Oxygen Utilization Research Articles

Determinants of Longitudinal Changes in Exercise Capacity in Patients with Independent Functioning on Hemodialysis.

Patients with chronic kidney disease reportedly have decreased muscle oxygen utilization, which most substantially decreases exercise capacity, followed by cardiac reserve. However, determinants of longitudinal changes in exercise capacity in patients on hemodialysis and the effects of long-term exercise interventions are unknown. This study was conducted to clarify these concerns. This was a prospective cohort study. Patients on hemodialysis that were not hospitalized were followed from baseline up to 2years, and cardiopulmonary exercise testing results, including peak oxygen uptake, peak work rate, heart rate reserve, and ventilatory equivalent for carbon dioxide slope, as well as implementation of exercise interventions were assessed. Based on the 2-year change in peak oxygen uptake, they were divided into improvement or declined groups. Forty-five patients who were not hospitalized completed the follow-up were analyzed. In the improvement group, the variation was determined by an increase in peak work rate, which is a peripheral factor (partial regression coefficient 0.08 [95% CI = 0.01 to 0.16]), while in the decline group, the variation was determined by a decrease in the ventilatory equivalent for carbon dioxide slope, which is a cardiac factor (partial regression coefficient = -0.12; 95% CI = -0.21 to -0.03). Moreover, exercise intervention was associated with the change in peak oxygen uptake (partial regression coefficient = 3.09; 95% CI = 1.45 to 4.72). Exercise intolerance even in patients on hemodialysis that were not hospitalized and stable progressed over time with deterioration of cardiac reserve, whereas exercise interventions were associated with improved exercise capacity through enhanced peripheral function. The results support the early measurement of cardiopulmonary or skeletal muscle reserve through cardiopulmonary exercise testing and the implementation of long-term exercise interventions based on the measurement results to address the potential deterioration in exercise capacity associated with reduced cardiac reserve, even in patients on hemodialysis that are asymptomatic and stable.

Predicting the impact of underwater skimming on dissolved oxygen consumption in slow sand filters for potable water treatment

In a well-functioning slow sand filter (SSF), dissolved oxygen (DO) is crucial for enabling aerobic processes and microbiota growth. Given that DO supply is predominantly via the feed water, flow pauses (e.g., during cleaning) may trigger anoxic/anaerobic conditions in the stagnant filter bed. Underwater skimming (UWS) is an advanced cleaning technique that employs a skimmer with a shrouded blade, mounted on a mobile platform, to remove the fouling layer composed of sand and particles in order to improve the efficiency of slow sand filtration. As UWS results in changes to the flow pattern of the SSF, a mathematical model was developed to predict DO utilization after a flow perturbation associated with UWS operation. The model was based on a depth resolved measurement of specific oxygen utilization derived from a full scale SSF. Pilot plant experiments monitored DO in the feed and filtrate of SSFs cleaned using underwater and conventional dry skimming techniques. The highest oxygen utilization was in the Schmutzdecke layer, with additional demand imposed by the presence of a granular activated carbon (GAC) sandwich layer. It was observed that pseudo-steady state conditions occurred following filter ripening, where DO utilization, driven by biological activity, remained relatively constant regardless of filter cleaning technique. For flow pauses between three and 24 h, the pause duration's importance decreased, while the hydraulic loading rate became the critical factor for DO recovery in the filter. Additionally, introducing a ‘sweetening flow’ during UWS ensured a continuous DO supply, facilitating quicker DO replenishment post-cleaning. The model reliably predicted filtrate DO within ±0.6 mg/L, demonstrating its operational utility, especially in the optimisation of UWS methodology. As such, UWS can be applied to clean SSFs with the methodology modified to prevent any detrimental effects to DO management within the filter. This study predicted DO dynamics in SSFs, advancing UWS techniques and could be applied for enhancing water treatment strategies by filtration.

Physiological parameters and training characteristics of endurance runners at Ethiopian Youth Sports Academy (2400 meters above sea level) and Guna Athletics Sport Club (3100 meters above sea level) training camps: a comparative cross-sectional study.

Endurance performance is impacted by physiological, anthropometrical, diet, genetic, psychological, and training characteristics. Altitude can affect physiological parameters (like maximum oxygen utilization, arterial oxygen saturation (SaO<inf>2</inf>), heart rate, and blood pressure) and training characteristics (duration, frequency, and training load). Thus, this study compared physiological parameters and training characteristics between endurance runners at Ethiopian Youth Sports Academy (EYSA) and Guna Athletics Sport Club (GASC) located which are located at elevation of 2400 and 3100 meters, respectively. A comparative cross-sectional study design was used from September to November 2021. Data was obtained from a total of 120 eligible participants (30 runners and 30 controls at GASC, and 30 runners and 30 controls at EYSA). Sociodemographic and training characteristics were assessed using self-administered standardized questionnaires. SaO<inf>2</inf> and heart rate were measured using finger pulse-oximetry (Nellcor, Oxim N-65; Covidien, Dublin, Ireland). Blood pressure was measured by Folee Digital Blood Pressure Monitor DX-B1 (Jiangsu Folee Medical Equipment Co., Ltd., Zhenjiang, China). The runners of GASC had significantly lower resting SaO<inf>2</inf>, SaO<inf>2</inf> immediately after maximal exertion, training (frequency and load) than runners of EYSA in both sexes. Runners of Guna Athletics Sport Club (RGASC) had significantly higher maximum oxygen utilization (VO<inf>2</inf>max) than Runners Ethiopian Youth Sports Academy (REYSA) in both sexes. Severe exercise-induced hypoxemia (EIAH) and moderate EIAH were developed by male runners of GASC and EYSA respectively. Besides, female runners GASC and EYSA developed moderate and mild EIAH, respectively. Conclusively, there were significant differences in physiological parameters and training load between RGASC and REYSA. High altitude (3100 meters) may have a greater impact on the above variables than moderate hypoxia (2400 meters above sea level). Hence, endurance runner coaches should give emphasis to these variables.

Linking ecological niche and metabolic hierarchy in low-oxygen-driven anammox systems

Dissolved oxygen (DO) is regarded as a key regulatory factor for the practical engineering applications of anaerobic ammonium oxidation (anammox) processes, however, the adaptability and metabolic mechanisms of floc anammox consortia with low-oxygen as potential substrates involved in the holistic microbial metabolic system are still elusive. This study showed that the nitrogen removal efficiency (NRE) of floc anammox consortia was 16.45% and 35.71% higher at DO of 0.2–0.5 mg·L−1 than at DO <0.2 mg·L−1 and DO of 0.5–0.8 mg·L−1, respectively. Meanwhile, the activity of anammox bacteria (AnAOB) and ammonia-oxidizing bacteria (AOB) was the highest, representing 22.64 ± 3.20 mg N·g−1 V SS·d−1 and 103.22 ± 6.47 mg N·g−1 VSS·d−1, respectively. AnAOB applied the antioxidant enzymes (CCP, T-SOD) and Cbb3-type cytochrome c oxidase (Cbb3-type CcO) for oxygen detoxification and utilization. Moreover, AOB, aerobic/anoxic heterotrophic bacteria, denitrifying bacteria, etc. defined as the core members in anammox consortia could also consume DO and adjust the NH4+-N/NO2−-N ratio for AnAOB, establishing potent microbial interactions to relieve the pressure of DO on AnAOB and improve NRE. This study reveals that anammox consortia can utilize limited DO as a substrate to promote anammox processes, which advances the practical applications of anammox processes.

Effect of culture history and carbon sources on polyhydroxyalkanoates production in activated sludge systems

ABSTRACT Polyhydroxyalkanoates (PHAs) are important and completely biodegradable alternatives to regular plastics, and they can be produced by activated sludge systems during wastewater treatment. Wastewaters with high organic content are being used for PHA production, which is an important resource recovery option. In this context, the effect of sludge retention time and different carbon sources, such as acetate, peptone-mixture and industrial wastewater (containing acetic acid (AA), lactic acid (LA) and propionic acid (PA)), on PHA storage was investigated. Oxygen utilisation rate (OUR) profiles were generated in respirometric tests and were evaluated by activated sludge modelling. Results showed that high storage (AA: 70%; LA: 49%; PA: 60% and industrial wastewater: 52%) was achievable in the feast phase even when the biomass was fed with a high organic acid content substrate to which it is not acclimated.

Correlation between epicardial fat thickness and maximum oxygen utilisation in obese adult males: A cross-sectional study

Correlation between epicardial fat thickness and maximum oxygen utilisation in obese adult males: A cross-sectional study

The functional state of athletes who have undergone coronavirus infection (COVID-19)

This study aimed to investigate the energy supply of athletes, who had a mild form of coronavirus infection (COVID-19) under cycling ergometric load (CEL) to substantiate the timing of recovery, as well as to determine the volume and intensity of physical activity. Eighty-seven athletes aged from 18 to 28 years old, involved in cyclic sports, were examined. Group I consisted of 52 athletes with COVID-19, and group II consisted of 37 healthy self-isolating athletes. In addition to the comprehensive examination, the tested athletes underwent special examinations: the study of diagnostic material using methods of nucleic acid amplification, spirography and spiroergometry, electrocardiography (ECG), and CEL. The results of athletes from both groups did not differ significantly (p ​> ​0.5) in the 1st, 2nd, and 3rd examinations. The second examination revealed a discrepancy between functional reserves and the load performed, as evidenced by the difference in the recovery rate of most indicators, the results of the third examination in the long-term period (6 months) showed that the athletes of the first group did not have any violations of the parameters of the respiratory function (RF) and cardiovascular system at rest, after performing CEL, as well as in the recovery period. The results suggest that the full resumption of training loads and participation in competitions are possible only with the complete normalization of the functional state of the cardiorespiratory system. The most informative indicators are: minute ventilation (V˙E), heart rate (HR), oxygen pulse (OP), and coefficient of oxygen utilization (COU).

Closed-loop oxygen usage during invasive mechanical ventilation of pediatric patients (CLOUDIMPP): a randomized controlled cross-over study.

The aim of this study is the evaluation of a closed-loop oxygen control system in pediatric patients undergoing invasive mechanical ventilation (IMV). Cross-over, multicenter, randomized, single-blind clinical trial. Patients between the ages of 1 month and 18 years who were undergoing IMV therapy for acute hypoxemic respiratory failure (AHRF) were assigned at random to either begin with a 2-hour period of closed-loop oxygen control or manual oxygen titrations. By using closed-loop oxygen control, the patients' SpO2 levels were maintained within a predetermined target range by the automated adjustment of the FiO2. During the manual oxygen titration phase of the trial, healthcare professionals at the bedside made manual changes to the FiO2, while maintaining the same target range for SpO2. Following either period, the patient transitioned to the alternative therapy. The outcomes were the percentage of time spent in predefined SpO2 ranges ±2% (primary), FiO2, total oxygen use, and the number of manual adjustments. The median age of included 33 patients was 17 (13-55.5) months. In contrast to manual oxygen titrations, patients spent a greater proportion of time within a predefined optimal SpO2 range when the closed-loop oxygen controller was enabled (95.7% [IQR 92.1-100%] vs. 65.6% [IQR 41.6-82.5%]), mean difference 33.4% [95%-CI 24.5-42%]; P < 0.001). Median FiO2 was lower (32.1% [IQR 23.9-54.1%] vs. 40.6% [IQR 31.1-62.8%]; P < 0.001) similar to total oxygen use (19.8 L/h [IQR 4.6-64.8] vs. 39.4 L/h [IQR 16.8-79]; P < 0.001); however, median SpO2/FiO2 was higher (329.4 [IQR 180-411.1] vs. 246.7 [IQR 151.1-320.5]; P < 0.001) with closed-loop oxygen control. With closed-loop oxygen control, the median number of manual adjustments reduced (0.0 [IQR 0.0-0.0] vs. 1 [IQR 0.0-2.2]; P < 0.001). Closed-loop oxygen control enhances oxygen therapy in pediatric patients undergoing IMV for AHRF, potentially leading to more efficient utilization of oxygen. This technology also decreases the necessity for manual adjustments, which could reduce the workloads of healthcare providers. This research has been submitted to ClinicalTrials.gov (NCT05714527).

Post-Pulmonary Embolism Phenotypes Described by Invasive Cardiopulmonary Exercise Testing

BackgroundPost pulmonary embolism (PE) dyspnea is common. Existing non-invasive studies have demonstrated that post PE dyspnea is associated with elevations in right ventricular afterload, dead space ventilation, and deconditioning. We aimed to use invasive cardiopulmonary exercise testing (iCPET) parameters in patients with post PE dyspnea to identify unique physiologic phenotypes. Research QuestionAre there distinct post pulmonary embolism dyspnea physiologic phenotypes described with iCPET? Study Design and MethodsPatients were enrolled at the time of acute PE and through our pulmonary hypertension and dyspnea clinic. ICPET was performed if there was high suspicion for pulmonary hypertension or if there was unexplained dyspnea. A hierarchical cluster analysis was performed to identify dyspnea phenotypes. ICPET parameters assessing pulmonary hemodynamics, ventilation, and peripheral oxygen utilization were then compared within and across each cluster and with iCPET controls against peak oxygen consumption (Peak VO2). Results173 patients were enrolled. Sixty-seven patients underwent iCPET. All patients had reductions in Peak VO2 and peak cardiac index relative to controls. Three clusters were identified. Cluster one was defined by having elevated RV afterload and impaired ventilatory efficiency. Cluster two had elevated RV afterload with reductions in respiratory mechanics. Cluster three had mild derangement in RV afterload with mild reductions in peak cardiac output. InterpretationiCPET reveals significant heterogeneity in post PE dyspnea. Three phenotypes are characterized by differences in RV afterload, ventilatory efficiency, respiratory mechanics, and peripheral oxygen utilization.

Young users of electronic cigarettes exhibit reduced cardiorespiratory fitness.

Electronic nicotine delivery systems, often referred to as e-cigarettes, are popular tobacco products frequently advertised as safer alternatives to traditional cigarettes despite preliminary data suggesting a potential negative cardiovascular impact. Cardiorespiratory fitness is a critical cardiovascular health marker that is diminished in individuals who consume traditional tobacco products. Whether the use of e-cigarettes impacts cardiorespiratory fitness is currently unknown. Thus, the purpose of this study was to investigate the impact of regular e-cigarette use on cardiorespiratory fitness in young healthy adults. Twenty-six users of e-cigarettes (ECU, 13 males, and 13 females; age: 24 ± 3 yr; e-cigarette usage 4 ± 2 yr) and 16 demographically matched nonusers (NU, 6 males, and 10 females; age: 23 ± 3 yr) participated in this study. Cardiorespiratory fitness was measured by peak oxygen consumption (V̇o2peak) during a cardiopulmonary exercise test. Measurements of chronotropic response, hemodynamic, oxygen extraction, and utilization were also evaluated. Our results suggest that regular users of e-cigarettes exhibited significantly lower peak oxygen consumption when compared with nonusers, even when controlled by fat-free mass and lean body mass. Hemodynamic changes were not different between both groups during exercise, whereas lower chronotropic responses and skeletal muscle oxygen utilization were observed in users of e-cigarettes. Results from the present study demonstrate that young, apparently healthy, regular users of e-cigarettes exhibit significantly reduced cardiorespiratory fitness, lower chronotropic response, and impaired skeletal muscle oxygen utilization during exercise. Overall, our findings contribute to the growing body of evidence that supports adverse effects of regular e-cigarette use on cardiovascular health.NEW & NOTEWORTHY E-cigarettes are tobacco products frequently used by youth and young adults. Little is known about the long-term health effects of their prolonged use. Results from the present study demonstrate that young, apparently healthy, regular users of e-cigarettes exhibit significantly reduced cardiorespiratory fitness, a marker of cardiovascular health and a predictor of all-cause mortality. We also identified that the young users of e-cigarettes present with lower chronotropic response and impaired skeletal muscle oxygen utilization during exercise.

Effect of Fe2+-activated persulfate combined with biodegradation in removing gasoline BTX from karst groundwater: A box-column experimental study.

In-situ chemical oxidation with persulfate (PS-ISCO) is a preferred approach for the remediation of fuel-contaminated groundwater. Persulfate (PS) can be activated by various methods to produce stronger sulfate radicals for more efficient ISCO. Despite karst aquifers being widespread, there are few reports on PS-ISCO combined with Fe2+-activated PS. To better understand the effects of Fe2+-activated PS for the remediation of gasoline-contaminated aquifers in karst areas, a box-column experiment was conducted under flow conditions, using karst groundwater and limestone particles to simulate an aquifer. Gasoline was used as the source of hydrocarbon contaminants. Dissolved oxygen and nitrate were added to enhance bioremediation (EBR) and ferrous sulfate was used to activate PS. The effect of Fe2+-activated PS combined with biodegradation was compared during the periods of EBR + ISCO and ISCO alone, using the mass flow method for data analysis. The results showed that the initial dissolution of benzene, toluene, and xylene (BTX) from gasoline injection was rapid and variable, with a decaying trend at an average pseudo-first-order degradation rate constant of 0.032 d-1. Enhanced aerobic biodegradation and denitrification played a significant role in limestone-filled environments, with dissolved oxygen and nitrate utilization ratios of 59 ~ 72% and 12-70%, respectively. The efficiency of EBR + ISCO was the best method for BTX removal, compared with EBR or ISCO alone. The pseudo-first-order degradation rate constants of BTX reached 0.022-0.039, 0.034-0.070, and 0.027-0.036 d-1, during the periods of EBR alone, EBR + ISCO, and ISCO alone, respectively. The EBR + ISCO had a higher BTX removal ratio range of 71.0 ~ 84.3% than the ISCO alone with 30.1 ~ 45.1%. The presence of Fe2+-activated PS could increase the degradation rate of BTX with a range of 0.060 ~ 0.070 d-1, otherwise, with a range of 0.034-0.052 d-1. However, Fe2+-activated PS also consumed about 3 times the mass of PS, caused a further decrease in pH with a range of 6.8-7.6, increased 3-4 times the Ca2+ and 1.6-1.8 times the HCO3- levels, and decreased the BTX removal ratio of ISCO + EBR, compared to the case without Fe2+ activation. In addition, the accumulation of ferric hydroxides within a short distance indicated that the range of PS activated by Fe2+ may be limited. Based on this study, it is suggested that the effect of Fe2+-activated PS should be evaluated in the remediation of non-carbonate rock aquifers.

Integrated cellular response of the zebrafish (Danio rerio) heart to temperature change.

A decrease in environmental temperature represents a challenge to the cardiovascular system of ectotherms. To gain insight into the cellular changes that occur during cold exposure and cold acclimation we characterized the cardiac phosphoproteome and proteome of zebrafish following 24 h or one week exposure to 20 oC from 27 oC; or at multiple points during six weeks of acclimation to 20 oC from 27 oC. Our results indicate that cold exposure causes an increase in mitogen-activated protein kinase signaling, the activation of stretch sensitive pathways, cellular remodeling via ubiquitin-dependent pathways, and changes to the phosphorylation state of proteins that regulate myofilament structure and function including desmin and troponin T. Cold acclimation (2-6 weeks) led to a decrease in multiple components of the electron transport chain through time, but an increase in proteins for lipid transport, lipid metabolism, the incorporation of polyunsaturated fatty acids into membranes and protein turnover. For example, there was an increase in the levels of apolipoprotein C, prostaglandin reductase-3, and surfeit locus protein 4, involved in lipid transport, lipid metabolism, and lipid membrane remodeling. Gill opercular movements suggests that oxygen utilization during cold acclimation is reduced. Neither the amount of food consumed relative to body mass nor body condition were affected by acclimation. These results suggest that while oxygen uptake was reduced, energy homeostasis was maintained. This study highlights that the response of zebrafish to a decrease in temperature is dynamic through time and that investment in the proteomic response increases with the duration of exposure.

Identifying the Mechanisms of a Peripherally Limited Exercise Phenotype in Patients With Heart Failure With Preserved Ejection Fraction.

We identified peripherally limited patients using cardiopulmonary exercise testing and measured skeletal muscle oxygen transport and utilization during invasive single leg exercise testing to identify the mechanisms of the peripheral limitation. Forty-five patients with heart failure with preserved ejection fraction (70±7 years, 27 females) completed seated upright cardiopulmonary exercise testing and were defined as having a (1) peripheral limitation to exercise if cardiac output/oxygen consumption (VO2) was elevated (≥6) or 5 to 6 with a stroke volume reserve >50% (n=31) or (2) a central limitation to exercise if cardiac output/VO2 slope was ≤5 or 5 to 6 with stroke volume reserve <50% (n=14). Single leg knee extension exercise was used to quantify peak leg blood flow (Doppler ultrasound), arterial-to-venous oxygen content difference (femoral venous catheter), leg VO2, and muscle oxygen diffusive conductance. In a subset of participants (n=36), phosphocreatine recovery time was measured by magnetic resonance spectroscopy to determine skeletal muscle oxidative capacity. Peak VO2 during cardiopulmonary exercise testing was not different between groups (central: 13.9±5.7 versus peripheral: 12.0±3.1 mL/min per kg; P=0.135); however, the peripheral group had a lower peak arterial-to-venous oxygen content difference (central: 13.5±2.0 versus peripheral: 11.1±1.6 mLO2/dL blood; P<0.001). During single leg knee extension, there was no difference in peak leg VO2 (P=0.306), but the peripherally limited group had greater blood flow/VO2 ratio (P=0.024), lower arterial-to-venous oxygen content difference (central: 12.3±2.5 versus peripheral: 10.3±2.2 mLO2/dL blood; P=0.013), and lower muscle oxygen diffusive conductance (P=0.021). A difference in magnetic resonance spectroscopy-derived phosphocreatine recovery time was not detected (P=0.199). Peripherally limited patients with heart failure with preserved ejection fraction identified by cardiopulmonary exercise testing have impairments in oxygen transport and utilization at the level of the skeletal muscle quantified by invasive knee extension exercise testing, which includes an increased blood flow/V̇O2 ratio and poor muscle diffusive capacity. URL: https://www.clinicaltrials.gov; Unique identifier: NCT04068844.

Nutrient accumulations in high-saline bottom waters in the eutrophic East China Sea inner shelf

Despite decades of mitigation efforts, eutrophication-induced algal blooms and hypoxia have not significantly decreased globally, possibly due to the legacy effects of eutrophication. The legacy effect has been more explored in inland waters and enclosed estuaries than in open coastal waters. Here, we reanalyzed cruise data from the East China Sea inner shelf to explore the effect of eutrophication on nutrient accumulations in high-saline bottom waters. Our dataset showed elevated nitrate (12.75 ± 6.51 μmol L−1) and phosphate (0.85 ± 0.26 μmol L−1) in high-salinity (salinity>34, temperature < 23 °C) bottom waters during the summer of 2006 to 2013. They were higher than those typically observed in the Taiwan Warm Current Bottom Water by approximately 5.45 ± 6.51, and 0.29 ± 0.26 μmol L−1, respectively. Significant correlations of nitrate with apparent oxygen utilization (AOU) and elevated AOU suggested that organic matter decomposition contributed to increased nitrate in bottom waters under eutrophication conditions. Based on an end-member mixing estimation, we found that the organic matter decomposition accounted for 28% to 37% of the nutrient concentrations in the bottom waters, with a standard deviation of 20%. Results from our mass-balance model indicated that 40–74% of regenerated nutrients are flushed out of the model box set within 95% equilibrium time due to the advection of offshore waters, assuming a residence time of 46.0 to 13.9 days. Based on cruise results in June and August 2009, the net accumulation rates of nitrate, phosphate, and AOU in the Taiwan Warm Current Bottom Water were estimated to be 0.046, 0.0036, and 0.44 μmol L−1 d−1, respectively. Such nutrient accumulations in the water column and the residual nutrients in sediment are crucial legacy nutrients, potentially triggering algal blooms. Conversely, the flushing effect suggests a significant transport of nutrients and other chemical elements to the offshore and open ocean.

Longitudinal decline in peak V̇o2 with aging in a healthy population is associated with a reduction in peripheral oxygen utilization but not in cardiac output.

Aging is associated with a significant decline in aerobic capacity assessed by maximal exercise oxygen consumption (V̇o2max). The relative contributions of the specific V̇o2 components driving this decline, namely cardiac output (CO) and arteriovenous oxygen difference (A - V)O2, remain unclear. We examined this issue by analyzing data from 99 community-dwelling participants (baseline age: 21-96 yr old; average follow-up: 12.6 yr old) from the Baltimore Longitudinal Study of Aging, free of clinical cardiovascular disease. V̇o2peak, a surrogate of V̇o2max, was used to assess aerobic capacity during upright cycle ergometry. Peak exercise left ventricular volumes, heart rate, and CO were estimated using repeated gated cardiac blood pool scans. The Fick equation was used to calculate (A - V)O2diff,peak from COpeak and V̇o2peak. In unadjusted models, V̇o2peak, (A - V)O2diff,peak, and COpeak declined longitudinally over time at steady rates with advancing age. In multiple linear regression models adjusting for baseline values and peak workload, however, steeper declines in V̇o2peak and (A - V)O2diff,peak were observed with advanced entry age but not in COpeak. The association between the declines in V̇o2peak and (A - V)O2diff,peak was stronger among those ≥50 yr old compared with their younger counterparts, but the difference between the two age groups did not reach statistical significance. These findings suggest that age-associated impairment of peripheral oxygen utilization during maximal exercise poses a stronger limitation on peak V̇o2 than that of CO. Future studies examining interventions targeting the structure and function of peripheral muscles and their vasculature to mitigate age-associated declines in (A - V)O2diff are warranted.NEW & NOTEWORTHY The age-associated decline in aerobic exercise performance over an average of 13 yr in community-dwelling healthy individuals is more closely associated with decreased peripheral oxygen utilization rather than decreased cardiac output. This association was more evident in older than younger individuals. These findings suggest that future studies with larger samples examine whether these associations vary across the age range and whether the decline in cardiac output plays a greater role earlier in life. In addition, studies focused on determinants of peripheral oxygen uptake by exercising muscle may guide the selection of preventive strategies designed to maintain physical fitness with advancing age.

Pediatric COVID-19 in Lesotho and Post-pandemic Implications on Lower Respiratory Infections in Children.

Background The United States Agency for International Development (USAID) Reaching Impact, Saturation, and Epidemic Control (RISE) program funded Jhpiego to support the Government of Lesotho's COVID-19 response, including two national COVID-19 treatment centers. To evaluate the status of post-pandemic pediatric respiratory care in Lesotho, we analyzed pediatric treatment center data and healthcare worker (HCW) performance on pediatric COVID-19 training offered to HCWs at COVID-19 treatment centers. Methods We conducted a retrospective cohort study of patients 15 years of age or less hospitalized at two COVID-19 treatment centers in Lesotho from May 1, 2020, to April 30, 2022. Patient data were extracted from hospital files. We used the independent sample t-test, Mann-Whitney U test, or Fisher's exact test to evaluate associations between exposure variables and death. We also assessed differences between pre- and post-training examination scores of three one-day HCW training on pediatric COVID-19 using paired t-tests. Results Overall, <15-year-olds comprised 18/1,448 (1.2%) hospitalizations. Twenty-two percent (4/18) of children were hypoxemic (oxyhemoglobin saturation <94%) within the first 24 hours and 44% (8/18) at any point in the hospitalization. Oxygen utilization increased over the two-year period (p=0.004) and all eight children with hypoxemia received oxygen (p<0.001). Four of 18 (22%) patients died. For HCW training, pre- and post-training examinations were completed by 76/82 (92.7%) participants. The overall mean pretraining score was 44.6% (standard deviation (SD) 15.7%). Mean scores improved by an average of 32.2% (95% confidence interval (CI) 27.7%, 36.6%, p<0.001) on the same day post-training examination. Conclusions National COVID-19 treatment center data indicate a low burden of severe pediatric COVID-19 disease in Lesotho. However, recognized HCW knowledge gaps suggest deficiencies in identifying and referring severely ill children, which may detrimentally impact the ongoing post-pandemic care of children with severe lower respiratory infections.

Controls on Oxygen Variability and Depletion in the Patuxent River Estuary

Oxygen depletion in coastal waters is increasing globally due primarily to eutrophication and warming. Hypoxia responses to nutrient loading and climate change have been extensively studied in large systems like the Chesapeake Bay and the Baltic Sea, while fewer studies have investigated smaller, shallower hypoxic zones. Thus, an improved understanding of the interactions of eutrophication and warming on hypoxia expansion (or reduction) in the wide variety of different estuarine environments is needed. We examined interannual controls on oxygen depletion in the Patuxent River estuary, a eutrophic sub-estuary of Chesapeake Bay where seasonal hypoxia develops annually. We conducted a spatial and temporal analysis of dissolved oxygen (DO) trends, timing, and several metrics of depletion over a long-term record (1985–2021). We found an internally generated hypoxic zone that initiates in the middle estuary, spreading upstream and downstream as the summer progresses, and that hypoxic volume days (HVD) have been increasing (0.11 per year, p = 0.03) over the record despite reduced watershed nitrogen loads and stable phosphorus loads. River flow and temperature have been increasing and are major drivers of increased HVD, with river flow explaining 40% of the interannual variation in HVD (temperature has increased 0.03 and 0.06 °C per year in summer and fall, respectively). Apparent oxygen utilization (AOU) is increasing in bottom waters in the fall, consistent with increasing trends of both water temperature and stratification strength. HVD was negatively related (r2 = 0.34, slope = −0.59*HVD) to the biomass of benthic invertebrates in the middle region of the estuary, suggesting that benthic forage for higher trophic levels will be limited by sustained hypoxia. These results indicate that current and future climate variability plays an important role in regulating oxygen depletion in the Patuxent River estuary, which reinforces the need to factor climate change into strategies for the restoration and management of estuaries.

Iron Deficiency in Pulmonary Hypertension.

Pulmonary hypertension (PH) is a complex cardiovascular condition that is characterized by elevated pulmonary arterial pressure, which leads to significant morbidity and mortality. Among the various factors that influence the pathophysiology and progression of PH, iron deficiency has become a critical, yet often overlooked, element. In this review, the prevalence, implications, and therapeutic potential of addressing iron deficiency in patients with PH are elucidated.Iron deficiency, which is prevalent in a significant proportion of patients with PH, has been associated with worsened clinical outcomes, including diminished exercise capacity, impaired oxygen transport and utilization, and compromised right ventricular function. The pathophysiological linkages between iron deficiency and PH are multifaceted and involve alterations in oxygen sensing, endothelial function, and metabolic disturbances.In this review, the evidence from recent clinical trials and studies that assess the impact of iron supplementation, both oral and intravenous, on PH outcomes is critically analyzed. Although some studies suggest improvements in exercise capacity and hemodynamic parameters following iron repletion, the responses appear variable and are not universally beneficial. This review highlights the complexities of iron metabolism in PH and the challenges in effectively diagnosing and treating iron deficiency in this patient population.Furthermore, the potential mechanisms through which iron supplementation might influence pulmonary vascular and right ventricular function, emphasizing the need for personalized treatment approaches are discussed. In this review, the importance of recognizing iron deficiency in the management of patients with PH is highlighted, and further research is warranted to establish comprehensive, evidence-based guidelines for iron supplementation in this unique patient cohort. The ultimate goal of this review is to improve clinical outcomes and quality of life for patients suffering from this debilitating condition.

Hypoxia Triggered by Expanding River Plume on the East China Sea Inner Shelf During Flood Years

AbstractThe frequency of riverine floods is predicted to increase in East Asia. However, the response of coastal hypoxia (&lt;63 μmol L−1) to floods has not been well understood. In the summer of 2020, characterized by one of the most significant Changjiang water fluxes in three decades, we conducted a cruise during the flood period on the East China Sea inner shelf. Our observations revealed severe bottom hypoxia with a maximum spatial coverage of ∼11,600 km2 and a minimum dissolved oxygen concentration (DO) of 21 μmol L−1. In the surface layer, the relationships between salinity and nitrate, dissolved inorganic carbon (DIC) indicated significant organic matter production, validated by a high‐Chlorophyll‐a (Chl a) patch (&gt;5 μg L−1). Furthermore, the significant relationship between apparent oxygen utilization and DIC of deep waters reveals that the organic matter decomposition primarily drove the hypoxia during the flood period. Episodic wind events also influenced bottom DO and DIC, by transporting surface waters to the deep. Multiple‐years data set shows that the average Changjiang nitrate flux during flood years is about 1.4 times that during non‐flood years. The flood waters mix with estuarine waters, forming the high‐nutrient plume waters, which expanded farther offshore during the flood period. While high turbidity remained confined to the inner estuary. Consequently, the high‐Chl a area significantly expanded, which significantly exacerbated the hypoxia.

Integrated Solar Production of Fertilisers and Fuels

Solar fertiliser production including the internal utilisation of the side-product oxygen is analysed as one promising example of an innovative process utilising renewable energy resources and addressing the aspect of integrated production – here in the case of nitrogen containing fertilisers. Alternative methods to supply solar energy into the energy intensive generation of precursors needed for nitrate-based fertiliser via the Haber Bosch and Ostwald processes are introduced. Those methods are assessed in a comparative way through process design and simulation with a focus on oxygen injection inside the NOx combustion of the Ostwald process and through calculation of its economic impacts.