Estimation of Cardiac Output From First Part of Arterial Dye-Dilution Curves

¹ From the Section of Physiology, Mayo Clinic and Mayo Foundation, Rochester, Minnesota

A formula for calculation of the cardiac output from indicator-dilution curves has been derived, utilizing only measurement of the buildup time and peak concentration of the curve. The application of this formula and of one described by Dow for determining cardiac output from the initial portion of a dilution curve has been tested in 63 curves recorded after central injection of dye in normal persons. Values for cardiac output determined by the forward-triangle and the Dow methods showed satisfactory agreement with values determined by the Hamilton replot method. Comparison of values from the three dye methods with values determined by the Fick method gave a larger degree of variability, but one that was similar for each of the dye methods. It is concluded that the variability between the dye and Fick methods is caused by factors other than the method used to calculate the output from the dilution curve.