Cardiac output in normal resting man

¹ Cardiovascular Pulmonary Laboratory, Department of Medicine, University of Colorado Medical Center, Denver, Colorado

Sixty-three measurements of cardiac output in 50 normal resting individuals utilizing pulmonary arterial catheterization and the classical Fick method were made to investigate the normal standards of cardiac output under these conditions. Variation between individuals in age, sex, body size and metabolic rate was great enough to render the cardiac index (cardiac output/ unit of body surface area) a rather insensitive standard of normal blood flow. Rather the variation was substantially improved by considering cardiac output to be linearly related to oxygen uptake. This direct relationship appeared to be the result of the A-V oxygen difference varying independently of oxygen uptake, metabolic rate and body surface area. The mean A-V oxygen difference was 39.8 cc/l. with one standard deviation of ±5.8 cc/l.