Pathophysiology and Therapy of High-Altitude Sickness: Practical Approach in Emergency and Critical Care

Pain Perception Threshold in Young High-Altitude Natives After Acute Exposure to Severe Hypoxic Conditions

Previous studies indicate that individuals at high altitudes have a lower pain threshold than those living at sea level. This study evaluates the differences in pain perception among young people living at an altitude of 3800 m and after acute exposure to a severe hypoxic environment at more than 5100 m. Fourteen people (BMI of 22.6 ± 1.2 and age of 23.3 ± 1.9 years) residing in the city of Puno (3825 m) participated in an ascent to the Populated Center of La Rinconada (>5100 m). The unilateral ischemia pain provocation test was used, applying pressure with a manual sphygmomanometer to generate transient ischemia in the arm while the patient opens and closes their hand. Onset, peak, and resolution times of pain, heart rate, and oxygen saturation were recorded. At their residence altitude of 3828 m, the mean hemoglobin was 16.16 ± 2.29, while at 5100 m, mean hemoglobin increased to 17.57 ± 1.74. The average time to pain onset in the right arm was 30.43 s ± 14.15 at 3828 m, whereas at 5100 m above sea level, the pain perception was at 31.00 s ± 19.01. At 3828 m, the average time until pain sensation in the left arm was 19.93 s ± 9.44 and increased to 23.07 s ± 10.83 at 5100 m. During exposure to a severe hypoxic environment, the pain perception threshold was similar between 3828 m and 5100 m above sea level.

The Role of Hypoxia in Longevity

Aging is marked by a progressive decrease in physiological function and reserve capacity, which results in increased susceptibility to diseases. Understanding the mechanisms of driving aging is crucial for extending health span and promoting human longevity. Hypoxia, marked by reduced oxygen availability, has emerged as a promising area of study within aging research. This review explores recent findings on the potential of oxygen restriction to promote healthy aging and extend lifespan. While the role of hypoxia-inducible factor 1 (HIF-1) in cellular responses to hypoxia is well-established, its impact on lifespan remains complex and context-dependent. Investigations in invertebrate models suggest a role for HIF-1 in longevity, while evidence in mammalian models is limited. Hypoxia extends the lifespan independent of dietary restriction (DR), a known intervention underlying longevity. However, both hypoxia and DR converge on common downstream effectors, such as forkhead box O (FOXO) and flavin-containing monooxygenase (FMOs) to modulate the lifespan. Further work is required to elucidate the molecular mechanisms underlying hypoxia-induced longevity and optimize clinical applications. Understanding the crosstalk between HIF-1 and other longevity-associated pathways is crucial for developing interventions to enhance lifespan and healthspan. Future studies may uncover novel therapeutic strategies to promote healthy aging and longevity in human populations.

Risk factors associated with high altitude sickness among travelers: A case control study in Himalaya district of Nepal

High elevation adventures are popular among travelers; however, they carry significant health risks, such as altitude sickness. This study aims to identify risk factors associated with high altitude sickness among travelers to Mustang district. A health-facility-based, age-sex matched 1:1 case-control study was conducted in Mustang district hospital, Nepal. Measurements included Acute Mountain Sickness/High Altitude Cerebral Edema/High Altitude Pulmonary Edema assessment via LLS questionnaire, demographics, medical history, ascent rate, and prophylactic medicine intake. Data were collected between September and November, 2023 via predesigned structured questionnaire by trained medical officers in, and analyzed using SPSS version 25. Using binary logistic regression, the study tested potential risk factors associated with altitude sickness. Ethical approval was obtained from the NHRC, and written informed consent was obtained from all participants. A total of 63 cases (individuals with altitude sickness) and 63 controls (without) were interviewed. The mean age of cases and controls was 48.5 years (SD = 16.5) and 48 years (SD = 16.9) respectively. 38 were rapid ascenders, and 88 were slow ascenders. Awareness of altitude sickness was reported by 65 individuals, with 36 taking prophylactic medication (Acetazolamide 125/250mg). Among cases, 8 experienced HACE, 42 had AMS, and 13 had HAPE. Rapid ascent (Adjusted Odds Ratio [AOR]: 6.41, 95% Confidence Interval [CI]: 2.36-17.54), individuals with a previous history of illness (AOR: 10.20, 95% CI: 2.70-38.46), and failing to take prophylactic medication (AOR: 10.01, 95% CI: 1.896-10.680) were linked to an increased risk of altitude sickness. Our study highlights the critical role of ascent speed, previous history of illness, and use of prophylactic measures in development of altitude sickness.

Impact of Low Altitude-Hilly Terrain on Pulmonary Health in Young Adults: A Gender-Based Spirometric Analysis

Introduction

This study explores the pulmonary function of young adults living in hilly terrains at low altitudes (around 1,800 ft), assessing the impact of elevation on lung health and potential gender-based differences using digital spirometry.

Materials and Methods

Pulmonary functions, including forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), FEV1/FVC ratio, and peak expiratory flow rate, were measured in individuals aged 18-24 years. Differences between males and females were examined using independent t-tests and Pearson correlation tests to analyze the relationships between various pulmonary metrics.

Results

Males demonstrated higher mean values in FVC and FEV1 compared to females, though the FEV1/FVC ratio remained consistent across genders. Correlation analysis within the total sample and across genders revealed significant relationships among the tests.

Conclusion

The study highlights low altitude's physiological effects on lung function, with gender differences in pulmonary findings. These findings necessitate gender-specific approaches in health interventions and emphasize the importance of altitude consideration in respiratory health research.

[Status of Research on Molecular Mechanisms and Management of Acute Mountain Sickness]

Acute mountain sickness (AMS), a condition characterized primarily by symptoms such as headache and nausea, has a high incidence and seriously affects the life and health of individuals undertaking rapid ascensions to high altitudes. The main pathophysiological manifestations of AMS include cerebral vasodilation and transient increases in intracranial pressure, with severe cases potentially incurring cerebral edema. The occurrence and development of AMS is associated with factors such as the susceptibility, physiological state, and psychological state of an individual. The molecular mechanisms involved include inflammatory responses, oxidative stress, immune regulation, and energy metabolism at the levels of genes, proteins, and metabolism. The management of AMS includes both prevention and treatment strategies. This article provides a comprehensive discussion of AMS from several aspects, including diagnosis, pathophysiological manifestations, susceptibility factors, molecular mechanisms, and prevention and treatment strategies.

Evaluation of the cell death markers for aberrated cell free DNA release in high altitude pulmonary edema

The effect of high altitude (HA, altitude >2500 m) can trigger a maladaptive response in unacclimatized individuals, leading to various HA illnesses such as high altitude pulmonary edema (HAPE). The present study investigates circulating cell free (cf) DNA, a minimally invasive biomarker that can elicit a pro-inflammatory response. Our earlier study observed altered cfDNA fragment patterns in HAPE patients and the significant correlation of these patterns with peripheral oxygen saturation levels. However, the unclear release mechanisms of cfDNA in circulation limit its characterization and clinical utility. The present study not only observed a significant increase in cfDNA levels in HAPE patients (27.03 ± 1.37 ng/ml; n = 145) compared to healthy HA sojourners (controls, 14.57 ± 0.74 ng/ml; n = 65) and highlanders (HLs, 15.50 ± 0.8 ng/ml; n = 34) but also assayed the known cell death markers involved in cfDNA release at HA. The study found significantly elevated levels of the apoptotic marker, annexin A5, and secondary necrosis or late apoptotic marker, high mobility group box 1, in HAPE patients. In addition, we observed a higher oxidative DNA damage marker, 8-hydroxy-2'-deoxyguanosine, in HAPE compared with controls, suggestive of the role of oxidative DNA status in promoting the inflammatory potential of cfDNA fragments and their plausible role in manifesting HAPE pathophysiology. Extensive in vitro future assays can confirm the immunogenic role of cfDNA fragments that may act as a danger-associated molecular pattern and associate with markers of cellular stresses in HAPE.

Glucose deprivation impairs hypoxia-inducible factor-1α synthesis

Hypoxia-inducible factors (HIFs) are key transcriptional mediators of the hypoxic response and are implicated in oncogenesis. HIFα is regulated by a well-characterized, oxygen-dependent degradation pathway involving the von Hippel Lindau (VHL) tumor suppressor protein. However, comparatively little is known about HIFα regulation at the translational level, particularly under cellular stress. There is evidence that HIFα expression not only responds to changes in oxygen tension, but also nutrient availability. In this study, we monitored global translation rates, ATP levels and HIF1α synthesis rates in response to glucose starvation or glycolysis inhibition. We found that both global and HIF1α-specific translation rates decline under glucose deprivation that is concomitant with ATP reduction. These results are in contrast with previous reports showing preferential HIF1α synthesis despite global translation suppression under hypoxia and suggest that a glucose requirement in cellular metabolism is associated with HIF1α translation.

Effect of nitrate supplementation on oxygen saturation levels for acute mountain sickness prevention: A systematic review and meta-analysis

PURPOSE

This study aimed to systematically review the effect of nitrate supplementation on blood oxygen saturation.

METHODS

We searched PubMed, Scopus, and Cochrane Library databases from their inception up to October 2022. Two reviewers independently conducted two stages of the screening process to include a randomized controlled trial with nitrate supplementation versus placebo intervention assessing oxygen saturation among lowlanders going to either real or simulated high altitude environments. We used the Cochrane Risk of Bias 2.0 tool to assess the risk of bias in the included studies. Fixed-effect model meta-analyses were conducted for laboratory-based studies. Random-effect meta-analyses were conducted for real-world studies.

RESULTS

We found 7 trials that met the eligibility criteria. A meta-analysis of studies with some bias concerns showed an increase of 1.26 % in the SpO2 with 44 % I2 during submaximal exercise at simulated high altitudes (GRADE: low). On the contrary, a meta-analysis of studies without heterogeneity showed that nitrate supplementation aggravated oxygen saturation decline (-2.64 %, p = 0.03, GRADE: high) during rest in real high-altitude environments. A meta-analysis also showed that nitrate supplementation did not affect Acute Mountain Sickness (AMS) symptoms (GRADE: high).

CONCLUSION

Our results suggest that nitrate supplementation did not provide benefits for AMS prevention during rest at high altitudes. The low-quality evidence showing small beneficial effects of nitrate supplementation during exercise calls for further studies.

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.

Emergency Care for High-Altitude Trekking and Climbing

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.

Preliminary study of identified novel susceptibility loci for HAPE risk in a Chinese male Han population

High altitude pulmonary edema (HAPE) is a life-threatening form of non-cardiogenic pulmonary edema. In recent years, association studies have become the main method for identifying HAPE genetic loci. A genome-wide association study (GWAS) of HAPE risk-associated loci was performed in Chinese male Han individuals (164 HAPE cases and 189 healthy controls) by the Precision Medicine Diversity Array Chip with 2,771,835 loci (Applied Biosystems Axiom™). Eight overlapping candidate loci in CCNG2, RP11-445O3.2, NUPL1 and WWOX were finally selected. In silico functional analyses displayed the PPI network, functional enrichment and signal pathways related to CCNG2, NUPL1, WWOX and NRXN1. This study provides data supplements for HAPE susceptibility gene loci and new insights into HAPE susceptibility.

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.

Polysaccharides from Brassica rapa root: Extraction, purification, structural features, and biological activities. A review

Brassica rapa (B. rapa) roots are attracting increased attention from nutritionists and health-conscious customers because of their remarkable performance in supplying necessary nutrients. Polysaccharides are major biologically active substances in B. rapa roots, which come in a variety of monosaccharides with different molar ratios and glycosidic bond types. Depending on the source, extraction, separation, and purification methods of B. rapa roots polysaccharides (BRP); different structural features, and pharmacological activities are elucidated. Polysaccharides from B. rapa roots possess a range of nutritional, biological, and health-enhancing characteristics, including anti-hypoxic, antifatigue, immunomodulatory, hypoglycemic, anti-tumor, and antioxidant activities. This paper reviewed extraction and purification methods, structural features, and biological activities as well as correlations between the structural and functional characteristics of polysaccharides from the B. rapa roots. Ultimately, this work will serve as useful reference for understanding the connections between polysaccharide structure and biological activity and developing novel BRP-based functional foods.

Progress in the Treatment of High Altitude Cerebral Edema: Targeting REDOX Homeostasis

With the increasing of altitude activities from low-altitude people, the study of high altitude cerebral edema (HACE) has been revived. HACE is a severe acute mountain sickness associated with exposure to hypobaric hypoxia at high altitude, often characterized by disturbance of consciousness and ataxia. As for the pathogenesis of HACE, previous studies suggested that it might be related to the disorder of cerebral blood flow, the destruction of blood-brain barrier and the injury of brain parenchyma cells caused by inflammatory factors. In recent years, studies have confirmed that the imbalance of REDOX homeostasis is also involved in the pathogenesis of HACE, which mainly leads to abnormal activation of microglia and destruction of tight junction of vascular endothelial cells through the excessive production of mitochondrial-related reactive oxygen species. Therefore, this review summarizes the role of REDOX homeostasis and the potential of the treatment of REDOX homeostasis in HACE, which is of great significance to expand the understanding of the pathogenesis of HACE. Moreover, it will also be helpful to further study the possible therapy of HACE related to the key link of REDOX homeostasis.

Metabolites and gene expression in the myocardium of fasting rats in an acute hypoxic environment

With the rising demand for entry to extremely high altitudes (HAs), rapid adaptability to extremely hypoxic environments is a challenge that we need to explore. Fasting was used to evaluate acute hypoxia tolerance at HA and was proven to be an effective method for improving the survival rate at extreme HA. Our experiments also showed that fasting pretreatment for 72 h significantly increased the 24 h survival rate of rats at 7620 m from 10 to 85% and protected the myocardium cells of rats. Here, we compared the metabolites and gene expression in the myocardium of SD rats pretreated with fasting and nonfasting at normal altitude and extreme HA. Our findings demonstrated that the dynamic contents of detected differential metabolites (DMs) between different rat groups were consistent with the expression of differentially expressed genes (DEGs), and DM clusters also showed strong correlations with DEG clusters. DM clusters related to amino acids and lipids were significantly lower in the fasting groups, and the correlated DEG clusters were enriched in mitotic pathways, including CDK1, CDC7, NUF2, and MCM6, suggesting that fasting can attenuate mitotic processes in cardiac tissues and reduce the synthesis of amino acids and lipids. L-Glutamine-related metabolites were particularly low at extreme HA without pretreatment but were normal in the fasting groups. The DEGs in the cluster related to L-glutamine-related metabolites were enriched for T-cell receptor V(D)J recombination, the Hippo signaling pathway, the Wnt signaling pathway, the cGMP-PKG signaling pathway, and the mTOR signaling pathway and were significantly downregulated, indicating that the content of L-glutamine decreased at extreme HA, while fasting increased it to adapt to the environment. Moreover, abundant fatty acids were detected when rats were exposed to extreme HA without pretreatment. Our study revealed the fasting and hypoxic environment-related factors in SD rats and provided new insights into the genetic and molecular characteristics in the myocardium, which is critical to developing more potential rapid adaptation methods to extreme HA.

Temporal changes in biomarkers in individuals with and without acute mountain sickness following rapid ascent

BACKGROUND

Field studies have reported conflicting results regarding changes in biomarkers at high altitude. This study measured temporal changes in biomarkers and compared the differences between individuals with and without acute mountain sickness (AMS).

MATERIALS AND METHODS

This study included 34 nonacclimatized healthy participants. Ten-milliliters of blood were collected at four time points: 3 days before ascent (T0), on two successive nights at 3150 m (T1 and T2), and 2 days after descent (T3). Participants were transported by bus from 555 m to 3150 m within 3 hours. AMS was diagnosed using the self-reported Lake Louise Scoring (LLS) questionnaire.

RESULTS

Compared with T0, significant increases in E-selectin and decreases in vascular endothelial growth factor (VEGF) levels were observed at high altitude. Significantly increased C-reactive protein (CRP), monocyte chemoattractant protein-1 (MCP-1), and S100 calcium-binding protein B (S100B) levels were observed at T2, and significantly decreased vascular cell adhesion molecule-1 (VCAM-1) levels were observed at T3. Eighteen (53%) participants developed AMS. Changes in E-selectin, CRP, MCP-1, and S100B levels were independent of AMS. Relative to individuals without AMS, those with AMS had significantly higher atrial natriuretic peptide (ANP) and VCAM-1 levels and lower plasminogen activator inhibitor-1 (PAI-1) levels at T1 and higher brain natriuretic peptide and lower VEGF and PAI-1 levels at T3. LLSs were positively correlated with ANP and VCAM-1 levels and negatively correlated with PAI-1 levels measured at T1.

CONCLUSIONS

After acute ascent, individuals with and without AMS exhibited different trends in biomarkers associated with endothelial cell activation and natriuretic peptides.

Study of high-altitude cerebral edema using multimodal imaging

Objective

To analyze the brain imaging features of high-altitude cerebral edema (HACE) using computed tomography (CT) and multi-sequence magnetic resonance imaging (MRI) and to explore its injury characteristics.

Materials and methods

We selected 30 patients with HACE diagnosed between January 2012 to August 2022 as the experimental group and 60 patients with dizziness on traveling from the plain to the plateau or from lower altitude to higher altitude in a short period of time as the control group. We collected general clinical data from the experimental group and classified it according to clinical symptoms. In both groups, we then performed a head CT and multi-sequence MRI (T1WI, T2WI, FLAIR, and DWI). Among them, nine patients with HACE were also scanned using susceptibility-weighted imaging (SWI). Finally, we analyzed the images.

Results

According to clinical symptoms, we divided the 30 cases of HACE into 12 mild cases and 18 severe cases. There was no significant difference in sex, age, leukocyte, neutrophil, or glucose content between mild and severe HACE. The sensitivity and specificity of the MRI diagnosis were 100 and 100%, respectively, while the sensitivity and specificity of the CT diagnosis were 23.3 and 100%, respectively. The distribution range of deep and juxtacortical white matter edema was significantly larger in severe HACE than in mild HACE (p < 0.001). The corpus callosum edema distribution range in severe HACE was significantly larger than that in mild HACE (p = 0.001). The ADC value of the splenium of the corpus callosum was significantly lower in severe HACE than in mild HACE (p = 0.049). In mild and severe HACE, the signal intensity of the DWI sequence was significantly higher than that of conventional MRI sequences (T1WI, T2WI, FLAIR) (p = 0.008, p = 0.025, respectively). In severe HACE, seven cases showed bilateral corticospinal tract edema at the thalamic level, and SWI showed cerebral microbleeds (CMBs) in five cases, especially in the corpus callosum.

Conclusions

MRI has more advantages than CT in the evaluation of HACE, especially in the DWI sequence. The white matter injury of severe HACE is more severe and extensive, especially in the corpus callosum, and some CMBs and corticospinal tract edema may also appear.

Screening of osteoporosis and sarcopenia in individuals aged 50 years and older at different altitudes in Yunnan province: Protocol of a longitudinal cohort study

INTRODUCTION

Musculoskeletal system gradually degenerates with aging, and a hypoxia environment at a high altitude may accelerate this process. However, the comprehensive effects of high-altitude environments on bones and muscles remain unclear. This study aims to compare the differences in bones and muscles at different altitudes, and to explore the mechanism and influencing factors of the high-altitude environment on the skeletal muscle system.

METHODS

This is a prospective, multicenter, cohort study, which will recruit a total of 4000 participants over 50 years from 12 research centers with different altitudes (50m~3500m). The study will consist of a baseline assessment and a 5-year follow-up. Participants will undergo assessments of demographic information, anthropomorphic measures, self-reported questionnaires, handgrip muscle strength assessment (HGS), short physical performance battery (SPPB), blood sample analysis, and imaging assessments (QCT and/or DXA, US) within a time frame of 3 days after inclusion. A 5-year follow-up will be conducted to evaluate the changes in muscle size, density, and fat infiltration in different muscles; the muscle function impairment; the decrease in BMD; and the osteoporotic fracture incidence. Statistical analyses will be used to compare the research results between different altitudes. Multiple linear, logistic regression and classification tree analyses will be conducted to calculate the effects of various factors (e.g., altitude, age, and physical activity) on the skeletal muscle system in a high-altitude environment. Finally, a provisional cut-off point for the diagnosis of sarcopenia in adults at different altitudes will be calculated.

ETHICS AND DISSEMINATION

The study has been approved by the institutional research ethics committee of each study center (main center number: KHLL2021-KY056). Results will be disseminated through scientific conferences and peer-reviewed publications, as well as meetings with stakeholders.

CLINICAL TRIAL REGISTRATION NUMBER

http://www.chictr.org.cn/index.aspx, identifier ChiCTR2100052153.