Response of enlarged alveolar vessels to acute hypoxia

Because the postulated mechanism of high altitude pulmonary edema is inhomogeneous vaconstriction and hyperperfusion of unconstricted vessels, pulmonary blood flow through vessels larger than 10 micron was determined at baseline and during acute hypoxia sufficient to reduce arterial oxygen saturation to 65%. Women demonstrated a uniform response of decreasing such flow, whereas responses in men were highly variable. Hyperperfusion of enlarged vessels during hypoxia is not an acute phenomenon in the majority of subjects and is therefore either unique to some individuals or a sub-acute occurrence.