Medical Screening of Climbers Who Later Develop High-Altitude Pulmonary Edema on Aconcagua

Brillhart, Aaron, Molly Enenbach, Javier Seufferheld, Bernabé Abramor, Peter Callas, Rodrigo Duplessis, Ian Guertin, Theodore A Hartridge, Roxana Pronce, Ana Saravia, and Scott E. McIntosh. Medical screening of climbers who later develop high-altitude pulmonary edema on Aconcagua. High Alt Med Biol. 00:00-00, 2026.

On Aconcagua (6,961 m), high-altitude pulmonary edema (HAPE) is the most frequent reason for medical evacuation. This study aimed to compare medical screening data of climbers who developed HAPE with those who did not and to identify trends to aid in illness prevention and climber safety.

De-identified medical screening data of Aconcagua climbers from 2024 to 25 were retrospectively reviewed, comparing climbers who developed HAPE with those who did not.

Fifty-three of 2,336 climbers developed HAPE (2.3%). Asymptomatic climbers screened at 4,300 m who later developed HAPE had lower mean oxygen saturation than controls (80% vs. 85%, p < 0.001) and higher mean heart rate (96 vs. 87 bpm, p < 0.001). Nonsignificant trends were noted with guided status (74% vs. 61%, p = 0.06), and prophylactic acetazolamide use (34% vs. 21%, unadjusted: p = 0.02, odds ratio [OR] 1.92, adjusted: p = 0.08, OR 1.74).

On Aconcagua, certain vital sign parameters, including oxygen saturation below 80% and tachycardia during asymptomatic screening at 4,300 m, could raise concern for later developing HAPE. Future research could clarify any association between HAPE, certain climber groups such as guided clients, ascent rate, and medication use. Gradual ascent should continue to be emphasized to facilitate acclimatization and prevent life-threatening altitude illness such as HAPE.