Possibility of cardiac output monitoring from the intra-arterial blood pressure profile

A method for estimating cardiac output (CO) from the intra-arterial blood pressure profile ("contour method") was tested in 8 patients: 6 with essential hypertension, 1 with a pheochromocytoma and 1 with orthostatic hypotension. CO (1/min) was derived by the following formula: PSA (1+St/Dt) X HR 10(-3), where PSA is the area under the systolic portion of the pressure curve, St is the systolic and Dt the diastolic time, X is a correction factor, HR is the heart rate and 10(-3) is a conversion factor from ml/min to 1/min. The "contour method" was compared to the thermodilution CO method. The correlation between the 2 methods was highly significant: the r value in all patients during different conditions (supine, tilt, dynamic and static exercise) ranged from 0.91 to 0.97 with an intercept close to 0 and a slope close to 1. These results indicate that CO is properly measured from the intra-arterial blood pressure profile by the "contour method". A continuous hemodynamic monitoring can be derived applying the "contour method" to the intra-arterial blood pressure profile obtained with the Oxford technique.