HAPE is the most lethal of the altitude illnesses. Because the condition is easily reversible with descent and oxygen, the cause of death is usually lack of early recognition, misdiagnosis, or inability to descend to a lower altitude. Litigation commonly results from HAPE deaths, a fact worth considering for physicians involved in such cases.
EPIDEMIOLOGY The incidence of HAPE varies from less than 1 in 10,000 skiers in Colorado to 2 to 3 percent of climbers on Mt. McKinley, and was reported as high as 15 percent in some regiments in the Indian army who were airlifted to high altitude during the Indian/Chinese war. Women appear less susceptible than men. Risk factors include heavy exertion, rapid ascent, cold, excessive salt ingestion, use of sleeping medication, and a previous history indicating inherent individual susceptibility. Such susceptibility was recently related to immunogenetic factors,10 as well as to physiologic factors.11 Preexisting respiratory infection predisposes children to HAPE.12
CLINICAL PRESENTATION (T§b.!e...191:3) Early in the course of illness, when the edema is still interstitial or localized, the victim develops a dry cough, decreased exercise performance, dyspnea on exertion, increased recovery time from exercise, and localized rales, usually in the right midlung field. Late in the course of the illness, there develops tachycardia, tachypnea, and dyspnea at rest, marked weakness, productive cough, cyanosis, and more generalized rales. As hypoxemia worsens, consciousness becomes impaired. Victims usually become comatose and then die. Early diagnosis is critical, and decreased exercise performance and dry cough is enough to raise the suspicion of early HAPE. The typical victim is strong and fit and may or may not have symptoms of AMS before onset of HAPE. The condition typically worsens at night and is noticed most commonly on the second night at a new altitude. Unfortunately, rales may not be audible in 30 percent of persons with HAPE at rest but can be elicited immediately after a short bout of exercise. Fever up to 38.5°C is common, and tachycardia and tachypnea generally correlate with the severity of illness. On cardiac auscultation, a prominent P2 and right ventricular heave may be appreciated. ECG generally reveals right axis deviation and a right ventricular strain pattern consistent with acute pulmonary hypertension. Chest x-ray findings progress from interstitial to localized alveolar to generalized alveolar infiltrates as the illness progresses from mild to severe. 13
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