High altitude medicine & biology最新文献

Cornwell, William, Aaron L Baggish, Christoph Dehnert, Benjamin D Levine, and Andrew M Luks. Clinical Conundrum: Climbing at the Extremes of High Elevation with Nonischemic Cardiomyopathy. High Alt Med Biol. 00:00-00, 2024.

Häfliger, Alina, Aline Buergin, Laura C. Mayer, Maamed Mademilov, Mona Lichtblau, Talantbek Sooronbaev, Silvia Ulrich, Konrad E. Bloch, and Michael Furian. Sex-specific difference in health-related altitude-effects and their prevention by acetazolamide. Data from a randomized controlled trial. High Alt Med Biol. 00:00-00, 2024. Background: Women are underrepresented in studies on acute mountain sickness (AMS), altitude-induced sleep-disordered breathing and preventive acetazolamide use. Methods: We analyzed sex-specific altitude-effects in participants of a randomized, placebo-controlled, double-blind trial in healthy lowlanders >40 years. Participants took 375 mg/day acetazolamide or placebo starting 24 hours before ascent to and while staying 2 days at 3,100 m. Main outcomes of this analysis were sex-specific incidence of AMS (Lake Louise score ≥3), nocturnal pulse oximetry (SpO₂) and apnea-hypopnea index (AHI) at 3,100 m. Results: With placebo, 30 of 119 (25%) women and 4 of 51 (8%) men developed AMS (p = 0.009 between sexes) at 3,100 m. Among women assigned to placebo, SpO₂ (mean ± SE 84 ± 0%) and AHI (16.9 ± 1.3/h) in night 1 at 3,100 m were lower compared to men (SpO₂ 86 ± 0%; AHI 28.3 ± 1.9/h), despite similar baseline values at 760 m. Mean between-sex difference in altitude-effects (women-men) in SpO₂ was -1.4% (95% CI, -2.4 to -0.3%); AHI -10.7/h (95% CI, -15.7 to -5.7/h). The impact of acetazolamide on AMS was not significant for either sex but acetazolamide improved AHI in men (difference men-women, -9.8/h [95% CI, -16.8 to -2.7/h]). Conclusion: This study suggests sex-specific differences in altitude-induced hypoxemia, periodic breathing, AMS incidence, and in the response to preventive acetazolamide treatment.

Kansara, Nikunj Kumar, Anurag Timothy, Rijesh Unnithan, and Manas Chatterjee. Unraveling high altitude-induced thromboembolic disorders: polycythemia or complex mechanisms?. High Alt Med Biol. 00:00-00, 2024. Background: Thromboembolic disorders (TEDs) occurring at high altitudes due to exposure to hypoxic environments pose a significant challenge for clinicians in high-altitude area. Hypobaric hypoxia often leads to acquired erythrocytosis, which is believed to increase the incidence of thrombosis. This study aims to examine the relationship between thromboembolic events and erythrocytosis. Methodology: A prospective study was conducted, including all the patients admitted to Siachen hospital for TEDs from January 01, 2022, to December 31, 2022. Data on height, duration of the stay, hemoglobin (Hb), and packed cell volume levels at the time of admission were recorded. Results: A total of 35 cases were enrolled during the study period. The average age of the patients was 29.10 years (standard deviation: 6.06). The mean deployment height was 17,300 ft, with a range of 12,000 ft-21,600 ft. The average duration of stay was 73 days, ranging from 7 to 162 days. The mean Hb level was 18 g/dl (SD: 2.64), with a range of 12.4 g/dl-22.4 g/dl. Twenty-five cases of thrombotic events (71.4%) occurred with normal Hb levels (<17.5 mg/dl), compared with 10 cases (28.6%) with Hb levels >17.5 mg/dl. Conclusion: Prolonged stays at high altitudes and exposure to hypobaric hypoxia are major stressors. The study suggests that it is not elevated Hb levels, but rather the body's lack of an appropriate physiological response, that contributes to the development of thromboembolic events.

Stauffer, Emeric, François Caton, Raphael Marlu, Aurélien Pichon, Landry Seyve, Michael Furian, Aymeric Paillisser, Florence Berquet, Jeremy De Abreu, Blandine Deschamps, Benoit Polack, Philippe Connes, Paul Robach, Stéphane Doutreleau, Julien V Brugniaux, Samuel Verges, and Benoit Champigneulle.Acclimatized lowlanders exhibit a hypocoagulable profile after a passive ascent at high altitude. High Alt Med Biol. 00:00-00, 2024. Background: Discordant results have been previously reported regarding the impact of high-altitude (HA) exposure on coagulation. We aimed to investigate changes in coagulation parameters in lowlanders exposed to HA for 14 days using a combination of dynamic coagulation assays and conventional in vitro tests. Material and Methods: We assessed coagulation in 10 lowlanders using whole-blood rotational thromboelastometry (ROTEM), thrombin generation assay (TGA) on poor-platelet plasma, and conventional coagulation tests. Tests were performed at low altitude (LA, 210 m) and at the end of a 14-day sojourn at HA, including passive ascents to 3,800 m for 6 days and then to 5,100 m for 8 days. Results: Conventional tests revealed significant changes in coagulation factors and inhibitors after HA exposure, although these changes remained within normal ranges. ROTEM assays demonstrated a delayed clot initiation in EXTEM/FIBTEM, without any alteration in clot firmness, in HA versus LA (p < 0.01). TGA changes showed an increase in time to peak (p < 0.01), a decrease in endogenous thrombin potential (p < 0.05), and a decrease in thrombin peak (p < 0.001). Conclusions: We found no evidence of hypercoagulability in lowlanders after a 14-day sojourn at HA. In contrast, dynamic coagulation assays (ROTEM and TGA) revealed a hypocoagulable pattern.

Ren, Hong, Xi-Yue Yang, Rui Su, HaiLin Ma, and Hao Li. Temporal Effects of Hypoxia Exposure at High Altitudes on Compensatory Brain Function: Evidence from Functional Connectivity of Resting-State EEG Brain Networks. High Alt Med Biol. 00:00-00, 2024. Background: The aim of this study was to investigate the effects of prolonged exposure to hypobaric hypoxia at high altitude on changes in brain function measured by electroencephalography (EEG), focusing specifically on the resting-state brain network functional connectivity and compensatory adaptations in brain function among individuals with varying durations of high altitude residency. Methods: In study I, 64 participants were divided into high-altitude group (HG) and low-altitude group (LG). Ninety-six long-term migrants residing at an altitude of 3,650 m were recruited for studyII and categorized into three groups based on their duration of stay at high altitude: group A (1-2 years), group B (8-10 years), and group C (18-20 years). Resting-state EEG data were collected from each participant, and functional connectivity analysis was conducted using Phase Locking Value. Results: Study I showed that participants with HG had stronger functional connectivity in the occipital lobe than those with LG (p < 0.05). The study II findings indicate that there were significant differences in functional connectivity strength among the frontal and occipital lobes in groups A, B, and C across the α, β, δ, and θ frequency bands. Specifically, the functional connectivity strength of the frontal lobe was significantly higher in group A compared with group B, and in group B compared with group C (p < 0.05). Additionally, the functional connectivity of the occipital lobe was significantly higher in group C compared with group B, and in group B compared with group A (p < 0.05). Conclusions: The consistent results of the whole frequency band suggest that the individual's occipital lobe function is enhanced to compensate for the damage of frontal lobe function, so as to better adapt to the extreme environment at high altitude.

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.

Guo, Yan, Chao Yu, Zhongsheng Lu, Menglan Zhang, Qiang Zhang, and Xiao Liu. Zinc homeostasis plays important roles in hypoxia tolerance: A study conducted clinically and in vitro. High Alt Med Biol. 00:00-00, 2024. Objective: High-altitude environments pose significant challenges to human physiology due to reduced oxygen availability, often resulting in altitude-related illnesses such as high-altitude cerebral edema (HACE). This study focuses on understanding the role of zinc homeostasis in enhancing hypoxia tolerance, which may be pivotal in mitigating the adverse effects of such illnesses. Methods: The study involved healthy individuals from high-altitude (4,500-5,000 m) and low-altitude areas (0-200 m), as well as patients with HACE. Blood samples were collected and analyzed. Additionally, a hypoxic model was developed using human brain microvascular endothelial cells (HBMECs), and zinc intervention was implemented. Results: In the blood samples of patients with HACE and those of healthy individuals, there were over 4,000 differentially expressed genes (DEGs), with more than 300 of them linked to zinc. Among these zinc-associated genes, only carbonic anhydrase I (CA1) exhibited a substantial upregulation in expression, while the expression of others was notably downregulated. Compared with the high-altitude group, hemoglobin (Hb) (14.7 vs. 19.5 g/dl) and plasma zinc (37.0 vs. 94.0 mmol/dl) were lower in HACE, while CA1 (55.4 vs. 8.6 g/l) was elevated (p < 0.01). In vitro studies confirmed that exposure to hypoxia (O₂ 8%-8.5%, 24 hours) inhibited HBMECs proliferation and migration, increased apoptosis and necrosis, and led to abnormal expression of CA1 and various zinc transport proteins. However, zinc intervention (6 μM, 24 hours) significantly mitigated these adverse effects and improved the cell's ability to tolerate hypoxia. Conclusion: Zinc homeostasis was crucial for hypoxia tolerance. Proper zinc supplementation could potentially alleviate symptoms associated with hypoxia intolerance, such as altitude sickness, but further confirmation was needed.

Szymczak, Robert K., Magdalena Sawicka, and Małgorzata Jelitto. Recurrent pulmonary embolism at high altitude in a mountaineer with hereditary thrombophilia. High Alt Med Biol. 25:345-347, 2024.-It is speculated that high-altitude travel is an independent risk factor for thrombosis. Mountaineering-specific factors, such as hypoxia, cold, and immobilization, may interact with patient-specific risk factors and contribute to thrombus formation. We present the case of a mountaineer with hereditary thrombophilia who experienced recurrent pulmonary embolism during high-altitude expeditions.

Ebert-Santos, Christine, and Ana Campos. Ileus at altitude. High Alt Med Biol. 25:342-344, 2024.-Autoimmune myasthenia gravis (MG) is a condition commonly caused by the production of antibodies that block acetylcholine receptors. Until recently, gastrointestinal (GI) symptoms were considered rare in myasthenia gravis, but are now being proposed as an early identification tool. Presented here is a case study that exemplifies GI symptoms in MG, exacerbated by low barometric pressure at altitude. This illustrates the need to identify GI symptoms earlier in MG patients, as well as the need for providers at high altitude to be aware of these manifestations of MG.