Cyclic variation of the Doppler power from porcine blood under pulsatile flow in tubes of varying compliance

Abstract

The cyclic variation of the Doppler power backscattered from porcine whole blood and red blood cell suspensions was investigated under pulsatile flow in a mock flow loop of varying compliance. Experiments were performed using five different hematocrit values at four different stroke rates. A significant cyclic variation of Doppler power was measured in all experiments but the pattern of the cyclic variation was different. At high stroke rates (40 beats/min or more), the cyclic variation of the Doppler power showed a small peak during acceleration of flow and reached a minimum at peak systole and another peak was observed during deceleration. This minimum power phenomenon during peak systole became more prominent as the stroke rate was increased up to 60 beats/min. At a low stroke rate (20 beats/min), the Doppler power increased during early systole and remained the same until late diastole. The cyclic variation using whole porcine blood and red cell suspension showed the same pattern and suggested that aggregation of RBC did not affect the pattern of the cyclic variation. In addition to these general features, the differences for different experimental scenarios (whole blood versus red cell suspensions, and rigid tube versus compliant tube) are discussed.