G. Cloutier et Kk. Shung, STUDY OF RED-CELL AGGREGATION IN PULSATILE FLOW FROM ULTRASONIC DOPPLER POWER MEASUREMENTS, Biorheology, 30(5-6), 1993, pp. 443-461
Human red cell aggregability and disaggregability represent important
hemorheological parameters of blood. Several techniques have been prop
osed to evaluate the tendency of red cells to form aggregates and to d
isrupt in the presence of shear stress. One of the most recent approac
hes is based on the characterization of the intensity of ultrasonic sc
attered signals. A pulsatile flow loop model is used in the present st
udy to demonstrate the potential applicability of Doppler ultrasound t
o detect and characterize the hemodynamic behavior of red cell aggrega
tes. Porcine whole blood specimens collected from 20 different pigs we
re circulated in the flow model (tube diameter of 0.476 cm) at differe
nt mean velocities and pulsation rates. At a pulsation of 70 beats/min
for mean velocities of 13 cm/sec and 63 cm/sec, no cyclic variation o
f the Doppler power was observed, suggesting the absence of rouleaux b
uild-up and rouleaux disruption. At a pulsation of 20 beats/min and me
an velocities of 11 cm/sec and 38 cm/sec, statistically significant cy
clic variations (p < 0.01) were measured. It is suggested that aggrega
te size enlargement, rouleaux orientation with the flow field and the
effect of shear stress on rouleaux disruption are possible causes for
the observed cyclic variation of the Doppler power within the flow cyc
le at a pulsation of 20 beats/min. A discussion of the potential appli
cation of this technique for in vivo study in large vessels is given.