High altitude pulmonary edema: Known for short as HAPE, the accumulation in the lungs of extravascular fluid (fluid outside of blood vessels) at high altitude, a consequence of rapid altitude ascent, especially when that ascent is accompanied by significant exercise.
HAPE leads to dyspnea (shortness of breath), cough, tachycardia (fast heart rate) and decreased arterial oxygen levels. HAPE varies in degree from very mild to potentially fatal.
Some people may be genetically susceptible to HAPE. People who develop HAPE have smaller lungs, higher pulmonary artery pressures, and higher pulmonary artery wedge pressures during exercise at sea level than those who do not develop HAPE.
The incidence of HAPE has been analyzed in a prospective study of people climbing a 4500-meter mountain. 15% of climbers had clearcut evidence of HAPE from examination of the chest (by stethoscope or X-ray) after their climb. There is probably a risk of HAPE for most climbers if the rate of ascent and degree of physical effort are great enough. (Lancet Jan. 24, 2002).
The planning and pacing of ascents is of critical importance. HAPE tends to be less frequent on well-planned, gradual ascents to much greater heights, despite the greater degree of hypoxemia (low blood oxygen levels).