Journal of Applied Physiology, Vol 63, Issue 3 1284-1288, Copyright © 1987 by American Physiological Society
Automated computation of relative flow resistance using a pulsed Doppler flowmeter
H. D. Battarbee, W. Johnson and G. E. Farrar
Department of Physiology and Biophysics, Louisiana State University Medical Center, School of Medicine in Shreveport 71130.
Use of a pulsed Doppler flowmeter to assess changes in blood flow
resistance often requires a laborious series of calculations, and full
characterization of resistance changes frequently necessitates replotting
of calculated data. To facilitate the interpretation of pulsed Doppler
flowmetry data, a simple, inexpensive device was constructed that computes
the signal ratio of mean arterial pressure (MAP) to directional pulsed
Doppler outputs. With this device, relative flow resistance can be recorded
and quantitatively assessed at a glance in three vascular beds in real
time. This computer-like device was designed around the Burr-Brown DIV100HP
integrated circuit. C741G OpAmps provide input buffering, zeroing, and
ranging adjustments enabling the user to accurately follow resistance over
a very broad range of changes without exceeding the device's operating
limits. A LM339 quad comparator monitors the input of each DIV100 and
indicates when operating limits are exceeded via a channel-specific LED
indicator and an audible alarm. No significant attenuation of the input
signals occurs over the range of direct current to 50 kHz, and the output
is without significant phase shift. Comparisons with calculated changes in
resistance derived from the MAP and pulsed Doppler flowmetry in
unanesthetized, unrestrained rats confirmed that resistance changes can be
measured with precision and accuracy.
