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Physiological responses during ascent to high altitude and the incidence of acute mountain sickness

Cobb, A. B., Levett, D. Z. H., Mitchell, K. , Aveling, W., Hurlbut, D., Gilbert-Kawai, E., Hennis, P. J., Mythen, M. G., Grocott, M. P. W., Martin, D. S., Caudwell Xtreme Everest, Xtreme Everest 2009, Xtreme Everest 2 investigators, Newman, S. P. ORCID: 0000-0001-6712-6079 & et al. (2021). Physiological responses during ascent to high altitude and the incidence of acute mountain sickness. Physiological Reports, 9(7), article number e14809. doi: 10.14814/phy2.14809


Acute mountain sickness (AMS) occurs when there is failure of acclimatisation to high altitude. The aim of this study was to describe the relationship between physiological variables and the incidence of AMS during ascent to 5300 m. A total of 332 lowland-dwelling volunteers followed an identical ascent profile on staggered treks. Self-reported symptoms of AMS were recorded daily using the Lake Louise score (mild 3-4; moderate-severe ≥5), alongside measurements of physiological variables (heart rate, respiratory rate (RR), peripheral oxygen saturation (SpO2 ) and blood pressure) before and after a standardised Xtreme Everest Step-Test (XEST). The overall occurrence of AMS among participants was 73.5% (23.2% mild, 50.3% moderate-severe). There was no difference in gender, age, previous AMS, weight or body mass index between participants who developed AMS and those who did not. Participants who had not previously ascended >5000 m were more likely to get moderate-to-severe AMS. Participants who suffered moderate-to-severe AMS had a lower resting SpO2 at 3500 m (88.5 vs. 89.6%, p = 0.02), while participants who suffered mild or moderate-to-severe AMS had a lower end-exercise SpO2 at 3500 m (82.2 vs. 83.8%, p = 0.027; 81.5 vs. 83.8%, p < 0.001 respectively). Participants who experienced mild AMS had lower end-exercise RR at 3500 m (19.2 vs. 21.3, p = 0.017). In a multi-variable regression model, only lower end-exercise SpO2 (OR 0.870, p < 0.001) and no previous exposure to altitude >5000 m (OR 2.740, p-value 0.003) predicted the development of moderate-to-severe AMS. The Xtreme Everest Step-Test offers a simple, reproducible field test to help predict AMS, albeit with relatively limited predictive precision.

Publication Type: Article
Additional Information: This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2021 The Authors. Physiological Reports published by Wiley Periodicals LLC on behalf of The Physiological Society and the American Physiological Society
Publisher Keywords: altitude, altitude sickness, exercise, hypoxia
Subjects: Q Science > QP Physiology
Departments: School of Health & Psychological Sciences > Healthcare Services Research & Management
SWORD Depositor:
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