[Continuous measurement of cardiac output during ergometer exercise using an ultrasonic pulsed Doppler flowmeter]

A method for determining cardiac output was developed, which provided the product of the absolute blood flow rate at the aortic arch (as measured non-invasively from the suprasternal notch by an ultrasonic pulsed Doppler flowmeter: UPDF) and the cross-sectional area of the aorta at that level, as estimated from two-dimensional echograms. Using this method, non-invasive continuous measurements of cardiac output were made during bicycle ergometer exercise. The results were summarized as follows: Resting cardiac output values obtained by this method correlated reasonably well with those by the thermodilution method (correlation coefficient r = 0.76). Eight healthy male volunteers exercised for 2 min on a bicycle ergometer at 250 kpm/min, and serial cardiac outputs were determined by this method for five of these subjects during and after the loading. The cardiac output curves thus obtained clearly demonstrated abrupt increases in cardiac outputs initially, followed by rapid returns to resting cardiac output levels after the end of exercise. We intend to conduct additional studies for larger groups of subjects to further evaluate and to establish this method for use in cardiac examinations.