Characteristics of Climbers with High Altitude Pulmonary Edema on Mount Aconcagua

Introduction- Mount Aconcagua (6961 m) in Argentina is the highest peak in the Americas, and more than 3000 climbers attempt to summit annually. High altitude pulmonary edema (HAPE) is a leading cause of mortality and evacuation on Aconcagua.Objective- This study sought to describe the characteristics of climbers who developed HAPE on Aconcagua to aid in future prevention efforts.Methods- Climbers diagnosed with HAPE in January 2024 were surveyed regarding demographics, preparation, acclimatization, and illness. Healthy climbers on Aconcagua also were surveyed for the same period, providing a control population.Results- Seventeen climbers were diagnosed with HAPE. These climbers were similar to climbers without HAPE in age, sex, origin, home elevation, hypoxic tent use, staged ascent, recent virus exposure, fitness metrics, and ascent-rate plans. Climbers with HAPE spent fewer nights at the 4300-m base camp (3.6 vs 5.0 nights). Prior to developing HAPE, 71% of patients reported unresolved acute mountain sickness symptoms. HAPE onset median elevation was 5500 m, with a median of 8.0 days over 3000 m and a median lowest SpO2 of 60% at diagnosis. There was a nonsignificant trend between acetazolamide use and increased HAPE. All surveyed HAPE patients descended, required helicopter evacuation, and survived.Conclusion- This study examined climbers who developed HAPE on Mount Aconcagua, yielding implications for high altitude illness prevention efforts and further study. HAPE cases were associated with insufficient nights at the 4300-m base camp and unresolved acute mountain sickness symptoms. The relationship between acetazolamide and HAPE warrants further study on Aconcagua.