Continuous positive airway pressure treatment for acute mountain sickness at 4240 m in the Nepal Himalaya.

Acute mountain sickness (AMS) is very common at altitudes above 2500 m. There are few treatment options in the field where electricity availability is limited, and medical assistance or oxygen is unavailable or difficult to access. Positive airway pressure has been used to treat AMS at 3800 m. We hypothesized that continuous positive airway pressure (CPAP) could be used under field conditions powered by small rechargeable batteries. Methods Part 1. 5 subjects trekked to 3500 m from 2800 m in one day and slept there for one night, ascending in the late afternoon to 3840 m, where they slept using CPAP 6-7 cm via mask. The next morning they descended to 3500 m, spent the day there, ascended in late afternoon to 3840 m, and slept the night without CPAP. Continuous overnight oximetry was recorded and the Lake Louise questionnaire for AMS administered both mornings. Methods Part 2. 14 trekkers with symptoms of AMS were recruited at 4240 m. All took acetazolamide. The Lake Louise questionnaire was administered, oximetry recorded, and CPAP 6-7 cm was applied for 10-15 min. CPAP was used overnight and oximetry recorded continuously. In the morning the Lake Louise questionnaire was administered, and oximetry recorded for 10-15 min. The equipment used in both parts was heated, humidified Respironics RemStar® machines powered by Novuscell™ rechargeable lithium ion batteries. Oximetry was recorded using Embletta™ PDS. Results Part 1. CPAP improved overnight Sao2 and eliminated AMS symptoms in the one subject who developed AMS. CPAP was used for 7-9 h and the machines operated for >8 h using the battery. Results Part 2. CPAP use improved Sao2 when used for 10-15 min at the time of recruitment and overnight CPAP use resulted in significantly reduced AMS symptoms. Conclusion. CPAP with rechargeable battery may be a useful treatment option for trekkers and climbers who develop AMS.