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Background Despite much evidence supporting the monitoring of the divergence of transcutaneous partial pressure of carbon dioxide (tcPCO 2 ) from arterial partial pressure carbon dioxide (artPCO 2 ) as an indicator of the shock status, data are limited on the relationships of the gradient between tcPCO 2 and artPCO 2 (tc-artPCO 2 ) with the systemic oxygen metabolism and hemodynamic parameters. Our study aimed to test the hypothesis that tc-artPCO 2 can detect inadequate tissue perfusion during hemorrhagic shock and resuscitation. Methods This prospective animal study was performed using female pigs at a university-based experimental laboratory. Progressive massive hemorrhagic shock was induced in mechanically ventilated pigs by stepwise blood withdrawal. All animals were then resuscitated by transfusing the stored blood in stages. A transcutaneous monitor was attached to their ears to measure tcPCO 2 . A pulmonary artery catheter (PAC) and pulse index continuous cardiac output (PiCCO) were used to monitor cardiac output (CO) and several hemodynamic parameters. The relationships of tc-artPCO 2 with the study parameters and systemic oxygen delivery (DO 2 ) were analyzed. Results Hemorrhage and blood transfusion precisely impacted hemodynamic and laboratory data as expected. The tc-artPCO 2 level markedly increased as CO decreased. There were significant correlations of tc-artPCO 2 with DO 2 and COs (DO 2 : r = − 0.83, CO by PAC: r = − 0.79; CO by PiCCO: r = − 0.74; all P < 0.0001). The critical level of oxygen delivery (DO 2crit ) was 11.72 mL/kg/min according to transcutaneous partial pressure of oxygen (threshold of 30 mmHg). Receiver operating characteristic curve analyses revealed that the value of tc-artPCO 2 for discrimination of DO 2crit was highest with an area under the curve (AUC) of 0.94, followed by shock index (AUC = 0.78; P < 0.04 vs tc-artPCO 2 ), and lactate (AUC = 0.65; P < 0.001 vs tc-artPCO 2 ). Conclusions Our observations suggest the less-invasive tc-artPCO 2 monitoring can sensitively detect inadequate systemic oxygen supply during hemorrhagic shock. Further evaluations are required in different forms of shock in other large animal models and in humans to assess its usefulness, safety, and ability to predict outcomes in critical illnesses.

In the field of respiratory clinical practice, the importance of measuring carbon dioxide (CO2) concentrations cannot be overemphasized. Within the body, assessment of the arterial partial pressure of CO2 (PaCO2) has been the gold standard for many decades. Non-invasive assessments are usually predicated on the measurement of CO2 concentrations in the air, usually using an infrared analyzer, and these data are clearly important regarding climate changes as well as regulations of air quality in buildings to ascertain adequate ventilation. Measurements of CO2 production with oxygen consumption yield important indices such as the respiratory quotient and estimates of energy expenditure, which may be used for further investigation in the various fields of metabolism, obesity, sleep disorders, and lifestyle-related issues. Measures of PaCO2 are nowadays performed using the Severinghaus electrode in arterial blood or in arterialized capillary blood, while the same electrode system has been modified to enable relatively accurate non-invasive monitoring of the transcutaneous partial pressure of CO2 (PtcCO2). PtcCO2 monitoring during sleep can be helpful for evaluating sleep apnea syndrome, particularly in children. End-tidal PCO2 is inferior to PtcCO2 as far as accuracy, but it provides breath-by-breath estimates of respiratory gas exchange, while PtcCO2 reflects temporal trends in alveolar ventilation. The frequency of monitoring end-tidal PCO2 has markedly increased in light of its multiple applications (e.g., verify endotracheal intubation, anesthesia or mechanical ventilation, exercise testing, respiratory patterning during sleep, etc.).

The present study reviewed the carbon-biogeochemistry-related observations concerning CO2 and CH4 dynamics in the estuaries adjoining the Indian Sundarbans mangrove ecosystem. The review focused on the partial pressure of CO2 and CH4 [pCO2(water) and pCH4(water)] and air–water CO2 and CH4 fluxes and their physical, biogeochemical, and hydrological drivers. The riverine-freshwater-rich Hooghly estuary has always exhibited higher CO2 emissions than the marine-water-dominated Sundarbans estuaries. The mangrove sediment porewater and recirculated groundwater were rich in pCO2(water) and pCH4(water), enhancing their load in the adjacent estuaries. Freshwater-seawater admixing, photosynthetically active radiation, primary productivity, and porewater/groundwater input were the principal factors that regulated pCO2(water) and pCH4(water) and their fluxes. Higher chlorophyll-a concentrations, indicating higher primary production, led to the furnishing of more organic substrates that underwent anaerobic degradation to produce CH4 in the water column. The northern Bay of Bengal seawater had a high carbonate buffering capacity that reduced the pCO2(water) and water-to-air CO2 fluxes in the Sundarbans estuaries. Several authors traced the degradation of organic matter to DIC, mainly following the denitrification pathway (and pathways between aerobic respiration and carbonate dissolution). Overall, this review collated the significant findings on the carbon biogeochemistry of Sundarbans estuaries and discussed the areas that require attention in the future.

Main conclusion Storage at an elevated partial pressure of oxygen and classical artificial ageing cause a rapid loss of seed viability of short-lived vegetable seeds. Prolonging seed longevity during storage is of major importance for gene banks and the horticultural industry. Slowing down biochemical deterioration, including oxygen-dependent deterioration caused by oxidative processes can boost longevity. This can be affected by the seed structure and the oxygen permeability of seed coat layers. Classical artificial seed ageing assays are used to estimate seed 'shelf-life' by mimicking seed ageing via incubating seeds at elevated temperature and elevated relative humidity (causing elevated equilibrium seed moisture content). In this study, we show that seed lots of vegetable Allium species are short-lived both during dry storage for several months and in seed ageing assays at elevated seed moisture levels. Micromorphological analysis of the Allium cepa x Allium fistulosum salad onion seed identified intact seed coat and endosperm layers. Allium seeds equilibrated at 70% relative humidity were used to investigate seed ageing at tenfold elevated partial pressure of oxygen (high pO 2 ) at room temperature (22 ºC) in comparison to classical artificial ageing at elevated temperature (42 ºC). Our results reveal that 30 days high pO 2 treatment causes a rapid loss of seed viability which quantitatively corresponded to the seed viability loss observed by ~ 7 days classical artificial ageing. A similar number of normal seedlings develop from the germinating (viable) proportion of seeds in the population. Many long-lived seeds first exhibit a seed vigour loss, evident from a reduced germination speed, preceding the loss in seed viability. In contrast to this, seed ageing of our short-lived Allium vegetable seems to be characterised by a rapid loss in seed viability.

The aim of this paper is to present a novel negative temperature coefficient (NTC) thermistor based on A2Zr2O7 (A = Nd, Sm, Gd, Yb) zirconate ceramics with pyrochlore-type structure for high-temperature application. The zirconate ceramics were synthesized via a solid-state reaction method where rare-earth oxides and ZrO2 were used as starting materials. The physical structures were characterized by X-ray diffraction, scanning electron microscopy, and Raman spectroscopy. It was confirmed that Nd2Zr2O7 and Sm2Zr2O7 are pyrochlore phases, while Yb2Zr2O7 and Gd2Zr2O7 are defect fluorite phases. The electrical property investigated by using resistance–temperature measurements demonstrated that the prepared A2Zr2O7 zirconate ceramics exhibit a typical characteristic of NTC over a wide temperature range between 673 and 1273 K. Particularly, A2Zr2O7, in addition to having high activation energy to ensure better sensitivity, can still maintain higher resistivity under high-temperature environments. Furthermore, the resistivity of A2Zr2O7 is almost independent of the change in oxygen partial pressure. These properties are superior to the classical spinel-type or perovskite-type NTC thermistor, providing valuable information to explore new NTC thermistor for high-temperature applications.

In this study, the BaCeO 3 -BaZrO 3 material was modified using an internal addition method of ZnO as a sintering aid. resulting in the synthesis of the Zn, Y and Gd triple-doped BaCe 0.6 Zr 0.2-x Y 0.15 Gd 0.05 Zn x O 3-δ (BCZYGZn x , x  = 0, 0.02, 0.04, 0.06) materials. The impact of Zn doping as a sintering aid on the phase structure, microscopic morphology, electrical and transport properties of BCZYGZn x proton conductor materials were systematically investigated. The XRD results demonstrate that BCZYGZn x materials with a single perovskite structure have been successfully synthesized by the solid-phase reaction method. The SEM analysis results demonstrate that the introduction of Zn 2+ can markedly enhance the sintering performance of the materials. A comprehensive analysis of relaxation time distribution (DRT) and equivalent circuit scheme (ECS) was conducted to investigate the effects of temperature, test atmosphere and Zn doping concentration on the conductivity of BCZYGZn x materials. The results demonstrate that BCZYGZn0.04 material exhibits the highest conductivity of 9.25 × 10 –3 S cm −1 at 700 °C under p H 2 O = 0.018 atm and p O 2  = 0.20 atm atmospheres. The proton transference number of the BCZYGZn x materials were calculated according to the defect equilibrium model and the results indicate that BCZYGZn0.04 material has a higher proton transference number, reaching 0.88 at 600 °C. Furthermore, the proton transference properties of the material are mainly affected by the water pressure and less by the oxygen partial pressure according to the predominant regions of proton conduction in diverse atmospheres. In conclusion, the Zn doping strategy enhances the electrical and transport properties of BaCeO 3 -BaZrO 3 materials.

•  Introduction ‐  Imaging of hypoxic areas ‐  Hypoxia markers ‐  Positron emission tomography (PET) ‐  Near‐infrared spectroscopy (NIRS) ‐  Magnetic resonance spectroscopy (MRS) ‐  Electron paramagnetic resonance spectroscopy (EPR) •  Oxygen partial pressure measurement ‐  Polarographic sensor ‐  Optical sensor ‐  Mass spectrometry •  What does tumour hypoxia mean? •  Small molecules and hypoxia ‐  Chemotherapeutic drugs ‐  Radiation sensitizers: the nitroimidazoles ‐  Hypoxia prodrugs: tirapazimine and anthraquinone ‐  pO2 modulator: myo‐inositol trispyrophosphate (ITPP) ‐  Hypoxia mimetics: dimethyloxallyl glycine, desferrioxamine and metal ions •  What does physioxia mean? ‐  From air to blood ‐  In brain ‐  In lungs ‐  In skin ‐  In intestinal tissue ‐  In liver ‐  In kidney ‐  In muscle ‐  In bone marrow ‐  In umbilical cord blood ‐  To summarize physioxia •  Cellular and molecular consequences of physioxia versus normoxia and hypoxia ‐  Hypoxia inducible factors actions ‐  Role of microRNAs in hypoxia‐dependent regulations ‐  Cell adhesion molecules: their regulation by oxygen partial pressure ‐  Soluble molecules: example of angiogenin •  Conclusion 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.

According to the model by Riley and Cournand (9) and in analogy to VD/VT, it can be referred to as \"wasted\" pulmonary blood flow: the blood gas partial pressures from these regions are equal to or only slightly higher than the mixed venous ones, and therefore are the cause of arterial hypoxemia. In particular, different maneuvers can influence gas exchange through various mechanisms; for example, improved oxygenation can reflect a pure redistribution of blood flow (see inhaled vasodilators), a change in mixed venous O2 concentration, and/or a reopening of previously nonaerated lung units (see recruitment). [...]in ARDS the \"optimal\" SaO2 and PaO2 level remains undetermined, because experimental data suggest that hyperoxia can worsen VILI (133), and mechanical ventilation with FIO2 of 0.6 or greater for 3 or more days was associated with increased thickness of the air-blood barrier and endothelial cell injury (134). [...]a retrospective analysis demonstrated that the number of days with hyperoxemia as defined with a PaO2 greater than 120 mm Hg was an independent risk factor for ventilator-associated pneumonia (135). [...]Caironi and colleagues reported that the best combination of physiological parameters predicting more pronounced recruitment as measured by CT scan was PaO2/FIO2 on PEEP 5 cm H2O less than 150 mm Hg, together with increased compliance of the respiratory system and a decreased VD/VT when PEEP was increased from 5 to 15 cm H2O (247).

Background and Aims Because bronchoscopy is an invasive procedure, sedatives and analgesics are commonly administered, which may suppress the patient’s spontaneous breathing and can lead to hypoventilation and hypoxemia. Few reports exist on the dynamic monitoring of oxygenation and ventilation during bronchoscopy. This study aimed to prospectively monitor and evaluate oxygenation and ventilation during bronchoscopy using transcutaneous arterial blood oxygen saturation and carbon dioxide. Methods We included patients who required pathological diagnosis using fluoroscopic bronchoscopy at our hospital between March 2021 and April 2022. Midazolam was intravenously administered to all patients as a sedative during bronchoscopy, and fentanyl was administered in addition to midazolam when necessary. A transcutaneous blood gas monitor was used to measure dynamic changes, including arterial blood partial pressure of carbon dioxide (tcPCO 2 ), transcutaneous arterial blood oxygen saturation (SpO 2 ), pulse rate, and perfusion index during bronchoscopy. Quantitative data of tcPCO 2 and SpO 2 were presented as mean ± standard deviation (SD) (min–max), while the quantitative data of midazolam plus fentanyl and midazolam alone were compared. Similarly, data on sex, smoking history, and body mass index were compared. Subgroup comparisons of the difference (Δ value) between baseline tcPCO 2 at the beginning of bronchoscopy and the maximum value of tcPCO 2 during the examination were performed. Results Of the 117 included cases, consecutive measurements were performed in 113 cases, with a success rate of 96.6%. Transbronchial lung biopsy was performed in 100 cases, whereas transbronchial lung cryobiopsy was performed in 17 cases. Midazolam and fentanyl were used as anesthetics during bronchoscopy in 46 cases, whereas midazolam alone was used in 67 cases. The median Δ value in the midazolam plus fentanyl and midazolam alone groups was 8.10 and 4.00 mmHg, respectively, indicating a significant difference of p  < 0.005. The mean ± standard deviation of tcPCO 2 in the midazolam plus fentanyl and midazolam alone groups was 44.8 ± 7.83 and 40.6 ± 4.10 mmHg, respectively. The SpO 2 in the midazolam plus fentanyl and midazolam alone groups was 94.4 ± 3.37 and 96.2 ± 2.61%, respectively, with a larger SD and greater variability in the midazolam plus fentanyl group. Conclusion A transcutaneous blood gas monitor is non-invasive and can easily measure the dynamic transition of CO 2 . Furthermore, tcPCO 2 can be used to evaluate the ventilatory status during bronchoscopy easily. A transcutaneous blood gas monitor may be useful to observe regarding respiratory depression during bronchoscopy, particularly when analgesics are used.