EXERCISE-INDUCED VA Q INEQUALITY IN SUBJECTS WITH PRIOR HIGH-ALTITUDEPULMONARY-EDEMA/

Ventilation-perfusion (VA/Q) mismatch has been shown to increase durin g exercise, especially in hypoxia. A possible explanation is subclinic al interstitial edema due to high pulmonary capillary pressures. We hy pothesized that this may be pathogenetically similar to high-altitude pulmonary edema (HAPE) so that HAPE-susceptible people with higher vas cular pressures would develop more exercise-induced VA/Q mismatch. To examine this, seven healthy people with a history of HAPE and nine wit h similar altitude exposure but no HAPE history (control) were studied at rest and during exercise at 35, 65, and 85% of maximum 1) at sea l evel and then 2) after 2 days at altitude (3,810 m) breathing both nor moxic (inspired Po-2=148 Torr) and hypoxic (inspired PO2=91 Torr) gas at both locations. We measured cardiac output and respiratory and iner t gas exchange. In both groups, VA/Q mismatch (assessed by log standar d deviation of the perfusion distribution) increased with exercise. At sea level, log standard deviation of the perfusion distribution was s lightly higher in the HAPE-susceptible group than in the control group during heavy exercise. At altitude, these differences disappeared. Be cause a history. of HAPE was associated with greater exercise-induced VA/Q mismatch and higher pulmonary capillary pressures, our findings a re consistent with the hypothesis that exercise-induced mismatch is du e to a temporary extravascular fluid accumulation.