A new approach to the noninvasive measurement of cardiac output using an annular array Doppler technique--II. Practical implementation and results.

An experimental Doppler flowmeter system has been developed which can noninvasively measure blood flow volume rate in a vessel. It is based on the attenuation compensated technique and does not require knowledge of the vessel size or beam-vessel angle. In vitro results have shown that the measurement of volume flow rate is independent of vessel angle to within +/- 4%, and independent of vessel diameter to within +/- 5%. Flow rate linearity is better than +/- 3%. A good comparison has been obtained, in vivo, of aortic diameters measured by an imaging system and with this flowmeter; the r value was 0.98. The noninvasive measurement of cardiac output using this flowmeter has been compared with conventional dilution techniques in 54 patients, with a resulting correlation coefficient of r = 0.96.