PULMONARY EDEMA BY ASCENDING TO HIGH ALTITUDES.

SUMMARY Acute pulmonary edema was observed in 36 young healthy persons after ascending to altitudes 13,700 feet or more above sea level. Most of them were born and living permanently at high altitudes and developed pulmonary edema on returning to the mountains after a relatively short stay at lower or sea levels. The clinical manifestations were usually severe and rapidly progressive disappearing in 24 to 48 hours with oxygen administration. The predominant roentgenologic appearance was a coarse mottling exudate, more confluent in both parahilar regions. The heart size remained normal. The electrocardiogram showed acute right ventricular overloading and primary disturbances of repolarization probably related to right ventricular myocardial ischemia. Cardiac catheterization performed in one patient during the recovery period at sea level, revealed normal pressures in the pulmonary artery and capillary bed. Necropsies performed in two patients showed severe pulmonary edema, extensive areas with hyaline membrane, thrombosis of distal arteries and septal capillaries and multiple preterminal arterioles. The left atrium and ventricle were normal and there was a moderate right ventricular hypertrophy usually found in the high altitude resident. Pulmonary edema of high altitude appears to be the result of a magnification of the hemodynamic changes occurring during a rapid exposure to an environment of hypoxia and low temperature. These changes would be an increase in cardiac output and pulmonary blood volume, pulmonary vasoconstriction at pre-capillary level with secondary pulmonary hypertension, and increased pulmonary capillary permeability.