Continuous cardiac output measurements with a newly developed pulmonary artery Doppler catheter.

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Development of a method for continuous cardiac output measurements has been under way over a decade. Although intravascular ultrasound techniques have been used for measuring cardiac output continuously, a problem would be the angle of incidence between the ultrasound beam and the blood flow, which would constitute the errors in velocity measurements and in cardiac output measurements. We newly developed pulmonary artery Doppler catheter which could provide true flow velocity independent of the angle of incidence formed by the ultrasound beam and the flow.A pair of ultrasonic transducers positioned at a fixed angle was mounted on the distal section of pulmonary artery catheter to be positioned in the main pulmonary artery. The Doppler shifts (DELTAf1, DELTAF2) were detected by two transducers sampling at closely spaced two points in the main pulmonary artery. The values of DELTAF1 and DELTAf2 were used to compute two velocity measurements, and true flow velocity of pulmonary artery was … More calculated using following equation : V= ((V1)^2+(V2)^2)^<1/2>, where V=true velocity, V1 and V2=velocity detected by the transducer 1 and 2. The velocities were calculated using newly developed phase differential techniques. Cardiac output by thermodilution technique and true flow velocity of pulmonary artery were measured simultaniously. Then, cardiac output was calculated from true flow velocity of pulmonary artery continuously. After IRB approval, the pulmonary artery Doppler catheter (Aloka, Tokyo, Japan) was evaluated in animal experiments. The Doppler catheter was advanced to the pulmonary artery of anesthetized dogs (19-30kg). After thoracotomy, an electromagnetic flow probe was placed around the pulmonary artery. Cardiac output was measured by the pulmonary artery Doppler catheter (CO-Doppler), by thermodilution method (CO-Thermo) and by electromagnetic flowmeter (CO-EMF) simultaneously, and CO-Doppler, Co-Thermo and CO-EMF were compared.Co-Doppler was highly correlated with CO-EMF (Y=1.16x-0.27, r^2=0.99, n=71, p<0.001). CO-Doppler was also correlated with CO-Thermo (r^2=0.72).Using a newly developed pulmonary artery Doppler catheter, we are able to estimates cardiac output continuously. Our technique presented would be superior in measuring cardiac output at real time basis than other modified thermodilution techniques for continuous cardiac output monitoring. Less