The Hyperoxic-Hypoxic Paradox

Laboratory medicine and sports: where are we now?

Laboratory medicine in sport and exercise has significantly developed during the last decades with the awareness that physical activity contributes to improved health status, and is present in monitoring both professional and recreational athletes. Training and competitions can modify concentrations of a variety of laboratory parameters, so the accurate laboratory data interpretation includes controlled and known preanalytical and analytical variables to prevent misleading interpretations. The paper represents a comprehensive summary of the lectures presented during the 35th Annual Symposium of the Croatian Society of Medical Biochemistry and Laboratory Medicine. It describes management of frequent sport injuries and sums up current knowledge of selected areas in laboratory medicine and sports including biological variation, changes in biochemical parameters and glycemic status. Additionally, the paper polemicizes sex hormone disorders in sports, encourages and comments research in recreational sports and laboratory medicine. In order to give the wider view, the connection of legal training protocols as well as monitoring prohibited substances in training is also considered through the eyes of laboratory medicine.

Mild hyperbaric oxygen exposure protects heart during ischemia/reperfusion and affects vascular relaxation

Mild hyperbaric oxygen therapy (mHBOT) is an adjuvant therapy used in conditions where tissue oxygenation is reduced and is implemented using pressures less than 1.5 ATA and 100% O2 (instead of the classical HBOT at 1.9-3 ATA) which results in cheaper, easier to implement, and equally effective. mHBOT is offered for wellness and beauty and as an anti-aging strategy, in spite of the absence of studies on the cardiovascular system. Consequently, we investigated the impact of mHBOT on the cardiovascular system. Mechanical and energetic parameters of isolated heart submitted to ischemia/reperfusion injury and arterial contractile response from mHBOT-exposed rats were evaluated. In the heart, mHBOT increased pre-ischemic velocity of contraction and ischemic end-diastolic pressure and developed pressure and contractile economy during reperfusion. mHBOT decreased infarct size and increased the plasma nitrite levels. In the artery, mHBOT increased acetylcholine sensitivity. mHBOT protects the heart during ischemia/reperfusion and affects vascular relaxation.

Physiological skin oxygen levels: An important criterion for skin cell functionality and therapeutic approaches

The skin is made up of different layers with various gradients, which maintain a complex microenvironment, particularly in terms of oxygen levels. However, all types of skin cells are cultured in conventional incubators that do not reproduce physiological oxygen levels. Instead, they are cultured at atmospheric oxygen levels, a condition that is far removed from physiology and may lead to the generation of free radicals known to induce skin ageing. This review aims to summarize the current literature on the effect of physiological oxygen levels on skin cells, highlight the shortcomings of current in vitro models, and demonstrate the importance of respecting skin oxygen levels. We begin by clarifying the terminology used about oxygen levels and describe the specific distribution of oxygen in the skin. We review and discuss how skin cells adapt their oxygen consumption and metabolism to oxygen levels environment, as well as the changes that are induced, particularly, their redox state, life cycle and functions. We examine the effects of oxygen on both simple culture models and more complex reconstructed skin models. Finally, we present the implications of oxygen modulation for a more therapeutic approach.

Research progress on high-concentration oxygen therapy after cerebral hemorrhage

Recently, the role of high-concentration oxygen therapy in cerebral hemorrhage has been extensively discussed. This review describes the research progress in high-concentration oxygen therapy after cerebral hemorrhage. High-concentration oxygen therapy can be classified into two treatment methods: hyperbaric and normobaric high-concentration oxygen therapy. Several studies have reported that high-concentration oxygen therapy uses the pathological mechanisms of secondary ischemia and hypoxia after cerebral hemorrhage as an entry point to improve cerebral oxygenation, metabolic rate, cerebral edema, intracranial pressure, and oxidative stress. We also elucidate the mechanisms by which molecules such as Hypoxia-inducible factor 1-alpha (HIF-1α), vascular endothelial growth factor, and erythropoietin (EPO) may play a role in oxygen therapy. Although people are concerned about the toxicity of hyperoxia, combined with relevant literature, the evidence discussed in this article suggests that as long as the duration, concentration, pressure, and treatment interval of patients with cerebral hemorrhage are properly understood and oxygen is administered within the treatment window, it can be effective to avoid hyperoxic oxygen toxicity. Combined with the latest research, we believe that high-concentration oxygen therapy plays an important positive role in injuries and outcomes after cerebral hemorrhage, and we recommend expanding the use of normal-pressure high-concentration oxygen therapy for cerebral hemorrhage.

Physical enhancement of older adults using hyperbaric oxygen: a randomized controlled trial

INTRODUCTION

Aging is associated with a progressive decline in the capacity for physical activity. The objective of the current study was to evaluate the effect of an intermittent hyperbaric oxygen therapy (HBOT) protocol on maximal physical performance and cardiac perfusion in sedentary older adults.

METHODS

A randomized controlled clinical trial randomized 63 adults (> 64yrs) either to HBOT (n = 30) or control arms (n = 33) for three months. Primary endpoint included the maximal oxygen consumption (VO2Max) and VO2Max/Kg, on an E100 cycle ergometer. Secondary endpoints included cardiac perfusion, evaluated by magnetic resonance imaging and pulmonary function. The HBOT protocol comprised of 60 sessions administered on a daily basis, for 12 consecutive weeks, breathing 100% oxygen at 2 absolute atmospheres (ATA) for 90 min with 5-minute air breaks every 20 min.

RESULTS

Following HBOT, improvements were observed in VO2Max/kg, with a significant increase of 1.91 ± 3.29 ml/kg/min indicated by a net effect size of 0.455 (p = 0.0034). Additionally, oxygen consumption measured at the first ventilatory threshold (VO2VT1) showed a significant increase by 160.03 ± 155.35 ml/min (p < 0.001) with a net effect size of 0.617. Furthermore, both cardiac blood flow (MBF) and cardiac blood volume (MBV) exhibited significant increases when compared to the control group. The net effect size for MBF was large at 0.797 (p = 0.008), while the net effect size for MBV was even larger at 0.896 (p = 0.009).

CONCLUSION

The findings of the study indicate that HBOT has the potential to improve physical performance in aging adults. The enhancements observed encompass improvements in key factors including VO2Max, and VO2VT1. An important mechanism contributing to these improvements is the heightened cardiac perfusion induced by HBOT.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier NCT02790541 (registration date 06/06/2016).

Hyperbaric Oxygen Therapy to Minimize Orthodontic Relapse in Rabbits

OBJECTIVES

 The purpose of the present study was to discover how hyperbaric oxygen therapy (HBOT) could reduce orthodontic relapse by altering the expressions of hypoxia-inducible factor (HIF)-1 messenger ribonucleic acid (mRNA), type I collagen (Col I), and matrix metalloproteinase-1 (MMP-1) in the gingival supracrestal fibers in rabbits.

MATERIALS AND METHODS

 This study involved 44 male rabbits (Oryctolagus cuniculus) randomly divided into the normal group (K0), the orthodontic group without HBOT (K1), and the orthodontic group with HBOT (K2). Following orthodontic separation of the two upper central incisors, a retention phase and relapse assessment were performed. The HBOT was performed for a period of 2, 4, 6, 8, and 10 days after retention. HIF-1α transcription was assessed employing real-time polymerase chain reaction, whereas Col I and MMP-1 proteins were examined using immunohistochemistry. The orthodontic relapse was measured clinically using a digital caliper.

STATISTICAL ANALYSIS

 We used the one-way analysis of variance followed by Tukey's post hoc for multiple comparisons to measure differences between pairs of means; a p-value of 0.05 was considered statistically significant.

RESULTS

 HBOT significantly increased the HIF-1α mRNA expression (p = 0.0140), increased Col I (p = 0.0043) and MMP-1 (p = 0.0068) on the tensioned and pressured side of the gingival supracrestal fibers, respectively, and clinically decreased the relapse (p = 3.75 × 10-40).

CONCLUSION

 HBOT minimizes orthodontic relapse by influencing HIF-1α expression, collagen synthesis (Col I), and degradation (MMP-1). This result suggests that HBOT has the potential to be used as an adjunctive method in the orthodontic retention phase.

Role of Hyperbaric Oxygen in Filler-Induced Vascular Occlusion

INTRODUCTION

The rising incidence of filler-induced vascular complications in the context of aesthetic procedures necessitates a thorough assessment of therapeutic options. Hyperbaric oxygen therapy (HBOT) has emerged as a potential intervention for filler-induced vascular occlusion (FIVO), although optimal dosing and timing remain undefined.

METHODS

This review explores the pathophysiology of FIVO and elucidates HBOT's multifaceted role in salvaging ischemic tissue. The physical and biochemical mechanisms of HBOT, including its vasodilatory, anti-spasmodic, and anti-inflammatory effects, are examined.

RESULTS

HBOT serves as an adjunctive therapy in FIVO management, emphasizing timely intervention, adherence to specific pressures (two atmosphere absolute), and session durations (60 minutes) to optimize efficacy and minimize complications. While existing HBOT protocols for compromised grafts provide insights, standardized guidelines for FIVO are lacking.

CONCLUSION

HBOT enhances tissue oxygenation, modulates reactive oxygen species, and influences angiogenesis and hypoxia response. However, it does not replace key treatment protocols for filler vascular complications. Further research and standardized protocols are warranted to define HBOT's definitive role in mitigating filler-induced vascular complications. Level of Evidence IV This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Hyperbaric Oxygenation: Can It Be a Novel Supportive Method in Acute Kidney Injury? Data Obtained from Experimental Studies

Despite constant achievements in treatment, acute kidney injury (AKI) remains a significant public health problem and a cause of mortality in the human population. In developed countries, AKI is a significant and frequent hospital complication, especially among patients admitted to intensive care units, where mortality rates can reach up to 50%. In addition, AKI has been implicated as an independent risk factor for the development of chronic kidney disease. Hyperbaric oxygenation (HBO) has been used as a primary or adjunctive therapy for the past 50 years, both in experimental and clinical studies. HBO is a treatment in which the patient is occasionally exposed to 100% oxygen at a pressure greater than atmospheric pressure at sea level. However, despite decades of extensive research, the potentially beneficial effects of this therapeutic approach are still not fully understood, although many potential mechanisms have been proposed, such as antioxidative, anti-inflammatory, anti-apoptotic, etc. Furthermore, the low cost and insignificant adverse events make HBO a potentially important strategy in the prevention and treatment of different diseases. Considering all of this, this review highlights the potential role of HBO in maintaining cellular homeostasis disrupted due to AKI, caused in different experimental models.

Mitochondrial DNA mutations in extremely preterm infants with bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a serious chronic lung disease affecting extremely preterm infants. While mitochondrial dysfunction has been investigated in various medical conditions, limited research has explored mitochondrial DNA (mtDNA) gene mutations, specifically in BPD. This study aimed to evaluate mitochondrial mtDNA gene mutations in extremely preterm infants with BPD. In this prospective observational study, we enrolled a cohort of extremely preterm infants diagnosed with BPD. Clinical data were collected to provide comprehensive patient profiles. Peripheral blood mononuclear cells were isolated from whole-blood samples obtained within a defined timeframe. Subsequently, mtDNA extraction and sequencing using next-generation sequencing technology were performed to identify mtDNA gene mutations. Among the cohort of ten extremely preterm infants with BPD, mtDNA sequencing revealed the presence of mutations in seven patients, resulting in a total of twenty-one point mutations. Notably, many of these mutations were identified in loci associated with critical components of the respiratory chain complexes, vital for proper mitochondrial function and cellular energy production. This pilot study provides evidence of mtDNA point mutations in a subset of extremely preterm infants with BPD. These findings suggest a potential association between mitochondrial dysfunction and the pathogenesis of BPD. Further extensive investigations are warranted to unravel the mechanisms underlying mtDNA mutations in BPD.

Hyperbaric Oxygen Therapy as an Alternative Therapeutic Option for Radiation-Induced Necrosis Following Radiotherapy for Intracranial Pathologies

BACKGROUND

Radiotherapy (RT) is a feasible adjuvant therapeutic option for managing intracranial pathologies. One of the late complications of RT that frequently develops within months following RT is radiation necrosis (RN). Corticosteroids are the first-line therapeutic option for RNs; however, in case of unfavorable outcomes or intolerability, several other options, including bevacizumab, laser interstitial thermal therapy, surgery, and hyperbaric oxygen therapy (HBOT). Our goal was to investigate the feasibility and efficacy of the application of HBOT in RNs following RT and help physicians make decisions based on the latest data in the literature.

METHODS

We provide a comprehensive review of the literature on the current issues of utilization of HBOT in RNs.

RESULTS

We included 11 studies with a total of 46 patients who underwent HBOT. Most of the cases were diagnosed with brain tumors or arteriovenous malformations. Improvement was achieved in most of the cases.

DISCUSSION

HBOT is a noninvasive therapeutic intervention that can play a role in adjuvant therapy concurrent with RT and chemotherapy and treating RNs. HBOT resolves the RN through 3 mechanisms, including angiogenesis, anti-inflammatory modulation, and cellular repair. Previous studies demonstrated that HBOT is a feasible and well-tolerated therapeutic option that has shown promising results in improving clinical and radiological outcomes in intracranial RNs. Complications of HBOT are usually mild and reversible.

CONCLUSIONS

HBOT is a feasible and effective therapeutic option in steroid-refractory RNs and is associated with favorable outcomes and a low rate of side effects.

Hyperbaric oxygen therapy vs. pharmacological intervention in adults with fibromyalgia related to childhood sexual abuse: prospective, randomized clinical trial

Fibromyalgia syndrome (FMS) is a chronic pain syndrome characterized by disruptions in pain processing within the central nervous system. It exhibits a high prevalence among patients with a history of traumatic experiences, notably childhood sexual abuse (CSA). This study compared the efficacy of hyperbaric oxygen therapy (HBOT) to the current pharmacological standard of care for individuals suffering from CSA-related FMS. Forty-eight participants diagnosed with FMS and a history of CSA were randomly assigned to either the HBOT group (60 sessions of 100% oxygen at 2 ATA for 90 min, with air breaks every 5 min) or the medication (MED) group (FDA-approved medications, Pregabalin and Duloxetine). The primary endpoint was the Fibromyalgia impact questionnaire (FIQ) score, while secondary endpoints encompassed emotional status and daily functioning questionnaires, as well as pain thresholds and conditioned pain modulation tests. Brain activity was evaluated through single photon emission computed tomography (SPECT). Results revealed a significant group-by-time interaction for the FIQ score favoring HBOT over MED (p < 0.001), with a large effect size (Cohen's d = - 1.27). Similar findings were observed in emotional symptoms and functional measures. SPECT imaging demonstrated an increase in activity in pre-frontal and temporal brain areas, which correlated with symptoms improvement. In conclusion, HBOT exhibited superior benefits over medications in terms of physical, functional, and emotional improvements among FMS patients with a history of CSA. This associated with increased activity in pre-frontal and temporal brain areas, highlighting the neuroplasticity effect of HBOT.

Hyperbaric oxygen therapy: future prospects in regenerative therapy and anti-aging

Hyperbaric Oxygen Therapy (HBOT) utilizes 100% oxygen at high atmospheric pressure for clinical applications. HBOT has proven to be an effective supplementary treatment for a variety of clinical and pathological disorders. HBOT's therapeutic results are based on the physiological effects of increased tissue oxygenation, or improved oxygen bioavailability. HBOT's current indications in illnesses like as wound healing, thermal or radiation burns, and tissue necrosis point to its function in facilitating the regeneration process. Various research has revealed that HBOT plays a function in vascularization, angiogenesis, and collagen production augmentation. Individual regeneration capacity is influenced by both environmental and genetic factors. Furthermore, the regenerating ability of different types of tissues varies, and this ability declines with age. HBOT affects physiological processes at the genetic level by altering gene expression, delaying cell senescence, and assisting in telomere length enhancement. The positive results in a variety of indications, ranging from tissue regeneration to better cognitive function, indicate that it has enormous potential in regenerative and anti-aging therapy.

Hyperoxia and brain: the link between necessity and injury from a molecular perspective

Oxygen (O2) supplementation is commonly used to treat hypoxia in patients with respiratory failure. However, indiscriminate use can lead to hyperoxia, a condition detrimental to living tissues, particularly the brain. The brain is sensitive to reactive oxygen species (ROS) and inflammation caused by high concentrations of O2, which can result in brain damage and mitochondrial dysfunction, common features of neurodegenerative disorders. Hyperoxia leads to increased production of ROS, causing oxidative stress, an imbalance between oxidants and antioxidants, which can damage tissues. The brain is particularly vulnerable to oxidative stress due to its lipid composition, high O2 consumption rate, and low levels of antioxidant enzymes. Moreover, hyperoxia can cause vasoconstriction and decreased O2 supply to the brain, posing a challenge to redox balance and neurodegenerative processes. Studies have shown that the severity of hyperoxia-induced brain damage varies with inspired O2 concentration and duration of exposure. Therefore, careful evaluation of the balance between benefits and risks of O2 supplementation, especially in clinical settings, is crucial.

Hyperbaric Oxygen Reduces Oxidative Stress Impairment and DNA Damage and Simultaneously Increases HIF-1α in Ischemia-Reperfusion Acute Kidney Injury

The central exacerbating factor in the pathophysiology of ischemic-reperfusion acute kidney injury (AKI) is oxidative stress. Lipid peroxidation and DNA damage in ischemia are accompanied by the formation of 3-nitrotyrosine, a biomarker for oxidative damage. DNA double-strand breaks (DSBs) may also be a result of postischemic AKI. γH2AX(S139) histone has been identified as a potentially useful biomarker of DNA DSBs. On the other hand, hypoxia-inducible factor (HIF) is the "master switch" for hypoxic adaptation in cells and tissues. The aim of this research was to evaluate the influence of hyperbaric oxygen (HBO) preconditioning on antioxidant capacity estimated by FRAP (ferric reducing antioxidant power) and ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) assay, as well as on oxidative stress parameter 3-nitrotyrosine, and to assess its effects on γH2AX(S139), HIF-1α, and nuclear factor-κB (NF-κB) expression, in an experimental model of postischemic AKI induced in spontaneously hypertensive rats. The animals were divided randomly into three experimental groups: sham-operated rats (SHAM, n = 6), rats with induced postischemic AKI (AKI, n = 6), and group exposed to HBO preconditioning before AKI induction (AKI + HBO, n = 6). A significant improvement in the estimated glomerular filtration rate, eGFR, in AKI + HBO group (p < 0.05 vs. AKI group) was accompanied with a significant increase in plasma antioxidant capacity estimated by FRAP (p < 0.05 vs. SHAM group) and a reduced immunohistochemical expression of 3-nitrotyrosine and γH2AX(S139). Also, HBO pretreatment significantly increased HIF-1α expression (p < 0.001 vs. AKI group), estimated by Western blot and immunohistochemical analysis in kidney tissue, and decreased immunohistochemical NF-κB renal expression (p < 0.01). Taking all of these results together, we may conclude that HBO preconditioning has beneficial effects on acute kidney injury induced in spontaneously hypertensive rats.

COVID-19 and abnormal uterine bleeding: potential associations and mechanisms

The impact of COVID-19 on menstruation has received a high level of public and media interest. Despite this, uncertainty exists about the advice that women and people who menstruate should receive in relation to the expected impact of SARS-CoV-2 infection, long COVID or COVID-19 vaccination on menstruation. Furthermore, the mechanisms leading to these reported menstrual changes are poorly understood. This review evaluates the published literature on COVID-19 and its impact on menstrual bleeding, discussing the strengths and limitations of these studies. We present evidence consistent with SARS-CoV-2 infection and long COVID having an association with changes in menstrual bleeding parameters and that the impact of COVID vaccination on menstruation appears less significant. An overview of menstrual physiology and known causes of abnormal uterine bleeding (AUB) is provided before discussing potential mechanisms which may underpin the menstrual disturbance reported with COVID-19, highlighting areas for future scientific study. Finally, consideration is given to the effect that menstruation may have on COVID-19, including the impact of the ovarian sex hormones on acute COVID-19 severity and susceptibility and reported variation in long COVID symptoms across the menstrual cycle. Understanding the current evidence and addressing gaps in our knowledge in this area are essential to inform public health policy, direct the treatment of menstrual disturbance and facilitate development of new therapies, which may reduce the severity of COVID-19 and improve quality of life for those experiencing long COVID.

Long term outcomes of hyperbaric oxygen therapy in post covid condition: longitudinal follow-up of a randomized controlled trial

In our previous randomized controlled trial, we documented significant improvements in cognitive, psychiatric, fatigue, sleep, and pain symptoms among long Coronavirus disease 2019 (COVID) patients who underwent hyperbaric oxygen therapy (HBOT). The primary objective of the present study was to evaluate the enduring 1 year long term effects of HBOT on long COVID syndrome. This longitudinal long-term follow-up included 31 patients with reported post COVID-19 cognitive symptoms, who underwent 40 daily sessions of HBOT. Participants were recruited more than one year (486 ± 73) after completion of the last HBOT session. Quality of life, assessed using the short form-36 (SF-36) questionnaire revealed, that the long-term results exhibited a similar magnitude of improvement as the short-term outcomes following HBOT across most domains. Regarding sleep quality, improvements were observed in global score and across five sleep domains with effect sizes of moderate magnitude during the short-term evaluation, and these improvements persisted in the long-term assessment (effect size (ES1) = 0.47-0.79). In the realm of neuropsychiatric symptoms, as evaluated by the brief symptom inventory-18 (BSI-18), the short-term assessment following HBOT demonstrated a large effect size, and this effect persisted at the long-term evaluation. Both pain severity (ES1 = 0.69) and pain interference (ES1 = 0.83), had significant improvements during the short-term assessment post HBOT, which persisted at long term. The results indicate HBOT can improve the quality of life, quality of sleep, psychiatric and pain symptoms of patients suffering from long COVID. The clinical improvements gained by HBOT are persistent even 1 year after the last HBOT session.

Enriched oxygen improves age-related cognitive impairment through enhancing autophagy

Age-related cognitive impairment represents a significant health concern, with the understanding of its underlying mechanisms and potential interventions being of paramount importance. This study aimed to investigate the effects of hyperbaric oxygen therapy (HBOT) on cognitive function and neuronal integrity in aged (22-month-old) C57BL/6 mice. Male mice were exposed to HBOT for 2 weeks, and spatial learning and memory abilities were assessed using the Morris water maze. We employed transcriptome sequencing and Gene Ontology (GO) term enrichment analysis to examine the effects of HBOT on gene expression profiles, with particular attention given to synapse-related genes. Our data indicated a significant upregulation of postsynapse organization, synapse organization, and axonogenesis GO terms, likely contributing to improved cognitive performance. Moreover, the hyperphosphorylation of tau, a hallmark of many neurodegenerative diseases, was significantly reduced in the HBO-treated group, both in vivo and in vitro. Transmission electron microscopy revealed significant ultrastructural alterations in the hippocampus of the HBOT group, including an increase in the number of synapses and the size of the active zone, a reduction in demyelinated lesions, and a decreased number of "PANTHOS." Furthermore, Western blot analyses confirmed the upregulation of PSD95, BDNF, and Syn proteins, suggesting enhanced synaptic plasticity and neurotrophic support. Moreover, HBOT increased autophagy, as evidenced by the elevated levels of Beclin-1 and LC3 proteins and the reduced level of p62 protein. Finally, we demonstrated that HBOT activated the AMPK-mTOR signaling pathway, a critical regulator of autophagy. Notably, our findings provide novel insights into the mechanisms by which HBOT ameliorates age-related cognitive impairment, suggesting the potential therapeutic value of this approach.

Hyperoxia: Effective Mechanism of Hyperbaric Treatment at Mild-Pressure

HBOT increases the proportion of dissolved oxygen in the blood, generating hyperoxia. This increased oxygen diffuses into the mitochondria, which consume the majority of inhaled oxygen and constitute the epicenter of HBOT effects. In this way, the oxygen entering the mitochondria can reverse tissue hypoxia, activating the electron transport chain to generate energy. Furthermore, intermittent HBOT is sensed by the cell as relative hypoxia, inducing cellular responses such as the activation of the HIF-1α pathway, which in turn, activates numerous cellular processes, including angiogenesis and inflammation, among others. These effects are harnessed for the treatment of various pathologies. This review summarizes the evidence indicating that the use of medium-pressure HBOT generates hyperoxia and activates cellular pathways capable of producing the mentioned effects. The possibility of using medium-pressure HBOT as a direct or adjunctive treatment in different pathologies may yield benefits, potentially leading to transformative therapeutic advancements in the future.

Recent Advancement in Elimination Strategies and Potential Rejuvenation Targets of Senescence

Cellular senescence is a state of exiting the cell cycle, resisting apoptosis, and changing phenotype. Senescent cells (SCs) can be identified by large, distorted morphology and irreversible inability to replicate. In early development, senescence has beneficial roles like tissue patterning and wound healing, where SCs are cleared by the immune system. However, there is a steep rise in SC number as organisms age. The issue with SC accumulation stems from the loss of cellular function, alterations of the microenvironment, and secretions of pro-inflammatory molecules, consisting of cytokines, chemokines, matrix metalloproteinases (MMPs), interleukins, and extracellular matrix (ECM)-associated molecules. This secreted cocktail is referred to as the senescence-associated secretory phenotype (SASP), a hallmark of cellular senescence. The SASP promotes inflammation and displays a bystander effect where paracrine signaling turns proliferating cells into senescent states. To alleviate age-associated diseases, researchers have developed novel methods and techniques to selectively eliminate SCs in aged individuals. Although studies demonstrated that selectively killing SCs improves age-related disorders, there are drawbacks to SC removal. Considering favorable aspects of senescence in the body, this paper reviews recent advancements in elimination strategies and potential rejuvenation targets of senescence to bring researchers in the field up to date.

Hyperoxic-hypoxic Paradox: Breast Cancer Microenvironment and an Innovative Treatment Strategy

A small therapeutic range of oxygen is required for effective metabolism. As a result, hypoxia (low oxygen concentration) is one of the most potent inducers of gene expression, metabolic alterations, and regenerative processes, such as angiogenesis, stem cell proliferation, migration, and differentiation. The cellular response is controlled by sensing the increased oxygen levels (hyperoxia) or hypoxia via specific chemoreceptor cells. Surprisingly, changes in free oxygen concentration instead of absolute oxygen levels may be regarded as a deficiency of oxygen at the cellular level. Recurrent intermittent hyperoxia may trigger many mediators of cellular pathways typically generated during hypoxia. The dilemma of hyperoxic-hypoxic conditions is known as the hyperoxic-hypoxic paradox. According to the latest data, the hypoxic microenvironment, crucial during cancer formation, has been demonstrated to play a key role in regulating breast cancer growth and metastasis. Hypoxic circumstances cause breast cancer cells to respond in a variety of ways. Transcription factors are identified as hypoxia-inducible factors (HIFs) that have been suggested to be a factor in the pathobiology of breast cancer and a possible therapeutic target, driving the cellular response to hypoxia. Breast cancer has a dismal prognosis due to a high level of resistance to practically all well-known cancer management that has been related to hypoxia-based interactions between tumor cells and the stromal milieu. We attempt to review the enigma by exploring the starring roles of HIFs in breast cancer, the HIF paradox, and the hyperoxic-hypoxic enigma.

Comparing the Blood Response to Hyperbaric Oxygen with High-Intensity Interval Training-A Crossover Study in Healthy Volunteers

High-intensity interval training (HIIT) and hyperbaric oxygen therapy (HBOT) induce reactive oxygen species (ROS) formation and have immunomodulatory effects. The lack of readily available biomarkers for assessing the dose-response relationship is a challenge in the clinical use of HBOT, motivating this feasibility study to evaluate the methods and variability. The overall hypothesis was that a short session of hyperbaric oxygen (HBO2) would have measurable effects on immune cells in the same physiological range as shown in HIIT; and that the individual response to these interventions can be monitored in venous blood and/or peripheral blood mononuclear cells (PBMCs). Ten healthy volunteers performed two interventions; a 28 min HIIT session and 28 min HBO2 in a crossover design. We evaluated bulk RNA sequencing data from PBMCs, with a separate analysis of mRNA and microRNA. Blood gases, peripheral venous oxygen saturation (SpvO2), and ROS levels were measured in peripheral venous blood. We observed an overlap in the gene expression changes in 166 genes in response to HIIT and HBO2, mostly involved in hypoxic or inflammatory pathways. Both interventions were followed by downregulation of several NF-κB signaling genes in response to both HBO2 and HIIT, while several interferon α/γ signaling genes were upregulated. Only 12 microRNA were significantly changed in HBO2 and 6 in HIIT, without overlap between interventions. ROS levels were elevated in blood at 30 min and 60 min compared to the baseline during HIIT, but not during/after HBO2. In conclusion, HBOT changed the gene expression in a number of pathways measurable in PBMC. The correlation of these changes with the dose and individual response to treatment warrants further investigation.

Key pathways and genes that are altered during treatment with hyperbaric oxygen in patients with sepsis due to necrotizing soft tissue infection (HBOmic study)

BACKGROUND

For decades, the basic treatment strategies of necrotizing soft tissue infections (NSTI) have remained unchanged, primarily relying on aggressive surgical removal of infected tissue, broad-spectrum antibiotics, and supportive intensive care. One treatment strategy that has been proposed as an adjunctive measure to improve patient outcomes is hyperbaric oxygen (HBO2) treatment. HBO2 treatment has been linked to several immune modulatory effects; however, investigating these effects is complicated due to the disease's acute life-threatening nature, metabolic and cell homeostasis dependent variability in treatment effects, and heterogeneity with respect to both patient characteristics and involved pathogens. To embrace this complexity, we aimed to explore the underlying biological mechanisms of HBO2 treatment in patients with NSTI on the gene expression level.

METHODS

We conducted an observational cohort study on prospective collected data, including 85 patients admitted to the intensive care unit (ICU) for NSTI. All patients were treated with one or two HBO2 treatments and had one blood sample taken before and after the intervention. Total RNAs from blood samples were extracted and mRNA purified with rRNA depletion, followed by whole-transcriptome RNA sequencing with a targeted sequencing depth of 20 million reads. A model for differentially expressed genes (DEGs) was fitted, and the functional aspects of the obtained set of genes was predicted with GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of genes and Genomes) enrichment analyses. All analyses were corrected for multiple testing with FDR.

RESULTS

After sequential steps of quality control, a final of 160 biological replicates were included in the present study. We found 394 protein coding genes that were significantly DEGs between the two conditions with FDR < 0.01, of which 205 were upregulated and 189 were downregulated. The enrichment analysis of these DEGs revealed 20 GO terms in biological processes and 12 KEGG pathways that were significantly overrepresented in the upregulated DEGs, of which the term; "adaptive immune response" (GO:0002250) (FDR = 9.88E-13) and "T cell receptor signaling pathway" (hsa04660) (FDR = 1.20E-07) were the most significant. Among the downregulated DEGs two biological processes were significantly enriched, of which the GO term "apoptotic process" (GO:0006915) was the most significant (FDR = 0.001), followed by "Positive regulation of T helper 1 cell cytokine production" (GO:2000556), and "NF-kappa B signaling pathway" (hsa04064) was the only KEGG pathway that was significantly overrepresented (FDR = 0.001).

CONCLUSIONS

When one or two sessions of HBO2 treatment were administered to patients with a dysregulated immune response and systemic inflammation due to NSTI, the important genes that were regulated during the intervention were involved in activation of T helper cells and downregulation of the disease-induced highly inflammatory pathway NF-κB, which was associated with a decrease in the mRNA level of pro-inflammatory factors.

TRIAL REGISTRATION

Biological material was collected during the INFECT study, registered at ClinicalTrials.gov (NCT01790698).

Onge P, McDonald SM, Hecocks D, Wittels SH. Continuous Physiological Monitoring of the Combined Exposure to Hypoxia and High Cognitive Load in Military Personnel

Military aviators endure high cognitive loads and hypoxic environments during flight operations, impacting the autonomic nervous system (ANS). The synergistic effects of these exposures on the ANS, however, are less clear. This study investigated the simultaneous effects of mild hypoxia and high cognitive load on the ANS in military personnel. This study employed a two-factor experimental design. Twenty-four healthy participants aged between 19 and 45 years were exposed to mild hypoxia (14.0% O2), normoxia (21.0% O2), and hyperoxia (33.0% O2). During each epoch (n = 5), participants continuously performed one 15 min and one 10 min series of simulated, in-flight tasks separated by 1 min of rest. Exposure sequences (hypoxia-normoxia and normoxia-hyperoxia) were separated by a 60 min break. Heart rate (HR), heart rate variability (HRV), and O2 saturation (SpO2) were continuously measured via an armband monitor (Warfighter MonitorTM, Tiger Tech Solutions, Inc., Miami, FL, USA). Paired and independent t-tests were used to evaluate differences in HR, HRV, and SpO2 within and between exposure sequences. Survival analyses were performed to assess the timing and magnitude of the ANS responses. Sympathetic nervous system (SNS) activity during hypoxia was highest in epoch 1 (HR: +6.9 bpm, p = 0.002; rMSSD: -9.7 ms, p = 0.003; SDNN: -11.3 ms, p = 0.003; SpO2: -8.4%, p < 0.0000) and appeared to slightly decline with non-significant increases in HRV. During normoxia, SNS activity was heightened, albeit non-significantly, in epoch 1, with higher HR (68.5 bpm vs. 73.0 bpm, p = 0.06), lower HRV (rMSSD: 45.1 ms vs. 38.7 ms, p = 0.09 and SDNN: 52.5 ms vs. 45.1 ms, p = 0.08), and lower SpO2 (-0.7% p = 0.05). In epochs 2-4, HR, HRV, and SpO2 trended towards baseline values. Significant between-group differences in HR, HRV, and O2 saturation were observed. Hypoxia elicited significantly greater HRs (+5.0, p = 0.03), lower rMSSD (-7.1, p = 0.03), lower SDNN (-8.2, p = 0.03), and lower SpO2 (-1.4%, p = 0.002) compared to normoxia. Hyperoxia appeared to augment the parasympathetic reactivation reflected by significantly lower HR, in addition to higher HRV and O2 relative to normoxia. Hypoxia induced a greater ANS response in military personnel during the simultaneous exposure to high cognitive load. The significant and differential ANS responses to varying O2 levels and high cognitive load observed highlight the importance of continuously monitoring multiple physiological parameters during flight operations.

Hyperbaric oxygen therapy exerts anti-osteoporotic effects in obese and lean D-galactose-induced aged rats

Obesity accelerates the aging processes, resulting in an aggravation of aging-induced osteoporosis. We investigated the anti-osteoporotic effect of hyperbaric oxygen therapy (HBOT) in obese- and lean-aged rats through measurement of cellular senescence, hypoxia, inflammation, antioxidants, and bone microarchitecture. Obese and lean male Wistar rats were injected with 150 mg/kg/day of D-galactose for 8 weeks to induce aging. Then, all rats were randomly given either sham or HBOT for 14 days. Metabolic parameters were determined. Expression by bone mRNA for cellular senescence, hypoxia, inflammation, antioxidative capacity, and bone remodeling were examined. Micro-computed tomography and atomic absorption spectroscopy were performed to evaluate bone microarchitecture and bone mineral profiles, respectively. We found that HBOT restored the alterations in the mRNA expression level of p16, p21, HIF-1α, TNF-α, IL-6, RANKL, RANK, NFATc1, DC-STAMP, Osx, ALP, and Col1a1 in the bone in obese-and lean- aging rats. In obese-aging rats, HBOT increased the level of expression of Sirt1 and CuZnSOD mRNA and diminished the expression level of HIF-2α and ctsk mRNA to the same levels as the control group. However, HBOT failed to alter catalase and OCN mRNA expression in obese-aged rats. HBOT partially improved the bone microarchitecture in obese-aged rats, but completely restored it in lean-aged rats. Interestingly, HBOT protected against obesity-induced demineralization in obese-aged rats. In summary, HBOT exerts an anti-osteoporotic effect in lean-aged rats and prevents some, but not all the negative effects of obese-aged conditions on bone health. Therefore, HBOT is considered as a potential therapy for aging-induced osteoporosis, regardless of obese status.

The use of hyperbaric oxygen for veterans with PTSD: basic physiology and current available clinical data

Post-traumatic stress disorder (PTSD) affects up to 30% of veterans returning from the combat zone. Unfortunately, a substantial proportion of them do not remit with the current available treatments and thus continue to experience long-term social, behavioral, and occupational dysfunction. Accumulating data implies that the long-standing unremitting symptoms are related to changes in brain activity and structure, mainly disruption in the frontolimbic circuit. Hence, repair of brain structure and restoration of function could be a potential aim of effective treatment. Hyperbaric oxygen therapy (HBOT) has been effective in treating disruptions of brain structure and functions such as stroke, traumatic brain injury, and fibromyalgia even years after the acute insult. These favorable HBOT brain effects may be related to recent protocols that emphasize frequent fluctuations in oxygen concentrations, which in turn contribute to gene expression alterations and metabolic changes that induce neuronal stem cell proliferation, mitochondrial multiplication, angiogenesis, and regulation of the inflammatory cascade. Recently, clinical findings have also demonstrated the beneficial effect of HBOT on veterans with treatment-resistant PTSD. Moderation of intrusive symptoms, avoidance, mood and cognitive symptoms, and hyperarousal were correlated with improved brain function and with diffusion tensor imaging-defined structural changes. This article reviews the current data on the regenerative biological effects of HBOT, and the ongoing research of its use for veterans with PTSD.

Hyperbaric oxygen therapy suppresses hypoxia and reoxygenation injury to retinal pigment epithelial cells through activating peroxisome proliferator activator receptor-alpha signalling

Retinal ischemia followed by reperfusion (IR) is a common cause of many ocular disorders, such as age-related macular degeneration (AMD), which leads to blindness in the elderly population, and proper therapies remain unavailable. Retinal pigment epithelial (RPE) cell death is a hallmark of AMD. Hyperbaric oxygen (HBO) therapy can improve IR tissue survival by inducing ischemic preconditioning responses. We conducted an in vitro study to examine the effects of HBO preconditioning on oxygen-glucose deprivation (OGD)-induced IR-injured RPE cells. RPE cells were treated with HBO (100% O2 at 3 atmospheres absolute for 90 min) once a day for three consecutive days before retinal IR onset. Compared with normal cells, the IR-injured RPE cells had lower cell viability, lower peroxisome proliferator activator receptor-alpha (PPAR-α) expression, more severe oxidation status, higher blood-retinal barrier disruption and more elevated apoptosis and autophagy rates. HBO preconditioning increased PPAR-α expression, improved cell viability, decreased oxidative stress, blood-retinal barrier disruption and cellular apoptosis and autophagy. A specific PPAR-α antagonist, GW6471, antagonized all the protective effects of HBO preconditioning in IR-injured RPE cells. Combining these observations, HBO therapy can reverse OGD-induced RPE cell injury by activating PPAR-α signalling.

Functional MRI evaluation of hyperbaric oxygen therapy effect on hand motor recovery in a chronic post-stroke patient: a case report and physiological discussion

Introduction

Impairments in activities of daily living (ADL) are a major concern in post-stroke rehabilitation. Upper-limb motor impairments, specifically, have been correlated with low quality of life. In the current case report, we used both task-based and resting state functional MRI (fMRI) tools to investigate the neural response mechanisms and functional reorganization underlying hyperbaric oxygen therapy (HBOT)-induced motor rehabilitation in a chronic post-stroke patient suffering from severe upper-limb motor impairment.

Methods

We studied motor task fMRI activation and resting-state functional connectivity (rsFC) in a 61-year-old right-handed male patient who suffered hemiparesis and physical weakness in the right upper limb, 2 years after his acute insult, pre- and post-treatment of 60 daily HBOT sessions. Motor functions were assessed at baseline and at the end of the treatment using the Fugl-Meyer assessment (FMA) and the handgrip maximum voluntary contraction (MVC).

Results

Following HBOT, the FMA score improved from 17 (severe impairment) to 31 (moderate impairment). Following the intervention during trials involving the affected hand, there was an observed increase in fMRI activation in both the supplementary motor cortex (SMA) and the premotor cortex (PMA) bilaterally. The lateralization index (LI) decreased from 1 to 0.63, demonstrating the recruitment of the contralesional hemisphere. The region of interest, ROI-to-ROI, analysis revealed increased post-intervention inter-hemispheric connectivity (P = 0.002) and a between-network connectivity increase (z-score: 0.35 ± 0.21 to 0.41 ± 0.21, P < 0.0001). Seed-to-voxel-based rsFC analysis using the right SMA as seed showed increased connectivity to the left posterior parietal cortex, the left primary somatosensory cortex, and the premotor cortex.

Conclusion

This study provides additional insights into HBOT-induced brain plasticity and functional improvement in chronic post-stroke patients.

Hyperbaric Oxygen Therapy Counters Oxidative Stress/Inflammation-Driven Symptoms in Long COVID-19 Patients: Preliminary Outcomes

Long COVID-19 patients show systemic inflammation and persistent symptoms such as fatigue and malaise, profoundly affecting their quality of life. Since improving oxygenation can oppose inflammation at multiple tissue levels, we hypothesized that hyperbaric oxygen therapy (HBOT) could arrest inflammation progression and thus relieve symptoms of COVID-19. We evaluated oxy-inflammation biomarkers in long COVID-19 subjects treated with HBOT and monitored with non-invasive methods. Five subjects (two athletes and three patients with other comorbidities) were assigned to receive HBOT: 100% inspired O2 at 2.4 ATA in a multiplace hyperbaric chamber for 90 min (three athletes: 15 HBOT × 5 days/wk for 3 weeks; two patients affected by Idiopathic Sudden Sensorineural Hearing Loss: 30 HBOT × 5 days/wk for 6 weeks; and one patient with osteomyelitis: 30 HBOT × 5 days/wk for week for 6 weeks and, after a 30-day break, followed by a second cycle of 20 HBOT). Using saliva and/or urine samples, reactive oxygen species (ROS), antioxidant capacity, cytokines, lipids peroxidation, DNA damage, and renal status were assessed at T1_pre (basal level) and at T2_pre (basal level after treatment), and the results showed attenuated ROS production, lipid peroxidation, DNA damage, NO metabolites, and inflammation biomarker levels, especially in the athletes post-treatment. Thus, HBOT may represent an alternative non-invasive method for treating long COVID-19-induced long-lasting manifestations of oxy-inflammation.

Impact of Hypoxia-Hyperoxia Exposures on Cardiometabolic Risk Factors and TMAO Levels in Patients with Metabolic Syndrome

Along with the known risk factors of cardiovascular diseases (CVDs) constituting metabolic syndrome (MS), the gut microbiome and some of its metabolites, in particular trimethylamine-N-oxide (TMAO), are actively discussed. A prolonged stay under natural hypoxic conditions significantly and multi-directionally changes the ratio of gut microbiome strains and their metabolites in feces and blood, which is the basis for using hypoxia preconditioning for targeted effects on potential risk factors of CVD. A prospective randomized study included 65 patients (32 females) with MS and optimal medical therapy. Thirty-three patients underwent a course of 15 intermittent hypoxic-hyperoxic exposures (IHHE group). The other 32 patients underwent sham procedures (placebo group). Before and after the IHHE course, patients underwent liver elastometry, biochemical blood tests, and blood and fecal sampling for TMAO analysis (tandem mass spectrometry). No significant dynamics of TMAO were detected in both the IHHE and sham groups. In the subgroup of IHHE patients with baseline TMAO values above the reference (TMAO ≥ 5 μmol/l), there was a significant reduction in TMAO plasma levels. But the degree of reduction in total cholesterol (TCh), low-density lipoprotein (LDL), and regression of liver steatosis index was more pronounced in patients with initially normal TMAO values. Despite significant interindividual variations, in the subgroup of IHHE patients with MS and high baseline TMAO values, there were more significant reductions in cardiometabolic and hepatic indicators of MS than in controls. More research is needed to objectify the prognostic role of TMAO and the possibilities of its correction using hypoxia adaptation techniques.

Role of hypoxic exosomes and the mechanisms of exosome release in the CNS under hypoxic conditions

Hypoxia is characterized by low oxygen levels in the body or environment, resulting in various physiological and pathological changes. The brain, which has the highest oxygen consumption of any organ, is particularly susceptible to hypoxic injury. Exposure to low-pressure hypoxic environments can cause irreversible brain damage. Hypoxia can occur in healthy individuals at high altitudes or in pathological conditions such as trauma, stroke, inflammation, and autoimmune and neurodegenerative diseases, leading to severe brain damage and impairments in cognitive, learning, and memory functions. Exosomes may play a role in the mechanisms of hypoxic injury and adaptation and are a current focus of research. Investigating changes in exosomes in the central nervous system under hypoxic conditions may aid in preventing secondary damage caused by hypoxia. This paper provides a brief overview of central nervous system injury resulting from hypoxia, and aimed to conduct a comprehensive literature review to assess the pathophysio-logical impact of exosomes on the central nervous system under hypoxic conditions.

Characterization and therapeutic perspectives of differentiation-inducing therapy in malignant tumors

Cancer is a major public health issue globally and is one of the leading causes of death. Although available treatments improve the survival rate of some cases, many advanced tumors are insensitive to these treatments. Cancer cell differentiation reverts the malignant phenotype to its original state and may even induce differentiation into cell types found in other tissues. Leveraging differentiation-inducing therapy in high-grade tumor masses offers a less aggressive strategy to curb tumor progression and heightens chemotherapy sensitivity. Differentiation-inducing therapy has been demonstrated to be effective in a variety of tumor cells. For example, differentiation therapy has become the first choice for acute promyelocytic leukemia, with the cure rate of more than 90%. Although an appealing concept, the mechanism and clinical drugs used in differentiation therapy are still in their nascent stage, warranting further investigation. In this review, we examine the current differentiation-inducing therapeutic approach and discuss the clinical applications as well as the underlying biological basis of differentiation-inducing agents.

Exploiting moderate hypoxia to benefit patients with brain disease: Molecular mechanisms and translational research in progress

Hypoxia is increasingly recognized as an important physiological driving force. A specific transcriptional program, induced by a decrease in oxygen (O2) availability, for example, inspiratory hypoxia at high altitude, allows cells to adapt to lower O2 and limited energy metabolism. This transcriptional program is partly controlled by and partly independent of hypoxia-inducible factors. Remarkably, this same transcriptional program is stimulated in the brain by extensive motor-cognitive exercise, leading to a relative decrease in O2 supply, compared to the acutely augmented O2 requirement. We have coined the term "functional hypoxia" for this important demand-responsive, relative reduction in O2 availability. Functional hypoxia seems to be critical for enduring adaptation to higher physiological challenge that includes substantial "brain hardware upgrade," underlying advanced performance. Hypoxia-induced erythropoietin expression in the brain likely plays a decisive role in these processes, which can be imitated by recombinant human erythropoietin treatment. This article review presents hints of how inspiratory O2 manipulations can potentially contribute to enhanced brain function. It thereby provides the ground for exploiting moderate inspiratory plus functional hypoxia to treat individuals with brain disease. Finally, it sketches a planned multistep pilot study in healthy volunteers and first patients, about to start, aiming at improved performance upon motor-cognitive training under inspiratory hypoxia.

Effects of hyperbaric oxygen therapy on human psychomotor performance: A review

Psychomotor performance is the coordination of a sensory or ideational (cognitive) process and a motor activity. All sensorimotor processes involved in planning and execution of voluntary movements need oxygen supply and seem to be significantly disrupted in states of hypoxia. Hyperbaric oxygen therapy has become a widely used treatment in routine medicine and sport medicine due to its beneficial effects on different aspects of human physiology and performance. This paper presents state-of-the-art data on the effects of hyperbaric oxygen therapy on different aspects of human psychomotor function. The therapy's influence on musculoskeletal properties and motor abilities as well as the effects of hyperbaric oxygenation on cognitive, myocardial and pulmonary functions are presented. In this review the molecular and physiological processes related to human psychomotor performance in response to hyperbaric oxygen are discussed to contribute to this fast-growing field of research in integrative medicine. Please cite this article as: Olex-Zarychta D. Effects of hyperbaric oxygen therapy on human psychomotor performance: A review. J Integr Med. 2023; 21(5): 430-440.

Fibromyalgia: Could hyperbaric oxygen therapy make the difference? Our experience

Fibromyalgia is a rare disease, difficult to diagnose and to treat. We think that hyperbaric oxygen therapy could improve its signs and symptoms although more evidences have to be accumulated.

Oxygen Variations-Insights into Hypoxia, Hyperoxia and Hyperbaric Hyperoxia-Is the Dose the Clue?

Molecular oxygen (O2) is one of the four most important elements on Earth (alongside carbon, nitrogen and hydrogen); aerobic organisms depend on it to release energy from carbon-based molecules [...].

Hyperbaric oxygen therapy for late radiation tissue injury

BACKGROUND

This is the third update of the original Cochrane Review published in July 2005 and updated previously in 2012 and 2016. Cancer is a significant global health issue. Radiotherapy is a treatment modality for many malignancies, and about 50% of people having radiotherapy will be long-term survivors. Some will experience late radiation tissue injury (LRTI), developing months or years following radiotherapy. Hyperbaric oxygen therapy (HBOT) has been suggested as a treatment for LRTI based on the ability to improve the blood supply to these tissues. It is postulated that HBOT may result in both healing of tissues and the prevention of complications following surgery and radiotherapy.

OBJECTIVES

To evaluate the benefits and harms of hyperbaric oxygen therapy (HBOT) for treating or preventing late radiation tissue injury (LRTI) compared to regimens that excluded HBOT.

SEARCH METHODS

We used standard, extensive Cochrane search methods. The latest search date was 24 January 2022.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) comparing the effect of HBOT versus no HBOT on LRTI prevention or healing.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Our primary outcomes were 1. survival from time of randomisation to death from any cause; 2. complete or substantial resolution of clinical problem; 3. site-specific outcomes; and 4.

ADVERSE EVENTS

Our secondary outcomes were 5. resolution of pain; 6. improvement in quality of life, function, or both; and 7. site-specific outcomes. We used GRADE to assess certainty of evidence.

MAIN RESULTS

Eighteen studies contributed to this review (1071 participants) with publications ranging from 1985 to 2022. We added four new studies to this updated review and evidence for the treatment of radiation proctitis, radiation cystitis, and the prevention and treatment of osteoradionecrosis (ORN). HBOT may not prevent death at one year (risk ratio (RR) 0.93, 95% confidence interval (CI) 0.47 to 1.83; I2 = 0%; 3 RCTs, 166 participants; low-certainty evidence). There is some evidence that HBOT may result in complete resolution or provide significant improvement of LRTI (RR 1.39, 95% CI 1.02 to 1.89; I2 = 64%; 5 RCTs, 468 participants; low-certainty evidence) and HBOT may result in a large reduction in wound dehiscence following head and neck soft tissue surgery (RR 0.24, 95% CI 0.06 to 0.94; I2 = 70%; 2 RCTs, 264 participants; low-certainty evidence). In addition, pain scores in ORN improve slightly after HBOT at 12 months (mean difference (MD) -10.72, 95% CI -18.97 to -2.47; I2 = 40%; 2 RCTs, 157 participants; moderate-certainty evidence). Regarding adverse events, HBOT results in a higher risk of a reduction in visual acuity (RR 4.03, 95% CI 1.65 to 9.84; 5 RCTs, 438 participants; high-certainty evidence). There was a risk of ear barotrauma in people receiving HBOT when no sham pressurisation was used for the control group (RR 9.08, 95% CI 2.21 to 37.26; I2 = 0%; 4 RCTs, 357 participants; high-certainty evidence), but no such increase when a sham pressurisation was employed (RR 1.07, 95% CI 0.52 to 2.21; I2 = 74%; 2 RCTs, 158 participants; high-certainty evidence).

AUTHORS' CONCLUSIONS

These small studies suggest that for people with LRTI affecting tissues of the head, neck, bladder and rectum, HBOT may be associated with improved outcomes (low- to moderate-certainty evidence). HBOT may also result in a reduced risk of wound dehiscence and a modest reduction in pain following head and neck irradiation. However, HBOT is unlikely to influence the risk of death in the short term. HBOT also carries a risk of adverse events, including an increased risk of a reduction in visual acuity (usually temporary) and of ear barotrauma on compression. Hence, the application of HBOT to selected participants may be justified. The small number of studies and participants, and the methodological and reporting inadequacies of some of the primary studies included in this review demand a cautious interpretation. More information is required on the subset of disease severity and tissue type affected that is most likely to benefit from this therapy, the time for which we can expect any benefits to persist and the most appropriate oxygen dose. Further research is required to establish the optimum participant selection and timing of any therapy. An economic evaluation should also be undertaken.

The Mechanisms of Action of Hyperbaric Oxygen in Restoring Host Homeostasis during Sepsis

The perception of sepsis has shifted over time; however, it remains a leading cause of death worldwide. Sepsis is now recognized as an imbalance in host cellular functions triggered by the invading pathogens, both related to immune cells, endothelial function, glucose and oxygen metabolism, tissue repair and restoration. Many of these key mechanisms in sepsis are also targets of hyperbaric oxygen (HBO2) treatment. HBO2 treatment has been shown to improve survival in clinical studies on patients with necrotizing soft tissue infections as well as experimental sepsis models. High tissue oxygen tension during HBO2 treatment may affect oxidative phosphorylation in mitochondria. Oxygen is converted to energy, and, as a natural byproduct, reactive oxygen species are produced. Reactive oxygen species can act as mediators, and both these and the HBO2-mediated increase in oxygen supply have the potential to influence the cellular processes involved in sepsis. The pathophysiology of sepsis can be explained comprehensively through resistance and tolerance to infection. We argue that HBO2 treatment may protect the host from collateral tissue damage during resistance by reducing neutrophil extracellular traps, inhibiting neutrophil adhesion to vascular endothelium, reducing proinflammatory cytokines, and halting the Warburg effect, while also assisting the host in tolerance to infection by reducing iron-mediated injury and upregulating anti-inflammatory measures. Finally, we show how inflammation and oxygen-sensing pathways are connected on the cellular level in a self-reinforcing and detrimental manner in inflammatory conditions, and with support from a substantial body of studies from the literature, we conclude by demonstrating that HBO2 treatment can intervene to maintain homeostasis.

Hyperbaric Oxygen Therapy for Veterans With Treatment-resistant PTSD: A Longitudinal Follow-up Study

INTRODUCTION

PTSD is common among veteran combatants. PTSD is characterized by brain changes, for which available treatments have shown limited effect. In a short-term study, we showed that hyperbaric oxygen therapy (HBOT) induced neuroplasticity and improved clinical symptoms of veterans with treatment-resistant PTSD. Here, we evaluated the long-term clinical symptoms of the participants of that study.

MATERIALS AND METHODS

Veterans from our short-term study were recruited 1 or more years after completing HBOT. The Clinician-Administered PTSD Scale for DSM-5 (CAPS-5) and self-reported questionnaires were administered at a single site visit. Changes in clinical scores between long-term, short-term, and pretreatment evaluations were analyzed.

RESULTS

Of the 28 participants who received HBOT during or following the short-term study, 22 agreed to participate in the current study. At a mean of 704 ± 230 days after completing the HBOT course, the mean CAPS-5 score (26.6 ± 14.4) was significantly better (lower) than at the pre-HBOT evaluation (47.5 ± 13.1, P < .001) and not statistically different from the short-term evaluation (28.6 ± 16.7, P = .745). However, for the CAPS-5 subcategory D (cognition and mood symptoms), the mean score was significantly better (lower) at long-term than at short-term evaluation (7.6 ± 5.1 vs. 10.0 ± 6.0, P < .001). At the long-term compared to the pretreatment evaluation, higher proportions of the participants were living with life partners (10 (46%) vs. 17 (77%), P = .011) and were working (9 (41%) vs. 16 (73%), P = .033). Decreases were observed between pretreatment and the long-term follow-up, in the number of benzodiazepine users (from 10 (46%) to 4 (18%), P = .07) and in the median (range) cannabis daily dose (from 40.0 g (0-50) to 22.5 g (0-30), P = .046).

CONCLUSIONS

The beneficial clinical effects of HBOT are persistent and were not attenuated at long-term follow-up of about 2 years after completion of HBOT. Additional long-term effects of the treatment were observed in social function and in decreased medication use.

Hyperbaric air mobilizes stem cells in humans; a new perspective on the hormetic dose curve

Introduction

Hyperbaric air (HBA) was first used pharmaceutically in 1662 to treat lung disease. Extensive use in Europe and North America followed throughout the 19th century to treat pulmonary and neurological disorders. HBA reached its zenith in the early 20th century when cyanotic, moribund "Spanish flu pandemic" patients turned normal color and regained consciousness within minutes after HBA treatment. Since that time the 78% Nitrogen fraction in HBA has been completely displaced by 100% oxygen to create the modern pharmaceutical hyperbaric oxygen therapy (HBOT), a powerful treatment that is FDA approved for multiple indications. Current belief purports oxygen as the active element mobilizing stem progenitor cells (SPCs) in HBOT, but hyperbaric air, which increases tensions of both oxygen and nitrogen, has been untested until now. In this study we test HBA for SPC mobilization, cytokine and chemokine expression, and complete blood count.

Methods

Ten 34-35-year-old healthy volunteers were exposed to 1.27ATA (4 psig/965 mmHg) room air for 90 min, M-F, for 10 exposures over 2-weeks. Venous blood samples were taken: (1) prior to the first exposure (served as the control for each subject), (2) directly after the first exposure (to measure the acute effect), (3) immediately prior to the ninth exposure (to measure the chronic effect), and (4) 3 days after the completion of tenth/final exposure (to assess durability). SPCs were gated by blinded scientists using Flow Cytometry.

Results

SPCs (CD45dim/CD34+/CD133-) were mobilized by nearly two-fold following 9 exposures (p = 0.02) increasing to three-fold 72-h post completion of the final (10th) exposure (p = 0.008) confirming durability.

Discussion

This research demonstrates that SPCs are mobilized, and cytokines are modulated by hyperbaric air. HBA likely is a therapeutic treatment. Previously published research using HBA placebos should be re-evaluated to reflect a dose treatment finding rather than finding a placebo effect. Our findings of SPC mobilization by HBA support further investigation into hyperbaric air as a pharmaceutical/therapy.

Understanding human aging and the fundamental cell signaling link in age-related diseases: the middle-aging hypovascularity hypoxia hypothesis

Aging-related hypoxia, oxidative stress, and inflammation pathophysiology are closely associated with human age-related carcinogenesis and chronic diseases. However, the connection between hypoxia and hormonal cell signaling pathways is unclear, but such human age-related comorbid diseases do coincide with the middle-aging period of declining sex hormonal signaling. This scoping review evaluates the relevant interdisciplinary evidence to assess the systems biology of function, regulation, and homeostasis in order to discern and decipher the etiology of the connection between hypoxia and hormonal signaling in human age-related comorbid diseases. The hypothesis charts the accumulating evidence to support the development of a hypoxic milieu and oxidative stress-inflammation pathophysiology in middle-aged individuals, as well as the induction of amyloidosis, autophagy, and epithelial-to-mesenchymal transition in aging-related degeneration. Taken together, this new approach and strategy can provide the clarity of concepts and patterns to determine the causes of declining vascularity hemodynamics (blood flow) and physiological oxygenation perfusion (oxygen bioavailability) in relation to oxygen homeostasis and vascularity that cause hypoxia (hypovascularity hypoxia). The middle-aging hypovascularity hypoxia hypothesis could provide the mechanistic interface connecting the endocrine, nitric oxide, and oxygen homeostasis signaling that is closely linked to the progressive conditions of degenerative hypertrophy, atrophy, fibrosis, and neoplasm. An in-depth understanding of these intrinsic biological processes of the developing middle-aged hypoxia could provide potential new strategies for time-dependent therapies in maintaining healthspan for healthy lifestyle aging, medical cost savings, and health system sustainability.

The effect of hyperbaric oxygen therapy on myocardial function in post-COVID-19 syndrome patients: a randomized controlled trial

Post-COVID-19 condition refers to a range of persisting physical, neurocognitive, and neuropsychological symptoms following SARS-CoV-2 infection. Recent evidence revealed that post-COVID-19 syndrome patients may suffer from cardiac dysfunction and are at increased risk for a broad range of cardiovascular disorders. This randomized, sham-control, double-blind trial evaluated the effect of hyperbaric oxygen therapy (HBOT) on the cardiac function of post-COVID-19 patients with ongoing symptoms for at least three months after confirmed infection. Sixty patients were randomized to receive 40 daily HBOT or sham sessions. They underwent echocardiography at baseline and 1-3 weeks after the last protocol session. Twenty-nine (48.3%) patients had reduced global longitudinal strain (GLS) at baseline. Of them, 13 (43.3%) and 16 (53.3%) were allocated to the sham and HBOT groups, respectively. Compared to the sham group, GLS significantly increased following HBOT (- 17.8 ± 1.1 to - 20.2 ± 1.0, p = 0.0001), with a significant group-by-time interaction (p = 0.041). In conclusion, post-COVID-19 syndrome patients despite normal EF often have subclinical left ventricular dysfunction that is characterized by mildly reduced GLS. HBOT promotes left ventricular systolic function recovery in patients suffering from post COVID-19 condition. Further studies are needed to optimize patient selection and evaluate long-term outcomes.This study was registered with ClinicalTrials.gov, number NCT04647656 on 01/12/2020.

Human Sperm as an In Vitro Model to Assess the Efficacy of Antioxidant Supplements during Sperm Handling: A Narrative Review

Spermatozoa are highly differentiated cells that produce reactive oxygen species (ROS) due to aerobic metabolism. Below a certain threshold, ROS are important in signal transduction pathways and cellular physiological processes, whereas ROS overproduction damages spermatozoa. Sperm manipulation and preparation protocols during assisted reproductive procedures-for example, cryopreservation-can result in excessive ROS production, exposing these cells to oxidative damage. Thus, antioxidants are a relevant topic in sperm quality. This narrative review focuses on human spermatozoa as an in vitro model to study which antioxidants can be used to supplement media. The review comprises a brief presentation of the human sperm structure, a general overview of the main items of reduction-oxidation homeostasis and the ambivalent relationship between spermatozoa and ROS. The main body of the paper deals with studies in which human sperm have been used as an in vitro model to test antioxidant compounds, including natural extracts. The presence and the synergic effects of different antioxidant molecules could potentially lead to more effective products in vitro and, in the future, in vivo.

Hyperbaric Oxygen Therapy in Orthopaedics: An Adjunct Therapy with an Emerging Role

Introduction

Hyperbaric oxygen therapy (HBOT) has emerged as an adjunct treatment modality in various orthopedic and rheumatological conditions. Undersea and Hyperbaric Medical Society (UHMS) defined the minimum number of HBOT cycles, dose, and frequency for various diseases. UHMS laid the 14 absolute indications for HBOT. This article deals with the mechanism of actions of HBOT and evidence of various musculoskeletal disorders where HBOT was utilized to accelerate the healing process of the diseases.

Materials and methods

The review literature search was conducted by using PubMed, SCOPUS, and other database of medical journals for identifying, reviewing, and evaluating the published clinical trial data, research study, and review articles for the use of HBOT in musculoskeletal disorders.

Results

Various clinical researchers documented cellular and biochemical advantages of HBOT which possess allodynic effects, anti-inflammatory, and prooxygenatory effects in patients with musculoskeletal conditions. Studies on the usage of HBOT in avascular necrosis and wound healing provide a platform for exploring the plausible uses of HBOT in other musculoskeletal conditions. Literature evidence states the complications associated with HBOT therapy.

Conclusion

The existing HBOT protocols have to be optimized for various musculoskeletal disorders. Large scale blinded RCTs have to be performed for demonstrating the level of evidence in the usage of HBOT in various musculoskeletal clinical scenarios.

Mesenchymal Stem Cells for Treating Alzheimer's Disease: Cell Therapy and Chemical Reagent Pretreatment

As the size of the population aged 65 and older continues to grow, the incidence and mortality rates of Alzheimer's disease (AD) are increasing annually. Unfortunately, current treatments only treat symptoms temporarily and do not alter the patients' life expectancy or course of AD. Mesenchymal stem cells (MSCs) have shown a certain therapeutic potential in neurodegenerative diseases including AD due to their neuroinflammatory regulation and neuroprotective effects. However, the low survival and homing rates of MSCs after transplantation seriously affect their therapeutic effectiveness. Therefore, appropriate in vitro preconditioning is necessary to increase the survival and homing rates of MSCs to improve their effectiveness in treating AD. Here we summarize the therapeutic mechanisms of MSCs in AD and the chemical reagents used for the pretreatment of MSCs.

The potential of hyperbaric oxygen as a therapy for neurodegenerative diseases

The World Health Organization estimates that by the year 2040, neurodegenerative diseases will be the second leading cause of death in developed countries, overtaking cancer-related deaths and exceeded only by cardiovascular disease-related death. The search for interventions has therefore become paramount to alleviate some of this burden. Based on pathways affected in neurodegenerative diseases, hyperbaric oxygen treatment (HBOT) could be a good candidate. This therapy has been used for the past 50 years for conditions such as decompression sickness and wound healing and has been shown to have promising effects in conditions associated with neurodegeneration and functional impairments. The goal of this review was to explore the history of hyperbaric oxygen therapy, its uses, and benefits, and to evaluate its effectiveness as an intervention in treating neurodegenerative diseases. Additionally, we examined common mechanisms underlying the effects of HBOT in different neurodegenerative diseases, with a special emphasis on epigenetics.

Metabolic switch in cancer - Survival of the fittest

Cell metabolism is characterised by the highly coordinated conversion of nutrients into energy and biomass. In solid cancers, hypoxia, nutrient deficiencies, and tumour vasculature are incompatible with accelerated anabolic growth and require a rewiring of cancer cell metabolism. Driver gene mutations direct malignant cells away from oxidation to maximise energy production and biosynthesis while tumour-secreted factors degrade peripheral tissues to fuel disease progression and initiate metastasis. As it is vital to understand cancer cell metabolism and survival mechanisms, this review discusses the metabolic switch and current drug targets and clinical trials. In the future, metabolic markers may be included when phenotyping individual tumours to improve the therapeutic opportunities for personalised therapy.

Mild Hyperbaric Oxygen Exposure Enhances Peripheral Circulatory Natural Killer Cells in Healthy Young Women

Mild hyperbaric oxygen (HBO) enhances oxygen absorption in blood, relieving fatigue without causing oxidative stress. The benefits of mild HBO have been recognized in the treatment of lifestyle-related diseases and hypertension, but no research has been conducted on its effects on immunity. The aim of the present study is to investigate the effect of mild HBO on natural killer (NK) cells and cytokines in healthy young women. This crossover randomized control trial was conducted with 16 healthy young women. Participants were randomly exposed to normobaric oxygen (NBO; 1.0 atmospheres absolute (ATA), 20.8% oxygen) and mild HBO conditions (1.4 ATA, 35-40% oxygen, injected 18L oxygen per minute) in a hyperbaric oxygen chamber for 70 min. Heart rate, parasympathetic activity, NK cell count, interleukin (IL)-6, IL-12p70 and derivatives of reactive oxygen metabolites (d-ROMs) were measured before and after both exposures. In the NBO condition, parasympathetic activity remained unchanged, whereas after mild HBO exposure, parasympathetic activity was significantly increased. NK cells remained unchanged after NBO exposure, while NK cells were increased after exposure to mild HBO. Exposure to mild HBO did not increase d-ROM values, IL-6 and IL-12p70 protein levels. These findings suggest that exposure to mild HBO can be a useful protocol to increase NK cells by regulating parasympathetic activity via increasing oxygen delivery.

Hyperbaric oxygen preconditioning for prevention of acute high-altitude diseases: Fact or fiction?

Acute high-altitude diseases, including acute mountain sickness (AMS), high-altitude cerebral edema (HACE), and high-altitude pulmonary edema (HAPE), have been recognized as potentially lethal diseases for altitude climbers. Various preconditioning stimuli, including hyperbaric oxygen (HBO), have been proposed to prevent acute high-altitude diseases. Herein, we reviewed whether and how HBO preconditioning could affect high-altitude diseases and summarized the results of current trials. Evidence suggests that HBO preconditioning may be a safe and effective preventive method for acute high-altitude diseases. The proposed mechanisms of HBO preconditioning in preventing high-altitude diseases may involve: 1) protection of the blood-brain barrier and prevention of brain edema, 2) inhibition of the inflammatory responses, 3) induction of the hypoxia-inducible factor and its target genes, and 4) increase in antioxidant activity. However, the optimal protocol of HBO preconditioning needs further exploration. Translating the beneficial effects of HBO preconditioning into current practice requires the "conditioning strategies" approach. More large-scale and high-quality randomized controlled studies are needed in the future.

Hyperbaric oxygen therapy for long COVID (HOT-LoCO), an interim safety report from a randomised controlled trial

BACKGROUND

With ~ 50 million individuals suffering from post-COVID condition (PCC), low health related quality of life (HRQoL) is a vast problem. Common symptoms of PCC, that persists 3 months from the onset of COVID-19 are fatigue, shortness of breath and cognitive dysfunction. No effective treatment options have been widely adopted in clinical practice. Hyperbaric oxygen (HBO₂) is a candidate drug.

METHODS

The objective of this interim analysis is to describe our cohort and evaluate the safety of HBO₂ for post covid condition. In an ongoing randomised, placebo-controlled, double blind, clinical trial, 20 previously healthy subjects with PCC were assigned to HBO₂ or placebo. Primary endpoints are physical domains in RAND-36; Physical functioning (PF) and Role Physical (RP) at 13 weeks. Secondary endpoints include objective physical tests. Safety endpoints are occurrence, frequency, and seriousness of Adverse Events (AEs). An independent data safety monitoring board (DSMB) reviewed unblinded data. The trial complies with Good Clinical Practice. Safety endpoints are evaluated descriptively. Comparisons against norm data was done using t-test.

RESULTS

Twenty subjects were randomised, they had very low HRQoL compared to norm data. Mean (SD) PF 31.75 (19.55) (95% Confidence interval; 22.60-40.90) vs 83.5 (23.9) p < 0.001 in Rand-36 PF and mean 0.00 (0.00) in RP. Very low physical performance compared to norm data. 6MWT 442 (180) (95% CI 358-525) vs 662 (18) meters p < 0.001. 31 AEs occurred in 60% of subjects. In 20 AEs, there were at least a possible relationship with the study drug, most commonly cough and chest pain/discomfort.

CONCLUSIONS

An (unexpectedly) high frequency of AEs was observed but the DSMB assessed HBO₂ to have a favourable safety profile. Our data may help other researchers in designing trials. Trial Registration ClinicalTrials.gov: NCT04842448. Registered 13 April 2021, https://clinicaltrials.gov/ct2/show/NCT04842448 . EudraCT: 2021-000764-30. Registered 21 May 2021, https://www.clinicaltrialsregister.eu/ctr-search/trial/2021-000764-30/SE.