Consensus statement on chronic and subacute high altitude diseases

Early effects of acetazolamide on hemoglobin mass and plasma volume in chronic mountain sickness at 5100 m

INTRODUCTION AND OBJECTIVES

Chronic Mountain Sickness (CMS) syndrome, combining excessive erythrocytosis and clinical symptoms in highlanders, remains a public health concern in high-altitude areas, especially in the Andes, with limited therapeutic approaches. The objectives of this study were to assess in CMS-highlanders permanently living in La Rinconada (5100-5300 m, Peru, the highest city in the world), the early efficacy of acetazolamide (ACZ) and atorvastatin to reduce hematocrit (Hct), as well as the underlying mechanisms focusing on intravascular volumes.

MATERIALS AND METHODS

Forty-one males (46±8 years of age) permanently living in La Rinconada for 15 [10-20] years and suffering from CMS were randomized between ACZ (250 mg once-daily; N = 13), atorvastatin (20 mg once-daily; N = 14) or placebo (N = 14) uptake in a double-blinded parallel study. Hematocrit (primary endpoint) as well as arterial blood gasses, total hemoglobin mass (Hbmass) and intravascular volumes were assessed at baseline and after a mean (±SD) treatment duration of 19±2 days.

RESULTS

ACZ increased PaO2 by +13.4% (95% CI: 4.3 to 22.5%) and decreased Hct by -5.2% (95% CI: -8.3 to -2.2%), whereas Hct remained unchanged with placebo or atorvastatin. ACZ tended to decrease Hbmass (-2.6%, 95% CI: -5.7 to 0.5%), decreased total red blood cell volume (RBCV, -5.3%, 95% CI: -10.3 to -0.3%) and increased plasma volume (PV, +17.6%, 95% CI: 4.9 to 30.3%). Atorvastatin had no effect on intravascular volumes, while Hbmass and RBCV increased in the placebo group (+6.1%, 95% CI: 4.2 to 7.9% and +7.0%, 95%CI: 2.7 to 11.4%, respectively).

CONCLUSIONS

Short-term ACZ uptake was effective to reduce Hct in CMS-highlanders living at extreme altitude >5,000 m and was associated with both an increase in PV and a reduction in RBCV.

Effect of Altitude on Polycythemia Vera: Is it Necessary to Change Limits?

Serin, Istemi, Ahmet Unal, Arzu Dobral, Fatma Elif Eroglu, Erdem Ayik, Jale Oz Unal, Mehmet Barış Cengiz, Okan Kati, Toros Taskin, Vural Bastug, and Abdulkadir Karismaz. The effect of altitude on polycythemia vera: Is it necessary to change limits? High Alt Med Biol. 00:00-00, 2025. Background: Polycythemia vera (PV) is a myeloproliferative disease characterized by high hemoglobin/hematocrit levels accompanied by JAK2 mutations. In this study, we aimed to establish a new hemoglobin cut-off value for the diagnosis and further evaluation of PV, taking into account the altitude of the regions where patients reside. In addition, we sought to examine the impact of altitude on patients diagnosed with PV and secondary polycythemia (SP) within our case series. Methods: Patients living in Istanbul and Agri who were evaluated for PV at the hematology outpatient clinic of Istanbul and Agri Training and Research Hospitals between January 20, 2023, and January 20, 2024, were included in the study. The average altitude of the center of Agri is 1,630 m, while the center of Istanbul is 30 m. Results: The mean altitude of residence for individuals diagnosed with PV was 326 ± 259 m, whereas it was significantly higher at 1,065 ± 675 m in the SP subgroup (p < 0.001). However, in subgroup analyses of patients with PV and SP, altitude was not a significant factor influencing hemoglobin levels. Conclusions: Our study results did not support the use of different hemoglobin cut-off values or correction factors for further evaluation of PV in patients living at different altitudes. Our results might not be applicable to altitudes higher than those we examined.

Chronic Mountain Sickness: A Comprehensive Review of Current Management and Proposals for Novel Therapies

Chronic mountain sickness (CMS) is an acquired condition affecting 5%-10% of high-altitude residents. Lifelong exposure to chronic hypoxia triggers excessive erythrocytosis, resulting in an expanded hematocrit. Patients present with symptoms such as dyspnea, fatigue, and palpitations. Complications such as pulmonary hypertension and heart failure are often fatal. Relocation to sea level remains the only definitive management of CMS but poses an unacceptable personal burden. Long-term oxygen therapy provides symptomatic relief, but dependency issues remain a concern. Phlebotomy reduces hematocrit and offers short-term symptom relief. However, side effects and cultural conflicts continue to pose challenges. Acetazolamide, enalapril, and medroxyprogesterone have lowered hematocrit and alleviated symptoms in human trials. Further research into systemic side effects, application in women, and long-term use is required. Methylxanthines, adrenergic blockers, almitrine, and dopamine antagonists showed promise in murine and/or short-term human trials, highlighting the need for further long-term human trials. Inhibition of hypoxia-inducible factor and Janus Kinase-signal transducer and activator of transcription pathways is currently used to suppress hematocrit in polycythemia vera, demonstrating potential application in CMS. Topiramate may stimulate ventilation via acid-base modulation, thus providing therapeutic value. Similarly, the effect of aspirin and caffeine on ventilation may provide a low-cost, accessible intervention.

Distinct methylomic signatures of high-altitude acclimatization and adaptation in the Tibetan Plateau

High altitude presents a challenging environment for human settlement. DNA methylation is an essential epigenetic mechanism that responds to environmental stimuli, but its roles in high-altitude short-term acclimatization (STA) and long-term adaptation (LTA) are poorly understood. Here, we conducted a methylome-wide association study involving 687 native highlanders and 299 acclimatized newcomers in the Tibetan Plateau and 462 native lowlanders to identify differentially methylated sites (DMSs) associated with STA or LTA. We identified 93 and 4070 DMSs for STA and LTA, respectively, which had no overlap, showed opposite asymmetric effect size patterns, and resided near genes enriched in distinct biological pathways/processes (e.g., cell cycle for STA and immune diseases and calcium signalling pathway for LTA). Epigenetic clock analysis revealed evidence of accelerated ageing in the acclimatized newcomers compared to the native lowlanders. Our research provides novel insights into epigenetic regulation in relation to high altitude and intervention strategies for altitude-related ageing or illnesses.

Closing the loop: autonomous intelligent control for hypoxia pre-acclimatization and high-altitude health management

Hypobaric hypoxia at high altitudes threatens the health of high-altitude residents. The development of effective methods to guarantee the safety of frequent human activities in high-altitude locations is therefore needed. Pre-acclimatization at sea level is an effective approach to mitigate subsequent altitude sickness for rapid ascent, which offers a viable substitute to on-site acclimatization, minimizes the associated risks that are linked to prolonged exposure in high-altitude environments and can be personalized to individual hypoxic responses. Another critical aspect to prevent long-term physical damage is personalized health management at high altitudes, which is enabled by the emerging technologies of wearable sensors, the Internet of Medical Things and artificial intelligence. In this review, we outline the progress in pre-acclimatization and high-altitude health management, as well as the understanding of physiological mechanisms under hypoxia, highlighting the important role that is played by wearable sensors and physiological closed-loop control systems in developing intelligent personalized solutions. We also discuss the challenges and prospects of deploying autonomous intelligent monitoring and control in high-altitude health management.

Association of hemoglobin with decreased prevalence of diabetic retinopathy among Tibetan male patients

INTRODUCTION

It has been reported that hemoglobin (Hb) levels are negatively associated with the prevalence of diabetic retinopathy (DR). This study aims to investigate the relationship between Hb levels and DR prevalence among highlanders, who exhibit elevated Hb levels as an adaptive response to hypoxia.

METHODS

This cross-sectional, hospital-based study utilized data from 645 Tibetan male patients with type 2 diabetes (T2D) between 2018 and 2020. Patients were divided into two groups based on Hb level (group 1: 12.0 ≤ Hb < 16.0 g/dL; group 2: Hb ≥ 16.0 g/dL). DR was diagnosed based on fundus photographs and fundus fluorescein angiography.

RESULTS

Among the study participants, 140 were diagnosed with DR. An inverse relationship was observed between Hb levels and the prevalence of DR. Each 1.0-g/dL increase in Hb concentration was associated with an 18% reduction in the prevalence of DR (95% confidence interval [CI]: 0.71-0.95). Multiple logistic regression analysis confirmed that patients with higher Hb levels had an adds ratio of 0.48 (95% CI, 0.29-0.79) for DR after adjusting for confounders, compared to those with lower Hb levels.

CONCLUSIONS

Our findings indicate that the inverse relationship between Hb levels and DR prevalence observed in lowland populations is also applicable to high-altitude individuals.

A case of plateau heart disease misdiagnosed as chronic pulmonary heart disease

This paper reports a case of plateau heart disease in Qinghai-Tibetan plateau who had recurrent symptoms of chest tightness and shortness of breath for 6 years but was misdiagnosed as chronic pulmonary heart disease. Plateau heart disease was diagnosed by thoracic computed tomography, pulmonary arteriography, pulmonary function tests and examination of medical history. Through the detailed analysis and differential diagnosis of this case, the aim is to distinguish between high-altitude heart disease and high-altitude chronic pulmonary heart disease, with the hope of achieving new breakthroughs in the diagnosis and treatment of this condition in the future.

Life destiny of erythrocyte in high altitude erythrocytosis: mechanisms underlying the progression from physiological (moderate) to pathological (excessive) high-altitude erythrocytosis

High-altitude polycythemia (HAPC) represents a pathological escalation of the physiological erythrocytosis induced by chronic hypoxia exposure. While moderate erythroid expansion enhances oxygen delivery, HAPC manifests as hematologic disorder characterized by hemoglobin thresholds (≥21 g/dL males; ≥19 g/dL females) and multi-organ complications including microcirculatory thrombosis, right ventricular hypertrophy, and uric acid dysmetabolism. This review critically evaluates the continuum between adaptive and maladaptive polycythemia through multiscale analysis of erythrocyte biology. We integrate genomic predisposition patterns, bone marrow erythroid kinetic studies, and peripheral erythrocyte pathophenotypes revealed by multi-omics profiling (iron-redox proteome, hypoxia-metabolome crosstalk). Current diagnostic limitations are highlighted, particularly the oversimplification of hemoglobin cutoffs that neglect transitional dynamics in erythrocyte turnover. By reconstructing the erythroid life cycle-from hypoxia-sensitive progenitor commitment to senescent cell clearance-we propose a phase transition model where cumulative epigenetic-metabolic derangements overcome homeostatic buffers, triggering pathological erythroid amplification. These insights reframe HAPC as a systems biology failure of erythroid adaptation, informing predictive biomarkers and targeted interventions to preserve hematological homeostasis in hypoxic environments.

Platelet Reduction in Rats Exposed to Chronic Hypoxia Is Associated with Interaction of Glycoprotein Ib Alpha von Willebrand Factor

Chronic high-altitude hypoxia is associated with reduced platelet count, but it is unclear whether the decrease in platelet count is due to impaired production or increased clearance. This study examines how hypoxia affects platelet production and apoptosis and elucidates the impact of glycoprotein Ibα-von Willebrand factor interaction on platelets in rats using a hypobaric hypoxia chamber. The results showed that the number of megakaryocytes increased under hypoxia; however, the levels of differentiation and polyploidy decreased, while those of apoptosis increased. Platelet production did not reduce according to the reticulated platelet percentage, while platelet apoptosis enhanced; these results suggest that increased platelet clearance was the main reason behind platelet reduction. Our previous microarray results indicated that glycoprotein Ibα (GPIbα) expression increased under hypoxia, which was a protein involved in platelet clearance; therefore, we examined the interaction of platelet GPIbα with the von Willebrand factor (vWF) both in vivo and in vitro to explore the effect of this process on platelets and whether it is related to platelet apoptosis. Under hypoxia, the stronger interaction between GPIbα and vWF promoted platelet apoptosis; inhibiting this interaction reduced platelet apoptosis and increased platelet counts. Platelet reduction is associated with apoptosis induced by the interaction between GPIbα and vWF.

The efficacy and safety of acetazolamide in chronic mountain sickness: A systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

The impact of acetazolamide (ACZ) in chronic mountain sickness (CMS) has not been fully assessed. The purpose of this systematic review is to evaluate the effectiveness and safety of acetazolamide in the treatment of chronic mountain sickness.

RESEARCH METHODS

This systematic review and meta-analysis were conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The primary outcome measure was CMS clinical score. Secondary outcomes included CMS total score,hematocrit (HCT), Pondus Hydrogenii‌ (pH), arterial oxygen pressure (PaO2), arterial carbon dioxide pressure (PaCO2), bicarbonate concentration (HCO3), and adverse events.

RESULTS

Five randomized controlled trials were included, comprising a total of 137 subjects, with 78 in the acetazolamide group and 59 in the control group.The CMS clinical score showed an MD of -0.31 (95% CI, -1.13 to -0.51, P = 0.46),the results indicated no statistical significance.But the CMS total score had an MD of -1.13 [95% CI, -2.03 to -0.23], P = 0.01, showing a significant difference.The HCT results showed an MD of -2.70 (95% CI, -4.58 to -0.82; P = 0.005), indicating a statistically significant reduction. The result of PaO2,PaCO2,pH and HCO3 are statistically significant. In terms of adverse events, increased diuresis and headache were not statistically significant. Paresthesia had a significant difference.

CONCLUSION

Based on the available evidence, we conclude that ACZ 250 mg is a safe, reliable, and low-cost treatment option for chronic mountain sickness. By reducing HCT, PaCO2, pH, and HCO3, and increasing PaO2, it improves respiratory and circulatory parameters in CMS patients and effectively treats CMS.

High-altitude pulmonary hypertension: a comprehensive review of mechanisms and management

High-altitude pulmonary hypertension (HAPH) is characterized by an increase in pulmonary artery pressure due to prolonged exposure to hypoxic environment at high altitudes. The development of HAPH involves various factors such as pressure changes, inflammation, oxidative stress, gene regulation, and signal transduction. The pathophysiological mechanisms of this condition operate at molecular, cellular, and genetic levels. Diagnosis of HAPH often relies on echocardiography, cardiac catheterization, and other methods to assess pulmonary artery pressure and its impact on cardiac function. Treatment options for HAPH encompass both nondrug and drug therapies. While advancements have been made in understanding the pathological mechanisms through research on animal models and clinical trials, there are still limitations to be addressed. Future research should focus on exploring molecular targets, personalized medicine, long-term management strategies, and interdisciplinary approaches. By leveraging advanced technologies like systems biology, omics technology, big data, and artificial intelligence, a comprehensive analysis of HAPH pathogenesis can lead to the identification of new treatment targets and strategies, ultimately enhancing patient quality of life and prognosis. Furthermore, research on health monitoring and preventive measures for populations living at high altitudes should be intensified to reduce the incidence and mortality of HAPH.

Association between single nucleotide polymorphisms in EPAS1 and PPARA genes and high altitude polycythemia in Chinese Tibetan population

Background

High altitude polycythemia (HAPC) is a disease with high morbidity and great harm in high altitude populations. It has been shown that Single Nucleotide Polymorphisms (SNPs) correlate with the genetic basis of adaptation to plateau hypoxia in Tibetan populations. The EPAS1 and PPARA genes are involved in hypoxia adaptation by encoding transcription factors in Tibetan populations at high altitude. The aim of this study was to investigate the association of EPAS1 and PPARA gene locus polymorphisms with genetic susceptibility to HAPC in the Chinese Tibetan population.

Methods

We included 78 HAPC patients and 84 healthy controls, and genotyped the EPAS1 gene SNP loci (rs6735530, rs6756667, rs7583392, and rs12467821) and PPARA rs6520015 by using TaqMan polymerase chain reaction. Logistic regression was used to analyze the association between these SNPs and HAPC; interactions between SNPs were also predicted by multifactorial dimensionality reduction (MDR) analysis.

Results

We found that the PPARA rs6520015 polymorphism was not associated with the risk of HAPC in the Chinese Tibetan population; EPAS1 rs6735530, rs6756667, rs7583392, and rs12467821 increased the risk of HAPC in some models. Haplotype TCAGC decreases the risk of HAPC; Haplotype TTGAT increases the risk of HAPC; and EPAS1 rs7583392 is in complete linkage disequilibrium with rs12467821. The best prediction model was the EPAS1 rs6756667 unit point model, but the P value was greater than 0.05 in all three models, which was not statistically significant.

Conclusion

The present findings suggest that among the Tibetan population in China, There is an association between EPAS1 rs6735530, rs6756667, rs7583392, and rs12467821 and the risk of HAPC, and that there is no significant correlation between PPARA rs6520015 and the risk of HAPC.

Hemoglobin is associated with hypertension-mediated cardiovascular damages in hypertensive patients with high-altitude polycythemia

High-altitude polycythemia (HAPC) is a pathological state resulting from maladaptation to prolonged high-altitude exposure, posing significant risks to the cardiovascular health of highlanders. However, its influence on hypertension-mediated organ damages (HMODs) in hypertensive individuals remains unclear. We recruited hypertensive patients residing at altitudes above 2500 m for over 3 years. A case-control matching was conducted in a 1:1 ratio between hypertensive patients with and without HAPC, based on gender and age. Echocardiography, carotid artery ultrasound, and brachial flow-mediated dilation (FMD) were measured as HMODs. A total of 88 hypertensive patients were included in the analysis, with 44 with HAPC and 44 without HAPC. Patients with HAPC showed significantly higher hemoglobin (HGB) levels (217.82 ± 17.34 vs. 160.16 ± 13.25, P<0.001), a larger left atrium (LA) diameter (35.36 ± 4.25 vs. 33.09 ± 3.55, P = 0.008), and a higher proportion of impaired FMD (95.45% vs. 79.55%, P = 0.049) compared to those without HAPC. No significant differences were found between the two groups in diastolic function parameters, left ventricular mass index (LVMI), relative wall thickness (RWT), or intima-media thickness (IMT). After adjusting for age, gender, and other confounding factors, HGB remained significantly associated with LA diameter (β = 0.034, P = 0.023) and impaired FMD (OR = 1.034, 95% CI 1.001-1.069). After matching for age and gender, hypertensive patients with HAPC exhibited a significantly larger LA diameter and a higher prevalence of impaired FMD compared to those without HAPC. Additionally, HGB was identified as an independent risk factor for both increased LA diameter and impaired FMD in hypertensive patients with HAPC.

The primary studies of epigallocatechin-3-gallate in improving brain injury induced by chronic high-altitude natural environment in rats by 7.0T high-field MR imaging

BACKGROUND

Epigallocatechin-3-gallate (EGCG) is one of the most abundant and important bioactive polyphenolic compounds in green tea. However, despite its potent antioxidant effects, its neuroprotective effects on chronic high altitude (HA)-induced nerve damage have not been reported. The purpose of this study is to use quantitative susceptibility mapping (QSM) with pathology to dynamically evaluate the status of brain damage and the effect of EGCG.

METHODS

A model of HA environments-induced brain injury was established of Sprague-Dawley (SD) rats in a natural plateau environment for 4 weeks, 8 weeks, 12 weeks and 20 weeks. Behavioral alterations were then observed and assessed with the open field test (OFT) and Morris water maze (MWM) test. The microglial activation, nissl staining and neural degeneration by Fluoro Jade B in the hippocampus of the rats were observed by immunohistochemistry. In the rats, serum erythropoietin (EPO), hippocampal inflammatory cytokines (interleukin-1β [IL-1β], interleukin-6 [IL-6] and tumor necrosis factor-α [TNF-α]), ferritin, oxidative stress (superoxide dismutase [SOD], glutathione peroxidase [GSH-Px], catalase [CAT] and malondialdehyde [MDA]) were detected using ELISA kits and biochemical methods. Iron accumulation was observed by QSM and colorimetry. Iron metabolisms (ceruloplasmin [Cp], transferrin [Tf], divalent metal transport1 [DMT1] and hepcidin [Hep]) were detected using qPCR. Neural ultrastructural changes were evaluated with electron microscope. Salidroside treatment was chosen as the positive control group in ELISA, biochemical detection and electron microscopy.

RESULTS

The susceptibility values in the left and right hippocampus, the hippocampal ferritin, serum and hippocampal iron content increased significantly after HA exposure. The expression of hippocampal Cp and Hep decreased and the expression of Tf increased. Nissl staining revealed that the neurons of hippocampal CA1 region of h-20w group were small and irregular, atrophied, and nuclear shrinkage. Tissue oxidative stress and inflammatory indicators (MDA, TNF-α, IL-1β, IL-6) increased while antioxidant enzymes (SOD, CAT, GSH-Px) decreased. EGCG attenuated HA environments-induced cognitive impairment, iron accumulation, microglial activation and neural degeneration. The effects of EGCG in reducing EPO and the metal chelating property with respect to iron were dose-dependent, with effects of EGCG (50 mg/kg) being similar to those of salidroside (50 mg/kg).

CONCLUSIONS

EGCG can act as a neuroprotective agent against chronic HA environments-mediated neural injuries. QSM provides a potential complementary imaging technique to detect the effect of treating HA diseases.

Redefining chronic mountain sickness: insights from high-altitude research and clinical experience

Chronic Mountain Sickness (CMS), characterized by increased red blood cells above average values traditionally attributed to chronic hypobaric hypoxia exposure, is being redefined in light of recent research and clinical experience. We propose a shift in perspective, viewing CMS not as a singular entity but as Poly-erythrocythemia (PEH), as the Hematocrit/Hemoglobin/Red Blood Cells (Ht/Hb/RBCs) increase constitutes a sign, not a disease reflecting a spectrum of oxygen transport alterations in multiple diseases in the chronic hypoxia environment in high-altitude populations. Drawing on over five decades of experience at the High Altitude Pulmonary and Pathology Institute (HAPPI-IPPA) in Bolivia, we advocate for altitude-specific blood parameter norms and emphasize the importance of correct etiological diagnosis for effective management. This updated understanding not only aids in managing chronically hypoxemic patients at various altitudes but also offers valuable insights into global health challenges, including the recovery from COVID-19.

Development and clinical validation of photochemical biosensors for monitoring hemoglobin, blood lipids and uric acid in plateau areas

High-altitude regions are prone to plateau erythrocytosis due to unique geo-climatic conditions such as low oxygen, high altitude, and low temperatures, with significantly higher incidences of hyperlipidemia and hyperuricemia compared to lowland areas. However, the extreme environmental conditions at high altitudes and the elevated hematocrit levels in blood samples from these populations present significant challenges to the applicability of existing point-of-care testing (POCT) devices. This study describes the development, early clinical validation, and potential clinical impact of three portable, paper-based photochemical biosensing platforms specifically designed for use at high altitudes to monitor hemoglobin, lipids, and uric acid in blood samples. To systematically evaluate the performance of these sensors, 154 fresh venous blood samples from three distinct altitudes were tested and compared with a reference measurement system, alongside an extensive evaluation for the first time of the suitability of various commercially available POCT devices, including these platforms, for use in high-altitude environments. The results demonstrated that the accuracy and concordance between the developed platforms and the reference system were consistently above 95%. Additionally, concordance remained above 95% when the same samples were tested at varying altitudes (4500 m to 3650 m and 4800 m to 3650 m). All of this indicates that the sensing platform provides high accuracy and reliability for testing in high-altitude environments. It holds promise for broader application in the screening and management of chronic diseases in high-altitude and other extreme environments, and for advancing the use of bedside testing technology in resource-limited settings.

Medical Problems of Chronic Hypoxia in Highlanders Living on the Tibetan Plateau

Ri-Li Ge. Medical problems of chronic hypoxia in highlanders living on the tibetan plateau. High Alt Med Biol. 00:00-00, 2024.-Health issues at high altitudes arise due to the lower atmospheric pressure and subsequent reduction in the partial pressure of oxygen in ambient air. While much research has been published on health problems of lowlanders who move to high altitudes, less is known about the medical challenges faced by long-term and permanent high-altitude residents, especially in the Qinghai-Tibetan plateau. In this review, we briefly summarized the chronic hypoxia-related health issues in highlanders, focusing on the specific population of the Qinghai-Tibetan plateau. It deals with important health problems for highlanders, including the main disease categories, from chronic mountain sicknesses and pulmonary hypertension (PH) to kidney, neurocognitive impairments, perinatal problems, and congenital heart defect. However, the most hallmark of disorders is excessive erythrocytosis associated with specific symptoms and signs, and high-altitude heart disease is characterized by excessive PH, right ventricular hypertrophy, and right heart failure. We also provide information on potential treatment strategies, including some traditional Tibetan medical practices and also a combination of Western medicine and traditional Chinese medicine to prevent and treat these conditions effectively. This mini-review is heavily based on a couple of decades of research carried out by Chinese high-altitude medical research groups at the Qinghai-Tibetan Plateau. We believe that this review will provide valuable perspective to researchers whose study interest and base lie in high altitude.

Real-time monitoring and prediction of remote operator fatigue in plateau deep mining based on dynamic Bayesian networks

Fatigue can cause human error, which is the main cause of accidents. In this study, the dynamic fatigue recognition of unmanned electric locomotive operators under high-altitude, cold and low oxygen conditions was studied by combining physiological signals and multi-index information. The characteristic data from the physiological signals (ECG, EMG and EM) of 15 driverless electric locomotive operators were tracked and tested continuously in the field for 2 h, and a dynamic fatigue state evaluation model based on a first-order hidden Markov (HMM) dynamic Bayesian network was established. The model combines contextual information (sleep quality, working environment and circadian rhythm) and physiological signals (ECG, EMG and EM) to estimate the fatigue state of plateau mine operators. The simulation results of the dynamic fatigue recognition model and subjective synchronous fatigue reports were compared with the field-measured signal data. The verification results show that the synchronous subjective fatigue and simulated fatigue estimation results are highly consistent (correlation coefficient r = 0.971**), which confirms that the model is reliable for long-term dynamic fatigue evaluation. The results show that the established fatigue evaluation model is effective and provides a new model and concept for dynamic fatigue state estimation for remote mine operators in plateau deep mining. Moreover, this study provides a reference for clinical medical research and human fatigue identification under high-altitude, cold and low-oxygen conditions.

Right ventricular strain impairment due to hypoxia in patients with COPD: a post hoc analysis of two randomised controlled trials

BACKGROUND

Hypoxic pulmonary vasoconstriction leads to an increase in pulmonary artery pressure (PAP) and potentially right heart failure in healthy individuals and patients with respiratory diseases. Previous studies in patients with chronic obstructive pulmonary disease (COPD) exposed to hypobaric hypoxia have shown an increase in PAP, while traditional echocardiographic parameters revealed only minimal changes at high altitude. Speckle-tracking-derived analysis is potentially more sensitive to assess right ventricular (RV) function and we used this method to investigate the impact on RV function of patients with COPD ascending to high altitude and compared the results with the traditional echocardiographic parameters.

METHODS

This post hoc analysis evaluates echocardiographic RV free wall strain (RVFWS) in patients with COPD GOLD grade 1-3 travelling from 760 m to 3100 m for a 2-day stay. An RVFWS over -20% was considered as an indicator of RV dysfunction.

RESULTS

A total of 54 patients (57% men, mean±SD age 58±9 years, forced expiratory volume in 1 s (FEV1 % predicted 77.3±22.5)) with echocardiographs of sufficient quality were included. The mean RVFWS worsened significantly from -26.0±4.9% at 760 m to -23.9±5.4% at 3100 m (p=0.02). The number of patients with relevant RV dysfunction based on RVFWS increased from 7.4% at 760 m to 25.9% at 3100 m (p=0.02), whereas the prevalence of RV dysfunction assessed by traditional indices remained unchanged.

CONCLUSION

Exposure to hypoxia led to RVFWS impairment in more than one quarter of patients with COPD. Strain analysis is a promising, non-invasive method for evaluating RV dysfunction, even in subclinical cases and might be prognostically relevant in patients with lung diseases.

TRIAL REGISTRATION NUMBERS

NCT02450968 and NCT03173508.

Elevated Perspectives: Unraveling Cardiovascular Dynamics in High-Altitude Realms

High-altitude regions pose distinctive challenges for cardiovascular health because of decreased oxygen levels, reduced barometric pressure, and colder temperatures. Approximately 82 million people live above 2400 meters, while over 100 million people visit these heights annually. Individuals ascending rapidly or those with pre-existing cardiovascular conditions are particularly vulnerable to altitude-related illnesses, including Acute Mountain Sickness (AMS) and Chronic Mountain Sickness (CMS). The cardiovascular system struggles to adapt to hypoxic stress, which can lead to arrhythmias, systemic hypertension, and right ventricular failure. Pathophysiologically, high-altitude exposure triggers immediate increases in cardiac output and heart rate, often due to enhanced sympathetic activity. Over time, acclimatisation involves complex changes, such as reduced stroke volume and increased blood volume. The pulmonary vasculature also undergoes significant alterations, including hypoxic pulmonary vasoconstriction and vascular remodelling, contributing to conditions, like pulmonary hypertension and high-altitude pulmonary edema. Genetic adaptations in populations living at high altitudes, such as gene variations linked to hypoxia response, further influence these physiological processes. Regarding cardiovascular disease risk, stable coronary artery disease patients generally do not face significant adverse outcomes at altitudes up to 3500 meters. However, those with unstable angina or recent cardiac interventions should avoid high-altitude exposure to prevent exacerbation. Remarkably, high-altitude living correlates with reduced cardiovascular mortality rates, possibly due to improved air quality and hypoxia-induced adaptations. Additionally, there is a higher incidence of congenital heart disease among children born at high altitudes, highlighting the profound impact of hypoxia on heart development. Understanding these dynamics is crucial for managing risks and improving health outcomes in high-altitude environments.

The Effects of Nocturnal Hypoxemia on Cognitive Performance in Andean Highlanders

Background: Many Andean highlanders exposed to chronic hypoxemia are susceptible to excessive erythrocytosis (EE) and chronic mountain sickness (CMS). Nocturnal hypoxemia is more marked than diurnal hypoxemia and includes sustained and intermittent components. The potential for cognitive impairments related to nocturnal hypoxemia in this population has not been extensively studied, but improved understanding may provide opportunities for the prevention of long-term effects of EE and CMS. Methods: To examine this relationship, 48 participants residing permanently at 4,340 m completed an overnight sleep study and a battery of cognitive function tests that examined a broad range of cognitive domains. Results: Greater nocturnal hypoxemia was associated with longer reaction times on Balloon Analogue Risk Task (BART) (p < 0.01) and Emotion Recognition Test (ERT) (p < 0.01). Longer completion times of Trail Making Task were also associated with increased nocturnal hypoxemia (p = 0.03). Increased hematocrit was similarly associated with longer reaction times on the ERT (p = 0.01) and the BART (p = 0.01). Conclusion: Overall, our results showed that increased nocturnal hypoxemia and higher hematocrit were associated with impairments in cognitive performance in individuals residing permanently at high altitude.

Effect of therapeutic erythrocytapheresis on outcomes and renal benefit in patients with high-altitude polycythemia: a real-world study

Kidney injury from high-altitude polycythemia (HAPC) is common, yet few studies have explored effective treatments. This research assessed the renal benefits of therapeutic erythrocytapheresis (TE) in HAPC patients, analyzing the efficacy of single versus multiple treatments. From 2017 to 2023, 631 patients undergoing TE were included. Findings showed notable improvements in hemoglobin levels (median: 228.00 vs. 169.00 g/L, p < 0.001), estimated glomerular filtration rate (eGFR) (median: 100.24 vs. 105.92 ml/min/1.73 m2, p < 0.001), and uric acid levels (median 495.00 vs. 405.00 µmol/L, p < 0.001). The rate of patients with negative urine protein tests rose from 54.58 to 92.83%. Analysis indicated that a lower pre-treatment eGFR was associated with significant renal improvement post-treatment (OR 0.959, 95% CI 0.945-0.972, p < 0.001), even when adjusting for hemoglobin and other factors (OR 0.962, 95% CI 0.947-0.977, p < 0.001). After propensity score matching, 168 patients were categorized based on the number of treatments. Compared to single treatment, multiple treatments resulted in significantly lower hemoglobin levels post-treatment (median: 177.00 vs. 165.00 g/L, p < 0.001). TE proves to be a beneficial treatment for HAPC, improving hemoglobin and renal function. Multiple treatments may be preferable for maintaining stable hemoglobin levels.

Born high, born fast: Does highland birth confer a pulmonary advantage for sea level endurance?

Less than 7% of the world's population live at an altitude above 1500 m. Yet, as many as 67% of medalists in the 2020 men's and women's Olympic marathon, and 100% of medalists in the 2020 men's and women's Olympic 5000 m track race may have been born or raised above this otherwise rare threshold. As a possible explanation, research spanning nearly a quarter of a century demonstrates that indigenous highlanders exhibit pulmonary adaptations distinct from their lowland counterparts. These adaptations may then promote endurance performance. Indeed, healthy indigenous highlanders often exhibit a larger aerobic exercise capacity compared to sea-level residents who travel to high altitude. However, questions remain on whether high-altitude birth is advantageous for sea-level competitions. In this review, we ask whether being born at a high altitude generates an ergogenic advantage for endurance performance in the Summer Olympics-a venue that is generally held at sea level. In so doing, we distinguish between three groups of high-altitude residents: (i) the indigenous highlander, (ii) the highland newcomer, and (iii) the highland sojourner. Concentrating specifically on altitude-induced alterations to pulmonary physiology beginning in the perinatal period, we propose that if altitude-related maladaptations are avoided, genomic and developmental alterations accompanying highland birth may present benefits for endurance competitions at sea level.

Expedition 5300: limits of human adaptations in the highest city in the world

Exposure to chronic hypobaric hypoxia imposes a significant physiological burden to more than 80 million humans living above 2500 m throughout the world. Among them, 50 000 live in the world's highest city, La Rinconada, located at 5000-5300 m in southern Peru. Expedition 5300 is the first scientific and medical programme led in La Rinconada to investigate the physiological adaptations and altitude-related health issues in this unique population. Dwellers from La Rinconada have very high haemoglobin concentration (20.3 ± 2.4 g/dL; n = 57) and those with chronic mountain sickness (CMS) exhibit even higher concentrations (23.1 ± 1.7 g/dL; n = 150). These values are associated with large total haemoglobin mass and blood volume, without an associated iron deficit. These changes in intravascular volumes lead to a substantial increase in blood viscosity, which is even larger in CMS patients. Despite these large haematological changes, 24 h blood pressure monitoring is essentially normal in La Rinconada, but some results suggest impaired vascular reactivity. Echocardiography revealed large right heart dilatation and high pulmonary arterial pressure as well as left ventricle concentric remodelling and grade I diastolic dysfunction. These changes in heart dimension and function tend to be more severe in highlanders with CMS. Polygraphy evaluations revealed a large reduction in nocturnal pulse oxygen saturation (median SpO2 = 79%), which is even more severe in CMS patients who also tended to show a higher oxygen desaturation index. The population of La Rinconada offers a unique opportunity to investigate the human responses to chronic severe hypoxia, at an altitude that is probably close to the maximum altitude human beings can permanently tolerate without presenting major health issues.

Symposium review: high altitude travel with pulmonary vascular disease

Pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension are the main precapillary forms of pulmonary hypertension (PH) summarized as pulmonary vascular diseases (PVD). PVDs are characterized by exertional dyspnoea and oxygen desaturation, and reduced quality of life and survival. Medical therapies improve life expectancy and physical performance of PVD patients, of whom many wish to participate in professional work and recreational activities including traveling to high altitude. The exposure to the hypobaric hypoxic environment of mountain regions incurs the risk of high altitude adverse events (AEHA) due to severe hypoxaemia exacerbating symptoms and further increase in pulmonary artery pressure, which may lead to right heart decompensation. Recent prospective and randomized trials show that altitude-induced hypoxaemia, pulmonary haemodynamic changes and impairment of exercise performance in PVD patients are in the range found in healthy people. The vast majority of optimally treated stable PVD patients who do not require long-term oxygen therapy at low altitude can tolerate short-term exposure to moderate altitudes up to 2500 m. PVD patients that reveal persistent severe resting hypoxaemia (S p O 2 ${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$  <80% for >30 min) at 2500 m respond well to supplemental oxygen therapy. Although there are no accurate predictors for AEHA, PVD patients with unfavourable risk profiles at low altitude, such as higher WHO functional class, lower exercise capacity with more pronounced exercise-induced desaturation and more severely impaired haemodynamics, are at increased risk of AEHA. Therefore, doctors with experience in PVD and high-altitude medicine should counsel PVD patients before any high-altitude sojourn. This review aims to summarize recent literature and clinical recommendations about PVD patients travelling to high altitude.

DDIT4 promotes erythroid differentiation and coordinates with SIPA1 to regulate erythroid proliferation in bone marrow of high altitude erythrocytosis

Erythrocytosis moderately enhances the oxygen-carrying capacity of the blood and is considered a characteristic response of individuals adapting from low-altitude regions to high-altitude regions. Nevertheless, erythrocytosis can also turn excessive and result in maladaptive syndromes, such as high altitude polycythemia (HAPC). The increased differentiation or proliferation of erythroid cells in the bone marrow may be a crucial factor leading to accumulation of peripheral erythroid cells. However, the mechanism of erythroid regulation within the bone marrow of high-altitude erythrocytosis remains insufficiently systematically observed. We utilized single-cell transcription sequencing to characterize bone marrow cells following chronic hypoxic exposure and found that bone marrow erythrocytosis is associated with the accumulation of Baso-E, Poly-E, and Ortho-E cells at the terminal stage of erythroid lineage differentiation. Through analysis of differential gene expression and localization in differentiated cells within the erythroid lineage, we confirmed that DDIT4 expression was localized in advanced differentiated erythroblast including Baso-E, Poly-E and Ortho-E, its expression was significantly enhanced by hypoxia exposure. We demonstrated that overexpression of DDIT4 could promote K562 cell differentiation, and through the IP pull-down interaction protein profile, we found that DDIT4 might participate in regulating the cell cycle by interacting with SIPA1 to promote the proliferation of erythroid cells and may be involved in HAPC.

Astaxanthin Supplementation Effects in Right Ventricle of Rats Exposed to Chronic Intermittent Hypobaric Hypoxia

In Chile, individuals are commonly exposed to high altitude due to the work shift system, involving days of exposure to high altitude followed by days at sea level over the long term, which can result in chronic intermittent hypobaric hypoxia (CIHH). CIHH can cause high-altitude pulmonary hypertension (HAPH), the principal manifestation of which is right ventricular hypertrophy (RVH), in some cases leading to heart failure and eventually death. Studies have shown the contribution of oxidative stress and inflammation to RVH development. Recently, it was determined that the pigment astaxanthin has high antioxidant capacity and strong anti-inflammatory and cardioprotective effects. Therefore, the aim of this study was to determine the effects of astaxanthin on RVH development in rats subjected to CIHH.

METHODS

Thirty two male Wistar rats were randomly assigned to the following groups (n = 8 per group): the normoxia with vehicle (NX), normoxia with astaxanthin (NX + AS), chronic intermittent hypobaric hypoxia with vehicle (CIHH), and chronic intermittent hypobaric hypoxia with astaxanthin (CIHH + AS) groups. CIHH was simulated by 2 days in a hypobaric chamber followed by 2 days at sea level for 29 days.

RESULTS

Exposure to CIHH induced RVH and increased lipid peroxidation (MDA), Nox2 expression, and SOD activity, however, it decreased pro-IL-1β expression. Astaxanthin restored oxidative stress markers (Nox2 and MDA), increased GPx activity, and decreased RVH compared to CIHH.

CONCLUSION

Astaxanthin alleviates RVH and reduces Nox2 and MDA levels while increasing GPx activity in rats subjected to CIHH. These findings provide new insights of astaxanthin as a new nutraceutical against high-altitude effects.

Effects of hemodynamic load on cardiac remodeling in fish and mammals: the value of comparative models

The ability of the vertebrate heart to remodel enables the cardiac phenotype to be responsive to changes in physiological conditions and aerobic demand. Examples include exercise-induced cardiac hypertrophy, and the significant remodeling of the trout heart during thermal acclimation. Such changes are thought to occur in response to a change in hemodynamic load (i.e. the forces that the heart must work against to circulate blood). Variations in hemodynamic load are caused by either a volume overload (high volume of blood returning to the heart, impairing contraction) or a pressure overload (elevated afterload pressure that the heart must contract against). The changes observed in the heart during remodeling are regulated by multiple cellular signaling pathways. The cardiac response to these regulatory mechanisms occurs across levels of biological organization, affecting cardiac morphology, tissue composition and contractile function. Importantly, prolonged exposure to pressure overload can cause a physiological response - that improves function - to transition to a pathological response that causes loss of function. This Review explores the role of changes in hemodynamic load in regulating the remodeling response, and considers the cellular signals responsible for regulating remodeling, incorporating knowledge gained from studying biomedical models and comparative animal models. We specifically focus on the renin-angiotensin system, and the role of nitric oxide, oxygen free radicals and transforming growth factor beta. Through this approach, we highlight the strong conservation of the regulatory pathways of cardiac remodeling, and the specific conditions within endotherms that may be conducive to the development of pathological phenotypes.

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.

Micro- and macrovascular function in the highest city in the world: a cross sectional study

Background

Since vascular responses to hypoxia in both healthy high-altitude natives and chronic mountain sickness (a maladaptive high-altitude pathology characterised by excessive erythrocytosis and the presence of symptoms-CMS) remain unclear, the role of inflammation and oxidative/nitrosative stress on the endothelium-dependent and -independent responses in both the micro- and macrocirculation, in healthy Andeans at different altitudes and in CMS patients, was examined.

Methods

94 men were included: 18 lowlanders (LL), 38 healthy highlanders permanently living at 3800 m (n = 21-HL-3800) or in La Rinconada, the highest city in the world (5100-5300 m) (n = 17-HL-5100/No CMS). Moreover, 14 participants with mild (Mild CMS) and 24 with moderate to severe CMS (Mod/Sev CMS) were recruited. All undertook two reactivity tests: i) local thermal hyperaemia (microcirculation) and ii) flow-mediated dilation (macrocirculation). Endothelium-independent function (glyceryl trinitrate) was also assessed only in La Rinconada.

Findings

Conductance and skin blood flow velocity during the microcirculation test, as well as macrocirculation progressively decreased with altitude (LL > HL-3800 > HL-5100/No CMS). CMS also induced a decrease in macrocirculation (HL-5100/No CMS > Mild CMS = Mod/Sev CMS), while glyceryl trinitrate restored vascular function. Both oxidative stress and nitric oxide metabolites increased with altitude only. Principal component analysis revealed that increasing inflammation with altitude was associated with a progressive decline in both micro- and macrovascular function in healthy highlanders.

Interpretation

Both micro and macrovascular function are affected by chronic exposure to hypoxia, the latter being further compounded by CMS.

Funding

The "Fonds de dotation AGIR pour les maladies chroniques", the "Air Liquide Foundation", and the "French National Research Agency".

Mountain sickness in altitude inhabitants of Latin America: A systematic review and meta-analysis

OBJECTIVE

Chronic and acute mountain sickness is known worldwide, but most of the available information comes from the eastern continent (Himalayas) without taking into account the west which has the most recent group located at altitude, the Andes. The aim of this study was to synthesize the evidence on the prevalence of acute and chronic mountain sickness in Latin American countries (LATAM).

METHODS

A systematic search of the variables of interest was performed until July 8, 2023 in the Web of Science, Scopus, PubMed and Embase databases. We included studies that assessed the prevalence of mountain sickness in high-altitude inhabitants (>1500 m.a.s.l) who lived in a place more than 12 months. These were analyzed by means of a meta-analysis of proportions. To assess sources of heterogeneity, subgroup analyses and sensitivity analyses were performed by including only studies with low risk of bias and excluding extreme values (0 or 10,000 ratio). PROSPERO (CRD42021286504).

RESULTS

Thirty-nine cross-sectional studies (10,549 participants) met the inclusion criteria. We identified 5 334 and 2 945 events out of 10,000 with acute and chronic mountain sickness in LATAM countries. The most common physiological alteration was polycythemia (2,558 events), while cerebral edema was the less common (46 events). Clinical conditions were more prevalent at high altitudes for both types of MS.

CONCLUSION

Acute mountain sickness (AMS) occurs approximately in 5 out of 10 people at high altitude, while chronic mountain sickness (CMS) occurs in 3 out of 10. The most frequent physiological alteration was polycythemia and the least frequent was cerebral edema.

Pulmonary vascular diseases at high altitude - is it safe to live in the mountains?

PURPOSE OF REVIEW

This review addresses the concern of the health effects associated with high-altitude living and chronic hypoxia with a focus on pulmonary hypertension. With an increasing global population residing at high altitudes, understanding these effects is crucial for public health interventions and clinical management.

RECENT FINDINGS

Recent literature on the long-term effects of high-altitude residence and chronic hypoxia is comprehensively summarized. Key themes include the mechanisms of hypoxic pulmonary vasoconstriction, the development of pulmonary hypertension, and challenges in distinguishing altitude-related pulmonary hypertension and classical pulmonary vascular diseases, as found at a low altitude.

SUMMARY

The findings emphasize the need for research in high-altitude communities to unravel the risks of pulmonary hypertension and pulmonary vascular diseases. Clinically, early and tailored management for symptomatic individuals residing at high altitudes are crucial, as well as access to advanced therapies as proposed by guidelines for pulmonary vascular disease. Moreover, identifying gaps in knowledge underscores the necessity for continued research to improve understanding and clinical outcomes in high-altitude pulmonary vascular diseases.

Mechanism of the apoptosis of bone marrow erythroblasts in rats under hypobaric hypoxia

This study aimed to investigate the mechanism of the apoptosis of erythroblasts in rat bone marrow after the exposure to hypobaric hypoxia. Male SD rats were randomly divided into three groups. The hypoxic group was kept in a hypobaric hypoxia chamber at a simulated altitude of 5000 m for 7 and 28 days, respectively. The control group was kept at an altitude of 2260 m. We found that myeloid: erythroid (M:E) ratio was significantly lower after hypoxia exposure and the proportions of polychromatic erythroblasts and orthochromatic erythroblasts significantly increased compared to control group, along with significant increase in the proportion of CD71+ cells and apoptosis rate. The expression levels of caspase-3, Bax, and Cyt-C in CD71+ cells were higher after hypoxia exposure than those in control group, while there was no significant difference in the expression levels of TNFR and Fas. In conclusion, after exposure to hypobaric hypoxia the proliferation of peripheral blood and bone marrow erythroblasts in rats increased, and apoptosis also increased, indicating that bone marrow erythroblasts in rats is regulated by both proliferation and apoptosis, and the mitochondrial pathway is one of the important pathways for apoptosis.

Performance in the Six-Minute Walking Test Does Not Discriminate Excessive Erythrocytosis Patients in a Severe Hypoxic Environment

BACKGROUND

Chronic exposure to severe hypoxia causes an increase in hematocrit (Hct) and hemoglobin concentration ([Hb]), which can lead to excessive erythrocytosis (EE) and impact physical performance. This work aims to determine the differences in the six-minute walking test (6MWT) between EE and healthy subjects residing at more than 5000 m.

METHODS

A prospective, cross-sectional study was performed on 71 men (36 healthy and 25 suffering from EE) living in La Rinconada, Peru (5100 m). Basal levels of [Hb] and Hct were obtained. All the subjects performed the 6MWT, and distance reached, vital signs, dyspnea, and fatigue (Borg scale) at the end of the test were recorded.

RESULTS

The average [Hb] and Hct levels in the control group were 18.7 ± 1.2 g/dL and 60.4 ± 7.1%, respectively, contrasting with EE subjects, who showed 23.4 ± 1.6 g/dL and 73.6 ± 5.9% (p < 0.001). However, no statistically significant differences were observed in BMI or other anthropometric parameters. At the end of the 6MWT, the distance traveled and vital constants were similar between both groups, except for arterial oxygen saturation, which was consistently lower in subjects with EE throughout the test.

CONCLUSION

EE does not significantly affect 6MWT performance at high altitudes, nor the hemodynamic control during moderate aerobic exercise of subjects who live permanently in a severely hypoxic environment.

Cerebral homeostasis and orthostatic responses in residents of the highest city in the world

Permanent residence at high-altitude and chronic mountain sickness (CMS) may alter the cerebrovascular homeostasis and orthostatic responses. Healthy male participants living at sea-level (LL; n = 15), 3800 m (HL3800m; n = 13) and 5100 m (HL5100m; n = 17), respectively, and CMS highlanders living at 5100 m (n = 31) were recruited. Middle cerebral artery mean blood flow velocity (MCAv), cerebral oxygen delivery (CDO2), mean blood pressure (MAP), heart rate variability and spontaneuous cardiac baroreflex sensitivity (cBRS) were assessed while sitting, initial 30 s and after 3 min of standing. Cerebral autoregulation index (ARI) was estimated (ΔMCAv%baseline)/ΔMAP%baseline) in response to the orthostatic challenge. Altitude and CMS were associated with hypoxemia and elevated hemoglobin concentration. While sitting, MCAv and LFpower negatively correlated with altitude but were not affected by CMS. CDO2 remained preserved. BRS was comparable across all altitudes, but lower with CMS. Within initial 30 s of standing, altitude and CMS correlated with a lesser ΔMAP while ARI remained unaffected. After 3 min standing, MCAv, CDO2 and cBRS remained preserved across altitudes. The LF/HF ratio increased in HL5100m compared to LL and HL3800m from sitting to standing. In contrary, CMS showed blunted autonomic nervous activation in responses to standing. Despite altitude- and CMS-associated hypoxemia, erythrocytosis and impaired blood pressure regulation (CMS only), cerebral homeostasis remained overall preserved.

Prevalence and risk factors of deep venous thrombosis of hospitalizations in plateau: a cross-section analysis

BACKGROUND

Deep venous thrombosis (DVT) is a serious public health issue that threatens human health and economic development. Presently, differences in the prevalence of DVT among individuals from different nationalities, residents of high-altitude areas, and those consuming any special diet are unknown. Therefore, we aimed to elucidate the prevalence of and the associated risk factors for DVT in hospitalized patients in the plateau areas.

METHODS

The subjects were hospitalized patients in three grade III-a hospitals in the Qinghai Province, China, during January-October 2020. The demographic, clinical, and laboratory data were collected at admission, and ultrasonography of the bilateral lower extremities was performed. The hospital stay-duration was recorded at the time of discharge.

RESULTS

A total of 3432 patients were enrolled, of which 159 (4.60%) were diagnosed with DVT. The age of > 50 years (OR = 2.434, 95% CI: 1.521-3.894252, P < 0.001), residence altitude of ≥ 3000 m (OR = 2.346, 95% CI: 1.239-4.440, P = 0.009), D-dimer level of ≥ 0.5 mg/L (OR = 2.211, 95% CI: 1.547-3.161, P < 0.001), presence of comorbidities (OR = 1.904, 95% CI: 1.386-2.705, P < 0.001), a history of varicose veins (OR = 1.990, 95% CI: 0.959-4.128, P = 0.045), and current medications (OR = 2.484, 95% CI: 1.778-3.471, P < 0.001) were identified as risk factors for DVT in these plateau areas.

CONCLUSION

The prevalence of DVT in the hospitalized patients of the studied plateau areas was 4.60%. We recommend considering individualized risk stratification (age > 50 years, residence altitude ≥ 3000 m, a history of varicose veins, D-dimer level ≥ 0.5 mg/L, current medications, and comorbidities) for patients at the time of admission.

Making a virtue out of an evil: Are red blood cells from chronic mountain sickness patients eligible for transfusions?

We investigated highlanders, permanently living at an altitude of 5100 m and compared Chronic Mountain Sickness (CMS) patients with control volunteers. While we found differences in systemic parameters such as blood oxygen content, hematocrit, hemoglobin concentration, and blood viscosity, the mechanical and rheological properties of single red blood cells did not differ between the two investigated groups.

Characteristics and risk profiles of patients with pulmonary arterial or chronic thromboembolic pulmonary hypertension living permanently at >2500 m of high altitude in Ecuador

Over 80 Mio people worldwide live >2500 m, including at least as many patients with pulmonary vascular disease (PVD), defined as pulmonary arterial or chronic thromboembolic pulmonary hypertension (PAH/CTEPH), as elsewhere (estimated 0.1‰). Whether PVD patients living at high altitude have altered disease characteristics due to hypobaric hypoxia is unknown. In a cross-sectional study conducted at the Hospital Carlos Andrade Marin in Quito, Ecuador, located at 2840 m, we included 36 outpatients with PAH or CTEPH visiting the clinic from January 2022 to July 2023. We collected data on diagnostic right heart catheterization, treatment, and risk factors, including NYHA functional class (FC), 6-min walk distance (6MWD), and NT-brain natriuretic peptide (BNP) at baseline and at last follow-up. Thirty-six PVD patients (83% women, 32 PAH, 4 CTEPH, mean ± SD age 44 ± 13 years, living altitude 2831 ± 58 m) were included and had the following baseline values: PaO2 8.2 ± 1.6 kPa, PaCO2 3.9 ± 0.5 kPa, SaO2 91 ± 3%, mean pulmonary artery pressure 53 ± 16 mmHg, pulmonary vascular resistance 16 ± 4 WU, 50% FC II, 50% FC III, 6MWD 472 ± 118 m, BNP 490 ± 823 ng/L. Patients were treated for 1628 ± 1186 days with sildenafil (100%), bosentan (33%), calcium channel blockers (33%), diuretics (69%), and oxygen (nocturnal 53%, daytime 11%). Values at last visit were: FC (II 75%, III 25%), 6MWD of 496 ± 108 m, BNP of 576 ± 5774 ng/L. Compared to European PVD registries, ambulatory PVD patients living >2500 m revealed similar blood gases and relatively low and stable risk factor profiles despite severe hemodynamic compromise, suggesting that favorable outcomes are achievable for altitude residents with PVD. Future studies should focus on long-term outcomes in PVD patients dwelling >2500 m.

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.

Are coagulation profiles in Andean highlanders with excessive erythrocytosis favouring hypercoagulability?

Chronic mountain sickness is a maladaptive syndrome that affects individuals living permanently at high altitude and is characterized primarily by excessive erythrocytosis (EE). Recent results concerning the impact of EE in Andean highlanders on clotting and the possible promotion of hypercoagulability, which can lead to thrombosis, were contradictory. We assessed the coagulation profiles of Andeans highlanders with and without excessive erythrocytosis (EE+ and EE-). Blood samples were collected from 30 EE+ and 15 EE- in La Rinconada (Peru, 5100-5300 m a.s.l.), with special attention given to the sampling pre-analytical variables. Rotational thromboelastometry tests were performed at both native and normalized (40%) haematocrit using autologous platelet-poor plasma. Thrombin generation, dosages of clotting factors and inhibitors were measured in plasma samples. Data were compared between groups and with measurements performed at native haematocrit in 10 lowlanders (LL) at sea level. At native haematocrit, in all rotational thromboelastometry assays, EE+ exhibited hypocoagulable profiles (prolonged clotting time and weaker clot strength) compared with EE- and LL (all P < 0.01). At normalized haematocrit, clotting times were normalized in most individuals. Conversely, maximal clot firmness was normalized only in FIBTEM and not in EXTEM/INTEM assays, suggesting abnormal platelet activity. Thrombin generation, levels of plasma clotting factors and inhibitors, and standard coagulation assays were mostly normal in all groups. No highlanders reported a history of venous thromboembolism based on the dedicated survey. Collectively, these results indicate that EE+ do not present a hypercoagulable profile potentially favouring thrombosis.

A Case of High-Altitude Renal Syndrome

Wang, Si-Yang, Jun Liang, and Jing-Hong Zhao. A Case of High-Altitude Renal Syndrome. High Alt Med Biol. 00:000-000, 2024.-Epidemiological studies have confirmed that high-altitude exposure increases the risk of proteinuria. The concept of high-altitude renal syndrome (HARS) was proposed in 2011. HARS is a group of clinical syndromes consisting of high-altitude polycythemia, hyperuricemia, systemic hypertension, and microalbuminuria. At present, no standardized and unified treatment methods of HARS have been proposed. We report a case of HARS without other organ involvement in a young man exposed to high altitude. Decreasing the red blood cell count and hemodynamic changes as soon as possible may be of great importance for reducing proteinuria. In addition, angiotensin receptor blockers are effective in the treatment of HARS.

Study on Allele Specific Expression of Long-Term Residents in High Altitude Areas

In diploid organisms, half of the chromosomes in each cell come from the father and half from the mother. Through previous studies, it was found that the paternal chromosome and the maternal chromosome can be regulated and expressed independently, leading to the emergence of allele specific expression (ASE). In this study, we analyzed the differential expression of alleles in the high-altitude population and the normal population based on the RNA sequencing data. Through gene cluster analysis and protein interaction network analysis, we found some changes occurred at the gene level, and some negative effects. During the study, we realized that the calmodulin homology domain may have a certain correlation with long-term survival at high altitude. The plateau environment is characterized by hypoxia, low air pressure, strong ultraviolet radiation, and low temperature. Accordingly, the genetic changes in the process of adaptation are mainly reflected in these characteristics. High altitude generation living is also highly related to cancer, immune disease, cardiovascular disease, neurological disease, endocrine disease, and other diseases. Therefore, the medical system in high altitude areas should pay more attention to these diseases.

Hypermethylation of BMPR2 and TGF-β Promoter Regions in Tibetan Patients with High-Altitude Polycythemia at Extreme Altitude

Although the expression of many genes is associated with adaptation to high-altitude hypoxic environments, the role of epigenetics in the response to this harsh environmental stress is currently unclear. We explored whether abnormal DNA promoter methylation levels of six genes, namely, ABCA1, SOD2, AKT1, VEGFR2, TGF-β, and BMPR2, affect the occurrence and development of high-altitude polycythemia (HAPC) in Tibetans. The methylation levels of HAPC and the control group of 130 Tibetans from very high altitudes (> 4500 m) were examined using quantitative methylation-specific real-time PCR (QMSP). Depending on the type of data, the Pearson chi-square test, Wilcoxon rank-sum test, and Fisher exact test were used to assess the differences between the two groups. The correlation between the methylation levels of each gene and the hemoglobin content was explored using a linear mixed model. Our experiment revealed that the methylation levels of the TGF-β and BMPR2 genes differed significantly in the two groups (p < 0.05) and linear mixed model analysis showed that the correlation between the hemoglobin and methylation of ABCA1, TGF-β, and BMPR2 was statistically significant (p < 0.05). Our study suggests that levels of TGF-β and BMPR2 methylation are associated with the occurrence of HAPC in extreme-altitude Tibetan populations among 6 selected genes. Epigenetics may be involved in the pathogenesis of HAPC, and future experiments could combine gene and protein levels to verify the diagnostic value of TGF-β and BMPR2 methylation levels in HAPC.

Community Care Needs of Highly Complex Chronic Patients: An Epidemiological Study in a Healthcare Area

One of the priorities in family and community care is the epidemiological surveillance of the care needs and dysfunctionality present in populations of highly complex chronic patients (HCCPs) using standardised nursing languages. The aim of this study is to establish the prevalence of care needs and dysfunctionality among HCCPs in a specific health area by municipalities and geographical areas (metropolitan, north, and south) while verifying correlations with sociodemographic, financial, and health characteristics. This is an epidemiological, observational, descriptive, cross-sectional study carried out with a sample of 51,374 HCCPs, whose data were grouped into 31 municipalities. Data were collected on the following variables: sociodemographic, financial, health, functional status (health patterns), and care needs (nursing diagnoses). The mean age of the HCCPs was 73.41 (1.45) years, of which 56.18 (2.86)% were women. The municipalities in the northern area have a significantly higher proportion of older patients, HCCPs, lower incomes, and higher unemployment rates. The southern area had higher proportions of non-Spanish nationals and professionals in the hotel and catering industry, and the metropolitan area had a higher proportion of employed individuals and higher levels of education. Northern municipalities had a higher prevalence of illnesses and anxiolytic and anti-psychotic treatments. Dysfunctionality frequencies did not differ significantly by area. However, a higher prevalence of 13 nursing diagnoses was observed in the north. A high number of correlations were observed between population characteristics, dysfunctionality, and prevalent diagnoses. Finally, the frequencies of dysfunctionality in the population and the most common care needs were mapped by municipality. This research sought to ascertain whether there was an unequal distribution of these two aspects among HCCPs in order to gain a deeper epidemiological understanding of them from a family and community perspective using standardised nursing languages. This study was not registered.

A time-resolved multi-omics atlas of transcriptional regulation in response to high-altitude hypoxia across whole-body tissues

High-altitude hypoxia acclimatization requires whole-body physiological regulation in highland immigrants, but the underlying genetic mechanism has not been clarified. Here we use sheep as an animal model for low-to-high altitude translocation. We generate multi-omics data including whole-genome sequences, time-resolved bulk RNA-Seq, ATAC-Seq and single-cell RNA-Seq from multiple tissues as well as phenotypic data from 20 bio-indicators. We characterize transcriptional changes of all genes in each tissue, and examine multi-tissue temporal dynamics and transcriptional interactions among genes. Particularly, we identify critical functional genes regulating the short response to hypoxia in each tissue (e.g., PARG in the cerebellum and HMOX1 in the colon). We further identify TAD-constrained cis-regulatory elements, which suppress the transcriptional activity of most genes under hypoxia. Phenotypic and transcriptional evidence indicate that antenatal hypoxia could improve hypoxia tolerance in offspring. Furthermore, we provide time-series expression data of candidate genes associated with human mountain sickness (e.g., BMPR2) and high-altitude adaptation (e.g., HIF1A). Our study provides valuable resources and insights for future hypoxia-related studies in mammals.

Prevalence of pulmonary hypertension in COPD patients living at high altitude

BACKGROUND

Pulmonary hypertension (PH) is associated with poor prognosis for patients with chronic obstructive pulmonary disease (COPD). Most of the knowledge about PH in COPD has been generated at sea level, with limited information associated with high altitude (HA).

OBJECTIVES

To assess the prevalence and severity of PH in COPD patients living in a HA city (2,640 m).

METHODS

Cross-sectional study in COPD patients with forced expiratory volume in the first second / forced vital capacity ratio (FEV1/FVC) post-bronchodilator <0,7. Transthoracic echocardiography (TTE), spirometry, carbon monoxide diffusing capacity, and arterial blood gasses tests were performed. Patients were classified according to the severity of airflow limitation. PH was defined by TTE as an estimated systolic pulmonary artery pressure (sPAP) > 36 mmHg or indirect PH signs; severe PH as sPAP > 60 mmHg; and disproportionate PH as an sPAP > 60 mmHg with non-severe airflow limitation (FEV1 > 50% predicted).

RESULTS

We included 176 COPD patients. The overall estimated prevalence of PH was 56.3% and the likelihood of having PH increased according to airflow-limitation severity: mild (31.6%), moderate (54.9%), severe (59.6%) and very severe (77.8%) (p = 0.038). The PH was severe in 7.3% and disproportionate in 3.4% of patients.

CONCLUSIONS

The estimated prevalence of PH in patients with COPD at HA is high, particularly in patients with mild to moderate airflow limitation, and greater than that described for COPD patients at low altitude. These results suggest a higher risk of developing PH for COPD patients living at HA compared to COPD patients with similar airflow limitation living at low altitude.

The cardiovascular system at high altitude: A bibliometric and visualization analysis

BACKGROUND

When exposed to high-altitude environments, the cardiovascular system undergoes various changes, the performance and mechanisms of which remain controversial.

AIM

To summarize the latest research advancements and hot research points in the cardiovascular system at high altitude by conducting a bibliometric and visualization analysis.

METHODS

The literature was systematically retrieved and filtered using the Web of Science Core Collection of Science Citation Index Expanded. A visualization analysis of the identified publications was conducted employing CiteSpace and VOSviewer.

RESULTS

A total of 1674 publications were included in the study, with an observed annual increase in the number of publications spanning from 1990 to 2022. The United States of America emerged as the predominant contributor, while Universidad Peruana Cayetano Heredia stood out as the institution with the highest publication output. Notably, Jean-Paul Richalet demonstrated the highest productivity among researchers focusing on the cardiovascular system at high altitude. Furthermore, Peter Bärtsch emerged as the author with the highest number of cited articles. Keyword analysis identified hypoxia, exercise, acclimatization, acute and chronic mountain sickness, pulmonary hypertension, metabolism, and echocardiography as the primary research hot research points and emerging directions in the study of the cardiovascular system at high altitude.

CONCLUSION

Over the past 32 years, research on the cardiovascular system in high-altitude regions has been steadily increasing. Future research in this field may focus on areas such as hypoxia adaptation, metabolism, and cardiopulmonary exercise. Strengthening interdisciplinary and multi-team collaborations will facilitate further exploration of the pathophysiological mechanisms underlying cardiovascular changes in high-altitude environments and provide a theoretical basis for standardized disease diagnosis and treatment.

Correlation between serum inflammatory factors and cognitive function in patients with high-altitude polycythemia: A case-control study

The purpose of this study is to investigate the serum inflammatory factors in patients with high-altitude polycythemia (HAPC) and their correlation with cognitive function. The subjects were recruited and placed into a HAPC group and control group. Serum samples were collected, and inflammatory factors (interleukin-1beta [IL-1β], monocyte chemoattractant protein-1 [MCP-1], and tumor necrosis factor-alpha [TNF-α]) were measured using ELISA kits. The mini-mental State Examination (MMSE) was used to assess cognitive function. According to the MMSE scores, HAPC group was further divided into normal cognitive function group (HNCF) and cognitive dysfunction group (HCDF). In comparison with the control group, the MMSE scores in the HAPC group were significantly low (P < .05), whereas the serum levels of IL-1β, MCP-1, and TNF-α were significantly high (P < .01). Among the HAPC group (n = 60), 21 belonged to the HCDF and 39 belonged to the HNCF. Compared with the HNCF, the IL-1β, MCP-1, and TNF-α in the HCDF were significantly increased (P < .01). The Pearson correlation analysis showed that inflammatory factors were positively correlated with hemoglobin, and negatively correlated with MMSE. Serum inflammatory cytokines IL-1, MCP-1, and TNF-α were increased in HAPC, and HAPC exhibited cognitive dysfunction. Considering chronic hypoxia environment influences the change of the red blood cell metabolic and inflammatory factor, red blood cells and inflammatory factor in plateau is likely to be affected by patients with vascular lesions, increase cognitive impairment.

Left ventricular strain changes at high altitude in rats: a cardiac magnetic resonance tissue tracking imaging study

BACKGROUND

Long-term exposure to a high altitude environment with low pressure and low oxygen could cause abnormalities in the structure and function of the heart. Myocardial strain is a sensitive indicator for assessing myocardial dysfunction, monitoring myocardial strain is of great significance for the early diagnosis and treatment of high altitude heart-related diseases. This study applies cardiac magnetic resonance tissue tracking technology (CMR-TT) to evaluate the changes in left ventricular myocardial function and structure in rats in high altitude environment.

METHODS

6-week-old male rats were randomized into plateau hypoxia rats (plateau group, n = 21) as the experimental group and plain rats (plain group, n = 10) as the control group. plateau group rats were transported from Chengdu (altitude: 360 m), a city in a plateau located in southwestern China, to the Qinghai-Tibet Plateau (altitude: 3850 m), Yushu, China, and then fed for 12 weeks there, while plain group rats were fed in Chengdu(altitude: 360 m), China. Using 7.0 T cardiac magnetic resonance (CMR) to evaluate the left ventricular ejection fraction (EF), end-diastolic volume (EDV), end-systolic volume (ESV) and stroke volume (SV), as well as myocardial strain parameters including the peak global longitudinal (GLS), radial (GRS), and circumferential strain (GCS). The rats were euthanized and a myocardial biopsy was obtained after the magnetic resonance imaging scan.

RESULTS

The plateau rats showed more lower left ventricular GLS and GRS (P < 0.05) than the plain rats. However, there was no statistically significant difference in left ventricular EDV, ESV, SV, EF and GCS compared to the plain rats (P > 0.05).

CONCLUSIONS

After 12 weeks of exposure to high altitude low-pressure hypoxia environment, the left ventricular global strain was partially decreased and myocardium is damaged, while the whole heart ejection fraction was still preserved, the myocardial strain was more sensitive than the ejection fraction in monitoring cardiac function.