Reference Values for Peak Exercise Cardiac Output in Healthy Individuals

BACKGROUND: Cardiac output (Q\u2d9) is a key parameter in the assessment of cardiac function, its measurement being crucial for the diagnosis, treatment, and prognostic evaluation of all heart diseases. Until recently, Q\u2d9 determination at peak exercise has been possible through invasive methods, so that normal values were obtained in studies based on small populations. METHODS: Nowadays, peak Q\u2d9 can be measured noninvasively by means of the inert gas rebreathing (IGR) technique. The present study was undertaken to provide reference values for peak Q\u2d9 in the normal general population and to obtain a formula able to estimate peak exercise Q\u2d9 from measured peak oxygen uptake (V\u2d9o2). RESULTS: We studied 500 normal subjects (age, 44.9 \ub1 1.5 years; range, 18-77 years; 260 men, 240 women) who underwent a maximal cardiopulmonary exercise test with peak Q\u2d9 measurement by IGR. In the overall study sample, peak Q\u2d9 was 13.2 \ub1 3.5 L/min (men, 15.3 \ub1 3.3 L/min; women, 11.0 \ub1 2.0 L/min; P < .001) and peak V\u2d9o2 was 95% \ub1 18% of the maximum predicted value (men, 95% \ub1 19%; women, 95% \ub1 18%). Peak V\u2d9o2 and peak Q\u2d9 progressively decreased with age (R2, 0.082; P < .001; and R2, 0.144; P < .001, respectively). The V\u2d9o2-derived formula to measure Q\u2d9 at peak exercise was (4.4 7 peak V\u2d9o2) + 4.3 in the overall study cohort, (4.3 7 peak V\u2d9o2) + 4.5 in men, and (4.9 7 peak V\u2d9o2) + 3.6 in women. CONCLUSIONS: The simultaneous measurement of Q\u2d9 and V\u2d9o2 at peak exercise in a large sample of healthy subjects provided an equation to predict peak Q\u2d9 from peak V\u2d9o2 values