Postexercise Peripheral Oxygen Saturation After Completion of the 6-Minute Walk Test Predicts Successfully Reaching the Summit of Aconcagua

Objective The 6-minute walk test (6MWT) is a single measurement of functional status in patients with cardiovascular disease. It has not been studied at high altitude. We investigate the screening value of 6-minute walk distance (6MWD) and postexercise vital sign (VS) measurements as predictors of successfully reaching the summit or development of acute mountain sickness (AMS) on Aconcagua (6962 m). Methods Prospective observational cohort in Aconcagua Provincial Park, Argentina. Adults climbing the normal route who registered with base camp physicians were included. There were no exclusion criteria. VSs were measured before (resting) and after (postexercise) completion of 6MWT while volunteers acclimatized at Plaza de Mulas base camp (4365 m). Volunteers proceeded towards the summit at their own pace and upon descent returned a questionnaire with maximum altitude reached and Lake Louise AMS Self-report Score (LLSelf). Results One hundred twenty-four volunteers completed the 6MWT. Sixty-four volunteers (51.6%) completed questionnaires; 56% summited. Median LLSelf was 4 (IQR: 3.0–6.5). There was no association between any resting or postexercise VS measurements and AMS. However, mean postexercise SpO2 was 80.8% in summiters and 76.4% in nonsummiters, a difference of −4.4% (95% CI: −6.7 to −2.0, p = 0.0005). Postexercise SpO2 < 75% had 97.2% sensitivity and negative likelihood ratio of 0.086 in predicting the outcome of successfully reaching the summit: only one climber with SpO2 < 75% successfully reached the summit. Conclusions This study provides the first published data on 6MWD recorded in the field at high altitude. Postexercise SpO2 < 75% may be a useful screening test for predicting the outcome of successfully reaching the summit of Aconcagua.