The effect of acute hypoxia on left ventricular function during exercise

The effect of acute hypoxia on the human left ventricular function during exercise was evaluated by 2D and Doppler echocardiography on 11 healthy male college students. Each subject completed 6-min moderate intensity (100 W) supine cycling exercises in normoxia and hypoxia, respectively. The concentration of inspired O₂ was adjusted to keep arterial hemoglobin O₂ concentration (SpO₂) at 88–92% during hypoxia. Doppler indices obtained were compared between normoxia and hypoxia. The left ventricular myocardial diastolic function was increased during exercise in hypoxia compared with normoxia. The peak velocity of early filling wave increased at rest (P < 0.05) and during exercise (P < 0.05 at second minute, and P < 0.01 at sixth minute) in hypoxia. The heart rate (P < 0.01) and cardiac output (P < 0.001) were elevated markedly at rest during hypoxia. The left ventricular systolic function variables, such as stroke volume, ejection fraction, and end-systolic volume were relatively unaltered during hypoxia compared with normoxia. The results suggest that acute hypoxia increases the left ventricular myocardial diastolic function during moderate intensity supine cycling exercise without affecting the systolic function.