Effect of intermittent hypoxia on cardiovascular adaptations and response to progressive hypoxia in humans.

The aim of the present study was to elucidate (1) the cardiovascular adaptations and response to hypoxic stimuli during short-term intermittent hypoxia and (2) whether the change in cardiovascular response to hypoxia is correlated to the change in hypoxic ventilatory chemosensitivity. Fourteen subjects were decompressed in a chamber to 432 torr, simulating an altitude of 4500 m, over a period of 30 min and were maintained at that pressure for 1 h daily for 7 days. Ventilatory (DeltaV(I)/DeltaSa(O2); Sa(O2) is arterial oxygen saturation), systolic and diastolic blood pressure (DeltaSBP/DeltaSa(O2) and DeltaDBP/DeltaSa(O2)), and heart rate (DeltaHR/DeltaSa(O2)) responses to progressive isocapnic hypoxia were measured before and after intermittent hypoxia. Resting ventilation, SBP, DBP, and HR did not change after intermittent hypoxia. DeltaSBP/DeltaSa(O2) and DeltaDBP/DeltaSa(O2) increased significantly after intermittent hypoxia accompanied by an enhanced DeltaV(I)/DeltaSa(C2), but there was no change in DeltaHR/DeltaSa(C2). There were significant correlations between the change in DeltaV(I)/DeltaSa(O2) and both the changes in DeltaSBP/DeltaSa(O2) and DeltaDBP/DeltaSa(O2) following intermittent hypoxic exposure. These results suggest that short-term intermittent hypoxia leads to the enhanced arterial BP response to hypoxic stimuli in humans, and that the enhanced peripheral chemosensitivity to hypoxia after intermittent hypoxia may play an important role in the increased arterial BP response.