High Altitude Pulmonary Edema (HAPE)

High altitude pulmonary edema (HAPE) typically shows up in otherwise healthy patients after rapid ascent (e.g., mountain-climbing) with subsequent coughing, tachycardia, hypoxemia, and fatigue. These symptoms are often attributed to overexertion or dehydration, but it’s important to recognize the underlying physiology.

At its core, altitude exposes the lung to hypoxia and triggers hypoxic pulmonary vasoconstriction (HPV). In most people, that response is modest and evenly distributed; however, in susceptible patients, it is exaggerated and uneven, driving pulmonary pressures up and shunting flow into vulnerable regions. Fluid and protein leak into the alveoli, leading to V/Q mismatch and impairments in gas exchange.

Treatment is centered around descent and supplemental oxygen to improve hypoxia and blunt pulmonary vasoconstriction. If descent is not immediately possible, portable hyperbaric chambers can simulate it and work as a bridge. Nifedipine has also been used to lower pulmonary pressures and reduce the risk of HAPE in prevention studies. Other agents have signals in selected groups, but they should never distract from the fundamentals: oxygen, descent, warmth, and stopping exertion.

Like so much else, prevention is the best treatment. Slow ascent and built-in acclimatization days are essential. Prophylaxis can help, but only as an adjunct to judgment, not a replacement for it.

Here’s a chest CT scan showing the classic pulmonary edema associated with HAPE.

Here are some PubMed IDs to review the data: 1922223, 17015867, 1483797, 23720264