Oxygen, Volume 6, Issue 3 (September 2026) – 9 articles

Neonates born at higher altitudes may be at increased risk for adverse outcomes due to lower ambient oxygen availability. Despite frequent use of home oxygen therapy following neonatal intensive care unit (NICU) discharge, evidence-based guidelines assessing discharge readiness and oxygen prescribing in high-altitude settings remains limited. This study aimed to identify factors associated with adverse events following discharge and characterize infants discharged with home oxygen therapy in New Mexico. A retrospective chart review was conducted of infants discharged with home oxygen therapy from the University of New Mexico Hospital (UNMH) NICU from 1 July 2018 through 1 July 2023. We found that lower room air trial oxygen saturation and lower birth weight were both significantly associated with adverse events after discharge. These findings informed implementation institutional discharge protocols that indicated minimum room air saturation thresholds prior to discharge and oxygen adjustments for higher altitude. Although implementation of these protocols was not associated with a statistically significant reduction in adverse events, this work established a foundation for future multicenter collaboration with other centers at high altitude to validate these findings and further refine evidence-based discharge practices for infants living at high altitude. Full article

Arguably, the most vital function of the cardiovascular system (CVS) is its ability to facilitate the oxygenation of blood in the lungs, and to deliver that oxygen to the rest of the body. This relies on the ability of oxygen to diffuse in and out of the bloodstream, as well as for the CVS to maintain adequate perfusion of body tissues. The CVS also plays a key role in immune responses, particularly in initiating an acute inflammatory reaction in response to infection or injury. Changes in vascular function, such as vasodilation, increased vascular permeability, and initiation of coagulation, are critical elements of this inflammatory response. Normally, the regulated nature of immune responses helps to limit any potential detrimental effects. However, in cases of severe, dysregulated inflammation, as seen in conditions such as sepsis, the vascular responses that form a normal part of the inflammatory reaction may start to impact upon tissue oxygenation. Increased microvascular permeability and the development of edema can impact upon oxygen diffusion, whilst tissue perfusion can be impacted at the level of both the micro- and macrocirculation. In severe cases, impaired perfusion and oxygen delivery to vital organs may lead to multiple organ system failure. An increased understanding of the impact of inflammation on vascular function may help elucidate novel therapeutic approaches to manage these critical care situations. Full article

Singlet oxygen is produced by light-dependent excitation of molecular oxygen using photosensitizers. Using blue light and riboflavin (RF) or riboflavin phosphate (RFP) as photosensitizers, we studied the reaction of singlet oxygen with tertiary amines in aqueous solution because many are used as biochemical buffers and as electron donors in photoreduction reactions. The reactions of singlet oxygen with multiple tertiary amines, including ethylenediamine tetraacetic acid (EDTA), bicine, and triethanolamine (TEOA), produced micromolar hydrogen peroxide (H₂O₂) as the stable end product. For bicine and TEOA, but not EDTA, H₂O₂ yield increased as pH increased due to their higher amine pKa values. A white LED used in conjunction with riboflavin and tertiary amines also produced H₂O₂, a contaminant likely to form during tissue culture manipulations. Direct photoreduction of 2,6-dichlorophenolindophenol and 2,3-dimethoxy-5-methyl-p-benzoquinone was achieved using blue light, RF or RFP, and tertiary amines as electron donors. With RF, EDTA was the optimal electron donor for both substrates, whereas with RFP, bicine and TEOA were superior to EDTA. Photochemical redox cycling of both quinones produced H₂O₂ via singlet oxygen-dependent re-oxidation of reduced quinols. Several amine buffers, including HEPES and PIPES, reacted with singlet oxygen to produce H₂O₂ but did not function as electron donors in quinone photoreduction assays. Full article

We studied the Stokes signals generated following the Raman photoexcitation of dissolved oxygen in water. When a water sample is pumped with intense nanosecond radiation, Stokes signals of different origins are generated. These signals form a characteristic nonlinear diffraction pattern, comprising a central spot and concentric rings whose radii depend on the Stokes wavelengths. Although most of the Stokes signals correspond to the stretching vibrations of water molecules, we also observed a small contribution from dissolved oxygen molecules. This contribution can be separated from the others using appropriate spectroscopic filters, then analyzed with a spectrometer. In this study, we report on Stokes components assigned to singlet oxygen excitation detected in the central spot, as well as in the diffraction pattern’s ring structure. The signal detected in the central spot exhibits a single peak, while that from the ring shows a two-peak structure. These two observed peaks are interpreted as Stokes signals corresponding to Raman transitions to the two lowest vibrational sublevels of the singlet-oxygen electronic state. We also report exponential growth in the Stokes signal with the pulse energy, in agreement with the standard stimulated Raman theoretical model. Full article

Introduction: Survival at high altitudes requires efficient energy management. Although hypobaric hypoxia alters thermodynamic efficiency, the independent impact of altitude versus demographic factors on basal and exertional caloric costs remains uncertain. We evaluated these variables in chronic residents across four Peruvian altitudes. Methodology: A cross-sectional study was conducted involving 141 healthy adults (aged 18–38 years) residing in Lima (154 m), Arequipa (2335 m), Puno (3827 m), and La Rinconada (5100 m). Resting energy expenditure (REE) and physical activity energy expenditure (PAEE) were estimated using continuous photoplethysmography; PAEE was assessed following the 6-min walk test (6MWT). Hemodynamic parameters, oxygen saturation (SpO₂), and hemoglobin (Hb) levels were evaluated. An analysis of covariance (ANCOVA) was employed to adjust metabolic variations for age, sex, and body mass index (BMI). Results: Unadjusted data demonstrated a progressive increase in REE and PAEE proportional to altitude. However, the ANCOVA revealed that the independent effect of the city of residence was no longer statistically significant after adjusting for anthropometric and demographic covariates. Physiologically, the SpO₂ deficit imposed a high metabolic demand (an increase of approximately 1.29 kcal in REE for every 1% drop in SpO₂). Hb concentrations above 18 g/dL were associated with an exponential increase in caloric cost driven by blood hyperviscosity. A positive correlation was identified between Hb levels and energy expenditure (EE), which proved to be statistically stronger in the female cohort. Under extreme hypoxia conditions (5100 m), men exhibited a significantly higher PAEE (50.60 ± 10.17 kcal vs. 40.78 ± 5.21 kcal). Despite the increased biological effort, mechanical performance in the 6MWT remained constant across cities. Conclusions: There is no independent relationship between REE and the altitude of residence. The initial unadjusted relationship between altitude and EE was negated by covariates, particularly body mass index (BMI). The preservation of functional capacity at the expense of the energy economy underscores the profound physiological burden of Andean acclimatization. Full article

Medical ozone has emerged as a potential redox-modulating intervention in inflammatory and degenerative conditions, particularly in dermatological contexts characterized by chronic oxidative imbalance and impaired tissue remodeling. Unlike conventional pharmacological agents, ozone exerts its biological activity through rapid chemical reactions generating transient reactive and electrophilic species that activate endogenous adaptive signaling pathways. Controlled oxidative perturbations activate antioxidant transcriptional programs, primarily mediated by the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway, while modulating inflammatory signaling networks, including nuclear factor kappa B (NF-κB) and the NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome. This dual behavior reflects hormetic responses in which low-dose exposure promotes adaptive cellular signaling, whereas excessive oxidative burden leads to structural and functional damage. This review summarizes current knowledge on the molecular mechanisms underlying ozone-induced redox modulation, with emphasis on chemical reactivity, spatiotemporal signaling dynamics, thiol-based sensing, and metabolic reinforcement of antioxidant defenses. Particular attention is given to skin and subcutaneous adipose tissue, where oxidative stress, immune activation, and extracellular matrix remodeling converge. Dose dependency, safety constraints, and methodological variability are critically discussed, highlighting the narrow threshold between adaptive signaling and oxidative injury and the need for rigorous mechanistic and clinical validation. Full article

Introduction: A major health issue in individuals living at high-altitude regions is an increase in the number of red blood cells (RBCs). This condition generates a series of physiological alterations including the nervous system, where damage can occur due to increased blood viscosity. This increased viscosity, in turn, could compromise oxygen uptake, potentially linked to a degree of cognitive impairment. Objective: To determine the association between exposure to chronic hypoxia and sleep quality with the degree of cognitive impairment in a young adult population residing at different altitude levels. Methodology: A cross-sectional study was conducted with 200 apparently healthy subjects (aged 21–26 years) permanently residing in four Peruvian cities: Lima (154 m), Arequipa (2335 m), Puno (3820 m), and La Rinconada (5100 m) (n = 50 per location). Physiological profiles (SpO₂, blood pressure, heart rate, hemoglobin, and hematocrit) were measured. Cognitive impairment and sleep quality were evaluated using the Montreal Cognitive Assessment (MoCA) and the Pittsburgh Sleep Quality Index (PSQI). Sex-stratified hierarchical multiple linear regression models with bootstrapping were utilized for independent correlation analysis. Results: Hemoglobin levels gradually increased with altitude, peaking at 19.47 ± 3.01 g/dL in La Rinconada, while SpO₂ decreased to 81.64%. Moderate-to-severe cognitive impairment was exclusively restricted to the extreme altitude population of La Rinconada, where only 10% of subjects remained unaffected. In the sex-stratified multivariate regression, residency in La Rinconada initially served as a robust negative predictor of MoCA scores among women (β = −5.52, p < 0.001); however, this geographical effect lost statistical significance after adjusting for biological variables in Model 2 (β = −4.72, p = 0.178). In the fully adjusted models, neither individual hemoglobin levels nor SpO₂ fluctuations displayed an independent linear association with cognitive performance in either sex (p > 0.05). Sleep quality was poor across cohorts but showed no significant association with cognitive impairment (p = 0.174). Conclusions: Chronic exposure to severe hypoxia (>5000 m) is associated with a greater presence of cognitive impairment, which is largely accounted for by individual physiological adaptations rather than isolated, linear effects of independent hematological or subjective sleep parameters. Full article

Hydroperoxides (R–OOH, organic hydroperoxides) constitute a relatively small but structurally diverse class of natural metabolites occurring in higher plants, fungi, and marine organisms. Their formation is closely associated with oxidative processes involving redox-active metal ions, particularly iron and copper, which promote reactive oxygen species (ROS) generation and the oxidative transformation of steroids and triterpenoids. In the present study, approximately 1500 naturally occurring steroids and triterpenoids were screened using the PASS (Prediction of Activity Spectra for Substances) platform to identify compounds with potential relevance to neurodegenerative disorders. Among the analyzed compounds, only 17 hydroperoxide-containing steroids and triterpenoids exhibited notable predicted anti-dementia activity and were selected for detailed evaluation. The selected compounds displayed a broad spectrum of predicted biological activities, including antineoplastic, anti-inflammatory, antiulcerative, antithrombotic, hepatoprotective, and neuroprotective effects. Several hydroperoxide-containing triterpenoids demonstrated particularly high predicted anti-dementia activity, with a norlupane-type hydroperoxide exhibiting the highest probability of activity (Pa = 0.972). The biological significance of these compounds may be related to the unique redox properties of the hydroperoxide functionality, which can participate in both oxidative and adaptive signaling processes. Because hydroperoxides interact with transition metal ions and reactive oxygen species, they occupy a complex position at the interface between oxidative stress, cellular defense mechanisms, and neurodegeneration. The present analysis highlights hydroperoxide-containing steroids and triterpenoids as an underexplored class of natural products with potential relevance to dementia research. However, the reported activities are based primarily on computational predictions and should be interpreted as indicators of pharmacological potential rather than experimentally validated therapeutic effects. Further investigations involving blood–brain barrier permeability assessment, biochemical studies, cellular assays, animal models, and clinical evaluation will be required to determine the true therapeutic value of these compounds in neurodegenerative diseases. Full article