Journal of Ultrasound in Medicine, Vol 6, Issue 4 181-190, Copyright © 1987 by American Institute of Ultrasound in Medicine
Continuous measurement of pulmonary blood flow using a retractable pulsed Doppler probe
C. L. Lucas, G. W. Henry, B. A. Keagy, E. Criado, J. I. Ferreiro, B. Ha, M. D. Baudino and B. R. Wilcox
The feasibility of measuring pulmonary blood flow (PAQ) continuously using
a removable, extraluminal 20 MHz pulsed Doppler probe, which has been used
successfully to measure aortic blood flow, was assessed in seven
anesthetized mongrel dogs. Simultaneous recordings were made from the
Doppler probe (range-gated 5-6 mm from the anterior wall of the main
pulmonary artery) and an electromagnetic flow probe (encircling the aorta)
over cardiac outputs (CO) ranging from 0.2 to 5.5 L/min. Assuming a flat
velocity profile and a fixed cross-sectional area, PAQ was initially
calculated as the product of area and mean velocity. Regression analyses
(PAQ = a + b X CO) indicated good intraanimal linear correlations in six
animals (r greater than or equal to 0.84) and no correlation in one animal
(r = 0.003); however, PAQ was consistently higher than CO and interanimal
variability was marked, as suggested by large deviations in mean intercept
and slope values (a = 1.67 +/- 1.09 L/min and b = 0.70 +/- 0.33). Results
improved (r greater than or equal to 0.79 in all animals, a = 0.47 +/- 0.52
L/min, and b = 0.77 +/- 0.21) when the method to estimate PAQ was altered
to assume that the starting cross-sectional area was the area that would
make baseline PAQ and CO agree, and that the area during each subsequent CO
level changed as a function of pulmonary artery pressure and an estimate of
pulmonary artery compliance. Results of this study imply that it will be
more difficult to use this Doppler probe to monitor CO from the pulmonary
artery than it was from the aorta due to the elliptical, more compliant
pulmonary vessel walls and the irregular pulmonary artery velocity profile.
