Low pCO2 Research Articles

Prognostic Value of PCO2 Gap in Adult Septic Shock Patients: A Systematic Review and Meta-Analysis.

Sepsis cases caused substantial mortality and a significant burden on healthcare costs and resources. To tackle this problem, there has been discussion surrounding O2 parameters as it has a distinct outcome in septic patients. This review aimed to evaluate the prognostic value of the central venous-arterial carbon dioxide difference (PCO2) gap in patients with septic shock. A comprehensive systematic search was performed through electronic databases including Pubmed, Scopus, and Embase for studies focusing on the use of PCO2 gap as a mortality predictor in septic shock patients. Other secondary outcomes such as mean arterial pressure, lactate clearance, the acute physiology and chronic health evaluation II score, and intensive care unit length of stay were also measured. The Newcastle-Ottawa Scale tool was used to assess the risk of bias. A total of 8 studies were analysed. The mortality rate (odds ratio=0.50, 95% CI=0.28-0.87, P < .01) and lactate levels (mean difference [MD] = -0.98; 95% CI=-1.62 to -0.35; P=.001) of the low PCO2 gap group were significantly lower than the high gap group. The low gap group had a significantly higher mean arterial pressure compared to the high gap group (MD=4.54; 95% CI=2.14 to 6.95; P=.001). There were no pronounced outcomes in acute physiology and chronic health evaluation score and intensive care unit length of stay. PCO2 gap can potentially be used as a marker for mortality rate in septic shock patients. It is also significantly associated with other predictors, such as mean arterial pressure and lactate clearance.

Seasonality of precipitation in the southwestern United States during the late Pleistocene inferred from stable isotopes in herbivore tooth enamel

The late Pleistocene was a climatically dynamic period, with abrupt shifts between cool-wet and warm-dry conditions. Increased effective precipitation supported large pluvial lakes and long-lived spring ecosystems in valleys and basins throughout the western and southwestern U.S., but the source and seasonality of the increased precipitation are debated. Increases in the proportions of C4/(C4+ C3) grasses in the diets of large grazers have been ascribed both to increases in summer precipitation and lower atmospheric CO2 levels. Here we present stable carbon and oxygen isotope data from tooth enamel of late Pleistocene herbivores recovered from paleowetland deposits at Tule Spring Fossil Beds National Monument in the Las Vegas Valley of southern Nevada, as well as modern herbivores from the surrounding area. We use these data to investigate whether winter or summer precipitation was responsible for driving the relatively wet hydroclimate conditions that prevailed in the region during the late Pleistocene. We also evaluate whether late Pleistocene grass C4/(C4+ C3) was higher than today, and potential drivers of any changes.Tooth enamel δ18O values for Pleistocene Equus, Bison, and Mammuthus are generally low (average 22.0 ± 0.7‰, 2 s.e., VSMOW) compared to modern equids (27.8 ± 1.5‰), and imply lower water δ18O values (−16.1 ± 0.8‰) than modern precipitation (−10.5‰) or in waters present in active springs and wells in the Las Vegas Valley (−12.9‰), an area dominated by winter precipitation. In contrast, tooth enamel of Camelops (a browser) generally yielded higher δ18O values (23.9 ± 1.1‰), possibly suggesting drought tolerance. Mean δ13C values for the Pleistocene grazers (−6.6 ± 0.7‰, 2 s.e., VPDB) are considerably higher than for modern equids (−9.6 ± 0.4‰) and indicate more consumption of C4 grass (17 ± 5%) than today (4 ± 4%). However, calculated C4 grass consumption in the late Pleistocene is strikingly lower than the proportion of C4 grass taxa currently present in the valley (55–60%). δ13C values in Camelops tooth enamel (−7.7 ± 1.0‰) are interpreted as reflecting moderate consumption (14 ± 8%) of Atriplex (saltbush), a C4 shrub that flourishes in regions with hot, dry summers.Lower water δ18O values, lower abundance of C4 grasses, and the inferred presence of Atriplex are all consistent with general circulation models for the late Pleistocene that show enhanced delivery of winter precipitation, sourced from the north Pacific, into the interior western U.S. but do not support alternative models that infer enhanced delivery of summer precipitation, sourced from the tropics. In addition, we hypothesize that dietary competition among the diverse and abundant Pleistocene fauna may have driven the grazers analyzed here to feed preferentially on C4 grasses. Dietary partitioning, especially when combined with decreased pCO2 levels during the late Pleistocene, can explain the relatively high δ13C values observed in late Pleistocene grazers in the Las Vegas Valley and elsewhere in the southwestern U.S. without requiring additional summer precipitation. Pleistocene hydroclimate parameters derived from dietary and floral records may need to be reevaluated in the context of the potential effects of dietary preferences and lower pCO2 levels on the stability of C3 vs. C4 plants.

Clinical determinants and prognostic significance of hypocapnia in acute heart failure

The aim of this research was to examine the prevalence of hyperventilation (defined by pCO2 value) among acute heart failure (AHF) patients and to link it with potential triggers and prognosis. All patients underwent dyspnea severity assessment and capillary blood examination on hospital admission and during hospitalization. Out of 241 AHF patients, 57(24%) were assigned to low pCO2 group (pCO2 ≤ 30 mmHg) and 184 (76%) to normal pCO2 group (pCO2 > 30 mmHg). Low pCO2 group had significantly lower HCO3- (22.3 ± 3.4 vs 24.7 ± 2.9 mmol/L, p < 0.0001) and significantly higher lactate level (2.53 ± 1.6 vs 2.14 ± 0.97 mmol/L, p = 0.03). No differences between groups were observed in respect to the following potential triggers of hyperventilation: hypoxia (sO2 92.5 ± 5.2 vs 92 ± 5.6% p = 0.57), infection (CRP 10.5[4.9–26.4]vs 7.15[3.45–17.35] mg/L, p = 0.47), dyspnea severity (7.8 ± 2.3vs 8.0 ± 2.3 points, p = 0.59) and pulmonary congestion (82.5 vs 89.1%, p = 0.19), respectively. Low pCO2 value was related to an increased 4-year all-cause mortality hazard ratio (HR) (95% CI) 2.2 (1.3–3.6); p = 0.002 and risk of death and of rehospitalization for HF, HR (95% CI) 2.0 (1.3–3.0); p = 0.002. Hyperventilation is relatively frequent in AHF and is related to poor prognosis. Low pCO2 was not contingent on expected potential triggers of dyspnea but rather on tissue hypoperfusion.

Interaction between seawater carbon dioxide dynamics and stratification in shallow coastal waters: A preliminary study based on a weekly validated three-dimensional ecological model

Shallow coastal waters (SCWs) have attracted wide attention in recent years due to their strong carbon sequestration capacity. However, the complex carbon dioxide (CO2) dynamics in the water column makes it difficult to estimate the air–water CO2 fluxes (FCO2) accurately. We developed a numerical model of CO2 dynamics in water based on field measurements for a typical stratified semi-enclosed shallow bay: the Yatsushiro Sea, Japan. The developed model showed an excellent ability to reproduce the stratification and CO2 dynamics of the Yatsushiro Sea. Through numerical model simulations, we analyzed the annual CO2 dynamics in the Yatsushiro Sea in 2018. The results show that the effect of stratification on the CO2 dynamics in seawater varies greatly depending on the distance from the estuary and the period. In the estuarine region, stratification manifests itself throughout the year by promoting the maintenance of a high partial pressure of CO2 (pCO2) in surface waters, resulting in surface pCO2 being higher than atmospheric pCO2 for up to 40 days during the flood period (average surface pCO2 of 539.94 µatm). In contrast, in areas farther from the estuary, stratification mainly acts to promote the maintenance of high pCO2 in surface waters during periods of high freshwater influence. Then changes to a lower surface pCO2 before the freshwater influence leads towards complete dissipation. Finally, we estimated the FCO2 of the Yatsushiro Sea in 2018, and the results showed that the Yatsushiro Sea was a sink area for atmospheric CO2 in 2018 (−1.70 mmol/m2/day).

Boosting ethanol production rates from carbon dioxide in MES cells under optimal solventogenic conditions

Microbial Electrosynthesis (MES) has been widely applied for acetic acid (HA) production from CO2 and electricity. Ethanol (EtOH) has a higher market value than HA, and wide application in industry and as a biofuel. However, it has only been obtained sporadically and at low concentrations, probably due to sub-optimal operating conditions. This study aimed at enhancing EtOH productivity in MES cells by jointly optimising key operation parameters, including pH, H2 and CO2 partial pressure (pH2 and pCO2), and HA concentration, to promote solventogenesis. Two H-type cells were operated in fed-batch mode at −0.8 V vs. SHE with CO2 as the sole carbon source. A mixed culture, enriched with Clostridium ljungdahlii was used as the biocatalyst. The combination of low pH (<4.5) and pCO2 (<0.3 atm), along with high HA concentration (about 6 g L−1) and pH2 (>3 atm), were mandatory conditions for maintaining an efficient solventogenic culture, dominated by Clostridium sp., capable of high-rate EtOH production. The maximum EtOH production rate was 10.95 g m−2 d−1, and a concentration of 5.28 g L−1 was achieved. Up to 30 % of the electrons and 15.2 % of the carbon provided were directed towards EtOH production, and 28.1 kWh were required for the synthesis of 1 kg of EtOH from CO2. These results highlight that strict conditions are required for a continuous, reliable, EtOH production in MES cells. Future investigation should focus on improving cell configuration to achieve EtOH production at higher current densities while minimizing the electric energy input.

Automated preparation of washed platelet concentrates through spinning-membrane filtration.

Washed platelet concentrates (WPC), prepared with an automated system cell processor (ACP), have recently been approved to be manufactured and marketed in Japan. From the perspective of risk management, it is preferable to secure alternative technologies for ACP. Here, we conducted a study to evaluate the quality of WPC prepared using an automated membrane filtration-based system, Lovo. Replaced PCs prepared from apheresis PCs were equally divided into control and test units, and subsequently washed using ACP and Lovo respectively. Work and operational efficiencies were evaluated by in vitro analyses, including total handling time, platelet recovery, and plasma protein removal rate. Product quality, including a set of biochemical and physiological indicators of platelets and supernatants, were assessed before and 3 days after washing. In vitro platelet recovery rates and plasma protein removal rates were >85% and >95%, respectively, in both groups. The pH values on day 0 were significantly high (6.97 vs. 6.86) due to low pCO2 in the test group, while no significant differences in glucose consumption and lactate production were observed between the two groups. The levels of hypotonic shock responses, aggregation response, platelet shape, CD62P expression, and sCD62P concentration were similar in both groups during the 3-day storage period. Platelet washing with Lovo provides platelet quality equivalent to, or better than, conventional washing with ACP. Thus, the new automated system, Lovo, can be considered as an alternative to ACP for WPC preparation.

Mesophyll conductance response to short-term changes in pCO2 is related to leaf anatomy and biochemistry in diverse C4 grasses.

Mesophyll CO2 conductance (gm ) in C3 species responds to short-term (minutes) changes in environment potentially due to changes in leaf anatomical and biochemical properties and measurement artefacts. Compared with C3 species, there is less information on gm responses to short-term changes in environmental conditions such as partial pressure of CO2 (pCO2 ) across diverse C4 species and the potential determinants of these responses. Using 16 C4 grasses we investigated the response of gm to short-term changes in pCO2 and its relationship with leaf anatomy and biochemistry. In general, gm increased as pCO2 decreased (statistically significant increase in 12 species), with percentage increases in gm ranging from +13% to +250%. Greater increase in gm at low pCO2 was observed in species exhibiting relatively thinner mesophyll cell walls along with greater mesophyll surface area exposed to intercellular air spaces, leaf N, photosynthetic capacity and activities of phosphoenolpyruvate carboxylase and Rubisco. Species with greater CO2 responses of gm were also able to maintain their leaf water-use efficiencies (TEi ) under low CO2 . Our study advances understanding of CO2 response of gm in diverse C4 species, identifies the key leaf traits related to this response and has implications for improving C4 photosynthetic models and TEi through modification of gm .

Genetic variation underlies plastic responses to global change drivers in the purple sea urchin, Strongylocentrotus purpuratus.

Phenotypic plasticity and adaptive evolution enable population persistence in response to global change. However, there are few experiments that test how these processes interact within and across generations, especially in marine species with broad distributions experiencing spatially and temporally variable temperature and pCO2. We employed a quantitative genetics experiment with the purple sea urchin, Strongylocentrotus purpuratus, to decompose family-level variation in transgenerational and developmental plastic responses to ecologically relevant temperature and pCO2. Adults were conditioned to controlled non-upwelling (high temperature, low pCO2) or upwelling (low temperature, high pCO2) conditions. Embryos were reared in either the same conditions as their parents or the crossed environment, and morphological aspects of larval body size were quantified. We find evidence of family-level phenotypic plasticity in response to different developmental environments. Among developmental environments, there was substantial additive genetic variance for one body size metric when larvae developed under upwelling conditions, although this differed based on parental environment. Furthermore, cross-environment correlations indicate significant variance for genotype-by-environment interactive effects. Therefore, genetic variation for plasticity is evident in early stages of S. purpuratus, emphasizing the importance of adaptive evolution and phenotypic plasticity in organismal responses to global change.

Interactive effects of CO2 , temperature, irradiance, and nutrient limitation on the growth and physiology of the marine cyanobacterium Synechococcus (Cyanophyceae).

The marine cyanobacterium Synechococcus elongatus was grown in a continuous culture system to study the interactive effects of temperature, irradiance, nutrient limitation, and the partial pressure of CO2 (pCO2) on its growth and physiological characteristics. Cells were grown on a 14:10 h light:dark cycle at all combinations of low and high irradiance (50 and 300 μmol photons ⋅ m-2 ⋅ s-1 , respectively), low and high pCO2 (400 and 1000 ppmv, respectively), nutrient limitation (nitrate-limited and nutrient-replete conditions), and temperatures of 20-45°C in 5°C increments. The maximum growth rate was ~4.5 · d-1 at 30-35°C. Under nutrient-replete conditions, growth rates at most temperatures and irradiances were about 8% slower at a pCO2 of 1000 ppmv versus 400 ppmv. The single exception was 45°C and high irradiance. Under those conditions, growth rates were ~45% higher at 1000 ppmv. Cellular carbon:nitrogen ratios were independent of temperature at a fixed relative growth rate but higher at high irradiance than at low irradiance. Initial slopes of photosynthesis-irradiance curves were higher at all temperatures under nutrient-replete versus nitrate-limited conditions; they were similar at all temperatures under high and low irradiance, except at 20°C, when they were suppressed at high irradiance. A model of phytoplankton growth in which cellular carbon was allocated to structure, storage, or the light or dark reactions of photosynthesis accounted for the general patterns of cell composition and growth rate. Allocation of carbon to the light reactions of photosynthesis was consistently higher at low versus high light and under nutrient-replete versus nitrate-limited conditions.

Responses of Freshwater Calcifiers to Carbon-Dioxide-Induced Acidification

Increased anthropogenic carbon dioxide (CO2) in the atmosphere can enter surface waters and depress pH. In marine systems, this phenomenon, termed ocean acidification (OA), can modify a variety of physiological, ecological, and chemical processes. Shell-forming organisms are particularly sensitive to this chemical shift, though responses vary amongst taxa. Although analogous chemical changes occur in freshwater systems via absorption of CO2 into lakes, rivers, and streams, effects on freshwater calcifiers have received far less attention, despite the ecological importance of these organisms to freshwater systems. We exposed four common and widespread species of freshwater calcifiers to a range of pCO2 conditions to determine how CO2-induced reductions in freshwater pH impact calcium carbonate shell formation. We incubated the signal crayfish, Pacifastacus leniusculus, the Asian clam, Corbicula fluminea, the montane pea clam, Pisidium sp., and the eastern pearlshell mussel, Margaritifera margaritifera, under low pCO2 conditions (pCO2 = 616 ± 151 µatm; pH = 7.91 ± 0.11), under moderately elevated pCO2 conditions (pCO2 = 1026 ± 239 uatm; pH = 7.67 ± 0.10), and under extremely elevated pCO2 conditions (pCO2 = 2380 ± 693 uatm; pH = 7.32 ± 0.12). Three of these species exhibited a negative linear response to increasing pCO2 (decreasing pH), while the fourth, the pea clam, exhibited a parabolic response. Additional experiments revealed that feeding rates of the crayfish decreased under the highest pCO2 treatment, potentially contributing to or driving the negative calcification response of the crayfish to elevated pCO2 by depriving them of energy needed for biocalcification. These results highlight the potential for freshwater taxa to be deleteriously impacted by increased atmospheric pCO2, the variable nature of these responses, and the need for further study of this process in freshwater systems.

Understanding the Implications of Hydrographic Processes on the Dynamics of the Carbonate System in a Sub-Antarctic Marine-Terminating Glacier-Fjord (53°S)

The biogeochemical dynamics of fjords in the southeastern Pacific Ocean are strongly influenced by hydrological and oceanographic processes occurring at a seasonal scale. In this study, we describe the role of hydrographic forcing on the seasonal variability of the carbonate system of the Sub-Antarctic glacial fjord, Seno Ballena, in the Strait of Magellan (53°S). Biogeochemical variables were measured in 2018 during three seasonal hydrographic cruises (fall, winter and spring) and from a high-frequency pCO2-pH mooring for 10 months at 10 ± 1 m depth in the fjord. The hydrographic data showed that freshwater input from the glacier influenced the adjacent surface layer of the fjord and forced the development of undersaturated CO2 (&amp;lt; 400 μatm) and low aragonite saturation state (ΩAr &amp;lt; 1) water. During spring, the surface water had relatively low pCO2 (mean = 365, range: 167 - 471 μatm), high pH (mean = 8.1 on the total proton concentration scale, range: 8.0 - 8.3), and high ΩAr (mean = 1.6, range: 1.3 - 4.0). Concurrent measurements of phytoplankton biomass and nutrient conditions during spring indicated that the periods of lower pCO2 values corresponded to higher phytoplankton photosynthesis rates, resulting from autochthonous nutrient input and vertical mixing. In contrast, higher values of pCO2 (range: 365 – 433 μatm) and relatively lower values of pHT (range: 8.0 – 8.1) and ΩAr (range: 0.9 – 2.0) were recorded in cold surface waters during winter and fall. The naturally low freshwater carbonate ion concentrations diluted the carbonate ion concentrations in seawater and decreased the calcium carbonate saturation of the fjord. In spring, at 10 m depth, higher primary productivity caused a relative increase in ΩAr and pHT. Assuming global climate change will bring further glacier retreat and ocean acidification, this study represents important advances in our understanding of glacier meltwater processes on CO2 dynamics in glacier–fjord systems.

The relationship between ventilatory ratio (VR) and 28-day hospital mortality by restricted cubic splines (RCS) in 14,328 mechanically ventilated ICU patients

BackgroundPrevious studies found that high levels of ventilatory ratio (VR) were associated with a poor prognosis due to worse ventilatory efficiency in acute respiratory distress syndrome patients. However, relatively few large studies have assessed the association between VR and intensive care unit (ICU) mortality in the general adult ventilated population.MethodsThe present study is a retrospective cohort study. Patients mechanically ventilated for more than 12 h were included. VR was calculated based on a previously reported formula. Restricted cubic spline models were used to fit the relationship between VR and mortality risks.ResultsA total of 14,328 mechanically ventilated ICU patients were included in the study, of which 1311 died within 28 days. The results of the study are as follows: (1) In the general adult ventilated population, VR was positively associated with 28-day mortality when VR ≥ 1.3 (increase of 0.1 per VR; HR 1.05, p < 0.001). The same tendency was also observed in the populations of severe hypoxemia with a PaO2/FiO2 (P/F) ratio < 200 mmHg. (2) However, in the population with a P/F ratio ≥ 200, a J-shaped dose–response association between VR and the risk of mortality was observed, with the risk of death positively associated with VR when VR ≥ 0.9 (10% increase in HR for every 0.1 increase in VR, p = 0.000) but negatively associated with VR when VR < 0.9 (10% decrease in HR for every 0.1 increase in VR, p = 0.034). In the population of P/F ratio ≥ 200 with VR less than 0.9, compared to the survival group, the nonsurvival group had a lower level PCO2 (33 mmHg [29.1, 37.9] vs. 34.4 mmHg [30.6, 38.5]), rather than a significant level of measured minute ventilation or P/F ratio.ConclusionsVR was positively associated with the risk of death in the general ICU population; however, VR was inversely associated with 28-day mortality in the population with a P/F ratio ≥ 200 and low VR . Further research should investigate this relationship, and VR should be interpreted with caution in clinical practice.

Meta-analysis suggests negative, but pCO2-specific, effects of ocean acidification on the structural and functional properties of crustacean biomaterials.

Crustaceans comprise an ecologically and morphologically diverse taxonomic group. They are typically considered resilient to many environmental perturbations found in marine and coastal environments, due to effective physiological regulation of ions and hemolymph pH, and a robust exoskeleton. Ocean acidification can affect the ability of marine calcifying organisms to build and maintain mineralized tissue and poses a threat for all marine calcifying taxa. Currently, there is no consensus on how ocean acidification will alter the ecologically relevant exoskeletal properties of crustaceans. Here, we present a systematic review and meta‐analysis on the effects of ocean acidification on the crustacean exoskeleton, assessing both exoskeletal ion content (calcium and magnesium) and functional properties (biomechanical resistance and cuticle thickness). Our results suggest that the effect of ocean acidification on crustacean exoskeletal properties varies based upon seawater pCO2 and species identity, with significant levels of heterogeneity for all analyses. Calcium and magnesium content was significantly lower in animals held at pCO2 levels of 1500–1999 µatm as compared with those under ambient pCO2. At lower pCO2 levels, however, statistically significant relationships between changes in calcium and magnesium content within the same experiment were observed as follows: a negative relationship between calcium and magnesium content at pCO2 of 500–999 µatm and a positive relationship at 1000–1499 µatm. Exoskeleton biomechanics, such as resistance to deformation (microhardness) and shell strength, also significantly decreased under pCO2 regimes of 500–999 µatm and 1500–1999 µatm, indicating functional exoskeletal change coincident with decreases in calcification. Overall, these results suggest that the crustacean exoskeleton can be susceptible to ocean acidification at the biomechanical level, potentially predicated by changes in ion content, when exposed to high influxes of CO2. Future studies need to accommodate the high variability of crustacean responses to ocean acidification, and ecologically relevant ranges of pCO2 conditions, when designing experiments with conservation‐level endpoints.

P274 GUESS WHO‘S COMING TO REANIMATION? ANALYSIS OF THE ELDERLY PATIENT WITH EMBOLISM IN NEED OF HOSPITALIZATION IN INTENSIVE CARE: REAL LIFE IN THE EMERGENCY ROOM

Abstract Premise Pulmonary embolism is a disease still characterized by high mortality and which may require hospitalization in intensive care. Purpose Evaluate which parameters, in the real life of an Emergency Department, correlate with the need and the duration of hospitalization in intensive care. Methods Single–center retrospective observational study, on all geriatric patients (&amp;gt; 75) who refer to our ED, where they were diagnosed with acute PE. Enrollment began in 2015 and ended in 2019. We collected data from medical history, physical examination, laboratory tests, imaging, outcomes. Results We enrolled 247 patients, with a mean age of 83 years and female prevalence (F = 63%). Of these 12 (14 %) required hospitalization in intensive care from the emergency room. Regarding the need for hospitalization in resuscitation, age and vital parameters (arterial pressure, respiratory rate, heart rate), as well as derived shock indices are not correlated (p &amp;gt; 0.05). Only the systolic blood pressure values and it show a trend which however does not reach statistical significance (p = 0.06). Among the blood gas analysis parameters, only low pCO2 has a slight correlation (p &amp;lt; 0.05). The D–Dimer (p &amp;lt; 0.01) and creatinine values (p &amp;lt; 0.05) show correlation between the blood chemistry tests. Regarding the length of stay in resuscitation, age and vital parameters (blood pressure, respiratory rate, heart rate), as well as derived shock indices, do not show any correlation (rho∼0; p &amp;gt; 0.05). A weak correlation is instead present with high values of D–Dimer (rho∼0.25; p &amp;lt; 0.005) and creatinine (rho∼0.33; p &amp;lt; 0.0005). The presence of massive pulmonary embolism shows no correlation (p &amp;gt; 0.5). The presence of organ damage, on the other hand, correlates in a statistically significant manner (p &amp;lt; 0.0005). Excellent correlation is shown by the sPESI index (p &amp;lt; 0.0001). Discrete correlation showed the alteration in pH (rho∼0.61; p &amp;lt; 0.0001). Correlation for the blood gas analysis parameters taken into consideration (pH; pO2; pCO2; lactates). Conclusions The study suggests a reduced significance of vital parameters and indices derived from them for the need and duration of hospitalization in resuscitation. Presence of organ damage, low pCO2 values and high D–Dimer and creatinine values are associated with both the need for hospitalization in resuscitation and duration.

Listriodon dukkar sp. nov. (Suidae, Artiodactyla, Mammalia) from the late Miocene of Pasuda (Gujarat, India): the decline and extinction of the Listriodontinae

The Listriodontinae were a common and widespread group of Suidae (pigs) that lived in an area extending from Portugal to China and to southern Africa. Here, we describe the new species Listriodon dukkar from Pasuda (Gujarat, India). It shares features with Li. pentapotamiae, evolved from it, and is the last representative of this lineage. The Listriodontinae flourished for about 10 million years, reached their maximum diversity and geographic extension during the Mid-Miocene Climatic Optimum (about 17–13.6 Ma), and their last records are close in age and date to ~ 9.8 Ma in the Indian Subcontinent, 9.78 Ma in Europe, and ~ 10 Ma in Africa. We review the environments in which the last listriodont lineages lived and went extinct. Their extinctions occurred against a background of increasing seasonality, vegetation change, a rise in bovid diversity and abundance, and local events, such as the European Vallesian Crisis and a dramatic drop in tragulid abundance in the Siwaliks. However, changes in the atmospheric pCO2 may have contributed to their decline and extinction in all their geographic distribution. Decreasing pCO2 is expected to have decreased sugar content and increased protein content of leaves and fruit. Hindgut fermenting Suoidea have higher protein requirements, while foregut fermenting Suoidea are more efficient in digesting sugars. Listriodontinae were probably foregut fermenters and were less well adapted in a low pCO2 world.

Effects of High-Frequency Oscillatory Ventilation With Volume Guarantee During Surfactant Treatment in Extremely Low Gestational Age Newborns With Respiratory Distress Syndrome: An Observational Study.

ObjectiveTo evaluate the effect of volume guarantee (VG) combined with high-frequency oscillatory ventilation (HFOV) on respiratory and other physiological parameters immediately after lung recruitment and surfactant administration in HFOV elective ventilated extremely low gestational age newborns (ELGAN) with respiratory distress syndrome (RDS).DesignObservational study.SettingTertiary neonatal intensive care unit.PatientsTwenty-two ELGANs of 25.5 ± 1.1 weeks of gestational age requiring invasive mechanical ventilation and surfactant administration for RDS during the first 6 h of life.InterventionsAll infants intubated in delivery room, were managed with elective HFOV and received surfactant after a lung recruitment manoeuver. Eleven infants received HFOV + VG and were compared with a control group of 11 infants receiving HFOV alone. HFOV was delivered in both groups by Dräger Babylog VN500 ventilator (Dräger, Lubeck, Germany).Main Outcome MeasuresVariations and fluctuations of delivered high-frequency tidal volume (VThf), fluctuation of pressure amplitude (ΔP) and partial pressure of CO2 (pCO2) levels after recruitment manoeuver and immediately after surfactant administration, in HFOV + VG vs. HFOV ventilated infants.ResultsThere were no significant differences in the two groups at starting ventilation with or without VG. The mean applied VThf per kg was 1.7 ± 0.3 ml/kg in the HFOV group and 1.7 ± 0.1 ml/kg in the HFOV + VG group. Thirty minutes after surfactant administration, HFOV group had a significant higher VThf/Kg than HFOV + VG (2.1 ± 0.3 vs. 1.6 ± 0.1 ml/kg, p < 0.0001) with significantly lower pCO2 levels (43.1 ± 3.8 vs. 46.8 ± 1.5 mmHg, p = 0.01), 54.4% of patients having pCO2 below 45 mmHg. Measured post-surfactant ΔP values were higher in HFOV group (17 ± 3 cmH2O) than in HFOV + VG group (13 ± 3 cmH2O, p = 0.01).ConclusionHFOV + VG maintains pCO2 levels within target range and reduces VThf delivered variations more consistently than HFOV alone after surfactant administration.

Autonomous Wintertime Observations of Air‐Sea Exchange in the Gulf Stream Reveal a Perfect Storm for Ocean CO2 Uptake

AbstractA scarcity of wintertime observations of surface ocean carbon dioxide partial pressure (pCO2) in and near the Gulf Stream creates uncertainty in the magnitude of the regional carbon sink and its controlling mechanisms. Recent observations from an Uncrewed Surface Vehicle (USV), outfitted with a payload to measure surface ocean and lower atmosphere pCO2, revealed sharp gradients in ocean pCO2 across the Gulf Stream. Surface ocean pCO2 was lower by ∼50 μatm relative to the atmosphere in the subtropical mode water (STMW) formation region. This undersaturation combined with strong wintertime winds allowed for rapid ocean uptake of CO2, averaging −11.5 mmol m−2 day−1 during the February 2019 USV mission. The unique timing of this mission revealed active STMW formation. The USV proved to be a useful tool for CO2 flux quantification in the poorly observed, dynamic western boundary current environment.

Cerebrospinal Fluid and Arterial Acid–Base Equilibrium of Spontaneously Breathing Patients with Aneurismal Subarachnoid Hemorrhage

BackgroundHyperventilation resulting in hypocapnic alkalosis (HA) is frequently encountered in spontaneously breathing patients with acute cerebrovascular conditions. The underlying mechanisms of this respiratory response have not been fully elucidated. The present study describes, applying the physical–chemical approach, the acid-base characteristics of cerebrospinal fluid (CSF) and arterial plasma of spontaneously breathing patients with aneurismal subarachnoid hemorrhage (SAH) and compares these results with those of control patients. Moreover, it investigates the pathophysiologic mechanisms leading to HA in SAH.MethodsPatients with SAH admitted to the neurological intensive care unit and patients (American Society of Anesthesiologists physical status of 1 and 2) undergoing elective surgery under spinal anesthesia were enrolled. CSF and arterial samples were collected simultaneously. Electrolytes, strong ion difference (SID), partial pressure of carbon dioxide (PCO2), weak noncarbonic acids (ATOT), and pH were measured in CSF and arterial blood samples.ResultsTwenty spontaneously breathing patients with SAH and 25 controls were enrolled. The CSF of patients with SAH, as compared with controls, was characterized by a lower SID (23.1 ± 2.3 vs. 26.5 ± 1.4 mmol/L, p < 0.001) and PCO2 (40 ± 4 vs. 46 ± 3 mm Hg, p < 0.001), whereas no differences in ATOT (1.2 ± 0.5 vs. 1.2 ± 0.2 mmol/L, p = 0.95) and pH (7.34 ± 0.06 vs. 7.35 ± 0.02, p = 0.69) were observed. The reduced CSF SID was mainly caused by a higher lactate concentration (3.3 ± 1.3 vs. 1.4 ± 0.2 mmol/L, p < 0.001). A linear association (r = 0.71, p < 0.001) was found between CSF SID and arterial PCO2. A higher proportion of patients with SAH were characterized by arterial HA, as compared with controls (40 vs. 4%, p = 0.003). A reduced CSF-to-plasma difference in PCO2 was observed in nonhyperventilating patients with SAH (0.4 ± 3.8 vs. 7.8 ± 3.7 mm Hg, p < 0.001).ConclusionsPatients with SAH have a reduction of CSF SID due to an increased lactate concentration. The resulting localized acidifying effect is compensated by CSF hypocapnia, yielding normal CSF pH values and resulting in a higher incidence of arterial HA.

Prenatal or postnatal corticosteroids favor clinical, respiratory, metabolic outcomes and oxidative balance of preterm lambs corticotherapy for premature neonatal lambs

Challenges of the extrauterine environment can be life threatening for a premature fetus with inadequate fetal maturity. Maternal corticosteroids therapy is widely employed to induce fetal pulmonary maturation. Nevertheless, whenever therapeutic pregnancy interruption has to be performed in a time manner insufficient to treat the dam, postnatal corticotherapy can be considered an alternative. However, it is not known if antenatal and postnatal corticotherapy can improve similarly neonatal outcomes and pulmonary function. This research aimed to analyze antenatal and postnatal corticotherapy on premature lambs vitality, pulmonary functioning, metabolic and oxidative status. Lambs were evaluated according to the mode of treatment: Prenatal Corticosteroid Group (8 lambs born after maternal betamethasone treatment 48 h prior to birth), Postnatal Corticosteroid Group (9 lambs subjected to betamethasone treatment 10 min after birth) and Control Group (5 lambs remained untreated). Lambs were medically followed-up from birth to 72 h thereafter through a complete physical examination, as well as lactatemia, glycaemia, blood acid-base balance and antioxidant status. Treated lambs had higher vitality score than the Control Group. Heart rate was higher in postnatal therapy compared to prenatal treatment. Respiratory rate and rectal temperature were higher in treated groups. Treated lambs had hyperglycemia, while the Postnatal Group had higher lactatemia than the Control Group. The Prenatal Group had lower and normal pCO2 from 60 min onwards. The Postnatal Group had higher superoxide dismutase activity than untreated lambs. In conclusion, prenatal and postnatal betamethasone treatments favor neonatal clinical outcome, respiratory function, glucose homeostasis and oxidative balance.

Early predictors of high-flow nasal cannula oxygen treatment failure in patients with respiratory distress admitted to the pediatric emergency department.

High-flow nasal cannula (HFNC) therapy is a relatively new method used in patients with respiratory distress. The aim of the study was to evaluate the outcomes and to determine the baseline predictors of HFNC treatment failure in children with acute respiratory distress/failure in the pediatric emergency department. Children with respiratory distress/failure aged 1 month to 18 years who underwent HFNC therapy with the pre-established protocol were retrospectively analyzed. HFNC therapy was used in respiratory and non-respiratory pathologies. HFNC failure was defined as the need for escalation to non-invasive ventilation or invasive mechanical ventilation. HFNC responders and non-responders were compared based on baseline clinical data. Of the 524 cases (median age:13 months; 292 males / 232 females), 484 (92.4%) had respiratory tract and 40 (7.6%) had non-respiratory tract pathologies. HFNC therapy was unsuccessful in 62 (11.8%) patients. The success rates were 81% and 55% in respiratory and non-respiratory diseases, respectively. In children with respiratory system pathologies, the pre-treatment venous pCO2 level (p: 0.045; OR: 0.958; 95%CI: 0.821-0.990) and the clinically important radiological finding on chest X-ray (lobar infiltration, atelectasis, pleural effusion) (p: 0.045; OR: 3.262; 95%CI: 1.178-9.034) were the most significant parameters in predicting HFNC failure. In children with non-respiratory pathologies, the pre-treatment venous lactate level (p: 0.008; OR: 1.558; 95%CI: 1.125-2.158) was a significant predictor of HFNC failure. There were no cases of pneumothorax or any other reported adverse effects related to HFNC therapy. HFNC treatment is a safe oxygen therapy in children with respiratory distress/failure due to various etiologies in the emergency department. The lower venous pCO2 level increases and the clinically important radiological finding on chest radiograph decreases the success of HFNC treatment in respiratory pathologies. The higher venous lactate level is a predictor of HFNC treatment failure in non-respiratory pathologies.