Objective During a high-altitude expedition, the association of cardiopulmonary exercise testing (CPET) parameters with the risk of developing acute mountain sickness (AMS) and the chance of reaching the summit were investigated.
Methods Thirty-nine subjects underwent maximal CPET at lowlands and during ascent to Mount Himlung Himal (7126 m) at 4844 m, before and after 12 days of acclimatisation, and at 6022 m. Daily records of Lake-Louise-Score (LLS) determined AMS. Participants were categorised as AMS+ if moderate to severe AMS occurred.
Results Maximal oxygen uptake (V̇O2max) decreased by 40.5%±13.7% at 6022 m and improved after acclimatisation (all p<0.001). Ventilation at maximal exercise (VEmax) was reduced at 6022 m, but higher VEmax was related to summit success (p=0.031). In the 23 AMS+ subjects (mean LLS 7.4±2.4), a pronounced exercise-induced oxygen desaturation (ΔSpO2exercise) was found after arrival at 4844 m (p=0.005). ΔSpO2exercise >-14.0% identified 74% of participants correctly with a sensitivity of 70% and specificity of 81% for predicting moderate to severe AMS. All 15 summiteers showed higher V̇O2max (p<0.001), and a higher risk of AMS in non-summiteers was suggested but did not reach statistical significance (OR: 3.64 (95% CI: 0.78 to 17.58), p=0.057). V̇O2max ≥49.0 mL/min/kg at lowlands and ≥35.0 mL/min/kg at 4844 m predicted summit success with a sensitivity of 46.7% and 53.3%, and specificity of 83.3% and 91.3%, respectively.
Conclusion Summiteers were able to sustain higher VEmax throughout the expedition. Baseline V̇O2max below 49.0 mL/min/kg was associated with a high chance of 83.3% for summit failure, when climbing without supplemental oxygen. A pronounced drop of SpO2exercise at 4844 m may identify climbers at higher risk of AMS.
- Exercise Test
Data availability statement
All data relevant to the study are included in the article or uploaded as supplementary information. Not applicable.
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TS and CTN are joint first authors.
Correction notice This article has been corrected since it published Online First. The author affiliations have been corrected.
Contributors TS mainly contributed to data analysis and wrote a substantial part of the manuscript. CTN performed statistical analysis, helped with data interpretation and contributed to major improvements of the manuscript. A-KB helped with data interpretation and critically reviewed multiple times the manuscript. UH, MPH, EP-H, JS, H-JK and TMM planned and conducted the field-study and were substantially involved in data acquisition during the expedition. Additionally, they critically reviewed the manuscript. JPH serves as the corresponding author and is the scientific director of the Swiss High-Altitude Medical Research Expedition. She was majorly involved in planning and conducting the study and data analysis. She majorly contributed to the manuscript and is responsible for the overall content.
Funding This project was funded by the Swiss Society of Mountain Medicine and the Inselspital Bern, Switzerland.
Competing interests None declared.
Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.
Provenance and peer review Not commissioned; externally peer reviewed.
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