Acute high-altitude sickness

Inulin promotes appetite in mice by regulating the gut microbiota under conditions of rapid entry to the plateau

The objective of this study was to examine the mechanism of inulin by regulating the gut microbiota under conditions of rapid entry to the plateau stage. Fifty 7-week-old SPF-grade C57BL/6J male mice were used as experimental subjects and analysed. This study compared the structural and functional characteristics of food intake, body weight changes, serum appetite hormone levels, and intestinal flora of mice in different doses of inulin intervention and control groups in two distinct environments: plains and the rush-into plateau. The results demonstrated that inulin influenced the functional characteristics of the gut microbiota of mice in terms of energy production, conversion, carbohydrate transport, and metabolism. Furthermore, inulin enhanced the secretion of appetite hormones, resulting in appetite promotion under acute plateau conditions by increasing the relative abundance of beneficial bacteria. In addition, inulin significantly improved the body weight of mice under plateau conditions, particularly in the mid- and high-dose groups of inulin-treated mice.

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.

Neurological Manifestations Associated with Exercise at Altitude

PURPOSE OF REVIEW

The effects that exercise at altitude has on the neurological system are diverse and still not well studied, and range from metabolic adaptations to modification of cerebral blood flow and neurotransmitters. In this review we summarise changes with exercise intensity, the implications of ascent, cognitive impairment, psychosis-like symptoms, the role of exercise in the development and prevention of AMS, and use of free radical scavengers to enhance sports performance and acclimatization.

RECENT FINDINGS

We discuss the impact of oxidative stress in hypobaric hypoxia and reactive oxygen species (ROS) production and its consequences, with special focus on exercise at altitude. Finally we consider how moderate intensity exercise could help prevent AMS, and the necessity of research on high intensity exercise with elevated rate of ascent, the development of specific tools of cognitive assessment, and the role of free-radical scavengers in the prevention of AMS and neurological symptoms.

Preparation and Characterization of Mitochondrial-Targeted Nitronyl Nitroxide Loaded PLGA Nanoparticles for Brain Injury Induced by Hypobaric Hypoxia in Mice

Background

Oxidative stress is considered an important mechanism of acute high-altitude brain injury. Imidazole nitronyl nitroxide radicals are a class of stable organic radical scavengers that contain single electrons in their molecules. Therefore, in order to search for compounds with low toxicity and better effect against high-altitude brain injury, the preparation methods of PLGA nanoparticles (TPP-C6-HPN@PLGA-NPs) loaded with a synthesized mitochondria targeting imidazole nitronyl nitroxide were emphasized and investigated. Furthermore, its protective effect on brain injury caused by low-pressure hypoxia (HH) in mice was evaluated.

Methods

Nanoparticles were prepared by emulsion solvent evaporation method, and the preparation method was optimized by Box Behnken design based on particle size, encapsulation efficiency (EE) and drug loading (DL). Physical characterization and release studies of the optimized NPs were conducted. The high altitude brain injury mice model was selected to evaluate the therapeutic effect of TPP-C6-HPN@PLGA-NPs in vivo. The histological and biochemical tests were conducted in serum and brain of mice exposed to HH condition.

Results

The nanoparticle size was 120.63 nm, the EE was 89.30%, the DL was 6.82%, the polydispersity index (PDI) was 0.172, and the zeta potential was -22.67 mV under optimal preparation process. In addition, TPP-C6-HPN@PLGA-NPs owned good stabilities and sustained drug releases. TPP-C6-HPN@PLGA-NP exhibited lower toxicity than TPP-C6-HPN and was well uptaken by PC12 cells. Histological and biochemical analysis demonstrated that TPP-C6-HPN@PLGA-NPs significantly reduced HH induced pathological lesions, oxidative stress, energy dysfunction and inflammation response of brain tissue. Furthermore, nanoparticles did not show significant toxicity to major organs such as the liver and kidneys, as well as hematology in mice.

Conclusion

TPP-C6-HPN@PLGA-NPs exhibits good stability, low hemolysis rate, sustained release, low toxicity, and long residence time in brain tissue and can be used as a promising formulation for the proper treatment of HH-induced brain damage.

hUC-MSCs Prevent Acute High-Altitude Injury through Apoe/Pdgf-b/p-Erk1/2 Axis in Mice

BACKGROUND

The hypobaric hypoxic atmosphere can cause adverse reactions or sickness. The purpose of this study was to explore the preventive effect and mechanism of human umbilical cord mesenchymal stem cells (hUC-MSCs) on acute pathological injury in mice exposed to high-altitude.

METHODS

We pretreated C57BL/6 mice with hUC-MSCs via the tail vein injection, and then the mice were subjected to hypobaric hypoxic conditions for five days. The effects of hUC-MSCs on the pathological injury of lung, heart, brain were assessed by biochemical analysis, histopathological testing, quantitative real-time polymerase chain reaction (qPCR), and western blot (WB). Further, transcriptome sequencing was used to screen for the potential therapeutic targets of hUC-MSCs in acute pathological injury, the identified signaling axis was characterized using Apoe-/- mice, qPCR and WB.

RESULTS

hUC-MSCs administration notably prevented and relieved gastrointestinal symptoms and inflammation of lung and heart, increased blood oxygen saturation and serum superoxide dismutase (SOD) level, decreased serum malondialdehyde (MDA) level, rescued lung tissue injury and myocardial mitochondrial disorder, elevated nissl bodies number in brain tissue and reduced the degree of pulmonary and cerebral edema. Furthermore, hUC-MSCs pretreatment reversed the down-regulated Apoe and up-regulated Pdgf-b and p-Erk1/2 in the lung of hypobaric hypoxic mice. Thus, hUC-MSCs protected against acute pathological injury caused by hypobaric hypoxic condition via the Apoe/Pdgf-b/p-Erk1/2 axis, and the identified pathway was confirmed by the negative results of Apoe-/- mice.

CONCLUSION

hUC-MSCs possess the preventive effect on acute pathological injury caused by hypobaric hypoxia environment at high-altitude.

NMN Supplementation Inhibits Endothelial Cell ROS-Mediated Src/Pi3k/Akt Signaling Pathway to Protect High-Altitude Blood-Retinal Barrier

Purpose

High-altitude retinopathy (HAR) is primarily caused by hypobaric hypoxia, leading to hemodynamic changes in the retina and disruption of the blood-retinal barrier (BRB), which results in vasogenic edema. Currently, treatment strategies for this condition are limited. In this study, we investigated the protective effect of nicotinamide mononucleotide (NMN) against high-altitude hypoxia-induced BRB disruption and its potential molecular mechanisms.

Methods

We established a mouse model of high-altitude BRB injury using a simulated high-altitude environment chamber. Vascular leakage was observed through the Evans Blue dye leakage assay, and retinal Nicotinamide adenine dinucleotide (NAD+) levels were measured using the WST-8 assay. Human umbilical vein endothelial cells (HUVECs) were cultured in a hypoxic chamber, and the permeability of a confluent monolayer to FITC-dextran was monitored. With or without NMN intervention, VE-cadherin expression or phosphorylation at cell junctions was analyzed by Western blot and/or immunofluorescence. Apoptosis levels were assessed via Western blot, TUNEL staining, or flow cytometry, whereas reactive oxygen species (ROS) levels were observed using DCFH-DA, MitoSOX, or DHE probes. DNA damage levels were measured using 8-Oxoguanine immunofluorescence staining, and phosphorylation levels of the Src/Pi3k/Akt signaling pathway were analyzed via Western blot.

Results

High-altitude hypoxia led to increased retinal cell apoptosis and significant phosphorylation of VE-cadherin in endothelial cells, which resulted in a marked increase in BRB permeability. Both in vitro and in vivo experiments showed that NMN intervention reduced endothelial cell apoptosis and permeability. Additionally, NMN protected the endothelial barrier by regulating ROS levels in endothelial cells, inhibiting Src phosphorylation, and downregulating the downstream Pi3k/Akt signaling pathway.

Conclusions

These findings establish the role of NMN and the ROS-mediated Src/Pi3k/Akt signaling pathway in protecting the endothelial barrier, and identify a potential therapeutic strategy for protecting against hypoxia-related BRB leakage.

Salidroside improves blood-brain barrier integrity and cognitive function in hypobaric hypoxia mice by inhibiting microglia activation through GSK3β

Salidroside, an active component found in Rhodiola rosea L., has emerged as a potential therapeutic agent for the prevention and treatment of hypoxic brain injury, while the precise target and mechanism of salidroside were remain unclear. The study utilized techniques such as network pharmacology, transcriptome sequencing to investigate the mechanism and target of salidroside in regulating blood-brain barrier (BBB) function to protect hypoxic brain injury in vivo. Utilized macromolecular docking and molecular biology techniques to explore the molecular mechanism of salidroside in alleviating brain injury induced by hypoxia in BV2 cell model. The results show that salidroside alleviated the learning and memory dysfunction and pathological injury in mice exposed to hypobaric hypoxia, reduced brain water content and attenuate the inflammatory response and oxidative stress, effectively reversed S100β in serum and promoted the repair of BBB. GSK3β is an important therapeutic target of salidroside in the treatment of hypoxic cognitive impairment, and salidroside can specifically bind GSK3β in the ATP binding pocket, inducing the phosphorylation of GSK3β, targeting downstream Nrf-2 to regulate microglia activity, promoting the accumulation of β-catenin, thereby inhibiting microglial activation, improving the BBB integrity injury and achieving a neuroprotective effect. This study demonstrates that salidroside can inhibit the activation of microglia by inducing GSK3β phosphorylation, achieve neuroprotective effects and alleviate learning and memory dysfunction in hypobaric hypoxia mice. This study provides a theoretical basis for the development of salidroside and the clinical application of Rhodiola rosea L.

Global research trends and emerging hotspots in acute high altitude illness: a bibliometric analysis and review (1937-2024)

INTRODUCTION

Acute High Altitude Illness (AHAI) includes conditions such as Acute Mountain Sickness (AMS), High Altitude Cerebral Edema (HACE), and High Altitude Pulmonary Edema (HAPE), which result from rapid ascent to altitudes exceeding 2,500 m. Although interest in AHAI research has been growing, a systematic and comprehensive analysis of global research trends remains lacking.

CONTENT

A total of 3,214 articles and reviews published from 1937 to 2024 were retrieved from the Web of Science Core Collection. Bibliometric tools, including CiteSpace and VOSviewer, were applied to thoroughly assess publication trends, collaborative networks among authors, institutional contributions, and keyword co-occurrence patterns. The dataset represents the contributions of over 11,758 authors across 86 countries and 3,378 institutions, reflecting the significant growth of this research domain.

SUMMARY AND OUTLOOK

Our findings highlight the increasing scholarly attention to AHAI research, with the United States leading in publication numbers. Emerging research themes include cellular activation, oxidative stress, risk factors, and hypobaric hypoxia. This is the first systematic bibliometric review of AHAI literature, offering a detailed roadmap of research hotspots, potential collaborations, and key future directions. These findings provide a valuable reference for researchers aiming to explore gaps and build on the existing knowledge in high-altitude medicine.

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.

Exploring the mechanism of action of huoermai essential oil for plateau insomnia based on the camp/CREB/BDNF/gabaergic pathway

ETHNOPHARMACOLOGICAL RELEVANCE

The traditional Huoermai therapy is a treatment for insomnia used by the Tibetan people living on the Tibetan plateau in China. This therapy involves the use of Myristica fragrans Houtt. and Carum carvi L., along with fomentation and massage, and has shown significant clinical effects. However, the mechanism of how Huoermai therapy treats plateau insomnia needs further clarification.

AIM OF THE STUDY

This study aimed to investigate the mechanism of action of Huoermai essential oil (HEO) in treating plateau insomnia, focusing on the cAMP/CREB/BDNF/GABAergic pathway.

METHODS

The major components of Huoermai essential oil were identified by Gas chromatography-mass spectrometry (GC-MS) for subsequent network pharmacology analysis. Proteomics techniques were employed to pinpoint disparities in brain tissue protein expression in a mouse model of plateau insomnia following Huoermai therapy administration, in conjunction with network pharmacology to forecast pathways related to hypoxia and insomnia. Plateau insomnia mouse model was established and the therapeutic impact of Huoermai essential oil was evaluated. Hematoxylin & Eosin staining(HE) was conducted to observe pathological damage to the cortex, hippocampus, thalamus and hypothalamus structures. Changes in serotonin (5-HT), melatonin (MT), adenosine (AD), cyclic adenosine monophosphate (cAMP) and malondialdehyde (MDA) levels in mouse brain tissue were gauged through enzyme-linked immunosorbent assay (ELISA) to assess sleep status and oxidative stress levels in mice. Molecular docking was employed to anticipate the target binding energy of Huoermai essential oil constituents. ELISA and Western Blot (WB) were used to ascertain the expression of cAMP/CREB/BDNF/GABAergic pathway.

RESULTS

The results indicated that HEO positively impacted intermittent hypobaric hypoxia-induced plateau insomnia in mice. Histological examination results showed that HEO ameliorated neuronal damage in specific regions of the brain affected by plateau insomnia, such as the cortex, hippocampus, thalamus, and hypothalamus. Through GC-MS analysis, 56 volatile oil components were identified. Subsequently, a combined network pharmacology and proteomics analyses led to selecting the cAMP/CREB/BDNF/GABAergic pathway for further study. ELISA experiments demonstrated that HEO treatment increased GABA and MT levels while significantly reducing 5-HT and adenosine levels in brain tissue of mice with plateau insomnia. WB results revealed that HEO ameliorated plateau insomnia by suppressing the hyperactivation of the cAMP pathway, increasing brain-derived neurotrophic factor (BDNF) levels and B-cell lymphoma-2 (BCL-2) expression, and alleviating hypoxia-induced oxidative stress. Moreover, molecular docking results showed strong binding affinity of all pharmacological components to their targets and proteins in the brain.

CONCLUSION

These results indicate that HEO significantly prolongs sleep duration in plateau insomniac mice and treats plateau insomnia by modulating levels of sleep-related regulators, modulating the cAMP pathway, increasing GABA receptor expression, and improving neuronal survival and anti-apoptosis.

Eleutheroside B Ameliorates Cardiomyocytes Necroptosis in High-Altitude-Induced Myocardial Injury via Nrf2/HO-1 Signaling Pathway

This study was designed to evaluate the protective effects of eleutheroside B (EB) in high-altitude-induced myocardial injury (HAMI) and to unravel the underlying molecular mechanisms. SD rats were used for in vivo experiments. Following pretreatment with EB, the SD rats were exposed to a hypobaric environment within a hypobaric chamber for 48 h. Electrocardiograms, H&E staining, and serum biochemical indices were measured to evaluate the protective effects of EB on HAMI. Immunofluorescence and Western blotting were utilized to detect the expression of associated proteins. In parallel, a hypobaric hypoxic cell incubator was used to establish an in vitro model of hypobaric hypoxia-induced cell injury. The anti-necroptotic effect and its potential underlying mechanisms were investigated and verified in vitro. Exposure to hypobaric hypoxia led to electrocardiogram disorders, pathological changes in myocardial tissue, increased concentrations of BNP and CK-MB, and elevated levels of oxidative stress indicators and inflammatory factors. Additionally, the expression of necroptosis-related proteins was upregulated. Pretreatment with EB effectively ameliorated myocardial injury caused by hypobaric hypoxia, mitigated oxidative stress and inflammation, and suppressed necroptosis. Furthermore, EB facilitated the translocation of Nrf2 into the nucleus. In conclusion, this study provides evidence suggesting that EB may exert a protective effect against HAMI by inhibiting cardiomyocyte necroptosis via the Nrf2/HO-1 signaling pathway.

Flying to high-altitude destinations

Every year millions of people fly to high-altitude destinations. They thereby expose themselves to specific high-altitude conditions. The hypoxic environment (low ambient oxygen availability) constitutes a major factor affecting health and well-being at high altitude. While the oxygen availability is already moderately reduced inside the aircraft cabin, this reduction becomes aggravated when leaving the plane at high-altitude destinations. Especially if not pre-acclimatized, the risk of suffering from high-altitude illnesses, e.g., acute mountain sickness, high-altitude cerebral or pulmonary edema, increases with the level of altitude. In addition, diminished oxygen availability impairs exercise tolerance, which not only limits physical activity at high altitude but may also provoke symptomatic exacerbation of pre-existing diseases. Moreover, the cold and dry ambient air and increased levels of solar radiation may contribute to adverse health effects at higher altitude. Thus, medical pre-examination and pre-flight advice, and proper preparation (pre-acclimatization, exercise training, and potentially adaptation of pharmacological regimes) are of utmost importance to reduce negative health impacts and frustrating travel experiences.

Nocturnal pulse oxygen saturation dynamics at simulated high altitude: Predictive value for acute mountain sickness in healthy men born pre-term

The physiological sequelae of pre-term birth might influence the responses of this population to hypoxia. Moreover, identifying variables associated with development of acute mountain sickness (AMS) remains a key practically significant area of altitude research. We investigated the effects of pre-term birth on nocturnal oxygen saturation (S p O 2 ${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$ ) dynamics and assessed the predictive potential of nocturnalS p O 2 ${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$ -related metrics for morning AMS in 12 healthy adults with gestational age < 32 weeks (pre-term) and 12 term-born control participants. Participants spent one night at a simulated altitude of ∼4200 m (normobaric hypoxia; fraction of inspired O2 = 0.141), with nocturnalS p O 2 ${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$ and heart rate recorded continuously at the fingertip using pulse oximetry and with morning AMS assessed using the Lake Louise scale. Pre-term and term-born participants had similar nocturnal meanS p O 2 ${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$ (mean ± SD; 77% ± 3% vs. 77% ± 4%; P = 0.661), minimumS p O 2 ${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$ (median[IQR]; 67[4]% vs. 69[5]%; P = 0.223), relative time spent withS p O 2 ${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$  < 80% (72% ± 29% vs. 70% ± 27%; P = 0.879) and mean heart rate (79 ± 12 vs. 71 ± 7 beats/min; P = 0.053). However, the increase inS p O 2 ${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$ between the two halves of the night was blunted with prematurity (-0.12% ± 1.51% vs. 1.11% ± 0.78%; P = 0.021). Moreover, the cumulative relative desaturation-based hypoxic 'load' was higher with prematurity (32[26]%min/h vs. 7[25]%min/h; P = 0.039), underpinned by increased desaturation frequency (69[49] vs. 21[35] counts/h; P = 0.009). MeanS p O 2 ${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$ , minimumS p O 2 ${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$ , morningS p O 2 ${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$ and relative time spent withS p O 2 ${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$  < 80% predicted AMS incidence better than a random classifier exclusively in the pre-term group, with no other variables predictive of AMS in the two groups separately or combined. Overall, pre-term birth might alter nocturnalS p O 2 ${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$ dynamics and influence AMS prediction in severe hypoxia.

High Altitude Pulmonary Edema Associated with Climbing Mount Fuji: A Case Report

A 51-year-old man presented to the emergency department with rapidly progressive dyspnea that developed while climbing Mount Fuji. He had climbed Mount Fuji twice without experiencing similar symptoms. On arrival, his oxygen saturation was 91% on 10 L/min of oxygen with a non-rebreather mask. Chest imaging revealed scattered bilateral infiltrating shadows. He was diagnosed with high-altitude pulmonary edema (HAPE) and treated with high-dose corticosteroids, calcium-channel blockers, antibiotics, and oxygen via a high-flow nasal cannula. The patient responded to treatment and was discharged on day 7. Climbers should be aware of the risk of HAPE when climbing Mount Fuji.

Google trend analysis of the Indian population reveals a panel of seasonally sensitive comorbid symptoms with implications for monitoring the seasonally sensitive human population

Seasonal variations in the environment induce observable changes in the human physiological system and manifest as various clinical symptoms in a specific human population. Our earlier studies predicted four global severe seasonal sensitive comorbid lifestyle diseases (SCLDs), namely, asthma, obesity, hypertension, and fibrosis. Our studies further indicated that the SCLD category of the human population may be maladapted or unacclimatized to seasonal changes. The current study aimed to explore the major seasonal symptoms associated with SCLD and evaluate their seasonal linkages via Google Trends (GT). We used the Human Disease Symptom Network (HSDN) to dissect common symptoms of SCLD. We then exploited medical databases and medical literature resources in consultation with medical practitioners to narrow down the clinical symptoms associated with four SCLDs, namely, pulmonary hypertension, pulmonary fibrosis, asthma, and obesity. Our study revealed a strong association of 12 clinical symptoms with SCLD. Each clinical symptom was further subjected to GT analysis to address its seasonal linkage. The GT search was carried out in the Indian population for the period from January 2015-December 2019. In the GT analysis, 11 clinical symptoms were strongly associated with Indian seasonal changes, with the exception of hypergammaglobulinemia, due to the lack of GT data in the Indian population. These 11 symptoms also presented sudden increases or decreases in search volume during the two major Indian seasonal transition months, namely, March and November. Moreover, in addition to SCLD, several seasonally associated clinical disorders share most of these 12 symptoms. In this regard, we named these 12 symptoms the "seasonal sensitive comorbid symptoms (SSC)" of the human population. Further clinical studies are needed to verify the utility of these symptoms in screening seasonally maladapted human populations. We also warrant that clinicians and researcher be well aware of the limitations and pitfalls of GT before correlating the clinical outcome of SSC symptoms with GT.

Correlation between hematological indicators in acclimatized high-altitude individuals and acute mountain sickness

Background

The impact of acute mountain sickness (AMS) on individuals ascending to plateaus, soon after exposure to high altitudes, is well-documented. However, the specific relationship between AMS and alterations in blood parameters remains unclear.

Methods

A total of 40 healthy volunteers were recruited. Following their arrival at an altitude of 3,300 m, an AMS questionnaire survey was administered 48 h later. Based on the AMS scores obtained, participants were categorized into three groups: non-AMS, mild AMS, and moderate/severe AMS (encompassing both moderate and severe cases). Blood routine tests were performed on all groups at 3-, 7-, and 30-days post-arrival at the plateau, with blood oxygen saturation tests conducted at 3 and 30 days after rapidly entering the plateau.

Results

In the current investigation, a total of 40 participants were stratified into non-AMS (n = 24), mild-AMS (n = 8), and moderate/severe-AMS (n = 8) cohorts subsequent to rapid ascension to an altitude of 3,300 m. The incidence of AMS in this study was 40%. Noteworthy elevations in red blood cells (RBC), hemoglobin (Hb), and hematocrit (HCT) levels were noted at the 3-day mark post-ascent across all delineated groups. By the 7th day, the moderate/severe-AMS cohort displayed sustained increments in Hb and HCT levels, whereas solely HCT levels rose in the mild-AMS and non-AMS cohorts. Upon reaching the 30-day milestone, the moderate/severe-AMS group demonstrated a reduction in RBC, Hb, and HCT levels, while only HCT levels decreased in the mild-AMS and non-AMS groups. Furthermore, it was observed that all groups exhibited notable reductions in oxygen saturation (SpO2) at 3 days post-ascent, followed by a partial recovery at 30 days, albeit remaining below baseline levels. The correlation analysis results indicated that RBC, Hb, and HCT exhibited a positive correlation with the severity of AMS after a 7-day acclimatization period at high altitude. Conversely, SpO2 demonstrated a negative correlation with the severity of AMS following the same duration at high altitude. The findings of the study suggest a strong association between alterations in RBC, Hb, and HCT levels and AMS, particularly among individuals in the moderate/severe-AMS category who displayed more significant fluctuations in these parameters.

Conclusion

Individuals suffering from moderate to severe AMS demonstrated increased levels of RBC, Hb, and HCT, as well as reduced SpO2, indicating a greater need for oxygen adaptation to high-altitude hypoxia. These findings emphasize the physiological adjustments to high altitudes and their potential implications for the treatment of AMS.

Senolytic cocktail dasatinib and quercetin attenuates chronic high altitude hypoxia associated bone loss in mice

Chronic high-altitude hypoxia (CHH) induces irreversible abnormalities in various organisms. Emerging evidence indicates that CHH markedly suppresses bone mass and bone strength. Targeting senescent cells and the consequent senescence-associated secretory phenotype (SASP) with senolytics is a recently developed novel therapy for multiple age-related diseases. The combination of dasatinib and quercetin (DQ) has been proven to selectively target senescent cells and attenuate SASP in multiple tissues. In this study, experimental mice were subjected to an environment simulating 5,000 m above sea level for 8 weeks to induce CHH conditions. Our results indicated that DQ supplementation was well-tolerated with negligible toxicity. In vivo, DQ prevented reductions in BMD and BMC and improved bone microarchitecture against CHH-induced changes. Biomechanical testing demonstrated that DQ significantly improved the mechanical properties of femoral bones in CHH-exposed mice. Furthermore, DQ mitigated senescence in LepR + BMSCs and decreased the population of senescent cells, as evidenced by reduced senescence markers and SA-β-Gal staining. An analysis of serum and bone marrow aspirates showed that DQ treatment preserved angiogenic and osteogenic coupling in the bone marrow microenvironment by maintaining type H vessels and angiogenic growth factors. The results suggest that DQ has significant anti-senescence effects on BMSCs and a positive impact on the bone marrow microenvironment, supporting its clinical investigation as a therapeutic agent for CHH-related osteoporosis.

Pulse oximetry for the prediction of acute mountain sickness: A systematic review

Acute mountain sickness (AMS) causes serious illness for many individuals ascending to high altitude (HA), although preventable with appropriate acclimatisation. AMS is a clinical diagnosis, with symptom severity evaluated using the Lake Louise Score (LLS). Reliable methods of predicting which individuals will develop AMS have not been developed. This systematic review evaluates whether a predictive relationship exists between oxygen saturation and subsequent development of AMS. PubMed, PubMed Central, MEDLINE, Semantic Scholar, Cochrane Library, University of Birmingham Library and clinicaltrials.gov databases were systematically searched from inception to 15 June 2023. Human studies involving collection of peripheral blood oxygen saturation (S p O 2 ${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$ ) from healthy lowlanders during ascent to HA that evaluated any relationship betweenS p O 2 ${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$ and AMS severity were considered for eligibility. Risk of bias was assessed using a modified Newcastle-Ottawa Tool for cohort studies (PROPSPERO CRD42023423542). Seven of 980 total identified studies were ultimately included for data extraction. These studies evaluatedS p O 2 ${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$ and AMS (via LLS) in 1406 individuals during ascent to HA (3952-6300 m). Risk of bias was 'low' for six and 'moderate' for one of the included studies. Ascent profiles andS p O 2 ${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$ measurement methodology varied widely, as did the statistical methods for AMS prediction. Decreasing oxygen saturation measured with pulse oximetry during ascent shows a positive predictive relationship for individuals who develop AMS. Studies have high heterogeneity in ascent profile and oximetry measurement protocols. Further studies with homogeneous methodology are required to enable statistical analysis for more definitive evaluation of AMS predictability by pulse oximetry.

The effects of real vs simulated high altitude on associative memory for emotional stimuli

INTRODUCTION

This study aimed to investigate the effects of normobaric hypoxia (NH) and hypobaric hypoxia (HH) on associative memory performance for emotionally valenced stimuli.

METHODS

Two experiments were conducted. In Study 1, n = 18 undergraduates performed an associative memory task under three NH conditions (FiO2= 20.9 %, 15.1 %, 13.6 %) using a tent with a hypoxic generator. In Study 2, n = 20 participants were assessed in a field study at various altitudes on the Himalayan mountains, including the Pyramid Laboratory (5000 m above sea level), using functional Near-Infrared Spectroscopy (fNIRS) and behavioral assessments.

RESULTS

Study 1 revealed no significant differences in recognition accuracy across NH conditions. However, Study 2 showed a complex relationship between altitude and memory for emotionally valenced stimuli. At lower altitudes, participants more accurately recognized emotional stimuli compared to neutral ones, a trend that reversed at higher altitudes. Brain oxygenation varied with altitude, indicating adaptive cognitive processing, as revealed by fNIRS measurements.

CONCLUSIONS

These findings suggest that hypoxia affects associative memory and emotional processing in an altitude-dependent manner, highlighting adaptive cognitive mechanisms. Understanding the effects of hypobaric hypoxia on cognition and memory can help develop strategies to mitigate its impact in high-altitude and hypoxic environments.

Differential Diagnoses for Isolated Right Sixth Nerve Palsy in the High Altitude Setting: A Case Report

This case report describes the presentation and management of a patient with an isolated right sixth nerve palsy while trekking in Nepal. Consideration is made of the anatomy of the sixth nerve and the differential diagnoses afforded to this isolated sign, including high altitude cerebral edema. The case stresses the need to exclude life-threatening pathologies for any symptoms associated with altitude and includes decision-making processes on whether to monitor the patient in the field or evacuate them to a definitive care facility.

Author Response-High Altitude Liver Failure: An Infrequent Trigger

How to cite this article: Srinivasan A, Prusty BSK. Author Response-High Altitude Liver Failure: An Infrequent Trigger. Indian J Crit Care Med 2024;28(12):1181.

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.

[Basic Research on the Microstructure of Rat Bones in the High-Altitude Environment of Qinghai-Tibet Plateau]

Objective

To establish a hypobaric hypoxia rat model in a real high-altitude environment, to investigate the effects of the real high-altitude environment on rat bone mass and bone microstructure using multiple methods such as Micro CT, blood biochemistry, and pathology, and to explore the potential mechanisms involved.

Methods

Sprague Dawley (SD) rats were transported to the Yushu Plateau Laboratory (at 4250 m above sea level) in Qinghai Province and kept there for 4, or 8, or 18 months. These groups were designated as H-4, H-8, and H-18, respectively. Upon completion of the high-altitude exposure, these animals were transported to the Molecular Imaging Laboratory, West China Hospital, Sichuan University (at 500 m above sea level) in Chengdu for relevant testing and comparison with the control animals raised in a low-altitude environment for the same durations (designated L-4, L-8, and L-18). The tests performed included blood biochemistry, Micro CT imaging, and pathological assessments such as ELISA, Western blot, and HE and TRAP staining.

Results

Compared with that of the control group, the body mass of rats in the H-4 and H-18 groups decreased significantly (H-4 group vs. L-4 group: [513.75±35.10] g vs. [649.18±60.03] g, P<0.01; H-18 group vs. L-18 group: [535.58±66.65] g vs. [670.86±44.96] g, P<0.01). The serum Ca2+ concentration was higher in the H-8 group and H-18 group compared to that in the control group (H-8 group vs. L-8 group: [2.48±0.09] mmol/L vs. [2.38±0.07] mmol/L, P<0.05; H-18 group vs. L-18 group: [2.55±0.11] mmol/L vs. [2.13±0.27] mmol/L, P<0.05). No statistically significant difference was observed in the concentration of P3+. Bone metabolism indicator cross-linked carboxy-terminal telopeptide of type Ⅰ collagen (CTX-Ⅰ) was significantly increased in all high-altitude groups compared to the low-altitude groups (H-4 group vs. L-4 group: [1.44±0.08] ng/mL vs. [0.70±0.13] ng/mL, P<0.01; H-8 group vs. L-8 group: [1.52±0.10] ng/mL vs. [0.75±0.10] ng/mL, P<0.01; H-18 group vs. L-18 group: [2.70±0.13] ng/mL vs. [1.94±0.15] ng/mL, P<0.01). In addition, CT results showed a decrease in bone volume fraction of trabecular bone in the three high-altitude groups (H-4 group vs. L-4 group: [7.48±2.35]% vs. [10.40±2.93]%, P<0.05; H-8 group vs. L-8 group: [7.17±2.68]% vs. [10.09±2.95]%, P<0.05; H-18 group vs. L-18 group: [2.90±2.91]% vs. [8.68±4.11]%, P<0.01), and increased trabecular separation in the three high-altitude groups (H-4 group vs. L-4 group: [0.70±0.12] mm vs. [0.60±0.06] mm, P<0.05; H-8 group vs. L-8 group: [0.68±0.07] mm vs. [0.59±0.05] mm, P<0.01; H-18 group vs. L-18 group: [0.80±0.09] mm vs. [0.70±0.09] mm, P<0.05). TRAP staining showed an increase in osteoclasts in the H-4 and H-18 groups. Western blot results indicated an increase in the expression of receptor activator of nuclear factor-κB ligand (RANKL) and hypoxia inducible factor-1α (HIF-1α) in high-altitude environment, while the expression of osteoprotegerin (OPG) was inhibited.

Conclusion

The impact of high-altitude environment on rat femurs is characterized primarily by a reduction in trabecular bone mass and damage to bone microstructure.

Nutrition, hydration and supplementation considerations for mountaineers in high-altitude conditions: a narrative review

Staying and climbing in high mountains (>2,500 m) involves changes in diet due to poor access to fresh food, lack of appetite, food poisoning, environmental conditions and physiological changes. The purpose of this review is to summarize the current knowledge on the principles of nutrition, hydration and supplementation in high-altitude conditions and to propose practical recommendations/solutions based on scientific literature data. Databases such as Pubmed, Scopus, ScienceDirect and Google Scholar were searched to find studies published from 2000 to 2023 considering articles that were randomized, double-blind, placebo-controlled trials, narrative review articles, systematic reviews and meta-analyses. The manuscript provides recommendations for energy supply, dietary macronutrients and micronutrients, hydration, as well as supplementation recommendations and practical tips for mountaineers. In view of the difficulties of being in high mountains and practicing alpine climbing, as described in the review, it is important to increase athletes' awareness of nutrition and supplementation in order to improve well-being, physical performance and increase the chance of achieving a mountain goal, and to provide the appropriate dietary care necessary to educate mountaineers and personalize recommendations to the needs of the individual.

Neurofilament Light Chain Is Associated With Acute Mountain Sickness

BACKGROUND

Neurological symptoms are common in acute mountain sickness (AMS); however, the extent of neuroaxonal damage remains unclear. Neurofilament light chain (NfL) is an established blood biomarker for neuroaxonal damage.

OBJECTIVE

To investigate whether plasma (p) NfL levels increase after simulated altitude exposure, correlate with the occurrence of AMS, and might be mitigated by preacclimatization.

METHODS

Healthy subjects were exposed to simulated high altitude (4500 m) by the use of a normobaric hypoxic chamber at the University of Innsbruck two times, that is, within Cycle 1 (C1) over 12 h, and within Cycle 2 (C2) for another 12 h but with a random assignment to prior acclimatization or sham acclimatization. Before each cycle (measurement [M] 1 and 3) and after each cycle (M2 and M4), clinical data (arterial oxygen saturation [SaO2], heart rate, and Lake Louise AMS score [LLS]) and plasma samples were collected. pNfL was measured using single-molecule array (Simoa) technique.

RESULTS

pNfL levels did not significantly change within each study cycle, but increased over the total study period (M1: 4.57 [3.34-6.39], M2: 4.58 [3.74-6.0], M3: 5.64, and M4: 6.53 [4.65-7.92] pg/mL, p < 0.001). Subjects suffering from AMS during the study procedures showed higher pNfL levels at M4 (6.80 [6.19-8.13] vs. 5.75 [4.17-7.35], p = 0.048), a higher total pNfL increase (2.88 [1.21-3.48] vs. 0.91 [0.53-1.48], p = 0.022) compared to subjects without AMS. An effect of preacclimatization on pNfL levels could not be observed.

CONCLUSIONS

pNfL increases alongside exposure to simulated altitude and is associated with AMS.

Acute mountain sickness on Jade Mountain: Results from the real-world practice (2018-2019)

Acute mountain sickness (AMS) is initiated in response to a hypoxic and hypobaric environment at a high altitude. The precise prevalence of AMS in Jade Mountain climbers remained largely unknown, particularly data obtained from real medical consultations. An overnight stay at the Pai-Yun Lodge (3402 m) is usually required before an ascent of the Jade Mountain. Since 2004, a Pai-Yun Clinic has been established in the Pai-Yun Lodge. The Pai-Yun Clinic provided regular and emergency medical service every weekend. We conducted a retrospective study by using medical records from the Pai-Yun Clinic between 2018 and 2019. A total of 1021 patients were enrolled, with 56.2 % males. Different age groups were 3.2 %, 54.5 %, 37.9 %, and 4.4 % in <20, 20-39, 40-59, and ≥60 years, respectively. There were 582 (57.0 %) patients diagnosed to have AMS (230 [39.5 %] were mild type and 352 [60.5 %] were severe type). The factors associated with AMS development included young age, absence of climbing history (>3000 m) within the last 3 months, first climbing (>3000 m) experience, taking preventive medication, low oxygen saturation, and a high Lake Louise AMS score (LLAMSS). The factors associated with AMS severity included absence of taking preventive medication, low oxygen saturation, and a high LLAMSS. Approximately 15 % of Jade Mountain climbers needed medical service, of which 60 % had AMS. 60 % of patients with AMS must require oxygen supply or medication prescription. Oxygen saturation measure and LLAMSS evaluation are reasonable tools to predict the occurrence and severity of AMS on Jade Mountain.

Changes in immune cell populations during acclimatization to high altitude

The immune response to acute hypoxemia may play a critical role in high-altitude acclimatization and adaptation. However, if not properly controlled, hypoxemia-induced inflammation may exacerbate high-altitude pathologies, such as acute mountain sickness (AMS), or other hypoxia-related clinical conditions. Several studies report changes in immune cell subsets at high altitude. However, the mechanisms underlying these changes, and if these alterations are beneficial or maladaptive, remains unknown. To address this, we performed multiparameter flow cytometry on peripheral blood mononuclear cells (PBMCs) collected throughout 3 days of high-altitude acclimatization in healthy sea-level residents (n = 20). Additionally, we conducted in vitro stimulation assays to test if high-altitude hypoxia exposure influences responses of immune cells to subsequent inflammatory stimuli. We found several immune populations were altered at high altitude, including monocytes, T cells, and B cells. Some changes in immune cell populations are potentially correlated with AMS incidence and severity. In vitro high-altitude PBMC cultures stimulated with lipopolysaccharide (LPS) showed no changes in pro-inflammatory cytokine production after 1 day at high-altitude. However, by day three pro-inflammatory cytokine production in response to LPS decreased significantly. These results indicate that high-altitude exposure may initiate an inflammatory response that encompasses innate immune sensitization, with adaptive immune suppression following acclimatization.

Tile: Construction of a specific nanoprobe for scavenging ROS in hypobaric hypoxia induced brain injury of mice

The prevention and treatment of hypobaric hypoxia brain injury (HHBI) remains an unprecedented challenge due to the complex oxidative stress response at the damage site. In this study, RuCO phthalocyanine compound (RuPc) and bovine serum albumin (BSA) were self-assembled to obtain RuPc-BSA nanoparticles for HHBI therapy. As a nanoprobe carrying and storing carbon monoxide (CO), RuPc-BSA delivers CO to pathologically damaged areas of the brain. CO specifically attaches itself to the heme functional groups on mitochondria and restricts the source of reactive oxygen species (ROS) generation. RuPc-BSA nanoparticles have been demonstrated in vitro to exhibit amazing stability as well as remarkable scavenging activity on hydroxyl radical, superoxide anion, and hydrogen peroxide. In vivo experiments showed that ROS levels in the brain of HHBI rats pretreated with RuPc-BSA decreased significantly, and neuronal function and oxidative stress levels were alleviated. Western blot and qRT-RCR results indicated that RuPc-BSA restricted the protein levels of Keap1, whereas enhanced the gene and protein levels of Nrf2. This study demonstrated that RuPc-BSA can ameliorate HHBI of mice by scavenging ROS partly via activating Keap1/Nrf2 signaling pathway.

mTOR in the Development of Hypoxic Pulmonary Hypertension Associated with Cardiometabolic Risk Factors

The pathophysiology of pulmonary hypertension is complex and multifactorial. It is a disease characterized by increased pulmonary vascular resistance at the level due to sustained vasoconstriction and remodeling of the pulmonary arteries, which triggers an increase in the mean pulmonary artery pressure and subsequent right ventricular hypertrophy, which in some cases can cause right heart failure. Hypoxic pulmonary hypertension (HPH) is currently classified into Group 3 of the five different groups of pulmonary hypertensions, which are determined according to the cause of the disease. HPH mainly develops as a product of lung diseases, among the most prevalent causes of obstructive sleep apnea (OSA), chronic obstructive pulmonary disease (COPD), or hypobaric hypoxia due to exposure to high altitudes. Additionally, cardiometabolic risk factors converge on molecular mechanisms involving overactivation of the mammalian target of rapamycin (mTOR), which correspond to a central axis in the development of HPH. The aim of this review is to summarize the role of mTOR in the development of HPH associated with metabolic risk factors and its therapeutic alternatives, which will be discussed in this review.

Is it Possible for Individuals with Pre-Existing Mental Disorders to Perform Mountain Sports at High Altitude-First Evidence from a Pilot Cross-Sectional Questionnaire Study

Gstir, Claudia, Timo Schurr, Roxana Ehlers, Johannes Burtscher, Barbara Sperner-Unterweger, and Katharina Hüfner. Is it possible for individuals with pre-existing mental disorders to perform mountain sports at high altitude-First evidence from a pilot cross-sectional questionnaire study. High Alt Med Biol. 00:00-00, 2024. Introduction: Mountain sports at high altitude (HA) are gaining increasing popularity, but little is known about the effect of such activities on mental health, despite a great prevalence of mental disorders. Methods: Data were collected using an online self-report questionnaire assessing mental and somatic disorders in individuals performing mountain sports at HA (>2,500 m above sea level [ASL]) as well as their symptom change. Nonparametric tests were used for analyses. Results: 251 individuals without pre-existing disorders (noD), 34 with somatic disorders (somaD), and 38 with mental disorders (mentalD; mainly depressive, eating, and anxiety disorders) participated in this study. Overall, 44.7% of the mentalD group compared with 14.7% of somaD experienced ameliorated symptoms during mountain sports at HA, while 2.6% and 8.8%, respectively, reported a worsening (χ2[2] =8.13, p = 0.017). People in the mentalD compared with somaD group significantly less frequently inform tour partners (41.9% vs. 90.9%; χ2[2]=16.69, p < 0.001) about their condition or consult their physician (2.6% vs. 26.5%; χ2[1]=8.53, p = 0.003) regarding their plans to perform mountain sports at HA. 14.5% of all participants reported mental symptoms at 2,500-3,500 m ASL, 23.5% between >3,500-5,500 m ASL and 31.8% >5,500 m ASL. Conclusion: Individuals with mental disorders often report improved mental health during mountain sports at HA, possibly due to a combination of physical activity, the alpine natural environment, and/or moderate hypoxia. The fact that tour partners and physicians are rarely informed shows the need to reduce the stigma of mental disorders in the mountain sports community. The study was prospectively registered with the German Clinical Trials Registry (DRKS00024949).

Dietary patterns related to attention and physiological function in high-altitude migrants

High altitude exposure negatively affects human attentional function. However, no studies have explored the regulation of attentional and physiological functions from a dietary perspective. A total of 116 Han Chinese students from Tibet University who were born and raised in a plain area and had been living in Tibet for > 2 years were recruited. All participants were male migrants. A food frequency questionnaire, complete blood count, and attention network test were performed on the participants. Pearson's correlation was applied to assess the reliability and validity of the food frequency questionnaire. Principal component analysis was utilized to extract dietary patterns. A linear mixed model was employed to account for individual differences. The results showed that the five main dietary patterns were coarse grain, alcohol, meat, protein, and snacking dietary patterns. Furthermore, individuals who adhered to the coarse grain dietary pattern and had high mean corpuscular hemoglobin showed better attentional performance. Individuals with high alcohol consumption and systemic immune-inflammation index levels exhibited worse attentional performance. These findings imply that high-altitude migrants should include more coarse grains in their daily diet and avoid excessive alcohol consumption to improve attention.

Incidence and risk factors of acute mountain sickness during ascent to Hoh Xil and the physiological responses before and after acclimatization

OBJECTIVES

Ascending to altitudes >2500 m may lead to acute mountain sickness (AMS).

METHODS

The demographics, height, weight, body mass index (BMI), smoking, and alcohol consumption of 104 healthy controls were collected in Chengdu (500 m). Heart rate (HR), saturation of pulse oxygen (SpO2), and AMS-related symptoms were collected in Hoh Xil (4200 m). A headache with Lake Louise score ≥3 was defined as AMS.

RESULTS

The incidence of AMS was 60.58%. AMS group had a lower SpO2 and higher HR than non-AMS group. Alcohol consumption seemed a risk factor for AMS. There was no difference in the BMI, age, height, weight, and smoking between AMS and non-AMS groups. The most common AMS symptom was headache, followed by dyspnea, insomnia, dizziness, lassitude, and anorexia. Women were prone to suffer from dizziness. The value of SpO2 and HR was improved both in AMS and non-AMS groups after hypoxia acclimatization, and the value showed greater improvement in AMS group. Oxygen therapy decreased the AMS-induced tachycardia, which had no any effect on SpO2 and symptom alleviating time.

CONCLUSION

Lower SpO2 and higher HR following exposure to high altitude were associated with AMS susceptibility. The anthropometric data changes were larger in AMS group than non-AMS group before and after hypoxia acclimatization.

TNF-α and RPLP0 drive the apoptosis of endothelial cells and increase susceptibility to high-altitude pulmonary edema

High-altitude pulmonary edema (HAPE) is a fatal threat for sojourners who ascend rapidly without sufficient acclimatization. Acclimatized sojourners and adapted natives are both insensitive to HAPE but have different physiological traits and molecular bases. In this study, based on GSE52209, the gene expression profiles of HAPE patients were compared with those of acclimatized sojourners and adapted natives, with the common and divergent differentially expressed genes (DEGs) and their hub genes identified, respectively. Bioinformatic methodologies for functional enrichment analysis, immune infiltration, diagnostic model construction, competing endogenous RNA (ceRNA) analysis and drug prediction were performed to detect potential biological functions and molecular mechanisms. Next, an array of in vivo experiments in a HAPE rat model and in vitro experiments in HUVECs were conducted to verify the results of the bioinformatic analysis. The enriched pathways of DEGs and immune landscapes for HAPE were significantly different between sojourners and natives, and the common DEGs were enriched mainly in the pathways of development and immunity. Nomograms revealed that the upregulation of TNF-α and downregulation of RPLP0 exhibited high diagnostic efficiency for HAPE in both sojourners and natives, which was further validated in the HAPE rat model. The addition of TNF-α and RPLP0 knockdown activated apoptosis signaling in endothelial cells (ECs) and enhanced endothelial permeability. In conclusion, TNF-α and RPLP0 are shared biomarkers and molecular bases for HAPE susceptibility during the acclimatization/adaptation/maladaptation processes in sojourners and natives, inspiring new ideas for predicting and treating HAPE.

Incidence and risk factors of severe acute high-altitude illness in healthy adults first entering the northern Tibetan Plateau of over 5,000 m

Background

Our study was designed to determine the incidence and risk factors of severe acute high-altitude illness (AHAI) in healthy adults first entering the northern Tibetan Plateau of over 5,000 m.

Methods

In our prospective observational study, we enrolled 500 people who were scheduled for fast ascension to the northern Tibetan Plateau. The primary outcome variable was severe AHAI, defined as the presence of serious symptoms that could not be ameliorated by general treatment and required evacuation to lower altitudes. According to the inclusion and exclusion criteria, a cohort of 383 healthy people was included in the statistical analysis. We calculated the incidence of severe AHAI, identified the risk factors, and the differences in the most severe symptoms experienced.

Results

Sixty-eight people were diagnosed with severe AHAI, and the incidence was 17.8%. Compared to individuals without severe AHAI, those with severe AHAI were more likely to be over the age of 40 years, of Han Chinese nationality, and living at an altitude of <1,500 m. They were less likely to belong to the Yi nationality, had a lower altitude of permanent residence, and exhibited decreased levels of lymphocyte count and hemoglobin concentration. Multivariable logistic regression showed that the mean altitude of permanent residence [per kilometer, adjusted odds ratio (AOR) = 0.464; 95% confidence interval (CI), 0.304-0.708; p < 0.001] and lymphocyte count (AOR = 0.606; 95% CI, 0.378-0.970; p = 0.037) were the independent risk factors. Headache and dyspnea ranked in the top two of the most severe symptoms for people with severe AHAI.

Conclusion

Living at lower altitudes and having a decreased lymphocyte level were the risk factors of severe AHAI in healthy adults first entering the plateau of over 5,000 m.

Assessment of Acute Mountain Sickness: Comparing the Chinese AMS Score to the Lake Louise Score

Wu, Yu, Wenqi Zhao, Bao Liu, Jianyang Zhang, Zhifeng Zhong, Simin Zhou, Jiaxin Xie, Yuqi Gao, Peng Li, and Jian Chen. Assessment of Acute Mountain Sickness: Comparing the Chinese Ams Score to the Lake Louise Score. High Alt Med Biol 25:164-173, 2024. Objective: To compare the ability of the Chinese AMS Score (CAS) to detect acute mountain sickness (AMS) using the 2018 version of the Lake Louise Score (LLS) as reference. Methods: After flying from Chengdu (altitude: 500 m) to Lhasa (3,658 m), 2,486 young men completed a questionnaire. The questionnaire contained LLS and CAS items. An LLS ≥3 and/or a CAS ≥cutoff were used as the criteria for AMS. Hierarchical cluster analysis and two-step cluster analysis were used to investigate relationships between the symptoms. Results: AMS incidence rates were 33.8% (n = 840) with the LLS and 59.3% (n = 1,473) with the CAS (χ2 = 872.5, p < 0.001). The LLS and CAS had a linear relationship (orthogonal regression, Pearson r = 0.91, p < 0.001). With the LLS as the standard, the CAS had high diagnostic accuracy (area under the curve = 0.95, 95% confidence interval: 0.94-0.96). However, with the CAS, 25.5% (n = 633) more participants were labeled as having AMS than with the LLS (false positives). Two clusters were identified: one with headache only (419 participants, 66.2%) and one without headache but with other symptoms (214 participants, 33.8%). Reducing the weight of headache in the CAS allowed to align CAS and LLS. Conclusion: In comparison to the LLS, the CAS has a sensitivity close to 100% but lacks specificity given the high rate of false positives. The different weight of headaches may be the main reason for the discrepancy.

Remote ischemic preconditioning prevents high-altitude cerebral edema by enhancing glucose metabolic reprogramming

AIMS

Incidence of acute mountain sickness (AMS) ranges from 40%-90%, with high-altitude cerebral edema (HACE) representing a life-threatening end stage of severe AMS. However, practical and convenient preventive strategies for HACE are lacking. Remote ischemic preconditioning (RIPC) has demonstrated preventive effects on ischemia- or hypoxia-induced cardiovascular and cerebrovascular diseases. This study aimed to investigate the potential molecular mechanism of HACE and the application of RIPC in preventing HACE onset.

METHODS

A hypobaric hypoxia chamber was used to simulate a high-altitude environment of 7000 meters. Metabolomics and metabolic flux analysis were employed to assay metabolite levels. Transcriptomics and quantitative real-time PCR (q-PCR) were used to investigate gene expression levels. Immunofluorescence staining was performed on neurons to label cellular proteins. The fluorescent probes Mito-Dendra2, iATPSnFR1.0, and CMTMRos were used to observe mitochondria, ATP, and membrane potential in cultured neurons, respectively. TUNEL staining was performed to detect and quantify apoptotic cell death. Hematoxylin and eosin (H&E) staining was utilized to analyze pathological changes, such as tissue swelling in cerebral cortex samples. The Rotarod test was performed to assess motor coordination and balance in rats. Oxygen-glucose deprivation (OGD) of cultured cells was employed as an in vitro model to simulate the hypoxia and hypoglycemia induced by RIPC in animal experiments.

RESULTS

We revealed a causative perturbation of glucose metabolism in the brain preceding cerebral edema. Ischemic preconditioning treatment significantly reprograms glucose metabolism, ameliorating cell apoptosis and hypoxia-induced energy deprivation. Notably, ischemic preconditioning improves mitochondrial membrane potential and ATP production through enhanced glucose-coupled mitochondrial metabolism. In vivo studies confirm that RIPC alleviates cerebral edema, reduces cell apoptosis induced by high-altitude hypoxia, and improves motor dysfunction resulting from cerebral edema.

CONCLUSIONS

Our study elucidates the metabolic basis of HACE pathogenesis. This study provides a new strategy for preventing HACE that RIPC reduces brain edema through reprogramming metabolism, highlighting the potential of targeting metabolic reprogramming for neuroprotective interventions in neurological diseases caused by ischemia or hypoxia.

Is Smoking Associated with the Risk of Acute Mountain Sickness? A Systematic Review and Meta-Analysis

Background: Controversy remains in the association between smoking and the risk of acute mountain sickness (AMS). Therefore, a systematic review of the existing literature may help clarify this association. Methods: We conducted a systematic search of PubMed, Embase, and Cochrane Library from database inception up to October 19, 2021. Both unadjusted and adjusted relative risks (RRs) and 95% confidence intervals (CIs) were calculated to compare the risk of AMS in the smoking and nonsmoking groups. Meta-regression was conducted to explore the factors causing heterogeneity of the studies, and subsequent stratified analysis was performed to present the pooled RR in different subgroups. Publication bias was assessed using funnel plots. Results: A total of 28 eligible articles (31 studies) were included. The pooled unadjusted and adjusted RRs were 0.88 (95% CI: 0.78-1.01) and 0.87 (95% CI: 0.77-0.99), respectively, using random-effect models. Publication bias was observed owing to restrictions on the sample size. The ascending altitude and sex composition of the study population were likely sources of heterogeneity according to meta-regression. Studies on participants with an ascending altitude of over 3,500 m or composed of both males and females reported a slight but not significant protective effect of smoking on the risk of AMS, with high heterogeneity. Conclusions: Smoking had no significant effect on AMS risk in this meta-analysis. Current studies showed high heterogeneity and included little information on quantitative exposure to smoking (i.e., dose and frequency); thus, the results require careful explanation.

Ssc-miR-101-3p inhibits hypoxia-induced apoptosis and inflammatory response in alveolar type-II epithelial cells of Tibetan pigs via targeting FOXO3

Tibetan pigs are a unique swine strain adapted to the hypoxic environment of the plateau regions in China. The unique mechanisms underlying the adaption by Tibetan pigs, however, are still elusive. Only few studies have investigated hypoxia-associated molecular regulation in the lung tissues of animals living in the plateau region of China. Our previous study reported that ssc-miR-101-3p expression significantly differed in the lung tissues of Tibetan pigs at different altitudes, suggesting that ssc-miR-101-3p plays an important role in the adaptation of Tibetan pigs to high altitude. To understand the underlying molecular mechanism, in this study, the target genes of ssc-miR-101-3p and their functions were analyzed via various methods including qRT-PCR and GO and KEGG pathway enrichment analyses. The action of ssc-miR-101-3p was investigated by culturing alveolar type-II epithelial cells (ATII) of Tibetan pigs under hypoxic conditions and transfecting ATII cells with vectors overexpressing or inhibiting ssc-miR-101-3p. Overexpression of ssc-miR-101-3p significantly increased the proliferation of ATII cells and decreased the expression of inflammatory and apoptotic factors. The target genes of ssc-miR-101-3p were significantly enriched in FOXO and PI3K-AKT signaling pathways required to mitigate lung injury. Further, FOXO3 was identified as a direct target of ssc-miR-101-3p. Interestingly, ssc-miR-101-3p overexpression reversed the damaging effect of FOXO3 in the ATII cells. In conclusion, ssc-miR-101-3p targeting FOXO3 could inhibit hypoxia-induced apoptosis and inflammatory response in ATII cells of Tibetan pigs. These results provided new insights into the molecular mechanisms elucidating the response of lung tissues of Tibetan pigs to hypoxic stress.

Key Genes FECH and ALAS2 under Acute High-Altitude Exposure: A Gene Expression and Network Analysis Based on Expression Profile Data

High-altitude acclimatization refers to the physiological adjustments and adaptation processes by which the human body gradually adapts to the hypoxic conditions of high altitudes after entering such environments. This study analyzed three mRNA expression profile datasets from the GEO database, focusing on 93 healthy residents from low altitudes (≤1400 m). Peripheral blood samples were collected for analysis on the third day after these individuals rapidly ascended to higher altitudes (3000-5300 m). The analysis identified significant differential expression in 382 genes, with 361 genes upregulated and 21 downregulated. Further, gene ontology (GO) annotation analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis indicated that the top-ranked enriched pathways are upregulated, involving blood gas transport, erythrocyte development and differentiation, and heme biosynthetic process. Network analysis highlighted ten key genes, namely, SLC4A1, FECH, EPB42, SNCA, GATA1, KLF1, GYPB, ALAS2, DMTN, and GYPA. Analysis revealed that two of these key genes, FECH and ALAS2, play a critical role in the heme biosynthetic process, which is pivotal in the development and maturation of red blood cells. These findings provide new insights into the key gene mechanisms of high-altitude acclimatization and identify potential biomarkers and targets for personalized acclimatization strategies.

Assessment of Dynamic Cerebral Autoregulation During Long-Term Exposure to High Altitude in Normal Subjects by Ultrasonography

PURPOSE

To evaluate changes in dynamic cerebral autoregulation (CA) during short-term and long-term exposure to high altitude with ultrasonography, and also study the sex differences in the response of CA to altitude.

METHODS

We assessed the differences in dynamic CA and measured with Doppler ultrasound of the bilateral internal carotid artery (ICA), vertebral artery (VA), and middle cerebral artery (MCA) and the values of basic information within 48 hours and at 2 years after arrival at Tibet in 65 healthy Han young Chinese volunteers, meanwhile, we compared the resistance index (RI) and pulsatility index (PI) of the right MCA at inhale oxygen 8 minutes when a newcomer with 2 years after arrival at Tibet.

RESULTS

With 2 years of altitude exposure, the SaO2 of all subjects was above 90%, the mean PEF, DAP, and HR values decreased, HGB increased compared within 48 hours in same-gender groups. Comparisons of cerebral hemodynamics between before 2 years and after 2 years within male and female groups, the mean RI and PI values of bilateral MCA after 2 years were significantly higher than before 2 years, at the same time, the mean RI and PI values of bilateral ICA were significant differences (P < .05) between male groups, with regard to female groups, showed that the mean RI and PI values of bilateral VA were significant differences (P < .05). Comparisons of Right MCA hemodynamics between after oxygen uptake 8 minutes and 2 years, the mean RI and PI values were no significant difference within male and female groups (P > .05).

CONCLUSIONS

Acute mountain sickness could result from an alteration of dynamic autoregulation of cerebral blood flow, but the impaired autoregulation may be corrected with the extension of time, furthermore, the response of CA to altitude in males and females are different.

High-altitude Cerebral Edema and High-altitude Pulmonary Edema Diagnosed in the Desert: A Case Report

Introduction

Acute mountain sickness, high-altitude pulmonary edema (HAPE), and high-altitude cerebral edema (HACE) are a spectrum of high-altitude conditions, with HACE being the most life-threatening. Most cases develop at altitudes of greater than 4,000 meters (∼13,000 feet) above sea level and after one to five days.

Case Report

A previously healthy 46-year-old female presented to the emergency department with ataxia, altered mental status, and vomiting that developed after rapidly ascending to ∼2,400 meters (∼7,800 feet) above sea level. She was treated for HACE and HAPE with resolution of her symptoms within 24 hours.

Conclusion

High-altitude pulmonary edema and HACE can develop rapidly and at moderate altitudes. Expeditious recognition and treatment is imperative to avoid life-threatening complications.

Intermittent high altitude hypoxia induced liver and kidney injury leading to hyperuricemia

About 140 million people worldwide live at an altitude above 2500 m. Studies have showed an increase of the incidence of hyperuricemia among plateau populations, but little is known about the possible mechanisms. This study aims to assess the effects of high altitude on hyperuricemia and explore the corresponding mechanisms at the histological, inflammatory and molecular levels. This study finds that intermittent hypobaric hypoxia (IHH) exposure results in an increase of serum uric acid level and a decrease of uric acid clearance rate. Compared with the control group, the IHH group shows significant increases in hemoglobin concentration (HGB) and red blood cell counts (RBC), indicating that high altitude hyperuricemia is associated with polycythemia. This study also shows that IHH exposure induces oxidative stress, which causes the injury of liver and renal structures and functions. Additionally, altered expressions of organic anion transporter 1 (OAT1) and organic cation transporter 1 (OCT1) of kidney have been detected in the IHH exposed rats. The adenosine deaminase (ADA) expression levels and the xanthione oxidase (XOD) and ADA activity of liver of the IHH exposure group have significantly increased compared with those of the control group. Furthermore, the spleen coefficients, IL-2, IL-1β and IL-8, have seen significant increases among the IHH exposure group. TLR/MyD88/NF-κB pathway is activated in the process of IHH induced inflammatory response in joints. Importantly, these results jointly show that IHH exposure causes hyperuricemia. IHH induced oxidative stress along with liver and kidney injury, unusual expression of the uric acid synthesis/excretion regulator and inflammatory response, thus suggesting a potential mechanism underlying IHH-induced hyperuricemia.

Global profiling of protein lactylation in microglia in experimental high-altitude cerebral edema

BACKGROUND

High-altitude cerebral edema (HACE) is considered an end-stage acute mountain sickness (AMS) that typically occurs in people after rapid ascent to 2500 m or more. While hypoxia is a fundamental feature of the pathophysiological mechanism of HACE, emerging evidence suggests that inflammation serves as a key risk factor in the occurrence and development of this disease. However, little is known about the molecular mechanism underlying their crosstalk.

METHODS

A mouse HACE model was established by combination treatment with hypobaric hypoxia exposure and lipopolysaccharides (LPS) stimulation. Lactylated-proteomic analysis of microglia was performed to reveal the global profile of protein lactylation. Molecular modeling was applied to evaluate the 3-D modeling structures. A combination of experimental approaches, including western blotting, quantitative real-time reverse transcriptionpolymerase chain reaction (qRT-PCR), and enzyme-linked immunosorbent assay (ELISA), confocal microscopy and RNA interference, were used to explore the underlying molecular mechanisms.

RESULTS

We found that hypoxia exposure increased the lactate concentration and lactylation in mouse HACE model. Moreover, hypoxia aggravated the microglial neuroinflammatory response in a lactate-dependent manner. Global profiling of protein lactylation has shown that a large quantity of lysine-lactylated proteins are induced by hypoxia and preferentially occur in protein complexes, such as the NuRD complex, ribosome biogenesis complex, spliceosome complex, and DNA replication complex. The molecular modeling data indicated that lactylation could affect the 3-D theoretical structure and increase the solvent accessible surface area of HDAC1, MTA1 and Gatad2b, the core members of the NuRD complex. Further analysis by knockdown or selectively inhibition indicated that the NuRD complex is involved in hypoxia-mediated aggravation of inflammation.

CONCLUSIONS

These results revealed a comprehensive profile of protein lactylation in microglia and suggested that protein lysine lactylation plays an important role in the regulation of protein function and subsequently contributes to the neuroinflammatory response under hypoxic conditions.

Ginsenosides ameliorates high altitude-induced hypoxia injury in lung and kidney tissues by regulating PHD2/HIF-1α/EPO signaling pathway

Background: The primary constituent of ginseng, known as ginsenosides (GS), has been scientifically demonstrated to possess anti-fatigue, anti-hypoxia, anti-inflammatory, and antioxidant properties. However, the effect and mechanisms of GS on tissue injury induced by high-altitude hypoxia still remain unclear. Aim of the study: This study aims to investigate the protective effect of GS on a high-altitude hypoxia model and explore its mechanism. Materials and methods: Sprague-Dawley rats were placed in a high-altitude simulation chamber for 48 h (equivalent to an altitude of 6,000 m) to establish a high-altitude hypoxia model. We assessed the anti-hypoxic efficacy of GS through blood gas analysis, complete blood count, and hemorheology analysis. We used H&E and hypoxia probe assays to evaluate the protective effect of GS on organ ischemia-induced injury. Further, we used ELISA and qPCR analysis to detect the levels of inflammatory factors and oxidative stress markers. Immunohistochemistry and immunofluorescence staining were performed to determinate protein expression of hypoxia inducible factor 1-alpha (HIF-1α), erythropoietin (EPO), and prolyl hydroxylase 2 (PHD2). Results: In the survival experiment of anoxic mice, 100 mg/kg of GS had the best anti-anoxic effect. GS slowed down the weight loss rate of rats in hypoxic environment. In the fluorescence detection of hypoxia, GS reduced the fluorescence signal value of lung and kidney tissue and alleviated the hypoxia state of tissue. Meanwhile GS improved blood biochemical and hematological parameters. We also observed that GS treatment significantly decreased oxidative stress damage in lung and kidney tissues. Further, the levels of inflammatory factors, IL-1β, IL-6, and TNF-α were reduced by GS. Finally, GS regulated the PHD2/HIF-1α/EPO signaling pathway to improve blood viscosity and tissue hyperemia damage. Conclusion: GS could alleviate high-altitude induced lung and kidney damage by reducing the level of inflammation and oxidative stress, improving blood circulation through the PHD2/HIF-1α/EPO pathway.

Reversible leukoencephalopathy with seizures: a case of severe high-altitude cerebral edema

BACKGROUND

Acute high-altitude illness (AHAI) refers to a series of syndromes including acute mountain sickness (AMS), high-altitude pulmonary edema (HAPE) and high-altitude cerebral edema (HACE). Among these, HACE is a severe and potentially life-threatening condition that can occur when individuals ascend to high altitudes. It is often characterized by ataxia, confusion, and altered mental status. Without appropriate treatment, HACE can rapidly progress to coma, but seizures are infrequent in occurrence.

CASE PRESENTATION

Here, we report a severe HACE patient with coma and status epilepticus. The patient is a 23-year-old male who was visiting Lhasa for the first time. He initially experienced headaches and dizziness on the first day, and then he was found in coma with limb convulsions on the next day. Immediate medical attention was sought, and brain CT and MRI scans showed reversible white matter lesions, especially in the corpus callosum and subcortical white matter. Although the lesions disappeared on T1 and T2 sequences, microbleeds were observed on the SWI sequence. After treatment with tracheal intubation, glucocorticoids and hyperbaric oxygen, the cerebral edema has resolved and the clinical symptoms improved, the patient has no seizures anymore.

CONCLUSIONS

HACE typically follows AMS and poses a significant risk to life. Clinical manifestations mainly include ataxia, alterations of behavior, and impaired consciousness, with severe cases progressing to coma. Seizures, though rarely observed, may occur. Imaging shows reversible white matter lesions, with microbleeds being a significant and persistent imaging marker over time. Administration of glucocorticoids plays a crucial role in treatment. Despite experiencing seizures, this patient did not experienced any further episodes once his condition improved.

Hypoxia-Induced Pulmonary Injury-Adrenergic Blockade Attenuates Nitrosative Stress, and Proinflammatory Cytokines but Not Pulmonary Edema

Hypoxia can induce pulmonary edema (PE) and inflammation. Furthermore, hypoxia depresses left ventricular (LV) inotropy despite sympathetic activation. To study the role of hypoxic sympathetic activation, we investigated the effects of hypoxia with and without adrenergic blockade (AB) on cardiovascular dysfunction and lung injury, i.e., pulmonary edema, congestion, inflammation, and nitrosative stress. Eighty-six female rats were exposed for 72 h to normoxia or normobaric hypoxia and received infusions with NaCl, prazosin, propranolol, or prazosin-propranolol combination. We evaluated hemodynamic function and performed histological and immunohistochemical analyses of the lung. Hypoxia significantly depressed LV but not right ventricular (RV) inotropic and lusitropic functions. AB significantly decreased LV function in both normoxia and hypoxia. AB effects on RV were weaker. Hypoxic rats showed signs of moderate PE and inflammation. This was accompanied by elevated levels of tumor necrosis factor α (TNFα) and nitrotyrosine, a marker of nitrosative stress in the lungs. In hypoxia, all types of AB markedly reduced both TNFα and nitrotyrosine. However, AB did not attenuate PE. The results suggest that hypoxia-induced sympathetic activation contributes to inflammation and nitrosative stress in the lungs but not to PE. We suggest that AB in hypoxia aggravates hypoxia-induced inotropic LV dysfunction and backlog into the pulmonary circulation, thus promoting PE.

Recent advances in predicting acute mountain sickness: from multidimensional cohort studies to cutting-edge model applications

High-altitude illnesses, encompassing a spectrum of health threats including Acute Mountain Sickness (AMS), pose significant challenges to individuals exposed to high altitude environments, necessitating effective prophylaxis and immediate management. Given the variability in individual responses to these conditions, accurate prediction of high-altitude illnesses onset is of paramount importance. This review systematically consolidates recent advancements in research on predicting AMS by evaluating existing cohort data, predictive models, and methodologies, while also delving into the application of emerging technologies. Through a thorough analysis of scholarly literature, we discuss traditional prediction methods anchored in physiological parameters (e.g., heart rate, respiratory frequency, blood pressure) and biochemical markers, as well as the integration and utility of novel technologies such as biosensors, genetic testing, and artificial intelligence within high-altitude prediction research. While conventional pre-diction techniques have been extensively used, they are often constrained by limitations in accuracy, reliability, and multifactorial influences. The advent of these innovative technologies holds promise for more precise individual risk assessments and personalized preventive and therapeutic strategies across various forms of AMS. Future research endeavors must pivot decisively towards the meticulous identification and stringent validation of innovative predictive biomarkers and models. This strategic re-direction should catalyze intensified interdisciplinary cooperation to significantly deepen our mechanistic insights into the pathogenesis of AMS while refining existing prediction methodologies. These groundbreaking advancements harbor the potential to fundamentally transform preventive and therapeutic frameworks for high-altitude illnesses, ultimately securing augmented safety standards and wellbeing for individuals operating at elevated altitudes with far-reaching global implications.

Altitude illnesses

Millions of people visit high-altitude regions annually and more than 80 million live permanently above 2,500 m. Acute high-altitude exposure can trigger high-altitude illnesses (HAIs), including acute mountain sickness (AMS), high-altitude cerebral oedema (HACE) and high-altitude pulmonary oedema (HAPE). Chronic mountain sickness (CMS) can affect high-altitude resident populations worldwide. The prevalence of acute HAIs varies according to acclimatization status, rate of ascent and individual susceptibility. AMS, characterized by headache, nausea, dizziness and fatigue, is usually benign and self-limiting, and has been linked to hypoxia-induced cerebral blood volume increases, inflammation and related trigeminovascular system activation. Disruption of the blood-brain barrier leads to HACE, characterized by altered mental status and ataxia, and increased pulmonary capillary pressure, and related stress failure induces HAPE, characterized by dyspnoea, cough and exercise intolerance. Both conditions are progressive and life-threatening, requiring immediate medical intervention. Treatment includes supplemental oxygen and descent with appropriate pharmacological therapy. Preventive measures include slow ascent, pre-acclimatization and, in some instances, medications. CMS is characterized by excessive erythrocytosis and related clinical symptoms. In severe CMS, temporary or permanent relocation to low altitude is recommended. Future research should focus on more objective diagnostic tools to enable prompt treatment, improved identification of individual susceptibilities and effective acclimatization and prevention options.