PULMONARY HEMODYNAMIC-RESPONSE TO EXERCISE IN SUBJECTS WITH PRIOR HIGH-ALTITUDE PULMONARY-EDEMA

Individuals with a prior history of (susceptible to) high altitude pul monary edema (HAPE-S) have high resting pulmonary arterial pressures, but little data are available on their vascular response to exercise. We studied the pulmonary vascular response to exercise in seven HAPE-S and nine control subjects at sea level and at 3,810 m altitude. At ea ch location, both normoxic (inspired PO2=148 Torr) and hypoxic (inspir ed PO2=91 Torr) studies were conducted. Pulmonary hemodynamic measurem ents included pulmonary arterial and pulmonary arterial occlusion pres sures. A multiple regression analysis demonstrated that the pulmonary arterial pressure reactivity to exercise was significantly greater in the HAPE-S group. This reactivity was not influenced by altitude or ox ygenation, implying that the response was intrinsic to the pulmonary c irculation. Pulmonary arterial occlusion pressure reactivity to exerci se was also greater in the HAPE-S group, increasing with altitude but independent of oxygenation. These findings suggest an augmented flow-d ependent pulmonary vasoconstriction and/or a reduced vascular cross-se ctional area in HAPE-S subjects.