Abstract

Cardiovascular and respiratory adjustments during maximal exercise test were studied before, during and after prolonged high altitude exposure (5000-7000 m). Seven subjects, aged 24.7 yrs (range 23-28), members of a Himalayan expedition, underwent a maximal symptom-limited exercise test on a bicycle, before departure, at 7th and 28th day of acclimatization and immediately after return to sea level (10-14 days). After 1 and 4 weeks at high altitude total work, maximal heart rate and systolic arterial pressure were significantly lower than before departure. Upon return total work remained lower (p<0,5), while maximal oxygen uptake, pulmonary ventilation and heart rate were not significantly different from before departure. Maximal systolic arterial pressure was significantly lower. During exercise, at the same work load, we observed, both at high altitude and upon return, heart rate higher than before departure. Not significantly different were the adjustments of systolic arterial pressure. We conclude that important cardiovascular changes occur during and after high altitude acclimatization: increasing work load, heart rate adjustments follow similar slope but at higher values, both during and after high altitude exposure. That is to counterbalance lower stroke volume, related, at high altitude, to reduced preload due to plasma volume contraction and, upon return, to a reduction in ventricular pump function during exercise. Verf.-Referat