Oxygen Tension Research Articles

High-flow nasal cannula oxygen therapy versus conventional oxygen therapy in patients undergoing bronchoscopy: a retrospective study

BackgroundPatients undergoing bronchoscopy, particularly those with pre-existing hypoxemia, face a significant risk of further deterioration in their oxygen saturation levels. This heightened risk necessitates the provision of supplemental oxygen therapy throughout the procedure, rendering it mandatory. High-flow nasal cannula (HFNC) has been widely employed in the management of hypoxemic acute respiratory failure (ARF) in adults. Based on this, HFNC has been used in endoscopic procedures, but there are still few studies on HFNC in fiberoptic bronchoscopy (FOB) patients. The purpose of this study was to evaluate the comparative efficacy of HFNC with nasal cannula oxygen in maintaining adequate oxygen saturation during fiberoptic bronchoscopy in patients with pre-existing hypoxemia.MethodsWe retrospectively investigated 232 patients with hypoxemia who underwent bronchoscopy between January 2018 to August 2023 who received either HFNC or nasal cannula oxygen supplementation. The control group received nasal cannula oxygen, and the observation group received HFNC. The changes of oxygen saturation, heart rate, blood pressure and adverse events during the operation were compared between the two groups.ResultsThe patients were divided into the HFNC (n = 78) and nasal cannula oxygen (n = 154) groups. During FOB, although the lowest oxygen saturation (SpO2) was similar in both groups (intraoperative minimum SpO2 was defined as the lowest value of SpO2 occurring between the start of anesthesia and the end of the operation), the occurrence of the lowest SpO2 < 90% was significantly lower in the HFNC group (3.8% vs. 17.5%, p = 0.003). No serious complications were reported in either group, however, the overall incidence of general adverse events was 7.7% and 20.1% in the HFNC and conventional oxygen therapy (COT) groups, respectively (p = 0.015). Multifactorial analysis showed that higher arterial partial pressure of oxygen versus the fraction of inspired oxygen (PaO2/FiO2; P/F) was a protective factor against desaturation events (p = 0.032, OR = 0.990, 95% CI: 0.982–0.999). In patients with baseline PaO2/FiO2 ≥ 200 mmHg, the HFNC group exhibited smoother vital sign changes from pre-procedure to the end of bronchoscopy, although there were no significant differences between the two groups regarding the rates of deoxygenation events as well as adverse events.ConclusionThe use of HFNC therapy can effectively reduce the incidence of SpO2 < 90% during bronchoscopy in patients with hypoxemia. Additionally, HFNC significantly reduces the overall incidence of adverse events compared to COT. In patients with milder hypoxemia, its advantages in maintaining operational stability during bronchoscopy should not be overlooked.

Detection of serum FOXM1 and IGF2 in patients with ARDS and their correlation with disease and prognosis

Abstract Objective To investigate the relationship between the expression levels of serum forkhead box protein M1(FOXM1) and insulin-like growth factor 2 (IGF2) mRNA in patients with acute respiratory distress syndrome (ARDS) condition and prognosis. Methods Ninety patients with ARDS admitted to our hospital were regarded as the ARDS group, according to the prognosis, they were grouped into death group (n = 64) and survival group (n = 126); the control group consisted of 190 healthy individuals. Results Compared with the control group, the level of serum FOXM1 mRNA in ARDS group was obviously lower, and the level of IGF2 mRNA was higher. The serum IGF2 mRNA, serum creatinine, inhaled oxygen concentration (FiO2), and mechanical ventilation time in the death group were higher than those in the control group, and the arterial oxygen partial pressure (PaO2), FOXM1 mRNA, and oxygenation index (PaO2/FiO2) were lower than those in control group. Logistic regression analysis indicated that FOXM1, IGF2, and PaO2/FiO2 were significant factors influencing the prognosis and mortality in ARDS patients. Correlation analysis showed that there was a negative correlation between serum FOXM1 and IGF2 mRNA levels in patients with ARDS. Conclusion Serum FOXM1 and IGF2 mRNA in patients with ARDS are correlated with the severity and prognosis of ARDS.

A finer-grained high altitude EEG dataset for hypoxia levels assessment

The study reports on a high-altitude EEG dataset comprising 64-channel EEG signals from 23 subjects, aiming at achieving a finer-grained assessment of hypoxia levels. Four hypoxia levels were induced by creating a gradient of oxygen partial pressure through changes in altitude and external hypoxia stimulation. The dataset was collected in a hypoxic chamber that simulates altitude changes, allowing for a refined classification of different hypoxia levels based on ranges of oxygen saturation. The total recorded EEG data amounts to approximately 10.25 hours. Validation results indicate that the four hypoxia levels can be effectively recognized using EEG signals. Compared to binary classification, our fine-grained dataset allows for more precise detection of hypoxia levels. This dataset is anticipated to have significant research and practical value in developing accurate methods for identifying hypoxia levels. As a valuable and standardized resource, it will enable extensive analysis and comparison for researchers in the field of high-altitude hypoxia.

Implementation of the Oxygen Saturation Index as a Predictor of Outcome in Prenatally Diagnosed CDH Neonates in the First 24 Hours of Life.

This study aimed to evaluate the Oxygen Saturation Index (OSI) as a noninvasive measure for early postnatal management and outcome prediction in neonates with congenital diaphragmatic hernia (CDH). Additionally, the study analyzed the correlation and predictive ability of OSI, Oxygenation Index (OI), Horovitz Index (HI), and partial pressure of arterial oxygen (PaO2) regarding mortality and the need for extracorporeal membrane oxygenation (ECMO). A retrospective, single-center study using data from 2013 to 2020. Parameters for calculating indices were extracted from patient charts every hour during the first 24 h of life. Statistical analyses included ROC analysis for predictive cut-off values and Spearman's rank for correlation assessments. The study included 138 neonates. Postductal OSI demonstrated high sensitivity (80%-85%) and negative predictive value (NPV) for predicting mortality and ECMO need, with cut-off values between 11.5 and 13. Optimal cut-off values for predicting ECMO need were 10 at 12 and 24 h (sensitivity 96.7%). OSI, OI, HI, and PaO2 showed comparable predictive capabilities with strong correlations. The lowest OI of 18 predicted mortality with a sensitivity of 75% and specificity of 90.9%. Strong correlations were found between the lowest PaO2 and lowest HI (0.963-0.974), and between highest OI and lowest PaO2 (-0.922 to -0.945). OSI is a promising index for predicting outcomes in CDH neonates, showing strong correlation with indices like OI and HI. Despite limitations, OSI provides continuous, bedside monitoring without invasive blood sampling. Further prospective studies are needed to validate these findings and establish new cut-off values.

Redox Stability and Electrical Properties of the High‐Entropy (Pb0.2Ca0.2Ba0.2Sr0.2Mg0.2)0.7La0.3WO4.15 Oxide Ion Conductor

Donor‐doped Pb1−xLaxWO4 (x ≤ 0.3) materials are well‐known for their high oxygen ionic conductivity. However, their poor phase and redox stabilities under a reducing atmosphere hinder their practical applications, such as electrolytes for solid oxide fuel cells. In this work, a high‐entropy (Pb0.2Ca0.2Ba0.2Sr0.2Mg0.2)0.7La0.3WO4.15 material is prepared through a traditional solid‐state reaction method, aimed to enhance the phase and redox stability of the material under reducing atmosphere. The results reveal that this material has high phase and structural stability in high oxygen partial pressure environments. However, it will still undergo phase decomposition, yielding impurity, and introducing strong electronic conduction, showing even lower redox stability and phase stability than the non‐high‐entropy counterpart Pb0.7La0.3WO4.15. Thus, improving the phase and redox stabilities under reducing atmospheres of the PbWO4‐based materials is still the main challenge in the future.

The Use of Arterial Blood Gases Analysis to Evaluate Lung Injury in Children with Congenital Heart Disease Disease who Undergo On-pump Cardiac Surgery

Abstract: congenital heart disease is a defect in the heart or great vessel discovered during infancy or later in life. Congenital heart disease is divided into acyanotic and cyanotic. Surgery is the main therapeutic option for any congenital heart disease. The cardiopulmonary bypass has advancements in open heart surgery. It provides circulatory and respiratory support. Aortic cross-clamp is necessary in most open heart surgeries to isolate the heart from circulation. Patients undergoing cardiac surgery on cardiopulmonary bypass often have disturbances in arterial blood gases, including partial pressure of oxygen, partial pressure of carbon dioxide, PH value, and bicarbonate. Aim of study: The study aimed to investigate the serial changes in arterial blood gases before, during, and after open heart surgery and to find the correlation between these changes and aortic cross-clamp time. Conclusion: This study finds the partial pressure of carbon dioxide is more predictive of lung injury after open heart surgery than the P/F ratio in cyanotic cases. While in acyanotic cases, the P/F ratio and partial pressure of carbon dioxide are important to determine lung injury. Also, this study finds that the prolonged cross-clamp time increases lung injury after open heart surgery.

Characteristics of the pregnancy and labour course in women who underwent COVID-19 during pregnancy.

This study aims to analyze the impact of COVID-19 on pregnancy and labor, focusing on its effects on maternal and child health. The research explores the relationships between coronavirus infection and clinical and laboratory parameters, as well as the risks of pregnancy complications and adverse birth outcomes. The study involved 60 pregnant women diagnosed with COVID-19. A comprehensive evaluation of clinical and laboratory indicators was conducted, employing correlation, regression, logistic analyses to determine risk factors. There was a strong inverse correlation between carbon dioxide levels and haematocrit (-0.76), and a direct correlation between blood pH and partial pressure of oxygen (0.73). COVID-19 was associated with increased risks of preterm labor (OR=1.82), stillbirth (OR=2.11), pre-eclampsia (OR=1.46), and foetal distress. Multivariate analysis revealed a 200 g reduction in neonatal birth weight and higher risks of hospitalisation (OR=1.8), postpartum hemorrhage (OR=2.3), and preterm delivery (OR=2.5). Comorbid conditions such as cardiovascular abnormalities, diabetes, obesity, thrombophilias exacerbated the risks of complications, including pre-eclampsia, neonatal respiratory distress syndrome, venous thromboembolism. COVID-19 infection increases the likelihood of pregnancy complications and adverse outcomes, especially in women with comorbidities. These findings highlight the need for preventive strategies and risk management protocols for pregnant women during future outbreaks, emphasizing the importance of further research in this field.

Empiric gram-negative antibiotics usage among critically ill patients across 13 ICUs of Nepal: A retrospective cohort study

Background This study aims to investigate the associations between patient characteristics and the receipt of empiric broad-spectrum gram-negative antimicrobials among adult patients admitted to ICUs in Nepal. Methods A retrospective cohort study was conducted in 13 ICUs in Nepal between January 1st, 2020, and December 31st, 2022. Empiric antibiotic use was defined as receiving gram-negative antibiotics within the first two days of ICU admission without evidence of infection from culture. Patient characteristics between patients receiving narrow-spectrum antibiotics and broad-spectrum gram-negative antibiotics were compared. Continuous variables were compared using mean and standard deviation, with mean differences and 95% confidence intervals calculated. Categorical variables were compared using the chi-square test. A multi-level multivariable regression model assessed the relationship between selected variables and broad-spectrum antibiotic usage, treating admitting ICU as a random factor. Results Among 12,349 eligible patients, 8720 (70.6%) received Empiric gram-negative antibiotics. Of those, 3240 (37.15%) received empiric narrow-spectrum gram-negative antibiotics, and 5480 (62.8%) received Empiric broad-spectrum gram-negative antibiotics. Patients receiving broad-spectrum gram-negative antibiotics were older (57.4 vs 53.8 yrs); had higher mean heart rates (97.3 vs 89.5 bpm), respiratory rates (24 vs 21.9), a fraction of inspired oxygen ( 50% vs 40%), blood sugar levels (163.4 vs 153.9 mg/dl), total leucocyte counts (12,685 vs 10,647 cells/cu mm) and serum creatinine (2.06 vs 1.03 umol/l) compared to narrow spectrum antibiotics. Similarly, patients receiving broad-spectrum gram-negative antibiotics had lower systolic blood pressure (122.6 vs 126.5 mm Hg), partial pressure of oxygen (96.7 vs 105.3), and pH ( 7.33 vs 7.36) compared to narrow-spectrum antibiotics. On multivariable regression; patients with readmission, cardiac support, and mechanical ventilation were more likely to receive broad-spectrum antibiotics. Conclusion The rate of empiric broad-spectrum gram-negative antibiotics usage in intensive care units is significantly high and associated with features of increased severity of illness.

Cortex kidney tissue partial oxygen pressure depends on percentage of active oxygenation during oxygenated hypothermic machine perfusion.

Preclinical and clinical studies have demonstrated the advantages of oxygenated hypothermic machine perfusion (HMPO2) during kidney preservation. However, the optimal oxygenation levels during HMPO2 remain undetermined. The aim of this study was to compare different levels of oxygenation (0%, 21%, 50%, and 100%) during 22 h of active oxygenated HMP (HMPO2) using oxygen preloading by bubbling oxygenation in the preservation solution and continuous surface oxygenation during MP in a porcine DCD model. After 60 min of warm ischemia time, both kidneys of an 80 kg pig were procured and randomized to one of the following groups: (1) 22-h static cold storage (n = 6), (2) 22-h HMP without active oxygenation (n = 6), (3) 22-h HMPO2 21% O2 (n = 6), (4) 22-h HMPO2 50% O2 (n = 6), and (5) 22-h HMPO2 100% O2 (n = 6). The primary outcome measure was to compare the different oxygen levels among the different groups assessed by cortex kidney tissue oxygen partial pressures (tpO2). Continuous HMPO2 resulted in a significant modification of cortex kidney tpO2. In addition, tpO2 was dependent on the percentage of oxygenation. One hundred percent oxygen resulted in a significantly higher tpO2 compared to all other study groups. In line with that, ATP resynthesis was significantly higher in the HMPO2 100% group. This study demonstrates that continuous HMPO2 results in a significant modification of tpO2 compared with SCS, and the degree of tpO2 is positively correlated with the percentage of active oxygenation during HMP. Metabolic profile analyses (ATP resynthesis) suggest that the aerobic mechanism is better supported with higher oxygen levels (50% and 100% oxygenation).

Incorporating a poly-ε-caprolactone scaffold in a stapled small intestinal anastomosis with induced ischemia significantly increased anastomotic tensile strength. An experimental study in pigs

Objective Anastomotic leakage is a severe complication with multifactorial aetiology, including impaired tissue oxygenation, infection, inflammation, and anastomotic tension. Reinforcement with poly-ε-caprolactone (PCL) scaffold incorporated in a stapled intestinal anastomosis has demonstrated a significant increase in the anastomotic tensile strength. This study aimed to investigate whether incorporation of the scaffold would influence tensile strength with induced ischemia compared to normal blood perfusion. Methods Eighteen pigs were randomly allocated into an intervention group with a induced relative reduction in blood perfusion to 30% at the anastomotic area and a control group with normal perfusion controlled by quantitative fluorescence angiography. Each pig recieved two stapled small intestinal anastomoses, one with a PCL scaffold incorporated and one without. On postoperative day five, the anastomoses were subjected to a maximal tensile strength test (MATS) and a histopathological analysis. Tensile strength was measured at three events: when a serosal tear became visible (MATS-1), at transmural rupture (MATS-2), and at maximum load before the load-strain curve dropped (MATS-3). Results In the intervention group, MATS-1 was significantly higher in scaffold-reinforced anastomoses compared to controls (7.9 ± 4.2N and 4.4 ± 2.5N, p < 0.02). The same tendency was found for MATS-2 and MATS-3, with statistically significant differences after adjusting for adhesion grade (p < 0.05). Histological analysis revealed no significant differences in wound healing between groups. Conclusion Incorporating a PCL scaffold in a stapled small intestinal anastomosis with induced ischemia improved anastomotic tensile strength.

Investigation of plasma sprayed Sr0·7La0·3TiO3 / La0·2Sr0·8MnO3 Bi-layer interconnector performance and its application in high power tubular solid oxide fuel cells

Atmospheric plasma spraying (APS) has been demonstrated as an efficient and rapid method for manufacturing high-performance solid oxide fuel cells (SOFCs), with interconnects serving as the “wires” for large-scale integration of SOFCs. However, the challenge of producing highly conductive and stable interconnects through plasma spraying remains unresolved. This study developed a Bi-layer perovskite interconnect for segmented-in-series solid oxide fuel cell (SIS–SOFCs). It involved APS-prepared dense N-type interconnects of Sr0·7La0·3TiO3 (LST), achieving low porosity, low leakage rate, and high conductivity LST coatings. The element of Ti valence state changes and conductivity of LST powders, hydrogen-treated powders, LST coatings, and hydrogen-treated coatings were quantitatively analyzed through phase detection and elemental valence state analysis under different oxygen partial pressure conditions to explore the variation of LST coating conductivity. Simultaneously, bi-layer interconnector model using La0·2Sr0·8MnO3(LSM)as the P-type interconnect was established to elucidate the electron transport mechanism within the Bi-layer interconnect under operating conditions and propose optimization schemes for the structural design of tubular serial-connected cell interconnects. The tubular dual-cell combination using LST/LSM Bi-layer interconnectors exhibited a maximum power density of 360 mW/cm2 at 800 °C, with only 33% interconnector loss compared to the maximum power density of 540 mW/cm2 achieved by a single cell at 800 °C. Additionally, it attained the highest open circuit voltage (1.9 V) at 650 °C. This Bi-layer interconnectors has been successfully applied in serial-connected tubular cells with more than 5 cells. Furthermore, the dual-cell combination showed almost no performance loss under 100 h of constant current discharge (0.3 A/cm2) testing. These research findings indicate that the LST/LSM Bi-layer interconnectors prepared using atmospheric plasma spraying is an ideal material system for the functional layer of interconnects in high-power tubular segmented-in-series solid oxide fuel cell structures.

Immediate postinjury extracorporeal carbon dioxide removal reduces ventilator requirements and mitigates acute respiratory distress syndrome in swine.

Awareness of ventilator-induced lung injury contributed to increased use of extracorporeal interventions, but not immediately after injury, before acute respiratory distress syndrome (ARDS) ensues. Our objective was to evaluate the role of venovenous extracorporeal carbon dioxide removal (ECCO2R) in management of mechanically ventilated swine with smoke inhalation injury and 40% body surface area burns. Yorkshire swine (n = 29, 43.2 ± 0.5 kg) underwent anesthesia, instrumentation, severe smoke inhalation, and 40% body surface area burns, followed by 72 hours of round-the-clock intensive care unit care with mechanical ventilation, fluids, pressors, bronchoscopic cast removal, computer tomography scans, and arterial blood assays. Within 1 hour after injury, animals received ECCO2R with either MiniLung (Xenios AG, Heilbronn, Germany; n = 10) or Hemolung (ALung Technologies, Pittsburgh, PA; n = 10), or no ECCO2R in injured controls (INJC, n = 12). Immediate postinjury ECCO2R reduced minute ventilation (p < 0.001) and prevented ARDS in 37.5% of MiniLung and 11.1% of Hemolung animals. Time to ARDS (partial pressure of arterial oxygen to fraction of inspired oxygen ratio below 300) was shortest (14 ± 2.2 hours) in INJC, intermediate (21.6 ± 3.5 hours) in Hemolung (HEMO), and most delayed in MiniLung (31.1 ± 7.2 hours, p = 0.0121, log-rank test vs. INJC). Driving pressure was lower in MiniLung versus INJC (p < 0.0001) and HEMO versus INJC (p = 0.0005) at 48 hours. Extracorporeal CO2 removal reduced systemic levels of tumor necrosis factor α versus INJC. In swine with severe smoke inhalation and burns, immediate postinjury ECCO2R reduced ventilator settings, delayed or prevented ARDS, and reduced its severity. Proactive early percutaneous ECCO2R initiation via simplified, purpose-built devices should be considered as a low-maintenance lung injury management approach with significant disease modifying clinical benefit potential.

In Vivo Mouse Abdominal Oxygen Imaging And Assessment of Subcutaneously Implanted Beta Cell Replacement Devices.

Type 1 diabetes (T1D) is an autoimmune disease that leads to the loss of insulin-producing pancreatic beta cells. Beta cell replacement devices or bioartificial pancreas (BAP) have shown promise in curing T1D and providing long-term insulin independence without the need for immunosuppressants. Hypoxia in BAP devices damages cells and imposes limitations on device dimensions. Noninvasive in vivo oxygen imaging assessment of implanted BAP devices will provide the necessary feedback and improve the chances of success. Pulse-mode electron paramagnetic resonance (EPR) oxygen imaging (EPROI) using injectable trityl OX071 as the oxygen-sensitive agent is an excellent technique for obtaining partial oxygen pressure (pO2) maps in vitro and in vivo. In this study, our goal was to optimize in vivo mouse abdominal EPROI and demonstrate proof-of-concept pO2 imaging of subcutaneously implanted BAP devices. All EPROI experiments were performed using a 25 mT EPROI instrument, JIVA-25®. For in vivo EPROI experiments, trityl OX071, a whole-body mouse resonator (∅32mm × 35mm), C57BL6 mice, and the inversion recovery electron spin echo (IRESE) pulse sequence were utilized. We investigated the signal amplitude and pO2 in mouse abdomen region for intravenous (i.v.) and intraperitoneal (i.p.) injection methods with either only a single bolus (B) or bolus plus infusion (BI) for 72.2mM OX071 and the effect of OX071 concentrations from 18 to 72.2 mM for the i.p.-B injection method. We also investigated the impact of animal respiratory rate on mouse abdominal pO2. Finally, we performed proof-of-concept pO2 imaging of two subcutaneously implanted BAP devices, OxySite and TheraCyte. At the end of the four-week study, the TheraCyte devices were extracted and analyzed for fibrosis, vascular differentiation, and immune cell infiltration. We established that mouse abdominal pO2 remains stable irrespective of trityl injection methods, concentrations, imaging time, or animal breathing rate. We demonstrate that the i.p.-B and i.p.-BI methods are suitable for EPROI, and i.p.-B method provides higher signal amplitude compared to i.v.-BIand up to 75min of imaging. An injection with a reduced trityl concentration and higher volume provides higher signal amplitude for i.p.-B method at the beginning. We also highlight the advantage of milder anesthesia for consistent, reliable mouse pO2 imaging. Finally, we demonstrate that EPROI could provide longitudinal noninvasive oxygen assessment of subcutaneously implanted BAP devices in vivo. In vivo EPROI is a reliable technique for mouse abdominal oxygen imaging and longitudinal assessment of subcutaneously implanted BAP devices noninvasively. This work reports abdominal oxygen imaging in the mouse model and demonstrates its application for the assessment of BAP devices. Even though the application focus of this work was on cell therapy, the techniques developed will have a much broader use in the biomedical field.

Gut eutrophication

“Classical eutrophication” occurs when raw unfixed nutrients enter an aquatic environment. This causes the deleterious proliferation in fauna most adept at exploiting this abundance of nutrition. The net effect is de-diversification. We propose an analogous process in the gut: “gut eutrophication”. Evidence shows that consumption of processed food, high in unfixed disaccharides, causes an expansion of bacteria in the gut habitat with a metabolic proclivity for these nutrients. This is at the expense of microbiota with a predilection for complex macromolecule macronutrients. There is a loss of diversity and the effect is exacerbated by a sedentary lifestyle. Gut luminal low oxygen tension favors salubrious gut commensals. This effect is potentiated by exercise but thwarted by inactivity. Antibiotics cause an obvious gut dysbiosis. So too can diet in a more insidious manner. The transition in microbial composition, seen in “gut eutrophication”, may be an aetiological component of metabolic disease-associated gut dysbiosis.

Theoretical analyses of the performance parameters of PEM fuel cells at various operating temperatures and pressures

In the present study, the performance parameters for a single-cell PEM fuel cell with 50 cm2 active surface area and 0.0178 cm polymer membrane thickness at 4 different operating temperatures (303, 323, 343, and 363 K) and 4 different operating pressures (3, 6, 9, and 12 atm) was investigated by theoretical analysis. Hydrogen and oxygen partial pressures, membrane resistivity, internal resistance, activation, ohmic and concentration losses, cell voltage, power density, and thermal efficiency were calculated using this analysis. It has been observed that the augmentation of temperature and pressure in the fuel cell leads to a favorable increase in cell voltage, power density, and thermal efficiency. The thermal efficiency values were found to be 23% and 39%, respectively at the following conditions: temperatures of 303 K and 363 K, current density of 1 A/cm2, and constant pressure. At the same current density, the thermal efficiency is 29% and 32% at 3 atm and 12 atm operating pressures at a constant temperature. When operated under constant current density and temperature conditions, an increase in the operating pressure of the PEMFC from 3 atm to 12 atm results in a corresponding increase in cell voltage, from 0.4422 V to 0.4755 V, respectively. It was observed that the influence of temperature on the thermal efficiency of the PEM fuel cell was led to be higher than the influence of pressure.

A Multiscale Mathematical Model for Fetal Gas Transport and Regulatory Systems During Second Half of Pregnancy.

Fetal asphyxia, a condition resulting from the combined effects of hypoxia and hypercapnia, leads to approximately 900,000 annual deaths worldwide. One cause is umbilical cord compression during labor-induced uterine contractions, disrupting the transport of metabolites to and from the placenta, and resulting in asphyxia. Current fetal well-being assessment relies on monitoring fetal heart rate and uterine contractions as indicators of oxygen delivery to the brain. To enhance our understanding of this complex relationship, this study aims to develop a modular mathematical model including fetal blood gas dynamics, the autonomic nervous system, and cerebral blood flow regulation. The novelty of this study lies in the capability of the model to simulate fetal growth. These submodels are part of a larger multiscale mathematical model describing fetal circulation in the second half of pregnancy. The blood gas model realistically replicates partial oxygen and carbon dioxide pressures in umbilical arteries and veins during healthy fetal development reported in the literature. An in silico experiment is conducted to simulate umbilical cord occlusion and is compared with lamb experiments to verify the realism of the regulation models during fetal growth. Our findings suggest that premature infants are more susceptible to umbilical cord occlusion, exhibiting elevated cerebral perfusion pressure and flow. This modular mathematical model may serve as a valuable tool for testing hypotheses related to the fetal regulatory system.

Phase Formation, Microstructure, and Permeability of Fe-Deficient Ni-Cu-Zn Ferrites (II): Effect of Oxygen Partial Pressure

We have investigated the phase formation, microstructure, and permeability of stoichiometric and Fe-deficient Ni-Cu-Zn ferrites of composition Ni0.30Cu0.20Zn0.50+zFe2−zO4−(z/2) with 0 ≤ z ≤ 0.06 sintered at 1000 °C in various oxygen partial pressures pO2, which range from 0.21 atm down to 10−5 atm. The density of the sintered samples is almost independent of the pO2, whereas the grain size of the Fe-deficient ferrites decreases in more reducing atmospheres. Stoichiometric ferrites show a regular growth of single-phase ferrite grains if sintered in air. Sintering at pO2 ≤ 10−2 atm leads to the formation of a small amount of Cu2O at grain boundaries and triple points. Fe-deficient compositions (z &gt; 0) form Cu-poor stoichiometric ferrites, which coexist with a minority CuO phase homogeneously distributed between the grains after sintering in air. At pO2 ≤ 10−2 atm, the CuO grain boundary phase starts to transform into Cu2O, which concentrates at some triple points at pO2 = 10−2 atm, and it is more homogeneously distributed between the ferrite grains at the lower pO2. Formation of the Cu oxide second phases is investigated using XRD, SEM, and EDX. The permeability at 1 MHz of the stoichiometric ferrites (z = 0) is between µ′ = 200 and µ′ = 300 within the studied range of the pO2. The permeability at 1 MHz of the Fe-deficient samples decreases with the pO2, e.g., from µ′ = 750 at pO2 = 0.21 atm to µ′ = 320 at pO2 = 10−5 atm for z = 0.02, respectively.

A comparison of the effect of oxygen partial pressure on microstructural evolution of PAN fibers during industrial carbon fiber production line at different altitudes

Understanding and regulating the oxidative stabilization behavior of polyacrylonitrile (PAN) precursor fibers are critical subjects of high-performance carbon fiber production technologies. Here, we performed continuous stabilization and carbonization of PAN fibers at industrial carbon fiber production lines in different locales (different oxygen partial pressure in atmosphere), and investigated the microstructural evolution of the fibers with a systematically analysis at different stages. Influence of oxygen partial pressure in oxidative stabilization atmosphere on tensile modulus of the obtained carbon fibers was obvious. Oxygen diffused into PAN fibers during oxidative stabilization, more homogeneous and crosslinked structures generated under higher oxygen partial pressure atmosphere, and gave the stabilized fibers lower skin-core ratio. The graphite layers gradually generated in the subsequent carbonization stages, and the gathered graphite layers transformed into graphite microcrystalline, the wide-angle x-ray diffraction (WAXD) demonstrated that higher oxygen partial pressure conditions contributed to the generation of higher crystallite preferred orientation and bigger crystallite size, Raman spectroscopy also confirmed the obtained carbon fibers with higher oxygen partial pressure conditions possessed more ordered graphite structures. Thus, relatively higher oxygen partial pressure in air gave the stabilized fibers more crosslinked structures, and contributed to the formation of high-performance carbon fibers.

Effects of very early hyperoxemia on neurologic outcome after out-of-hospital cardiac arrest: A secondary analysis of the TTM-2 trial.

Hyperoxemia is common in patients resuscitated after out-of-hospital cardiac arrest (OHCA) admitted to the intensive care unit (ICU) and may increase the risk of mortality. However, the effect of hyperoxemia on functional outcome, specifically related to the timing of exposure to hyperoxemia, remains unclear. The secondary analysis of the Target Temperature Management 2 (TTM-2) randomized trial. The primary aim was to identify the best cut-off of partial arterial pressure of oxygen (PaO2) to predict poor functional outcome within the first 24 h from admission, with this period further separated into 'very early' (0-4 h), 'early' (8-24 h), and 'late' (28-72 h) periods. Hyperoxemia was defined as the highest PaO2 recorded during each period. Poor functional outcome was defined as a 6 months modified Rankin Score (mRS) of 4 to 6. A total of 1,631 patients were analysed for the 'very early' and 'early' periods, and 1,591 in the 'late period'. In a multivariate logistic regression model, a PaO2 above 245 mmHg during the very early phase was independently associated with a higher probability of poor functional outcome (Odds Ratio, OR = 1.63, 95 % Confidence Interval, CI 1.08-2.44, p = 0.019). No significant associations were found for the later periods. Very early hyperoxemia after ICU admission is associated with higher risk of poor functional outcome after OHCA. Avoiding hyperoxia in the initial hours after resuscitation should be considered.

Investigation of Topography and Electrical Properties of K0.3MoO3 Thin Films

Abstract In this article we investigate topography and electrical properties of potassium blue bronze thin films by the means of atomic force microscopy. Thin films were prepared by pulsed laser depositions on two types of substrates (Al2O3 and SrTiO3) at different substrate temperatures and partial oxygen pressures. On the basis of topography measurements, granular nature of the films was revealed. Surface roughness, as well as the size and the orientation of grains was determined. Films deposited on SrTiO3 substrates are quite homogeneous and the grains display ordering in preferential directions. Films on Al2O3 contain randomly oriented grains. Roughness of the films increases with the increase of the deposition temperature. Electrical measurements provided qualitative information regarding the electrical properties of the films.