Oxygenation through oral Ox66 in a two-hit rodent model of respiratory distress

Acute respiratory distress syndrome (ARDS) is a complication of pulmonary disease that produces life-threatening hypoxaemia. Despite ventilation and hyperoxic therapies, undetected hypoxia can manifest in capillary beds leading to multi-organ failure. Ox66™ is an ingestible, solid-state form of oxygen designed to supplement oxygen deficits. Twenty-four anaesthetized rats underwent a two-hit model of respiratory distress (ARDS), where a single dose (5 mg/kg) of lipopolysaccharide (LPS) was given intratracheally, and then the respiratory tidal volume was reduced by 40%. After 60 min, animals were randomized to receive Ox66™, or normal saline (NS; vehicle control) via gavage or supplemental inspired oxygen (40% FiO2). A second gavage was administered at 120 min. Cardiovascular function and blood oximetry/chemistry were measured alongside the peripheral spinotrapezius muscle's interstitial oxygenation (PISFO2). ARDS reduced mean arterial pressure (MAP) and PISFO2 compared to baseline (BL) for all treatment groups. Treatment with Ox66 or NS did not improve MAP, but 40% FiO2 caused a rapid return to BL. PISFO2 improved after treatment with Ox66™ and 40% FiO2 and remained elevated for both groups against NS until study conclusion. Both oxygen treatments also suppressed the inflammatory response to LPS, suggesting that Ox66™ can deliver therapeutically-impactful levels of oxygen in situations of pulmonary dysfunction.

Effect of inhaled oxygen level on dynamic glucose-enhanced MRI in mouse brain

PURPOSE

To investigate the effect of inhaled oxygen level on dynamic glucose enhanced (DGE) MRI in mouse brain tissue and CSF at 3 T.

METHODS

DGE data of brain tissue and CSF from mice under normoxia or hyperoxia were acquired in independent and interleaved experiments using on-resonance variable delay multi-pulse (onVDMP) MRI. A bolus of 0.15 mL filtered 50% D-glucose was injected through the tail vein over 1 min during DGE acquisition. MRS was acquired before and after DGE experiments to confirm the presence of D-glucose.

RESULTS

A significantly higher DGE effect under normoxia than under hyperoxia was observed in brain tissue (p = 0.0001 and p = 0.0002 for independent and interleaved experiments, respectively), but not in CSF (p > 0.3). This difference is attributed to the increased baseline MR tissue signal under hyperoxia induced by a shortened T1 and an increased BOLD effect. When switching from hyperoxia to normoxia without glucose injection, a signal change of ˜3.0% was found in brain tissue and a signal change of ˜1.5% was found in CSF.

CONCLUSIONS

DGE signal was significantly lower under hyperoxia than that under normoxia in brain tissue, but not in CSF. The reason is that DGE effect size of brain tissue is affected by the baseline signal, which could be influenced by T1 change and BOLD effect. Therefore, DGE experiments in which the oxygenation level is changed from baseline need to be interpreted carefully.

Impact of Positive End-Expiratory Pressure and FiO2 on Lung Mechanics and Intrapulmonary Shunt in Mechanically Ventilated Patients with ARDS Due to COVID-19 Pneumonia

Purpose: This study aimed to investigate the effects of inspired oxygen fraction (FiO2) and positive end-expiratory pressure (PEEP) on gas exchange in mechanically ventilated patients with COVID-19. Methods: Two FiO2 (100%, 40%) were tested at 3 decreasing levels of PEEP (15, 10, and 5 cmH2O). At each FiO2 and PEEP, gas exchange, respiratory mechanics, hemodynamics, and the distribution of ventilation and perfusion were assessed with electrical impedance tomography. The impact of FiO2 on the intrapulmonary shunt (delta shunt) was analyzed as the difference between the calculated shunt at FiO2 100% (shunt) and venous admixture at FiO2 40% (venous admixture). Results: Fourteen patients were studied. Decreasing PEEP from 15 to 10 cmH2O did not change shunt (24 [21-28] vs 27 [24-29]%) or venous admixture (18 [15-26] vs 23 [18-34]%) while partial pressure of arterial oxygen (FiO2 100%) was higher at PEEP 15 (262 [198-338] vs 256 [147-315] mmHg; P < .05). Instead when PEEP was decreased from 10 to 5 cmH2O, shunt increased to 36 [30-39]% (P < .05) and venous admixture increased to 33 [30-43]% (P < .05) and partial pressure of arterial oxygen (100%) decreased to 109 [76-177] mmHg (P < .05). At PEEP 15, administration of 100% FiO2 resulted in a shunt greater than venous admixture at 40% FiO2, ((24 [21-28] vs 18 [15-26]%, P = .005), delta shunt 5.5% (2.3-8.8)). Compared to PEEP 10, PEEP of 5 and 15 cmH2O resulted in decreased global and pixel-level compliance. Cardiac output at FiO2 100% resulted higher at PEEP 5 (5.4 [4.4-6.5]) compared to PEEP 10 (4.8 [4.1-5.5], P < .05) and PEEP 15 cmH2O (4.7 [4.5-5.4], P < .05). Conclusion: In this study, PEEP of 15 cmH2O, despite resulting in the highest oxygenation, was associated with overdistension. PEEP of 5 cmH2O was associated with increased shunt and alveolar collapse. Administration of 100% FiO2 was associated with an increase in intrapulmonary shunt in the setting of high PEEP. Trial registration: NCT05132933.

Precise Regulation in Chain-Edge Structural Microenvironments of 1D Covalent Organic Frameworks for Photocatalysis

Covalent organic frameworks (COFs) constitute a promising research topic for photocatalytic reactions, but the rules and conformational relationships of 1D COFs are poorly defined. Herein, the chain edge structure is designed by precise modulation at the atomic level, and the 1D COFs bonded by C, O, and S elements is directionally prepared for oxygen-tolerant photoinduced electron transfer-atom transfer radical polymerization (PET-ATRP) reactions. It is demonstrated that heteroatom-type chain edge structures (─O─, ─S─) lead to a decrease in intra-plane conjugation, which restricts the effective transport of photogenerated electrons along the direction of the 1D strip. In contrast, the all-carbon type chain edge structure (─C─) with higher intra-plane conjugation not only reduces the energy loss of photoexcited electrons but also enhances the carrier density, which exhibits the optimal photopolymerization performance. This work offers valuable guidance in the exploitation of 1D COFs for high photocatalytic performance. This work offers valuable guidance in the exploitation of 1D COFs for high photocatalytic performance.

HIF1α-dependent uncoupling of glycolysis suppresses tumor cell proliferation

Hypoxia-inducible factor-1α (HIF1α) attenuates mitochondrial activity while promoting glycolysis. However, lower glycolysis is compromised in human clear cell renal cell carcinomas, in which HIF1α acts as a tumor suppressor by inhibiting cell-autonomous proliferation. Here, we find that, unexpectedly, HIF1α suppresses lower glycolysis after the glyceraldehyde 3-phosphate dehydrogenase (GAPDH) step, leading to reduced lactate secretion in different tumor cell types when cells encounter a limited pyruvate supply such as that typically found in the tumor microenvironment in vivo. This is because HIF1α-dependent attenuation of mitochondrial oxygen consumption increases the NADH/NAD+ ratio that suppresses the activity of the NADH-sensitive GAPDH glycolytic enzyme. This is manifested when pyruvate supply is limited, since pyruvate acts as an electron acceptor that prevents the increment of the NADH/NAD+ ratio. Furthermore, this anti-glycolytic function provides a molecular basis to explain how HIF1α can suppress tumor cell proliferation by increasing the NADH/NAD+ ratio.

Novel Alphaproteobacteria transcribe genes for nitric oxide transformation at high levels in a marine oxygen-deficient zone

Marine oxygen-deficient zones (ODZs) are portions of the ocean where intense nitrogen loss occurs primarily via denitrification and anammox. Despite many decades of study, the identity of the microbes that catalyze nitrogen loss in ODZs is still being elucidated. Intriguingly, high transcription of genes in the same family as the nitric oxide dismutase (nod) gene from Methylomirabilota has been reported in the anoxic core of ODZs. Here, we show that the most abundantly transcribed nod genes in the Eastern Tropical North Pacific ODZ belong to a new order (UBA11136) of Alphaproteobacteria, rather than Methylomirabilota as previously assumed. Gammaproteobacteria and Planctomycetia also transcribe nod, but at lower relative abundance than UBA11136 in the upper ODZ. The nod-transcribing Alphaproteobacteria likely use formaldehyde and formate as a source of electrons for aerobic respiration, with additional electrons possibly from sulfide oxidation. They also transcribe multiheme cytochrome (here named ptd) genes for a putative porin-cytochrome protein complex of unknown function, potentially involved in extracellular electron transfer. Molecular oxygen for aerobic respiration may originate from nitric oxide dismutation via cryptic oxygen cycling. Our results implicate Alphaproteobacteria order UBA11136 as a significant player in marine nitrogen loss and highlight their potential in one-carbon, nitrogen, and sulfur metabolism in ODZs.IMPORTANCEIn marine oxygen-deficient zones (ODZs), microbes transform bioavailable nitrogen to gaseous nitrogen, with nitric oxide as a key intermediate. The Eastern Tropical North Pacific contains the world's largest ODZ, but the identity of the microbes transforming nitric oxide remains unknown. Here, we show that highly transcribed nitric oxide dismutase (nod) genes belong to Alphaproteobacteria of the novel order UBA11136, which lacks cultivated isolates. These Alphaproteobacteria show evidence for aerobic respiration, using oxygen potentially sourced from nitric oxide dismutase, and possess a novel porin-cytochrome protein complex with unknown function. Gammaproteobacteria and Planctomycetia transcribe nod at lower levels. Our results pinpoint the microbes mediating a key step in marine nitrogen loss and reveal an unexpected predicted metabolism for marine Alphaproteobacteria.

Exploring Advanced Oxygen Reduction Reaction Electrocatalysts: The Potential of Metal-Free and Non-Pyrolyzed Covalent Organic Frameworks

Oxygen reduction reaction (ORR) electrocatalysis is an area of increasing interest for the in-situ production of H2O2 or the development of energy-related devices such as hydrogen fuel cells. Although pyrolyzed catalysts still offer the best performances to date with reference to the organic-based catalysts, metal-free and non-pyrolyzed covalent organic frameworks (COFs) stands out as promising alternatives candidates due to their favourable characteristics such as crystallinity, porosity, and organic composition, allowing the study of structural-property relationships. Herein, we present the design principles and recent advances in COFs-based ORR electrocatalysts, demonstrating how composition influences the activity and electronic pathway of the oxygen reduction process.

Factors that mediate change in creatinine and acute kidney injury after the Norwood operation: insights from high-fidelity haemodynamic monitoring data

BACKGROUND

Acute kidney injury is a common postoperative complication of paediatric cardiac surgery associated with increased morbidity and mortality. The purpose of this study is to characterise associations between haemodynamic parameters, clinical parameters, and medical interventions, on acute kidney injury.

METHODS

Nine patients with univentricular physiology undergoing the Norwood procedure from a single-centre tertiary care paediatric cardiac ICU were included (September 2022 to March 2023). Patients were monitored with the T3 software. Data were analysed using a Fisher exact test, Mann-Whitney-U test, LASSO-based machine learning techniques, and receiver operator curve analyses.

RESULTS

Over 27,000 datapoints were included. Acute kidney injury occurred in 2 patients (22%) during this period. Net fluid balance and renal oxygen extraction were independently associated with acute kidney injury, while commonly used metrics of pressure (systolic, diastolic, or mean arterial blood pressure) were not. The resulting acute kidney injury risk score was (4.1 × fluid balance) + (1.9 × renal oxygen extraction). The risk score was significantly higher in acute kidney injury with a score of 32.9 compared to 7.9 (p < 0.01). Optimal cut-offs for fluid balance (7 mL/hr) and renal oxygen extraction (29%) were identified. Higher serum creatinine:baseline creatinine ratio was associated with a higher mean airway pressure, higher renal oxygen extraction, higher mean arterial blood pressure, higher vasoactive inotropic score, and fluid balance.

CONCLUSION

Among patients with univentricular physiology undergoing the Norwood procedure, renal oxygen extraction and a higher net fluid balance are independently associated with increased risk of acute kidney injury. Renal perfusion pressure is not significantly associated with acute kidney injury.

Multiparameter Sensing of Oxygen and pH at Biological Interfaces via Hyperspectral Imaging of Luminescent Sensor Nanoparticles

Chemical dynamics in biological samples are seldom stand-alone processes but represent the outcome of complicated cascades of interlinked reaction chains. In order to understand these processes and how they correlate, it is important to monitor several parameters simultaneously at high spatial and temporal resolution. Hyperspectral imaging is a promising tool for this, as it provides broad-range spectral information in each pixel, enabling the use of multiple luminescent indicator dyes, while simultaneously providing information on sample structures and optical properties. In this study, we first characterized pH- and O2-sensitive indicator dyes incorporated in different polymer matrices as optical sensor nanoparticles to provide a library for (hyperspectral) chemical imaging. We then demonstrate the successful combination of a pH-sensitive indicator dye (HPTS(DHA)3), an O2-sensitive indicator dye (PtTPTBPF), and two reference dyes (perylene and TFPP), incorporated in polymer nanoparticles for multiparameter chemical imaging of complex natural samples such as green algal biofilms (Chlorella sorokiniana) and seagrass leaves (Zostera marina) with high background fluorescence. We discuss the system-specific challenges and limitations of our approach and further optimization possibilities. Our study illustrates how multiparameter chemical imaging with hyperspectral read-out can now be applied on natural samples, enabling the alignment of several chemical parameters to sample structures.

Increase in temperature facilitates Campylobacter jejuni biofilm formation under both aerobic and microaerobic incubation

The formation of Campylobacter jeuni biofilms on processing surfaces is a significant concern in poultry processing, contributing to food safety risks. This study focused on assessing the biofilm forming capabilities of 12 field isolates of C. jejuni of different aerotolerance categories on stainless steel surfaces, a prevalent material in poultry processing environments. Working cultures of each isolate were prepared to approximately 6 log CFU/mL and incubated on stainless steel coupons under microaerobic or aerobic conditions at room temperature or 42°C for 72 h. Biofilm attached cells were enumerated using direct plating and biofilm density was measured using a crystal violet assay by measuring the optical density (OD600) a. Data analysis was conducted using the PROC GLIMMIX procedure in SAS 9.4 with a significance level of 0.05. The study revealed a notable interaction between aerotolerance categories and temperature (P < 0.039) impacting the number of biofilms attached C. jejuni cells on stainless steel coupons. All isolates had significantly higher counts when incubated at 42°C compared to room temperature, regardless of oxygen level (P < 0.001). Furthermore, stronger biofilm density was observed at 42°C compared to room temperature, regardless of oxygen level. These findings underscore the influence of temperature on the biofilm forming ability of C. jejuni. The ability of these field isolates to form biofilms under various environmental conditions suggests a heightened potential for surface colonization and increased infection risk in poultry processing facilities.

Hypoxia research, where to now?

Investigating how cells and organisms sense and respond to O2 levels is essential to our understanding of physiology and pathology. This field has advanced considerably since the discovery of the major transcription factor family, hypoxia-inducible factor (HIF), and the enzymes that control its levels: prolyl hydroxylases (PHDs). However, with its expansion, new complexities have emerged. Herein we highlight three main areas where, in our opinion, the research community could direct some of their attention. These include non-transcriptional roles of HIFs, specificity and O2 sensitivity of 2-oxoglutarate-dependent dioxygenases (2-OGDDs), and new tools and methods to detect O2 concentrations in cells and organs. A greater understanding of these areas would answer big questions and help drive our knowledge of cellular responses to hypoxia forward.

Towards Sulphite-Free Winemaking: A New Horizon of Vinification and Maturation

The complex dynamics between oxygen exposure, sulphur dioxide (SO2) utilization, and wine quality are of the utmost importance in wine sector, and this study aims to explore their fine balance in winemaking. As a common additive, SO2 works as an antiseptic and antioxidant. However, its excessive use has raised health concerns. Regulatory guidelines, including Council Regulation (EC) N° 1493/1999 and Commission Regulation (EC) No 1622/2000, dictate SO2 concentrations in wines. The increasing demand for natural preservatives is driving the search for alternatives, with natural plant extracts, rich in phenolic compounds, emerging as promising substitutes. In this context, Bioma Company has proposed alternative additives deriving from vineyard waste to replace SO2 during winemaking. Thus, the aim of the present work was to compare the compositional characteristics between the product obtained with the alternative vinification and the traditional one during the winemaking, as well as the aroma compositions of the final wines. After a year of experimentation, the wines produced with Bioma products showed compositional characteristics comparable to their traditional counterparts. Notably, these wines comply with current legislation, with significantly reduced total sulphur content, allowing their designation as "without added sulphites". Bioma products emerge as potential catalysts for sustainable and health-conscious winemaking practices, reshaping the landscape of the industry.

Petroleum jelly: A comprehensive review of its history, uses, and safety

Petrolatum, also known as petroleum jelly, is a widely used topical agent, with a variety of uses in dermatology. Despite its popularity, many myths surround this ubiquitous dermatologic staple. This review details the history of petrolatum and how it is manufactured as well as how its biologic properties make it a great moisturizer. Additionally, data on its potential for flammability, allergenicity, and comedogenicity are detailed, dispelling misconceptions about petrolatum use around oxygen and as a cause of acne. The uses and benefits of petrolatum in dermatology are wide-ranging-a patch test instrument, a vehicle for medicated ointments, and a wound care essential. Given its ubiquitous presence, it is important for dermatologists to understand the history, safety profile, and myths surrounding this humble skincare staple.

Oxygen saturation thresholds in managing sickle cell disease at US children's hospitals

BACKGROUND

Adequate oxygen saturation (SpO2 ) is crucial for managing sickle cell disease (SCD). Children with SCD are at increased risk for occult hypoxemia; therefore, understanding SpO2 threshold practices would help identify barriers to oxygen optimization in a population sensitive to oxyhemoglobin imbalances. We investigated SpO2 cutoff levels used in clinical algorithms for management of acute SCD events at children's hospitals across the United States, and determined their consistency with recommended national guidelines (SpO2  > 95%).

METHODS

Clinical pathways and algorithms used for the management of vaso-occlusive crisis (VOC) and acute chest syndrome (ACS) in SCD were obtained and reviewed from large children's hospitals in the United States.

RESULTS

Responses were obtained from 94% (140/149) of eligible children's hospitals. Of these, 63 (45%) had available clinical algorithms to manage VOC and ACS. SpO2 cutoff was provided in 71.4% (45/63) of clinical algorithms. Substantial variation in SpO2 cutoff levels was noted, ranging from ≥90% to more than 95%. Only seven hospitals (5% of total hospitals and 15.6% of hospitals with clinical algorithms available) specified oxygen cutoffs that were consistent with national guidelines. Hospitals geographically located in the South (46.8%; n = 29/62) and Midwest (54.8%; n = 17/31) were more likely to have VOC and ACS clinical algorithms, compared to the Northeast (26.5%; n = 9/34) and West (36.4%; n = 8/22).

CONCLUSION

There is inconsistency in the use of clinical algorithms and oxygen thresholds for VOC and ACS across US children's hospitals. Children with SCD could be at risk for insufficient oxygen therapy during adverse acute events.

Oxygen and the Spark of Human Brain Evolution: Complex Interactions of Metabolism and Cortical Expansion across Development and Evolution

Scientific theories on the functioning and dysfunction of the human brain require an understanding of its development-before and after birth and through maturation to adulthood-and its evolution. Here we bring together several accounts of human brain evolution by focusing on the central role of oxygen and brain metabolism. We argue that evolutionary expansion of human transmodal association cortices exceeded the capacity of oxygen delivery by the vascular system, which led these brain tissues to rely on nonoxidative glycolysis for additional energy supply. We draw a link between the resulting lower oxygen tension and its effect on cytoarchitecture, which we posit as a key driver of genetic developmental programs for the human brain-favoring lower intracortical myelination and the presence of biosynthetic materials for synapse turnover. Across biological and temporal scales, this protracted capacity for neural plasticity sets the conditions for cognitive flexibility and ongoing learning, supporting complex group dynamics and intergenerational learning that in turn enabled improved nutrition to fuel the metabolic costs of further cortical expansion. Our proposed model delineates explicit mechanistic links among metabolism, molecular and cellular brain heterogeneity, and behavior, which may lead toward a clearer understanding of brain development and its disorders.

Mechanobiological stimulation in organ-on-a-chip systems reduces hepatic drug metabolic capacity in favor of regenerative specialization

Hepatic physiology depends on the liver's complex structural composition which among others, provides high oxygen supply rates, locally differential oxygen tension, endothelial paracrine signaling, as well as residual hemodynamic shear stress to resident hepatocytes. While functional improvements were shown by implementing these factors into hepatic culture systems, direct cause-effect relationships are often not well characterized-obfuscating their individual contribution in more complex microphysiological systems. By comparing increasingly complex hepatic in vitro culture systems that gradually implement these parameters, we investigate the influence of the cellular microenvironment to overall hepatic functionality in pharmacological applications. Here, hepatocytes were modulated in terms of oxygen tension and supplementation, endothelial coculture, and exposure to fluid shear stress delineated from oxygen influx. Results from transcriptomic and metabolomic evaluation indicate that particularly oxygen supply rates are critical to enhance cellular functionality-with cellular drug metabolism remaining comparable to physiological conditions after prolonged static culture. Endothelial signaling was found to be a major contributor to differential phenotype formation known as metabolic zonation, indicated by WNT pathway activity. Lastly, oxygen-delineated shear stress was identified to direct cellular fate towards increased hepatic plasticity and regenerative phenotypes at the cost of drug metabolic functionality - in line with regenerative effects observed in vivo. With these results, we provide a systematic evaluation of critical parameters and their impact in hepatic systems. Given their adherence to physiological effects in vivo, this highlights the importance of their implementation in biomimetic devices, such as organ-on-a-chip systems. Considering recent advances in basic liver biology, direct translation of physiological structures into in vitro models is a promising strategy to expand the capabilities of pharmacological models.

Tracking the early events of photosymbiosis evolution

Oxygenic photosynthesis evolved in cyanobacteria around 3.2 giga-annum (Ga) ago and was acquired by eukaryotes starting around 1.8 Ga ago by endosymbiosis. Photosymbiosis results either from integration of a photosynthetic bacteria by heterotrophic eukaryotes (primary photosymbiosis) or by successive integration of photosymbiotic eukaryotes by heterotrophic eukaryotes (secondary photosymbiosis). Primary endosymbiosis is thought to have been a rare event, whereas secondary and higher-order photosymbiosis evolved multiple times independently in different taxa. Despite its recurrent evolution, the molecular and cellular mechanisms underlying photosymbiosis are unknown. In this opinion, we discuss the primary events leading to the establishment of photosymbiosis, and we present recent research suggesting that, in some cases, domestication occurred instead of symbiosis, and how oxygen and host immunity can be involved in symbiont maintenance.

Expression and metabolism profiles of CVT associated with inflammatory responses and oxygen carrier ability in the brain

AIM

As the main type of stroke, the incidence of cerebral venous thrombosis (CVT) has been rising. However, the comprehensive mechanisms behind it remain unclear. Thus, the multi-omics study is required to investigate the mechanism after CVT and elucidate the characteristic pathology of venous stroke and arterial stroke.

METHODS

Adult rats were subjected to CVT and MCAO models. Whole-transcriptome sequencing (RNA-seq) and untargeted metabolomics analysis were performed to construct the transcriptome and metabolism profiles of rat brains after CVT and also MCAO. The difference analysis, functional annotation, and enrichment analysis were also performed.

RESULTS

Through RNA-seq analysis, differentially expressed genes (DEGs) were screened. 174 CVT specific genes including Il1a, Ccl9, Cxxl6, Tnfrsf14, etc., were detected. The hemoglobin genes, including both Hba and Hbb, were significantly downregulated after CVT, compared both to the MCAO and Sham groups. Metabolism analysis showed that CVT had higher heterogeneity of metabolism compared to MCAO. Metabolites including N-stearoyltyrosine, 5-methoxy-3-indoleaceate, Afegostat, pipecolic acid, etc. were specially regulated in CVT. Through the immune infiltration analysis, it was found that CVT had a higher immune response, with the abundance of certain types of immune cells increased, especially T helper cells. It was important to find the prevalence of the activation of inflammatory chemokine, cytokine, NOD-like pathway, and neutrophil extracellular trap.

CONCLUSION

We explored and analyzed the gene expression and metabolomic characteristics of CVT, revealed the specific inflammatory reaction mechanism of CVT and found the markers in transcriptome and metabolism levels. It points out the direction for CVT early diagnosis and treatment.

Topical oxygen therapy and singlet oxygen in wound healing: A scoping review

The aim of this scoping review was to provide an overview of current research into topical oxygen therapies including the under-researched singlet oxygen for wound healing. A scoping review was undertaken using five databases. After duplicates and ineligible studies were excluded, 49 studies were included for a narrative review. Out of the included 49 studies, 45 (91.8%) were published in the past 10 years (2013-2023) with 32 (65.3%) published in the past 5 years (2018-2023). Eight of the studies were systematic reviews and/or meta-analysis and 18 were RCTs. The search identified zero human RCTs on singlet oxygen, but one human cohort study and five studies in animals. There is evidence that topical oxygen therapy may be useful for the treatment of chronic wounds, mainly diabetic foot ulcers. Singlet oxygen has shown potential, but would need further confirmation in controlled human trials, including more research to understand the bio-properties.

Association of active oxygen-releasing gel and photodynamic therapy in the treatment of residual periodontal pockets in type 2 diabetic patients: A randomized controlled clinical study

BACKGROUND

The aim of this study was to evaluate the effect of active oxygen-releasing gel as an adjuvant, with and without antimicrobial photodynamic therapy (aPDT), in the treatment of residual pockets in periodontal patients with type 2 diabetes mellitus (DM2).

METHODS

Patients with residual pockets with probing depth (PD) ≥4 mm and bleeding on probing (BOP) were divided into the following groups: SI (n = 17)-subgingival instrumentation in a single session; BM (n = 17)-SI followed by local application of active oxygen-releasing gel inside the periodontal pocket for 3 min; BM + aPDT (n = 17)-SI followed by application of BM for 3 min and pocket irrigation with methylene blue, and 660-nm diode laser irradiation at 100 mW for 50 s. The periodontal clinical parameters, serum levels of glycated hemoglobin, and immunological analysis of crevicular fluid were evaluated. All data were submitted to statistical analysis (α = 5%).

RESULTS

A significant reduction in BOP was verified at 90 and 180 days in the BM + aPDT group. The percentage of sites with PD ≥ 4 mm was significantly reduced at 90 days in BM + aPDT and BM, whereas after 180 days only BM showed a significant reduction. In the BM + aPDT group, there was a significant reduction in tumor necrosis factor α levels at 90 days. There were no differences between the treatments.

CONCLUSION

The use of adjuvant active oxygen-releasing gel, with or without aPDT, resulted in the same clinical benefits as SI in the treatment of residual pockets in poorly controlled DM2 patients.

Early Hyperoxemia and 2-year Outcomes in Infants with Hypoxic-ischemic Encephalopathy: A Secondary Analysis of the Infant Cooling Evaluation Trial

OBJECTIVE

To determine the causal relationship between exposure to early hyperoxemia and death or major disability in infants with hypoxic-ischemic encephalopathy (HIE).

STUDY DESIGN

We analyzed data from the Infant Cooling Evaluation (ICE) trial that enrolled newborns ≥35 weeks' gestation with moderate-severe HIE, randomly allocated to hypothermia or normothermia. The primary outcome was death or major sensorineural disability at 2 years. We included infants with arterial pO2 measured within 2 hours of birth. Using a directed acyclic graph, we established that markers of severity of perinatal hypoxia-ischemia and pCO2 were a minimally sufficient set of variables for adjustment in a regression model to estimate the causal relationship between arterial pO2 and death/disability.

RESULTS

Among 221 infants, 116 (56%) had arterial pO2 and primary outcome data. The unadjusted analysis revealed a U-shaped relationship between arterial pO2 and death or major disability. Among hyperoxemic infants (pO2 100-500 mmHg) the proportion with death or major disability was 40/58 (0.69), while the proportion in normoxemic infants (pO2 40-99 mmHg) was 20/48 (0.42). In the adjusted model, hyperoxemia increased the risk of death or major disability (adjusted risk ratio 1.61, 95% CI 1.07-2.00, P = .03) in relation to normoxemia.

CONCLUSION

Early hyperoxemia increased the risk of death or major disability among infants who had an early arterial pO2 in the ICE trial. Limitations include the possibility of residual confounding and other causal biases. Further work is warranted to confirm this relationship in the era of routine therapeutic hypothermia.

Diverse mechanisms control amino acid-dependent environmental alkalization by Candida albicans

Candida albicans has the capacity to neutralize acidic growth environments by releasing ammonia derived from the catabolism of amino acids. The molecular components underlying alkalization and its physiological significance remain poorly understood. Here, we present an integrative model with the cytosolic NAD+-dependent glutamate dehydrogenase (Gdh2) as the principal ammonia-generating component. We show that alkalization is dependent on the SPS-sensor-regulated transcription factor STP2 and the proline-responsive activator Put3. These factors function in parallel to derepress GDH2 and the two proline catabolic enzymes PUT1 and PUT2. Consistently, a double mutant lacking STP2 and PUT3 exhibits a severe alkalization defect that nearly phenocopies that of a gdh2-/- strain. Alkalization is dependent on mitochondrial activity and in wild-type cells occurs as long as the conditions permit respiratory growth. Strikingly, Gdh2 levels decrease and cells transiently extrude glutamate as the environment becomes more alkaline. Together, these processes constitute a rudimentary regulatory system that counters and limits the negative effects associated with ammonia generation. These findings align with Gdh2 being dispensable for virulence, and based on a whole human blood virulence assay, the same is true for C. glabrata and C. auris. Using a transwell co-culture system, we observed that the growth and proliferation of Lactobacillus crispatus, a common component of the acidic vaginal microenvironment and a potent antagonist of C. albicans, is unaffected by fungal-induced alkalization. Consequently, although Candida spp. can alkalinize their growth environments, other fungal-associated processes are more critical in promoting dysbiosis and virulent fungal growth.

Predictors of 2-Year Mortality in Patients Receiving Long-Term Oxygen Therapy: A Prospective Observational Study

Background: Patients receiving long-term oxygen therapy are in a state of progressive respiratory dysfunction and have high mortality. However, the predictors of mortality in these patients have not yet been established. Objectives: This prospective observational study aimed to identify the predictors of two-year mortality in patients receiving long-term oxygen therapy. Design, Setting/Subjects: This two-year prospective observational study included 96 patients who received long-term oxygen therapy in the outpatient department of the National Hospital Organization Nishiniigata Chuo Hospital in Japan. Measurements: The updated Charlson Comorbidity Index, body mass index, handgrip strength, modified British Medical Research Council scale (mMRC), Barthel Index (BI), and Montreal Cognitive Assessment (MoCA) were collected in 2019 as a baseline. Outcome was defined as mortality due to chronic respiratory disease during the two-year follow-up period, and predictors were estimated using age- and sex-adjusted Cox proportional hazards model. Results: The 83 patients that were followed up, 30 (36%) died. The Cox proportional hazards model estimated handgrip strength (adjusted hazard ratio [HR]: 0.89; 95% confidence interval [CI]: 0.84-0.94; p < 0.01; Wald: 14.38.), mMRC (adjusted HR: 1.96; 95% CI: 1.36-2.83; p < 0.01; Wald: 13.16.), BI (adjusted HR: 0.95; 95% CI: 0.93-0.98; p < 0.01; Wald: 17.07.), and MoCA (adjusted HR: 2.17; 95% CI: 1.31-3.59; p < 0.01; Wald: 9.06) as predictors. Conclusions: This study indicated that handgrip strength, dyspnea, activities of daily living, and cognitive function were predictors of two-year mortality in patients receiving long-term oxygen therapy.

Hypoxia sensing in the body: An update on the peripheral and central mechanisms

An adequate supply of O2 is essential for the maintenance of cellular activity. Systemic or local hypoxia can be experienced during decreased O2 availability or associated with diseases, or a combination of both. Exposure to hypoxia triggers adjustments in multiple physiological systems in the body to generate appropriate homeostatic responses. However, with significant reductions in the arterial partial pressure of O2, hypoxia can be life-threatening and cause maladaptive changes or cell damage and death. To mitigate the impact of limited O2 availability on cellular activity, O2 chemoreceptors rapidly detect and respond to reductions in the arterial partial pressure of O2, triggering orchestrated responses of increased ventilation and cardiac output, blood flow redistribution and metabolic adjustments. In mammals, the peripheral chemoreceptors of the carotid body are considered to be the main hypoxic sensors and the primary source of excitatory feedback driving respiratory, cardiovascular and autonomic responses. However, current evidence indicates that the CNS contains specialized brainstem and spinal cord regions that can also sense hypoxia and stimulate brain networks independently of the carotid body inputs. In this manuscript, we review the discoveries about the functioning of the O2 chemoreceptors and their contribution to the monitoring of O2 levels in the blood and brain parenchyma and mounting cardiorespiratory responses to maintain O2 homeostasis. We also discuss the implications of the chemoreflex-related mechanisms in paediatric and adult pathologies.

Calcium Peroxide-Based Hydrogel Patch with Sustainable Oxygenation for Diabetic Wound Healing

Nonhealing diabetic wounds are predominantly attributed to the inhibition of angiogenesis, re-epithelialization, and extracellular matrix (ECM) synthesis caused by hypoxia. Although oxygen therapy has demonstrated efficacy in promoting healing, its therapeutic impact remains suboptimal due to unsustainable oxygenation. Here, this work proposes an oxygen-releasing hydrogel patch embedded with polyethylene glycol-modified calcium peroxide microparticles, which sustainably releases oxygen for 7 days without requiring any supplementary conditions. The released oxygen effectively promotes cell migration and angiogenesis under hypoxic conditions as validated in vitro. The in vivo tests in diabetic mice models show that the sustainably released oxygen significantly facilitates the synthesis of ECM, induces angiogenesis, and decreases the expression of inflammatory cytokines, achieving a diabetic wound healing rate of 84.2% on day 7, outperforming the existing oxygen-releasing approaches. Moreover, the proposed hydrogel patch is designed with porous, soft, antibacterial, biodegradable, and storage stability for 15 days. The proposed hydrogel patch is expected to be promising in clinics treating diabetic wounds.

Plants as a cost-effective source for customizable photosynthetic wound dressings: A proof of concept study

Oxygen is essential for tissue regeneration, playing a crucial role in several processes, including cell metabolism and immune response. Therefore, the delivery of oxygen to wounds is an active field of research, and recent studies have highlighted the potential use of photosynthetic biomaterials as alternative oxygenation approach. However, while plants have traditionally been used to enhance tissue regeneration, their potential to produce and deliver local oxygen to wounds has not yet been explored. Hence, in this work we studied the oxygen-releasing capacity of Marchantia polymorpha explants, showing their capacity to release oxygen under different illumination settings and temperatures. Moreover, co-culture experiments revealed that the presence of these explants had no adverse effects on the viability and morphology of fibroblasts in vitro, nor on the viability of zebrafish larvae in vivo. Furthermore, oxygraphy assays demonstrate that these explants could fulfill the oxygen metabolic requirements of zebrafish larvae and freshly isolated skin biopsies ex vivo. Finally, the biocompatibility of explants was confirmed through a human skin irritation test conducted in healthy volunteers following the ISO-10993-10-2010. This proof-of-concept study provides valuable scientific insights, proposing the potential use of freshly isolated plants as biocompatible low-cost oxygen delivery systems for wound healing and tissue regeneration.

The effects of oxygen addition on microstructure and mechanical properties of Ti-Mo alloys for biomedical application

The effective use of oxygen as an alloying element in Ti alloys is attractive due to the reduction of production cost and the increase in strength and hardness of the alloy. Although the oxygen addition in a Ti alloy increases strength and hardness, it may induce brittleness. An appropriate combination of alloying elements and thermomechanical treatment must be clarified for the use of oxygen as an alloying element. Ti-(0, 1.0, 2.0, 3.0)Mo-(0, 1.5, 3.0)O alloys were developed, and their microstructure and mechanical properties were examined. Ti-1Mo-3O alloy exhibited fine grains of α+β two phases having the tensile strength of 1,297 MPa with 15.5% for total strain at fracture. The Ti-1Mo-3O alloy has 1.5 times the tensile strength and the same total strain as the Ti-6Al-4V ELI alloy. Ti-(1.0, 2.0, 3.0)Mo-1.5O alloys also have excellent mechanical properties, with tensile strength of about 1,050-1,150 MPa and a total strain of about 20%-25%. In order to develop a high strength and moderate ductility Ti-Mo alloy using oxygen as an alloying element, the microstructure should have fine grains of α+β two phases with proper volume fraction of α and β phases and specific molybdenum concentration in β phase.

High-flow nasal cannula therapy for infants with bronchiolitis

BACKGROUND

Bronchiolitis is a common lower respiratory tract illness, usually of viral aetiology, affecting infants younger than 24 months of age and is the most common cause of hospitalisation of infants. It causes airway inflammation, mucus production and mucous plugging, resulting in airway obstruction. Effective pharmacotherapy is lacking and bronchiolitis is a major cause of morbidity and mortality. Conventional treatment consists of supportive therapy in the form of fluids, supplemental oxygen, and respiratory support. Traditionally, oxygen delivery is as a dry gas at 100% concentration via low-flow nasal prongs. However, the use of heated, humidified, high-flow nasal cannula (HFNC) therapy enables delivery of higher inspired gas flows of an air/oxygen blend, at 2 to 3 L/kg per minute up to 60 L/min in children. It can provide some level of continuous positive airway pressure (CPAP) to improve ventilation in a minimally invasive manner. This may reduce the need for invasive respiratory support, thus potentially lowering costs, with clinical advantages and fewer adverse effects.

OBJECTIVES

To assess the effects of HFNC therapy compared with conventional respiratory support in the treatment of infants with bronchiolitis.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, CINAHL, LILACS, and Web of Science (from June 2013 to December 2022). In addition, we consulted ongoing trial registers and experts in the field to identify ongoing studies, checked reference lists of relevant articles, and searched for conference abstracts. Date restrictions were imposed such that we only searched for studies published after the original version of this review.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) or quasi-RCTs that assessed the effects of HFNC (delivering oxygen or oxygen/room air blend at flow rates greater than 4 L/minute) compared to conventional treatment in infants (< 24 months) with a clinical diagnosis of bronchiolitis.

DATA COLLECTION AND ANALYSIS

Two review authors independently used a standard template to assess trials for inclusion and extract data on study characteristics, risk of bias elements, and outcomes. We contacted trial authors to request missing data. Outcome measures included the need for invasive respiratory support and time until discharge, clinical severity measures, oxygen saturation, duration of oxygen therapy, and adverse events.

MAIN RESULTS

In this update we included 15 new RCTs (2794 participants), bringing the total number of RCTs to 16 (2813 participants). Of the 16 studies, 11 compared high-flow to low-flow, and five compared high-flow to CPAP. These studies included infants less than 24 months of age as stated in our selection criteria. There were no significant differences in sex. We found that when comparing high-flow to low-flow oxygen therapy for infants with bronchiolitis there may be a reduction in the total length of hospital stay (mean difference (MD) -0.65 days, 95% confidence interval (CI) -1.23 to -0.06; P < 0.00001, I2 = 89%; 7 studies, 1951 participants; low-certainty evidence). There may also be a reduction in the duration of oxygen therapy (MD -0.59 days, 95% CI -1 to -0.18; P < 0.00001, I2 = 86%; 7 studies, 2132 participants; low-certainty evidence). We also found that there was probably an improvement in respiratory rate at one and 24 hours, and heart rate at one, four to six, and 24 hours in those receiving high-flow oxygen therapy when compared to pre-intervention baselines. There was also probably a reduced risk of treatment escalation in those receiving high-flow when compared to low-flow oxygen therapy (risk ratio (RR) 0.55, 95% CI 0.39 to 0.79; P = 0.001, I2 = 43%; 8 studies, 2215 participants; moderate-certainty evidence). We found no difference in the incidence of adverse events (RR 1.2, 95% CI 0.38 to 3.74; P = 0.76, I2 = 26%; 4 studies, 1789 participants; low-certainty evidence) between the two groups. The lack of comparable outcomes in studies comparing high-flow and CPAP, as well as the small numbers of participants, limited our ability to perform meta-analysis on this group.

AUTHORS' CONCLUSIONS

High-flow nasal cannula therapy may have some benefits over low-flow oxygen for infants with bronchiolitis in terms of a greater improvement in respiratory and heart rates, as well as a modest reduction in the length of hospital stay and duration of oxygen therapy, with a reduced incidence of treatment escalation. There does not appear to be a difference in the number of adverse events. Further studies comparing high-flow nasal cannula therapy and CPAP are required to demonstrate the efficacy of one modality over the other. A standardised clinical definition of bronchiolitis, as well as the use of a validated clinical severity score, would allow for greater and more accurate comparison between studies.

Effect of ultrasound-guided stellate ganglion block on cerebral oxygen metabolism and S100B protein during carotid endarterectomy

OBJECTIVE

To investigate the effect of ultrasound-guided stellate ganglion block (SGB) on cerebral oxygen metabolism and serum S100B during carotid endarterectomy (CEA).

METHODS

Patients who were prospectively enrolled to receive CEA under elective general anesthesia were randomized into an SGB group and a control group (ChiCTR2000033385). Before anesthesia, the SGB group underwent ipsilateral SGB under ultrasound guidance, while the control group did not. Ultrasound-guided right subclavian internal jugular vein catheterization was performed under general anesthesia. Mean arterial pressure (MAP) and heart rate (HR) were monitored at various time points (T0-T4). Arterial and internal jugular venous bulb blood were collected for blood gas analysis, determining jugular venous oxygen saturation (SjvO2), arteriovenous oxygen difference (AVDO2), cerebral oxygen extraction ratio (COER), lactate production rate (LPR), and lactate-oxygen index (LOI). The serum concentration of S100B in the internal jugular venous bulb at each time point was measured.

RESULTS

The results revealed significantly lower HR during anesthesia induction and surgery in the SGB group, with more stable MAP and HR during endotracheal intubation and surgery compared to the control group (P<0.05). The control group exhibited decreases at T3 and a slight increase at T4. SjvO2 was significantly higher in the SGB group, while AVDO2 and COER gradually decreased over time, but they were significantly higher in the control group (P<0.05). LPR and LOI in both groups peaked at T3 and were significantly different between T4 and T2 (P<0.05). Serum S100B levels in both groups rose and then decreased at each time point, but they were consistently lower in the SGB group (P<0.05).

CONCLUSION

SGB before CEA effectively suppresses the stress response, maintains intraoperative hemodynamic stability, improves brain tissue oxygen supply, and demonstrates a neuroprotective effect.

Extremely Enhanced Photoluminescence in MoS2-Derived Quantum Sheets

Molybdenum disulfide (MoS2) quantum sheets (QSs) are attractive for applications due to their tunable energy band structures and optical and electronic properties. The photoluminescence quantum yield (PLQY) of MoS2 QSs achieved by mechanical and liquid exfoliation and chemical vapor deposition is low. Some studies have reported that chemical treatment and elemental doping can improve the PLQY of transition metal dichalcogenides (TMDs), but this is limited by complex instruments and reactions. In this study, a heat treatment method based on a polar solvent is reported to improve the PLQY and photoluminescence (PL) intensity of MoS2 QSs at room temperature. The absolute PLQY of treated MoS2 QSs is increased to 18.5%, and the PL intensity is increased by a factor of 64. This method is also effective for tungsten disulfide (WS2) QSs. The PL enhancement of QSs is attributed to oxidation of the edges. Such passivation/deformation of MoS2 QSs facilitates the radiative route rather than the nonradiative route, resulting in extreme enhancement of the PL. Our work could provide novel insights/routes toward the PL enhancement of TMD QSs.

Diabetic Ocular Surface Has Defects in Oxygen Uptake Revealed by Optic Fiber Microsensor

Purpose

Diabetes mellitus causes diabetic keratopathy (DK). This and other ocular surface disorders are underdiagnosed and problematic for affected patients as well as recipients of diabetic donor corneas. Thus, it is important to find noninvasive means to facilitate determination of the potentially vision-threatening DK. It has been reported that diabetic corneas uptake significantly less oxygen (O2) than healthy controls. However, an integral assessment of the ocular surface is missing.

Methods

Using an optic-fiber O2 micro-sensor (optrode) we demonstrated recently that the healthy ocular surface displays a unique spatiotemporal map of O2 consumption. We hypothesize that diabetes impairs the spatiotemporal profile of O2 uptake at the ocular surface.

Results

Using streptozotocin (STZ)-induced diabetic mice, we found diminished O2 uptake and loss of the unique pattern across the ocular surface. A diabetic cornea consumes significantly less O2 at the bulbar conjunctiva and limbus, but not the central and peripheral cornea, compared to controls. Further, we show that, contrary to the healthy cornea, the diabetic cornea does not increase the O2 consumption at the limbus in the evening as the normal control.

Conclusions

Altogether, our measurements reveal a previously unknown impairment in O2 uptake at the diabetic cornea, making it a potential tool to diagnose ocular surface abnormalities and suggesting a new etiology mechanism.

Mitochondrial uncoupling proteins protect human airway epithelial ciliated cells from oxidative damage

Apical cilia on epithelial cells defend the lung by propelling pathogens and particulates out of the respiratory airways. Ciliated cells produce ATP that powers cilia beating by densely grouping mitochondria just beneath the apical membrane. However, this efficient localization comes at a cost because electrons leaked during oxidative phosphorylation react with molecular oxygen to form superoxide, and thus, the cluster of mitochondria creates a hotspot for oxidant production. The relatively high oxygen concentration overlying airway epithelia further intensifies the risk of generating superoxide. Thus, airway ciliated cells face a unique challenge of producing harmful levels of oxidants. However, surprisingly, highly ciliated epithelia produce less reactive oxygen species (ROS) than epithelia with few ciliated cells. Compared to other airway cell types, ciliated cells express high levels of mitochondrial uncoupling proteins, UCP2 and UCP5. These proteins decrease mitochondrial protonmotive force and thereby reduce production of ROS. As a result, lipid peroxidation, a marker of oxidant injury, decreases. However, mitochondrial uncoupling proteins exact a price for decreasing oxidant production; they decrease the fraction of mitochondrial respiration that generates ATP. These findings indicate that ciliated cells sacrifice mitochondrial efficiency in exchange for safety from damaging oxidation. Employing uncoupling proteins to prevent oxidant production, instead of relying solely on antioxidants to decrease postproduction oxidant levels, may offer an advantage for targeting a local area of intense ROS generation.

A Phase II Study of High-Flow Nasal Cannula for Relieving Dyspnea in Advanced Cancer Patients

CONTEXT

The efficacy and tolerability of high-flow nasal cannula (HFNC) for relieving dyspnea in advanced cancer patients with limited prognosis requires elucidation.

OBJECTIVES

The primary aim of this trial was to assess the efficacy and tolerability of HFNC regarding dyspnea including severe as well as moderate for longer durations in patients under palliative care.

METHODS

In this prospective study, hospitalized patients with advanced cancer who had dyspnea at rest (numeric rating scale, NRS≥3) and hypoxemia were enrolled. They were treated with HFNC for five days in the respiratory unit. Primary endpoint was mean change of modified Borg scale at 24 hours. Key secondary endpoints consisted of mean changes in modified Borg scale during the study period and feasibility (Trial Identifier, UMIN000035738).

RESULTS

Between February 2019 and February 2022, 25 patients were enrolled and 21 were analyzed. Twenty patients used inspired oxygen and the mean fraction of inspired oxygen (FiO2) was 0.34 (range, 0.21-1.0). At baseline, mean NRS (dyspnea) was 5.9 (range, 3-10). Median survival time was 19 days (range, 3-657). The mean change of modified Borg scale was 1.4 (80% confidence interval [CI]: 0.8-1.9) at 24 hours, 12 patients (57%) showed 1.0 points improvement of modified Borg scale. Within two hours, 15 patients showed 1.0 points improvement of modified Borg scale and such early responders were likely to maintain dyspnea improvement for 24 hours. Nineteen patients could continue HFNC for 24 hours and 11 patients completed five days of HFNC.

CONCLUSION

To our knowledge, this trial is the first prospective study to assess the five-day efficacy and tolerability of HFNC for dyspnea in patients under palliative care. Although this did not reach the prespecified endpoint, about half of the patients showed 1.0 point improvement, a minimally clinically important difference (MCID) in the chronic lung disease. HFNC can be a palliative treatment option in advanced cancer patients with dyspnea.

Associations between the intraoperative fraction of inspired intraoperative oxygen administration and days alive and out of hospital after surgery

Background

There is limited knowledge about the effect of liberal intraoperative oxygen on non-infectious complications and overall recovery from surgery.

Methods

In this retrospective cohort study, we investigated associations between mean intraoperative fraction of inspired oxygen (FiO2), and outcome in adults undergoing elective surgery lasting more than 2 h at a large metropolitan New Zealand hospital from 2012 to 2020. Patients were divided into low, medium, and high oxygen groups (FiO2 ≤ 0.4, 0.41-0.59, ≥0.6). The primary outcome was days alive and out of hospital at 90 days (DAOH90). The secondary outcomes were post-operative complications and admission to the ICU.

Results

We identified 15,449 patients who met the inclusion criteria. There was no association between FiO2 and DAOH90 when high FiO2 was analysed according to three groups. Using high FiO2 as the reference group there was an adjusted mean (95% confidence interval [CI]) difference of 0.09 (-0.06 to 0.25) days (P = 0.25) and 0.28 (-0.05 to 0.62) days (P = 0.2) in the intermediate and low oxygen groups, respectively. Low FiO2 was associated with increased surgical site infection: the adjusted odds ratio (OR) for low compared with high FiO2 was 1.53 (95% CI 1.12-2.10). Increasing FiO2 was associated with respiratory complications: the adjusted OR associated with each 10% point increase in FiO2 was 1.17 (95% CI 1.08-1.26) and the incidence of being admitted to an ICU had an adjusted OR of 1.1 (95% CI 1.03-1.18).

Conclusions

We found potential benefits, and risks, associated with liberal intraoperative oxygen administration indicating that randomised controlled trials are warranted.

Effects of propofol alone or in combination with ketamine on intraocular pressure in unpremedicated dogs

OBJECTIVE

To determine the effects of propofol (P) alone and in combination with ketamine (KP) at ratios of 1:1, 1:2, and 1:3 on intraocular pressure (IOP) in unpremedicated dogs.

ANIMALS STUDIED

A total of 28 cross-bred healthy dogs.

PROCEDURES

Dogs were randomly assigned to one of four groups (n = 7 per group) to receive intravenous P or KP at 1:1, 1:2, and 1:3 ratios, respectively. The infusion was administered at 0.6 mg/kg/min for 60 min. IOP, cardiorespiratory variables, rectal temperature (RT), and pedal reflex were recorded every 5 min for 60 min, starting from baseline (BL).

RESULTS

There was a statistically significant increase in IOP in all groups: P (p = .011), KP 1:1 (p = .003), KP 1:2 (p = .023), and KP 1:3 (p = .008). The IOP increase was less pronounced in the KP 1:2 group and was only significant (p = .023) at T45 compared with BL. A significant correlation was observed between IOP and SpO2 in P (r = -.215, p = .02), KP 1:2 (r = -.579, p < .01), and KP 1:3 (r = -.402, p < .01) groups. IOP significantly increased due to decreased SpO2 below 86.5% (p < .05).

CONCLUSIONS

Propofol alone and in combination with ketamine may increase preexisting IOP in unpremedicated dogs. SpO2 levels below 86.5% may trigger an increase in IOP. Administering KP in a 1:2 ratio at an infusion rate of 0.6 mg/kg/min does not significantly alter IOP for under 45 min in unpremedicated dogs with sufficient oxygenation.

Short-term hyperoxia induced mitochondrial respiratory chain complexes dysfunction and oxidative stress in lung of rats

BACKGROUND

Oxygen therapy is an alternative for many patients with hypoxemia. However, this practice can be dangerous as oxygen is closely associated with the development of oxidative stress.

METHODS

Male Wistar rats were exposed to hyperoxia with a 40% fraction of inspired oxygen (FIO2) and hyperoxia (FIO2 = 60%) for 120 min. Blood and lung tissue samples were collected for gas, oxidative stress, and inflammatory analyses.

RESULTS

Hyperoxia (FIO2 = 60%) increased PaCO2 and PaO2, decreased blood pH and caused thrombocytopenia and lymphocytosis. In lung tissue, neutrophil infiltration, nitric oxide concentration, carbonyl protein formation and the activity of complexes I and II of the mitochondrial respiratory chain increased. FIO2 = 60% decreased SOD activity and caused several histologic changes.

CONCLUSION

In conclusion, we have experimentally demonstrated that short-term exposure to high FIO2 can cause oxidative stress in the lung.

Effect of Acute Vasodilator Testing Using Oxygen in Pulmonary Hypertension Due to Left Heart Disease

BACKGROUND

Pulmonary vasodilators, including oxygen, have not shown consistent beneficial effects on pulmonary hypertension due to valvular heart disease (PH-VHD). Therefore, the study aimed to assess the effect of 100% fractional inspiration of oxygen (FiO2) on pulmonary and systemic hemodynamics in patients with combined pre- and post-capillary pulmonary hypertension (CpcPH) and isolated post-capillary pulmonary hypertension (IpcPH) due to PH-VHD.

METHODS

This prospective study was conducted among patients with PH-VHD undergoing mitral or aortic valve replacement or repair. The study was conducted after induction of anesthesia and pulmonary artery catheterization. Cardiac output was obtained using thermodilution and all direct, and derived hemodynamic variables were obtained at 30% and 100% FiO2. The patients were stratified a priori into responders {(≥10 mmHg fall in mean pulmonary artery pressure (MPAP)} and non-responders.

RESULTS

Fifty-seven patients completed the acute vasodilator test. The mean age and body mass index of the study population was 41.8 ± 14.1 years and 21.4 ± 4.6 kg/m2, respectively. There was a significant decrease in MPAP (40.77 ± 12.07 mmHg vs 36.74 ± 13.3 mmHg; P < .001) and pulmonary vascular resistance (PVR) {(median; Interquartile range (IQR); 388; 371 vs 323; 362 dynes sec.cm-5; P < .001) at 100% FiO2. Transpulmonary gradient (TPG) and diastolic pulmonary gradient (DPG) also decreased significantly (P < .001 and P < .001). Cardiac output did not change significantly. The magnitude of decrease in MPAP, PVR, TPG, DPG, and pulmonary artery compliance (PAC) between CpcPH and IpcPH was comparable. Responders did not show a significantly greater fall in MPAP, PVR, TPG, DPG, and PAC after surgery.

CONCLUSION

Hyperoxia may lead to reduction in MPAP and PVR in both hemodynamic phenotypes of PH-VHD. A larger sample size is required to support or refute the findings of this study.

Oxygen Therapy in Patients With Intermediate-Risk Acute Pulmonary Embolism: A Randomized Trial

BACKGROUND

The effect of supplemental oxygen therapy in patients with intermediate-risk pulmonary embolism (PE) who do not have hypoxemia at baseline is uncertain.

RESEARCH QUESTION

Does supplemental oxygen improve echocardiographic parameters in nonhypoxemic patients with intermediate-risk PE?

STUDY DESIGN AND METHODS

This pilot trial randomly assigned nonhypoxemic patients with stable PE and echocardiographic right ventricle (RV) enlargement to receive anticoagulation plus supplemental oxygen for the first 48 h vs anticoagulation alone. The primary outcome was normal echocardiographic RV size 48 h after randomization. Secondary efficacy outcomes were the numerical change in the RV to left ventricle (LV) diameter ratio measured 48 h and 7 days after randomization with respect to the baseline ratio measured at inclusion.

RESULTS

The study was stopped prematurely because of the COVID-19 pandemic after recruiting 70 patients (mean ± SD age, 67.3 ± 16.1 years; 36 female [51.4%]) with primary outcome data. Forty-eight h after randomization, normalization of the RV size occurred in 14 of the 33 patients (42.4%) assigned to oxygen and in eight of the 37 patients (21.6%) assigned to ambient air (P = .08). In the oxygen group, the mean RV to LV ratio was reduced from 1.28 ± 0.28 at baseline to 1.01 ± 0.16 at 48 h (P < .001); in the ambient air group, mean RV to LV ratios were 1.21 ± 0.18 at baseline and 1.08 ± 0.19 at 48 h (P < .01). At 90 days, one major bleeding event and one death (both in the ambient air group) had occurred.

INTERPRETATION

In analyses limited by a small number of enrollees, compared with ambient air, supplemental oxygen did not significantly increase the proportion of patients with nonhypoxemic intermediate-risk PE whose RV to LV ratio normalized after 48 h of treatment. This pilot trial showed improvement in some ancillary efficacy outcomes and provides support for a definitive clinical outcomes trial.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT04003116; URL: www.

CLINICALTRIALS

gov.

Interactions between zinc and NRF2 in vascular redox signalling

Recent evidence highlights the importance of trace metal micronutrients such as zinc (Zn) in coronary and vascular diseases. Zn2+ plays a signalling role in modulating endothelial nitric oxide synthase and protects the endothelium against oxidative stress by up-regulation of glutathione synthesis. Excessive accumulation of Zn2+ in endothelial cells leads to apoptotic cell death resulting from dysregulation of glutathione and mitochondrial ATP synthesis, whereas zinc deficiency induces an inflammatory phenotype, associated with increased monocyte adhesion. Nuclear factor-E2-related factor 2 (NRF2) is a transcription factor known to target hundreds of different genes. Activation of NRF2 affects redox metabolism, autophagy, cell proliferation, remodelling of the extracellular matrix and wound healing. As a redox-inert metal ion, Zn has emerged as a biomarker in diagnosis and as a therapeutic approach for oxidative-related diseases due to its close link to NRF2 signalling. In non-vascular cell types, Zn has been shown to modify conformations of the NRF2 negative regulators Kelch-like ECH-associated Protein 1 (KEAP1) and glycogen synthase kinase 3β (GSK3β) and to promote degradation of BACH1, a transcriptional suppressor of select NRF2 genes. Zn can affect phosphorylation signalling, including mitogen-activated protein kinases (MAPK), phosphoinositide 3-kinases and protein kinase C, which facilitate NRF2 phosphorylation and nuclear translocation. Notably, several NRF2-targeted proteins have been suggested to modify cellular Zn concentration via Zn exporters (ZnTs) and importers (ZIPs) and the Zn buffering protein metallothionein. This review summarises the cross-talk between reactive oxygen species, Zn and NRF2 in antioxidant responses of vascular cells against oxidative stress and hypoxia/reoxygenation.

Enhancing exercise tolerance in interstitial lung disease with high-flow nasal cannula oxygen therapy: A randomized crossover trial

BACKGROUND AND OBJECTIVE

Interstitial lung disease (ILD) is characterized by dyspnoea on exertion and exercise-induced hypoxaemia. High-flow nasal cannula (HFNC) therapy reduces the respiratory workload through higher gas flow and oxygen supplementation, which may affect exercise tolerance. This study aimed to examine the effects of oxygen and gas flow rates through HFNC therapy on exercise tolerance in ILD patients.

METHODS

We conducted three-treatment crossover study. All ILD patients performed the exercises on room air (ROOM AIR setting: flow, 0 L/min; fraction of inspired oxygen [FiO2 ], 0.21), HFNC (FLOW setting: flow 40 L/min, FiO2 0.21), and HFNC with oxygen supplementation (FLOW + OXYGEN setting: flow 40 L/min, FiO2 0.6). The primary endpoint was the endurance time, measured using constant-load cycle ergometry exercise testing at a peak work rate of 80%.

RESULTS

Twenty-five participants (10 men, 71.2 ± 6.7 years) were enrolled. The increase in exercise duration between the ROOM AIR and FLOW was 46.3 s (95% CI, -6.1 to 98.7; p = 0.083), and the FLOW and FLOW + OXYGEN was 91.5 s (39.1-143.9; p < 0.001). The percutaneous oxygen saturation (SpO2 ) at rest was significantly higher with the FLOW + OXYGEN setting than with the ROOM AIR and FLOW settings, and the difference persisted during exercise. At equivalent time points during exercise, the SpO2 with the FLOW setting was significantly higher than that with the ROOM AIR setting.

CONCLUSION

Oxygen supplementation in HFNC therapy improved exercise tolerance and SpO2 . We found that gas flow alone did not improve exercise tolerance, but improved SpO2 during exercise.

Superoxide, nitric oxide and peroxynitrite production by macrophages under different physiological oxygen tensions

Macrophages count on two O2-consuming enzymes to form reactive radical species: NAPDH oxidase 2 (Nox2) and nitric oxide synthase 2 (inducible isoform, iNOS) that produce superoxide radical (O2•-) and nitric oxide (•NO), respectively. If formed simultaneously, the diffusion-controlled reaction of O2•- and •NO yields peroxynitrite, a potent cytotoxic oxidant. In human tissues and cells, the oxygen partial pressure (pO2) normally ranges within 2-14 %, with a typical average pO2 value for most tissues ca. 5 %. Given that O2 is a substrate for both Nox2 and iNOS, its tissue and cellular concentration can affect O2•- and •NO production. Also, O2 is a modulator of the macrophage adaptative response and may influence iNOS expression in a hypoxia inducible factor 1-α (HIF1α-)-dependent manner. However, most of the reported experiments in cellula, analyzing the formation and effects of O2•- and •NO during macrophage activation and cytotoxicity towards pathogens, have been performed in cells exposed to atmospheric air supplemented with 5 % CO2; under these conditions, most cells are exposed to supraphysiologic oxygen tensions (ca. 20 % O2) which are far from the physiological pO2. Here, the role of O2 as substrate in the oxidative response of J774A.1 macrophages was explored upon exposure to different pO2 and O2•- and •NO formation rates were measured, obtaining a KM of 26 and 42 μM O2 for Nox2 and iNOS, respectively. Consequently, peroxynitrite formation was influenced by pO2, reaching a maximum at ≥ 10 % O2, but even at levels as low as 2 % O2, a substantial formation rate of this oxidant was detected. Indeed, the cytotoxic capacity of immunostimulated macrophages against the intracellular parasite T. cruzi was significant, even at low pO2 values, confirming the role of peroxynitrite as a potent oxidizing cytotoxin within a wide range of physiological oxygen tensions.

The Proteome of Extracellular Vesicles Released from Pulmonary Microvascular Endothelium Reveals Impact of Oxygen Conditions on Biotrauma

The lung can experience different oxygen concentrations, low as in hypoxia, high as under supplemental oxygen therapy, or oscillating during intermittent hypoxia as in obstructive sleep apnea or intermittent hypoxia/hyperoxia due to cyclic atelectasis in the ventilated patient. This study aimed to characterize the oxygen-condition-specific protein composition of extracellular vesicles (EVs) released from human pulmonary microvascular endothelial cells in vitro to decipher their potential role in biotrauma using quantitative proteomics with bioinformatic evaluation, transmission electron microscopy, flow cytometry, and non-activated thromboelastometry (NATEM). The release of vesicles enriched in markers CD9/CD63/CD81 was enhanced under intermittent hypoxia, strong hyperoxia and intermittent hypoxia/hyperoxia. Particles with exposed phosphatidylserine were increased under intermittent hypoxia. A small portion of vesicles were tissue factor-positive, which was enhanced under intermittent hypoxia and intermittent hypoxia/hyperoxia. EVs from treatment with intermittent hypoxia induced a significant reduction of Clotting Time in NATEM analysis compared to EVs isolated after normoxic exposure, while after intermittent hypoxia/hyperoxia, tissue factor in EVs seems to be inactive. Gene set enrichment analysis of differentially expressed genes revealed that EVs from individual oxygen conditions potentially induce different biological processes such as an inflammatory response under strong hyperoxia and intermittent hypoxia/hyperoxia and enhancement of tumor invasiveness under intermittent hypoxia.

Mechanisms of CH4 activation over oxygen-preadsorbed transition metals by ReaxFF and AIMD simulations

The chemisorbed oxygen usually promotes the CH bond activation over less active metals like IB group metals but has no effect or even an inhibition effect over more active metals like Pd based on the static electronic structure study. However, the understanding in terms of dynamics knowledge is far from complete. In the present work, methane dissociation on the oxygen-preadsorbed transition metals including Au, Cu, Ni, Pt, and Pd is systemically studied by reactive force field (ReaxFF). The ReaxFF simulation results indicate that CH4 molecules mainly undergo the direct dissociation on Ni, Pt, and Pd surfaces, while undergo the oxygen-assisted dissociation on Au and Cu surfaces. Additionally, the ab initio molecular dynamics (AIMD) simulations with the umbrella sampling are employed to study the free-energy changes of CH4 dissociation, and the results further support the CH4 dissociation pathway during the ReaxFF simulations. The present results based on ReaxFF and AIMD will provide a deeper dynamic understanding of the effects of pre-adsorbed oxygen species on the CH bond activation compared to that of static DFT.

Using Machine Learning to Overcome Interfering Oxygen Effects in a Graphene Volatile Organic Compound Sensor

Discriminating between volatile organic compounds (VOCs) for applications including disease diagnosis and environmental monitoring, is often complicated by the presence of interfering compounds such as oxygen. Graphene sensors are effective at detecting VOCs; however, they are also known to be highly sensitive to oxygen. Therefore, the combined effects of each of these gases on graphene sensors must be understood. In this work, we use graphene variable capacitor (varactor) sensors to examine the cross-selectivity of oxygen at 3 concentrations and 3 VOCs (ethanol, methanol, and methyl ethyl ketone) at 5 concentrations each. The sensor responses exhibit distinct shapes dependent on the relative concentrations in mixtures of oxygen and VOCs. Because the entire response shape is therefore informative for distinguishing between each gas mixture, a classification algorithm that utilizes entire sequences of data is needed. Accordingly, a long short-term memory (LSTM) network is used to classify the mixtures and VOC concentrations. The model achieves 100% accurate classification of the VOC type, even in the presence of varying levels of oxygen. When the VOC type and VOC concentration are classified, we show that the sensors can provide VOC concentration resolution within approximately 200 ppm. Throughout this work, we also demonstrate that an effective gas mixture classification can be achieved, even while the sensors exhibit varied drift patterns typical of graphene sensors. This is made possible due to the data analysis and machine learning methods employed.

Seasonal dynamics of the microbial methane filter in the water column of a eutrophic coastal basin

In coastal waters, methane-oxidizing bacteria (MOB) can form a methane biofilter and mitigate methane emissions. The metabolism of these MOBs is versatile, and the resilience to changing oxygen concentrations is potentially high. It is still unclear how seasonal changes in oxygen availability and water column chemistry affect the functioning of the methane biofilter and MOB community composition. Here, we determined water column methane and oxygen depth profiles, the methanotrophic community structure, methane oxidation potential, and water-air methane fluxes of a eutrophic marine basin during summer stratification and in the mixed water in spring and autumn. In spring, the MOB diversity and relative abundance were low. Yet, MOB formed a methane biofilter with up to 9% relative abundance and vertical niche partitioning during summer stratification. The vertical distribution and potential methane oxidation of MOB did not follow the upward shift of the oxycline during summer, and water-air fluxes remained below 0.6 mmol m-2 d-1. Together, this suggests active methane removal by MOB in the anoxic water. Surprisingly, with a weaker stratification, and therefore potentially increased oxygen supply, methane oxidation rates decreased, and water-air methane fluxes increased. Thus, despite the potential resilience of the MOB community, seasonal water column dynamics significantly influence methane removal.

The impact of dissolved oxygen concentration on the swimming performance and welfare of ballan wrasse (Labrus bergylta Ascanius, 1767)

Sea lice (Lepeophtheirus salmonis [Krøyer, 1838]) are a key issue for salmon aquaculture, contributing to increased mortality for both wild and farmed salmon if no action is taken. Using cleaner fish can be an effective, drug-free treatment method, and ballan wrasse (Labrus bergylta) is a hardy wrasse species that displays cleaning behavior. With concerns about the overharvest of wild ballan wrasse, many companies farm this species, but the optimal ranges of a wide variety of rearing parameters are still unknown. This study investigated the effect of 6-week exposure to four dissolved oxygen (DO) levels (125%, 100%, 85%, and 75% DO saturation as the percentage of air) on ballan wrasse. Survival; growth (specific growth rate, SGR); condition factor (CF); and primary (cortisol), secondary (glucose, lactate, magnesium), and tertiary stress indicators (swimming performance) were investigated. There were no differences in SGR, CF, survival, or cortisol level among the groups at the end of the 6 weeks. There was variation in the magnitude of the cortisol response to an acute stressor at the end of the 6-week period, with the 75% DO treatment exhibiting a 3.3-fold increase in cortisol compared to a 5.2-fold increase in the control group (100%), which could suggest chronic stress. Relative critical swimming speed (RUcrit ) was measured to investigate swimming performance once all groups were returned to 100% DO saturation. The 75% RUcrit was lower than the 100% treatment (1.7 ± 0.18 body length [BL]/s compared to 2.5 ± 0.16 BL/s). Overall, these results suggest that DO levels of 75% trigger physiological changes and therefore may negatively affect welfare.

A Dynamic Water Channel Affects O2 Stability in [FeFe]-Hydrogenases

[FeFe]-hydrogenases are capable of reducing protons at a high rate. However, molecular oxygen (O2 ) induces the degradation of their catalytic cofactor, the H-cluster, which consists of a cubane [4Fe4S] subcluster (4FeH ) and a unique diiron moiety (2FeH ). Previous attempts to prevent O2 -induced damage have focused on enhancing the protein's sieving effect for O2 by blocking the hydrophobic gas channels that connect the protein surface and the 2FeH . In this study, we aimed to block an O2 diffusion pathway and shield 4FeH instead. Molecular dynamics (MD) simulations identified a novel water channel (WH ) surrounding the H-cluster. As this hydrophilic path may be accessible for O2 molecules we applied site-directed mutagenesis targeting amino acids along WH in proximity to 4FeH to block O2 diffusion. Protein film electrochemistry experiments demonstrate increased O2 stabilities for variants G302S and S357T, and MD simulations based on high-resolution crystal structures confirmed an enhanced local sieving effect for O2 in the environment of the 4FeH in both cases. The results strongly suggest that, in wild type proteins, O2 diffuses from the 4FeH to the 2FeH . These results reveal new strategies for improving the O2 stability of [FeFe]-hydrogenases by focusing on the O2 diffusion network near the active site.

Predicting Hypoxia Using Machine Learning: Systematic Review

Background

Hypoxia is an important risk factor and indicator for the declining health of inpatients. Predicting future hypoxic events using machine learning is a prospective area of study to facilitate time-critical interventions to counter patient health deterioration.

Objective

This systematic review aims to summarize and compare previous efforts to predict hypoxic events in the hospital setting using machine learning with respect to their methodology, predictive performance, and assessed population.

Methods

A systematic literature search was performed using Web of Science, Ovid with Embase and MEDLINE, and Google Scholar. Studies that investigated hypoxia or hypoxemia of hospitalized patients using machine learning models were considered. Risk of bias was assessed using the Prediction Model Risk of Bias Assessment Tool.

Results

After screening, a total of 12 papers were eligible for analysis, from which 32 models were extracted. The included studies showed a variety of population, methodology, and outcome definition. Comparability was further limited due to unclear or high risk of bias for most studies (10/12, 83%). The overall predictive performance ranged from moderate to high. Based on classification metrics, deep learning models performed similar to or outperformed conventional machine learning models within the same studies. Models using only prior peripheral oxygen saturation as a clinical variable showed better performance than models based on multiple variables, with most of these studies (2/3, 67%) using a long short-term memory algorithm.

Conclusions

Machine learning models provide the potential to accurately predict the occurrence of hypoxic events based on retrospective data. The heterogeneity of the studies and limited generalizability of their results highlight the need for further validation studies to assess their predictive performance.

The effect of intraoperative cerebral oxygen desaturations on postoperative cerebral oxygen metabolism in neonates and infants a pilot study

INTRODUCTION

Cerebral oxygen desaturation during pediatric surgery has been associated with adverse perioperative outcomes. The aim of this pilot study was to analyze the frequency and severity of intraoperative cerebral oxygen desaturations and their impact on postoperative cerebral oxygen metabolism in neonates and infants undergoing pediatric surgery.

METHODS

In a prospective pilot study, intra- and postoperative regional cerebral oxygen saturation and blood flow were measured noninvasively using a device combining laser Doppler flowmetry and white-light-spectrometry. Thirty-seven consecutive neonates and infants undergoing noncardiac surgery under general anesthesia for more than 30 min and necessity for invasive arterial blood pressure monitoring were included. Patients with pre-known congenital structural heart disease or cerebral disease were excluded. Continuously brain monitor recording was started in sedated patients before induction of anesthesia (preoperative baseline) and was completed 1 h postoperatively in the PICU in sedated, intubated, and mechanically ventilated states at the PICU (postoperative state). Baseline and postoperative state for cerebral fractional tissue oxygen extraction and approximated cerebral metabolic rate of oxygen were calculated.

RESULTS

Seventeen (46%) of the 37 studied neonates and infants suffered from intraoperative periods of regional cerebral oxygen desaturation below 20% of the baseline (event group). Severity of cerebral desaturations was median 4.0%min/h [range 0.1-58.7; interquartile range [IQR] 0.99-21.29]. In the event group, the duration of surgery was significantly longer (median 135 min [range 11-260; IQR 113.5-167.0] vs median 46.5 min [range 11-180; IQR 30.5-159.3]; difference of -62.94; 95% confidence interval [CI] -105.17 to -20.71; p = .021). In the event group, cerebral fractional tissue oxygen extraction (median 0.41 [range 0.20-0.55; IQR 0.26-0.44] vs. median 0.27 [range 0.11-0.41; IQR 0.20-0.31]; difference of -0.11; 95% CI -0.17 to -0.05; p = .001) and approximated cerebral metabolic rate of oxygen (median 6.15 arbitrary unit [range 2.69-12.07; IQR 5.12-7.21] vs. median 4.14 arbitrary unit [range 1.78-7.86; IQR 3.82-6.31]; difference of -1.76; 95% CI -3.03 to -0.49; p = .009) were significantly higher and the cerebral regional oxygen saturation (median 58.99% [range 44.87-79.1; IQR 54.26-72.61] vs median 70.94% [range 57.9-86.13; IQR 67.07-76.59]; difference of 10.01; 95% CI 4.13-15.90; p = .002) significantly lower after surgery compared to the nonevent group.

DISCUSSION

The increase of approximated cerebral metabolic rate of oxygen could indicate an elevated oxidative energy metabolism in the "stressed" brain, due to repair processes. The increased cerebral fractional tissue oxygen extraction fits with the decreased NIRS cerebral oxygenation. Our data suggest that an increase in cerebral oxygen metabolism was the cause.

CONCLUSION

Cerebral oxygen desaturation during major surgery in neonates and infants is associated with early postoperative increased cerebral oxygen extraction and possibly increased cerebral oxygen metabolism.

Heme-based oxygen gasoreceptors

To investigate gasocrine signaling, there is a critical need to identify gasoreceptors for the essential gasotransmitters like O2. Based on existing scientific literature, I propose that heme-based O2 sensors, featuring diverse signaling domains across genera, should be explicitly designated as O2 gasoreceptors. Acknowledging that O2 gasoreceptors are likely to belong to multiple protein classes with diverse signaling domains and pathways will facilitate a comprehensive search for O2 gasoreceptors in all organisms and across every cell type. This approach will broaden the investigation beyond specialized tissues or cells, encompassing a systemic exploration.