Influence of Posture on Cardiac Output and Minute Ventilation During Exercise

Abstract

In four normal subjects, cardiac output, oxygen uptake, and ventilatory volume were compared on 8 occasions at rest and on 20 occasions during exercise in the recumbent and sitting postures. The oxygen uptake was not significantly different in the two postures either at rest or at equal external work loads. In the sitting posture during exercise, the cardiac index was approximately 12 per cent and stroke index 19 per cent lower than in the supine posture. Ventilation was signifi cantly higher because of an increase in respir atory frequency.