Variation Of Partial Pressure Research Articles

Magnitude of and Hydroclimatic Controls on CO2 and CH4 Emissions in the Subtropical Monsoon Pearl River Basin

AbstractRivers are important ecosystems for carbon emissions and play a crucial role in the global carbon cycle. However, CO2 and CH4 emissions from subtropical rivers are substantially under‐represented in global‐scale estimates. Here, we explored the regional patterns of riverine CO2 and CH4 dynamics in the Pearl River basin with a subtropical monsoon climate. We found that its CO2 and diffusive CH4 emissions showed a decreasing trend with increasing stream order. Seasonality in CO2 and diffusive CH4 emissions was primarily driven by variations in partial pressure of CO2 (pCO2) and CH4 (pCH4) and gas transfer velocities, which were strongly regulated by hydrology and climate. We further estimated the basin‐wide CO2 and diffusive CH4 fluxes at 17.8 ± 7.4 Tg C yr−1 and 191.5 ± 139.9 Gg C yr−1, respectively. When normalized to the water surface, the mean diffusive fluxes were 790.1 and 8.5 mmol m−2 d−1 for CO2 and CH4, respectively, which were 1.3 and 2.5 times higher than the global mean riverine CO2 and CH4 fluxes, respectively. This suggests that the global significance of subtropical rivers is probably underestimated because their substantially higher CH4 fluxes are unaccounted for. Furthermore, compared with measured pCO2, the alkalinity‐based pCO2 could introduce significant errors by 20% at ∼30% of the sampling sites, underscoring the necessity of direct measurements to reduce uncertainty. This study provides the first estimate of basin‐wide CO2 and diffusive CH4 emissions in the PRB through direct pCO2 and pCH4 measurements, and highlights the role of hydrologic and climatic factors in governing riverine carbon emissions.

Significant CO2 emission in the shallow inshore waters of the southeastern Yellow Sea in 2020

This study investigated the carbonate system and air-sea CO2 exchange in the inshore waters along South Korea's western coastline in 2020. Overlooking these waters might introduce significant errors in estimating air-sea CO2 fluxes of the southeastern Yellow Sea, given their interaction with land, offshore regions, and sediments. During periods other than summer, seasonal variations in seawater CO2 partial pressure (pCO2) could be generally explained by thermal effects. Tidal mixing and shallow depths resulted in weaker stratification-induced carbon export compared to offshore regions. However, during summer, inshore waters exhibited high spatial variability in pCO2, ranging from approximately 185 to 1000 μatm. In contrast to offshore waters that modestly absorbed CO2, inshore waters shallower than 20 m emitted ∼100 Gg C yr−1 to the atmosphere. However, considering the high heterogeneity of the study area, additional observations with high spatial and temporal resolution are required to refine estimates of air-sea CO2 exchange.

Temporal variability of air-water gas exchange of carbon dioxide in clam and fish aquaculture ponds

The growing trend of land-based aquaculture has heightened the significance of comprehensively assessing air-water carbon dioxide (CO2) gas exchange in these inland waters, given their potential impact on carbon neutral strategies. However, temporal variations of partial pressure of CO2 (pCO2) and CO2 flux in clam and fish aquaculture ponds were barely investigated. We assessed the water surface pCO2 in one to five months intervals by deploying a lab-made buoy in three clam ponds and three fishponds located in tropical and subtropical climates. Measurements were conducted over a 24 h period each time, spanning from April 2021 to June 2022, covering the stocking, middle, and harvesting stages of the culture cycle. Diurnal pCO2 variations were dominantly controlled by biologically driven changes in dissolved inorganic carbon and total alkalinity (~97 %), while temperature and salinity effects were minor (~3 %). Clam ponds acted as a sink of atmospheric CO2 during stocking stages and transitioned to a source during middle to harvesting stages. In contrast, fishponds acted as a source of atmospheric CO2 throughout culture cycles and CO2 flux strengthened when reaching harvesting stages. Overall, clam ponds acted as a weak sink for atmospheric CO2 (−2.8 ± 17.3 mmol m−2 d−1), whereas fishponds acted as a source (16.8 ± 21.7 mmol m−2 d−1). CO2 emission was stronger during daytime coinciding with higher windspeeds compared to nighttime in fishponds. We suggest incorporating high temporal resolution measurements to account for diurnal and culture-stage variations, enabling more accurate estimates of air-water CO2 flux in aquaculture ponds. Moreover, the findings of this study highlight the importance of feeding, aeration, and biological activities (photosynthesis, remineralization, and calcification) in controlling the air-water CO2 flux in aquaculture ponds and such information can be used in implementing better strategies to achieve carbon neutral goals.

Kinetics of dehydrogenation of n-heptane over GaPt supported catalytically active liquid metal solutions (SCALMS).

The concept of Supported Catalytically Active Liquid Metal Solutions (SCALMS) was explored for the catalytic dehydrogenation of n-heptane. For this purpose, a GaPt on alumina (Ga84Pt/Al2O3) was compared with a Pt on alumina catalyst at different reaction temperatures and feed compositions. While the observed activation energies with both catalysts for the overall n-heptane depletion rate were similar with both catalysts, the SCALMS systems provides a lower activation energy for the desired dehydrogenation path and significantly higher activation energies for the undesired aromatization and cracking reaction. Thus, the SCALMS catalyst under investigation shows technically interesting features, in particular at high temperature operation. The partial pressure variation revealed an effective reaction order of around 0.7 for n-heptane for both catalysts, while the effective order for hydrogen was 0.35 for Pt/Al2O3 and almost zero for SCALMS.

Sea Surface pCO2 Response to Typhoon “Wind Pump” and Kuroshio Intrusion in the Northeastern South China Sea

The Luzon Strait (LS) is a key region for estimating carbon sources and sinks in the South China Sea (SCS) and is highly influenced by the Kuroshio Current (KC) and typhoons. Understanding the variations in the sea surface partial pressure of carbon dioxide (pCO2-sw) under the combined effects of typhoons and KC in this region is crucial for estimating local and regional changes in ocean carbon flux. Based on valuable in situ pCO2-sw and remote sensing data, this study aimed to reveal the temporal variations and the physical mechanisms of pCO2-sw variations under the comprehensive effects of both typhoons and Kuroshio Intrusion (KI) in the LS. One week after the passage of the tropical cyclone (TC) Nanmadol, the concentration in the pCO2-sw and the influencing mechanisms varied in three different regions (W1–W3) on Transect A (120°E). In the region dominated by SCS waters (W1), the average pCO2-sw increased by 5.1 μatm after TC, which was mainly due to the TC “Wind Pump” inducing strong vertical mixing, which brought dissolved inorganic carbon (DIC)-rich deeper water up to the surface. In the region affected by KC (W2 and W3), pCO2-sw decreased after the TC (−8.2 μatm and −1.8 μatm, respectively) with TC-enhanced KI because the invasion of lower pCO2-sw of Kuroshio waters inhibited the TC-induced upwelling. More significant TC-induced upwelling (W3) would alleviate the decrease in pCO2-sw caused by the TC-enhanced KI. This study is a rare case providing a better understanding of the variations in pCO2-sw under TC-enhanced KI, which provides support for regional climate change prediction and carbon flux estimation in the western boundary current regions.

Diazotrophic nitrogen fixation through aerial roots occurs in Avicennia marina: implications for adaptation of mangrove plant growth to low-nitrogen tidal flats.

Nitrogen limitation of primary production is common in coastal ecosystems. Mangrove trees maintain high levels of nitrogen fixation around their roots. The interior aerial space of mangrove roots, in which atmospheric gas is supplied through lenticels, could be efficient sites for nitrogen fixation. We measured tidal variations of partial pressure of N2 in root aerenchyma and conducted field experiments using 15 N2 as a tracer to track N2 movement through aerial roots of Avicennia marina. We used the acetylene reduction assay to identify the root parts harboring diazotrophs. The nitrogenase activity and estimated nitrogen fixation through aerenchyma were higher in pneumatophores and absorbing roots than in cable roots. Positive correlations between root nitrogen contents and turnover rates of root nitrogen derived from N2 through aerenchyma suggested that the internal supply of N2 to diazotrophs could be the main source for nitrogen assimilation by A. marina roots. Our results confirmed that N2 is supplied to diazotrophs through aerial roots and that nitrogen fixation occurs in A. marina roots. The aerial root structures, which occur across families of mangrove plants, could be an adaptation to survival in not only low-oxygen environments but also tidal flats with little plant-available nitrogen.

Impact of sputtering gas on the microstructural, mechanical and wetting properties of vanadium nitride coatings

Vanadium nitride (VN) coatings were deposited via reactive DC magnetron sputtering technique on a hot substrate (400 °C) with varying partial pressure of N2. The impact of nitrogen partial pressure on the crystal structure, microstructure, elemental composition, surface topography, mechanical and wetting properties of VN coatings was investigated using grazing incidence X-ray diffraction (GIXRD), Raman spectroscopy, field emission scanning electron microscope (FESEM), energy dispersive spectroscopy (EDS), atomic force microscope (AFM), nano-indentation, and drop shape analyzer (DSA). The variation in the N2 partial pressure leads the significant changes in the microstructure, mechanical and wetting properties of the coatings. The GIXRD spectra reveals the formation of crystalline FCC phase in the deposited VN coatings. However, at 100% N2 partial pressure, the preferred orientation of crystal planes changes from (200) to (220). The FESEM image reveals that at low N2 partial pressure, the coating exhibits well-separated grains with clearly visible grain boundaries. As the N2 partial pressure increases, the agglomeration of grains becomes more pronounced, and the grain boundaries become less discernible. However, at 100% N2 partial pressure, the structure transforms into triangular nanoflake-like prismatic structures with voids. The VN coatings with 60% N2 partial pressure exhibits the highest mechanical properties whereas at 100% N2 partial pressure, the VN coatings reveal super-hydrophilic character.

Thermodynamic model of hydrogen-based fuel cell

The contemporary scholarly treatise expatiates on a lofty and refined mathematical schema of a Proton Exchange Membrane fuel cell seamlessly integrated into the Matlab Simulink milieu. The central aim of this model is to transcend the short descriptions of fuel cell functioning using parameters that denote certain physical connotations in an all-embracing manner. With minimal computational overhead, it could be extended to simulate an entire stack of fuel cells within the purview of an energetic system. The performance of each cell and its response to variations in pressure, temperature, humidity, and partial pressure of reactants are scrutinized with the utmost care, and the paramountcy of membrane hydration is exposed.

Under the sea: How can we use heart rate and accelerometers to remotely assess fish welfare in salmon aquaculture?

Recent advances in bio-sensing technologies open for new possibilities to monitor and safeguard the welfare of fishes in aquaculture. Yet before taken into practice, the applicability of all novel biosensors must be validated, and the breadth of their potential uses must be investigated. Here, we investigated how ECG and accelerometry-derived parameters measured using bio-loggers, such as heart rate, acceleration and variance of acceleration, relate to O2 consumption rate (MO2) and blood borne indicators of stress and tissue damage to determine how biologgers may be used to estimate stress and welfare. To do this, we instrumented 13 fish with a biologger and an intravascular catheter and subjected them to a swimming protocol followed by a stress protocol throughout which the physiological parameters were measured and analyzed a posteriori. Additionally, based on the empirical data obtained, we calculated the mathematical relationships between the bio-logger data and the other parameters and tested the relationship between the calculated parameters using the linear regression algorithms and the measured parameters. Our results show that acceleration is a good proxy for swimming activity as it is closely related to tail beat frequency. In addition, we show that heart rate, acceleration and variance of acceleration all can be used as predictors for metabolic rate. Accelerometry based data, especially variance of acceleration, significantly explain some of the variation in venous partial pressure of O2, blood lactate and plasma cortisol concentration. Variance of acceleration also significantly explains some of the variation in pH and mean corpuscular hemoglobin concentration. These relationships are explained by variance of acceleration being a good indicator of the onset of burst-swimming activity, which is often followed by acid-base imbalances and release of catecholamines. The results herein indicate that bio-logger data can be used to extrapolate a range of stress-related physiological events when these are accompanied by increases in activity and highlight the great potential of biosensors for monitoring fish welfare.

Optimization of the superconducting properties of NbTiN thin films by variation of the N2 partial pressure during sputter deposition

We report the effect of nitrogen partial pressure on the growth of niobium-titanium nitride (NbTiN) thin films through reactive sputtering of the NbTi target in the presence of Ar and N2 atmosphere. The N2 partial pressure was varied from 5.8% to 15.15% with respect to the Ar flow available in the chamber. We measured a critical temperature (T C) as high as 15.77 K for an N2 partial pressure of 6.8% for a 50 nm film deposited on an MgO substrate. The epitaxial growth of the NbTiN films is evident from the observed (200) and (400) XRD peaks with respect to the substrate. The superconducting properties were analyzed with respect to the observed values of T C, ΔT C, temperature dependence of the upper critical field (B C2), coherence length (ξ), diffusion coefficient (D), and the thermally activated flux flow behavior following the Arrhenius equation. The T C variation observed for the entire spectrum of N2 partial pressure variation is ∼11%, with T C getting saturated towards the higher end of the N2 content. While the T C variation with respect to N2 content is non-linear, the variation of B C2(0), diffusion coefficient, and zero temperature coherence length ξ(0) show a linear dependence. While the B C2(0) values show an increasing trend, D and ξ(0) values show a decreasing trend with respect to the increase of N2 partial pressure. It is concluded that the optimum window of N2 partial pressure for the reactive sputtering of NbTiN using a target of Nb0.7Ti0.3 for the present experimental conditions, in terms of epitaxial growth and obtaining the highest T C is within the range of 5.8% to 8.51%.

Dehydrogenation of dicyclohexylamine in gaseous phase over a nickel catalyst: effect of reaction parameters

This work deals with a study of the effect of reaction temperature and partial pressure of hydrogen on the product selectivity of the gas-phase dehydrogenation of dicyclohexylamine. Laboratory experiments of dicyclohexylamine dehydrogenation were performed in a glass tubular flow-through reactor with the use of commercial supported nickel Ni/Cr2O3-SiO2 catalyst. The systematic variation in reaction temperature (433–463 K) and partial pressure of hydrogen, i.e. the molar ratio of dicyclohexylamine to H2 and N2 (1:0:30–1:15:0), was used to investigate the dehydrogenation of dicyclohexylamine from the perspective of the formation of products. It was confirmed that the major products of dicyclohexylamine dehydrogenation are imine N-cyclohexylidenecyclohexanamine and aromatic amine N-phenylcyclohexylamine, while the latter is the dominant product. The sequential hydrogenolysis reaction of N-phenylcyclohexylamine was observed to result in the formation of cyclohexylamine and benzene. Furthermore, a significant increase in the concentration of the other six products was observed. The mass spectrometry detection identified these products as N-butylcyclohexanamine, N-pentylcyclohexanamine, N-isopentylcyclohexanamine, N-(2-methylbutyl)cyclohexanamine, N-cyclopentylcyclohexanamine, and N-(3-methylcyclopentyl)cyclohexanamine. The reaction results in the formation of two dehydrogenation products, which are accompanied by other subsequent reactions, such as hydrogenolysis, isomerization, and cyclization.Graphical abstract

Dual titration of minute ventilation and sweep gas flow to control carbon dioxide variations in patients on venovenous extracorporeal membrane oxygenation

BackgroundThe implantation of venovenous extracorporeal membrane oxygenation (VV-ECMO) support to manage severe acute respiratory distress syndrome generates large variations in carbon dioxide partial pressure (PaCO2) that are associated with intracranial bleeding. We assessed the feasibility and efficacy of a pragmatic protocol for progressive dual titration of sweep gas flow and minute ventilation after VV-ECMO implantation in order to limit significant PaCO2 variations.Patients and methodsA protocol for dual titration of sweep gas flow and minute ventilation following VV-ECMO implantation was implemented in our unit in September 2020. In this single-centre retrospective before-after study, we included patients who required VV-ECMO from March, 2020 to May, 2021, which corresponds to two time periods: from March to August, 2020 (control group) and from September, 2020 to May, 2021 (protocol group). The primary endpoint was the mean absolute change in PaCO2 in consecutive arterial blood gases samples drawn over the first 12 h following VV-ECMO implantation. Secondary endpoints included large (> 25 mmHg) initial variations in PaCO2, intracranial bleedings and mortality in both groups.ResultsFifty-one patients required VV-ECMO in our unit during the study period, including 24 in the control group and 27 in the protocol group. The protocol was proved feasible. The 12-h mean absolute change in PaCO2 was significantly lower in patients of the protocol group as compared with their counterparts (7 mmHg [6–12] vs. 12 mmHg [6–24], p = 0.007). Patients of the protocol group experienced less large initial variations in PaCO2 immediately after ECMO implantation (7% vs. 29%, p = 0.04) and less intracranial bleeding (4% vs. 25%, p = 0.04). Mortality was similar in both groups (35% vs. 46%, p = 0.42).ConclusionImplementation of our protocol for dual titration of minute ventilation and sweep gas flow was feasible and associated with less initial PaCO2 variation than usual care. It was also associated with less intracranial bleeding.

Hypercapnia under controlled mechanical ventilation in patients with high-risk acute pulmonary thromboembolism

Objective: To evaluate the variation of arterial partial pressure of carbon dioxide (PaCO2) in patients with high-risk pulmonary embolism under mechanical ventilation. Methods: We retrospectively analyzed the cases of high-risk pulmonary embolism who underwent intravenous thrombolysis in Peking Union Medical College Hospital from January 1, 2012, to May 1, 2022. The enrolled patients were divided into a mechanical-ventilated group and an active-breathing group according to whether they received invasive mechanical ventilation or not. The level of PaCO2 under active breathing between the two groups, the changes in PaCO2 before intubation, after intubation and after thrombolysis in the mechanical-ventilated group were compared. The 14-day all-cause mortality of the two groups was calculated and compared. Results: A total of 49 patients with high-risk pulmonary embolism were enrolled, including 22 patients in the mechanical-ventilated group and 27 patients in the active-breathing group. Before intubation, PaCO2 in both groups was lower than normal without statistically significant difference between the two groups. After effective thrombolysis therapy, PaCO2 in both groups recovered to the normal range. In the mechanical-ventilated group, PaCO2 significantly increased 11-147 min after intubation and returned to the normal range after thrombolysis therapy. The 14-day mortality in the mechanical-ventilated group was 54.5%, while all patients in the active-breathing group survived. Conclusions: Under mechanical controlled ventilation, patients with high-risk pulmonary embolism could represent hypercapnia which resolved after effective thrombolytic therapy. In mechanical ventilated patients with sudden-onset hypoxemia and hypercapnia, the possibility of high-risk pulmonary embolism should be considered.

Optic Fiber Microsensor Reveals Specific Spatiotemporal Oxygen Uptake Profiles at the Mammalian Ocular Surface.

Oxygen (O2) uptake by cells and tissues is a critical indicator of metabolic demand, changes in microenvironment, and pathophysiology. O2 uptake from the atmosphere accounts for virtually all the O2 consumption in the avascular cornea; however, a detailed spatiotemporal profile of corneal O2 uptake (COU) remains undetermined. Here, we used a non-invasive self-referencing optical fiber O2 sensor-the scanning micro-optrode technique (SMOT)-to report the O2 partial pressure and flux variations at the ocular surface of rodents and non-human primates. In vivo spatial mapping in mice revealed a distinct COU, characterized by a centripetal gradient with a significantly higher O2 influx at the limbus and conjunctiva regions than at the center of the cornea. This regional COU profile was reproduced ex vivo in freshly enucleated eyes. The centripetal gradient was conserved across the following species analyzed: mice, rats, and rhesus monkeys. In vivo temporal mapping in mice showed a significant increase in the O2 flux in the limbus in the evening compared to other times. Altogether, the data unveiled a conserved centripetal COU profile, which may be associated with the limbal epithelial stem cells residing at the intersection of the limbus and conjunctiva. These physiological observations will serve as a useful baseline for comparative studies with contact lens wear, ocular disease, diabetes, etc. Moreover, the sensor may be applied to understand the responses of the cornea and other tissues to various insults, drugs, or changes in the environment.

Effects of Argon Partial Pressure Variations on Wettability and Anti-icing Characteristics of Aluminum Doped ZnO Thin Films

When ice forms on solid surfaces, it can cause issues in many different sectors (aircraft, electricity lines, etc.). Surfaces and coatings with hydrophobic qualities may be used in anti-icing applications. The purpose of this work is to utilize RF Magneton Sputtering to deposit AZO thin coatings, which will slow the accumulation of ice on the surface. The effects of changes in argon partial pressure on the anti-icing, wettability, optical, and structural properties of the resulting thin films have been experimentally investigated. X-ray diffraction demonstrated a (002) peak of ZnO, the intensity of the peak diminishes with an increase in partial pressure. The band gap was measured to be between 2.98 and 3.15 eV, and the average maximum transmittance was observed to be around 82% for 50% partial pressure and 71% for 33% partial pressure, confirming the transparency of the thin films. Wettability studies revealed that the films are hydrophobic with a maximum contact angle of 127.5°, which was deposited at lower partial pressure. Films deposited at 33% partial pressure delayed the formation of ice on the surface by 4.5 folds when compared to an uncoated substrate.

Oxidation Behavior, Insulation Resistance, and Permeability of FeSiCr Alloys for Multilayer Inductors

FeSiCr alloys are used as soft magnetic materials for power multilayer inductors. The alloys are typically annealed at intermediate temperatures in air during inductor fabrication to form an insulating chromium oxide layer around the alloy particles. The variation of the annealing temperature between 700 °C and 900 °C in air, and, for the first time, the variation of the oxygen partial pressure during annealing at 900 °C are studied, and their effects on the alloy’s oxidation behavior, phase formation, insulation resistance, and permeability are demonstrated. The chromium oxide content increases up to about 12 wt% with annealing temperature in air, whereas it decreases to 8.2 wt% after annealing at 900 °C and 0.001% O2. The observed mass changes during annealing confirm the various tendencies towards oxidation. This oxidation behavior is reflected in an increase in the insulation resistance with annealing temperature or in a resistance reduction with decreasing oxygen partial pressure. The permeability decreases from µ = 22 after annealing at 700 °C to µ = 18.5 at 900 °C in air. The reduction of pO2 during annealing at 900 °C leads to an increase in permeability up to µ = 22.5 at pO2 = 0.001% O2. The results can be used to design cofiring strategies using reduced oxygen partial pressure for new composite multilayer inductive components consisting of FeSiCr- and ferrite layers in combination with silver metallization.

Arctic Ocean annual high in {{boldsymbol{p}}}_{{{bf{CO}}}_{{bf{2}}}} could shift from winter to summer

Long-term stress on marine organisms from ocean acidification will differ between seasons. As atmospheric carbon dioxide (CO2) increases, so do seasonal variations of ocean CO2 partial pressure ({p}_{{{rm{CO}}}_{2}}), causing summer and winter long-term trends to diverge1–5. Trends may be further influenced by an unexplored factor—changes in the seasonal timing of {p}_{{{rm{CO}}}_{2}}. In Arctic Ocean surface waters, the observed timing is typified by a winter high and summer low6 because biological effects dominate thermal effects. Here we show that 27 Earth system models simulate similar timing under historical forcing but generally project that the summer low, relative to the annual mean, eventually becomes a high across much of the Arctic Ocean under mid-to-high-level CO2 emissions scenarios. Often the greater increase in summer {p}_{{{rm{CO}}}_{2}}, although gradual, abruptly inverses the chronological order of the annual high and low, a phenomenon not previously seen in climate-related variables. The main cause is the large summer sea surface warming7 from earlier retreat of seasonal sea ice8. Warming and changes in other drivers enhance this century’s increase in extreme summer {p}_{{{rm{CO}}}_{2}} by 29 ± 9 per cent compared with no change in driver seasonalities. Thus the timing change worsens summer ocean acidification, which in turn may lower the tolerance of endemic marine organisms to increasing summer temperatures.

Spatiotemporal Variations of Riverine CO2 Partial Pressure and its Effect on CO2 Flux at the Water–Air Interface in a Small Karst River

Spatiotemporal Variations of Riverine CO2 Partial Pressure and its Effect on CO2 Flux at the Water–Air Interface in a Small Karst River

Absence of visitors during lockdown reveals natural variation in carbon dioxide level in the Glowworm Cave, Waitomo, New Zealand

Waitomo Glowworm Cave is a highly visited cave where the highlight is viewing the bioluminescence display of a large colony of glowworms. Anthropogenic carbon dioxide build-up in the cave is prevented by management of chimney-effect ventilation aided by a network of microclimate sensors. A cave door prevents ventilationunder drying conditions and promotes it when necessary to clear CO2 and when inflowing air has high relative humidity. A COVID-19-related nationwide “lockdown” in New Zealand from March 2020 resulted in neither staff nor visitors being present in the cave for 60 days, and provided an opportunity to assess the natural microclimate of the cave, especially the natural variation in partial pressure of carbon dioxide (pCO2). In addition, comparison to the previous year showed that the presence of people in the cave increased the cave temperatures but the effect was short-lived due to cave ventilation. During the period of lockdown, the daily increase of carbon dioxide partial pressure (pCO2) due to visitors was absent. When the cave door remained sealed, pCO2 varied and tended to lie at levels above that of the external atmosphere (410 ppm). Notably, rain events raised pCO2 by up to 200 ppm (v/v), which appeared to be sourced from both stream water and drip water. These natural CO2 sources rarely reached the levels associated with cave visitation. The results support current management practices that use door control to enhance cave ventilation when people are in the cave or when natural conditions (high stream levels and high drip-water levels) promote CO2 outgassing into the cave. Suppressing ventilation outside of those times reduces the risk of introducing dry air that could desiccate the glowworms.

Sequential treatment of severe pneumonia with respiratory failure and its influence on respiratory mechanical parameters and hemodynamics.

BACKGROUNDThe pathophysiological characteristics of severe pneumonia complicated by respiratory failure comprise pulmonary parenchymal changes leading to ventilation imbalance, alveolar capillary injury, pulmonary edema, refractory hypoxemia, and reduced lung compliance. Prolonged hypoxia can cause acid-base balance disorder, peripheral circulatory failure, blood-pressure reduction, arrhythmia, and other adverse consequences.AIMTo investigate sequential mechanical ventilation’s effect on severe pneumonia complicated by respiratory failure. METHODSWe selected 108 patients with severe pneumonia complicated by respiratory failure who underwent mechanical ventilation between January 2018 and September 2020 at the Luhe Hospital’s Intensive Care Unit and divided them into sequential and regular groups according to a randomized trial, with each group comprising 54 patients. The sequential group received invasive and non-invasive sequential mechanical ventilation, whereas the regular group received invasive mechanical ventilation. Blood-gas parameters, hemodynamic parameters, respiratory mechanical parameters, inflammatory factors, and treatment outcomes were compared between the two groups before and after mechanical-ventilation treatment. RESULTSThe arterial oxygen partial pressure and stroke volume variation values of the sequential group at 24, 48, and 72 h of treatment were higher than those of the conventional group (P < 0.05). The carbon dioxide partial pressure value of the sequential group at 72 h of treatment and the Raw value of the treatment group at 24 and 48 h were lower than those of the conventional group (P < 0.05). The pH value of the sequential group at 24 and 72 h of treatment, the central venous pressure value of the treatment at 24 h, and the Cst value of the treatment at 24 and 48 h were higher than those of the conventional group (P < 0.05). The tidal volume in the sequential group at 24 h of treatment was higher than that in the conventional group (P < 0.05), the measured values of interleukin-6 and tumor necrosis factor-α in the sequential group at 72 h of treatment were lower than those in the conventional group (P < 0.05), and the total time of mechanical ventilation in the sequential group was shorter than that in the conventional group, with a statistically significant difference (P < 0.05).CONCLUSIONTreating severe pneumonia complicated by respiratory failure with sequential mechanical ventilation is more effective in improving respiratory system compliance, reducing inflammatory response, maintaining hemodynamic stability, and improving patient blood-gas levels; however, from this study’s perspective, it cannot reduce patient mortality.