Predictive Factors of Successful Summiting on Aconcagua

Abstract

Background

Base camp physicians and expedition leaders commonly measure static vital signs when screening mountaineers prior to summit attempts. Single measurements of functional status such as the 6-minute walk test (6MWT) and postexercise vital signs (VS) have not been described at high altitude.

Objective

Determine if postexercise VS or 6-minute walk distance (6MWD) predicts successful summiting at extreme altitude on Aconcagua.

Methods

Prospective observational cohort study. Setting: Plaza de Mulas base camp (4365 m) Aconcagua Provincial Park, Argentina. Inclusion criteria: volunteer trekkers to Aconcagua (6962 m) during January 2009 who signed written informed consent. Exclusion criteria: pregnant women, age <18 years. Study protocol: VS were measured before and after completion of a 6MWT using a standardized protocol on a 40-m course while acclimatizing at 4365 m. Subjects proceeded towards the summit at their own pace and returned a questionnaire with maximum altitude reached upon descent. Statistical analysis: means, 95% confidence intervals, and t tests were calculated using Stata.

Results

Sixty-five subjects completed the 6MWT and returned their questionnaires. Thirty-six (55%) climbers reached the summit (6962 m). Mean maximum altitude reached was 6487 m. Among climbers who reached the summit, mean resting Sao₂: 86.3%, mean 6MWD: 482.9 m, mean postexercise Sao₂: 80.8%, and mean ΔSao₂: −5.5%. Among climbers who did not reach the summit, mean resting Sao₂: 83.9%, mean 6MWD: 451.8 m, mean postexercise Sao₂: 76.5%, and mean ΔSao₂: −7.4%. Between the 2 groups, the differences of the mean were as follows: resting Sao₂, −2.3% (95% CI: −4.4 to −0.3; P = .013); 6MWD, 31.1m (95% CI: −9.4 to 71.5; P = .065); postexercise Sao₂, −4.3% (95% CI: −6.6% to −1.9%; P = .0003); and ΔSao₂, −1.9% (95% CI −4.2 to 0.4; P = .048).

Conclusions

Climbers who successfully reached the summit of Aconcagua were less hypoxic and performed better on 6MWT compared with those who did not. Future studies with larger sample sizes are needed to validate these results.