Oxygen, Volume 5, Issue 4 (December 2025) – 8 articles

Background: During an apnea, oxygen depletion occurs at all tissue levels, so apnea duration is influenced by the mammalian dive reflex, which includes a bradycardia resulting in reduced cardiac oxygen consumption. This study aimed to examine the relationships between heart rate (HR), peripheral estimation of O₂ (SpO₂), deltoid and respiratory muscle oxygenation (SmO₂), and apnea duration. Methods: The study included 10 breath-hold divers (BHD), 39 ± 10 years of age, with body height of 184.3 ± 3.5 cm, body mass of 84.0 ± 9.2 kg, and 16.2 ± 9.7 years of apnea experience. The BHD performed three preparatory apneas followed by three maximal apneas with 5 min of supine rest between each apnea. During all apneas (duration, 115–323 s; involuntary breathing movements (IBMs), 7–35), SmO₂ (measured via NIRS on intercostals (respiratory) and deltoid (locomotor) muscles), heart rate, and SpO₂ (measured via forehead sensor) were obtained. Results: The smallest disagreement in oxygen levels was between intercostal SmO₂ and SpO₂ during the easy-going phase (no IBMs), whereas deltoid desaturation values were more variable. During the struggle phase, Intercostal SmO₂, moderately, and Deltoid SmO₂, strongly, differed from SpO₂. Correlations between apnea duration and O₂ saturation showed that only Intercostal SmO₂ (r = −0.71; p = 0.03) was significantly related to apnea duration. There was also a significant correlation between HR and SpO₂ in the struggle phase (r = −0.58; p = 0.05). Conclusions: These findings suggest that during the struggle phase, SpO₂ and SmO₂ are not highly connected and that local and systemic oxygen levels in the blood are depleted at different rates. Furthermore, the HR response during the struggle phase affected only SpO₂, which indicates that lowering the heart rate may help prevent more rapid deoxygenation. Lastly, the intercostal trend of deoxygenation could be interpreted as respiratory muscle work, suggesting that the increased work of respiratory muscles may prolong apnea duration. Full article

The purpose of this analysis is to report on the clinical efficacy of Continuous Diffusion of Oxygen (CDO) therapy in real-world clinical practice and compare those results to data published in controlled clinical studies. For the real-world clinical results, a Prospective Patients Database (PPD) of 764 patients treated using CDO therapy in a broad range of clinical practices across a wide range of wound types and wound locations was analyzed. The objectives included analyzing the clinical efficacy of CDO therapy across multiple wound types and anatomical locations, testing the data for robustness, and comparing the efficacy to results from controlled clinical studies for CDO and NPWT. The PPD data is also analyzed for efficacy among the sexes and by age for older patients in the Medicare population. The robustness of the PPD data is tested using various non- and semi-parametric statistical tools, including the Kaplan–Meier and Cox proportional hazard (PH) models, among others. The results show that CDO therapy is highly efficacious with an average healing success rate of 76.3% in real-world application, ranging from 71.2% to 84.1% for different wound types. The Medicare age population had an average age of 78 years old and similar healing rates to the overall population, with slightly better results for pressure ulcers in the older patient population. The PPD data proved to be extremely robust in every test method, demonstrating substantially equivalent efficacy in various wound types and locations, as well as between men and women. The PPD results for CDO compared favorably to clinical trial results for CDO and NPWT. Both clinical trial and PPD data for CDO exhibited better healing rates when compared to NPWT. Kaplan–Meier analysis shows that CDO use in clinical practice has 79.2% full closure in 112 days, as compared to NPWT, which has 43.2% full closure in the same timeframe for similar wound sizes and severity. These results demonstrate not only that CDO is highly efficacious in clinical practice, but that the efficacy is also similar across all wound types and locations in the body. CDO also compares very favorably to NPWT. Full article

Maximal aerobic power (V̇O₂peak) in youth depends on hemoglobin (Hb)—mediated oxygen transport. While sex- and age-specific patterns are established in untrained cohorts, further research is needed in competitive adolescent athletes. We studied 124 young athletes matched by age and sex (62 boys, 62 girls; 10–16 years). Hb was measured from fasting blood samples, and V̇O₂peak was determined via cardiopulmonary exercise testing (CPET). Boys showed higher Hb than girls (14.43 ± 0.85 g/dL vs. 13.6 ± 0.74 g/dL; p < 0.001) and a significant age-related increase (B = 0.29, p < 0.001), whereas girls remained stable. V̇O₂peak was also higher in boys (50.03 ± 6.18 mL/min/kg, p < 0.001). Regression analysis identified Hb as a strong predictor of V̇O₂peak (β = 0.40, p < 0.001). These findings demonstrate that classical developmental Hb trajectories persist in highly trained youth and confirm Hb as a key determinant of aerobic power. Monitoring hematological status, particularly in female athletes, is essential for optimizing performance and development. Full article

Root pruning has been proposed as a practical method to regulate growth and metabolite accumulation in horticultural crops, yet its physiological and metabolic consequences in hydroponically grown lettuce remain poorly understood. In this study, we examined the effects of root pruning, applied two days before harvest, on biomass production, oxidative stress responses, and metabolite accumulation in red leaf lettuce. Root pruning suppressed root growth and reduced root water content in a severity-dependent manner. Shoot fresh weight also declined, whereas shoot dry weight was significantly reduced only under severe pruning. Young leaves of pruned plants exhibited transient reddish coloration, which was most pronounced under severe pruning. Quantitative analyses revealed that anthocyanin content increased up to 4.5-fold compared with the control, while total phenolic content also rose significantly. These metabolic changes were accompanied by pronounced oxidative stress, as indicated by elevated hydrogen peroxide accumulation and enhanced lipid peroxidation. In addition, leaf nitrate concentration decreased significantly in both moderate and severe pruning treatments. Collectively, these findings demonstrate that root pruning acts as a controllable stressor that triggers oxidative stress signaling, enhances antioxidant metabolite accumulation, and reduces nitrate content, highlighting its potential as a pre-harvest strategy for improving the nutritional and functional quality of hydroponic lettuce. Full article

This review indicates that microalgae may serve as a sustainable supply of bioactive compounds and lipids over the long run. It also discusses the significance of lactic acid bacteria (LAB) and Saccharomyces cerevisiae in biotransformation processes. Microalgae contribute to food security and environmental sustainability due to their rapid growth and diverse applications, including food, feed, and biofuels. Fermentation with LAB and S. cerevisiae enhances the nutritional and functional properties of microalgal biomass, rendering it more digestible, bioactive, and palatable. This review discusses the metabolic characteristics of LAB and S. cerevisiae, their ability to modify microalgal components through enzymatic action, and the resultant products, including enhanced fatty acid profiles and bioactive compounds. Furthermore, the biotransformation of pigments during LAB fermentation is examined, revealing significant alterations in the hue and bioactivity of the pigments, hence enhancing the appeal of microalgal products. Future perspectives emphasize the necessity for further investigation to identify optimal fermentation conditions and to explore the synergistic interactions between LAB and S. cerevisiae in the production of novel beneficial components from microalgae using both microbes. Full article

Photosensitized excitation of molecular oxygen generates singlet oxygen, a reactive oxygen species that has been studied in biological systems, synthetic methods and in aquatic ecosystems. The reaction of singlet oxygen with tertiary amines is important because they are widely used as electron donors in photochemical reactions. Herein we studied the reaction of singlet oxygen with multiple tertiary amines including ethylenediamine tetraacetic acid (EDTA), triethanolamine (TEOA) and triethylamine (TEA). Singlet oxygen was generated using the photosensitizers methylene blue or chlorin e6 and red light with output at 660 nm. TEOA and TEA generated more hydrogen peroxide (H₂O₂), the stable end product, than EDTA at all pH values tested and regardless of the photosensitizer used. Both histidine and imidazole scavenged singlet oxygen and decreased H₂O₂ yield. The extent of histidine scavenging was pH-dependent for the combination of methylene blue and EDTA but not for TEOA or TEA. The combination of chlorin e6 and EDTA generated less H₂O₂ because both contain multiple negative charges that limit their interaction. Multiple tertiary amines that are used as biochemical buffers produced similar quantities of H₂O₂ as EDTA, TEOA and TEA. However, these sulfonic acid-containing tertiary amines did not function as electron donors in a benzoquinone photoreduction assay. Full article

Swine effluents require effective treatment due to their high pollutant load, particularly nitrogen and phosphorus, which can cause eutrophication of water bodies. This study focused on monitoring nutrient removal in a sequential biological reactor through online measurements of parameters such as dissolved oxygen (DO), pH, oxidation-reduction potential (ORP), and total alkalinity during the treatment of effluents from a pig slaughterhouse. A laboratory-scale reactor was used, operated with timer switches in an anaerobic–aerobic–anoxic sequence, a sludge retention time (SRT) of 25 days, and an operational cycle time of 16 h. The reactor demonstrated notable efficiency in contaminant removal, with an average organic matter removal of 87.1% measured as chemical oxygen demand (COD) and 95.5% as biochemical oxygen demand (BOD). Regarding nitrogen and phosphorus removal, a 69.4% reduction in total nitrogen (TN) and a 53.2% reduction in total phosphorus (TP) were observed. The pH, ORP, and DO profiles showed a clear correlation with the nutrient removal processes, allowing optimization of the phase durations in the reactor to enhance treatment efficiency. Full article

Chronic kidney disease is closely associated with an increased risk of cardiovascular disease. Although kidney transplantation represents the treatment of choice for patients with end-stage chronic kidney disease, it is also linked to significant cardiovascular risk. This study aimed to evaluate the relationship between cardiovascular pathology and oxidative status in kidney transplant recipients, while also assessing the influence of disease etiology and humoral immune response on oxidative imbalance. A cross-sectional analysis was conducted in individuals with advanced chronic kidney disease (n = 36) and kidney transplant recipients (n = 40). A total of 18 healthy subjects were included. The enzymatic activities of xanthine oxidase, superoxide dismutase, and glutathione peroxidase, and levels of lipid peroxidation products, oxidized glutathione, and reduced glutathione were measured using spectrophotometry in plasma and mononuclear and polymorphonuclear leukocytes isolated using Ficoll density gradients. Individual oxidative status was evaluated using OXYSCORE. Kidney transplantation was associated with a higher incidence of cardiovascular disease (p < 0.01) and increased levels of both prooxidant (p < 0.01) and antioxidant parameters (p < 0.01). Elevated OXYSCORE values were observed particularly in patients with nephroangiosclerosis, diabetic kidney disease, polycystic kidney disease (p < 0.05), and cardiovascular comorbidities (p < 0.001). Additionally, the presence of anti-graft antibodies correlated with higher oxidative scores. These findings suggest that OXYSCORE may serve as a potential indicator of cardiovascular damage in kidney transplant recipients. Full article