PO2 Values Research Articles

Caffeine administered to pregnant sows improves piglet vitality, gas exchange and body weight gain

Intra-partum asphyxia is the most common non-infectious etiology limiting the performance of neonate piglets. Previous studies indicate caffeine (orally and subcutaneously) reverses the effects of intra-partum asphyxia in neonate piglets. In this study, there was investigation of whether use of a novel therapeutic protocol for administering caffeine subcutaneously to pregnant sows would improve the newborn piglets’ vitality, physio-metabolic profiles and body weight gain. Sows were randomly divided into two groups (n = 10 each). Caffeine or NaCl 0.9% was administered 2 days pre-farrowing. Physio-metabolic profiles were measured using blood from the anterior vena cava. The vitality of piglets was evaluated immediately after birth. Piglets (n = 180) were weighed at birth and on days 7, 14 and 21 of lactation. Caffeine positively affected the vitality of the piglets, as indicated by greater vitality scores than that for the control group (8.72 ± 0.12 compared with 7.28 ± 0.16, P < 0.001). Metabolic values were similar between groups, but pO2 values were greater in the piglets with greater vitality scores treated with caffeine (19.10 ± 0.82 compared with 14.49 ± 1.42, P < 0.01), indicating increased respiratory rates. Body weight gain at day 21 was greater in the piglets treated with caffeine that had greater vitality scores than the control piglets having greater vitality scores (6.87 ± 0.18 compared with 6.52 ± 0.25 kg, P < 0.05). Caffeine administration before birth improves the vitality and respiratory capacity of piglets, increasing their adaptation to extra-uterine environment.

Implantable microchip containing oxygen-sensing paramagnetic crystals for long-term, repeated, and multisite in vivo oximetry.

EPR oximetry is established as a viable method for measuring the tissue oxygen level (partial pressure of oxygen, pO2) in animal models; however, it has not yet been established for measurements in humans. EPR oximetry requires an oxygen-sensing paramagnetic probe (molecular or particulate) to be placed at the site/organ of measurement, which may pose logistical and safety concerns, including invasiveness of the probe-placement procedure as well as lack of temporal stability and sensitivity for long-term (repeated) measurements, and possible toxicity in the short- and long-term. In the past, we have developed an implantable oxygen-sensing probe, called OxyChip, which we have successfully established for oximetry in pre-clinical animal models (Hou et al. Biomed. Microdevices 20, 29, 2018). Currently, OxyChip is being evaluated in a limited clinical trial in cancer patients. A major limitation of OxyChip is that it is a large (1.4mm3) implant and hence not suitable for measuring oxygen heterogeneity that may be present in solid tumors, chronic wounds, etc. In this report, we describe the development of a substantially smaller version of OxyChip (0.07mm3 or 70 cubic micron), called mChip, that can be placed in the tissue of interest using a 23G syringe-needle with minimal invasiveness. Using in vitro and in vivo models, we have shown that the microchip provides adequate EPR sensitivity, stability, and biocompatibility and thus enables robust, repeated, and simultaneous measurement from multiple implants providing mean and median pO2 values in the implanted region. The mChips will be particularly useful for those applications that require repeated measurements of mean/median pO2 in superficial tissues and malignancies.

How parameter specification of an Earth system model of intermediate complexity influences its climate simulations

Earth system models (ESMs) consist of parameterization schemes based on one’s perception of how the Earth system functions. A typical ESM contains a large number of parameters (i.e., the constants and exponents in the parameterization schemes) whose specification can have a significant impact on an ESM’s simulation capabilities. Sensitivity analyses (SA) is an important tool for assessing how parameter specification influences model simulations. In this study, we used an Earth system model of intermediate complexity (EMIC)—LOVECLIM as an example to illustrate how SA methods can be used to identify the most sensitive parameters that control the simulations of several key global water and energy cycle variables, including global annual mean absolute surface air temperature (TG), precipitation and evaporation over the land and over the oceans (PL, PO, EL, EO), and land runoff (RL). We also demonstrate how judiciously specifying model parameters can improve the simulations of those variables. Three SA methods MARS, RF, and sparse PCE-based Sobol’ method were used to evaluate a pool of 25 adjustable parameters chosen from land, atmosphere, and ocean components of LOVECLIM and their results were intercompared to ensure robustness of the results. It is found that with different parameter specification, TG can vary from 10 to 20 °C, and the values of PL, PO, EL, and EO can change by more than 100%. An interesting observation is that the value of RL vary from 13,000 to 35,000 km3, far below the observed climatological value of 40,000 km3, indicating a model structural deficiency in representing land runoff by LOVECLIM which must be corrected to obtain more reasonable global water budgets. We also note that parameter sensitivities are significantly different at different latitudes. Finally, we showed that global water and energy cycle simulations can be significantly improved by even a crude automatic parameter tuning, indicating that parameter optimization can be a viable way to improve ESM climate simulations. The results from this study should help us to understand the parameter uncertainty of a full-scale ESM.

Real-time Monitoring of Cerebral Blood Flow and Cerebral Oxygenation During Rapid Ventricular Pacing in Neurovascular Surgery: A Pilot Study

Rapid ventricular pacing (RVP) can be used to produce short periods of flow arrest during dissection or rupture of a cerebral aneurysm but carries the risk of inducing cerebral ischemia. This study evaluates the intraoperative effect of RVP on local cerebral blood flow (CBF) and cerebral oxygenation during neurovascular surgery. Five patients undergoing elective cerebrovascular surgery were included in a single-center prospective study. RVP was applied in pacing periods of 40 seconds with 30% and 100% FiO2. Regional cerebral oxygenation was monitored using a Foresight near-infrared spectroscopy sensor. A Clark-type electrode and a thermal diffusion microprobe located in the white matter were used to monitor brain tissue pO2 and CBF, respectively. CBF response to RVP closely followed the blood pressure pattern and resulted in a low-flow state. Unlike CBF, brain tissue pO2 and regional cerebral oxygenation showed a delayed response to RVP, decreasing beyond the pacing period and slowly recovering after RVP cessation. We found a correlation between brain tissue pO2 and regional cerebral oxygenation. Increasing the inspired oxygen concentration had a positive impact on absolute regional cerebral oxygenation and brain tissue pO2 values, but the pattern resulting from applying RVP remained unaltered. RVP reduces CBF and cerebral oxygenation. Brain tissue pO2 and regional cerebral oxygenation are correlated but unlike CBF respond to RVP in a delayed manner. Further research is required to evaluate the impact of longer RVP bursts on brain oxygenation.

Is body mass index a risk factor for low cerebral oxygenation during spinal anesthesia in women undergoing cesarean section? A preliminary study

Background/aim In this study, it was aimed to investigate the relationship between body mass index (BMI) and cerebral oxygenation during spinal anesthesia in women undergoing cesarean section. This study also aimed to demonstrate whether fetal cord blood oxygenation was affected by maternal BMI and/or delivery time.Materials and methods The study included parturients with ASA I score undergoing cesarean section under spinal anesthesia in 2015 and 2016. They were divided into two groups according to BMI: Group 1 comprised parturients with BMI of <30 (n = 11) and Group 2 comprised parturients with BMI of ≥30 (n = 17). Right cerebral oxygenation (RSO2) and left cerebral oxygenation (LSO2) monitoring was performed using near-infrared spectroscopy (NIRS). The participants were divided into two groups according to the duration of fetal delivery. Group A included parturients with delivery time of <2 min (n = 7) and Group B those with delivery time of >2 min (n = 18), and fetal cord blood oxygenation was measured using a blood gas analyzer.Results Evaluation was made of a total of 25 patients. The RSO2 values were​​ measured at the 20th, 30th, and 35th minutes of the cesarean section procedure and the median values of all the time intervals in Group 1 were significantly lower than those of Group 2 (P < 0.05). The LSO2 value ​​was significantly lower in Group 1 at the 35th minute compared to Group 2 (P < 0.05). The PO2 values of fetal cord blood were significantly lower in Group B (P < 0.05). Conclusion The results of this study showed that parturients with BMI of <30 who are undergoing cesarean section under spinal anesthesia might have an increased risk of complications due to decreased cerebral oxygenation related with hypotension. Therefore, it can be suggested that before and during cesarean section these patients should be closely monitored for cerebral oxygenation using NIRS.

New Synthetic Methods of Novel Nanoporous Polycondensates and Excellent Oxygen Permselectivity of Their Composite Membranes.

Two kinds of novel nanoporous polycondensates (sc(Rf)) have been synthesized by two new preparation methods consisting of polycondensation and highly selective photocyclicaromataization of 1/3 helical cis-cis polyphenylacetylenes with polymerizable groups. By the original methods, new well-defined sheet polymers having nanopores or nanospaces have been synthesized for the first time. Their composite membranes, containing small amounts (1.0 wt%) of sc(Rf), had ultrahigh oxygen permeability (Po2 > 1000 barrer), and their plots were beyond the Robeson’s upper bound line in the graph of oxygen permselectivity (α = Po2/PN2) versus Po2. Both α and Po2 values were enhanced by adding only small amounts (1.0 wt%) of sc(Rf). One of the sc(Rf)s synthesized on the base membrane surface showed the best performance, i.e., Po2 = 5300 barrer and α = 2.5. The membrane surface was effectively covered by sc(Rf), judging from the contact angle values. It is thought that nanopores and nanospaces created in and between sc(Rf) molecules played an important role for the enhancement of both α and Po2/PN2.

Comparison of Systemic Effects of Midazolam, Ketamine, and Isoflurane Anaesthesia in Rabbits.

IntroductionClinical doses of anaesthetic agents were administered to rabbits and effects on the brain, heart, and liver were investigated biochemically and histopathologically.Material and MethodsThe rabbits were randomly divided into three main groups (16 rabbits each) and each group into study (n = 8) and control (n = 8) groups. All study group rabbits received 3 mg/kg of midazolam (M) intramuscularly. Group 1.1 (M) received nothing further, group 2.1 (MK) also received 25 mg/kg of ketamine, and group 3.1 (MKI) besides ketamine was also given 2% isoflurane to induce anaesthesia for 30 min. NaCl solution in the same volume as midazolam and ketamine was injected into the controls.ResultsIn clinical evaluation significant differences were detected in respiratory and heart rates. In blood gas analysis the PO2 and PCO2 values showed statistical differences in anaesthesia intervals. Significant biochemical value changes were recorded in creatine kinase-Mb, glucose, and total protein. Histopathological liver examinations revealed higher total apoptotic and normal cell numbers in the MK than in the M and MKI groups. Apoptotic cell numbers were statistically significant in M and MK groups.ConclusionAnaesthetic agents may increase programmed apoptosis. The MKI anaesthetics combination was found to cause less cell destruction in general than the other study groups. It was indicated that MKI was the safer anaesthetic combination in rabbits.

Acoustic droplet vaporization with microfluidic droplets results in dissolved oxygen scavenging

Acoustic droplet vaporization (ADV) is the ultrasound-mediated phase transitioning of liquid perfluoropentane (PFP) droplets into gas microbubbles resulting in dissolved oxygen scavenging from the surrounding fluid. The objective of this study was to determine how droplet diameter influences oxygen scavenging. Droplets of 12 μm and 6 μm diameters were manufactured using a microfluidic system, which were diluted in saline to obtain concentrations of 0.48 Χ 10-3 ± 0.12 Χ 10-3 ml/ml and 1.11 Χ 10-3 ± 0.13 Χ 10-3ml/ml, respectively. Samples were pumped through a 37 °C flow phantom at 10 ml/min. A 5 MHz transducer insonified droplets at 5 MPa for 20 cycles with a 500 Hz repetition frequency. Oxygen partial pressure (Po2) was measured with a distal sensor. Samples of 12 μm and 6 μm droplets had an average volume-weighted transition efficiency of 5.8% ± 4.5% and 5.3% ± 4.6%, respectively. The initial Po2 was 169 ± 7 mmHg for all samples. ADV with 12 μm and 6 μm droplets reduced the Po2 to 113 ± 21 mmHg and 101 ± 9 mmHg, respectively. An oxygen scavenging model based on the PFP phase transitioned volume yielded a final Po2 of 121 ± 27 mmHg for 12 μm droplets and 106 ± 29 mmHg for 6 μm droplets. There was no statistically significant difference (p > 0.05) between the experimentally measured and modeled Po2 values after ADV.

Is the teleost heart oxygen limited? – Insights using “hyperoxic” incubations of contracting cardiac tissue from rainbow trout

Considerable effort has been devoted to understanding the negative effects of reduced PO2 on cardiac function. Much less is known about the impacts of elevated PO2 (hyperoxia) on cardiac performance and energetics, especially in fishes. The fish heart is of particular interest because cardiac dependence on oxygen is extremely variable between species and the early evolution of fish occurred when atmospheric PO2 was higher than current conditions. Although extracellular PO2 is variable and normally does not exceed 21 kPa, recent evidence suggests that teleost cardiac function is stimulated at supraphysiological PO2 values. The purpose of this study was to address whether cardiac contractility and energy metabolism is responsive to elevated PO2 values in sexually-immature female rainbow trout. Isometric force development (contractility) and oxygen consumption (V̇O2) were recorded in electrically-paced ventricular preparations. Contractility and V̇O2decreased when superfusate PO2 was decreased from ~70 kPa to 57 kPa or 45 kPa. However, PO2 calculated at the preparation core was always above 18 kPa. This estimate, along with complete recovery of contractility and V̇O2 at ~70 kPa, suggests that decreases observed in cardiac performance were not due to tissue hypoxia at the lower PO2 levels. In conclusion, the heart of female rainbow trout may be oxygen-limited in vitro and this study raises new questions about the choice of appropriate PO2 for experimentation, the relevance of elevated and varying PO2 to measurements of cardiac performance, and the possible existence of an oxygen sensor within rainbow trout cardiomyocytes.

Comparison of arterial and venous blood gases in patients with obesity hypoventilation syndrome and neuromuscular disease.

OBJECTIVES:Obesity hypoventilation syndrome (OHS) and some neuromuscular diseases (NMD) present with hypercapnic respiratory failure. Arterial blood gas (ABG) analysis is important in the diagnosis, follow-up, and treatment response of these diseases. However, ABG sampling is difficult in these patients because of excessive subcutaneous fat tissue, muscle atrophy, or contracture. The aim of this study is to investigate the value of venous blood gas (VBG), which is an easier and less complicated method, among stable patients with OHS and NMD.METHODS:The study included stable OHS and NMD patients who had been previously diagnosed and followed up between March 2017 and May 2017 in the outpatient clinic. ABG was taken from all patients in room air, and peripheral VBG was taken within 5 min after ABG sampling.RESULTS:Thirty-six patients with OHS and 46 patients with NMD were included in the study. There was a moderate positive correlation between arterial and venous pH values for all patients (rs = 0.590, P < 0.001). There were a strong and very strong positive correlations between arterial and venous pCO2 and HCO3 values (rs = 0.725 and rs = 0.934, respectively) (P < 0.001). There was no correlation between arterial and venous pO2 and saturation values. There was an agreement in Bland–Altman method for the values of ABG and VBG (pH, pCO2, and HCO3).CONCLUSIONS:There was a correlation between ABG and VBG values (pH, pCO2, and HCO3). VBG parameters (pH, pCO2, and HCO3) can be used safely instead of ABG parameters which have many risks, during treatment and follow-up of patients with OHS and NMD.

Evaluation of the i-STAT Blood Gas Analysis System in Cardiovascular Surgery

The aim of this study was toinvestigate the compatibility of the parameters measured with the i-STAT blood gas analyser and the conventional blood gas analyser Rapid Point 500 (Siemens Healthcare Diagnostics, USA) in patients who underwent cardiovascular surgery. This clinical study included fifty patients undergoing coronary artery bypass surgery. Fifty whole blood samples were portioned and measured on the i-STAT and RP500 laboratory analyzers. The compatibility between pH, pCO2, pO2, Hb, Na+, K+, iCa2+ and glucose values was investigated.There was a good correlation of the i-STAT analyser with the RP500 analyser, with the exception Hb and Na+. Also all parameters except for Hb and ionized calcium were found to be within acceptable range in terms of clinical decision limits. It is very important that the point-of-care devices give accurate results as well as quick results. For this reason, we absolutely think that the point of care devices should be subjected to external and internal quality control programs, users should be trained regularly and feedback studies should be done.

Non-invasive Evaluation of Neonatal Cerebral Status in the Newborns of Mothers Addicted to Alcohol and Drugs

The present study aims to assess the effects of alcohol and drug consumption on the cerebral status of a newborn with risk. Although there is a vast literature on the quality of life in terms of health, there is no uniform point of view, since the well-being of a person implies other elements that consider not only health but also the economic and educational environment in which the individual evolves and often these factors are connected. Besides, there is no valid instrument for measuring the quality of life either for an adult or for a child. In most cases, alcohol consumption intensifies in time, significantly decresing the quality of life for the mother and especially for the conception product. The study focuses on showing the The study focuses on highlighting the psychosocial and pharmacological aspects relevant to the diagnosis and management of neonatal cerebral status. The study participants, whose responses were the base for the quantitative analyzes, were individually interviewed using a standardized interview protocol. The interviews were conducted between October 2015 and September 2017. The interview protocol included three sections, in this chapter focusing our attention on the following sections: a) socio-demographic characteristics: age of gestation, sex of the newborn; b) clinical data: Presentation, Weight at Birth, Apgar Score, Cerebral Saturation (rSO2), Peripheral saturation (SpO2), The extraction fraction (FTOE), Parameters harvested from the umbilical cord at birth (pH, Base excess (BE), pCO2, pO2, MetHb, COHb), c) risk profile: mother�s alcohol consumption, including during pregnancy and drug use. The study group consisted of 90 infants born full term in Elena Doamna Maternity Hospital in Iasi, between 2015-2017, included in the programme of follow-up of the newborn with risk with the purpose of performing an non-invasive assessment of the fetal and neonatal cerebral status, in order to prevent and establish treatment methods for perinatal asphyxia. Based on the information obtained through the preliminary documentation, 30 newborns with alcohol and / or drug-consuming mothers and 60 neonates with risk-free mothers were selected - the control batch, who accepted to participate in the study.The cases studied showed the homogeneity of the groups depending on the mother�s age and gestational age, as well as the sex of the newborn and the weight at birth (p]0.05). In neonates from mothers at risk, the under-reference level of 1-minute brain saturation, combined with a lower gestational age and the 62.5% probability of performing a caesarean section at low levels of cerebral saturation was noted in 66.7% of newborns.The cut off value of SpO2, was established at 70 mL/ 100g/1 min, with a sensitivity of 50.9% and a specificity of 51.3%, after reading the coordinates of ROC curve, but the prediction was not significant from the statistical point of view (p=0.670). The mean level of base excess was al excesului de baze was slightly lower in newborns with the extraction fraction below the cut off value (-4.64 vs -4.18; p=0.560). According to the cases studied, 1 min after birth, 23.3% of the newborns showed an increased level of pCO2 associated with a reduced level of peripheral saturation (r= -0.231; p=0.05). The correlation between the pO2 level and the cerebral saturation, recorded 1 min after birth, was direct, but reduced as intensity (r= +0.295; p=0.049). About 27% of the newborns associated increased values of pO2 with reduced values of the extraction fraction (r=-0.272; p=0.047). The newborns with an extraction fraction over the cut off value had a level of COHb below 1% (p=0.756) more frequently. Newborns from mothers who have consumed alcohol and / or drugs, including during pregnancy, show a reduced level of cerebral saturation and peripheral saturation 1 minute after birth. In 16.7% of newborns, the extraction limit was below the baseline 1 minute after birth.

Role of signaling pathway of long non-coding RNA growth arrest-specific transcript 5/microRNA-200c-3p/angiotensin converting enzyme 2 in the apoptosis of human lung epithelial cell A549 in acute respiratory distress syndrome

Objective: To investigate whether long non-coding RNA (lncRNA) growth arrest-specific transcript 5 (GAS5)/microRNA-200c-3p/angiotensin converting enzyme 2(ACE2) involved in the regulation of the apoptosis of human lung epithelial cell A549 in acute respiratory distress syndrome (ARDS). Methods: ARDS rat models were established and were divided into control, ARDS, ARDS+ pcDNA and ARDS+ pcDNA-GAS5 groups. Six hours after the establishment of ARDS rat model, arterial blood and lung tissues of the rats from the four groups were collected. The changes of partial pressure of oxygen (PO(2)) and partial pressure of CO(2) (PCO(2)) were analyzed and the expression of GAS5 in lung tissue was observed in these groups. Then, A549 cells were divided into control, lipopolysaccharide (LPS), LPS+ pcDNA, LPS+ pcDNA-GAS5, LPS+ pcDNA-GAS5+ pre-NC, LPS+ pcDNA-GAS5+ miR-200c-3p mimic groups. Quantitative real-time PCR (qRT-PCR) was conducted to measure lncRNA GAS5, ACE2 and miR-200c-3p levels. RNA immunoprecipitation and RNA pull-down assay were used to detect the combination between GAS5 and miR-200c-3p. Western blotting was used to detect the protein level of ACE2. Flow cytometry was used to observe the apoptosis of A549 cells in those groups. The data between groups were compared by t test. Results: In ARDS rat model, PO(2) value was significantly increased in ARDS+ pcDNA-GAS5 group than that in ARDS+ pcDNA group[(81.5±3.3) vs (57.5±5.1) mmHg, t=4.850, P<0.05], and PCO(2) value was significantly decreased in ARDS+ pcDNA-GAS5 group than that in ARDS+ pcDNA group[(50.6±1.9) vs (64.0±1.9) mmHg, t=5.940, P<0.05]. LncRNA GAS5 level in A549 cells of LPS group decreased significantly than that in control group (0.43±0.01 vs 1.01±0.01, t=0.242, P<0.05). Compared with LPS+ pcDNA group, ACE2 expression increased significantly in LPS+ pcDNA-GAS5 group (0.85±0.04 vs 0.34±0.02, t=1.800, P<0.05). Compared with LPS+ pcDNA-GAS5+ pre-NC group, ACE2 expression decreased significantly in LPS+ pcDNA-GAS5+ miR-200c-3p mimic group (0.62±0.01 vs 0.84±0.02, t=9.440, P<0.05). Compared with control group, the percentage of A549 cell apoptosis promoted significantly in LPS group (25.90±0.61 vs 7.90±0.22, t=0.257, P<0.05). Compared with LPS+ pcDNA group, the percentage of A549 cell apoptosis suppressed significantly in LPS+ pcDNA-GAS5 group (10.50±0.37 vs 26.37±0.45, t=1.760, P<0.05). Compared with LPS+ pcDNA-GAS5+ pre-NC group, the percentage of A549 apoptosis promoted significantly in LPS+ pcDNA-GAS5+ miR-200c-3p mimic group (19.07±0.56 vs 10.87±0.26, t=0.643, P<0.05). Conclusion: In ARDS, down-regulation of lncRNA GAS5 decreases ACE2 expression through increasing miR-200c-3p to promote the apoptosis of A549 cells, thus to promote the progression of ARDS.

Systemic Oxygen Transport with Rest, Exercise, and Hypoxia: A Comparison of Humans, Rats, and Mice.

The objective of this article is to compare and contrast the known characteristics of the systemic O2 transport of humans, rats, and mice at rest and during exercise in normoxia and hypoxia. This analysis should help understand when rodent O2 transport findings can-and cannot-be applied to human responses to similar conditions. The O2 -transport system was analyzed as composed of four linked conductances: ventilation, alveolo-capillary diffusion, circulatory convection, and tissue capillary-cell diffusion. While the mechanisms of O2 transport are similar in the three species, the quantitative differences are naturally large. There are abundant data on total O2 consumption and on ventilatory and pulmonary diffusive conductances under resting conditions in the three species; however, there is much less available information on pulmonary gas exchange, circulatory O2 convection, and tissue O2 diffusion in mice. The scarcity of data largely derives from the difficulty of obtaining blood samples in these small animals and highlights the need for additional research in this area. In spite of the large quantitative differences in absolute and mass-specific O2 flux, available evidence indicates that resting alveolar and arterial and venous blood PO2 values under normoxia are similar in the three species. Additionally, at least in rats, alveolar and arterial blood PO2 under hypoxia and exercise remain closer to the resting values than those observed in humans. This is achieved by a greater ventilatory response, coupled with a closer value of arterial to alveolar PO2 , suggesting a greater efficacy of gas exchange in the rats. © 2018 American Physiological Society. Compr Physiol 8:1537-1573, 2018.

Intraoperative partial pressure of oxygen measurement to predict flap survival.

Introduction:Flap monitoring using partial pressure of oxygen (pO2) is a proven modality. Instruments needed are expensive and are not readily available to a clinician. Here, pO2 of flap has been determined using readily available and cheap methods, and a cut-off value is calculated which helps in predicting flap outcome.Methods and Results:Total 235 points on 84 skin flaps were studied. Capillary blood was collected from flap and fingertip using 1-ml syringes after at least 30 min of flap inset, and pO2 analysed using blood gas analyser. Fall/change of pO2 (difference of mean of pO2 [diff-pO2]) was also calculated by subtracting the flap pO2 from the finger pO2. Flap was monitored clinically in post-operative period and divided into two groups depending on its survival with Group 1 – dead points and Group 2 – alive points. pO2 and diff-pO2 amongst both the groups were compared and found to be statistically different (P = 0.0001). Cut-off value calculated for pO2 was found to be <86.3 mmHg with a sensitivity of 100% and specificity of 89.05%. The difference of >68.503 mmHg of flap pO2 compared from finger pO2 was calculated as a cut-off with sensitivity of 94.12 and specificity of 79.60%.Conclusions:Flap areas having intra-operative pO2 value <86.3 mmHG have higher chances (60.71%) of getting necrosis later. Similarly, if diff-pO2 compared to fingertip is >68.5 mmHg, chances of those points getting necrosed in post-operative period are high.

Comparison of methods of chemical loop gain measurement during tidal ventilation in awake healthy subjects.

The loop gain (LG) is defined as the ratio of a ventilatory response over the perturbation in ventilation, and it is used to analyze ventilatory control stability. The LG can be derived from minute ventilation (V̇e), end-tidal Pco2 ([Formula: see text]), and end-tidal Po2 ([Formula: see text]) values. Several methods of LG assessment have been developed, which have never been compared. We evaluated the computability, the short-term repeatability, and the agreement of six published (or slightly modified) models for LG determination. These models included three unconstrained autoregressive models, univariate (V̇e), bivariate (V̇e, [Formula: see text]), and trivariate (V̇e, [Formula: see text], and [Formula: see text]), and three analytical transfer function constrained models based on V̇e, V̇e and CO2-sensitivity, and V̇e and central and peripheral CO2 sensitivities, respectively. The models were tested with tidal breathing data in 37 awake healthy subjects (median age 35 yr; 23 women, 14 men). Modeling failed in 11, 0, and 0 subjects for the three unconstrained models, respectively, and 4, 1, and 9 subjects for the three constrained models, respectively. Bland and Altman analyses of the LG values in the medium frequency range of two separate recordings demonstrated good repeatability for four models, excluding univariate and trivariate unconstrained models. The four repeatable models gave LG values that were in agreement (medium frequency LG, median 0.100-0.210), although the constrained model based on V̇e systematically overestimated LG values. The variances explained by these models were ∼20%. In conclusion, model-based analyses of tidal breathing were performed with different approaches that gave comparable results for chemical LG and explained variance.NEW & NOTEWORTHY Several methods of chemical loop gain measurement have been published but never compared. We show that a better repeatability is obtained with analytical constrained models compared with autoregressive unconstrained models and that the repeatable models gave comparable results of loop gain, even if the calculation based on ventilation-only recording gave higher values than those obtained with both ventilation and end-tidal Pco2 recording. The explained variance of ventilation was similar whatever the model.

Nitrous oxide from chemodenitrification: A possible missing link in the Proterozoic greenhouse and the evolution of aerobic respiration.

The potent greenhouse gas nitrous oxide (N2 O) may have been an important constituent of Earth's atmosphere during Proterozoic (~2.5-0.5Ga). Here, we tested the hypothesis that chemodenitrification, the rapid reduction of nitric oxide by ferrous iron, would have enhanced the flux of N2 O from ferruginous Proterozoic seas. We empirically derived a rate law, , and measured an isotopic site preference of +16‰ for the reaction. Using this empirical rate law, and integrating across an oceanwide oxycline, we found that low nM NO and μM-low mM Fe2+ concentrations could have sustained a sea-air flux of 100-200 Tg N2 O-Nyear-1 , if N2 fixation rates were near-modern and all fixed N2 was emitted as N2 O. A 1D photochemical model was used to obtain steady-state atmospheric N2 O concentrations as a function of sea-air N2 O flux across the wide range of possible pO2 values (0.001-1 PAL). At 100-200 Tg N2 O-Nyear-1 and >0.1 PAL O2 , this model yielded low-ppmv N2 O, which would produce several degrees of greenhouse warming at 1.6ppmv CH4 and 320ppmv CO2 . These results suggest that enhanced N2 O production in ferruginous seawater via a previously unconsidered chemodenitrification pathway may have helped to fill a Proterozoic "greenhouse gap," reconciling an ice-free Mesoproterozoic Earth with a less luminous early Sun. A particularly notable result was that high N2 O fluxes at intermediate O2 concentrations (0.01-0.1 PAL) would have enhanced ozone screening of solar UV radiation. Due to rapid photolysis in the absence of an ozone shield, N2 O is unlikely to have been an important greenhouse gas if Mesoproterozoic O2 was 0.001 PAL. At low O2 , N2 O might have played a more important role as life's primary terminal electron acceptor during the transition from an anoxic to oxic surface Earth, and correspondingly, from anaerobic to aerobic metabolisms.

The effects of declined oxygen levels on hypoxia symptoms and blood gases: An experimental study

Environmental suffocation is a form of asphyxia. In such cases, an autopsy alone is not sufficient to determine the cause of death, and forensic pathologists need environmental data from the scene and the symptoms of hypoxia from the victim. Considering that the symptoms of hypoxia vary widely, the analysis of gases in the blood is used to assess the level of oxygenation in humans. No research has yet equated a specific level of oxygen in the air with environmental suffocation. This study aimed to determine the correlation among the decreased level of oxygen in the environment, the values of blood gases, and the emergence of the symptoms of hypoxia. Pig animal model (Sus scrofa) was used. This study induced a state of environmental suffocation in the pigs, which were placed in a chamber with oxygen levels decreasing from 21% to 11% and then to 7%. At each oxygen level, the symptoms of hypoxia and the values of arterial blood gases were assessed. It is concluded that the decreased oxygen levels in the chamber resulted in hypoxia symptoms such as changes in the respiratory rate, heart rate, and blood gases, such as the pH, PO2, PCO2, HCO3, BE, and O2 saturation values. These changes had different percentages that reflect each range of the decreased oxygen levels in the chamber.

Oxygen-enriched sintering for improved piezoelectric performance of (K0.5Na0.5)(Ta0.3Nb0.7)O3 lead-free ceramics: The impact of defects

In this work, (K0.5Na0.5)(Ta0.3Nb0.7)O3 (KNNT) powders synthesized by the microwave-hydrothermal method were sintered under different oxygen partial pressure (PO2 = 0, 0.498, 0.995 atm) atmospheres. Effects of PO2 on the phase composition, microstructure, piezoelectric properties, and defects in the KNNT ceramics were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Ultraviolet-visible diffuse reflectance spectroscopy (UV–Vis DRS). Results indicated that PO2 had almost no effect on the phase structure and grain morphology of KNNT ceramics. Abnormal grain growth was observed with increasing PO2; simultaneously, the density of the ceramics decreased. However, the d33 value reached its maximum of 205 pC/N when sintered at the highest PO2, and kp showed a similar trend. TEM observations indicated that the microscopic domains had the most regular domain orientation at a PO2 of 0.998 atm. These phenomena were due to the different oxygen vacancy concentrations caused by varying PO2. UV–Vis DRS revealed that the defect concentration decreased with increasing PO2; moreover, the oxygen vacancy concentrations were determined by XPS to be 23.5%, 21.1%, and 19.1% corresponding to PO2 values of 0, 0.498, and 0.995 atm, respectively, indicating that oxygen-enriched sintering can reduce defects and enhance piezoelectric properties.

Compatibility Analysis of Chromites in Dual-Phase Composites for Oxygen Transport Membranes

An oxygen transport membrane (OTM) is a promising way of supplying oxygen from air to high temperature processes, such as gasification.[1] Several studies have demonstrated that mixed ionic-electronic conducting (MIEC) perovskites with composition AxSr1-xCoyFe1-yO3-d (A=La, Ba) have high oxygen-ionic and electronic conductivity, which are the basic requirements for an OTM material. However, these perovskites have a limited pO2 operation range, suffering irreversible chemical decomposition at pO2 values below 10-12. [2] YCrO3-based perovskites show high electronic conductivity and thermo-chemical stability both at high temperatures (~1000 ºC) and in reducing environments (pO2 ~10-20 atm). [3,4] Hence, chromites in combination with highly stable ionic-conductors (e.g. ceria or zirconia-based materials) as dual-phase composites are alternative OTM materials. However, their chemical compatibility and stability together with ion-conductors in reducing conditions, as well as their oxygen permeation in different atmospheres, needs to be further investigated. This study analyses the stability of dual-phase composites consisting of 30 vol.% perovskite Y0.8Ca0.2Cr0.8Co0.2O3 (YCCC) and 70 vol.% ionic conductors Ce0.9Gd0.1O1.95 (CGO10) or (Sc2O3)0.1(Y2O3)0.01(ZrO2)0.89 (10Sc1YSZ) as OTM materials. These dual-phase composites were sintered in air between 1200 ºC and 1450 ºC to analyze the effect of temperature on the composites, and stability tests were made by exposing the composites to humidified 5% H2/N2 at 850 ºC. SEM-EDS, XRD and thermal analyses were performed to characterize the composites and identify possible secondary phases that could detriment their performance. Oxygen flux tests were performed using 1 mm thick pellets in air/N2, air/CO2 and air/H2-3%H2O gradients at temperatures up to 950 ºC. In 10Sc1YSZ-containing samples, densification was inhibited in the studied temperature range, which might be related to evaporation of transition metals from the perovskite B site, Ca mobility and possible reactions with Zr. Metal evaporation was slightly intensified after reducing conditions, resulting in relative densities <80%. Chromium depletion from the composite and formation of Cr2O3 crystals was observed in samples sintered at 1450 ºC. On the other hand, CGO10-based composite reached ~ 90% of relative density at 1200 ºC, though CaCrO4 formation, probably related to Ca excess in the perovskite, was identified. Nevertheless, higher stability towards reducing conditions was observed. Initial oxygen permeation tests performed in dense CGO10-YCCC composite pellets show fluxes up to 0.4 Nml·cm-2·min-1 at 950ºC in air/N2 gradient. The CGO10-YCCC dual-phase composite is therefore a promising material, which is now under further optimization and development as a tubular, multilayer OTM. [1] Julbe, A. et. al. Catalysis Today, 104 (2005), 102-113 [2] Niedrig, C. et al. Journal of The Electrochemical Society, 160 (2) F135-F140 (2013). [3] Gupta, S. et al. Materials Science and Engineering, 90 (2015), 1–36. [4] Suvorov, S.A. et al. Refractories and Industrial Ceramics, 45-2 (2004), 94-99.