Altitude illnesses

Acclimatized Lowlanders Exhibit a Hypocoagulable Profile after a Passive Ascent at High Altitude

Stauffer, Emeric, François Caton, Raphael Marlu, Aurélien Pichon, Landry Seyve, Michael Furian, Aymeric Paillisser, Florence Berquet, Jeremy De Abreu, Blandine Deschamps, Benoit Polack, Philippe Connes, Paul Robach, Stéphane Doutreleau, Julien V. Brugniaux, Samuel Verges, and Benoit Champigneulle. Acclimatized lowlanders exhibit a hypocoagulable profile after a passive ascent at high altitude. High Alt Med Biol. 26:209-214, 2025. Background: Discordant results have been previously reported regarding the impact of high-altitude (HA) exposure on coagulation. We aimed to investigate changes in coagulation parameters in lowlanders exposed to HA for 14 days using a combination of dynamic coagulation assays and conventional in vitro tests. Material and Methods: We assessed coagulation in 10 lowlanders using whole-blood rotational thromboelastometry (ROTEM), thrombin generation assay (TGA) on poor-platelet plasma, and conventional coagulation tests. Tests were performed at low altitude (LA, 210 m) and at the end of a 14-day sojourn at HA, including passive ascents to 3,800 m for 6 days and then to 5,100 m for 8 days. Results: Conventional tests revealed significant changes in coagulation factors and inhibitors after HA exposure, although these changes remained within normal ranges. ROTEM assays demonstrated a delayed clot initiation in EXTEM/FIBTEM, without any alteration in clot firmness, in HA versus LA (p < 0.01). TGA changes showed an increase in time to peak (p < 0.01), a decrease in endogenous thrombin potential (p < 0.05), and a decrease in thrombin peak (p < 0.001). Conclusions: We found no evidence of hypercoagulability in lowlanders after a 14-day sojourn at HA. In contrast, dynamic coagulation assays (ROTEM and TGA) revealed a hypocoagulable pattern.

High-altitude hypoxia exacerbates chemotherapy-induced myelosuppression by lowering serum G-CSF/GM-CSF and regulating apoptosis and proliferation

The unique hypoxic environment in high-altitude regions is increasingly drawing attention for its impact on the health of residents, particularly in patients post-chemotherapy. This study aimed to investigate the effects and potential mechanisms of high-altitude hypoxia on myelosuppression following chemotherapy, with the goal of providing a theoretical basis for clinical treatment. A retrospective clinical study of 80 patients with breast cancer revealed that patients in the plateau exhibited a significantly higher incidence of grade 3 or higher neutropenia and any level of neutropenia post-chemotherapy than those in the plain, with propensity score matching (PSM) confirming these associations. Animal experiments revealed that high-altitude hypoxia reduced the white blood cell (WBC) count, granulocyte count, lymphocyte count, and number of bone marrow nucleated cells (BMNCs) in cyclophosphamide (CTX)-treated mice. Additionally, high-altitude hypoxia induced a significant reduction in the proliferation index and an elevation in apoptosis rates in BMNCs. High-altitude hypoxia also significantly reduced serum levels of granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF). Transcriptomic analysis of BMNCs demonstrated that high-altitude hypoxia might modulate the hematopoietic function in CTX-induced myelosuppression mice through pathways related to hematopoiesis, such as porphyrin metabolism, hematopoietic cell lineage, ECM-receptor interaction, and PI3K-Akt signaling pathway. Our results suggest that high-altitude hypoxia exacerbates chemotherapy-induced myelosuppression, possibly through reducing the serum level of G-CSF/GM-CSF and regulating apoptosis and proliferation by PI3K-Akt signaling pathway, highlighting that cancer patients undergoing chemotherapy in hypoxic environments may require enhanced supportive care to mitigate these adverse effects.

Comparative effects of pharmacological interventions for the prevention of acute mountain sickness: A systematic review and Bayesian network meta-analysis

BACKGROUND

Acute Mountain Sickness (AMS), the most prevalent high-altitude illness, necessitates effective preventive measures due to rising sudden high-altitude exposure from tourism and occupational activities. Current Pharmacological prophylaxis lack robust comparisons, dose optimization, and confounder-adjusted analysis.

METHODS

This network meta-analysis (NMA) included 28 randomized controlled trials (RCTs), evaluated healthy individuals with a rapid ascent to >2500 m, compared 13 drugs for AMS incidence, severe AMS (SAMS) incidence, Lake Louise Score (LLS), peripheral oxygen saturation (SpO2), and pulmonary artery pressure (PAP). Quality was evaluated using Cochrane Risk of Bias tools and CINeMA (Confidence in Network Meta-Analysis) for evidence grading. Network meta-regression adjusted for ascent altitude and exposure duration to identify "time" windows or "height" windows.

RESULTS

250 mg BID acetazolamide (OR = 0.31, 95 %CI: 0.20-0.47) demonstrated a 5-day preventive efficacy window, while 375 mg BID acetazolamide (OR = 0.31, 95 %CI: 0.18-0.54) showed a shorter 3-day window. 4 mg BID dexamethasone (OR = 0.29, 95 %CI: 0.16-0.54) and 600 mg TID ibuprofen (OR = 0.44, 95 %CI: 0.3-0.64) also significantly reduced AMS incidence. No pharmacological interventions reduced SAMS incidence. After altitude adjustment, sildenafil (40 mg TID; MD = -1.11, 95 %CI: 2.01-0.25) attenuated altitude-induced PAP elevation.

CONCLUSION

Moderate-dose acetazolamide (125-250 mg BID) effectively prevents AMS with a longer prophylactic window compared to high-dose regimens (375 mg BID). There is no pharmacological intervention to prevent SAMS and no high-quality evidence to prevent high-altitude-induced PAP elevation. Our findings delineate the efficacy duration of acetazolamide across doses, while underscoring the imperative for robust clinical trials to advance the evidence base.

Atypical neurological symptoms at high altitude: a systematic literature review

BACKGROUND

Acute Mountain Sickness (AMS) is a prevalent and potentially debilitating condition affecting individuals who participate in high-altitude journeys, mostly above 2500 m. The main symptoms of AMS, listed in the Lake Louise Symptom score used to diagnose AMS, are headache, dizziness, nausea, and fatigue. However, mountaineering can also be associated with other neurological disturbances. Most records related to neurological disorders associated with high-altitude medicine focus on AMS and its typical neurological symptoms indicated in official criteria. Other conditions related to acute exposure to high altitudes are high-altitude headaches (HAH), which usually precede AMS and high-altitude cerebral oedema (HACE), which can be a complication of AMS or appear independently.

METHODS

This review aimed to describe studies that included atypical neurological symptoms, which appear during acute exposure to high altitudes and are not mentioned in the criteria of AMS or HACE. Four databases, PubMed, Embase, Web of Science, and Medline Ultimate, were screened. PROSPERO registration ID for this review is CRD420250654251.

FINDINGS

Studies that met our inclusion criteria presented symptoms related to well-known conditions, such as stroke, deep cerebral vein thrombosis, seizures, or transient neurological dysfunctions. Moreover, cranial nerve palsies, olfactory threshold impairment, multiple sclerosis worsening, or speech, memory, and sensation disturbances were described in patients at high altitudes.

CONCLUSIONS

This review shows that high altitude may be an inducing factor in other neurological disturbances besides AMS, HAH, and HACE symptoms. The growing popularity of high-altitude stays should be associated with increasing knowledge about the unusual neurological symptoms that may occur.

Unraveling the pathogenesis and prevention strategies of acute high-altitude illness through gut microecology

High-altitude environments, characterized by hypobaric and hypoxic conditions, induce acute hypoxia, resulting in decreased blood oxygen saturation. This hypoxic stress perturbs gut microecological homeostasis, significantly contributing to the pathogenesis of acute mountain sickness. Consequently, elucidating the mechanisms by which high altitude affects gut homeostasis is crucial for developing effective interventions.

Human gut microbiota adaptation to high-altitude exposure: longitudinal analysis over acute and prolonged periods

This study investigated the longitudinal effects of acute (7-day) and prolonged (3-month) high-altitude exposure on gut microbiota in healthy adult males, addressing the limited data available in human populations. A cohort of 406 healthy adult males was followed, and fecal samples were collected at three time points: baseline at 800 m (406 samples), 7 days after ascending to 4,500 m (406 samples), and 2 weeks post-return to 800 m following 3 months at high altitude (186 samples). High-throughput 16S ribosomal DNA sequencing was employed to analyze microbiota composition and diversity. Results revealed significant changes in alpha- and beta-diversity, with acute high-altitude exposure inducing more pronounced effects compared to prolonged exposure. Specifically, acute exposure increased opportunistic pathogens (Ruminococcus and Oscillibacter) but decreased beneficial short-chain fatty acid producers (Faecalibacterium and Bifidobacterium). Notably, these changes in microbiota persisted even after returning to low altitude, indicating long-term remodeling. Functional analyses revealed substantial changes in metabolic pathways, suggesting microbiota-driven adaptations to energy utilization under high-altitude hypoxic conditions. In summary, acute high-altitude exposure caused dramatic changes in gut microbiota, while prolonged exposure led to structural and functional reshaping. These findings enhance our understanding of how high-altitude environments reshape gut microbiota.

IMPORTANCE

This study is the first to investigate the impact of high-altitude exposure on gut microbiota adaptation in a large-scale longitudinal cohort. It seeks to enhance understanding of how high-altitude environments reshape gut microbiota. Acute exposure to high altitude significantly affected both α-diversity and β-diversity of gut microbiota, with acute exposure causing more pronounced changes than prolonged adaptation, indicating temporary disruptions in microbial communities. Notable shifts in microbial abundance were observed, including increased levels of genera linked to hypoxic stress (e.g., Gemmiger, Ruminococcus, and Parabacteroides) and decreased levels of beneficial bacteria (e.g., Faecalibacterium, Roseburia, and Bifidobacterium), suggesting possible adverse health effects. Functional analysis indicated changes in metabolism-related pathways post-exposure, supporting the idea that high-altitude adaptations involve metabolic adjustments for energy management. These findings enhance understanding of high-altitude physiology, illustrating the role of gut microbiota in hypoxic health.

Improved oxygen saturation and acclimatization with bacteriotherapy at high altitude

High altitude imposes physiological stress on the human body due to reduced oxygen availability, and options to improve acclimatization are limited. Seventeen participants underwent a randomized, doubled-blinded, placebo-controlled study to test the effects of a multi-strain probiotic on acclimatization to high altitude (3,800 m). The primary outcome was oxygen saturation (SpO2) during both daytime and nighttime. Secondary measurements included acute mountain sickness (AMS) score, sleep measurements, ventilation, resting heart rate, blood pressure, heart rate variability, and fasting glucose levels. The probiotic group exhibited a higher daytime and nighttime SpO2 compared to the placebo group at high altitude. The probiotic group also exhibited a lower AMS score and enhanced acclimatization relative to the placebo group at high altitude, evidenced by higher SpO2 and lower AMS scores in treatment versus placebo groups. These results suggest bacteriotherapy as a novel, non-invasive intervention for high-altitude acclimatization.

Ambulatory Blood Pressure in Tourists at Low Versus High Altitude: Colorado High Altitude Monitoring Pressure Study

IntroductionLimited evidence exists to guide travelers about blood pressure (BP) changes at high altitude (HA). Our primary objective compared 24-h ambulatory BP at low altitude (LA) vs HA in a cohort of tourists. Exploratory analyses compared results by sex and history of underlying hypertension.MethodsThis prospective observational cohort study measured ambulatory BP with Welch-Allyn ABPM 6100 monitors at LA (<1000 m) and HA (median 2751 m). Measurements included heart rate/BP every 30 min while awake and hourly overnight, BP≥180/100 mm Hg, sleep quality, and Lake Louise score (acute mountain sickness).ResultsAmong 33 participants (median age 61 y, 17 with hypertension, 12 on BP medication), 25 completed LA and HA measurements. Average 24-h mean arterial pressure (MAP) increased at HA by 6 mm Hg (95% CI, 2-10 mm Hg; P=0.04). When analyzed by the presence of preexisting hypertension, 24-h MAP was similar between LA and HA in those with underlying hypertension (mean difference, 4 mm Hg; 95% CI, -4 to 11 mm Hg; P=0.3) but rose at HA in those without (mean difference, 9 mm Hg; 95% CI, 5-14 mm Hg; P=0.001). At HA, 24-h MAP was similar in both groups (mean difference, 9 mm Hg; 95% CI, 0-19 mm Hg; P=0.05). Results did not differ by sex. Severe-range BP was common in all groups and asymptomatic.ConclusionsAmong this tourist cohort, we observed an increase in average 24-h MAP at HA. Altitude-related changes in BP varied greatly between individuals. This variation was related in part to underlying hypertension but not sex. Our data suggest that BP changes are not of clinical concern in HA travelers.

Cardiorespiratory fitness and effects of ubiquinol during high-altitude acclimatization and deacclimatization: The SCARF trial

The dynamic characteristics of cardiorespiratory fitness during high-altitude acclimatization and deacclimatization are not well elucidated, and whether ubiquinol exerts beneficial effects on cardiorespiratory fitness remains debated. In this trial, 41 volunteers were randomized to receive oral ubiquinol or placebo administration, 14 days before departure to highlands. All individuals were carried to 3900 m by air and then returned to 300 m after 7 days. Cardiopulmonary exercise testing was performed at baseline, on the third day after arrival in the highlands, and on the seventh day after return. This trial revealed the dynamic characteristics of cardiorespiratory fitness during the entire high-altitude acclimatization and deacclimatization process. The short-term journey to the highlands did not significantly affect cardiorespiratory fitness or physical performance capacity after the return. Cardiovascular and respiratory recoveries were desynchronized after returning from the highlands. Ubiquinol supplementation maintained the physical performance capacity in the highlands and facilitated acclimatization to hypoxia. Trial registration: The Chinese Clinical Trial Registry, ChiCTR2200059900, http://www.chictr.org.cn/ChiCTR2200059900.

Oxygen metabolism abnormalities and high-altitude cerebral edema

Hypobaric hypoxia is widely recognized as a prominent risk factor for high-altitude cerebral edema (HACE), which contributes to the exacerbation of multiple pathological mechanisms, including oxidative stress, mitochondrial dysfunction, disruption of blood-;brain barrier integrity, neuroinflammation, and neuronal apoptosis. Among these mechanisms, abnormalities in oxygen metabolism, including hypoxia, oxidative stress, and mitochondrial dysfunction, play pivotal roles in the pathophysiology of HACE. In this review, our objective is to enhance our comprehension of the underlying molecular mechanisms implicated in HACE by investigating the potential involvement of oxygen metabolism. Addressing aberrations in oxygen metabolism holds promise for providing innovative therapeutic strategies for managing HACE.

Systemic inflammatory response syndrome and multiple organ dysfunction syndrome caused by acute mountain sickness: a case report and literature review

Acute mountain sickness (AMS) is a common condition following rapid exposure to high altitude, though severe complications such as acute gastrointestinal bleeding, systemic inflammatory response syndrome (SIRS) and multiple organ dysfunction syndrome (MODS) are rare. Herein, we report a case of SIRS and MODS in a young traveler who visited Lhasa, Tibet (elevation 3,650 m). Three days after arrival, the patient developed headache, abdominal pain, significant hematemesis, and persistent hypotension. Gastroscopy revealed diffuse bleeding of the gastric mucosa. Laboratory tests indicated multi-organ dysfunction involving the lungs, liver, and kidneys. The patient responded well to conservative treatment of continuous oxygen supplementation. This case represents one of the first reported instances of acute gastric mucosal injury and MODS induced by AMS, underscoring the significant medical risks associated with high-altitude environments.

Emergency Care for High-Altitude Trekking and Climbing

van Veelen, Michiel J., Rudolf Likar, Markus Tannheimer, Konrad E. Bloch, Silvia Ulrich, Michael Philadelphy, Barbara Teuchner, Thomas Hochholzer, Jacqueline Pichler Hefti, Urs Hefti, Peter Paal, and Martin Burtsche. Emergency Care for High-Altitude Trekking and Climbing. High Alt Med Biol. 26:70-86, 2025. Introduction: High altitude regions are characterized by harsh conditions (environmental, rough terrain, natural hazards, and limited hygiene and health care), which all may contribute to the risk of accidents/emergencies when trekking or climbing. Exposure to hypoxia, cold, wind, and solar radiation are typical features of the high altitude environment. Emergencies in these remote areas place high demands on the diagnostic and treatment skills of doctors and first-aiders. The aim of this review is to give insights on providing the best possible care for victims of emergencies at high altitude. Methods: Authors provide clinical recommendations based on their real-world experience, complemented by appropriate recent studies and internationally reputable guidelines. Results and Discussion: This review covers most of the emergencies/health issues that can occur when trekking or during high altitude climbing, that is, high altitude illnesses and hypothermia, freezing cold injuries, accidents, for example, with severe injuries due to falling, cardiovascular and respiratory illnesses, abdominal, musculoskeletal, eye, dental, and skin issues. We give a summary of current recommendations for emergency care and pain relief in case of these various incidents.

Aldose Reductase: A Promising Therapeutic Target for High-Altitude Pulmonary Edema

The Qinghai-Tibet Plateau, famously known as the "Roof of the World", has witnessed a surge in individuals traveling or working there. However, a considerable percentage of these individuals may suffer from acute mountain sickness (AMS), with high-altitude pulmonary edema (HAPE) being a severe and potentially life-threatening manifestation. HAPE disrupts the balance of intrapulmonary tissue fluid, resulting in severe lung function impairment. Current therapeutic interventions for HAPE have limitations and are accompanied by significant side effects. Aldose reductase (AR), a crucial enzyme in the polyol metabolic pathway, has been implicated in various diseases. In this study, we sought to explore the role of AR in HAPE. Utilizing both in vivo and in vitro models, we investigated the impact of AR on hypoxia-induced pulmonary edema, vascular pressure, inflammatory factors, and oxidative stress. Our findings revealed that AR knockdown mitigated hypoxia-induced pulmonary edema, decreased the expression of vascular pressure and inflammatory factors, and enhanced the expression related to oxidative stress. These results indicate that AR may serve as a potential therapeutic target for HAPE, offering a plausible pathological basis and novel drug targets for the prevention and treatment of this condition.

Brassica rapa L. crude polysaccharide meditated synbiotic fermented whey beverage ameliorates hypobaric hypoxia induced intestinal damage

Hypobaric hypoxia causes oxidative stress and inflammatory responses and disrupts the gut microbiome and metabolome. In this study, we developed a synbiotic fermented whey beverage, combining kefir and Brassica rapa L. crude polysaccharides, to explore its protective effects against high-altitude induced injury in mice. The beverage, formulated with 0.8% (w/v) polysaccharides and kefir inoculation, demonstrated robust fermentation parameters and antioxidative capacity. When applied to a hypobaric hypoxia mouse model, the synbiotic fermented whey significantly reduced oxidation and protected the intestinal barrier by lowering inflammation, protecting the intestinal structure, increasing goblet cell counts, and reducing apoptosis. It also modulated the gut microbiota, enriching beneficial taxa as Intestinimonas and Butyricicoccaceae, while reducing harmful ones like Marvinbryantia and Proteus, and enhancing short-chain fatty acid (SCFA) production. Notably, the beverage increased berberine and nicotinic acid levels, activating the adenosine monophosphate-activated protein kinase (AMPK) signalling pathway and influencing nicotinate and nicotinamide metabolites linked to the suppression of Marvinbryantia, thereby alleviating intestinal inflammation and barrier damage. These effects contributed to the alleviation of hypoxia-induced intestinal damage in mice. This study highlights the potential of synbiotics and whey fermentation in novel nutritional interventions in high altitude environments.

Hypoxia Reduces Mouse Urine Output via HIF1α-Mediated Upregulation of Renal AQP1

Introduction

Patients with acute mountain sickness (AMS) due to hypoxia at high altitudes often exhibit abnormal water metabolism. Hypoxia-inducible factors (HIFs) are major regulators of adaptive responses to hypoxia. As transcription factors, HIFs are involved in the regulation of erythropoiesis, iron metabolism, angiogenesis, energy metabolism, and cell survival by promoting the transcriptional expression of hundreds of target genes. Roxadustat, a novel drug for the treatment of anemia associated with chronic kidney disease (CKD), acts by inhibiting the degradation of HIFs to increase their protein levels. However, the clinical use of roxadustat is frequently associated with peripheral edema, suggesting the involvement of HIFs in regulating the body's water balance possibly by modulating water reabsorption in the kidney.

Methods

We first evaluated the effect of hypoxia (8% O2) on mouse urine output. We then performed in vitro experiments using hypoxia (1% O2) and roxadustat on mouse primary proximal tubular cells (mPTCs). The quantitative polymerase chain reaction, Western blot, and immunofluorescence were used to assess AQP1 mRNA and protein expression levels. Luciferase, Chromatin immunoprecipitation (ChIP), and electrophoretic mobility shift assay (EMSA) were used to investigate the transcriptional regulation of AQP1 by HIF1α.

Results

We found that mice exposed to hypoxia (8% O2) had significantly reduced urine volume compared to mice exposed to normoxia (21% O2). Hypoxia significantly elevated AQP1 expression at both mRNA and protein levels. In vitro experiments using mouse primary cultured proximal tubular cells (mPTCs) revealed that both hypoxia and roxadustat increased AQP1 expression. Mechanistically, overexpression of HIF1α, but not HIF2α, markedly increased AQP1 protein expression. Furthermore, the upregulation of AQP1 by hypoxia and roxadustat can be blocked by the HIF1α inhibitor PX-478 in mPTCs. Finally, we found that the AQP1 gene promoter contains a putative hypoxia response element and confirmed that AQP1 is a target gene of HIF1α using Luciferase reporter, ChIP, and EMSA assays.

Conclusion

This study demonstrates that hypoxia can reduce the urine volume of mice via upregulating AQP1 expression by HIF1α in the proximal tubular epithelial cells. Our findings also suggest a potential mechanism involved in water metabolism disorders in patients with AMS and in patients with CKD receiving roxadustat treatment.

Dynamics in the prevalence and clinical manifestations of acute mountain sickness of different ascent protocols during high altitudes exposure

Background

Leisure, work, and sports activities that involve ascending to high altitudes (HA) are growing in popularity, yet they also pose the risk of developing acute mountain sickness (AMS). Despite the dynamic nature of AMS, its prevalence, clinical manifestations, and associated risks have still not to be comprehensively characterized.

Methods

A total of 770 healthy males, ranging in age from 18 to 45 years, were included in this study. The subjects were divided into two cohorts: a fast ascent cohort (n = 424) who ascended to 3,650 m by airplane, and a slow ascent cohort (n = 346) who ascended to the same altitude by bus. Subsequently, they all further ascended to 4,400 m. AMS was diagnosed using the Lake Louise Scoring system (LLS), with either the old or new version were employed.

Results

As diagnosed by the old LLS and new LLS, the incidence of AMS was 37.9 and 32.4% at 3650 m, respectively, which decreased to 35.7 and 32.4% after further ascending to 4,400 m in the fast ascent cohort; the incidence of AMS was 26.5 and 23.2% at 3650 m, which increased to 44.5 and 42.3% after further ascending to 4,400 m in the slow ascent cohort. Furthermore, there were noticeable disparities in the occurrence and progression of AMS-related symptoms among cohorts adhering to different ascent protocols. Specifically, fast ascent protocol posed a risk during the initial phase of the ascent, but transformed into a protective effect upon further ascent to a higher altitude.

Conclusion

Ascent protocol emerged as the pivotal influence on the prevalence of AMS and associated manifestations, demonstrating a transition from a risk factor during initial ascent to a protective factor following further ascent to higher altitudes. These findings suggest an innovative strategy for high-altitude expeditions and work endeavors, emphasizing the importance of a strategic plan for ascending to higher altitudes.

[Research Progress in the Role of Hypoxia-Inducible Factor 1 in Altitude Sickness and the Mechanisms Involved]

Individuals who reside at high altitudes for extended periods or those who visit these regions briefly frequently experience high-altitude response, which triggers a series of physiological and pathological changes in the body, ultimately causing altitude sickness. One of the most critical features of high-altitude environments is hypoxia. Recent studies have demonstrated that hypoxia-inducible factor 1 (HIF-1) plays a central role in mediating the body's response to hypoxic conditions at high altitudes. HIF-1, a heterodimeric transcription factor composed of an oxygen-sensitive subunit α (HIF-1α) and a constitutively expressed subunit β (HIF-1β), directly regulates the expression of multiple target genes, thereby modulating various physiological processes essential for cellular adaptation to hypoxia. According to a substantial body of research, aberrant expression of HIF-1 is implicated in the pathogenesis and progression of various diseases, including altitude sickness, cardiovascular disorders, neurological conditions, inflammatory diseases, cognitive impairment, immune dysregulation, and cancer. In this review, we provided an in-depth examination of the structural characteristics and regulatory mechanisms governing HIF-1 expression, discussed its downstream target genes, and highlighted the inhibitors currently under development. Additionally, we summarized the pivotal role and underlying mechanisms of HIF-1 in the development of altitude sickness, particularly its regulatory role in the pathophysiological processes of high-altitude pulmonary edema (HAPE), high-altitude cerebral edema (HACE), and high-altitude pulmonary hypertension (HAPH). Through a thorough examination of the role of HIF-1, we aim to provide a theoretical foundation and potential therapeutic targets for the prevention and treatment of altitude sickness.

Ginsenoside Rg1 Prevents and Treats Acute Pulmonary Injury Induced by High-Altitude Hypoxia

This study aimed to investigate the protective effects of ginsenoside Rg1 on high-altitude hypoxia-induced acute lung injury (ALI) and elucidated its molecular targets and related pathways, specifically its association with the fluid shear stress pathway. Using a combination of bioinformatics analysis and both in vivo and in vitro experiments, we assessed the role of ginsenoside Rg1 in mitigating physiological and biochemical disturbances induced by hypoxia. In the in vivo experiments, we measured arterial blood gas parameters, levels of inflammatory cells and cytokines, erythrocyte and platelet parameters, and conducted histological analysis in rats. The in vitro experiments utilized human pulmonary microvascular endothelial cells (HPMECs) and A549 cells to examine cell viability, intracellular reactive oxygen species (ROS) and Ca2⁺ levels, and mitochondrial function. The results of the in vivo experiments demonstrate that ginsenoside Rg1 significantly increased arterial blood oxygen partial pressure and saturation, elevated arterial blood glucose levels, and stabilized respiratory and metabolic functions in rats. It also reduced inflammatory cells and cytokines, such as tumor necrosis factor-α and interleukin-6, and improved erythrocyte and platelet abnormalities, supporting its protective role through the regulation of the fluid shear stress pathway. Histological and ultrastructural analyses revealed that Rg1 significantly protected lung tissue structure and organelles. In vitro experiments further confirmed that Rg1 improved cell viability in HPMEC and A549 cells under hypoxic conditions, decreased intracellular ROS and Ca2⁺ levels, and enhanced mitochondrial function. These findings collectively demonstrate that ginsenoside Rg1 exerts significant protective effects against high-altitude hypoxia-induced ALI by enhancing oxygen delivery and utilization, reducing inflammatory responses, and maintaining cellular metabolism and vascular function. Notably, the protective effects of Rg1 are closely associated with the regulation of the fluid shear stress pathway, suggesting its potential for treating high-altitude hypoxia-related diseases.

Sodium Hydrosulfide Protects Rats from Hypobaric-Hypoxia-Induced Acute Lung Injury

Hydrogen sulfide (H2S), as a key gas signaling molecule, plays an important role in regulating various diseases, with appropriate concentrations providing antioxidative, anti-inflammatory, and anti-apoptotic effects. The specific role of H2S in acute hypoxic injury remains to be clarified. This study focuses on the H2S donor sodium hydrosulfide (NaHS) and explores its protective effects and mechanisms against acute hypoxic lung injury. First, various mouse hypoxia models were established to evaluate H2S's protection in hypoxia tolerance. Next, a rat model of acute lung injury (ALI) induced by hypoxia at 6500 m above sea level for 72 h was created to assess H2S's protective effects and mechanisms. Evaluation metrics included blood gas analysis, blood routine indicators, lung water content, and lung tissue pathology. Additionally, LC-MS/MS and bioinformatic analyses were combined in performing quantitative proteomics on lung tissues from the normoxic control group, the hypoxia model group, and the hypoxia model group with NaHS treatment to preliminarily explore the protective mechanisms of H2S. Further, enzyme-linked immunosorbent assays (ELISA) were used to measure oxidative stress markers and inflammatory factors in rat lung tissues. Lastly, Western blot analysis was performed to detect Nrf2, HO-1, P-NF-κB, NF-κB, HIF-1α, Bcl-2, and Bax proteins in lung tissues. Results showed that H2S exhibited significant anti-hypoxic effects in various hypoxia models, effectively modulating blood gas and blood routine indicators in ALI rats, reducing pulmonary edema, improving lung tissue pathology, and alleviating oxidative stress, inflammatory responses, and apoptosis levels.

Hyperoxic recovery interferes with the metabolic imprint of hypoxic exercise

Supplemental oxygen (hyperoxia) improves physical performance during hypoxic exercise. Based on the analysis of metabolome and iron homeostasis from human athlete blood samples, we show that hyperoxia during recovery periods interferes with metabolic alterations following hypoxic exercise. This may impair beneficial adaptations to exercise and/or hypoxia and highlights risks of oxygen supplementation in hypoxia.

Sleep Quality Among Pilgrims at High Altitude: A Cross-Sectional Study From Gosaikunda Lake, Nepal (4380 m)

Introduction Nepal is a touristic country; globally, many people visit Nepal for mountaineering, trekking, sightseeing, and pilgrimages. Gosaikunda, located at an elevation of 4380 m (14,370 ft) in the Rasuwa district, Nepal, is a popular pilgrimage site. At high altitudes, hypobaric hypoxia is the primary cause of sleep disturbances and is characterized by difficulty falling asleep, frequent nighttime awakening, difficulty returning to sleep, and waking up earlier in the morning than desired, ultimately resulting in a reduction in total sleep duration and quality. Objective The primary objective of this study was to evaluate the quality of sleep patterns of pilgrims while undergoing acute high-altitude exposure on their journey to Gosaikunda, Nepal, which is a pilgrimage site situated at an altitude of 4380 meters (14,370 feet) above sea level. Methodology A cross-sectional descriptive study from August 7 to 14, 2022, was conducted among Gosaikunda pilgrims who visited the sacred lake in Rasuwa district in Nepal at an altitude of 4380 m, where weather is unpredictable and adverse climatic events are prevalent. The subjective sleep quality was evaluated by using the Athens Insomnia Scale (AIS). Individual participants rated each item (sleep symptoms) as 0 to 3, 0 = no problem, 1 = slight problem, 2 = marked problem, and 3 = very marked or no sleep at all. The total range of the score is 0 to 24, with a cutoff point score ≥ 6 being considered poor sleep. Results Out of 229 participants, 42 (18%), 24 (11%), and three (1%) of them experienced mild, moderate, and severe insomnia, and 160 (70%) had no sleep disturbances. Based on the Athens Insomnia Scale cutoff points, 69 (30.13%) had a score of ≥ 6, indicative of insomnia, and 160 (69.86%) had a score of less than 6, suggestive of no insomnia. Daytime sleepiness was the most common subjective sleep issue among the pilgrims suffering from insomnia (40, 57.97%) and no insomnia (96, 60%). The majority of pilgrims, 207 (99.12%), stayed overnight while ascending at Gosiakunda (4380 meters). The mean body mass index (BMI) in kg/m2 of pilgrims suffering from insomnia and those not suffering from insomnia was 25.29±5.3 and 24.58±4.47, respectively, with a P-value greater than 0.05. The mean age among pilgrims suffering from insomnia and pilgrims who didn't was 41.64±13.39 and 41.64±13.44, respectively, with a P-value greater than 0.05. The majority of the pilgrims took an average of two days to reach Gosaikunda Lake, of which 207 (99.12%) remained at altitude for one night and 22 (0.96%) stayed for more than one night. Conclusion Acute exposure to high altitude results in frequent arousal due to hypobaric hypoxia, which in turn causes pilgrims to feel mentally and physically fatigued and somnolent due to the poor sleep they experience. An elevated BMI, advanced age, and male sex were associated with poor sleep quality after acute altitude exposure. Further research is needed to better understand the mechanisms underlying these associations and to develop effective interventions to improve sleep quality during rapid ascent.

The impact of high-altitude migration on cardiac structure and function: a 1-year prospective study

Introduction

The trend of human migration to terrestrial high altitudes (HA) has been increasing over the years. However, no published prospective studies exist with follow-up periods exceeding 1 month to investigate the cardiac change. This prospective study aimed to investigate the changes in cardiac structure and function in healthy young male lowlanders following long-term migration to HA.

Methods

A total of 122 Chinese healthy young males were divided into 2 groups: those migrating to altitudes between 3600 m and 4000 m (low HA group, n = 65) and those migrating to altitudes between 4000 m and 4700 m (high HA group, n = 57). Traditional echocardiographic parameters were measured at sea level, 1 month and 1 year after migration to HA.

Results

All 4 cardiac chamber dimensions, areas, and volumes decreased after both 1 month and 1 year of HA exposure. This reduction was more pronounced in the high HA group than in the low HA group. Bi-ventricular diastolic function decreased after 1 month of HA exposure, while systolic function decreased after 1 year. Notably, these functional changes were not significantly influenced by altitude differences. Dilation of the pulmonary artery and a progressive increase in pulmonary artery systolic pressure were observed with both increasing exposure time and altitude. Additionally, a decreased diameter of the inferior vena cava and reduced bicuspid and tricuspid blood flow velocity indicated reduced blood flow following migration to the HA.

Discussion

1 year of migration to HA is associated with decreased blood volume and enhanced hypoxic pulmonary vasoconstriction. These factors contribute to reduced cardiac chamber size and slight declines in bi-ventricular function.