It usually takes a few days to develop, and is exacerbated by over exertion. In bad cases, you can hear gurgling of fluid in the lungs, and the victim brings up a bloody sputum. This is a serious condition, which can kill in hours. The victim drowns in his own juices. HAPE is best avoided by gradual ascent.
Treatment is immediate descent by several thousand feet and oxygen if available.
Too Much of a Good Thing T he body also responds to the lower oxygen levels by putting more red blood cells into circulation. Up to a point, this is a good thing. However, if it goes too far, the blood becomes thick and prone to clotting. Clots which get dislodged float around and can cause strokes, heart attacks, and pulmonary embolisms. All bad juju.