On-line cardiac output by digital computer

output by digital computer. J. Appl. Physiol. 40(2): 266-268. 1976 *- Many devices for fast cardiac output calculations employ special assumptions and departures from the Stewart-Hamilton method. These assumptions and departures can cause substantial errors. This publication describes an on-line computer system for evaluating dye-dilution curves according to the classical Stewart-Hamilton method. Dilution curves are smoothed, using a digital filter to eliminate heartbeat noise. Recirculation is removed using the constant ratio property of exponentials. The quality of the curves is evaluated by deter-mining the length of the base line, the extent and the fit to an exponential downslope, and a figure of merit, based on the five tanks-in-series model. Dilution curves, the logarithmic form, and the exponential ratios are displayed on a CRT for visual checks. Comparison of cardiac outputs obtained by this on-lin