Liu, Wenzhong; Chen, Siyu; Backman, Vadim; Sheibani, Nader; Sorenson, Christine M.; Fawzi, Amani A.; Linsenmeier, Robert A.; Zhang, Hao F.

2015-01-01

The lack of capability to quantify oxygen metabolism noninvasively impedes both fundamental investigation and clinical diagnosis of a wide spectrum of diseases including all the major blinding diseases such as age-related macular degeneration, diabetic retinopathy, and glaucoma. Using visible light optical coherence tomography (vis-OCT), we demonstrated accurate and robust measurement of retinal oxygen metabolic rate (rMRO2) noninvasively in rat eyes. We continuously monitored the regulatory response of oxygen consumption to a progressive hypoxic challenge. We found that both oxygen delivery, and rMRO2 increased from the highly regulated retinal circulation (RC) under hypoxia, by 0.28 ± 0.08 μL min−1 (p < 0.001), and 0.20 ± 0.04 μL min−1 (p < 0.001) per 100 mmHg systemic pO2 reduction, respectively. The increased oxygen extraction compensated for the deficient oxygen supply from the poorly regulated choroidal circulation. Results from an oxygen diffusion model based on previous oxygen electrode measurements corroborated our in vivo observations. We believe that vis-OCT has the potential to reveal the fundamental role of oxygen metabolism in various retinal diseases. PMID:26658555

Direct oxygen supply with polydimethylsiloxane (PDMS) membranes induces a spontaneous organization of thick heterogeneous liver tissues from rat fetal liver cells in vitro.

PubMed

Hamon, Morgan; Hanada, Sanshiro; Fujii, Teruo; Sakai, Yasuyuki

2012-01-01

Oxygen is a vital nutrient for growth and maturation of in vitro cells (e.g., adult hepatocytes). We previously demonstrated that direct oxygenation through a polydimethylsiloxane (PDMS) membrane increases the oxygen supply to cell cultures and improves hepatocyte functions. In this study, we removed limits on oxygen supply to fetal rat liver cells through the use of direct oxygenation through a PDMS membrane to investigate in vitro growth and maturation. We chose fetal liver cells because they are considered a feasible source of liver progenitor cells for regenerative medicine therapy due to their highly efficient maturation and proliferation. Cells from 17-day-old pregnant rats were cultured under 5% and 21% oxygen atmospheres. Some cells were first cultured under 5% oxygen, and then switched to a 21% oxygen atmosphere. When oxygen supply was enhanced by a PDMS membrane, the rat fetal liver cells organized into a complex tissue composed of an epithelium of hepatocytes above a mesenchyme-like tissue. The thickness of this supportive tissue was directly correlated to oxygen concentration and was thicker under 5% oxygen. When cultures were switched from 5% to 21% oxygen, lumen-containing structures were formed in the thick mesenchymal-like tissue and the albumin secretion rate increased. In addition, cells adapted their glycolytic activity to the oxygen concentrations. This system promoted the formation of a functional and organized thick tissue suitable for use in regenerative medicine.

Flexible Sheet-Type Sensor for Noninvasive Measurement of Cellular Oxygen Metabolism on a Culture Dish.

PubMed

Kojima, Mari; Takehara, Hiroaki; Akagi, Takanori; Shiono, Hirofumi; Ichiki, Takanori

2015-01-01

A novel flexible sensor was developed for the noninvasive oxygen metabolism measurement of cultivated cells and tissues. This device is composed of a transparent double-layered polymer sheet of ethylene-vinyl alcohol (EVOH) and poly(dimethylsiloxane) (PDMS) having an array of microhole structures of 90 μm diameter and 50 μm depth on its surface. All the microhole structures were equipped with a 1-μm-thick optical chemical sensing layer of platinum porphyrin-fluoropolymer on their bottom. The three-dimensional microstructures of the sensor were fabricated by a newly developed simple and low-cost production method named self-aligned hot embossing. The device was designed to be attached slightly above the cells cultivated on a dish to form a temporarily closed microspace over the target cells during measurement. Since the change in oxygen concentration is relatively fast in the microcompartmentalized culture medium, a rapid evaluation of the oxygen consumption rate is possible by measuring the phosphorescence lifetime of the platinum porphyrin-fluoropolymer. The combined use of the device and an automated optical measurement system enabled the high-throughput sensing of cellular oxygen consumption (100 points/min). We monitored the oxygen metabolism of the human breast cancer cell line MCF7 on a Petri dish and evaluated the oxygen consumption rate to be 0.72 ± 0.12 fmol/min/cell. Furthermore, to demonstrate the utility of the developed sensing system, we demonstrated the mapping of the oxygen consumption rate of rat brain slices and succeeded in visualizing a clear difference among the layer structures of the hippocampus, i.e., the cornu ammonis (CA1 and CA3) and dentate gyrus (DG).

Long-term luminescence of sensibilizers in tissues at the conditions of oxygen deficiency due to photodynamic effect

NASA Astrophysics Data System (ADS)

Ishemgulov, A. T.; Letuta, S. N.; Pashkevich, S. N.; Alidzhanov, E. K.; Lantukh, Yu. D.

2017-11-01

Long-term luminescence of organic dyes (xanthene dyes, halogen substituted fluoroscein) was used for an in vitro study of the photodynamic effect of exogenic probes in malignant tumors and healthy tissues of mice. It is shown that the photodynamic activity of oxygen and the dynamics of its concentration in tissues can be estimated from the delayed fluorescence of exogenic probes caused by singlet-triplet annihilation of singlet oxygen and excited triplet states of the molecules of photosensitizer dyes. It is found that quenching of long-term luminescence of photosensitizers significantly differs in tumors and normal tissues.

Detection of reactive oxygen metabolites in malignant and adjacent normal tissues of patients with lung cancer.

PubMed

Okur, Hacer Kuzu; Yuksel, Meral; Lacin, Tunc; Baysungur, Volkan; Okur, Erdal

2013-01-17

Different types of reactive oxygen metabolites (ROMs) are known to be involved in carcinogenesis. Several studies have emphasized the formation of ROMs in ischemic tissues and in cases of inflammation. The increased amounts of ROMs in tumor tissues can either be because of their causative effects or because they are produced by the tumor itself. Our study aimed to investigate and compare the levels of ROMs in tumor tissue and adjacent lung parenchyma obtained from patients with lung cancer. Fifteen patients (all male, mean age 63.6 ± 9 years) with non-small cell lung cancer were enrolled in the study. All patients were smokers. Of the patients with lung cancer, twelve had epidermoid carcinoma and three had adenocarcinoma. During anatomical resection of the lung, tumor tissue and macroscopically adjacent healthy lung parenchyma (control) that was 5 cm away from the tumor were obtained. The tissues were freshly frozen and stored at -20°C. The generation of ROMs was monitored using luminol- and lucigenin-enhanced chemiluminescence (CL) techniques. Both luminol (specific for (.)OH, H(2)O(2), and HOCl(-)) and lucigenin (selective for O(2)(.)(-)) CL measurements were significantly higher in tumor tissues than in control tissues (P <0.001). Luminol and lucigenin CL measurements were 1.93 ± 0.71 and 2.5 ± 0.84 times brighter, respectively, in tumor tissues than in the adjacent parenchyma (P = 0.07). In patients with lung cancer, all ROM levels were increased in tumor tissues when compared with the adjacent lung tissue. Because the increase in lucigenin concentration, which is due to tissue ischemia, is higher than the increase in luminol, which is directly related to the presence and severity of inflammation, ischemia may be more important than inflammation for tumor development in patients with lung cancer.

[Noninvasive estimation of human tissue respiration with wavelet-analysis of oxygen saturation and blood flow oscillations in microvessels].

PubMed

Krupatkin, A I

2012-01-01

Laser Doppler flowmetry, laser spectrophotometry of oxygen saturation and fluorescence determination of NAD-H/FAD ratio were carried out at 30 humans in the upper extremity skin zones with and without arteriole-venule anastomoses (AVA). For the first time it was shown that wavelet-analysis of oxygen saturation and microvascular blood flow oscillations was an effective approach to noninvasive estimation of skin oxygen extraction (OE) and oxygen consumption rate (OC). OE = (SaO2--SvO2)/SaO2, where SaO2 (%) and SvO2(%) are the oxygen saturation of arterial and venular blood, correspondingly. If the ratio between amplitudes of cardiac rhythm (Ac, p.u.) and respiratory rhythm (Ar, p.u.) Ac/Ar < or = 1, SvO2 = SO2. In the case of Ac/Ar >1, SvO2 = SO2/(Ac/Ar). OC = Mnutr x (SaO2-SvO2) in p.u. x %O2, where Mnutr--value of nutritive perfusion (p.u.). Mnutr = M/SI, where SI--shunting index of blood flow in microvessels. The values of perfusion, OE and OC were higher in the skin with AVA than in the skin without AVA. The values of perfusion and oxygen saturation were more variable in the skin with AVA. The greatest significance for tissue metabolism have the oxygen diffused from the smallest arterioles and capillaries. The contribution increased to tissue metabolism of total perfusion and of oxygen diffused from arterioles in the conditions of tissue ischemia.

Measurement of oxygen tension in the ischemic myocardium using encased polargraphic oxygen electrodes.

PubMed

Barrett, J A; Lynch, V D; Balkon, J; Wolf, P S

1986-06-01

The ability to continuously monitor the delicate balance between blood flow and oxygen consumption would be a great asset in the study of myocardial ischemia. The present study was performed, in anesthetized dogs, to validate the use of encased polargraphic oxygen electrodes in the study of myocardial ischemia. Polargraphic oxygen electrodes were placed in the area to be rendered ischemic at fixed tissue depths of 3 mm (epicardium) and 9 mm (endocardium). Endocardial and epicardial oxygen tensions as well as the ratio of endocardial to epicardial oxygen tension and left circumflex coronary flow were monitored. Ischemia was induced by decreasing left circumflex coronary flow by 50%. Upon completion of a 20-min poststenotic period, endocardial pO2, endocardial/epicardial ratio, and coronary flow were significantly decreased (59 +/- 7, 52 +/- 7, and 55 +/- 4%, respectively) whereas epicardial pO2 was slightly decreased. Nitroglycerin (10 micrograms/kg, i.v.) markedly increased endocardial pO2 and endocardial/epicardial ratio above poststenotic control (13 +/- 5 mmHg and 64 +/- 10%, respectively) whereas epicardial pO2 was not significantly decreased. The increases in endocardial pO2 occurred at a point where coronary flow and mean arterial pressure were not significantly changed. Conversely, dipyridamole (125 micrograms/kg, i.v.) significantly increased coronary flow (26 +/- 2 ml/min/100 g) although it did not appreciably alter endocardial or epicardial pO2. It is concluded that encased polargraphic oxygen electrodes provide a quantitative method for determination of oxygen tension in the ischemic myocardium.

In Vivo Imaging of Flavoprotein Fluorescence During Hypoxia Reveals the Importance of Direct Arterial Oxygen Supply to Cerebral Cortex Tissue.

PubMed

Chisholm, K I; Ida, K K; Davies, A L; Papkovsky, D B; Singer, M; Dyson, A; Tachtsidis, I; Duchen, M R; Smith, K J

2016-01-01

Live imaging of mitochondrial function is crucial to understand the important role played by these organelles in a wide range of diseases. The mitochondrial redox potential is a particularly informative measure of mitochondrial function, and can be monitored using the endogenous green fluorescence of oxidized mitochondrial flavoproteins. Here, we have observed flavoprotein fluorescence in the exposed murine cerebral cortex in vivo using confocal imaging; the mitochondrial origin of the signal was confirmed using agents known to manipulate mitochondrial redox potential. The effects of cerebral oxygenation on flavoprotein fluorescence were determined by manipulating the inspired oxygen concentration. We report that flavoprotein fluorescence is sensitive to reductions in cortical oxygenation, such that reductions in inspired oxygen resulted in loss of flavoprotein fluorescence with the exception of a preserved 'halo' of signal in periarterial regions. The findings are consistent with reports that arteries play an important role in supplying oxygen directly to tissue in the cerebral cortex, maintaining mitochondrial function.

Forearm muscle oxygenation decreases with low levels of voluntary contraction

NASA Technical Reports Server (NTRS)

Murthy, G.; Kahan, N. J.; Hargens, A. R.; Rempel, D. M.

1997-01-01

The purpose of our investigation was to determine if the near infrared spectroscopy technique was sensitive to changes in tissue oxygenation at low levels of isometric contraction in the extensor carpi radialis brevis muscle. Nine subjects were seated with the right arm abducted to 45 degrees, elbow flexed to 85 degrees, forearm pronated 45 degrees, and wrist and forearm supported on an armrest throughout the protocol. Altered tissue oxygenation was measured noninvasively with near infrared spectroscopy. The near infrared spectroscopy probe was placed over the extensor carpi radialis brevis of the subject's right forearm and secured with an elastic wrap. After 1 minute of baseline measurements taken with the muscle relaxed, four different loads were applied just proximal to the metacarpophalangeal joint such that the subjects isometrically contracted the extensor carpi radialis brevis at 5, 10, 15, and 50% of the maximum voluntary contraction for 1 minute each. A 3-minute recovery period followed each level of contraction. At the end of the protocol, with the probe still in place, a value for ischemic tissue oxygenation was obtained for each subject. This value was considered the physiological zero and hence 0% tissue oxygenation. Mean tissue oxygenation (+/-SE) decreased from resting baseline (100% tissue oxygenation) to 89 +/- 4, 81 +/- 8, 78 +/- 8, and 47 +/- 8% at 5, 10, 15, and 50% of the maximum voluntary contraction, respectively. Tissue oxygenation levels at 10, 15, and 50% of the maximum voluntary contraction were significantly lower (p < 0.05) than the baseline value. Our results indicate that tissue oxygenation significantly decreases during brief, low levels of static muscle contraction and that near infrared spectroscopy is a sensitive technique for detecting deoxygenation noninvasively at low levels of forearm muscle contraction. Our findings have important implications in occupational medicine because oxygen depletion induced by low levels of muscle

Acetazolamide during acute hypoxia improves tissue oxygenation in the human brain.

PubMed

Wang, Kang; Smith, Zachary M; Buxton, Richard B; Swenson, Erik R; Dubowitz, David J

2015-12-15

Low doses of the carbonic anhydrase inhibitor acetazolamide provides accelerated acclimatization to high-altitude hypoxia and prevention of cerebral and other symptoms of acute mountain sickness. We previously observed increases in cerebral O2 metabolism (CMRO2 ) during hypoxia. In this study, we investigate whether low-dose oral acetazolamide (250 mg) reduces this elevated CMRO2 and in turn might improve cerebral tissue oxygenation (PtiO2 ) during acute hypoxia. Six normal human subjects were exposed to 6 h of normobaric hypoxia with and without acetazolamide prophylaxis. We determined CMRO2 and cerebral PtiO2 from MRI measurements of cerebral blood flow (CBF) and cerebral venous O2 saturation. During normoxia, low-dose acetazolamide resulted in no significant change in CBF, CMRO2 , or PtiO2 . During hypoxia, we observed increases in CBF [48.5 (SD 12.4) (normoxia) to 65.5 (20.4) ml·100 ml(-1)·min(-1) (hypoxia), P < 0.05] and CMRO2 [1.54 (0.19) to 1.79 (0.25) μmol·ml(-1)·min(-1), P < 0.05] and a dramatic decline in PtiO2 [25.0 to 11.4 (2.7) mmHg, P < 0.05]. Acetazolamide prophylaxis mitigated these rises in CBF [53.7 (20.7) ml·100 ml(-1)·min(-1) (hypoxia + acetazolamide)] and CMRO2 [1.41 (0.09) μmol·ml(-1)·min(-1) (hypoxia + acetazolamide)] associated with acute hypoxia but also reduced O2 delivery [6.92 (1.45) (hypoxia) to 5.60 (1.14) mmol/min (hypoxia + acetazolamide), P < 0.05]. The net effect was improved cerebral tissue PtiO2 during acute hypoxia [11.4 (2.7) (hypoxia) to 16.5 (3.0) mmHg (hypoxia + acetazolamide), P < 0.05]. In addition to its renal effect, low-dose acetazolamide is effective at the capillary endothelium, and we hypothesize that local interruption in cerebral CO2 excretion accounts for the improvements in CMRO2 and ultimately in cerebral tissue oxygenation during hypoxia. This study suggests a potentially pivotal role of cerebral CO2 and pH in modulating CMRO2 and PtiO2 during acute hypoxia. Copyright © 2015 the American

Optical Oxygen Micro- and Nanosensors for Plant Applications

PubMed Central

Ast, Cindy; Schmälzlin, Elmar; Löhmannsröben, Hans-Gerd; van Dongen, Joost T.

2012-01-01

Pioneered by Clark's microelectrode more than half a century ago, there has been substantial interest in developing new, miniaturized optical methods to detect molecular oxygen inside cells. While extensively used for animal tissue measurements, applications of intracellular optical oxygen biosensors are still scarce in plant science. A critical aspect is the strong autofluorescence of the green plant tissue that interferes with optical signals of commonly used oxygen probes. A recently developed dual-frequency phase modulation technique can overcome this limitation, offering new perspectives for plant research. This review gives an overview on the latest optical sensing techniques and methods based on phosphorescence quenching in diverse tissues and discusses the potential pitfalls for applications in plants. The most promising oxygen sensitive probes are reviewed plus different oxygen sensing structures ranging from micro-optodes to soluble nanoparticles. Moreover, the applicability of using heterologously expressed oxygen binding proteins and fluorescent proteins to determine changes in the cellular oxygen concentration are discussed as potential non-invasive cellular oxygen reporters. PMID:22969334

Increased oxygen exposure alters collagen expression and tissue architecture during ligature-induced periodontitis.

PubMed

Gajendrareddy, P K; Junges, R; Cygan, G; Zhao, Y; Marucha, P T; Engeland, C G

2017-06-01

The aim of this study was to evaluate the effects of increased oxygen availability on gene expression and on collagen deposition/maturation in the periodontium following disease. Male Wistar rats had ligatures placed around their molars to induce periodontal disease, and a subset of animals underwent hyperbaric oxygen (HBO) treatment for 2 h twice per day. At 15 and 28 d, tissue gene expression of COL1A1, transforming growth factor-β1 and alkaline phosphatase was determined; other histological samples were stained with Picrosirius red to evaluate levels of collagen deposition, maturation and thickness. In animals that underwent HBO treatment, type I collagen expression was higher and collagen deposition, maturation and thickness were more robust. Reduced mRNA levels of transforming growth factor-beta1 and alkaline phosphatase in HBO-treated rats on day 28 suggested that a quicker resolution in both soft tissue and bone remodeling occurred following oxygen treatment. No differences in inflammation were observed between groups. The extracellular matrix regenerated more quickly in the HBO-treated group as evidenced by higher collagen expression, deposition and maturation. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Oxygen tension differentially regulates the functional properties of cartilaginous tissues engineered from infrapatellar fat pad derived MSCs and articular chondrocytes.

PubMed

Buckley, C T; Vinardell, T; Kelly, D J

2010-10-01

For current tissue engineering or regenerative medicine strategies, chondrocyte (CC)- or mesenchymal stem cell (MSC)-seeded constructs are typically cultured in normoxic conditions (20% oxygen). However, within the knee joint capsule a lower oxygen tension exists. The objective of this study was to investigate how CCs and infrapatellar fad pad derived MSCs will respond to a low oxygen (5%) environment in 3D agarose culture. Our hypothesis was that culture in a low oxygen environment (5%) will enhance the functional properties of cartilaginous tissues engineered using both cell sources. Cell-encapsulated agarose hydrogel constructs (seeded with CCs or infrapatellar fat pad (IFP) derived MSCs) were prepared and cultured in a chemically defined serum-free medium in the presence (CCs and MSCs) or absence (CCs only) of transforming growth factor-beta3 (TGF-β3) in normoxic (20%) or low oxygen (5%) conditions for 42 days. Constructs were assessed at days 0, 21 and 42 in terms of mechanical properties, biochemical content and histologically. Low oxygen tension (5%) was observed to promote extracellular matrix (ECM) production by CCs cultured in the absence of TGF-β3, but was inhibitory in the presence of TGF-β3. In contrast, a low oxygen tension enhanced chondrogenesis of IFP constructs in the presence of TGF-β3, leading to superior mechanical functionality compared to CCs cultured in identical conditions. Extrapolating the results of this study to the in vivo setting, it would appear that joint fat pad derived MSCs may possess a superior potential to generate a functional repair tissue in low oxygen tensions. However, in the context of in vitro cartilage tissue engineering, CCs maintained in normoxic conditions in the presence of TGF-β3 generate the most mechanically functional tissue. Copyright © 2010 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.

Measuring Tissue Perfusion During Pressure Relief Maneuvers: Insights Into Preventing Pressure Ulcers

PubMed Central

Makhsous, Mohsen; Priebe, Michael; Bankard, James; Rowles, Diana; Zeigler, Mary; Chen, David; Lin, Fang

2007-01-01

Background/Objective: To study the effect on tissue perfusion of relieving interface pressure using standard wheelchair pushups compared with a mechanical automated dynamic pressure relief system. Design: Repeated measures in 2 protocols on 3 groups of subjects. Participants: Twenty individuals with motor-complete paraplegia below T4, 20 with motor-complete tetraplegia, and 20 able-bodied subjects. Methods: Two 1-hour sitting protocols: dynamic protocol, sitting configuration alternated every 10 minutes between a normal sitting configuration and an off-loading configuration; wheelchair pushup protocol, normal sitting configuration with standard wheelchair pushup once every 20 minutes. Main Outcome Measures: Transcutaneous partial pressures of oxygen and carbon dioxide measured from buttock overlying the ischial tuberosity and interface pressure measured at the seat back and buttocks. Perfusion deterioration and recovery times were calculated during changes in interface pressures. Results: In the off-loading configuration, concentrated interface pressure during the normal sitting configuration was significantly diminished, and tissue perfusion was significantly improved. Wheelchair pushups showed complete relief of interface pressure but incomplete recovery of tissue perfusion. Conclusions: Interface pressure analysis does not provide complete information about the effectiveness of pressure relief maneuvers. Measures of tissue perfusion may help establish more effective strategies. Relief achieved by standard wheelchair pushups may not be sufficient to recover tissue perfusion compromised during sitting; alternate maneuvers may be necessary. The dynamic seating system provided effective pressure relief with sustained reduction in interface pressure adequate for complete recovery of tissue perfusion. Differences in perfusion recovery times between subjects with spinal cord injury (SCI) and controls raise questions about the importance of changes in vascular responses

Overview on recent upper atmosphere atomic oxygen measurements

NASA Astrophysics Data System (ADS)

Zhu, Yajun; Kaufmann, Martin; Chen, Qiuyu; Martin, Riese

2017-04-01

In recent years, new global datasets of atomic oxygen in the upper mesosphere and lower thermosphere have been presented. They are based on airglow measurements from low earth satellites. Surprisingly, the atomic oxygen abundance differs by 30-50% for similar atmospheric conditions. This paper gives an overview on the various atomic oxygen datasets available so far and presents most recent results obtained from measurements on Envisat. Differences between the datasets are discussed.

Oxygen dynamics and transport in the Mediterranean sponge Aplysina aerophoba.

PubMed

Hoffmann, Friederike; Røy, Hans; Bayer, Kristina; Hentschel, Ute; Pfannkuchen, Martin; Brümmer, Franz; de Beer, Dirk

2008-01-01

The Mediterranean sponge Aplysina aerophoba kept in aquaria or cultivation tanks can stop pumping for several hours or even days. To investigate changes in the chemical microenvironments, we measured oxygen profiles over the surface and into the tissue of pumping and non-pumping A. aerophoba specimens with Clark-type oxygen microelectrodes (tip diameters 18-30 μm). Total oxygen consumption rates of whole sponges were measured in closed chambers. These rates were used to back-calculate the oxygen distribution in a finite-element model. Combining direct measurements with calculations of diffusive flux and modeling revealed that the tissue of non-pumping sponges turns anoxic within 15 min, with the exception of a 1 mm surface layer where oxygen intrudes due to molecular diffusion over the sponge surface. Molecular diffusion is the only transport mechanism for oxygen into non-pumping sponges, which allows total oxygen consumption rates of 6-12 μmol cm -3  sponge day -1 . Sponges of different sizes had similar diffusional uptake rates, which is explained by their similar surface/volume ratios. In pumping sponges, oxygen consumption rates were between 22 and 37 μmol cm -3  sponge day -1 , and the entire tissue was oxygenated. Combining different approaches of direct oxygen measurement in living sponges with a dynamic model, we can show that tissue anoxia is a direct function of the pumping behavior. The sponge-microbe system of A. aerophoba thus has the possibility to switch actively between aerobic and anaerobic metabolism by stopping the water flow for more than 15 min. These periods of anoxia will greatly influence physiological variety and activity of the sponge microbes. Detailed knowledge about the varying chemical microenvironments in sponges will help to develop protocols to cultivate sponge-associated microbial lineages and improve our understanding of the sponge-microbe-system.

ARGON, XENON, HYDROGEN, AND THE OXYGEN CONSUMPTION AND GLYCOLYSIS OF MOUSE TISSUE SLICES

PubMed Central

South, Frank E.; Cook, Sherburne F.

1954-01-01

The effects of xenon, argon, and hydrogen on the aerobic and anaerobic metabolism of mouse liver, brain, and sarcoma slices have been investigated. Xenon was found to alter the rates of metabolism of these tissues in a manner almost identical with helium. The gas increased the rate of oxygen consumption in all three tissues and significantly depressed that of anaerobic glycolysis in brain and liver. The depression of glycolysis in sarcoma was less pronounced and not highly significant. Although both the magnitude and statistical significance of the effects observed with argon were much smaller, there was a seeming adherence to the general pattern established by xenon and helium. Hydrogen while remaining essentially ineffective insofar as oxygen uptake was concerned, depressed glycolysis in both liver and brain slices but did not significantly affect sarcoma slices. The following points are stressed in the Discussion: (1) the magnitude and direction of effects exerted by helium, argon, xenon, hydrogen, and nitrogen do not conform with the relative values of molecular weight, density, and solubility of these gases; (2) the effect of these gases on tissue metabolism does not necessarily parallel that exerted upon the whole organism. PMID:13118104

Measurement of dissolved oxygen during red wines tank aging with chips and micro-oxygenation.

PubMed

Nevares, I; del Alamo, M

2008-07-21

Nowadays, micro-oxygenation is a very important technique used in aging wines in order to improve their characteristics. The techniques of wine tank aging imply the use of small doses of oxygen and the addition of wood pieces of oak to the wine. Considering the low dissolved oxygen (DO) levels used by micro-oxygenation technique it is necessary to choose the appropriate measurement principle to apply the precise oxygen dosage in wine at any time, in order to assure its correct assimilation. This knowledge will allow the oenologist to control and run the wine aging correctly. This work is a thorough revision of DO measurement main technologies applied to oenology. It describes the strengths and weaknesses of each of them, and draws a comparison of their workings in wine measurement. Both, the traditional systems by electrochemical probes, and the newest photoluminescence-based probes have been used. These probes adapted to red wines ageing study are then compared. This paper also details the first results of the dissolved oxygen content evolution in red wines during a traditional and alternative tank aging. Samples have been treated by three different ageing systems: oak barrels, stainless-steel tanks with small oak wood pieces (chips) and with bigger oak pieces (staves) with low micro-oxygenation levels. French and American oak barrels manufactured by the same cooperage have been used.

Visible light optical coherence tomography measure retinal oxygen metabolic response to systemic oxygenation (Conference Presentation)

NASA Astrophysics Data System (ADS)

Yi, Ji; Liu, Wenzhong; Chen, Siyu; Backman, Vadim; Sheibani, Nader; Sorenson, Christine M.; Fawzi, Amani A.; Linsenmeier, Robert A.; Zhang, Hao F.

2016-03-01

The lack of capability to quantify oxygen metabolism noninvasively impedes both fundamental investigation and clinical diagnosis of a wide spectrum of diseases including all the major blinding diseases such as age-related macular degeneration, diabetic retinopathy, and glaucoma. Using visible light optical coherence tomography (vis-OCT), we demonstrated accurate and robust measurement of retinal oxygen metabolic rate (rMRO2) noninvasively in rat eyes. The rMRO2 was calculated by concurrent measurement of blood flow and blood oxygen saturation (sO2). Blood flow was calculated by the principle of Doppler optical coherence tomography, where the phase shift between two closely spaced A-lines measures the axial velocity. The distinct optical absorption spectra of oxy- and deoxy-hemoglobin provided the contrast for sO2 measurement, combined with the spectroscopic analysis of vis-OCT signal within the blood vessels. We continuously monitored the regulatory response of oxygen consumption to a progressive hypoxic challenge. We found that both oxygen delivery, and rMRO2 increased from the highly regulated retinal circulation (RC) under hypoxia, by 0.28+/-0.08 μL/min (p<0.001), and 0.20+/-0.04 μL/min (p<0.001) per 100 mmHg systemic pO2 reduction, respectively. The increased oxygen extraction compensated for the deficient oxygen supply from the poorly regulated choroidal circulation (CC).

Modeling the oxygen microheterogeneity of tumors for photodynamic therapy dosimetry

NASA Astrophysics Data System (ADS)

Pogue, Brian W.; Paulsen, Keith D.; O'Hara, Julia A.; Hoopes, P. Jack; Swartz, Harold

2000-03-01

Photodynamic theory of tumors uses optical excitation of a sensitizing drug within tissue to produce large deposits of singlet oxygen, which are thought to ultimately cause the tumor destruction. Predicting dose deposition of singlet oxygen in vivo is challenging because measurement of this species in vivo is not easily achieved. But it is possible to follow the concentration of oxygen in vivo, and so measuring the oxygen concentration transients during PDT may provide a viable method of estimating the delivered dose of singlet oxygen. However modeling the microscopic heterogeneity of the oxygen distribution within a tumor is non-trivial, and predicting the microscopic dose deposition requires further study, but this study present the framework and initial calibration needed or modeling oxygen transport in complex geometries. Computational modeling with finite elements provides a versatile structure within which oxygen diffusion and consumption can be modeled within realistic tissue geometries. This study develops the basic tools required to simulate a tumor region, and examines the role of (i) oxygen supply and consumption rates, (ii) inter- capillary spacing, (iii) photosensitizer distribution, and (iv) differences between simulated tumors and those derived directly from histology. The result of these calculations indicate that realistic tumor tissue capillary networks can be simulated using the finite element method, without excessive computational burden for 2D regions near 1 mm2, and 3D regions near 0.1mm3. These simulations can provide fundamental information about tissue and ways to implement appropriate oxygen measurements. These calculations suggest that photodynamic therapy produces the majority of singlet oxygen in and near the blood vessels, because these are the sites of highest oxygen tension. These calculations support the concept that tumor vascular regions are the major targets for PDT dose deposition.

Diffuse reflectance spectra measured in vivo in human tissues during Photofrin-mediated pleural photodynamic therapy

NASA Astrophysics Data System (ADS)

Finlay, Jarod C.; Zhu, Timothy C.; Dimofte, Andreea; Friedberg, Joseph S.; Hahn, Stephen M.

2006-02-01

Optimal delivery of light in photodynamic therapy (PDT) requires not only optimal placement and power of light sources, but knowledge of the dynamics of light propagation in the tissue being treated and in the surrounding normal tissue, and of their respective accumulations of sensitizer. In an effort to quantify both tissue optical properties and sensitizer distribution, we have measured fluorescence emission and diffuse reflectance spectra at the surface of a variety of tissue types in the thoracic cavities of human patients. The patients studied here were enrolled in Phase II clinical trials of Photofrin-mediated PDT for the treatment of non-small cell lung cancer and cancers with pleural effusion. Patients were given Photofrin at dose of 2 mg per kg body weight 24 hours prior to treatment. Each patient received surgical resection of the affected lung and pleura. Patients received intracavity PDT at 630nm to a dose of 30 J/cm2, as determined by isotropic detectors sutured to the cavity walls. We measured the diffuse reflectance spectra before and after PDT in various positions within the cavity, including tumor, diaphragm, pericardium, skin, and chest wall muscle in 5 patients. The measurements we acquired using a specially designed fiber optic-based probe consisting of one fluorescence excitation fiber, one white light delivery fiber, and 9 detection fibers spaced at distances from 0.36 to 7.8 mm from the source, all of which are imaged via a spectrograph onto a CCD, allowing measurement of radially-resolved diffuse reflectance and fluorescence spectra. The light sources for these two measurements (a 403-nm diode laser and a halogen lamp, respectively) were blocked by computer-controlled shutters, allowing sequential fluorescence, reflectance, and background acquisition. The diffuse reflectance was analyzed to determine the absorption and scattering spectra of the tissue and from these, the concentration and oxygenation of hemoglobin and the local drug uptake

Regional Tissue Oxygen Extraction and Severity of Anemia in Very Low Birth Weight Neonates: A Pilot NIRS Analysis.

PubMed

Mintzer, Jonathan P; Parvez, Boriana; La Gamma, Edmund F

2018-06-15

 Anemia causes blood flow redistribution and altered tissue metabolic behavior to sustain homeostatic oxygen consumption. We hypothesized that anemia severity would correlate with increased regional fractional tissue oxygen extraction among premature neonates.  Regional oxygen extraction was calculated using pulse oximetry and near-infrared spectroscopy data among neonates <1,250 g during their first 10 postnatal days. Oxygen extraction was assessed for correlations with raw hematocrit levels and following grouping into hematocrit quartiles.  Twenty-seven neonates with gestational age 27 ± 2 weeks and birth weight 966 ± 181 g underwent 116 hematocrit determinations. Cerebral and flank oxygen extraction inversely correlated with hematocrit (cerebral r  = -0.527, p  = 0.005; flank r  = -0.485, p  = 0.01). Increased cerebral oxygen extraction was observed for the lowest three hematocrit quartiles (Q1 0.26 ± 0.08, p  = 0.004; Q2 0.24 ± 0.09, p  = 0.01; Q3 0.25 ± 0.09, p  = 0.03; all compared with Q4 0.18 ± 0.10). Increased flank oxygen extraction occurred for the lowest two quartiles (Q1 0.36 ± 0.12, p  < 0.001; Q2 0.35 ± 0.11, p  < 0.001; compared with Q4 0.22 ± 0.13). Splanchnic oxygen extraction demonstrated no similar correlations.  Increases in tissue oxygen extraction may indicate early pathophysiologic responses to nascent anemia in premature neonates. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Diffusion coefficients of oxygen and hemoglobin measured by facilitated oxygen diffusion through hemoglobin solutions.

PubMed

Bouwer, S T; Hoofd, L; Kreuzer, F

1997-03-07

Diffusion coefficients of oxygen (DO2) and hemoglobin (DHb) were obtained from measuring the oxygen flux through thin layers of hemoglobin solutions at 20 degrees C. The liquid layers were supported by a membrane and not soaked in any filter material. Oxygen fluxes were measured from the changes in oxygen partial pressure in the gas phases at both sides of the layer. A mathematical treatment is presented for correct evaluation of the measurements. Measurements were done for bovine and for human hemoglobin. Hemoglobin concentrations (CHb) were between 11 and 42 g/dl, which covers the concentrations in the erythrocyte. Both DO2 and DHb could be fitted to the empirical equation D = D0(1-CHb/C1)10-CHb/C2. The following parameters were obtained: DO = 1.80 x 10(-9) m2/s, C1 = 100 g/dl, C2 = 119 g/dl, for oxygen and D0 = 7.00 x 10(-11) m2/s, C1 = 46 g/dl, C2 = 128 g/dl, for hemoglobin. No difference between the diffusion coefficients of bovine or human hemoglobin was found. The diffusion coefficients of hemoglobin were higher than most values reported in the literature, probably because in this study the mobility of hemoglobin was not hindered by surrounding filter material.

Non-contact tissue perfusion and oxygenation imaging using a LED based multispectral and a thermal imaging system, first results of clinical intervention studies

NASA Astrophysics Data System (ADS)

Klaessens, John H. G. M.; Nelisse, Martin; Verdaasdonk, Rudolf M.; Noordmans, Herke Jan

2013-03-01

During clinical interventions objective and quantitative information of the tissue perfusion, oxygenation or temperature can be useful for the surgical strategy. Local (point) measurements give limited information and affected areas can easily be missed, therefore imaging large areas is required. In this study a LED based multispectral imaging system (MSI, 17 different wavelengths 370nm-880nm) and a thermo camera were applied during clinical interventions: tissue flap transplantations (ENT), local anesthetic block and during open brain surgery (epileptic seizure). The images covered an area of 20x20 cm, when doing measurements in an (operating) room, they turned out to be more complicated than laboratory experiments due to light fluctuations, movement of the patient and limited angle of view. By constantly measuring the background light and the use of a white reference, light fluctuations and movement were corrected. Oxygenation concentration images could be calculated and combined with the thermal images. The effectively of local anesthesia of a hand could be predicted in an early stage using the thermal camera and the reperfusion of transplanted skin flap could be imaged. During brain surgery, a temporary hyper-perfused area was witnessed which was probably related to an epileptic attack. A LED based multispectral imaging system combined with thermal imaging provide complementary information on perfusion and oxygenation changes and are promising techniques for real-time diagnostics during clinical interventions.

Can non-invasive measurement of gut oxygenation predict necrotizing enterocolitis in preterm infants?

USDA-ARS?s Scientific Manuscript database

Factors that contribute to the development of NEC include hypoperfusion or decreased oxygenation of splanchnic tissue. Near-Infrared Spectroscopy (NIRS) will be used to assess gut oxygenation non-invasively. Typically NIRS is primarily used for cerebral hemodynamic monitoring; we intend to apply it ...

Subcutaneous oxygen pressure in spontaneously breathing lean and obese volunteers: a pilot study.

PubMed

Hiltebrand, Luzius B; Kaiser, Heiko A; Niedhart, Dagmar J; Pestel, Gunther; Kurz, Andrea

2008-01-01

Oxidative killing is the primary defense against surgical pathogens; risk of infection is inversely related to tissue oxygenation. Subcutaneous tissue oxygenation in obese patients is significantly less than in lean patients during general anesthesia. However, it remains unknown whether reduced intraoperative tissue oxygenation in obese patients results from obesity per se or from a combination of anesthesia and surgery. In a pilot study, we tested the hypothesis that tissue oxygenation is reduced in spontaneously breathing, unanesthetized obese volunteers. Seven lean volunteers with a body mass index (BMI) of 22 +/- 2 kg/m(2) were compared to seven volunteers with a BMI of 46 +/- 4 kg/m(2). Volunteers were subjected to the following oxygen challenges: (1) room air; (2) 2 l/min oxygen via nasal prongs, (3) 6 l/min oxygen through a rebreathing face mask; (4) oxygen as needed to achieve an arterial oxygen pressure (arterial pO(2)) of 200 mmHg; and (5) oxygen as needed to achieve an arterial pO(2) of 300 mmHg. The oxygen challenges were randomized. Arterial pO(2) was measured with a continuous intraarterial blood gas analyzer (Paratrend 7); deltoid subcutaneous tissue oxygenation was measured with a polarographic microoxygen sensor (Licox). Subcutaneous tissue oxygenation was similar in lean and obese volunteers: (1) room air, 52 +/- 10 vs 58 +/- 8 mmHg; (2) 2 l/min, 77 +/- 25 vs 79 +/- 24 mmHg; (3) 6 l/min, 125 +/- 43 vs 121 +/- 25 mmHg; (4) arterial pO(2) = 200 mmHg, 115 +/- 42 vs 144 +/- 23 mmHg; (5) arterial pO(2) = 300 mmHg, 145 +/- 41 vs 154 +/- 32 mmHg. In this pilot study, we could not identify significant differences in deltoid subcutaneous tissue oxygen pressure between lean and morbidly obese volunteers.

A pseudo-three-dimensional model for quantification of oxygen diffusion from preglomerular arteries to renal tissue and renal venous blood.

PubMed

Lee, Chang-Joon; Ngo, Jennifer P; Kar, Saptarshi; Gardiner, Bruce S; Evans, Roger G; Smith, David W

2017-08-01

To assess the physiological significance of arterial-to-venous (AV) oxygen shunting, we generated a new pseudo-three-dimensional computational model of oxygen diffusion from intrarenal arteries to cortical tissue and veins. The model combines the 11 branching levels (known as "Strahler" orders) of the preglomerular renal vasculature in the rat, with an analysis of an extensive data set obtained using light microscopy to estimate oxygen mass transfer coefficients for each Strahler order. Furthermore, the AV shunting model is now set within a global oxygen transport model that includes transport from arteries, glomeruli, peritubular capillaries, and veins to tissue. While a number of lines of evidence suggest AV shunting is significant, most importantly, our AV oxygen shunting model predicts AV shunting is small under normal physiological conditions (~0.9% of total renal oxygen delivery; range 0.4-1.4%), but increases during renal ischemia, glomerular hyperfiltration (~2.1% of total renal oxygen delivery; range 0.84-3.36%), and some cardiovascular disease states (~3.0% of total renal oxygen delivery; range 1.2-4.8%). Under normal physiological conditions, blood Po 2 is predicted to fall by ~16 mmHg from the root of the renal artery to glomerular entry, with AV oxygen shunting contributing ~40% and oxygen diffusion from arteries to tissue contributing ~60% of this decline. Arterial Po 2 is predicted to fall most rapidly from Strahler order 4 , under normal physiological conditions. We conclude that AV oxygen shunting normally has only a small impact on renal oxygenation, but may exacerbate renal hypoxia during renal ischemia, hyperfiltration, and some cardiovascular disease states. Copyright © 2017 the American Physiological Society.

Normothermic cardiopulmonary bypass increases cerebral tissue oxygenation during combined valve surgery: a single-centre, randomized trial.

PubMed

Lenkin, Andrey I; Zaharov, Viktor I; Lenkin, Pavel I; Smetkin, Alexey A; Bjertnaes, Lars J; Kirov, Mikhail Y

2013-05-01

In cardiac surgery, the choice of temperature regimen during cardiopulmonary bypass (CPB) remains a subject of debate. Hypothermia reduces tissue metabolic demands, but may impair the autoregulation of cerebral blood flow and contribute to neurological morbidity. The aim of this study was to evaluate the effect of two different temperature regimens during CPB on the systemic oxygen transport and the cerebral oxygenation during surgical correction of acquired heart diseases. In a prospective study, we randomized 40 adult patients with combined valvular disorders requiring surgical correction of two or more valves into two groups: (i) a normothermic (NMTH) group (n = 20), in which the body core temperature was maintained at 36.6°C during CPB and (ii) a hypothermic (HPTH) group (n = 20), in which the body was cooled to a core temperature of 32°C maintained throughout the period of CPB. The systemic oxygen transport and the cerebral oxygen saturation (SctO2) were assessed by means of a PiCCO2 haemodynamic monitor and a cerebral oximeter, respectively. All the patients received standard perioperative monitoring. We assessed haemodynamic and oxygen transport parameters, the duration of mechanical ventilation and the length of the ICU and the hospital stays. During CPB, central venous oxygen saturation was significantly higher in the HPTH group but SctO2 was increased in the NMTH group (P < 0.05). Cardiac index, systemic oxygen delivery and consumption increased postoperatively in both groups. However, oxygen delivery and consumption were significantly higher in the NMTH group (P < 0.05). The duration of respiratory support and the length of ICU and hospital stays did not differ between the groups. During combined valve surgery, normothermic CPB provides lower central venous oxygen saturation, but increases cerebral tissue oxygenation when compared with the hypothermic regimen.

Surface pressure measurement by oxygen quenching of luminescence

NASA Technical Reports Server (NTRS)

Gouterman, Martin P. (Inventor); Kavandi, Janet L. (Inventor); Gallery, Jean (Inventor); Callis, James B. (Inventor)

1993-01-01

Methods and compositions for measuring the pressure of an oxygen-containing gas on an aerodynamic surface, by oxygen-quenching of luminescence of molecular sensors is disclosed. Objects are coated with luminescent films containing a first sensor and at least one of two additional sensors, each of the sensors having luminescences that have different dependencies on temperature and oxygen pressure. Methods and compositions are also provided for improving pressure measurements (qualitative or quantitive) on surfaces coated with a film having one or more types of sensor.

Surface pressure measurement by oxygen quenching of luminescence

NASA Technical Reports Server (NTRS)

Gouterman, Martin P. (Inventor); Kavandi, Janet L. (Inventor); Gallery, Jean (Inventor); Callis, James B. (Inventor)

1994-01-01

Methods and compositions for measuring the pressure of an oxygen-containing gas on an aerodynamic surface, by oxygen-quenching of luminescence of molecular sensors is disclosed. Objects are coated with luminescent films containing a first sensor and at least one of two additional sensors, each of the sensors having luminescences that have different dependencies on temperature and oxygen pressure. Methods and compositions are also provided for improving pressure measurements (qualitative or quantitive) on surfaces coated with a film having one or more types of sensor.

Low-oxygen tensions found in Salmonella-infected gut tissue boost Salmonella replication in macrophages by impairing antimicrobial activity and augmenting Salmonella virulence.

PubMed

Jennewein, Jonas; Matuszak, Jasmin; Walter, Steffi; Felmy, Boas; Gendera, Kathrin; Schatz, Valentin; Nowottny, Monika; Liebsch, Gregor; Hensel, Michael; Hardt, Wolf-Dietrich; Gerlach, Roman G; Jantsch, Jonathan

2015-12-01

In Salmonella infection, the Salmonella pathogenicity island-2 (SPI-2)-encoded type three secretion system (T3SS2) is of key importance for systemic disease and survival in host cells. For instance, in the streptomycin-pretreated mouse model SPI-2-dependent Salmonella replication in lamina propria CD11c(-)CXCR1(-) monocytic phagocytes/macrophages (MΦ) is required for the development of colitis. In addition, containment of intracellular Salmonella in the gut critically depends on the antimicrobial effects of the phagocyte NADPH oxidase (PHOX), and possibly type 2 nitric oxide synthase (NOS2). For both antimicrobial enzyme complexes, oxygen is an essential substrate. However, the amount of available oxygen upon enteroinvasive Salmonella infection in the gut tissue and its impact on Salmonella-MΦ interactions was unknown. Therefore, we measured the gut tissue oxygen levels in a model of Salmonella enterocolitis using luminescence two-dimensional in vivo oxygen imaging. We found that gut tissue oxygen levels dropped from ∼78 Torr (∼11% O2) to values of ∼16 Torr (∼2% O2) during infection. Because in vivo virulence of Salmonella depends on the Salmonella survival in MΦ, Salmonella-MΦ interaction was analysed under such low oxygen values. These experiments revealed an increased intracellular replication and survival of wild-type and t3ss2 non-expressing Salmonella. These findings were paralleled by blunted nitric oxide and reactive oxygen species (ROS) production and reduced Salmonella ROS perception. In addition, hypoxia enhanced SPI-2 transcription and translocation of SPI-2-encoded virulence protein. Neither pharmacological blockade of PHOX and NOS2 nor impairment of T3SS2 virulence function alone mimicked the effect of hypoxia on Salmonella replication under normoxic conditions. However, if t3ss2 non-expressing Salmonella were used, hypoxia did not further enhance Salmonella recovery in a PHOX and NOS2-deficient situation. Hence, these data suggest that

Simultaneous detection of molecular oxygen and water vapor in the tissue optical window using tunable diode laser spectroscopy.

PubMed

Persson, Linda; Lewander, Märta; Andersson, Mats; Svanberg, Katarina; Svanberg, Sune

2008-04-20

We report on a dual-diode laser spectroscopic system for simultaneous detection of two gases. The technique is demonstrated by performing gas measurements on absorbing samples such as an air distance, and on absorbing and scattering porous samples such as human tissue. In the latter it is possible to derive the concentration of one gas by normalizing to a second gas of known concentration. This is possible if the scattering and absorption of the bulk material is equal or similar for the two wavelengths used, resulting in a common effective pathlength. Two pigtailed diode lasers are operated in a wavelength modulation scheme to detect molecular oxygen ~760 nm and water vapor ~935 nm within the tissue optical window (600 nm to 1.3 mum). Different modulation frequencies are used to distinguish between the two wavelengths. No crosstalk can be observed between the gas contents measured in the two gas channels. The system is made compact by using a computer board and performing software-based lock-in detection. The noise floor obtained corresponds to an absorption fraction of approximately 6x10(-5) for both oxygen and water vapor, yielding a minimum detection limit of ~2 mm for both gases in ambient air. The power of the technique is illustrated by the preliminary results of a clinical trial, nonintrusively investigating gas in human sinuses.

The Impact of Red Blood Cell Transfusion on Cerebral Tissue Oxygen Saturation in Severe Traumatic Brain Injury.

PubMed

McCredie, Victoria A; Piva, Simone; Santos, Marlene; Xiong, Wei; de Oliveira Manoel, Airton Leonardo; Rigamonti, Andrea; Hare, Gregory M T; Chapman, Martin G; Baker, Andrew J

2017-04-01

There are a range of opinions on the benefits and thresholds for the transfusion of red blood cells in critically ill patients with traumatic brain injury (TBI) and an urgent need to understand the neurophysiologic effects. The aim of this study was to examine the influence of red blood cell transfusions on cerebral tissue oxygenation (SctO 2 ) in critically ill TBI patients. This prospective observational study enrolled consecutive TBI patients with anemia requiring transfusion. Cerebral tissue oxygen saturation (SctO 2 ) was measured noninvasively with bilateral frontal scalp probes using near-infrared spectroscopy (NIRS) technology. Data were collected at baseline and for 24 h after transfusion. The primary outcome was the applicability of a four-wavelength near-infrared spectrometer to monitor SctO 2 changes during a transfusion. Secondary outcomes included the correlation of SctO 2 with other relevant physiological variables, the dependence of SctO 2 on baseline hemoglobin and transfusion, and the effect of red blood cell transfusion on fractional tissue oxygen extraction. We enrolled 24 patients with severe TBI, of which five patients (21 %) were excluded due to poor SctO 2 signal quality from large subdural hematomas and bifrontal decompressive craniectomies. Twenty transfusions were monitored in 19 patients. The mean pre- and post-transfusion hemoglobin concentrations were significantly different [74 g/L (SD 8 g/L) and 84 g/L (SD 9 g/L), respectively; p value <0.0001]. Post-transfusion SctO 2 was not significantly greater than pre-transfusion SctO 2 [left-side pre-transfusion 69 % (SD 7) vs. post-transfusion 70 % (SD 10); p = 0.68, and right-side pre-transfusion 69 % (SD 5) vs. post-transfusion 71 % (SD 7); p = 0.11]. In a multivariable mixed linear analysis, mean arterial pressure was the only variable significantly associated with a change in SctO 2 . The bifrontal method of recording changes in NIRS signal was not able to detect a

Measuring oxygen tension modulation, induced by a new pre-radiotherapy therapeutic, in a mammary window chamber mouse model

NASA Astrophysics Data System (ADS)

Schafer, Rachel; Gmitro, Arthur F.

2015-03-01

Tumor regions under hypoxic or low oxygen conditions respond less effectively to many treatment strategies, including radiation therapy. A novel investigational therapeutic, NVX-108 (NuvOx Pharma), has been developed to increase delivery of oxygen through the use of a nano-emulsion of dodecofluoropentane. By raising pO2 levels prior to delivering radiation, treatment efficacy may be improved. To aid in evaluating the novel drug, oxygen tension was quantitatively measured, spatially and temporally, to record the effect of administrating NVX-108 in an orthotopic mammary window chamber mouse model of breast cancer. The oxygen tension was measured through the use of an oxygen-sensitive coating, comprised of phosphorescent platinum porphyrin dye embedded in a polystyrene matrix. The coating, applied to the surface of the coverslip of the window chamber through spin coating, is placed in contact with the mammary fat pad to record the oxygenation status of the surface tissue layer. Prior to implantation of the window chamber, a tumor is grown in the SCID mouse model by injection of MCF-7 cells into the mammary fat pad. Two-dimensional spatial distributions of the pO2 levels were obtained through conversion of measured maps of phosphorescent lifetime. The resulting information on the spatial and temporal variation of the induced oxygen modulation could provide valuable insight into the optimal timing between administration of NVX-108 and radiation treatment to provide the most effective treatment outcome.

Quantitative evaluation of ViOptix's tissue oximeter in an ex-vivo animal model

NASA Astrophysics Data System (ADS)

Mao, Jimmy J. M.; Xu, Ronald; Lash, Bob; Wright, Leigh

2008-02-01

We evaluate the performance of ODISsey TM Tissue Oximeter (ViOptix, Inc., Fremont, CA) against co-oximeter. Concurrent oxygen saturation measurements were made in three dog limbs surgically removed and perfused with an extracorporeal blood circulation system. Oxygen saturation was adjusted in steps ranging from 95% down to 5% as monitored by the co-oximeter. The co-oximeter was used to measure the oxygen saturation of the whole blood drawn from both the arterial and the venous ports of the limb. The tissue oxygenation measured by the ODISsey TM tissue oximeter was compared with the average of the arterial and the venous blood oxygenation measured by the co-oximeter. Linear correlation was observed between the average oxygenation given by the co-oximeter and the ODISseyTM readings, with a root-mean-square difference of 7.6% and the correlation coefficient of 0.941, calculated from N = 194 data points.

Effects of homocysteine and its related compounds on oxygen consumption of the rat heart tissue homogenate: the role of different gasotransmitters.

PubMed

Uzelac, Jovana Jakovljević; Stanić, Marina; Krstić, Danijela; Čolović, Mirjana; Djurić, Dragan

2017-11-29

The objective of this study was to investigate in vitro effects of 10 µM DL-homocysteine (DL-Hcy), DL-homocysteine thiolactone-hydrochloride (DL-Hcy TLHC), and L-homocysteine thiolactone-hydrochloride (L-Hcy TLHC) on the oxygen consumption of rat heart tissue homogenate, as well as the involvement of the gasotransmitters NO, H 2 S and CO in the effects of the most toxic homocysteine compound, DL-Hcy TLHC. The possible contribution of the gasotransmitters in these effects was estimated by using the appropriate inhibitors of their synthesis (N ω -nitro-L-arginine methyl ester (L-NAME), DL-propargylglycine (DL-PAG), and zinc protoporphyrin IX (ZnPPR IX), respectively). The oxygen consumption of rat heart tissue homogenate was measured by Clark/type oxygen electrode in the absence and presence of the investigated compounds. All three homocysteine-based compounds caused a similar decrease in the oxygen consumption rate compared to control: 15.19 ± 4.01%, 12.42 ± 1.01%, and 16.43 ± 4.52% for DL-Hcy, DL-Hcy TLHC, or L-Hcy TLHC, respectively. All applied inhibitors of gasotransmitter synthesis also decreased the oxygen consumption rate of tissue homogenate related to control: 13.53 ± 1.35% for L-NAME (30 µM), 5.32 ± 1.23% for DL-PAG (10 µM), and 5.56 ± 1.39% for ZnPPR IX (10 µM). Simultaneous effect of L-NAME (30 µM) or ZnPPR IX (10 µM) with DL-Hcy TLHC (10 µM) caused a larger decrease of oxygen consumption compared to each of the substances individually. However, when DL-PAG (10 µM) was applied together with DL-Hcy TLHC (10 µM), it attenuated the effect of DL-Hcy TLHC from 12.42 ± 1.01 to 9.22 ± 1.58%. In conclusion, cardiotoxicity induced by Hcy-related compounds, which was shown in our previous research, could result from the inhibition of the oxygen consumption, and might be mediated by the certain gasotransmitters.

Brain Tissue PO2 Measurement During Normoxia and Hypoxia Using Two-Photon Phosphorescence Lifetime Microscopy.

PubMed

Xu, Kui; Boas, David A; Sakadžić, Sava; LaManna, Joseph C

2017-01-01

Key to the understanding of the principles of physiological and structural acclimatization to changes in the balance between energy supply (represented by substrate and oxygen delivery, and mitochondrial oxidative phosphorylation) and energy demand (initiated by neuronal activity) is to determine the controlling variables, how they are sensed and the mechanisms initiated to maintain the balance. The mammalian brain depends completely on continuous delivery of oxygen to maintain its function. We hypothesized that tissue oxygen is the primary sensed variable. In this study two-photon phosphorescence lifetime microscopy (2PLM) was used to determine and define the tissue oxygen tension field within the cerebral cortex of mice to a cortical depth of between 200-250 μm under normoxia and acute hypoxia (FiO 2  = 0.10). High-resolution images can provide quantitative distributions of oxygen and intercapillary oxygen gradients. The data are best appreciated by quantifying the distribution histogram that can then be used for analysis. For example, in the brain cortex of a mouse, at a depth of 200 μm, tissue oxygen tension was mapped and the distribution histogram was compared under normoxic and mild hypoxic conditions. This powerful method can provide for the first time a description of the delivery and availability of brain oxygen in vivo.

Quantitative brain tissue oximetry, phase spectroscopy and imaging the range of homeostasis in piglet brain.

PubMed

Chance, Britton; Ma, Hong Yan; Nioka, Shoko

2003-01-01

The quantification of tissue oxygen by frequency or time domain methods has been discussed in a number of prior publications where the meaning of the tissue hemoglobin oxygen saturation was unclear and where the CW instruments were unsuitable for proper quantitative measurements [1, 2]. The development of the IQ Phase Meter has greatly simplified and made reliable the difficult determination of precise phase and amplitude signals from brain. This contribution reports on the calibration of the instrument in model systems and the use of the instrument to measure tissue saturation (StO2) in a small animal model. In addition, a global interpretation of the meaning of tissue oxygen has been formulated based on the idea that autoregulation will maintain tissue oxygen at a fixed value over a range of arterial and venous oxygen values over the range of autoregulation. Beyond that range, the tissue oxygen is still correctly measured but, as expected, approaches the arterial saturation at low metabolic rates and the venous saturation at high metabolic rates of mitochondria.

Biochemical changes related to hypoxia during cerebral aneurysm surgery: combined microdialysis and tissue oxygen monitoring: case report.

PubMed

Hutchinson, P J; Al-Rawi, P G; O'Connell, M T; Gupta, A K; Pickard, J D; Kirkpatrick, P J

2000-01-01

The objective of this study was to monitor brain metabolism on-line during aneurysm surgery, by combining the use of a multiparameter (brain tissue oxygen, brain carbon dioxide, pH, and temperature) sensor with microdialysis (extracellular glucose, lactate, pyruvate, and glutamate). The case illustrates the potential value of these techniques by demonstrating the effects of adverse physiological events on brain metabolism and the ability to assist in both intraoperative and postoperative decision-making. A 41-year-old woman presented with a World Federation of Neurological Surgeons Grade I subarachnoid hemorrhage. Angiography revealed a basilar artery aneurysm that was not amenable to coiling, so the aneurysm was clipped. Before the craniotomy was performed, a multiparameter sensor and a microdialysis catheter were inserted to monitor brain metabolism. During the operation, the brain oxygen level decreased, in relation to biochemical changes, including the reduction of extracellular glucose and pyruvate and the elevation of lactate and glutamate. These changes were reversible. However, when the craniotomy was closed, a second decrease in brain oxygen occurred in association with brain swelling, which immediately prompted a postoperative computed tomographic scan. The scan demonstrated acute hydrocephalus, requiring external ventricular drainage. The patient made a full recovery. The monitoring techniques influenced clinical decision-making in the treatment of this patient. On-line measurement of brain tissue gases and extracellular chemistry has the potential to assist in the perioperative and postoperative management of patients undergoing complex cerebrovascular surgery and to establish the effects of intervention on brain homeostasis.

Influence of exercise duration on cardiorespiratory responses, energy cost and tissue oxygenation within a 6 hour treadmill run.

PubMed

Kerhervé, Hugo A; McLean, Scott; Birkenhead, Karen; Parr, David; Solomon, Colin

2017-01-01

The physiological mechanisms for alterations in oxygen utilization ([Formula: see text]) and the energy cost of running ( C r ) during prolonged running are not completely understood, and could be linked with alterations in muscle and cerebral tissue oxygenation. Eight trained ultramarathon runners (three women; mean ± SD; age 37 ± 7 yr; maximum [Formula: see text] 60 ± 15 mL min -1  kg -1 ) completed a 6 hr treadmill run (6TR), which consisted of four modules, including periods of moderate (3 min at 10 km h -1 , 10-CR) and heavy exercise intensities (6 min at 70% of maximum [Formula: see text], HILL), separated by three, 100 min periods of self-paced running (SP). We measured [Formula: see text], minute ventilation ([Formula: see text]), ventilatory efficiency ([Formula: see text]), respiratory exchange ratio (RER), C r , muscle and cerebral tissue saturation index (TSI) during the modules, and heart rate (HR) and perceived exertion (RPE) during the modules and SP. Participants ran 58.3 ± 10.5 km during 6TR. Speed decreased and HR and RPE increased during SP. Across the modules, HR and [Formula: see text] increased (10-CR), and RER decreased (10-CR and HILL). There were no significant changes in [Formula: see text], [Formula: see text], C r , TSI and RPE across the modules. In the context of positive pacing (decreasing speed), increased cardiac drift and perceived exertion over the 6TR, we observed increased RER and increased HR at moderate and heavy exercise intensity, increased [Formula: see text] at moderate intensity, and no effect of exercise duration on ventilatory efficiency, energy cost of running and tissue oxygenation.

Note: Measuring instrument of singlet oxygen quantum yield in photodynamic effects

NASA Astrophysics Data System (ADS)

Li, Zhongwei; Zhang, Pengwei; Zang, Lixin; Qin, Feng; Zhang, Zhiguo; Zhang, Hongli

2017-06-01

Using diphenylisobenzofuran (C20H14O) as a singlet oxygen (1O2) reporter, a comparison method, which can be used to measure the singlet oxygen quantum yield (ΦΔ) of the photosensitizer quantitatively, is presented in this paper. Based on this method, an automatic measuring instrument of singlet oxygen quantum yield is developed. The singlet oxygen quantum yield of the photosensitizer hermimether and aloe-emodin is measured. It is found that the measuring results are identical to the existing ones, which verifies the validity of the measuring instrument.

Blood oxygen binding in hypoxaemic calves.

PubMed

Cambier, Carole; Clerbaux, Thierry; Detry, Bruno; Marville, Vincent; Frans, Albert; Gustin, Pascal

2002-01-01

Blood oxygen transport and tissue oxygenation were studied in 28 calves from the Belgian White and Blue breed (20 healthy and 8 hypoxaemic ones). Hypoxaemic calves were selected according to their high respiratory frequency and to their low partial oxygen pressure (PaO2) in the arterial blood. Venous and arterial blood samples were collected, and 2,3-diphosphoglycerate, adenosine triphosphate, chloride, inorganic phosphate and hemoglobin concentrations, and pH, PCO, and PO2 were determined. An oxygen equilibrium curve (OEC) was measured in standard conditions, for each animal. The arterial and venous OEC were calculated, taking body temperature, pH and PCO2 values in arterial and venous blood into account. The oxygen exchange fraction (OEF%), corresponding to the degree of blood desaturation between the arterial and the venous compartments, and the amount of oxygen released at the tissue level by 100 mL of blood (OEF Vol%) were calculated from the arterial and venous OEC combined with the PO2 and hemoglobin concentration. In hypoxaemic calves investigated in this study, the hemoglobin oxygen affinity, measured under standard conditions, was not modified. On the contrary, in vivo acidosis and hypercapnia induced a decrease in the hemoglobin oxygen affinity in arterial blood, which combined to the decrease in PaO2 led to a reduced hemoglobin saturation degree in the arterial compartment. However, this did not impair the oxygen exchange fraction (OEF%), since the hemoglobin saturation degree in venous blood was also diminished.

Aggregate Formation of Oligonucleotides that Assist Molecular Imaging for Tracking of the Oxygen Status in Tumor Tissue.

PubMed

Yoshihara, Kazuki; Takagi, Kohei; Son, Aoi; Kurihara, Ryohsuke; Tanabe, Kazuhito

2017-08-17

The use of DNA aggregates could be a promising strategy for the molecular imaging of biological functions. Herein, phosphorescent oligodeoxynucleotides were designed with the aim of visualizing oxygen fluctuation in tumor cells. DNA-ruthenium conjugates (DRCs) that consisted of oligodeoxynucleotides, a phosphorescent ruthenium complex, a pyrene unit for high oxygen responsiveness, and a nitroimidazole unit as a tumor-targeting unit were prepared. In general, oligonucleotides have low cell permeability because of their own negative charges; however, the DRC formed aggregates in aqueous solution due to the hydrophobic pyrene and nitroimidazole groups, and smoothly penetrated the cellular membrane to accumulate in tumor cells in a hypoxia-selective manner. The oxygen-dependent phosphorescence of DRC in cells was also observed. In vivo experiments revealed that aggregates of DRC accumulated in hypoxic tumor tissue that was transplanted into the left leg of mice, and showed that oxygen fluctuations in tumor tissue could be monitored by tracking of the phosphorescence emission of DRC. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Single-cell measurement of red blood cell oxygen affinity.

PubMed

Di Caprio, Giuseppe; Stokes, Chris; Higgins, John M; Schonbrun, Ethan

2015-08-11

Oxygen is transported throughout the body by hemoglobin (Hb) in red blood cells (RBCs). Although the oxygen affinity of blood is well-understood and routinely assessed in patients by pulse oximetry, variability at the single-cell level has not been previously measured. In contrast, single-cell measurements of RBC volume and Hb concentration are taken millions of times per day by clinical hematology analyzers, and they are important factors in determining the health of the hematologic system. To better understand the variability and determinants of oxygen affinity on a cellular level, we have developed a system that quantifies the oxygen saturation, cell volume, and Hb concentration for individual RBCs in high throughput. We find that the variability in single-cell saturation peaks at an oxygen partial pressure of 2.9%, which corresponds to the maximum slope of the oxygen-Hb dissociation curve. In addition, single-cell oxygen affinity is positively correlated with Hb concentration but independent of osmolarity, which suggests variation in the Hb to 2,3-diphosphoglycerate (2-3 DPG) ratio on a cellular level. By quantifying the functional behavior of a cellular population, our system adds a dimension to blood cell analysis and other measurements of single-cell variability.

Investigation of laser-tissue interaction in medicine by means of laser spectroscopic measurements

NASA Astrophysics Data System (ADS)

Lademann, Juergen; Weigmann, Hans-Juergen

1995-01-01

Toxic and carcinogenic substances were produced during laser application in medicine for the cutting and evaporation of tissue. The laser smoke presents a danger potential for the medical staff and the patients. The laser tissue interaction process was investigated by means of laser spectroscopic measurements which give the possibility of measuring metastable molecular states directly as a prerequisite to understand and to influence fundamental laser tissue interaction processes in order to reduce the amount of harmful chemicals. Highly excited atomic and molecular states and free radicals (CN, OH, C2, CH, CH2) have been detected applying spontaneous and laser induced fluorescence methods. It was found that the formation of harmful substances in the laser plumes can be reduced significantly by optimization of the surrounding gas atmosphere. A high content of oxygen or water in the interaction zone has been found, in agreement with the results of classical and analytical methods, as a suitable way to decrease pollutant emission. The experimental methods and the principal results are applicable not only in laser medicine but in laser material treatment generally.

Comparison of cerebral tissue oxygenation values in full term and preterm newborns by the simultaneous use of two near-infrared spectroscopy devices: an absolute and a relative trending oximeter

NASA Astrophysics Data System (ADS)

Szczapa, Tomasz; Karpiński, Łukasz; Moczko, Jerzy; Weindling, Michael; Kornacka, Alicja; Wróblewska, Katarzyna; Adamczak, Aleksandra; Jopek, Aleksandra; Chojnacka, Karolina; Gadzinowski, Janusz

2013-08-01

The aim of this study is to compare a two-wavelength light emitting diode-based tissue oximeter (INVOS), which is designed to show trends in tissue oxygenation, with a four-wavelength laser-based oximeter (FORE-SIGHT), designed to deliver absolute values of tissue oxygenation. Simultaneous values of cerebral tissue oxygenation (StO2) are measured using both devices in 15 term and 15 preterm clinically stable newborns on the first and third day of life. Values are recorded simultaneously in two periods between which oximeter sensor positions are switched to the contralateral side. Agreement between StO2 values before and after the change of sensor position is analyzed. We find that mean cerebral StO2 values are similar between devices for term and preterm babies, but INVOS shows StO2 values spread over a wider range, with wider standard deviations than shown by the FORE-SIGHT. There is relatively good agreement with a bias up to 3.5% and limits of agreement up to 11.8%. Measurements from each side of the forehead show better repeatability for the FORE-SIGHT monitor. We conclude that performance of the two devices is probably acceptable for clinical purposes. Both performed sufficiently well, but the use of FORE-SIGHT may be associated with tighter range and better repeatability of data.

[Observation on changes of oxygen partial pressure in the deep tissues along the large intestine meridian during acupuncture in healthy subjects].

PubMed

Chen, Ming; Hu, Xiang-long; Wu, Zu-xing

2010-06-01

To observe changes of the partial oxygen pressure in the deep tissues along the Large Intestine Meridian (LIM) during acupuncture stimulation, so as to reveal the characteristics of energy metabolism in the tissues along the LIM. Thirty-one healthy volunteer subjects were enlisted in the present study. Partial oxygen pressure (POP) in the tissues (at a depth of about 1.5 cm) of acupoints Binao (LI 14), Shouwuli (LI 13), Shousanli (LI 10), 2 non-acupoints [the midpoints between Quchi (LI 11) and LI 14, and between Yangxi (LI 5) and LI 11) of the LIM, and 10 non-meridian points, 1.5-2.0 cm lateral and medial to each of the tested points of the LIM was detected before, during and after electroacupuncture (EA) stimulation of Hegu (LI 4) by using a tissue oxygen tension needle-like sensor. In normal condition, the POP values in the deep tissues along the LIM were significantly higher than those of the non-meridian control points on its bilateral sides. During and after EA of Hegu (LI 4), the POP levels decreased significantly in the deep tissues along the LIM in comparison with pre-EA (P < 0.01), and had no apparent changes in the non-meridian control points (P > 0.05). POP is significantly higher in the deep tissues along the LIM of healthy subjects under normal conditions, which can be downregulated by EA of Hegu (LI 4), suggesting an increase of both the utilization rate of oxygen and energy metabolism after EA.

Quantitative measurement of oxygen in microgravity combustion

NASA Technical Reports Server (NTRS)

Silver, Joel A.

1995-01-01

This research combines two innovations in an experimental system which should result in a new capability for quantitative, nonintrusive measurement of major combustion species. Using a newly available vertical cavity surface-emitting diode laser (VCSEL) and an improved spatial scanning method, we plan to measure the temporal and spatial profiles of the concentrations and temperatures of molecular oxygen in a candle flame and in a solid fuel (cellulose sheet) system. The required sensitivity for detecting oxygen is achieved by the use of high frequency wavelength modulation spectroscopy (WMS). Measurements will be performed in the NASA Lewis 2.2-second Drop Tower Facility. The objective of this research is twofold. First, we want to develop a better understanding of the relative roles of diffusion and reaction of oxygen in microgravity combustion. As the primary oxidizer species, oxygen plays a major role in controlling the observed properties of flames, including flame front speed (in solid or liquid flames), extinguishment characteristics, flame size, and flame temperature. The second objective is to develop better diagnostics based on diode laser absorption which can be of real value in microgravity combustion research. We will also demonstrate diode lasers' potential usefulness for compact, intrinsically-safe monitoring sensors aboard spacecraft. Such sensors could be used to monitor any of the major cabin gases as well as important pollutants.

Oxygen limitation and tissue metabolic potential of the African fish Barbus neumayeri: roles of native habitat and acclimatization

PubMed Central

2011-01-01

Background Oxygen availability in aquatic habitats is a major environmental factor influencing the ecology, behaviour, and physiology of fishes. This study evaluates the contribution of source population and hypoxic acclimatization of the African fish, Barbus neumayeri, in determining growth and tissue metabolic enzyme activities. Individuals were collected from two sites differing dramatically in concentration of dissolved oxygen (DO), Rwembaita Swamp (annual average DO 1.35 mgO2 L-1) and Inlet Stream West (annual average DO 5.58 mgO2 L-1) in Kibale National Park, Uganda, and reciprocally transplanted using a cage experiment in the field, allowing us to maintain individuals under natural conditions of oxygen, food availability, and flow. Fish were maintained under these conditions for four weeks and sampled for growth rate and the activities of phosphofructokinase (PFK), lactate dehydrogenase (LDH), citrate synthase (CS), and cytochrome c oxidase (CCO) in four tissues, liver, heart, brain, and skeletal muscle. Results Acclimatization to the low DO site resulted in lower growth rates, lower activities of the aerobic enzyme CCO in heart, and higher activities of the glycolytic enzyme PFK in heart and skeletal muscle. The activity of LDH in liver tissue was correlated with site of origin, being higher in fish collected from a hypoxic habitat, regardless of acclimatization treatment. Conclusions Our results suggest that the influence of site of origin and hypoxic acclimatization in determining enzyme activity differs among enzymes and tissues, but both factors contribute to higher glycolytic capacity and lower aerobic capacity in B. neumayeri under naturally-occurring conditions of oxygen limitation. PMID:21251277

Oxygen limitation and tissue metabolic potential of the African fish Barbus neumayeri: roles of native habitat and acclimatization.

PubMed

Martínez, Mery L; Raynard, Erin L; Rees, Bernard B; Chapman, Lauren J

2011-01-20

Oxygen availability in aquatic habitats is a major environmental factor influencing the ecology, behaviour, and physiology of fishes. This study evaluates the contribution of source population and hypoxic acclimatization of the African fish, Barbus neumayeri, in determining growth and tissue metabolic enzyme activities. Individuals were collected from two sites differing dramatically in concentration of dissolved oxygen (DO), Rwembaita Swamp (annual average DO 1.35 mgO2 L(-1)) and Inlet Stream West (annual average DO 5.58 mgO2 L(-1)) in Kibale National Park, Uganda, and reciprocally transplanted using a cage experiment in the field, allowing us to maintain individuals under natural conditions of oxygen, food availability, and flow. Fish were maintained under these conditions for four weeks and sampled for growth rate and the activities of phosphofructokinase (PFK), lactate dehydrogenase (LDH), citrate synthase (CS), and cytochrome c oxidase (CCO) in four tissues, liver, heart, brain, and skeletal muscle. Acclimatization to the low DO site resulted in lower growth rates, lower activities of the aerobic enzyme CCO in heart, and higher activities of the glycolytic enzyme PFK in heart and skeletal muscle. The activity of LDH in liver tissue was correlated with site of origin, being higher in fish collected from a hypoxic habitat, regardless of acclimatization treatment. Our results suggest that the influence of site of origin and hypoxic acclimatization in determining enzyme activity differs among enzymes and tissues, but both factors contribute to higher glycolytic capacity and lower aerobic capacity in B. neumayeri under naturally-occurring conditions of oxygen limitation.

Oxygen diffusion: an enzyme-controlled variable parameter.

PubMed

Erdmann, Wilhelm; Kunke, Stefan

2014-01-01

Previous oxygen microelectrode studies have shown that the oxygen diffusion coefficient (DO₂) increases during extracellular PO₂ decreases, while intracellular PO₂ remained unchanged and thus cell function (spike activity of neurons). Oxygen dependency of complex multicellular organisms requires a stable and adequate oxygen supply to the cells, while toxic concentrations have to be avoided. Oxygen brought to the tissue by convection diffuses through the intercellular and cell membranes, which are potential barriers to diffusion. In gerbil brain cortex, PO₂ and DO₂ were measured by membrane-covered and by bare gold microelectrodes, as were also spike potentials. Moderate respiratory hypoxia was followed by a primary sharp drop of tissue PO₂ that recovered to higher values concomitant with an increase of DO₂. A drop in intracellular PO₂ recovered immediately. Studies on the abdominal ganglion of aplysia californica showed similar results.Heterogeneity is a feature of both normal oxygen supply to tissue and supply due to a wide range of disturbances in oxygen supply. Oxygen diffusion through membranes is variable thereby ensuring adequate intracellular PO₂. Cell-derived glucosamine oxidase seems to regulate the polymerization/depolymerisation ratio of membrane mucopolysaccharides and thus oxygen diffusion.Variability of oxygen diffusion is a decisive parameter for regulating the supply/demand ratio of oxygen supply to the cell; this occurs in highly developed animals as well as in species of a less sophisticated nature. Autoregulation of oxygen diffusion is as important as the distribution/perfusion ratio of the capillary meshwork and as the oxygen extraction ratio in relation to oxygen consumption of the cell. Oxygen diffusion resistance is the cellular protection against luxury oxygen supply (which can result in toxic oxidative species leading to mutagenesis).

Microfabricated Collector-Generator Electrode Sensor for Measuring Absolute pH and Oxygen Concentrations.

PubMed

Dengler, Adam K; Wightman, R Mark; McCarty, Gregory S

2015-10-20

Fast-scan cyclic voltammetry (FSCV) has attracted attention for studying in vivo neurotransmission due to its subsecond temporal resolution, selectivity, and sensitivity. Traditional FSCV measurements use background subtraction to isolate changes in the local electrochemical environment, providing detailed information on fluctuations in the concentration of electroactive species. This background subtraction removes information about constant or slowly changing concentrations. However, determination of background concentrations is still important for understanding functioning brain tissue. For example, neural activity is known to consume oxygen and produce carbon dioxide which affects local levels of oxygen and pH. Here, we present a microfabricated microelectrode array which uses FSCV to detect the absolute levels of oxygen and pH in vitro. The sensor is a collector-generator electrode array with carbon microelectrodes spaced 5 μm apart. In this work, a periodic potential step is applied at the generator producing transient local changes in the electrochemical environment. The collector electrode continuously performs FSCV enabling these induced changes in concentration to be recorded with the sensitivity and selectivity of FSCV. A negative potential step applied at the generator produces a transient local pH shift at the collector. The generator-induced pH signal is detected using FSCV at the collector and correlated to absolute solution pH by postcalibration of the anodic peak position. In addition, in oxygenated solutions a negative potential step at the generator produces hydrogen peroxide by reducing oxygen. Hydrogen peroxide is detected with FSCV at the collector electrode, and the magnitude of the oxidative peak is proportional to absolute oxygen concentrations. Oxygen interference on the pH signal is minimal and can be accounted for with a postcalibration.

Which blood oxygen can sensitively indicate shock severity?

NASA Astrophysics Data System (ADS)

Pan, Boan; Li, Kai; Gao, Yuan; Ruan, Zhengshang; Li, Ting

2016-03-01

Clinical shock-monitoring mainly depends on measuring oxygen saturations from SVC blood samples invasively. The golden standard indicator is the central internal jugular vein oxygenation (SjvO2). Using near-infrared spectroscopy (NIRS) also can monitor shock in some papers published, but there is no discussion about which oxygen saturation (cerebral venous oxygen saturation, ScvO2; tissue oxygen saturation of internal jugular area; tissue oxygen saturation of extremities areas) can monitor shock patient more sensitively and accurately. The purpose of this paper is to examine which one is most effective. In order to discuss the problem, we continuously detected 56 critical patients who may be into shock state using NIRS oximeter at prefrontal, internal jugular vein area and forearm, and chose 24 patients who were into shock and then out of shock from the 56 critical patients. Combined with the patients' condition, the pulse oxygen saturation is most sensitively to monitoring shock than the others, and the internal jugular vein area oxygen saturation is most effective.

Measuring vertical oxygen profiles in the hyporheic zone using planar optodes

NASA Astrophysics Data System (ADS)

Vieweg, M.; Fleckenstein, J. H.; Schmidt, C.

2012-04-01

On of the key parameters, controlling biogeochemical reactions in the hyporheic zone (HZ) is the distribution of oxygen. A reliable measurement of the vertical oxygen distribution is an important tool to understand the dynamic fluctuations of the aerobic zone within the HZ. With repeated measurements of continuous profiles, mixing of surface water and groundwater as well as the consumption of oxygen can be evaluated. We present a novel approach for the in situ measurements of vertical oxygen distribution in the riverbed using a planar optode. The luminescence based optode measurement enables a non invasive measurement without consumption of oxygen, no creation of preferential flow paths and only minimal disturbance of the flow field. Possible atmospheric contamination by pumping pore water into a vessel can be avoided and the readings are independent of flow velocity. A self manufactured planar optode is wrapped around an acrylic tube and installed in the riverbed. The measurement is performed by vertically moving a profiler-piston inside the acrylic tube. The piston holds a robust polymer optical fibre which emits a modulated light signal through the acrylic glass to the optode-foil and transmits the induced luminescence signal back to a commercially available trace oxygen meter. Temperature compensation is accomplished using a depth-oriented temperature probe nearby and processing the raw data within a Matlab script. Robust and unbiased oxygen profiles are obtained by averaging multiple consecutive measurements. To ensure a constant velocity of the profiler for replicating the exact measuring depths, an electric motor device is used. First results at our test site show a variable oxygen profile down to 40 cm depth which is strongly influenced by stream level and upwelling groundwater conditions. The measured oxygen profiles will serve as input parameter for a 3D solute transport and chemical reaction subsurface model of the HZ.

Intramyocardial oxygen transport by quantitative diffuse reflectance spectroscopy in calves

NASA Astrophysics Data System (ADS)

Lindbergh, Tobias; Larsson, Marcus; Szabó, Zoltán; Casimir-Ahn, Henrik; Strömberg, Tomas

2010-03-01

Intramyocardial oxygen transport was assessed during open-chest surgery in calves by diffuse reflectance spectroscopy using a small intramuscular fiber-optic probe. The sum of hemo- and myoglobin tissue fraction and oxygen saturation, the tissue fraction and oxidation of cytochrome aa3, and the tissue fraction of methemoglobin were estimated using a calibrated empirical light transport model. Increasing the oxygen content in the inhaled gas, 21%-50%-100%, in five calves (group A) gave an increasing oxygen saturation of 19+/-4%, 24+/-5%, and 28+/-8% (p<0.001, ANOVA repeated measures design) and mean tissue fractions of 1.6% (cytochrome aa3) and 1.1% (hemo- and myoglobin). Cardiac arrest in two calves gave an oxygen saturation lower than 5%. In two calves (group B), a left ventricular assistive device (LVAD pump) was implanted. Oxygen saturation in group B animals increased with LVAD pump speed (p<0.001, ANOVA) and with oxygen content in inhaled gas (p<0.001, ANOVA). The cytochrome aa3 oxidation level was above 96% in both group A and group B calves, including the two cases involving cardiac arrest. In conclusion, the estimated tissue fractions and oxygenation/oxidation levels of the myocardial chromophores during respiratory and hemodynamic provocations were in agreement with previously presented results, demonstrating the potential of the method.

Oxygen, pH, and mitochondrial oxidative phosphorylation.

PubMed

Wilson, David F; Harrison, David K; Vinogradov, Sergei A

2012-12-15

The oxygen dependence of mitochondrial oxidative phosphorylation was measured in suspensions of isolated rat liver mitochondria using recently developed methods for measuring oxygen and cytochrome c reduction. Cytochrome-c oxidase (energy conservation site 3) activity of the mitochondrial respiratory chain was measured using an artificial electron donor (N,N,N',N'-tetramethyl-p-phenylenediamine) and ascorbate to directly reduce the cytochrome c, bypassing sites 1 and 2. For mitochondrial suspensions with added ATP, metabolic conditions approximating those in intact cells and decreasing oxygen pressure both increased reduction of cytochrome c and decreased respiratory rate. The kinetic parameters [K(M) and maximal rate (V(M))] for oxygen were determined from the respiratory rates calculated for 100% reduction of cytochrome c. At 22°C, the K(M) for oxygen is near 3 Torr (5 μM), 12 Torr (22 μM), and 18 Torr (32 μM) at pH 6.9, 7.4, and 7.9, respectively, and V(M) corresponds to a turnover number for cytochrome c at 100% reduction of near 80/s and is independent of pH. Uncoupling oxidative phosphorylation increased the respiratory rate at saturating oxygen pressures by twofold and decreased the K(M) for oxygen to <2 Torr at all tested pH values. Mitochondrial oxidative phosphorylation is an important oxygen sensor for regulation of metabolism, nutrient delivery to tissues, and cardiopulmonary function. The decrease in K(M) for oxygen with acidification of the cellular environment impacts many tissue functions and may give transformed cells a significant survival advantage over normal cells at low-pH, oxygen-limited environment in growing tumors.

Toe blood pressure and leg muscle oxygenation with body posture.

PubMed

Rosales-Velderrain, Armando; Cardno, Michael; Mateus, Jaime; Kumar, Ravindra; Schlabs, Thomas; Hargens, Alan R

2011-05-01

In 1980 Katkov and Chestukhin measured blood pressures and oxygenation invasively at various body tilt angles at different locations on the body, including the foot. To our knowledge, such measurements have not been performed noninvasively. Therefore, the purpose of this study was to measure toe blood pressure (TBP) and lower limb muscle oxygenation noninvasively at various body tilt angles, and to assess the use of a Finometer for noninvasive TBP measurements. Our noninvasive results are compared with those performed by Katkov and Chestukhin. We hypothesized that: 1) the Finometer provides a noninvasive measurement of TBP at different tilt angles; and 2) muscle oxygenation is highest with 0 and -6 degrees, and decreases with increased head-up tilt (HUT). There were 10 subjects who were exposed to different body tilt angles (-6, 0, 10, 30, 70, and 90 degrees). At each angle we measured TBP noninvasively with a Finometer and muscle tissue oxygenation by near infrared spectroscopy. We found a strong correlation between TBP using the Finometer and TBP predicted by adding the hydrostatic component due to body tilt to the standard arm blood pressure measurement. At 10, 30, 70, and 90 degrees both TBP and tissue oxygenation were significantly different from the 0 degree (supine) level. Oxygenation decreased and TBP increased with higher HUT angles. No differences were observed in TBP or oxygenation between -6 and 0 degree. The Finometer accurately measures TBP noninvasively with body tilt. Also, muscle oxygenation is highest at small HUT angles and decreases with increased HUT.

Measurement of tissue viscoelasticity with ultrasound

NASA Astrophysics Data System (ADS)

Greenleaf, J. F.; Alizad, A.

2017-02-01

Tissue properties such as elasticity and viscosity have been shown to be related to such tissue conditions as contraction, edema, fibrosis, and fat content among others. Magnetic Resonance Elastography has shown outstanding ability to measure the elasticity and in some cases the viscosity of tissues, especially in the liver, providing the ability to stage fibrotic liver disease similarly to biopsy. We discuss ultrasound methods of measuring elasticity and viscosity in tissues. Many of these methods are becoming widely available in the extant ultrasound machines distributed throughout the world. Some of the methods to be discussed are in the developmental stage. The advantages of the ultrasound methods are that the imaging instruments are widely available and that many of the viscoelastic measurements can be made during a short addition to the normal ultrasound examination time. In addition, the measurements can be made by ultrasound repetitively and quickly allowing evaluation of dynamic physiologic function in circumstances such as muscle contraction or artery relaxation. Measurement of viscoelastic tissue mechanical properties will become a consistent part of clinical ultrasound examinations in our opinion.

Single-cell measurement of red blood cell oxygen affinity

PubMed Central

Di Caprio, Giuseppe; Stokes, Chris; Higgins, John M.; Schonbrun, Ethan

2015-01-01

Oxygen is transported throughout the body by hemoglobin (Hb) in red blood cells (RBCs). Although the oxygen affinity of blood is well-understood and routinely assessed in patients by pulse oximetry, variability at the single-cell level has not been previously measured. In contrast, single-cell measurements of RBC volume and Hb concentration are taken millions of times per day by clinical hematology analyzers, and they are important factors in determining the health of the hematologic system. To better understand the variability and determinants of oxygen affinity on a cellular level, we have developed a system that quantifies the oxygen saturation, cell volume, and Hb concentration for individual RBCs in high throughput. We find that the variability in single-cell saturation peaks at an oxygen partial pressure of 2.9%, which corresponds to the maximum slope of the oxygen–Hb dissociation curve. In addition, single-cell oxygen affinity is positively correlated with Hb concentration but independent of osmolarity, which suggests variation in the Hb to 2,3-diphosphoglycerate (2–3 DPG) ratio on a cellular level. By quantifying the functional behavior of a cellular population, our system adds a dimension to blood cell analysis and other measurements of single-cell variability. PMID:26216973

Effects of positive end-expiratory pressure on brain tissue oxygen pressure of severe traumatic brain injury patients with acute respiratory distress syndrome: A pilot study.

PubMed

Nemer, Sérgio Nogueira; Caldeira, Jefferson B; Santos, Ricardo G; Guimarães, Bruno L; Garcia, João Márcio; Prado, Darwin; Silva, Ricardo T; Azeredo, Leandro M; Faria, Eduardo R; Souza, Paulo Cesar P

2015-12-01

To verify whether high positive end-expiratory pressure levels can increase brain tissue oxygen pressure, and also their effects on pulse oxygen saturation, intracranial pressure, and cerebral perfusion pressure. Twenty traumatic brain injury patients with acute respiratory distress syndrome were submitted to positive end-expiratory pressure levels of 5, 10, and 15 cm H2O progressively. The 3 positive end-expiratory pressure levels were used during 20 minutes for each one, whereas brain tissue oxygen pressure, oxygen saturation, intracranial pressure, and cerebral perfusion pressure were recorded. Brain tissue oxygen pressure and oxygen saturation increased significantly with increasing positive end-expiratory pressure from 5 to 10 and from 10 to 15 cm H2O (P=.0001 and P=.0001 respectively). Intracranial pressure and cerebral perfusion pressure did not differ significantly with increasing positive end-expiratory pressure from 5 to 10 and from 10 to 15 cm H2O (P=.16 and P=.79 respectively). High positive end-expiratory pressure levels increased brain tissue oxygen pressure and oxygen saturation, without increase in intracranial pressure or decrease in cerebral perfusion pressure. High positive end-expiratory pressure levels can be used in severe traumatic brain injury patients with acute respiratory distress syndrome as a safe alternative to improve brain oxygenation. Copyright © 2015 Elsevier Inc. All rights reserved.

Techniques for Measuring Low Earth Orbital Atomic Oxygen Erosion of Polymers

NASA Technical Reports Server (NTRS)

deGroh, Kim K.; Banks, Bruce A.; Demko, Rikako

2002-01-01

Polymers such as polyimide Kapton and Teflon FEP (fluorinated ethylene propylene) are commonly used spacecraft materials due to their desirable properties such as flexibility, low density, and in the case of FEP, a low solar absorptance and high thermal emittance. Polymers on the exterior of spacecraft in the low Earth orbit (LEO) environment are exposed to energetic atomic oxygen. Atomic oxygen reaction with polymers causes erosion, which is a threat to spacecraft durability. It is therefore important to understand the atomic oxygen erosion yield (E, the volume loss per incident oxygen atom) of polymers being considered in spacecraft design. The most common technique for determining E is through mass loss measurements. For limited duration exposure experiments, such as shuttle experiments, where the atomic oxygen fluence is often so low that mass loss measurements can not produce acceptable uncertainties, recession measurements based on atomic force microscopy analyses can be used. Equally necessary to knowing the mass loss or recession depth for determining the erosion yield of polymers is the knowledge of the atomic oxygen fluence that the polymers were exposed to in space. This paper discusses the procedures and relevant issues for mass loss and recession depth measurements for passive atomic oxygen erosion yield characterization of polymers, along with techniques for active atomic oxygen fluence and erosion characterization. One active atomic oxygen erosion technique discussed is a new technique based on optical measurements. Details including the use of both semi-transparent and opaque polymers for active erosion measurement are reviewed.

ASRDI oxygen technology survey. Volume 6: Flow measurement instrumentation

NASA Technical Reports Server (NTRS)

Mann, D. B.

1974-01-01

A summary is provided of information available on liquid and gaseous oxygen flowmetering including an evaluation of commercial meters. The instrument types, physical principles of measurement, and performance characteristics are described. Problems concerning flow measurements of less than plus or minus two percent uncertainty are reviewed. Recommendations concerning work on flow reference systems, the use of surrogate fluids, and standard tests for oxygen flow measurements are also presented.

Development and Validation of Noninvasive Magnetic Resonance Relaxometry for the In Vivo Assessment of Tissue-Engineered Graft Oxygenation

PubMed Central

Einstein, Samuel A.; Weegman, Bradley P.; Firpo, Meri T.; Papas, Klearchos K.

2016-01-01

Techniques to monitor the oxygen partial pressure (pO2) within implanted tissue-engineered grafts (TEGs) are critically necessary for TEG development, but current methods are invasive and inaccurate. In this study, we developed an accurate and noninvasive technique to monitor TEG pO2 utilizing proton (1H) or fluorine (19F) magnetic resonance spectroscopy (MRS) relaxometry. The value of the spin-lattice relaxation rate constant (R1) of some biocompatible compounds is sensitive to dissolved oxygen (and temperature), while insensitive to other external factors. Through this physical mechanism, MRS can measure the pO2 of implanted TEGs. We evaluated six potential MRS pO2 probes and measured their oxygen and temperature sensitivities and their intrinsic R1 values at 16.4 T. Acellular TEGs were constructed by emulsifying porcine plasma with perfluoro-15-crown-5-ether, injecting the emulsion into a macroencapsulation device, and cross-linking the plasma with a thrombin solution. A multiparametric calibration equation containing R1, pO2, and temperature was empirically generated from MRS data and validated with fiber optic (FO) probes in vitro. TEGs were then implanted in a dorsal subcutaneous pocket in a murine model and evaluated with MRS up to 29 days postimplantation. R1 measurements from the TEGs were converted to pO2 values using the established calibration equation and these in vivo pO2 measurements were simultaneously validated with FO probes. Additionally, MRS was used to detect increased pO2 within implanted TEGs that received supplemental oxygen delivery. Finally, based on a comparison of our MRS data with previously reported data, ultra-high-field (16.4 T) is shown to have an advantage for measuring hypoxia with 19F MRS. Results from this study show MRS relaxometry to be a precise, accurate, and noninvasive technique to monitor TEG pO2 in vitro and in vivo. PMID:27758135

Development and Validation of Noninvasive Magnetic Resonance Relaxometry for the In Vivo Assessment of Tissue-Engineered Graft Oxygenation.

PubMed

Einstein, Samuel A; Weegman, Bradley P; Firpo, Meri T; Papas, Klearchos K; Garwood, Michael

2016-11-01

Techniques to monitor the oxygen partial pressure (pO 2 ) within implanted tissue-engineered grafts (TEGs) are critically necessary for TEG development, but current methods are invasive and inaccurate. In this study, we developed an accurate and noninvasive technique to monitor TEG pO 2 utilizing proton ( 1 H) or fluorine ( 19 F) magnetic resonance spectroscopy (MRS) relaxometry. The value of the spin-lattice relaxation rate constant (R 1 ) of some biocompatible compounds is sensitive to dissolved oxygen (and temperature), while insensitive to other external factors. Through this physical mechanism, MRS can measure the pO 2 of implanted TEGs. We evaluated six potential MRS pO 2 probes and measured their oxygen and temperature sensitivities and their intrinsic R 1 values at 16.4 T. Acellular TEGs were constructed by emulsifying porcine plasma with perfluoro-15-crown-5-ether, injecting the emulsion into a macroencapsulation device, and cross-linking the plasma with a thrombin solution. A multiparametric calibration equation containing R 1 , pO 2 , and temperature was empirically generated from MRS data and validated with fiber optic (FO) probes in vitro. TEGs were then implanted in a dorsal subcutaneous pocket in a murine model and evaluated with MRS up to 29 days postimplantation. R 1 measurements from the TEGs were converted to pO 2 values using the established calibration equation and these in vivo pO 2 measurements were simultaneously validated with FO probes. Additionally, MRS was used to detect increased pO 2 within implanted TEGs that received supplemental oxygen delivery. Finally, based on a comparison of our MRS data with previously reported data, ultra-high-field (16.4 T) is shown to have an advantage for measuring hypoxia with 19 F MRS. Results from this study show MRS relaxometry to be a precise, accurate, and noninvasive technique to monitor TEG pO 2 in vitro and in vivo.

Measurement and Control of Oxygen Partial Pressure in an Electrostatic Levitator

NASA Technical Reports Server (NTRS)

SanSoucie, Michael P.; Rogers, Jan R.

2014-01-01

Recently the NASA Marshall Space Flight Center electrostatic levitation (ESL) laboratory has been upgraded to include an oxygen control system. This system allows the oxygen partial pressure within the vacuum chamber to be measured and controlled, at elevated temperatures, theoretically in the range from 10(exp -36) to 10(exp 0) bar. The role of active surface agents in liquid metals is fairly well known; however, published surface tension data typically has large scatter, which has been hypothesized to be caused by the presence of oxygen. The surface tension of metals is affected by even a small amount of adsorption of oxygen. It has even been shown that oxygen partial pressures may need to be as low as 10(exp -24) bar to avoid oxidation. While electrostatic levitation is done under high vacuum, oxide films or dissolved oxygen may have significant effects on materials properties, such as surface tension and viscosity. Therefore, the ability to measure and control the oxygen partial pressure within the chamber is highly desirable. The oxygen control system installed at MSFC contains a potentiometric sensor, which measures the oxygen partial pressure, and an oxygen ion pump. In the pump, a pulse-width modulated electric current is applied to yttrium-stabilized zirconia, resulting in oxygen transfer into or out of the system. Also part of the system is a control unit, which consists of temperature controllers for the sensor and pump, PID-based current loop for the ion pump, and a control algorithm. This system can be used to study the effects of oxygen on the thermophysical properties of metals, ceramics, glasses, and alloys. It can also be used to provide more accurate measurements by processing the samples at very low oxygen partial pressures. The oxygen control system will be explained in more detail and an overview of its use and limitations in an electrostatic levitator will be described. Some preliminary measurements have been made, and the results to date will

Cerebral Microcirculation and Oxygen Tension in the Human Secondary Cortex

PubMed Central

Linninger, A. A.; Gould, I. G.; Marinnan, T.; Hsu, C.-Y.; Chojecki, M.; Alaraj, A.

2013-01-01

The three-dimensional spatial arrangement of the cortical microcirculatory system is critical for understanding oxygen exchange between blood vessels and brain cells. A three-dimensional computer model of a 3 × 3 × 3 mm3 subsection of the human secondary cortex was constructed to quantify oxygen advection in the microcirculation, tissue oxygen perfusion, and consumption in the human cortex. This computer model accounts for all arterial, capillary and venous blood vessels of the cerebral microvascular bed as well as brain tissue occupying the extravascular space. Microvessels were assembled with optimization algorithms emulating angiogenic growth; a realistic capillary bed was built with space filling procedures. The extravascular tissue was modeled as a porous medium supplied with oxygen by advection–diffusion to match normal metabolic oxygen demand. The resulting synthetic computer generated network matches prior measured morphometrics and fractal patterns of the cortical microvasculature. This morphologically accurate, physiologically consistent, multi-scale computer network of the cerebral microcirculation predicts the oxygen exchange of cortical blood vessels with the surrounding gray matter. Oxygen tension subject to blood pressure and flow conditions were computed and validated for the blood as well as brain tissue. Oxygen gradients along arterioles, capillaries and veins agreed with in vivo trends observed recently in imaging studies within experimental tolerances and uncertainty. PMID:23842693

Measurement of the oxygen mass transfer through the air-water interface.

PubMed

Mölder, Erik; Mashirin, Alelxei; Tenno, Toomas

2005-01-01

Gas mass transfer through the liquid-gas interface has enormous importance in various natural and industrial processes. Surfactants or insoluble compounds adsorbed onto an interface will inhibit the gas mass transfer through the liquid-gas surface. This study presents a technique for measuring the oxygen mass transfer through the air-water interface. Experimental data obtained with the measuring device were incorporated into a novel mathematical model, which allowed one to calculate diffusion conduction of liquid surface layer and oxygen mass transfer coefficient in the liquid surface layer. A special measurement cell was constructed. The most important part of the measurement cell is a chamber containing the electrochemical oxygen sensor inside it. Gas exchange between the volume of the chamber and the external environment takes place only through the investigated surface layer. Investigated liquid was deoxygenated, which triggers the oxygen mass transfer from the chamber through the liquid-air interface into the liquid phase. The decrease of oxygen concentration in the cell during time was measured. By using this data it is possible to calculate diffusional parameters of the water surface layer. Diffusion conduction of oxygen through the air-water surface layer of selected wastewaters was measured. The diffusion conduction of different wastewaters was about 3 to 6 times less than in the unpolluted water surface. It was observed that the dilution of wastewater does not have a significant impact on the oxygen diffusion conduction through the wastewater surface layer. This fact can be explained with the presence of the compounds with high surface activity in the wastewater. Surfactants achieved a maximum adsorption and, accordingly, the maximum decrease of oxygen permeability already at a very low concentration of surfactants in the solution. Oxygen mass transfer coefficient of the surface layer of the water is found to be Ds/ls = 0.13 x 10(-3) x cm/s. A simple

NIRS-Derived Tissue Oxygen Saturation and Hydrogen Ion Concentration Following Bed Rest

NASA Technical Reports Server (NTRS)

Lee, S. M. C.; Everett, M. E.; Crowell, J. B.; Westby, C. M.; Soller, B. R.

2010-01-01

Long-term bed rest (BR), a model of spaceflight, results in a decrease in aerobic capacity and altered submaximal exercise responses. The strongest BR-induced effects on exercise appear to be centrally-mediated, but longer BR durations may result in peripheral adaptations (e.g., decreased mitochondrial and capillary density) which are likely to influence exercise responses. PURPOSE: To measure tissue oxygen saturation (SO2) and hydrogen ion concentration ([H+]) in the vastus lateralis (VL) using near infrared spectroscopy (NIRS) during cycle ergometry before and after . 30 d of BR. METHODS: Eight subjects performed a graded exercise test on a cycle ergometer to volitional fatigue 7 d before (pre-BR) and at the end or 1 day after BR (post-BR). NIRS spectra were collected from a sensor adhered to the skin overlying the VL. Oxygen consumption (VO2) was measured by open circuit spirometry. Blood volume (BV) was measured before and after BR using the carbon monoxide rebreathing technique. Changes in pre- and post-BR SO2 and [H+] data were compared using mixed model analyses. BV and peak exercise data were compared using paired t-tests. RESULTS: BV (pre-BR: 4.3+/-0.3, post-BR: 3.7+/-0.2 L, mean+/-SE, p=.01) and peak VO2 (pre-BR: 1.98+/-0.24, post-BR: 1.48 +/-0.21 L/min, p<.01) were reduced after BR. As expected, SO2 decreased with exercise before and after BR. However, SO2 was lower post compared with pre-BR throughout exercise, including at peak exercise (pre-BR: 50+/-3, post-BR: 43+/-4%, p=.01). After BR, [H+] was higher at the start of exercise and did not increase at the same rate as pre-BR. Peak [H+] was not different from pre to post-BR (pre-BR: 36+/-2; post-BR: 38+/-2 nmol/L). CONCLUSIONS: Lower SO2 during exercise suggests that oxygen extraction in the VL is higher after BR, perhaps due to lower circulating blood volume. The higher [H+] after BR suggests a greater reliance upon glycolysis during submaximal exercise, although [H+] at peak exercise was unchanged

The estimation of recovery time of calf muscle oxygen saturation during exercise by using functional near infrared spectroscopy

NASA Astrophysics Data System (ADS)

Ansari, M. A.; Shojaeifar, M.; Mohajerani, E.

2014-08-01

Several methods of near infrared spectroscopy such as functional near infrared spectroscopy (fNIRS) and pulse oximetry have been applied for monitoring of tissue oxygenation or arterial oxygen saturation. Some vascular diseases can be diagnosed through measurements of tissue oxygenation. In this study, the temporal variation of oxygenation of calf muscle after exercise is studied by fNIRS. First, the accuracy of a low-cost fNIRS system is studied by measuring the oxygenation of a lipid phantom. Moreover, in-vivo study is performed to evaluate the precision of this system. Then, the variation of muscle oxygenation of four persons during exercise is measured and also the recovery time after walking/running is measured by this fNIRS system.

Monitoring in microvascular tissue transfer by measurement of oxygen partial pressure: four years experience with 125 microsurgical transplants.

PubMed

Jonas, René; Schaal, Thomas; Krimmel, Michael; Gülicher, Dirk; Reinert, Siegmar; Hoffmann, Jürgen

2013-06-01

In a prospective study, the characteristics and benefit of an invasive measurement of oxygen partial pressure (pO(2)) with the aid of a polarographic sensor were investigated in 125 microsurgical reconstructions of the head and neck area over a period of 45 months. Measurements were performed over 96 h in eight different types of microsurgically revascularized flaps for extra- and intraoral reconstructions and were evaluated separately for each flap type. Of 125 reconstructions the system indicated malperfusion in 18 cases. Salvage surgery was performed in 17 cases due to venous thrombosis (6 cases), arterial thrombosis (3 cases), a combination of arterial and venous thrombosis (2 cases), rheological problems (3 cases), venous insufficiency by hematoma (2 cases) and kinking of vessels (1 case). In 10 cases salvage surgery was successful, 7 flaps were lost despite salvage surgery. In all these cases, the polarographic probe indicated the necessity of salvage surgery correctly. After 96 h no malperfusion was seen. Postoperatively, a common and characteristic development of the oxygen partial pressure in different types of flaps was seen. Initially, a clear increase of pO(2) could be measured. During 96 h, a slow decrease of pO(2) was observed. In conclusion polarographic measurement of pO(2) can be an excellent apparative supplement for the postoperative clinical control of microsurgically revascularized transplants. In buried flaps, this technique represents the only reliable method for transplant monitoring. Copyright © 2012 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

Lack of effect of moderate hypothermia on brain tissue oxygenation after acute intracranial hypertension in pigs.

PubMed

Bao, Ying-Hui; Liang, Yu-Min; Gao, Guo-Yi; Jiang, Ji-Yao

2010-02-01

In this study, we explored the effect of moderate hypothermia on brain tissue oxygenation following acute intracranial hypertension in micropigs. Twenty healthy juvenile micropigs weighting 4-6 kg were randomized into two groups: a normothermia group (n = 10) and a moderate hypothermia group (n = 10). The animals were intravenously anesthetized with propofol (4 mg/kg), an endotracheal tube was inserted, and mechanical ventilation was begun. Autologous arterial blood was injected into the left frontal lobe to establish acute intracerebral hematoma and intracranial hypertension (intracranial pressure [ICP] >40 mm Hg) in all animals. Cooling was initiated at 30 min after injection of the blood, and was achieved via the use of an ice bath and ice packs. In the hypothermia group, the brain temperature decreased to 33-34 degrees C. Brain temperature was maintained at 37 +/- 0.3 degrees C in the normothermia group. The ICP, cerebral perfusion pressure (CPP), brain tissue oxygen pressure (P(br)O(2)), brain tissue carbon dioxide pressure (P(br)CO(2)), and brain tissue pH value (pH(br)) were continuously monitored for 3 h in all animals. Compared to normothermia group, ICP values significantly decreased and CPP markedly improved in the hypothermia group (p < 0.05). Further, pH(br) also markedly increased and P(br)CO(2) decreased significantly in the hypothermia group (p < 0.05). However, P(br)O(2) did not statistically significantly improve in the hypothermia group (p > 0.05). In sum, moderate hypothermia significantly decreased ICP, reduced P(br)CO(2), and increased pH(br) values, but did not improve cerebral oxygenation following acute intracranial hypertension.

Model-based cell number quantification using online single-oxygen sensor data for tissue engineering perfusion bioreactors.

PubMed

Lambrechts, T; Papantoniou, I; Sonnaert, M; Schrooten, J; Aerts, J-M

2014-10-01

Online and non-invasive quantification of critical tissue engineering (TE) construct quality attributes in TE bioreactors is indispensable for the cost-effective up-scaling and automation of cellular construct manufacturing. However, appropriate monitoring techniques for cellular constructs in bioreactors are still lacking. This study presents a generic and robust approach to determine cell number and metabolic activity of cell-based TE constructs in perfusion bioreactors based on single oxygen sensor data in dynamic perfusion conditions. A data-based mechanistic modeling technique was used that is able to correlate the number of cells within the scaffold (R(2)  = 0.80) and the metabolic activity of the cells (R(2)  = 0.82) to the dynamics of the oxygen response to step changes in the perfusion rate. This generic non-destructive measurement technique is effective for a large range of cells, from as low as 1.0 × 10(5) cells to potentially multiple millions of cells, and can open-up new possibilities for effective bioprocess monitoring. © 2014 Wiley Periodicals, Inc.

Oxygen Pickup Ions Measured by MAVEN Outside the Martian Bow Shock

NASA Astrophysics Data System (ADS)

Rahmati, A.; Cravens, T.; Larson, D. E.; Lillis, R. J.; Dunn, P.; Halekas, J. S.; Connerney, J. E. P.; Eparvier, F. G.; Thiemann, E.; Mitchell, D. L.; Jakosky, B. M.

2015-12-01

The MAVEN (Mars Atmosphere and Volatile EvolutioN) spacecraft entered orbit around Mars on September 21, 2014 and has since been detecting energetic oxygen pickup ions by its SEP (Solar Energetic Particles) and SWIA (Solar Wind Ion Analyzer) instruments. The oxygen pickup ions detected outside the Martian bowshock and in the upstream solar wind are associated with the extended hot oxygen exosphere of Mars, which is created mainly by the dissociative recombination of molecular oxygen ions with electrons in the ionosphere. We use analytic solutions to the equations of motion of pickup ions moving in the undisturbed upstream solar wind magnetic and motional electric fields and calculate the flux of oxygen pickup ions at the location of MAVEN. Our model calculates the ionization rate of oxygen atoms in the exosphere based on the hot oxygen densities predicted by Rahmati et al. (2014), and the sources of ionization include photo-ionization, charge exchange, and electron impact ionization. The photo-ionization frequency is calculated using the FISM (Flare Irradiance Spectral Model) solar flux model, based on MAVEN EUVM (Extreme Ultra-Violet Monitor) measurements. The frequency of charge exchange between a solar wind proton and an oxygen atom is calculated using MAVEN SWIA solar wind proton flux measurements, and the electron impact ionization frequency is calculated based on MAVEN SWEA (Solar Wind Electron Analyzer) solar wind electron flux measurements. The solar wind magnetic field used in the model is from the measurements taken by MAVEN MAG (magnetometer) in the upstream solar wind. The good agreement between our predicted pickup oxygen fluxes and the MAVEN SEP and SWIA measured ones confirms detection of oxygen pickup ions and these model-data comparisons can be used to constrain models of hot oxygen densities and photochemical escape flux.

An algorithm for sensing venous oxygenation using ultrasound-modulated light enhanced by microbubbles

NASA Astrophysics Data System (ADS)

Honeysett, Jack E.; Stride, Eleanor; Deng, Jing; Leung, Terence S.

2012-02-01

Near-infrared spectroscopy (NIRS) can provide an estimate of the mean oxygen saturation in tissue. This technique is limited by optical scattering, which reduces the spatial resolution of the measurement, and by absorption, which makes the measurement insensitive to oxygenation changes in larger deep blood vessels relative to that in the superficial tissue. Acousto-optic (AO) techniques which combine focused ultrasound (US) with diffuse light have been shown to improve the spatial resolution as a result of US-modulation of the light signal, however this technique still suffers from low signal-to-noise when detecting a signal from regions of high optical absorption. Combining an US contrast agent with this hybrid technique has been proposed to amplify an AO signal. Microbubbles are a clinical contrast agent used in diagnostic US for their ability to resonate in a sound field: in this work we also make use of their optical scattering properties (modelled using Mie theory). A perturbation Monte Carlo (pMC) model of light transport in a highly absorbing blood vessel containing microbubbles surrounded by tissue is used to calculate the AO signal detected on the top surface of the tissue. An algorithm based on the modified Beer-Lambert law is derived which expresses intravenous oxygen saturation in terms of an AO signal. This is used to determine the oxygen saturation in the blood vessel from a dual wavelength microbubble-contrast AO measurement. Applying this algorithm to the simulation data shows that the venous oxygen saturation is accurately recovered, and this measurement is robust to changes in the oxygenation of the superficial tissue layer.

ASRDI oxygen technology survey. Volume 8: Pressure measurement

NASA Technical Reports Server (NTRS)

Arvidson, J. M.; Brennan, J. A.

1975-01-01

Pressure transducers and their current uses with gaseous or liquid oxygen are reviewed. All transducer types such as strain gage, capacitance, potentiometric, piezoelectric, etc., are included. Topics covered include: cryogenic pressure measurement; material compatibility with gaseous and liquid oxygen; cleaning procedures; pressure tap connections; transducer types and descriptions; and calibration techniques.

Cerebral blood oxygenation measurements in neonates with optoacoustic technique

NASA Astrophysics Data System (ADS)

Herrmann, Stephen; Petrov, Irene Y.; Petrov, Yuriy; Richardson, C. Joan; Fonseca, Rafael A.; Prough, Donald S.; Esenaliev, Rinat O.

2017-03-01

Cerebral hypoxia is a major contributor to neonatal/infant mortality and morbidity including severe neurological complications such as mental retardation, cerebral palsy, motor impairment, and epilepsy. Currently, no technology is capable of accurate monitoring of neonatal cerebral oxygenation. We proposed to use optoacoustics for this application by probing the superior sagittal sinus (SSS), a large central cerebral vein. We developed and built a multi-wavelength, optical parametric oscillator (OPO) and laser diode optoacoustic systems for measurement of SSS blood oxygenation in the reflection mode through open anterior or posterior fontanelles and in the transmission mode through the skull in the occipital area. In this paper we present results of initial tests of the laser diode system for neonatal cerebral oxygenation measurements. First, the system was tested in phantoms simulating neonatal SSS. Then, using the data obtained in the phantoms, we optimized the system's hardware and software and tested it in neonates admitted in the Neonatal Intensive Care Unit. The laser diode system was capable of detecting SSS signals in the reflection mode through the open anterior and posterior fontanelles as well as in the transmission mode through the skull with high signal-to-noise ratio. Using the signals measured at different wavelengths and algorithms developed for oxygenation measurements, the laser diode system provided real-time, continuous oxygenation monitoring with high precision at all these locations.

Mapping oxygen concentration in the awake mouse brain.

PubMed

Lyons, Declan G; Parpaleix, Alexandre; Roche, Morgane; Charpak, Serge

2016-02-02

Although critical for brain function, the physiological values of cerebral oxygen concentration have remained elusive because high-resolution measurements have only been performed during anesthesia, which affects two major parameters modulating tissue oxygenation: neuronal activity and blood flow. Using measurements of capillary erythrocyte-associated transients, fluctuations of oxygen partial pressure (Po2) associated with individual erythrocytes, to infer Po2 in the nearby neuropil, we report the first non-invasive micron-scale mapping of cerebral Po2 in awake, resting mice. Interstitial Po2 has similar values in the olfactory bulb glomerular layer and the somatosensory cortex, whereas there are large capillary hematocrit and erythrocyte flux differences. Awake tissue Po2 is about half that under isoflurane anesthesia, and within the cortex, vascular and interstitial Po2 values display layer-specific differences which dramatically contrast with those recorded under anesthesia. Our findings emphasize the importance of measuring energy parameters non-invasively in physiological conditions to precisely quantify and model brain metabolism.

Optical assessment of intravascular and intracellular parameters related to tissue viability

NASA Astrophysics Data System (ADS)

Mayevsky, Avraham; Sherman, Efrat; Cohen-Kashi, Meir; Dekel, Nava; Pewzner, Eliyahu

2007-02-01

Tissue viability represents the balance between O II supply and demand. In our previous paper (Mayevsky et al; Proc.SPIE 6083 : z1-z10, 2006) the HbO II was added to the multiparametric tissue spectroscope (Mayevsky et al J.Biomedical Optics 9:1028-1045,2004). This parameter provides relative values of microcirculatory blood oxygenation (MC-HbO II) evaluated by the 2 wavelength reflectometry principle. The advantage of this approach as compared to pulse oximetry is that the measurement is not dependent of the existence of the pulse of the heart. Also in the MC-HbO II the information is collected from small vessels providing O II to the mitochondria as compared to the pulse oximeter indicating blood oxygenation by the respiratory and cardiovascular systems. In the present study we compared the level of blood oxygenation measured by the pulse oximeter to that measured by the CritiView in the brain exposed to various systemic and localized perturbations of O II supply or demand. We exposed gerbils to anoxia, hypoxia, ischemia and terminal anoxia. In addition we measured mitochondrial NADH (surface fluorometry), tissue reflectance, tissue blood flow (laser Doppler flowmetry) from the same site of MC-HbO II measurement. A clear connection was found between the two blood oxygenation parameters only when systemic perturbations were used (anoxia, hypoxia and terminal anoxia). Under local events (ischemia) the MC-HbO II was responsive while the systemic oxygenation was unchanged. We concluded that MC-HbO II has a significant value in interpretation of tissue energy metabolism under pathophysiological conditions.

Measuring hemoglobin amount and oxygen saturation of skin with advancing age

NASA Astrophysics Data System (ADS)

Watanabe, Shumpei; Yamamoto, Satoshi; Yamauchi, Midori; Tsumura, Norimichi; Ogawa-Ochiai, Keiko; Akiba, Tetsuo

2012-03-01

We measured the oxygen saturation of skin at various ages using our previously proposed method that can rapidly simulate skin spectral reflectance with high accuracy. Oxygen saturation is commonly measured by a pulse oximeter to evaluate oxygen delivery for monitoring the functions of heart and lungs at a specific time. On the other hand, oxygen saturation of skin is expected to assess peripheral conditions. Our previously proposed method, the optical path-length matrix method (OPLM), is based on a Monte Carlo for multi-layered media (MCML), but can simulate skin spectral reflectance 27,000 times faster than MCML. In this study, we implemented an iterative simulation of OPLM with a nonlinear optimization technique such that this method can also be used for estimating hemoglobin concentration and oxygen saturation from the measured skin spectral reflectance. In the experiments, the skin reflectance spectra of 72 outpatients aged between 20 and 86 years were measured by a spectrophotometer. Three points were measured for each subject: the forearm, the thenar eminence, and the intermediate phalanx. The result showed that the oxygen saturation of skin remained constant at each point as the age varied.

Unexpected hypoxia-dependent erythropoietin secretion during experimental conditions not affecting tissue oxygen supply/demand ratio.

PubMed

Bozzini, C E; Barceló, A C; Conti, M I; Martínez, M P; Lezón, C E; Bozzini, C; Alippi, R M

1997-02-01

Although a great deal of evidence supports the hypothesis that plasma erythropoietin (EPO) levels of mammals are related to the oxygen supply to the tissues relative to their oxygen needs, several observation millitate against its inherent simplicity. This study presents our results obtained from in vivo experiments that suggest that hypoxia-dependent EPO production can be altered by conditions which apparently do not modify the tissue oxygen supply/demand ratio. Hypoxia-dependent EPO production rate (EPO-PR), derived from plasma EPO titers and plasma EPO half-lives, were estimated in both transfused-polycythemic and normocythemic mouse models subjected to different treatments. From calculations of the O2 carrying capacity of blood and body O2 consumption, it was assumed that the tissue supply/demand ratios were similar in both experimental and control mice of the same model at the time of induction of EPO production. The following observations were worth noting: (1) EPO-PRs in transfused polycythemic mice whose erythropoietic rates were stimulated by intermittent exposure to hypobaria (0.5 atm, 18 hr/day x 3 weeks), phenylhydrazine administration (40 mg/kg at weekly intervals x 3 weeks) or repeated rh-EPO injections (1500 U/kg 3 times a week x 3 weeks) before transfusion were more than five times high than in comparabily polycythemic mice whose erythropoietic rates were not stimulated previously; and (2) EPO-PR in response to hypobaric hypoxia was 2.08 times normal in normocythemic mice with cyclophosphamide (100 mg/kg) induced depression of erythropoiesis, and 0.33 times normal in normocythemic mice with rh-EPO (400 U/kg x 2) induced enhancement of erythropoiesis. Although the results obtained in polycythemic mice are difficult to explain, those from normocythemic mice suggest the existence of a feedback mechanism between EPO-responsive cells and EPO-producing cells. Both demonstrate the existence of experimental conditions in which modulation of the hypoxia

Vacuum Ultraviolet Absorption Measurements of Atomic Oxygen in a Shock Tube

NASA Technical Reports Server (NTRS)

Meyer, Scott Andrew

1995-01-01

The absorption of vacuum ultraviolet light by atomic oxygen has been measured in the Electric Arc-driven Shock Tube (EAST) Facility at NASA-Ames Research Center. This investigation demonstrates the instrumentation required to determine atomic oxygen concentrations from absorption measurements in impulse facilities. A shock wave dissociates molecular oxygen, producing a high temperature sample of atomic oxygen in the shock tube. A probe beam is generated with a Raman-shifted ArF excimer laser. By suitable tuning of the laser, absorption is measured over a range of wavelengths in the region of the atomic line at 130.49 nm. The line shape function is determined from measurements at atomic oxygen densities of 3 x 10(exp 17) and 9 x 10(exp 17)/cu cm. The broadening coefficient for resonance interactions is deduced from this data, and this value is in accord with available theoretical models.

Vacuum Ultraviolet Absorption Measurements of Atomic Oxygen in a Shock Tube

NASA Technical Reports Server (NTRS)

Meyer, Scott Andrew

1995-01-01

The absorption of vacuum ultraviolet light by atomic oxygen has been measured in the Electric Arc-driven Shock Tube (EAST) Facility at NASA-Ames Research Center. This investigation demonstrates the instrumentation required to determine atomic oxygen concentrations from absorption measurements in impulse facilities. A shock wave dissociates molecular oxygen, producing a high temperature sample of atomic oxygen in the shock tube. A probe beam is generated with a Raman-shifted ArF excimer laser. By suitable tuning of the laser, absorption is measured over a range of wavelengths in the region of the atomic line at 130.49 nm. The line shape function is determined from measurements at atomic oxygen densities of 3x10(exp 17) and 9x10(exp 17) cm(exp -3). The broadening coefficient for resonance interactions is deduced from this data, and this value is in accord with available theoretical models.

Vacuum Ultraviolet Absorption Measurements of Atomic Oxygen in a Shock Tube

NASA Technical Reports Server (NTRS)

Meyer, Scott Andrew

1995-01-01

The absorption of vacuum ultraviolet light by atomic oxygen has been measured in the Electric Arc-driven Shock Tube (EAST) Facility at NASA-Ames Research Center. This investigation demonstrates the instrumentation required to determine atomic oxygen concentrations from absorption measurements in impulse facilities. A shock wave dissociates molecular oxygen, producing a high temperature sample of atomic oxygen in the shock tube. A probe beam is generated with a Raman-shifted ArF excimer laser. By suitable tuning of the laser, absorption is measured over a range of wavelengths in the region of the atomic line at 130.49 nm. The line shape function is determined from measurements at atomic oxygen densities of 3 x 10(exp 17) and 9 x 10(exp 17) cm(exp -3). The broadening coefficient for resonance interactions is deduced from this data, and this value is in accord with available theoretical models.

A computational model of oxygen delivery by hemoglobin-based oxygen carriers in three-dimensional microvascular networks.

PubMed

Tsoukias, Nikolaos M; Goldman, Daniel; Vadapalli, Arjun; Pittman, Roland N; Popel, Aleksander S

2007-10-21

A detailed computational model is developed to simulate oxygen transport from a three-dimensional (3D) microvascular network to the surrounding tissue in the presence of hemoglobin-based oxygen carriers. The model accounts for nonlinear O(2) consumption, myoglobin-facilitated diffusion and nonlinear oxyhemoglobin dissociation in the RBCs and plasma. It also includes a detailed description of intravascular resistance to O(2) transport and is capable of incorporating realistic 3D microvascular network geometries. Simulations in this study were performed using a computer-generated microvascular architecture that mimics morphometric parameters for the hamster cheek pouch retractor muscle. Theoretical results are presented next to corresponding experimental data. Phosphorescence quenching microscopy provided PO(2) measurements at the arteriolar and venular ends of capillaries in the hamster retractor muscle before and after isovolemic hemodilution with three different hemodilutents: a non-oxygen-carrying plasma expander and two hemoglobin solutions with different oxygen affinities. Sample results in a microvascular network show an enhancement of diffusive shunting between arterioles, venules and capillaries and a decrease in hemoglobin's effectiveness for tissue oxygenation when its affinity for O(2) is decreased. Model simulations suggest that microvascular network anatomy can affect the optimal hemoglobin affinity for reducing tissue hypoxia. O(2) transport simulations in realistic representations of microvascular networks should provide a theoretical framework for choosing optimal parameter values in the development of hemoglobin-based blood substitutes.

2H,3H-decafluoropentane-based nanodroplets: new perspectives for oxygen delivery to hypoxic cutaneous tissues.

PubMed

Prato, Mauro; Magnetto, Chiara; Jose, Jithin; Khadjavi, Amina; Cavallo, Federica; Quaglino, Elena; Panariti, Alice; Rivolta, Ilaria; Benintende, Emilio; Varetto, Gianfranco; Argenziano, Monica; Troia, Adriano; Cavalli, Roberta; Guiot, Caterina

2015-01-01

Perfluoropentane (PFP)-based oxygen-loaded nanobubbles (OLNBs) were previously proposed as adjuvant therapeutic tools for pathologies of different etiology sharing hypoxia as a common feature, including cancer, infection, and autoimmunity. Here we introduce a new platform of oxygen nanocarriers, based on 2H,3H-decafluoropentane (DFP) as core fluorocarbon. These new nanocarriers have been named oxygen-loaded nanodroplets (OLNDs) since DFP is liquid at body temperature, unlike gaseous PFP. Dextran-shelled OLNDs, available either in liquid or gel formulations, display spherical morphology, ~600 nm diameters, anionic charge, good oxygen carrying capacity, and no toxic effects on human keratinocytes after cell internalization. In vitro OLNDs result more effective in releasing oxygen to hypoxic environments than former OLNBs, as demonstrated by analysis through oxymetry. In vivo, OLNDs effectively enhance oxy-hemoglobin levels, as emerged from investigation by photoacoustic imaging. Interestingly, ultrasound (US) treatment further improves transdermal oxygen release from OLNDs. Taken together, these data suggest that US-activated, DFP-based OLNDs might be innovative, suitable and cost-effective devices to topically treat hypoxia-associated pathologies of the cutaneous tissues.

2H,3H-Decafluoropentane-Based Nanodroplets: New Perspectives for Oxygen Delivery to Hypoxic Cutaneous Tissues

PubMed Central

Jose, Jithin; Khadjavi, Amina; Cavallo, Federica; Quaglino, Elena; Panariti, Alice; Rivolta, Ilaria; Benintende, Emilio; Varetto, Gianfranco; Argenziano, Monica; Troia, Adriano; Cavalli, Roberta; Guiot, Caterina

2015-01-01

Perfluoropentane (PFP)-based oxygen-loaded nanobubbles (OLNBs) were previously proposed as adjuvant therapeutic tools for pathologies of different etiology sharing hypoxia as a common feature, including cancer, infection, and autoimmunity. Here we introduce a new platform of oxygen nanocarriers, based on 2H,3H-decafluoropentane (DFP) as core fluorocarbon. These new nanocarriers have been named oxygen-loaded nanodroplets (OLNDs) since DFP is liquid at body temperature, unlike gaseous PFP. Dextran-shelled OLNDs, available either in liquid or gel formulations, display spherical morphology, ~600 nm diameters, anionic charge, good oxygen carrying capacity, and no toxic effects on human keratinocytes after cell internalization. In vitro OLNDs result more effective in releasing oxygen to hypoxic environments than former OLNBs, as demonstrated by analysis through oxymetry. In vivo, OLNDs effectively enhance oxy-hemoglobin levels, as emerged from investigation by photoacoustic imaging. Interestingly, ultrasound (US) treatment further improves transdermal oxygen release from OLNDs. Taken together, these data suggest that US-activated, DFP-based OLNDs might be innovative, suitable and cost-effective devices to topically treat hypoxia-associated pathologies of the cutaneous tissues. PMID:25781463

"In vivo" measurement of total gas pressure in mammalian tissue.

DOT National Transportation Integrated Search

1963-07-01

An in vivo method for the quantitative estimation of total gas pressure in mammalian tissue has been established. This method utilizes a rigid-walled capsule specially constructed to be permeable to oxygen, carbon dioxide and nitrogen (O2, Co2, and N...

3D printing of microtube in solid phantom to simulate tissue oxygenation and perfusion (Conference Presentation)

NASA Astrophysics Data System (ADS)

Lv, Xiang; Xue, Yue; Wang, Haili; Shen, Shu Wei; Zhou, Ximing; Liu, Guangli; Dong, Erbao; Xu, Ronald X.

2017-03-01

Tissue-simulating phantoms with interior vascular network may facilitate traceable calibration and quantitative validation of many medical optical devices. However, a solid phantom that reliably simulates tissue oxygenation and blood perfusion is still not available. This paper presents a new method to fabricate hollow microtubes for blood vessel simulation in solid phantoms. The fabrication process combines ultraviolet (UV) rapid prototyping technique with fluid mechanics of a coaxial jet flow. Polydimethylsiloxane (PDMS) and a UV-curable polymer are mixed at the designated ratio and extruded through a coaxial needle device to produce a coaxial jet flow. The extruded jet flow is quickly photo-polymerized by ultraviolet (UV) light to form vessel-simulating solid structures at different sizes ranging from 700 μm to 1000 μm. Microtube structures with adequate mechanical properties can be fabricated by adjusting material compositions and illumination intensity. Curved, straight and stretched microtubes can be formed by adjusting the extrusion speed of the materials and the speed of the 3D printing platform. To simulate vascular structures in biologic tissue, we embed vessel-simulating microtubes in a gel wax phantom of 10 cm x10 cm x 5 cm at the depth from 1 to 2 mm. Bloods at different oxygenation and hemoglobin concentration levels are circulated through the microtubes at different flow rates in order to simulate different oxygenation and perfusion conditions. The simulated physiologic parameters are detected by a tissue oximeter and a laser speckle blood flow meter respectively and compared with the actual values. Our experiments demonstrate that the proposed 3D printing process is able to produce solid phantoms with simulated vascular networks for potential applications in medical device calibration and drug delivery studies.

Retinal oxygen saturation evaluation by multi-spectral fundus imaging

NASA Astrophysics Data System (ADS)

Khoobehi, Bahram; Ning, Jinfeng; Puissegur, Elise; Bordeaux, Kimberly; Balasubramanian, Madhusudhanan; Beach, James

2007-03-01

Purpose: To develop a multi-spectral method to measure oxygen saturation of the retina in the human eye. Methods: Five Cynomolgus monkeys with normal eyes were anesthetized with intramuscular ketamine/xylazine and intravenous pentobarbital. Multi-spectral fundus imaging was performed in five monkeys with a commercial fundus camera equipped with a liquid crystal tuned filter in the illumination light path and a 16-bit digital camera. Recording parameters were controlled with software written specifically for the application. Seven images at successively longer oxygen-sensing wavelengths were recorded within 4 seconds. Individual images for each wavelength were captured in less than 100 msec of flash illumination. Slightly misaligned images of separate wavelengths due to slight eye motion were registered and corrected by translational and rotational image registration prior to analysis. Numerical values of relative oxygen saturation of retinal arteries and veins and the underlying tissue in between the artery/vein pairs were evaluated by an algorithm previously described, but which is now corrected for blood volume from averaged pixels (n > 1000). Color saturation maps were constructed by applying the algorithm at each image pixel using a Matlab script. Results: Both the numerical values of relative oxygen saturation and the saturation maps correspond to the physiological condition, that is, in a normal retina, the artery is more saturated than the tissue and the tissue is more saturated than the vein. With the multi-spectral fundus camera and proper registration of the multi-wavelength images, we were able to determine oxygen saturation in the primate retinal structures on a tolerable time scale which is applicable to human subjects. Conclusions: Seven wavelength multi-spectral imagery can be used to measure oxygen saturation in retinal artery, vein, and tissue (microcirculation). This technique is safe and can be used to monitor oxygen uptake in humans. This work

Microfluidic wound bandage: localized oxygen modulation of collagen maturation.

PubMed

Lo, Joe F; Brennan, Martin; Merchant, Zameer; Chen, Lin; Guo, Shujuan; Eddington, David T; DiPietro, Luisa A

2013-01-01

Restoring tissue oxygenation has the potential to improve poorly healing wounds with impaired microvasculature. Compared with more established wound therapy using hyperbaric oxygen chambers, topical oxygen therapy has lower cost and better patient comfort, although topical devices have provided inconsistent results. To provide controlled topical oxygen while minimizing moisture loss, a major issue for topical oxygen, we have devised a novel wound bandage based on microfluidic diffusion delivery of oxygen. In addition to modulating oxygen from 0 to 100% in 60 seconds rise time, the microfluidic oxygen bandage provides a conformal seal around the wound. When 100% oxygen is delivered, it penetrates wound tissues as measured in agar phantom and in vivo wounds. Using this microfluidic bandage, we applied the oxygen modulation to 8 mm excisional wounds prepared on diabetic mice. Treatment with the microfluidic bandage demonstrated improved collagen maturity in the wound bed, although only marginal differences were observed in total collagen, microvasculature, and external closure rates. Our results show that proper topical oxygen can improve wound parameters underneath the surface. Because of the ease of fabrication, the oxygen bandage represents an economical yet practical method for oxygen wound research. © 2013 by the Wound Healing Society.

Real-Time Monitoring of Singlet Oxygen and Oxygen Partial Pressure During the Deep Photodynamic Therapy In Vitro.

PubMed

Li, Weitao; Huang, Dong; Zhang, Yan; Liu, Yangyang; Gu, Yueqing; Qian, Zhiyu

2016-09-01

Photodynamic therapy (PDT) is an effective noninvasive method for the tumor treatment. The major challenge in current PDT research is how to quantitatively evaluate therapy effects. To our best knowledge, this is the first time to combine multi-parameter detection methods in PDT. More specifically, we have developed a set of system, including the high-sensitivity measurement of singlet oxygen, oxygen partial pressure and fluorescence image. In this paper, the detection ability of the system was validated by the different concentrations of carbon quantum dots. Moreover, the correlation between singlet oxygen and oxygen partial pressure with laser irradiation was observed. Then, the system could detect the signal up to 0.5 cm tissue depth with 660 nm irradiation and 1 cm tissue depth with 980 nm irradiation by using up-conversion nanoparticles during PDT in vitro. Furthermore, we obtained the relationship among concentration of singlet oxygen, oxygen partial pressure and tumor cell viability under certain conditions. The results indicate that the multi-parameter detection system is a promising asset to evaluate the deep tumor therapy during PDT. Moreover, the system might be potentially used for the further study in biology and molecular imaging.

Combined Hyperbaric Oxygen Partial Pressure at 1.4 Bar with Infrared Radiation: A Useful Tool To Improve Tissue Hypoxemia?

PubMed

Dünnwald, Tobias; Held, Julia; Balan, Petru; Pecher, Otto; Zeiger, Thomas; Hartig, Frank; Mur, Erich; Weiss, Günter; Schobersberger, Wolfgang

2018-06-13

Tissue hypoxia contributes to the pathogenesis of several acute and chronic diseases. Hyperbaric oxygen therapy (HBO) and whole-body warming using low-temperature infrared technology (LIT) are techniques that might improve hypoxemia. Combining HBO and LIT as hyperbaric oxygen therapy combined with low-temperature infrared radiation (HBOIR) might be an approach that results in positive synergistic effects on oxygenation. LIT increases blood flow and could reduce HBO-induced vasoconstriction, and hyperoxia could compensate for the increased metabolic oxygen requirements mediated by LIT. Both LIT and HBO increase the oxygen diffusion distance in the tissues. HBOIR at 0.5 bar has been shown to be safe and feasible. However, physiological responses and the safety of HBOIR at an increased oxygen (O2) partial pressure of 1.4 bar or 2.4 atmospheres absolute (ATA) still need to be determined. The hope is that should HBOIR at an increased oxygen partial pressure of 1.4 bar be safe, future studies to examine its efficacy in patients with clinical conditions, which include peripheral arterial disease (PAD) or wound healing disorders, will follow. The results of pilot studies have shown that HBOIR at an overload pressure is safe and well tolerated in healthy participants but can generate moderate cardiovascular changes and an increase in body temperature. From the findings of this pilot study, due to its potential synergistic effects, HBOIR could be a promising tool for the treatment of human diseases associated with hypoxemia.

Multimodal noninvasive monitoring of soft tissue wound healing.

PubMed

Bodo, Michael; Settle, Timothy; Royal, Joseph; Lombardini, Eric; Sawyer, Evelyn; Rothwell, Stephen W

2013-12-01

Here we report results of non-invasive measurements of indirect markers of soft tissue healing of traumatic wounds in an observational swine study and describe the quantification of analog physiological signals. The primary purpose of the study was to measure bone healing of fractures with four different wound treatments. A second purpose was to quantify soft tissue wound healing by measuring the following indirect markers: (1) tissue oxygenation, (2) fluid content, and (3) blood flow, which were all measured by non-invasive modalities, measured with available devices. Tissue oxygenation was measured by near infrared spectroscopy; fluid content was measured by bipolar bio-impedance; and blood flow was measured by Doppler ultrasound. Immediately after comminuted femur fractures were produced in the right hind legs of thirty anesthetized female Yorkshire swine, one of four wound treatments was instilled into each wound. The four wound treatments were as follows: salmon fibrinogen/thrombin-n = 8; commercial bone filler matrix-n = 7; bovine collagen-n = 8; porcine fibrinogen/thrombin-n = 7. Fractures were stabilized with an external fixation device. Immediately following wound treatments, measurements were made of tissue oxygenation, fluid content and blood flow; these measurements were repeated weekly for 3 weeks after surgery. Analog signals of each modality were recorded on both the wounded (right) hind leg and the healthy (left) hind leg, for comparison purposes. Data were processed off-line. The mean values of 10-s periods were calculated for right-left leg comparison. ANOVA was applied for statistical analysis. Results of the bone healing studies are published separately (Rothwell et al. in J Spec Oper Med 13:7-18, 2013). For soft tissue wounds, healing did not differ significantly among the four wound treatments; however, regional oxygenation of wounds treated with salmon fibrinogen/thrombin showed slightly different time trends. Further studies are

Oxygen measurement by multimode diode lasers employing gas correlation spectroscopy.

PubMed

Lou, Xiutao; Somesfalean, Gabriel; Chen, Bin; Zhang, Zhiguo

2009-02-10

Multimode diode laser (MDL)-based correlation spectroscopy (COSPEC) was used to measure oxygen in ambient air, thereby employing a diode laser (DL) having an emission spectrum that overlaps the oxygen absorption lines of the A band. A sensitivity of 700 ppm m was achieved with good accuracy (2%) and linearity (R(2)=0.999). For comparison, measurements of ambient oxygen were also performed by tunable DL absorption spectroscopy (TDLAS) technique employing a vertical cavity surface emitting laser. We demonstrate that, despite slightly degraded sensitivity, the MDL-based COSPEC-based oxygen sensor has the advantages of high stability, low cost, ease-of-use, and relaxed requirements in component selection and instrument buildup compared with the TDLAS-based instrument.

Deriving concentrations of oxygen and carbon in human tissues using single- and dual-energy CT for ion therapy applications

NASA Astrophysics Data System (ADS)

Landry, Guillaume; Parodi, Katia; Wildberger, Joachim E.; Verhaegen, Frank

2013-08-01

Dedicated methods of in-vivo verification of ion treatment based on the detection of secondary emitted radiation, such as positron-emission-tomography and prompt gamma detection require high accuracy in the assignment of the elemental composition. This especially concerns the content in carbon and oxygen, which are the most abundant elements of human tissue. The standard single-energy computed tomography (SECT) approach to carbon and oxygen concentration determination has been shown to introduce significant discrepancies in the carbon and oxygen content of tissues. We propose a dual-energy CT (DECT)-based approach for carbon and oxygen content assignment and investigate the accuracy gains of the method. SECT and DECT Hounsfield units (HU) were calculated using the stoichiometric calibration procedure for a comprehensive set of human tissues. Fit parameters for the stoichiometric calibration were obtained from phantom scans. Gaussian distributions with standard deviations equal to those derived from phantom scans were subsequently generated for each tissue for several values of the computed tomography dose index (CTDIvol). The assignment of %weight carbon and oxygen (%wC,%wO) was performed based on SECT and DECT. The SECT scheme employed a HU versus %wC,O approach while for DECT we explored a Zeff versus %wC,O approach and a (Zeff, ρe) space approach. The accuracy of each scheme was estimated by calculating the root mean square (RMS) error on %wC,O derived from the input Gaussian distribution of HU for each tissue and also for the noiseless case as a limiting case. The (Zeff, ρe) space approach was also compared to SECT by comparing RMS error for hydrogen and nitrogen (%wH,%wN). Systematic shifts were applied to the tissue HU distributions to assess the robustness of the method against systematic uncertainties in the stoichiometric calibration procedure. In the absence of noise the (Zeff, ρe) space approach showed more accurate %wC,O assignment (largest error of

Effects of topical negative pressure therapy on tissue oxygenation and wound healing in vascular foot wounds.

PubMed

Chiang, Nathaniel; Rodda, Odette A; Sleigh, Jamie; Vasudevan, Thodur

2017-08-01

Topical negative pressure (TNP) therapy is widely used in the treatment of acute wounds in vascular patients on the basis of proposed multifactorial benefits. However, numerous recent systematic reviews have concluded that there is inadequate evidence to support its benefits at a scientific level. This study evaluated the changes in wound volume, surface area, depth, collagen deposition, and tissue oxygenation when using TNP therapy compared with traditional dressings in patients with acute high-risk foot wounds. This study was performed with hospitalized vascular patients. Forty-eight patients were selected with an acute lower extremity wound after surgical débridement or minor amputation that had an adequate blood supply without requiring further surgical revascularization and were deemed suitable for TNP therapy. The 22 patients who completed the study were randomly allocated to a treatment group receiving TNP or to a control group receiving regular topical dressings. Wound volume and wound oxygenation were analyzed using a modern stereophotographic wound measurement system and a hyperspectral transcutaneous oxygenation measurement system, respectively. Laboratory analysis was conducted on wound biopsy samples to determine hydroxyproline levels, a surrogate marker to collagen. Differences in clinical or demographic characteristics or in the location of the foot wounds were not significant between the two groups. All patients, with the exception of two, had diabetes. The two patients who did not have diabetes had end-stage renal failure. There was no significance in the primary outcome of wound volume reduction between TNP and control patients on day 14 (44.2% and 20.9%, respectively; P = .15). Analyses of secondary outcomes showed a significant result of better healing rates in the TNP group by demonstrating a reduction in maximum wound depth at day 14 (36.0% TNP vs 17.6% control; P = .03). No significant findings were found for the other outcomes of changes

Measurement of Reactive Oxygen Species, Reactive Nitrogen Species, and Redox-Dependent Signaling in the Cardiovascular System: A Scientific Statement From the American Heart Association.

PubMed

Griendling, Kathy K; Touyz, Rhian M; Zweier, Jay L; Dikalov, Sergey; Chilian, William; Chen, Yeong-Renn; Harrison, David G; Bhatnagar, Aruni

2016-08-19

Reactive oxygen species and reactive nitrogen species are biological molecules that play important roles in cardiovascular physiology and contribute to disease initiation, progression, and severity. Because of their ephemeral nature and rapid reactivity, these species are difficult to measure directly with high accuracy and precision. In this statement, we review current methods for measuring these species and the secondary products they generate and suggest approaches for measuring redox status, oxidative stress, and the production of individual reactive oxygen and nitrogen species. We discuss the strengths and limitations of different methods and the relative specificity and suitability of these methods for measuring the concentrations of reactive oxygen and reactive nitrogen species in cells, tissues, and biological fluids. We provide specific guidelines, through expert opinion, for choosing reliable and reproducible assays for different experimental and clinical situations. These guidelines are intended to help investigators and clinical researchers avoid experimental error and ensure high-quality measurements of these important biological species. © 2016 American Heart Association, Inc.

Device for measuring the total concentration of oxygen in gases

DOEpatents

Isaacs, Hugh S.; Romano, Anthony J.

1977-01-01

This invention provides a CO equilibrium in a device for measuring the total concentration of oxygen impurities in a fluid stream. To this end, the CO equilibrium is produced in an electrochemical measuring cell by the interaction of a carbon element in the cell with the chemically combined and uncombined oxygen in the fluid stream at an elevated temperature.

A topical aqueous oxygen emulsion stimulates granulation tissue formation in a porcine second-degree burn wound.

PubMed

Li, Jie; Zhang, Yan-Ping; Zarei, Mina; Zhu, Linjian; Sierra, Jose Ollague; Mertz, Patricia M; Davis, Stephen C

2015-08-01

Oxygen is an essential substance for wound healing. Limited studies have shown that topical oxygen can influence healing. This study evaluated the effects of a Topical Oxygen Emulsion (TOE) on burn wound healing. A porcine second-degree burn wound model was used in the study. Burn wounds were randomly assigned to TOE, vehicle control, and no-treatment (air) groups. Effects of TOE on the granulation tissue formation and angiogenesis were studied using hematoxylin and eosin histological analysis. Protein production and gene expression of types I and III collagen and vascular endothelial growth factor (VEGF) were determined using immunofluorescent staining and Reverse Transcription and Polymerase Chain Reaction (RT-PCR), respectively. The TOE treated wounds exhibited better angiogenesis and granulation tissue formation by histology examination. The immunofluorescence staining and RT-PCR analysis demonstrated that protein production and mRNA expression of VEGF and collagen III were significantly higher in TOE treatment group than vehicle alone and air control groups, while there was no significant difference in the level of collagen I. Our data demonstrate that TOE enhances burn wound healing via stimulating the expression of VEGF and type III collagen and strongly indicates the potential use of TOE in wounds. Copyright © 2014 Elsevier Ltd and ISBI. All rights reserved.

Mapping oxygen concentration in the awake mouse brain

PubMed Central

Lyons, Declan G; Parpaleix, Alexandre; Roche, Morgane; Charpak, Serge

2016-01-01

Although critical for brain function, the physiological values of cerebral oxygen concentration have remained elusive because high-resolution measurements have only been performed during anesthesia, which affects two major parameters modulating tissue oxygenation: neuronal activity and blood flow. Using measurements of capillary erythrocyte-associated transients, fluctuations of oxygen partial pressure (Po2) associated with individual erythrocytes, to infer Po2 in the nearby neuropil, we report the first non-invasive micron-scale mapping of cerebral Po2 in awake, resting mice. Interstitial Po2 has similar values in the olfactory bulb glomerular layer and the somatosensory cortex, whereas there are large capillary hematocrit and erythrocyte flux differences. Awake tissue Po2 is about half that under isoflurane anesthesia, and within the cortex, vascular and interstitial Po2 values display layer-specific differences which dramatically contrast with those recorded under anesthesia. Our findings emphasize the importance of measuring energy parameters non-invasively in physiological conditions to precisely quantify and model brain metabolism. DOI: http://dx.doi.org/10.7554/eLife.12024.001 PMID:26836304

Reaction rates of oxygen with hemoglobin measured by non-equilibrium facilitated oxygen diffusion through hemoglobin solutions.

PubMed

Bouwer, S T; Hoofd, L; Kreuzer, F

2001-02-16

The purpose of this study was to verify the concept of non-equilibrium facilitated oxygen diffusion. This work succeeds our previous study, where facilitated oxygen diffusion by hemoglobin was measured at conditions of chemical equilibrium, and which yielded diffusion coefficients of hemoglobin and of oxygen. In the present work chemical non-equilibrium was induced using very thin diffusion layers. As a result, facilitation was decreased as predicted by theory. Thus, this work presents the first experimental demonstration of non-equilibrium facilitated oxygen diffusion. In addition, association and dissociation rate parameters of the reaction between oxygen and bovine and human hemoglobin were calculated and the effect of the homotropic and heterotropic interactions on each rate parameter was demonstrated. The results indicate that the homotropic interaction--which leads to increasing oxygen affinity with increasing oxygenation--is predominantly due to an increase in the association rate. The heterotropic interaction--which leads to decreasing oxygen affinity by anionic ligands--appears to be effected in two ways. Cl- increases the dissociation rate. In contrast, 2,3-diphosphoglycerate decreases the association rate.

Oscillation in tissue oxygen index during recovery from exercise.

PubMed

Yano, T; Afroundeh, R; Shirakawa, K; Lian, C-S; Shibata, K; Xiao, Z; Yunoki, T

2016-06-20

It was hypothesized that an oscillation of tissue oxygen index (TOI) determined by near-infrared spectroscopy during recovery from exercise occurs due to feedback control of adenosine triphosphate and that frequency of the oscillation is affected by blood pH. In order to examine these hypotheses, we aimed 1) to determine whether there is an oscillation of TOI during recovery from exercise and 2) to determine the effect of blood pH on frequency of the oscillation of TOI. Three exercises were performed with exercise intensities of 30 % and 70 % peak oxygen uptake (V(.)o(2)peak) for 12 min and with exercise intensity of 70 % V(.)o(2)peak for 30 s. TOI during recovery from the exercise was analyzed by fast Fourier transform in order to obtain power spectra density (PSD). There was a significant difference in the frequency at which maximal PSD of TOI appeared (Fmax) between the exercises with 70 % V(.)o(2)peak for 12 min (0.0039+/-0 Hz) and for 30 s (0.0061+/-0.0028 Hz). However, there was no significant difference in Fmax between the exercises with 30 % (0.0043+/-0.0013 Hz) and with 70 % V(.)o(2)peak for 12 min despite differences in blood pH and blood lactate from the warmed fingertips. It is concluded that there was an oscillation in TOI during recovery from the three exercises. It was not clearly shown that there was an effect of blood pH on Fmax.

Quadriceps oxygenation changes during walking and running on a treadmill

NASA Astrophysics Data System (ADS)

Quaresima, Valentina; Pizzi, Assunta; De Blasi, Roberto A.; Ferrari, Adriano; de Angelis, Marco; Ferrari, Marco

1995-04-01

Vastus lateralis muscle oxygenation was investigated on volunteers as well as muscular dystrophy patients during a walking test, and on volunteers during a free running by a continuous wave near infrared instrument. The data were analyzed using an oxygenation index independent on pathlength changes. Walking did not significantly affect the oxygenation of volunteers and patients. A relative deoxygenation was found only during free running indicating an unbalance between oxygen supply and tissue oxygen extraction. Preliminary measurements of exercising muscle oxygen saturation were performed by a 110 MHz frequency-domain, multisource instrument.

Simultaneous measurement of macro- and microvascular blood flow and oxygen saturation for quantification of muscle oxygen consumption.

PubMed

Englund, Erin K; Rodgers, Zachary B; Langham, Michael C; Mohler, Emile R; Floyd, Thomas F; Wehrli, Felix W

2018-02-01

To investigate the relationship between blood flow and oxygen consumption in skeletal muscle, a technique called "Velocity and Perfusion, Intravascular Venous Oxygen saturation and T2*" (vPIVOT) is presented. vPIVOT allows the quantification of feeding artery blood flow velocity, perfusion, draining vein oxygen saturation, and muscle T2*, all at 4-s temporal resolution. Together, the measurement of blood flow and oxygen extraction can yield muscle oxygen consumption ( V˙O2) via the Fick principle. In five subjects, vPIVOT-derived results were compared with those obtained from stand-alone sequences during separate ischemia-reperfusion paradigms to investigate the presence of measurement bias. Subsequently, in 10 subjects, vPIVOT was applied to assess muscle hemodynamics and V˙O2 following a bout of dynamic plantar flexion contractions. From the ischemia-reperfusion paradigm, no significant differences were observed between data from vPIVOT and comparison sequences. After exercise, the macrovascular flow response reached a maximum 8 ± 3 s after relaxation; however, perfusion in the gastrocnemius muscle continued to rise for 101 ± 53 s. Peak V˙O2 calculated based on mass-normalized arterial blood flow or perfusion was 15.2 ± 6.7 mL O 2 /min/100 g or 6.0 ± 1.9 mL O 2 /min/100 g, respectively. vPIVOT is a new method to measure blood flow and oxygen saturation, and therefore to quantify muscle oxygen consumption. Magn Reson Med 79:846-855, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Fluorescent microparticles for sensing cell microenvironment oxygen levels within 3D scaffolds

PubMed Central

Acosta, Miguel A.; Ymele-Leki, Patrick; Kostov, Yordan V.; Leach, Jennie B.

2010-01-01

We present the development and characterization of fluorescent oxygen-sensing microparticles designed for measuring oxygen concentration in microenvironments existing within standard cell culture and transparent three-dimensional (3D) cell scaffolds. The microparticle synthesis employs poly(dimethylsiloxane) to encapsulate silica gel particles bound with an oxygen-sensitive luminophore as well as a reference or normalization fluorophore that is insensitive to oxygen. We developed a rapid, automated and non-invasive sensor analysis method based on fluorescence microscopy to measure oxygen concentration in a hydrogel scaffold. We demonstrate that the microparticles are non-cytotoxic and that their response is comparable to that of a traditional dissolved oxygen meter. Microparticle size (5–40 μm) was selected for microscale-mapping of oxygen concentration to allow measurements local to individual cells. Two methods of calibration were evaluated and revealed that the sensor system enables characterization of a range of hypoxic to hyperoxic conditions relevant to cell and tissue biology (i.e., pO2 10–160 mm Hg). The calibration analysis also revealed that the microparticles have a high fraction of quenched luminophore (0.90 ± 0.02), indicating that the reported approach provides significant advantages for sensor performance. This study thus reports a versatile oxygen-sensing technology that enables future correlations of local oxygen concentration with individual cell response in cultured engineered tissues. PMID:19285719

Fluorescent microparticles for sensing cell microenvironment oxygen levels within 3D scaffolds.

PubMed

Acosta, Miguel A; Ymele-Leki, Patrick; Kostov, Yordan V; Leach, Jennie B

2009-06-01

We present the development and characterization of fluorescent oxygen-sensing microparticles designed for measuring oxygen concentration in microenvironments existing within standard cell culture and transparent three-dimensional (3D) cell scaffolds. The microparticle synthesis employs poly(dimethylsiloxane) to encapsulate silica gel particles bound with an oxygen-sensitive luminophore as well as a reference or normalization fluorophore that is insensitive to oxygen. We developed a rapid, automated and non-invasive sensor analysis method based on fluorescence microscopy to measure oxygen concentration in a hydrogel scaffold. We demonstrate that the microparticles are non-cytotoxic and that their response is comparable to that of a traditional dissolved oxygen meter. Microparticle size (5-40 microm) was selected for microscale-mapping of oxygen concentration to allow measurements local to individual cells. Two methods of calibration were evaluated and revealed that the sensor system enables characterization of a range of hypoxic to hyperoxic conditions relevant to cell and tissue biology (i.e., pO(2) 10-160 mmHg). The calibration analysis also revealed that the microparticles have a high fraction of quenched luminophore (0.90+/-0.02), indicating that the reported approach provides significant advantages for sensor performance. This study thus reports a versatile oxygen-sensing technology that enables future correlations of local oxygen concentration with individual cell response in cultured engineered tissues.

Effect of shivering on brain tissue oxygenation during induced normothermia in patients with severe brain injury.

PubMed

Oddo, Mauro; Frangos, Suzanne; Maloney-Wilensky, Eileen; Andrew Kofke, W; Le Roux, Peter D; Levine, Joshua M

2010-02-01

We analyzed the impact of shivering on brain tissue oxygenation (PbtO(2)) during induced normothermia in patients with severe brain injury. We studied patients with severe brain injury who developed shivering during induced normothermia. Induced normothermia was applied to treat refractory fever (body temperature [BT] > or =38.3 degrees C, refractory to conventional treatment) using a surface cooling device with computerized adjustment of patient BT target to 37 +/- 0.5 degrees C. PbtO(2), intracranial pressure, mean arterial pressure, cerebral perfusion pressure, and BT were monitored continuously. Circulating water temperature of the device system was measured to assess the intensity of cooling. Fifteen patients (10 with severe traumatic brain injury, 5 with aneurysmal subarachnoid hemorrhage) were treated with induced normothermia for an average of 5 +/- 2 days. Shivering caused a significant decrease in PbtO(2) levels both in SAH and TBI patients. Compared to baseline, shivering was associated with an overall reduction of PbtO(2) from 34.1 +/- 7.3 to 24.4 +/- 5.5 mmHg (P < 0.001). A significant correlation was found between the magnitude of shivering-associated decrease of PbtO(2) (DeltaPbtO(2)) and circulating water temperature (R = 0.82, P < 0.001). In patients with severe brain injury treated with induced normothermia, shivering was associated with a significant decrease of PbtO(2), which correlated with the intensity of cooling. Monitoring of therapeutic cooling with computerized thermoregulatory systems may help prevent shivering and optimize the management of induced normothermia. The clinical significance of shivering-induced decrease in brain tissue oxygenation remains to be determined.

Heat treatment of human esophageal tissues: Effect on esophageal cancer detection using oxygenated hemoglobin diffuse reflectance ratio

NASA Astrophysics Data System (ADS)

Zhao, Q. L.; Guo, Z. Y.; Si, J. L.; Wei, H. J.; Yang, H. Q.; Wu, G. Y.; Xie, S. S.; Guo, X.; Zhong, H. Q.; Li, L. Q.; Li, X. Y.

2011-03-01

The main objective of the present work is to study the influence of heat treatment on the esophageal cancer detection using the diffuse reflectance (DR) spectral intensity ratio R540/R575 of oxygenated hemoglobin (HbO2) absorption bands to distinguish the epithelial tissues of normal human esophagus and moderately differentiated esophageal squamous cell carcinoma (ESCC) at different heat treatment temperature of 20, 37, 42, 50, and 60°C, respectively. The DR spectra for the epithelial tissues of the normal esophagus and ESCC in vitro at different heat-treatment temperature in the wavelength range 400-650 nm were measured with a commercial optical fiber spectrometer. The results indicate that the average DR spectral intensity overall enhancement with concomitant increase of heat-treatment temperature for the epithelial tissues of normal esophagus and ESCC, but the average DR spectral intensity for the normal esophageal epithelial tissues is relatively higher than that for ESCC epithelial tissues at the same heat-treatment temperature. The mean R540/R575 ratios of ESCC epithelial tissues were always lower than that of normal esophageal epithelial tissues at the same temperature, and the mean R540/R575 ratios of the epithelial tissues of the normal esophagus and ESCC were decreasing with the increase of different heat-treatment temperatures. The differences in the mean R540/R575 ratios between the epithelial tissues of normal esophagus and ESCC were 13.33, 13.59, 11.76, and 11.11% at different heat-treatment temperature of 20, 37, 42, and 50°C, respectively. These results also indicate that the DR intensity ratio R540/R575 of the hemoglobin bands is a useful tool for discrimination between the epithelial tissues of normal esophagus and ESCC in the temperature range from room temperature to 50°C, but it was non-effective at 60°C or over 60°C.

Measuring oxygen uptake in fishes with bimodal respiration.

PubMed

Lefevre, S; Bayley, M; McKenzie, D J

2016-01-01

Respirometry is a robust method for measurement of oxygen uptake as a proxy for metabolic rate in fishes, and how species with bimodal respiration might meet their demands from water v. air has interested researchers for over a century. The challenges of measuring oxygen uptake from both water and air, preferably simultaneously, have been addressed in a variety of ways, which are briefly reviewed. These methods are not well-suited for the long-term measurements necessary to be certain of obtaining undisturbed patterns of respiratory partitioning, for example, to estimate traits such as standard metabolic rate. Such measurements require automated intermittent-closed respirometry that, for bimodal fishes, has only recently been developed. This paper describes two approaches in enough detail to be replicated by the interested researcher. These methods are for static respirometry. Measuring oxygen uptake by bimodal fishes during exercise poses specific challenges, which are described to aid the reader in designing experiments. The respiratory physiology and behaviour of air-breathing fishes is very complex and can easily be influenced by experimental conditions, and some general considerations are listed to facilitate the design of experiments. Air breathing is believed to have evolved in response to aquatic hypoxia and, probably, associated hypercapnia. The review ends by considering what realistic hypercapnia is, how hypercapnic tropical waters can become and how this might influence bimodal animals' gas exchange. © 2015 The Fisheries Society of the British Isles.

Near-infrared spectroscopy of renal tissue in vivo

NASA Astrophysics Data System (ADS)

Grosenick, Dirk; Steinkellner, Oliver; Wabnitz, Heidrun; Macdonald, Rainer; Niendorf, Thoralf; Cantow, Kathleen; Flemming, Bert; Seeliger, Erdmann

2013-03-01

We have developed a method to quantify hemoglobin concentration and oxygen saturation within the renal cortex by near-infrared spectroscopy. A fiber optic probe was used to transmit the radiation of three semiconductor lasers at 690 nm, 800 nm and 830 nm to the tissue, and to collect diffusely remitted light at source-detector separations from 1 mm to 4 mm. To derive tissue hemoglobin concentration and oxygen saturation of hemoglobin the spatial dependence of the measured cw intensities was fitted by a Monte Carlo model. In this model the tissue was assumed to be homogeneous. The scaling factors between measured intensities and simulated photon flux were obtained by applying the same setup to a homogeneous semi-infinite phantom with known optical properties and by performing Monte Carlo simulations for this phantom. To accelerate the fit of the tissue optical properties a look-up table of the simulated reflected intensities was generated for the needed range of absorption and scattering coefficients. The intensities at the three wavelengths were fitted simultaneously using hemoglobin concentration, oxygen saturation, the reduced scattering coefficient at 800 nm and the scatter power coefficient as fit parameters. The method was employed to study the temporal changes of renal hemoglobin concentration and blood oxygenation on an anesthetized rat during a short period of renal ischemia induced by aortic occlusion and during subsequent reperfusion.

Direct Measurements of Oxygen Gradients in Spheroid Culture System Using Electron Parametric Resonance Oximetry

PubMed Central

Langan, Laura M.; Dodd, Nicholas J. F.; Owen, Stewart F.; Purcell, Wendy M.; Jackson, Simon K.; Jha, Awadhesh N.

2016-01-01

Advanced in vitro culture from tissues of different origin includes three-dimensional (3D) organoid micro structures that may mimic conditions in vivo. One example of simple 3D culture is spheroids; ball shaped structures typically used as liver and tumour models. Oxygen is critically important in physiological processes, but is difficult to quantify in 3D culture: and the question arises, how small does a spheroid have to be to have minimal micro-environment formation? This question is of particular importance in the growing field of 3D based models for toxicological assessment. Here, we describe a simple non-invasive approach modified for the quantitative measurement and subsequent evaluation of oxygen gradients in spheroids developed from a non-malignant fish cell line (i.e. RTG-2 cells) using Electron Paramagnetic Resonance (EPR) oximetry. Sonication of the paramagnetic probe Lithium phthalocyanine (LiPc) allows for incorporation of probe particulates into spheroid during its formation. Spectra signal strength after incorporation of probe into spheroid indicated that a volume of 20 μl of probe (stock solution: 0.10 mg/mL) is sufficient to provide a strong spectra across a range of spheroid sizes. The addition of non-toxic probes (that do not produce or consume oxygen) report on oxygen diffusion throughout the spheroid as a function of size. We provide evidence supporting the use of this model over a range of initial cell seeding densities and spheroid sizes with the production of oxygen distribution as a function of these parameters. In our spheroid model, lower cell seeding densities (∼2,500 cells/spheroid) and absolute size (118±32 μm) allow control of factors such as pre-existing stresses (e.g. ∼ 2% normoxic/hypoxic interface) for more accurate measurement of treatment response. The applied methodology provides an elegant, widely applicable approach to directly characterize spheroid (and other organoid) cultures in biomedical and toxicological

Direct Measurements of Oxygen Gradients in Spheroid Culture System Using Electron Parametric Resonance Oximetry.

PubMed

Langan, Laura M; Dodd, Nicholas J F; Owen, Stewart F; Purcell, Wendy M; Jackson, Simon K; Jha, Awadhesh N

2016-01-01

Advanced in vitro culture from tissues of different origin includes three-dimensional (3D) organoid micro structures that may mimic conditions in vivo. One example of simple 3D culture is spheroids; ball shaped structures typically used as liver and tumour models. Oxygen is critically important in physiological processes, but is difficult to quantify in 3D culture: and the question arises, how small does a spheroid have to be to have minimal micro-environment formation? This question is of particular importance in the growing field of 3D based models for toxicological assessment. Here, we describe a simple non-invasive approach modified for the quantitative measurement and subsequent evaluation of oxygen gradients in spheroids developed from a non-malignant fish cell line (i.e. RTG-2 cells) using Electron Paramagnetic Resonance (EPR) oximetry. Sonication of the paramagnetic probe Lithium phthalocyanine (LiPc) allows for incorporation of probe particulates into spheroid during its formation. Spectra signal strength after incorporation of probe into spheroid indicated that a volume of 20 μl of probe (stock solution: 0.10 mg/mL) is sufficient to provide a strong spectra across a range of spheroid sizes. The addition of non-toxic probes (that do not produce or consume oxygen) report on oxygen diffusion throughout the spheroid as a function of size. We provide evidence supporting the use of this model over a range of initial cell seeding densities and spheroid sizes with the production of oxygen distribution as a function of these parameters. In our spheroid model, lower cell seeding densities (∼2,500 cells/spheroid) and absolute size (118±32 μm) allow control of factors such as pre-existing stresses (e.g. ∼ 2% normoxic/hypoxic interface) for more accurate measurement of treatment response. The applied methodology provides an elegant, widely applicable approach to directly characterize spheroid (and other organoid) cultures in biomedical and toxicological

The MOST - Monitor for Oxygenation of Surface and Tissue.

DTIC Science & Technology

1995-10-01

CAT Reduce need for ICU, low risk groups Central nursing station Office procedures: Dentistry , Endoscopy Monitoring spinal or epidural narcotics Home...obtainable by using laser Doppler methods (Wickramasinghe et al., 1994; Liepsch et al., 1993; Mendelson, Ochs, 1988). While many parameters beyond oxygenation...blood flow include laser Doppler flowmetry sys- tems which are currently commercially available. These systems measure the velocity of blood particles

Circulatory oxygen transport in the water flea Daphnia magna.

PubMed

Bäumer, C; Pirow, R; Paul, R J

2002-05-01

To determine the contribution of circulatory convection to tissue oxygen supply in animals of Daphnia magna, heart rate ( f(H)), in-vivo Hb oxygen-saturation ( S(Hb)) and NADH fluorescence intensity ( I(NADH)) as a measure of the tissue oxygenation state were simultaneously measured using digital motion analysis, microabsorption spectroscopy and fluorescence microscopy. In addition, the relationship between stroke volume and body size was established. Groups of differently sized animals (small: 1.4-1.6 mm, medium: 2.7-2.9 mm, large: 3.3 mm) with either low (Hb-poor) or high Hb concentration (Hb-rich) in the hemolymph were exposed to a gradual decrease in ambient oxygen partial pressure ( P(O2amb)) between normoxia and anoxia. In all groups, f(H) increased in response to progressive hypoxia. The hypoxic maximum in f(H) was highest in medium-sized Hb-poor animals, whereas perfusion rate increased continuously with increasing body size in Hb-poor and Hb-rich animals. The P(O2amb) at which Hb in the heart region was half-saturated (in-vivo P(50)) was higher in medium-sized (Hb-poor: 3.2 kPa, Hb-rich: 2.0 kPa) than in small (Hb-poor: 2.1 kPa, Hb-rich: 1.5 kPa) and large animals (Hb-poor: 1.9 kPa). The in-vivo P(50) was always lower in Hb-rich than in Hb-poor animals. The I(NADH) indicated an impairment of tissue oxygenation starting at higher critical P(O2amb) with increasing body size and with lower Hb concentration. Model calculations suggest that at the respective critical P(O2amb), circulatory convection delivers less than half of the oxygen demand in Hb-poor animals. In contrast, in Hb-rich animals, the contribution of circulatory convection to tissue oxygen supply at respective critical P(O2amb) was much greater due to the higher concentration of Hb.

Reproducibility of retinal vessel oxygen saturation measurements in healthy young subjects.

PubMed

Lasta, Michael; Palkovits, Stefan; Boltz, Agnes; Schmidl, Doreen; Kaya, Semira; Cherecheanu, Alina Popa; Garhöfer, Gerhard; Schmetterer, Leopold

2012-12-01

An adequate oxygenation and perfusion is essential for the function of the inner retina. Recently, several techniques for the measurement of retinal oxygen saturation became available. We set out to evaluate reproducibility of the measurements using a modified Retinal Vessel Analyzer. A total of 20 healthy female and male subjects aged between 18 and 35 years (22.9 ± 3.9; mean ± SD) were included. The measurement of retinal oxygen saturation with the retinal oximeter employed in this study is based on optical reflectometry using the different absorption characteristics of oxygenated and deoxygenated haemoglobin. The intraclass correlation coefficients and the coefficients of variation (CV) for test-retest, short-term as well as day-to-day measurements were calculated.   The intraclass correlation coefficients were between 0.91 and 0.94 for retinal branch arteries and between 0.84 and 0.88 for retinal branch veins. In retinal arteries, we calculated a test-retest CV of 3.24 ± 3.18% for oxygen saturation measurements. In retinal veins, data were slightly less reproducible with a CV of 4.92 ± 3.57%. Short-term reproducibility of both measurement cycles on each study day was in the same range (CV in retinal arteries: 2.91 ± 2.42% and CV in retinal veins: 4.76 ± 3.14%). The day-to-day coefficient of variation was slightly higher (CV in retinal arteries: 3.97 ± 2.87% and CV in retinal veins: 6.18 ± 3.36%). The reproducibility of haemoglobin oxygen saturation measurements using the retinal oximeter is acceptable. Further studies on the validity of the obtained results are, however, required. © 2012 The Authors. Acta Ophthalmologica © 2012 Acta Ophthalmologica Scandinavica Foundation.

Investigation of endocrine and immunological response in fat tissue to hyperbaric oxygen administration in rats.

PubMed

Şen, H; Erbağ, G; Ovali, M A; Öztopuz, R Ö; Uzun, M

2016-04-30

Though HBO treatment is becoming more common, the mechanism of action is not fully known. The positive effects of HBO administration on the inflammatory response is thought to be a possible basic mechanism. As a result, we aimed to research whether endocrine and immunological response of fat tissue changes in rats given HBO treatment model. This research was carried out on Wistar albino rats, they were treated with hyperbaric oxygen therapy. Their fatty tissue were taken from the abdomen, gene expression of the cytokines and adipokines were analyzed with Real time PCR method. When the gene expression of hormones and cytokines by fat tissue was examined, the leptin, visfatin, TNF-α, IL-1β and IL-10 levels in the HBO treatment group were statistically significantly increased compared to the control group (p=0.0313, p=0.0156, p=0.0156, p=0.0156, p=0.0313). In conclusion, in our study we identified that HBO administration affected the endochrinological functions of fat tissue.

Effects of Fiber Type and Size on the Heterogeneity of Oxygen Distribution in Exercising Skeletal Muscle

PubMed Central

Liu, Gang; Mac Gabhann, Feilim; Popel, Aleksander S.

2012-01-01

The process of oxygen delivery from capillary to muscle fiber is essential for a tissue with variable oxygen demand, such as skeletal muscle. Oxygen distribution in exercising skeletal muscle is regulated by convective oxygen transport in the blood vessels, oxygen diffusion and consumption in the tissue. Spatial heterogeneities in oxygen supply, such as microvascular architecture and hemodynamic variables, had been observed experimentally and their marked effects on oxygen exchange had been confirmed using mathematical models. In this study, we investigate the effects of heterogeneities in oxygen demand on tissue oxygenation distribution using a multiscale oxygen transport model. Muscles are composed of different ratios of the various fiber types. Each fiber type has characteristic values of several parameters, including fiber size, oxygen consumption, myoglobin concentration, and oxygen diffusivity. Using experimentally measured parameters for different fiber types and applying them to the rat extensor digitorum longus muscle, we evaluated the effects of heterogeneous fiber size and fiber type properties on the oxygen distribution profile. Our simulation results suggest a marked increase in spatial heterogeneity of oxygen due to fiber size distribution in a mixed muscle. Our simulations also suggest that the combined effects of fiber type properties, except size, do not contribute significantly to the tissue oxygen spatial heterogeneity. However, the incorporation of the difference in oxygen consumption rates of different fiber types alone causes higher oxygen heterogeneity compared to control cases with uniform fiber properties. In contrast, incorporating variation in other fiber type-specific properties, such as myoglobin concentration, causes little change in spatial tissue oxygenation profiles. PMID:23028531

In vitro study of 3D PLGA/n-HAp/β-TCP composite scaffolds with etched oxygen plasma surface modification in bone tissue engineering

NASA Astrophysics Data System (ADS)

Roh, Hee-Sang; Jung, Sang-Chul; Kook, Min-Suk; Kim, Byung-Hoon

2016-12-01

Three-dimensional (3D) scaffolds have many advantageous properties for bone tissue engineering application, due to its controllable properties such as pore size, structural shape and interconnectivity. In this study, effects on oxygen plasma surface modification and adding of nano-hydroxyapatite (n-HAp) and β-tricalcium phosphate (β-TCP) on the 3D PLGA/n-HAp/β-TCP scaffolds for improving preosteoblast cell (MC3T3-E1) adhesion, proliferation and differentiation were investigated. The 3D PLGA/n-HAp/β-TCP scaffolds were fabricated by 3D Bio-Extruder equipment. The 3D scaffolds were prepared with 0°/90° architecture and pore size of approximately 300 μm. In addition 3D scaffolds surface were etched by oxygen plasma to enhance the hydrophilic property and surface roughness. After oxygen plasma treatment, the surface chemistry and morphology were investigated by Fourier transform infrared spectroscopy, scanning electron microscopy, and atomic force microscopy. And also hydrophilic property was measured by contact angle. The MC3T3-E1 cell proliferation and differentiation were investigated by MTT assay and ALP activity. In present work, the 3D PLGA/HAp/beta-TCP composite scaffold with suitable structure for the growth of osteoblast cells was successfully fabricated by 3D rapid prototyping technique. The surface hydrophilicity and roughness of 3D scaffold increased by oxygen plasma treatment had a positive effect on cell adhesion, proliferation, and differentiation. Furthermore, the differentiation of MC3T3-E1 cell was significantly enhanced by adding of n-HAp and β-TCP on 3D PLGA scaffold. As a result, combination of bioceramics and oxygen plasma treatment showed a synergistic effect on biocompatibility of 3D scaffolds. This result confirms that this technique was useful tool for improving the biocompatibility in bone tissue engineering application.

[The effects of oxygen partial pressure changes on the osteometric markers of the bone tissue in rats].

PubMed

Berezovs'kyĭ, V Ia; Zamors'ka, T M; Ianko, R V

2013-01-01

Our purpose was to investigate the oxygen partial pressure changes on the osteometric and biochemical markers of bone tissue in rats. It was shown that breathing of altered gas mixture did not change the mass, general length, sagittal diameter and density thigh-bones in 12-month Wistar male-rats. The dosed normobaric hypoxia increased the activity of alkaline phosphatase and decreased the activity of tartrate-resistant acid phosphatase. At the same time normobaric hyperoxia with 40 and 90% oxygen conversely decreased the activity of alkaline phosphatase and increased the activity of tartrate-resistant acid phosphatase.

Endogenous Generation of Singlet Oxygen and Ozone in Human and Animal Tissues: Mechanisms, Biological Significance, and Influence of Dietary Components.

PubMed

Onyango, Arnold N

2016-01-01

Recent studies have shown that exposing antibodies or amino acids to singlet oxygen results in the formation of ozone (or an ozone-like oxidant) and hydrogen peroxide and that human neutrophils produce both singlet oxygen and ozone during bacterial killing. There is also mounting evidence that endogenous singlet oxygen production may be a common occurrence in cells through various mechanisms. Thus, the ozone-producing combination of singlet oxygen and amino acids might be a common cellular occurrence. This paper reviews the potential pathways of formation of singlet oxygen and ozone in vivo and also proposes some new pathways for singlet oxygen formation. Physiological consequences of the endogenous formation of these oxidants in human tissues are discussed, as well as examples of how dietary factors may promote or inhibit their generation and activity.

Endogenous Generation of Singlet Oxygen and Ozone in Human and Animal Tissues: Mechanisms, Biological Significance, and Influence of Dietary Components

PubMed Central

2016-01-01

Recent studies have shown that exposing antibodies or amino acids to singlet oxygen results in the formation of ozone (or an ozone-like oxidant) and hydrogen peroxide and that human neutrophils produce both singlet oxygen and ozone during bacterial killing. There is also mounting evidence that endogenous singlet oxygen production may be a common occurrence in cells through various mechanisms. Thus, the ozone-producing combination of singlet oxygen and amino acids might be a common cellular occurrence. This paper reviews the potential pathways of formation of singlet oxygen and ozone in vivo and also proposes some new pathways for singlet oxygen formation. Physiological consequences of the endogenous formation of these oxidants in human tissues are discussed, as well as examples of how dietary factors may promote or inhibit their generation and activity. PMID:27042259

Oxygen radical absorbance capacity (ORAC) and phenolic and anthocyanin concentrations in fruit and leaf tissues of highbush blueberry.

PubMed

Ehlenfeldt, M K; Prior, R L

2001-05-01

Antioxidant capacity, as measured by oxygen radical absorbance capacity (ORAC), and total phenolic and total anthocyanin contents were evaluated in fruit tissues of 87 highbush blueberry (Vacciniumcorymbosum L.) and species-introgressed highbush blueberry cultivars. ORAC and phenolic levels were evaluated in leaf tissues of the same materials. Average values for ORAC, phenolics, and anthocyanins in fruit were 15.9 ORAC units, 1.79 mg/g (gallic acid equivalents), and 0.95 mg/g (cyanidin-3-glucoside equivalents), respectively. Cv. Rubel had the highest ORAC per gram of fresh weight values, at 31.1 units, and cv. Elliott had the highest values on the basis of ORAC per square centimeter of surface area. In leaf tissue, values for both ORAC and phenolics were significantly higher than in fruit tissue, with mean values of 490 ORAC units and 44.80 mg/g (gallic acid equivalents), respectively. Leaf ORAC had a low, but significant, correlation with fruit phenolics and anthocyanins, but not with fruit ORAC. An analysis of ORAC values versus calculated midparent values in 11 plants from the 87-cultivar group in which all parents were tested suggested that, across cultivars, ORAC inheritance is additive. An investigation of ORAC values in a family of 44 cv. Rubel x Duke seedlings showed negative epistasis for ORAC values, suggesting Rubel may have gene combinations contributing to ORAC that are broken up during hybridization.

Oxygen Flow Rate Requirements of Critically Injured Patients

DTIC Science & Technology

2015-04-08

2.0 BACKGROUND Supplemental oxygen is required to correct hypoxemia and is often used to augment tissue oxygen delivery following hemorrhagic ...least 6 months after enrollment to determine mortality status. 3.4 Outcome Measurements The primary outcomes were the proportion of subjects...and 53/204 (26%) with hemorrhagic shock (systolic blood pressure (SBP) ៊ or blood transfusion). There were 33/142 (23%) patients with an indication

Quantitative fiber-optic Raman spectroscopy for tissue Raman measurements

NASA Astrophysics Data System (ADS)

Duraipandian, Shiyamala; Bergholt, Mads; Zheng, Wei; Huang, Zhiwei

2014-03-01

Molecular profiling of tissue using near-infrared (NIR) Raman spectroscopy has shown great promise for in vivo detection and prognostication of cancer. The Raman spectra measured from the tissue generally contain fundamental information about the absolute biomolecular concentrations in tissue and its changes associated with disease transformation. However, producing analogues tissue Raman spectra present a great technical challenge. In this preliminary study, we propose a method to ensure the reproducible tissue Raman measurements and validated with the in vivo Raman spectra (n=150) of inner lip acquired using different laser powers (i.e., 30 and 60 mW). A rapid Raman spectroscopy system coupled with a ball-lens fiber-optic Raman probe was utilized for tissue Raman measurements. The investigational results showed that the variations between the spectra measured with different laser powers are almost negligible, facilitating the quantitative analysis of tissue Raman measurements in vivo.

[The effect of prophylactically administered n-acetylcysteine on clinical indicators for tissue oxygenation during hyperoxic ventilation in cardiac risk patients].

PubMed

Spies, C; Giese, C; Meier-Hellmann, A; Specht, M; Hannemann, L; Schaffartzik, W; Reinhart, K

1996-04-01

Hyperoxic ventilation, used to prevent hypoxia during potential periods of hypoventilation, has been reported to paradoxically decrease whole-body oxygen consumption (VO2). Reduction in nutritive blood flow due to oxygen radical production is one possible mechanism. We investigated whether pretreatment with the sulfhydryl group donor and O2 radical scavenger N-acetylcysteine (NAC) would preserve VO2 and other clinical indicators of tissue oxygenation in cardiac risk patients. Thirty patients, requiring hemodynamic monitoring (radial and pulmonary artery catheters) because of cardiac risk factors, were included in this randomized investigation. All patients exhibited stable clinical conditions (hemodynamics, body temperature, hemoglobin, F1O2 < 0.5). Cardiac output was determined by thermodilution and VO2 by cardiovascular Fick. After baseline measurements, patients randomly received either 150 mg kg-1 NAC (n = 15) or placebo (n = 15) in 250 ml 5% dextrose i.v. over a period of 30 min. Measurements were repeated 30 min after starting NAC or placebo infusion, 30 min after starting hyperoxia (F1O2 = 1.0), and 30 min after resetting the original F1O2. There were no significant differences between groups in any of the measurements before treatment and after the return to baseline F1O2 at the end of the study, respectively. NAC, but not placebo infusion, caused a slight but not significant increase in cardiac index (CI), left ventricular stroke work index (LVSWI) and a decrease in systemic vascular resistance. Significant differences between groups during hyperoxia were: VO2 (NAC: 108 +/- 38 ml min-1m-2 vs placebo: 79 +/- 22 ml min-1m-2; P < or = 0.05), CI (NAC: 4.6 +/- 1.0 vs placebo: 3.7 +/- 1.11 min-1m-2; P < or = 0.05) and LVSWI (NAC: 47 +/- 12 vs placebo: 38 +/- 9; P < or = 0.05). The mean decrease of VO2 was 22% in the NAC group vs 47% in the placebo group (P < or = 0.05) and the mean difference between groups in venoarterial carbon dioxide gradient (PvaCO2) was 14

Modelling lung and tissue diffusion using a membrane oxygenator circuit.

PubMed

Dunningham, H; Borland, C; Bottrill, F; Gordon, D; Vuylsteke, A

2007-07-01

A simple model lung has been designed using a membrane oxygenator circuit comprising two membrane oxygenators primed with one to two litres of equine blood, giving reproducible results over several hours. Normoxia and normocapnia were achieved consistently over the duration of the test with a blood flow of 2.5 l/min, oxygenator ventilation gas flow of 5 l/min air with 0.3 l/min O2 and deoxygenator ventilation gas flow of 5 l/min 5% CO2 in N2 with 0.2 l/min CO2. The measured PaO2 was 81.3 (SD 3.35 mmHg), PvO2 38.3 (SD 1.38 mmHg), PvCO2 60.6 (SD 1.13 mmHg) and PaCO2 36.1 (SD 0.69mmHg). MO2 and MCO2 were 116 ml/min and 169 ml/min, respectively. An increasing linear relationship was observed for FiO2 and the corresponding PaO2 and, similarly, with FiCO2 and PvCO2, providing reference ranges for this model.

The oxygen paradox of neurovascular coupling

PubMed Central

Leithner, Christoph; Royl, Georg

2014-01-01

The coupling of cerebral blood flow (CBF) to neuronal activity is well preserved during evolution. Upon changes in the neuronal activity, an incompletely understood coupling mechanism regulates diameter changes of supplying blood vessels, which adjust CBF within seconds. The physiologic brain tissue oxygen content would sustain unimpeded brain function for only 1 second if continuous oxygen supply would suddenly stop. This suggests that the CBF response has evolved to balance oxygen supply and demand. Surprisingly, CBF increases surpass the accompanying increases of cerebral metabolic rate of oxygen (CMRO2). However, a disproportionate CBF increase may be required to increase the concentration gradient from capillary to tissue that drives oxygen delivery. However, the brain tissue oxygen content is not zero, and tissue pO2 decreases could serve to increase oxygen delivery without a CBF increase. Experimental evidence suggests that CMRO2 can increase with constant CBF within limits and decreases of baseline CBF were observed with constant CMRO2. This conflicting evidence may be viewed as an oxygen paradox of neurovascular coupling. As a possible solution for this paradox, we hypothesize that the CBF response has evolved to safeguard brain function in situations of moderate pathophysiological interference with oxygen supply. PMID:24149931

A tandem mass spectrometric method for singlet oxygen measurement.

PubMed

Karonen, Maarit; Mattila, Heta; Huang, Ping; Mamedov, Fikret; Styring, Stenbjörn; Tyystjärvi, Esa

2014-01-01

Singlet oxygen, a harmful reactive oxygen species, can be quantified with the substance 2,2,6,6-tetramethylpiperidine (TEMP) that reacts with singlet oxygen, forming a stable nitroxyl radical (TEMPO). TEMPO has earlier been quantified with electron paramagnetic resonance (EPR) spectroscopy. In this study, we designed an ultra-high-performance liquid chromatographic-tandem mass spectrometric (UHPLC-ESI-MS/MS) quantification method for TEMPO and showed that the method based on multiple reaction monitoring (MRM) can be used for the measurements of singlet oxygen from both nonbiological and biological samples. Results obtained with both UHPLC-ESI-MS/MS and EPR methods suggest that plant thylakoid membranes produce 3.7 × 10(-7) molecules of singlet oxygen per chlorophyll molecule in a second when illuminated with the photosynthetic photon flux density of 2000 μmol m(-2 ) s(-1). © 2014 The American Society of Photobiology.

Langley 8-foot high-temperature tunnel oxygen measurement system

NASA Technical Reports Server (NTRS)

Sprinkle, Danny R.; Chen, Tony D.; Chaturvedi, Sushil K.

1991-01-01

In order to ensure that there is a proper amount of oxygen necessary for sustaining test engine operation for hypersonic propulsion systems testing at the NASA Langley 8-foot high-temperature tunnel, a quickly responding real-time measurement system of test section oxygen concentration has been designed and tested at Langley. It is built around a zirconium oxide-based sensor which develops a voltage proportional to the oxygen partial pressure of the test gas. The voltage signal is used to control the amount of oxygen being injected into the combustor air. The physical operation of the oxygen sensor is described, as well as the sampling system used to extract the test gas from the tunnel test section. Results of laboratory tests conducted to verify sensor accuracy and response time performance are discussed, as well as the final configuration of the system to be installed in the tunnel.

Scattering and absorption measurements of cervical tissues measures using low cost multi-spectral imaging

NASA Astrophysics Data System (ADS)

Bernat, Amir S.; Bar-Am, Kfir; Cataldo, Leigh; Bolton, Frank J.; Kahn, Bruce S.; Levitz, David

2018-02-01

Cervical cancer is a leading cause of death for women in low resource settings. In order to better detect cervical dysplasia, a low cost multi-spectral colposcope was developed utilizing low costs LEDs and an area scan camera. The device is capable of both traditional colposcopic imaging and multi-spectral image capture. Following initial bench testing, the device was deployed to a gynecology clinic where it was used to image patients in a colposcopy setting. Both traditional colposcopic images and spectral data from patients were uploaded to a cloud server for remote analysis. Multi-spectral imaging ( 30 second capture) took place before any clinical procedure; the standard of care was followed thereafter. If acetic acid was used in the standard of care, a post-acetowhitening colposcopic image was also captured. In analyzing the data, normal and abnormal regions were identified in the colposcopic images by an expert clinician. Spectral data were fit to a theoretical model based on diffusion theory, yielding information on scattering and absorption parameters. Data were grouped according to clinician labeling of the tissue, as well as any additional clinical test results available (Pap, HPV, biopsy). Altogether, N=20 patients were imaged in this study, with 9 of them abnormal. In comparing normal and abnormal regions of interest from patients, substantial differences were measured in blood content, while differences in oxygen saturation parameters were more subtle. These results suggest that optical measurements made using low cost spectral imaging systems can distinguish between normal and pathological tissues.

Simultaneous Monitoring of Vascular Oxygenation and Tissue Oxygen Tension of Breast Tumors Under Hyperbaric Oxygen Exposure

DTIC Science & Technology

2008-04-01

28. Alagoz, T., R. Buller, B. Anderson, K. Terrell , R...and oxygenation Ann . New Acad. Sci. 838 29–45 Chapman J D, Stobbe C C, Arnfield M R, Santus R, Lee J and McPhee M S 1991 Oxygen dependency of tumor

Multi-spectral imaging of oxygen saturation

NASA Astrophysics Data System (ADS)

Savelieva, Tatiana A.; Stratonnikov, Aleksander A.; Loschenov, Victor B.

2008-06-01

The system of multi-spectral imaging of oxygen saturation is an instrument that can record both spectral and spatial information about a sample. In this project, the spectral imaging technique is used for monitoring of oxygen saturation of hemoglobin in human tissues. This system can be used for monitoring spatial distribution of oxygen saturation in photodynamic therapy, surgery or sports medicine. Diffuse reflectance spectroscopy in the visible range is an effective and extensively used technique for the non-invasive study and characterization of various biological tissues. In this article, a short review of modeling techniques being currently in use for diffuse reflection from semi-infinite turbid media is presented. A simple and practical model for use with a real-time imaging system is proposed. This model is based on linear approximation of the dependence of the diffuse reflectance coefficient on relation between absorbance and reduced scattering coefficient. This dependence was obtained with the Monte Carlo simulation of photon propagation in turbid media. Spectra of the oxygenated and deoxygenated forms of hemoglobin differ mostly in the red area (520 - 600 nm) and have several characteristic points there. Thus four band-pass filters were used for multi-spectral imaging. After having measured the reflectance, the data obtained are used for fitting the concentration of oxygenated and free hemoglobin, and hemoglobin oxygen saturation.

Airborne Lidar Measurements of Atmospheric Pressure Made Using the Oxygen A-Band

NASA Technical Reports Server (NTRS)

Riris, Haris; Rodriquez, Michael; Allan, Graham R.; Hasselbrack, William E.; Stephen, Mark A.; Abshire, James B.

2011-01-01

We report on airborne measurements of atmospheric pressure using a fiber-laser based lidar operating in the oxygen A-band near 765 nm and the integrated path differential absorption measurement technique. Our lidar uses fiber optic technology and non-linear optics to generate tunable laser radiation at 765 nm, which overlaps an absorption line pair in the Oxygen A-band. We use a pulsed time resolved technique, which rapidly steps the laser wavelength across the absorption line pair, a 20 cm telescope and photon counting detector to measure Oxygen concentrations.

Wound Healing Essentials: Let There Be Oxygen

PubMed Central

Sen, Chandan K.

2009-01-01

The state of wound oxygenation is a key determinant of healing outcomes. From a diagnostic standpoint, measurements of wound oxygenation are commonly used to guide treatment planning such as amputation decision. In preventive applications, optimizing wound perfusion and providing supplemental O2 in the peri-operative period reduces the incidence of post-operative infections. Correction of wound pO2 may, by itself, trigger some healing responses. Importantly, approaches to correct wound pO2 favorably influence outcomes of other therapies such as responsiveness to growth factors and acceptance of grafts. Chronic ischemic wounds are essentially hypoxic. Primarily based on the tumor literature, hypoxia is generally viewed as being angiogenic. This is true with the condition that hypoxia be acute and mild to modest in magnitude. Extreme near-anoxic hypoxia, as commonly noted in problem wounds, is not compatible with tissue repair. Adequate wound tissue oxygenation is required but may not be sufficient to favorably influence healing outcomes. Success in wound care may be improved by a personalized health care approach. The key lies in our ability to specifically identify the key limitations of a given wound and in developing a multifaceted strategy to specifically address those limitations. In considering approaches to oxygenate the wound tissue it is important to recognize that both too little as well as too much may impede the healing process. Oxygen dosing based on the specific need of a wound therefore seems prudent. Therapeutic approaches targeting the oxygen sensing and redox signaling pathways are promising. PMID:19152646

Oxygen Measurements in Liposome Encapsulated Hemoglobin

NASA Astrophysics Data System (ADS)

Phiri, Joshua Benjamin

Liposome encapsulated hemoglobins (LEH's) are of current interest as blood substitutes. An analytical methodology for rapid non-invasive measurements of oxygen in artificial oxygen carriers is examined. High resolution optical absorption spectra are calculated by means of a one dimensional diffusion approximation. The encapsulated hemoglobin is prepared from fresh defibrinated bovine blood. Liposomes are prepared from hydrogenated soy phosphatidylcholine (HSPC), cholesterol and dicetylphosphate using a bath sonication method. An integrating sphere spectrophotometer is employed for diffuse optics measurements. Data is collected using an automated data acquisition system employing lock-in -amplifiers. The concentrations of hemoglobin derivatives are evaluated from the corresponding extinction coefficients using a numerical technique of singular value decomposition, and verification of the results is done using Monte Carlo simulations. In situ measurements are required for the determination of hemoglobin derivatives because most encapsulation methods invariably lead to the formation of methemoglobin, a nonfunctional form of hemoglobin. The methods employed in this work lead to high resolution absorption spectra of oxyhemoglobin and other derivatives in red blood cells and liposome encapsulated hemoglobin (LEH). The analysis using singular value decomposition method offers a quantitative means of calculating the fractions of oxyhemoglobin and other hemoglobin derivatives in LEH samples. The analytical methods developed in this work will become even more useful when production of LEH as a blood substitute is scaled up to large volumes.

Partial Oxygen Pressure Affects the Expression of Prognostic Biomarkers HIF-1 Alpha, Ki67, and CK20 in the Microenvironment of Colorectal Cancer Tissue.

PubMed

Zhang, Lirong; Hu, Yu; Xi, Ning; Song, Jie; Huang, Wenjing; Song, Shanshan; Liu, Yiting; Liu, Xianying; Xie, Yingjun

2016-01-01

Hypoxia is prognostically important in colorectal cancer (CRC) therapy. Partial oxygen pressure (pO 2 ) is an important parameter of hypoxia. The correlation between pO 2 levels and expression levels of prognostic biomarkers was measured in CRC tissues. Human CRC tissues were collected and pO 2 levels were measured by OxyLite. Three methods for tissue fixation were compared, including formalin, Finefix, and Finefix-plus-microwave. Immunohistochemistry (IHC) staining was conducted by using the avidin-biotin complex technique for detecting the antibodies to hypoxia inducible factor-1 (HIF-1) alpha, cytokeratin 20 (CK20), and cell proliferation factor Ki67. The levels of pO 2 were negatively associated with the size of CRC tissues. Finefix-plus-microwave fixation has the potential to replace formalin. Additionally, microwave treatment improved Finefix performance in tissue fixation and protein preservation. The percentage of positive cells and gray values of HIF-1 alpha, CK20, and Ki67 were associated with CRC development ( P < 0.05). The levels of pO 2 were positively related with the gray values of Ki67 and negatively related with the values of HIF-1 alpha and CK20 ( P < 0.05). Thus, the levels of microenvironmental pO 2 affect the expression of predictive biomarkers HIF-1 alpha, CK20, and Ki67 in the development of CRC tissues.

The Use Of Fluorescence Quenching To Measure Oxygen Concentration

NASA Astrophysics Data System (ADS)

Cox, M. E.; Dunn, B.

1986-01-01

The method of fluorescence quenching is used to measure the concentration of molecular oxygen. The method is rapid, reversible, and does not consume oxygen. The method may provide the basis for a unique biomedical sensor. The key to developing such a device lies in the choice of a fluorophor/polymer composite matrix having the desired optical and transport properties. Experimental results will be presented for certain parameters essential for assessing device development. The properties of interest include the kinetics of fluorescence quenching, the biomolecular rate constants, the temperature dependence of oxygen solubility and diffusivity in the composite matrix, and the oxygen diffusion coefficient. Poly(dimethyl siloxane) [PDMS] was chosen as the polymer host because it is biocompatible, hydrophobic, has a high diffusivity for the simple gases, and is easily bonded to fused silica. 9,10-diphenyl anthracene [9,10-D] was selected since it is readily soluble in a number of organic solvents, has an excitation spectrum in the near UV, an emission spectrum in the visible, a long fluorescence lifetime, and a high quantum yield. When incorporated into PDMS, the optical spectra of 9,10-D does not alter appreciably. The response time of the device is determined by the solution/diffusion kinetics of oxygen in PDMS. The solubility of oxygen in PDMS decreases with increasing temperature and an enthalpy of solution of off = -3.0 kcal/mole. (1) The diffusion of oxyzen in PDMS is found to obey an Arrhenius relation over the temperature range of 5'C to 450C with D = Do exp (-ED/RT) (2) where Do = 0.115 cm2/s (3) and ED = 4.77 kcal/mole. (4) Results of these studies indicate that an appropriate device, based on a fluorophor/polymer composite, for the measurement of oxygen concentration should be sensitive over those ranges which are important for physiological monitoring.

Hyperspectral imaging solutions for brain tissue metabolic and hemodynamic monitoring: past, current and future developments

NASA Astrophysics Data System (ADS)

Giannoni, Luca; Lange, Frédéric; Tachtsidis, Ilias

2018-04-01

Hyperspectral imaging (HSI) technologies have been used extensively in medical research, targeting various biological phenomena and multiple tissue types. Their high spectral resolution over a wide range of wavelengths enables acquisition of spatial information corresponding to different light-interacting biological compounds. This review focuses on the application of HSI to monitor brain tissue metabolism and hemodynamics in life sciences. Different approaches involving HSI have been investigated to assess and quantify cerebral activity, mainly focusing on: (1) mapping tissue oxygen delivery through measurement of changes in oxygenated (HbO2) and deoxygenated (HHb) hemoglobin; and (2) the assessment of the cerebral metabolic rate of oxygen (CMRO2) to estimate oxygen consumption by brain tissue. Finally, we introduce future perspectives of HSI of brain metabolism, including its potential use for imaging optical signals from molecules directly involved in cellular energy production. HSI solutions can provide remarkable insight in understanding cerebral tissue metabolism and oxygenation, aiding investigation on brain tissue physiological processes.

Examiner's finger-mounted fetal tissue oximetry.

PubMed

Kanayama, Naohiro; Niwayama, Masatsugu

2014-06-01

The best way to assess fetal condition is to observe the oxygen status of the fetus (as well as to assess the condition of infants, children, and adults). Previously, several fetal oximeters have been developed; however, no instrument has been utilized in clinical practice because of the low-capturing rate of the fetal oxygen saturation. To overcome the problem, we developed a doctor's finger-mounted fetal tissue oximeter, whose sensor volume is one hundredth of the conventional one. Additionally, we prepared transparent gloves. The calculation algorithm of the hemoglobin concentration was derived from the light propagation analysis based on the transport theory. We measured neonatal and fetal oxygen saturation (StO₂) with the new tissue oximeter. Neonatal StO₂ was measured at any position of the head regardless of amount of hair. Neonatal StO₂ was found to be around 77%. Fetal StO₂ was detected in every position of the fetal head during labor regardless of the presence of labor pain. Fetal StO₂ without labor pain was around 70% in the first stage of labor and around 60% in the second stage of labor. We concluded that our new concept of fetal tissue oximetry would be useful for detecting fetal StO₂ in any condition of the fetus.

Examiner's finger-mounted fetal tissue oximetry

NASA Astrophysics Data System (ADS)

Kanayama, Naohiro; Niwayama, Masatsugu

2014-06-01

The best way to assess fetal condition is to observe the oxygen status of the fetus (as well as to assess the condition of infants, children, and adults). Previously, several fetal oximeters have been developed; however, no instrument has been utilized in clinical practice because of the low-capturing rate of the fetal oxygen saturation. To overcome the problem, we developed a doctor's finger-mounted fetal tissue oximeter, whose sensor volume is one hundredth of the conventional one. Additionally, we prepared transparent gloves. The calculation algorithm of the hemoglobin concentration was derived from the light propagation analysis based on the transport theory. We measured neonatal and fetal oxygen saturation (StO2) with the new tissue oximeter. Neonatal StO was measured at any position of the head regardless of amount of hair. Neonatal StO was found to be around 77%. Fetal StO was detected in every position of the fetal head during labor regardless of the presence of labor pain. Fetal StO without labor pain was around 70% in the first stage of labor and around 60% in the second stage of labor. We concluded that our new concept of fetal tissue oximetry would be useful for detecting fetal StO in any condition of the fetus.

The Rate of Oxygen Utilization by Cells

PubMed Central

Wagner, Brett A.; Venkataraman, Sujatha; Buettner, Garry R.

2011-01-01

The discovery of oxygen is considered by some to be the most important scientific discovery of all time – from both physical-chemical/astrophysics and biology/evolution viewpoints. One of the major developments during evolution is the ability to capture dioxygen in the environment and deliver it to each cell in the multicellular, complex mammalian body -- on demand, i.e. just-in-time. Humans use oxygen to extract approximately 2550 Calories (10.4 MJ) from food to meet daily energy requirements. This combustion requires about 22 moles of dioxygen per day, or 2.5 × 10-4 mol s-1. This is an average rate of oxygen utilization of 2.5 × 10-18 mol cell-1 s-1, i.e. 2.5 amol cell-1 s-1. Cells have a wide range of oxygen utilization, depending on cell type, function, and biological status. Measured rates of oxygen utilization by mammalian cells in culture range from <1 to >350 amol cell-1 s-1. There is a loose positive linear correlation of the rate of oxygen consumption (OCR) by mammalian cells in culture with cell volume and cell protein. The use of oxygen by cells and tissues is an essential aspect of the basic redox biology of cells and tissues. This type of quantitative information is fundamental to investigations in quantitative redox biology, especially redox systems biology. PMID:21664270

Spatiotemporal Oxygen Sensing Using Dual Emissive Boron Dye–Polylactide Nanofibers

PubMed Central

2015-01-01

Oxygenation in tissue scaffolds continues to be a limiting factor in regenerative medicine despite efforts to induce neovascularization or to use oxygen-generating materials. Unfortunately, many established methods to measure oxygen concentration, such as using electrodes, require mechanical disturbance of the tissue structure. To address the need for scaffold-based oxygen concentration monitoring, a single-component, self-referenced oxygen sensor was made into nanofibers. Electrospinning process parameters were tuned to produce a biomaterial scaffold with specific morphological features. The ratio of an oxygen sensitive phosphorescence signal to an oxygen insensitive fluorescence signal was calculated at each image pixel to determine an oxygenation value. A single component boron dye–polymer conjugate was chosen for additional investigation due to improved resistance to degradation in aqueous media compared to a boron dye polymer blend. Standardization curves show that in fully supplemented media, the fibers are responsive to dissolved oxygen concentrations less than 15 ppm. Spatial (millimeters) and temporal (minutes) ratiometric gradients were observed in vitro radiating outward from the center of a dense adherent cell grouping on scaffolds. Sensor activation in ischemia and cell transplant models in vivo show oxygenation decreases on the scale of minutes. The nanofiber construct offers a robust approach to biomaterial scaffold oxygen sensing. PMID:25426706

Biological Oxygen Productivity Over The Last Glacial Termination From Triple Oxygen Isotope Measurements

NASA Astrophysics Data System (ADS)

Blunier, T.; Bender, M. L.; Hendricks, M. B.

The atmospheric oxygen isotope signature of O2 is linked to the oxygen signature of seawater through photosynthesis and respiration. Fractionation during these pro- cesses is mass dependent affecting 17O about half as much as 18O. A mass indepen- dent fractionation process takes place during isotope exchange between O2 and CO2 in the stratosphere (Thiemens, 1999; Luz et al., 1999). The magnitude of the mass- independent anomaly in the triple isotope composition of O2 depends on relative rates of biological O2 cycling and photochemical reactions in the stratosphere. Variations of this anomaly thus allows us to estimate changes of mass dependent O2 production by photosynthesis versus mass independent O2-CO2 exchange in the stratosphere. We reconstruct total oxygen productivity for the past from 17O and 18O measure- ments of O2 trapped in ice cores. With a box model we estimate that the total biogenic productivity was only 76-83 % of today for the glacial and was probably still lower than today during the glacial-interglacial transition and the early Holocene. In principle we can calculate the oxygen flux from the ocean biosphere if we know the oxygen flux from the land biosphere. Calculated ocean production is very sensitive to the estimate of land biosphere production. The latter term remains uncertain, however, and we can presently only constrain glacial ocean production to 88 to 140 % of the present value.

[Intraoperative monitoring of oxygen tissue pressure: Applications in vascular neurosurgery].

PubMed

Arikan, Fuat; Vilalta, Jordi; Torne, Ramon; Chocron, Ivette; Rodriguez-Tesouro, Ana; Sahuquillo, Juan

2014-01-01

Ischemic lesions related to surgical procedures are a major cause of postoperative morbidity in patients with cerebral vascular disease. There are different systems of neuromonitoring to detect intraoperative ischemic events, including intraoperative monitoring of oxygen tissue pressure (PtiO2). The aim of this article was to describe, through the discussion of 4 cases, the usefulness of intraoperative PtiO2 monitoring during vascular neurosurgery. In presenting these cases, we demonstrate that monitoring PtiO2 is a reliable way to detect early ischemic events during surgical procedures. Continuous monitoring of PtiO2 in an area at risk allows the surgeon to resolve the cause of the ischemic event before it evolves to an established cerebral infarction. Copyright © 2014 Sociedad Española de Neurocirugía. Published by Elsevier España. All rights reserved.

Oxygen fugacities directly measured in magmatic gases.

PubMed

Sato, M; Wright, T L

1966-09-02

An electrochemical device was used to measure the fugacity of oxygen (fo(o2)) in holes drilled through the crust of Makaopuhi lava lake, Kilauea Volcano, Hawaii. Results obtained within 6 months of the lake formation show that log fo(o2) normally varies linearly with the reciprocal of the absolute temperature, and that chemical changes occurring in the cooling tholeiitic basalt are reflected in the fo(o2) values measured in the holes.

Pilot study of oxygen transport rate of banked red blood cells.

PubMed

Buchwald, H; Menchaca, H J; Michalek, V N; Rudser, K D; Rohde, T D; O'Dea, T; Connett, J E; Gorlin, J

2009-01-01

Dynamic oximetry provides a new way to assess the effect of blood storage on the oxygen transport rate (OTR). In dynamic oximetry, the rate at which oxyhemoglobin becomes deoxyhemoglobin is measured optically, thereby, indirectly measuring the rate at which oxygen leaves the red blood cell (RBC) making it available for transfer to tissues. Extending the physiologic diffusion time in an in vitro apparatus, consisting of a diffusion system and gas exchanger capable of controlling the surface area and the time of exposure for oxygenation and deoxygenation, makes OTR measurement feasible. Eight normal blood donor units, collected in adenine, dextrose, sorbitol, sodium chloride and mannitol , were stored for 8 weeks under standard conditions and serially sampled for OTR. We report that the OTR at the time of blood bank donation appears to be singular for each donor, that the interdonor differences are maintained over time, and that the individual OTR increased 1.72-fold (95% CI 1.51, 1.95) over 8 weeks, adjusting for sex, age and plasma cholesterol level. Oxygen transport rate increases during storage; blood units with similar haemoglobin content may have significant differences in OTR. Studies examining blood parameters at the time of donation and blood storage on patient outcomes should consider measuring OTR, as it may contribute to differences in observed efficacy of tissue oxygenation.

Oxygen consumption of human heart cells in monolayer culture.

PubMed

Sekine, Kaori; Kagawa, Yuki; Maeyama, Erina; Ota, Hiroki; Haraguchi, Yuji; Matsuura, Katsuhisa; Shimizu, Tatsuya

2014-09-26

Tissue engineering in cardiovascular regenerative therapy requires the development of an efficient oxygen supply system for cell cultures. However, there are few studies which have examined human cardiomyocytes in terms of oxygen consumption and metabolism in culture. We developed an oxygen measurement system equipped with an oxygen microelectrode sensor and estimated the oxygen consumption rates (OCRs) by using the oxygen concentration profiles in culture medium. The heart is largely made up of cardiomyocytes, cardiac fibroblasts, and cardiac endothelial cells. Therefore, we measured the oxygen consumption of human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs), cardiac fibroblasts, human cardiac microvascular endothelial cell and aortic smooth muscle cells. Then we made correlations with their metabolisms. In hiPSC-CMs, the value of the OCR was 0.71±0.38pmol/h/cell, whereas the glucose consumption rate and lactate production rate were 0.77±0.32pmol/h/cell and 1.61±0.70pmol/h/cell, respectively. These values differed significantly from those of the other cells in human heart. The metabolism of the cells that constitute human heart showed the molar ratio of lactate production to glucose consumption (L/G ratio) that ranged between 1.97 and 2.2. Although the energy metabolism in adult heart in vivo is reported to be aerobic, our data demonstrated a dominance of anaerobic glycolysis in an in vitro environment. With our measuring system, we clearly showed the differences in the metabolism of cells between in vivo and in vitro monolayer culture. Our results regarding cell OCRs and metabolism may be useful for future tissue engineering of human heart. Copyright © 2014 Elsevier Inc. All rights reserved.

Spontaneous calcium waves in Bergman glia increase with age and hypoxia and may reduce tissue oxygen.

PubMed

Mathiesen, Claus; Brazhe, Alexey; Thomsen, Kirsten; Lauritzen, Martin

2013-02-01

Glial calcium (Ca(2+)) waves constitute a means to spread signals between glial cells and to neighboring neurons and blood vessels. These waves occur spontaneously in Bergmann glia (BG) of the mouse cerebellar cortex in vivo. Here, we tested three hypotheses: (1) aging and reduced blood oxygen saturation alters wave activity; (2) glial Ca(2+) waves change cerebral oxygen metabolism; and (3) neuronal and glial wave activity is correlated. We used two-photon microscopy in the cerebellar cortexes of adult (8- to 15-week-old) and aging (48- to 80-week-old) ketamine-anesthetized mice after bolus loading with OGB-1/AM and SR101. We report that the occurrence of spontaneous waves is 20 times more frequent in the cerebellar cortex of aging as compared with adult mice, which correlated with a reduction in resting brain oxygen tension. In adult mice, spontaneous glial wave activity increased on reducing resting brain oxygen tension, and ATP-evoked glial waves reduced the tissue O(2) tension. Finally, although spontaneous Purkinje cell (PC) activity was not associated with increased glia wave activity, spontaneous glial waves did affect intracellular Ca(2+) activity in PCs. The increased wave activity during aging, as well as low resting brain oxygen tension, suggests a relationship between glial waves, brain energy homeostasis, and pathology.

In vivo evidence of methamphetamine induced attenuation of brain tissue oxygenation as measured by EPR oximetry

PubMed Central

Weaver, John; Yang, Yirong; Purvis, Rebecca; Weatherwax, Theodore; Rosen, Gerald M.; Liu, Ke Jian

2014-01-01

Abuse of methamphetamine (METH) is a major and significant societal problem in the US, as a number of studies have suggested that METH is associated with increased cerebrovascular events, hemorrhage or vasospasm. Although cellular and molecular mechanisms involved in METH-induced toxicity are not completely understood, changes in brain O2 may play an important role and contribute to METH-induced neurotoxicity including dopaminergic receptor degradation. Given that O2 is the terminal electron acceptor for many enzymes that are important in brain function, the impact of METH on brain tissue pO2 in vivo remains largely uncharacterized. This study investigated striatal tissue pO2 changes in male C57BL/6 mice (16–20g) following METH administration using EPR oximetry, a highly sensitive modality to measure pO2 in vivo, in situ and in real time. We demonstrate that 20 min after a single injection of METH (8 mg/kg i.v.), the striatal pO2 was reduced to 81% of the pretreatment level and exposure to METH for 3 consecutive days further attenuated striatal pO2 to 64%. More importantly, pO2 did not recover fully to control levels even 24 hrs after administration of a single dose of METH. and continual exposure to METH exacerbates the condition. We also show a reduction in cerebral blood flow associated with a decreased brain pO2 indicating an ischemic condition. Our findings suggests that administration of METH can attenuate brain tissue pO2, which may lead to hypoxic insult, thus a risk factor for METH-induced brain injury and the development of stroke in young adults. PMID:24412707

Injectable LiNc-BuO loaded microspheres as in vivo EPR oxygen sensors after co-implantation with tumor cells.

PubMed

Frank, Juliane; Gündel, Daniel; Drescher, Simon; Thews, Oliver; Mäder, Karsten

2015-12-01

Electron paramagnetic resonance (EPR) oximetry is a technique which allows accurate and repeatable oxygen measurements. We encapsulated a highly oxygen sensitive particulate EPR spin probe into microparticles to improve its dispersibility and, hence, facilitate the administration. These biocompatible, non-toxic microspheres contained 5-10 % (w/w) spin probe and had an oxygen sensitivity of 0.60 ± 0.01 µT/mmHg. To evaluate the performance of the microparticles as oxygen sensors, they were co-implanted with syngeneic tumor cells in 2 different rat strains. Thus, tissue injury was avoided and the microparticles were distributed all over the tumor tissue. Dynamic changes of the intratumoral oxygen partial pressure during inhalation of 8 %, 21 %, or 100 % oxygen were monitored in vivo by EPR spectroscopy and quantified. Values were verified in vivo by invasive fluorometric measurements using Oxylite probes and ex vivo by pimonidazole adduct accumulation. There were no hints that the tumor physiology or tissue oxygenation had been altered by the microparticles. Hence, these microprobes offer great potential as oxygen sensors in preclinical research, not only for EPR spectroscopy but also for EPR imaging. For instance, the assessment of tissue oxygenation during therapeutic interventions might help understanding pathophysiological processes and lead to an individualized treatment planning or the use of formulations with hypoxia triggered release of active agents. Copyright © 2015 Elsevier Inc. All rights reserved.

The jumbo squid, Dosidicus gigas (Ommastrephidae), living in oxygen minimum zones I: Oxygen consumption rates and critical oxygen partial pressures

NASA Astrophysics Data System (ADS)

Trueblood, Lloyd A.; Seibel, Brad A.

2013-10-01

Dosidicus gigas is a large, metabolically active, epipelagic squid known to undertake diel vertical migrations across a large temperature and oxygen gradient in the Eastern Pacific. Hypoxia is known to cause metabolic suppression in D. gigas. However, the precise oxygen level at which metabolic suppression sets in is unknown. Here we describe a novel ship-board swim tunnel respirometer that was used to measure metabolic rates and critical oxygen partial pressures (Pcrit) for adult squids (2-7kg). Metabolic rate measurements were validated by comparison to the activity of the Krebs cycle enzyme, citrate synthase, in mantle muscle tissue (2-17kg). We recorded a mean routine metabolic rate of 5.91μmolg-1h-1 at 10°C and 12.62μmolg-1h-1 at 20°C. A temperature coefficient, Q10, of 2.1 was calculated. D. gigas had Pcrits of 1.6 and 3.8kPa at 10 and 20°C, respectively. Oxygen consumption rate (MO2) varied with body mass (M) according to MO2=11.57M-0.12±0.03 at 10°C. Citrate synthase activity varied with body mass according to Y=9.32M-0.19±0.02.

Measurement in a marine environment using low cost sensors of temperature and dissolved oxygen

USGS Publications Warehouse

Godshall, F.A.; Cory, R.L.; Phinney, D.E.

1974-01-01

Continuous records of physical parameters of the marine environment are difficult as well as expensive to obtain. This paper describes preliminary results of an investigative program with the purpose of developing low cost time integrating measurement and averaging devices for water temperature and dissolved oxygen. Measurements were made in an estuarine area of the Chesapeake Bay over two week periods. With chemical thermometers average water temperature for the two week period was found to be equal to average water temperature measured with thermocouples plus or minus 1.0 C. The slow diffusion of oxygen through the semipermiable sides of plastic bottles permitted the use of water filled bottles to obtain averaged oxygen measurements. Oxygen measurements for two week averaging times using 500 ml polyethylene bottles were found to vary from conventionally measured and averaged dissolved oxygen by about 1.8 mg/l. ?? 1974 Estuarine Research Federation.

In vivo mapping of tumor oxygen consumption using (19)F MRI relaxometry.

PubMed

Diepart, Caroline; Magat, Julie; Jordan, Bénédicte F; Gallez, Bernard

2011-06-01

Recently, we have developed a new electron paramagnetic resonance (EPR) protocol in order to estimate tissue oxygen consumption in vivo. Because it is crucial to probe the heterogeneity of response in tumors, the aim of this study was to apply our protocol, together with (19)F MRI relaxometry, to the mapping of the oxygen consumption in tumors. The protocol includes the continuous measurement of tumor po(2) during the following respiratory challenge: (i) basal values during air breathing; (ii) increasing po(2) values during carbogen breathing until saturation of tissue with oxygen; (iii) switching back to air breathing. We have demonstrated previously using EPR oximetry that the kinetics of return to the basal value after oxygen saturation are mainly governed by tissue oxygen consumption. This challenge was applied in hyperthyroid mice (generated by chronic treatment with L-thyroxine) and control mice, as hyperthyroidism is known to dramatically affect the oxygen consumption rate of tumor cells. Our recently developed snapshot inversion recovery MRI fluorocarbon oximetry technique allowed the po(2) return kinetics to be measured with a high temporal resolution. The kinetic constants (i.e. oxygen consumption rates) were higher for tumors from hyperthyroid mice than from control mice, data that are consistent with our previous EPR study. The corresponding histograms of the (19)F MRI data showed that the kinetic constants displayed a shift to the right for the hyperthyroid group, indicating a higher oxygen consumption in these tumors. The color maps showed a large heterogeneity in terms of oxygen consumption rate within a tumor. In conclusion, (19)F MRI relaxometry allows the noninvasive mapping of the oxygen consumption in tumors. The ability to assess the heterogeneity of tumor response is critical in order to identify potential tumor regions that might be resistant to treatment and therefore produce a poor response to therapy. Copyright © 2010 John Wiley & Sons

Osmotic phenomena in application for hyperbaric oxygen treatment.

PubMed

Babchin, A; Levich, E; Melamed M D, Y; Sivashinsky, G

2011-03-01

Hyperbaric oxygen (HBO) treatment defines the medical procedure when the patient inhales pure oxygen at elevated pressure conditions. Many diseases and all injuries are associated with a lack of oxygen in tissues, known as hypoxia. HBO provides an effective method for fast oxygen delivery in medical practice. The exact mechanism of the oxygen transport under HBO conditions is not fully identified. The objective of this article is to extend the colloid and surface science basis for the oxygen transport in HBO conditions beyond the molecular diffusion transport mechanism. At a pressure in the hyperbaric chamber of two atmospheres, the partial pressure of oxygen in the blood plasma increases 10 times. The sharp increase of oxygen concentration in the blood plasma creates a considerable concentration gradient between the oxygen dissolved in the plasma and in the tissue. The concentration gradient of oxygen as a non-electrolyte solute causes an osmotic flow of blood plasma with dissolved oxygen. In other words, the molecular diffusion transport of oxygen is supplemented by the convective diffusion raised due to the osmotic flow, accelerating the oxygen delivery from blood to tissue. A non steady state equation for non-electrolyte osmosis is solved asymptotically. The solution clearly demonstrates two modes of osmotic flow: normal osmosis, directed from lower to higher solute concentrations, and anomalous osmosis, directed from higher to lower solute concentrations. The fast delivery of oxygen from blood to tissue is explained on the basis of the strong molecular interaction between the oxygen and the tissue, causing an influx of oxygen into the tissue by convective diffusion in the anomalous osmosis process. The transport of the second gas, nitrogen, dissolved in the blood plasma, is also taken into the consideration. As the patient does not inhale nitrogen during HBO treatment, but exhales it along with oxygen and carbon dioxide, the concentration of nitrogen in blood

Phenobarbital and neonatal seizures affect cerebral oxygen metabolism: a near-infrared spectroscopy study.

PubMed

Sokoloff, Max D; Plegue, Melissa A; Chervin, Ronald D; Barks, John D E; Shellhaas, Renée A

2015-07-01

Near-infrared spectroscopy (NIRS) measures oxygen metabolism and is increasingly used for monitoring critically ill neonates. The implications of NIRS-recorded data in this population are poorly understood. We evaluated NIRS monitoring for neonates with seizures. In neonates monitored with video-electroencephalography, NIRS-measured cerebral regional oxygen saturation (rSO2) and systemic O2 saturation were recorded every 5 s. Mean rSO2 was extracted for 1-h blocks before, during, and after phenobarbital doses. For each electrographic seizure, mean rSO2 was extracted for a period of three times the duration of the seizure before and after the ictal pattern, as well as during the seizure. Linear mixed models were developed to assess the impact of phenobarbital administration and of seizures on rSO2 and fractional tissue oxygen extraction. For 20 neonates (estimated gestational age: 39.6 ± 1.5 wk), 61 phenobarbital doses and 40 seizures were analyzed. Cerebral rSO2 rose (P = 0.005), and fractional tissue oxygen extraction declined (P = 0.018) with increasing phenobarbital doses. rSO2 declined during seizures, compared with baseline and postictal phases (baseline 81.2 vs. ictal 77.7 vs. postictal 79.4; P = 0.004). Fractional tissue oxygen extraction was highest during seizures (P = 0.002). Cerebral oxygen metabolism decreases after phenobarbital administration and increases during seizures. These small, but clear, changes in cerebral oxygen metabolism merit assessment for potential clinical impact.

Oxygen effects on glucose measurements with a reference analyzer and three handheld meters.

PubMed

Tang, Z; Louie, R F; Payes, M; Chang, K C; Kost, G J

2000-01-01

Oxygen may affect glucose meter and reference analyzer measurements. We evaluated the effects of changes in blood oxygen tension (Po2) on Accu-Chek Comfort Curve (Roche Diagnostics, Indianapolis, IN), Precision G, (Abbott Laboratories, Bedford, MA) and One Touch II (Lifescan, Milpitas, CA) glucose meter measurements, and on Yellow Springs Instruments (YSI) (Yellow Springs, OH) reference analyzer measurements. Venous blood drawn from healthy volunteers was adjusted to three glucose levels of 80, 200, and 400 mg/dL, each tonometered with six different Po2 levels (40, 80, 160, 240, 320, and 400 torr). To quantitate oxygen effects on reference analyzer measurements, glucose differences between test sample (Po2 changed) and control (Po2 80 torr) were calculated (YSItest-YSIcontrol). The threshold for determination of oxygen effects was +/-2 SD, where 2 SD was fro

The measurement of hemoglobin oxygen saturation using multiwavelength photoacoustic microscopy

NASA Astrophysics Data System (ADS)

Deng, Zilin; Yang, Xiaoquan; Yu, Lejun; Gong, Hui

2010-02-01

Hemoglobin oxygen saturation (SO2) is one of the most critical functional parameters to the metabolism. In this paper, we mainly introduced some initial results of measuring blood oxygen using multi-wavelength photoacoustic microscopy (PAM). In phantom study, we demonstrate the photoacoustic signal amplitude increases linearly with the concentration of red or blue ink. Then the calculated concentration of red ink in double-ink mixtures with PAM has a 5% difference with the result measured with spectrophotometric analysis. In ex vivo experiment, the measured result exhibt 15% difference between the PAM and spectrophotometric analysis. Experiment results suggest that PAM could be used to determine the SO2 quantitatively.

In vivo evidence of methamphetamine induced attenuation of brain tissue oxygenation as measured by EPR oximetry

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

Weaver, John, E-mail: jmweaver@salud.unm.edu; Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico Health Sciences Center, Albuquerque, NM 87131; Yang, Yirong

2014-03-01

Abuse of methamphetamine (METH) is a major and significant societal problem in the US, as a number of studies have suggested that METH is associated with increased cerebrovascular events, hemorrhage or vasospasm. Although cellular and molecular mechanisms involved in METH-induced toxicity are not completely understood, changes in brain O{sub 2} may play an important role and contribute to METH-induced neurotoxicity including dopaminergic receptor degradation. Given that O{sub 2} is the terminal electron acceptor for many enzymes that are important in brain function, the impact of METH on brain tissue pO{sub 2}in vivo remains largely uncharacterized. This study investigated striatal tissuemore » pO{sub 2} changes in male C57BL/6 mice (16–20 g) following METH administration using EPR oximetry, a highly sensitive modality to measure pO{sub 2}in vivo, in situ and in real time. We demonstrate that 20 min after a single injection of METH (8 mg/kg i.v.), the striatal pO{sub 2} was reduced to 81% of the pretreatment level and exposure to METH for 3 consecutive days further attenuated striatal pO{sub 2} to 64%. More importantly, pO{sub 2} did not recover fully to control levels even 24 h after administration of a single dose of METH and continual exposure to METH exacerbates the condition. We also show a reduction in cerebral blood flow associated with a decreased brain pO{sub 2} indicating an ischemic condition. Our findings suggests that administration of METH can attenuate brain tissue pO{sub 2}, which may lead to hypoxic insult, thus a risk factor for METH-induced brain injury and the development of stroke in young adults. - Highlights: • Explored striatal tissue pO{sub 2}in vivo after METH administration by EPR oximetry. • pO{sub 2} was reduced by 81% after a single dose and 64% after 3 consecutive daily doses. • pO{sub 2} did not recover fully to control levels even 24 h after a single dose. • Decrease in brain tissue pO{sub 2} may be associated with a

Mechanisms That Modulate Peripheral Oxygen Delivery during Exercise in Heart Failure.

PubMed

Kisaka, Tomohiko; Stringer, William W; Koike, Akira; Agostoni, Piergiuseppe; Wasserman, Karlman

2017-07-01

Oxygen uptake ([Formula: see text]o 2 ) measured at the mouth, which is equal to the cardiac output (CO) times the arterial-venous oxygen content difference [C(a-v)O 2 ], increases more than 10- to 20-fold in normal subjects during exercise. To achieve this substantial increase in oxygen uptake [[Formula: see text]o 2  = CO × C(a-v)O 2 ] both CO and the arterial-venous difference must simultaneously increase. Although this occurs in normal subjects, patients with heart failure cannot achieve significant increases in cardiac output and must rely primarily on changes in the arterial-venous difference to increase [Formula: see text]o 2 during exercise. Inadequate oxygen delivery to the tissue during exercise in heart failure results in tissue anaerobiosis, lactic acid accumulation, and reduction in exercise tolerance. H + is an important regulatory and feedback mechanism to facilitate additional oxygen delivery to the tissue (Bohr effect) and further aerobic production of ATP when tissue anaerobic metabolism increases the production of lactate (anaerobic threshold). This H + production in the muscle capillary promotes the continued unloading of oxygen (oxyhemoglobin desaturation) while maintaining the muscle capillary Po 2 (Fick principle) at a sufficient level to facilitate aerobic metabolism and overcome the diffusion barriers from capillary to mitochondria ("critical capillary Po 2 ," 15-20 mm Hg). This mechanism is especially important during exercise in heart failure where cardiac output increase is severely constrained. Several compensatory mechanisms facilitate peripheral oxygen delivery during exercise in both normal persons and patients with heart failure.

Singlet Oxygen Generation by UVA Light Exposure of Endogenous Photosensitizers

PubMed Central

Baier, Jürgen; Maisch, Tim; Maier, Max; Engel, Eva; Landthaler, Michael; Bäumler, Wolfgang

2006-01-01

UVA light (320–400 nm) has been shown to produce deleterious biological effects in tissue due to the generation of singlet oxygen by substances like flavins or urocanic acid. Riboflavin, flavin mononucleotide (FMN), flavin adenine dinucleotide (FAD), β-nicotinamide adenine dinucleotide (NAD), and β-nicotinamide adenine dinucleotide phosphate (NADP), urocanic acid, or cholesterol in solution were excited at 355 nm. Singlet oxygen was directly detected by time-resolved measurement of its luminescence at 1270 nm. NAD, NADP, and cholesterol showed no luminescence signal possibly due to the very low absorption coefficient at 355 nm. Singlet oxygen luminescence of urocanic acid was clearly detected but the signal was too weak to quantify a quantum yield. The quantum yield of singlet oxygen was precisely determined for riboflavin (ΦΔ = 0.54 ± 0.07), FMN (ΦΔ = 0.51 ± 0.07), and FAD (ΦΔ = 0.07 ± 0.02). In aerated solution, riboflavin and FMN generate more singlet oxygen than exogenous photosensitizers such as Photofrin, which are applied in photodynamic therapy to kill cancer cells. With decreasing oxygen concentration, the quantum yield of singlet oxygen generation decreased, which must be considered when assessing the role of singlet oxygen at low oxygen concentrations (inside tissue). PMID:16751234

Sequential weighted Wiener estimation for extraction of key tissue parameters in color imaging: a phantom study

NASA Astrophysics Data System (ADS)

Chen, Shuo; Lin, Xiaoqian; Zhu, Caigang; Liu, Quan

2014-12-01

Key tissue parameters, e.g., total hemoglobin concentration and tissue oxygenation, are important biomarkers in clinical diagnosis for various diseases. Although point measurement techniques based on diffuse reflectance spectroscopy can accurately recover these tissue parameters, they are not suitable for the examination of a large tissue region due to slow data acquisition. The previous imaging studies have shown that hemoglobin concentration and oxygenation can be estimated from color measurements with the assumption of known scattering properties, which is impractical in clinical applications. To overcome this limitation and speed-up image processing, we propose a method of sequential weighted Wiener estimation (WE) to quickly extract key tissue parameters, including total hemoglobin concentration (CtHb), hemoglobin oxygenation (StO2), scatterer density (α), and scattering power (β), from wide-band color measurements. This method takes advantage of the fact that each parameter is sensitive to the color measurements in a different way and attempts to maximize the contribution of those color measurements likely to generate correct results in WE. The method was evaluated on skin phantoms with varying CtHb, StO2, and scattering properties. The results demonstrate excellent agreement between the estimated tissue parameters and the corresponding reference values. Compared with traditional WE, the sequential weighted WE shows significant improvement in the estimation accuracy. This method could be used to monitor tissue parameters in an imaging setup in real time.

Dual-wavelength photothermal optical coherence tomography for blood oxygen saturation measurement

NASA Astrophysics Data System (ADS)

Yin, Biwei; Kuranov, Roman V.; McElroy, Austin B.; Milner, Thomas E.

2013-03-01

We report design and demonstration of a dual wavelength photothermal (DWP) optical coherence tomography (OCT) system for imaging of a phantom microvessel and measurement of hemoglobin oxygen saturation (SO2) level. The DWP-OCT system contains a swept-source (SS) two-beam phase-sensitive (PhS) OCT system (1060 nm) and two intensity modulated photothermal excitation lasers (770 nm and 800 nm). The PhS-OCT probe beam (1060 nm) and photothermal excitation beams are combined into one single-mode optical fiber. A galvanometer based two-dimensional achromatic scanning system is designed to provide 14 μm lateral resolution for the PhS-OCT probe beam (1060 nm) and 13 μm lateral resolution for photothermal excitation beams. DWP-OCT system's sensitivity is 102 dB, axial resolution is 13 μm in tissue and uses a real-time digital dispersion compensation algorithm. Noise floor for optical pathlength measurements is 300 pm in the signal frequency range (380-400 Hz) of photothermal modulation frequencies. Blood SO2 level is calculated from measured optical pathlength (op) signal in a 300 μm diameter microvessel phantom introduced by the two photothermal excitation beams. En-face and B-scan images of a phantom microvessel are recorded, and six blood samples' SO2 levels are measured using DWP-OCT and compared with values provided by a commercial blood oximeter. A mathematical model indicates thermal diffusion introduces a systematic artifact that over-estimates SO2 values and is consistent with measured data.