ASSESSMENT OF CARDIAC-OUTPUT FROM NONINVASIVE DETERMINATION OF ARTERIAL-PRESSURE PROFILE IN SUBJECTS AT REST

The stroke volume of the left ventricle (SV) was calculated from nonin vasive recordings of the arterial pressure using a finger photoplethys mograph and compared to the values obtained by pulsed Doppler echocard iography (PDE). A group of 19 healthy mpn and 12 women [means ages: 20 .8 (SD 1.6) and 22.2 (SD 1.6) years respectively] were studied at rest in the supine position. The ratio of the area below the ejection phas e of the arterial pressure wave (A(s)) to SV, as obtained by PDE, yiel ded a ''calibration factor'' dimensionally equal to the hydraulic impe dance of the system (Z(ao)=A(s).SV-1). The Z(ao) amounted on average t o 0.062 (SD 0.018) mmHg.s.cm(-3) for the men and to 0.104 (SD 0.024) m mHg.s.cm(-3) for the women. The Z(ao) was also estimated from the equa tion: Z(ao) = a (d + b.HR + c.PP + e.MAP)(-1), where HR was the heart rate, PP the pulse pressure, MAP the mean arterial pressure and the co efficients of the equation were obtained by an iterating statistical p ackage. The value of Z(ao) thus obtained allowed the calculation of SV from measurements derived from the photople thysmograph only. The mea n percentage error between the SV thus obtained and those experimental ly determined by PDE amounted to 14.8 and 15.6 for the men and the wom en, respectively. The error of the estimate was reduced to 12.3 and to 11.1, respectively, if the factor Z(ao), experimentally obtained from a given heart beat, was subsequently applied to other beats to obtain SV from the A(s) measurement in the same subject.