Silent Hypoxemia in High-Altitude Pulmonary Edema: A Case Report

We report a case of a trekker who ascended to Tilicho Lake (4919 m) from Kathmandu (1400 m) in 3 days. On day 3, he descended to Shree Kharka (4045 m). The following day, he trekked to Yak Kharka (4025 m) where, although he had no symptoms, he measured his own oxygen saturation (SpO₂) at 72% in ambient air. Overnight, his SpO₂ ranged from 75-80% on oxygen 2L/min via nasal cannula. The next day his SpO₂ dropped to 47% while still on oxygen. He descended on horseback to Manang (3500 m), where his SpO₂ was 70% on room air. He was diagnosed with high-altitude pulmonary edema (HAPE). He was treated with oxygen, 4L by nasal cannula, and nifedipine. The following day, he flew to Kathmandu, where he made a full recovery. Trekkers may develop life-threatening HAPE without obvious symptoms or signs. Slow ascent can decrease the likelihood of developing HAPE, but trekkers do not always follow the recommended ascent rate. Early detection, by history and physical examination and with point-of-care ultrasound (POCUS), if available, is critical in resource-limited regions such as ours. The keys to managing HAPE are early recognition and management, including descending to a lower altitude as soon as possible.