EFFECT OF POSTURE AND PROLONGED REST ON THE CARDIAC OUTPUT AND RELATED FUNCTIONS

Abstract

A method based on the foreign gas principle for determination of the arteriovenous O difference (and cardiac output) has been descr. Its distinguishing feature is its termination within 10 sec. in order to avoid the error due to recirculation of appreciable amts. of blood, which has been demonstrated to occur at that time or promptly thereafter. The method, applied in 34 consecutive detns. in 6 normal young men, demonstrated a cardiac output 10-25% higher in the recumbent as compared to the sitting posture. In either position, although basal conditions may be attained in 1 hr. as indicated by the constancy of the rate of O consumption, the cardiac output progressively decreases as rest is prolonged for a 2d and 3d hr. These changes run parallel with the observed changes in pulse rate and pulse pressure, the latter following closely the systolic output.