Aconcagua (6962 m) during January 2009 who signed written informed consent. Exclusion criteria: pregnant women, age ฯฝ18 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 SaO 2 : 86.3%, mean 6MWD: 482.9 m, mean postexercise SaO 2 : 80.8%, and mean โฌSaO 2 : ฯช5.5%. Among climbers who did not reach the summit, mean resting SaO 2 : 83.9%, mean 6MWD: 451.8 m, mean postexercise SaO 2 : 76.5%, and mean โฌSaO 2 : ฯช7.4%. Between the 2 groups, the differences of the mean were as follows: resting SaO 2 , ฯช2.3% (95% CI: ฯช4.4 to ฯช0.3; P ฯญ .013); 6MWD, 31.1m (95% CI: ฯช9.4 to 71.5; P ฯญ .065); postexercise SaO 2 , ฯช4.3% (95% CI: ฯช6.6% to ฯช1.9%; P ฯญ .0003); and โฌSaO 2 , ฯช1.9% (95% CI ฯช4.2 to 0.4; P ฯญ .048).
Conclusions.-Climbers who successfully reached the summit of Aconcagua were less hypoxic and performed better on 6MWT compared with those who did not.