Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2021 Apr;9(7):e14809.
doi: 10.14814/phy2.14809.

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

Alexandra B Cobb  1 , Denny Z H Levett  1   2   3   4 , Kay Mitchell  1   2   3   4 , Wynne Aveling  5 , Daniel Hurlbut  1 , Edward Gilbert-Kawai  1 , Philip J Hennis  1 , Monty G Mythen  1 , Michael P W Grocott  1   2   3   4 , Daniel S Martin  1   6   7 ; Caudwell Xtreme Everest, Xtreme Everest 2009, Xtreme Everest 2 investigators
Collaborators, Affiliations

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

Alexandra B Cobb et al. Physiol Rep. 2021 Apr.

Abstract

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.

Keywords: altitude; altitude sickness; exercise; hypoxia.

PubMed Disclaimer

Figures

FIGURE 1
FIGURE 1
The planned ascent profile for all participants. Daily ascent profile to altitude. In summary, participants went by airplane from Kathmandu (1300 m) to Lukla (2860 m), then ascended on foot. Rest days were inserted into the schedule to allow other experiments to be performed, and to reduce the anticipated incidence of AMS by allowing additional time for acclimatisation (Gilbert‐Kawai et al., 2015; Levett et al., 2010)
FIGURE 2
FIGURE 2
Flow diagram detailing the number of participants included in the final analysis. EBC, Everest Base Camp
FIGURE 3
FIGURE 3
Incidence of acute mountain sickness by trek day. LLS, Lake Louise score
FIGURE 4
FIGURE 4
Overall mean (±SEM) change in measured physiological variables in all participants during ascent to high altitude. Solid line = at rest, pre‐exercise; dotted line = at end of exercise. Blood pressure was only measured at rest, prior to exercise
FIGURE 5
FIGURE 5
Receiver operator characteristics curve for the moderate to severe AMS logistic regression model. Independent variables included: Resting SpO2, end‐exercise SpO2, resting respiratory rate, end‐exercise respiratory rate, systolic blood pressure, delta heart rate and no previous altitude exposure >5000 m. Area under the curve = 0.735 (95% CI 0.667–0.804, p < 0.001)
See this image and copyright information in PMC

Comment in

References

    1. Basnyat, B. , Lemaster, J. , & Litch, J. (1999). Everest or bust: a cross sectional, epidemiological study of acute mountain sickness at 4232 meters in the Himalayas. Aviation, Space & Environmental Medicine, 70, 867–873. - PubMed
    1. Burtscher, M. , Flatz, M. , & Faulhaber, M. (2004). Prediction of susceptibility to acute mountain sickness by SaO2 values during short‐term exposure to hypoxia. High Altitude Medicine & Biology, 5, 335–340. - PubMed
    1. Burtscher, M. , Szubski, C. , & Faulhaber, M. (2008). Prediction of the susceptibility to AMS in simulated altitude. Sleep and Breathing, 12, 103–108. - PubMed
    1. Chen, H. C. , Lin, W. L. , Wu, J. Y. , Wang, S. H. , Chiu, T. F. , Weng, Y. M. , Hsu, T. Y. , & Wu, M. H. (2012). Change in oxygen saturation does not predict acute mountain sickness on Jade Mountain. Wilderness & Environmental Medicine, 23, 122–127. - PubMed
    1. Faulhaber, M. , Wille, M. , Gatterer, H. , Heinrich, D. , & Burtscher, M. (2014). Resting arterial oxygen saturation and breathing frequency as predictors for acute mountain sickness development: A prospective cohort study. Sleep and Breathing, 18, 669–674. - PubMed

Publication types

LinkOut - more resources