Determination of cardiac output from pulse pressure contour during intra-aortic balloon pumping.

The reliability of cardiac output determinations from radial pulse pressure contour during intra-aortic balloon pumping (IABP) has been tested and compared with thermodilution measurements. During IABP the pulse pressure curve is distorted by preset volume changes in the aorta. The pressure decrease following balloon deflation was compared with pressure increase following systolic ejection to determine stroke volume and cardiac output. The analysis and calculations were computerized. Measurements were made in thirteen patients with left ventricular failure. The algorithmic analyser failed to produce any results at all in two patients and in ten other patients if failed to produce results more often in some of the patients than others. This made the algorithmic calculation of cardiac output useless in the care of the individual patients. In thirteen patients on IABP seventy-seven comparisons were obtained, and a fair covariation (r = 0.86) was found. The ratio between the two methods of cardiac output measurements did not change significantly with increasing cardiac output.