Peaking of the pressure pulse in fluid-filled tubes of spatially varying compliance.

Calculations are made for a fluid-filled tube with characteristics approximately those found physiologically. The pressure variation, diameter, and compliance at the input end are as measured by Lawton for the abdominal aorta of a dog. After a 30 cm-long input section of constant k (=dp/dA), the tube is taken to stiffen by approximately the amount measured by Patel et al., i.e., k increases by a factor of 5 over the next 40 cm. The cross-section remains constant. Pressure and velocity wave forms are calculated at 8 stations spaced at 10-cm intervals down the tube. The pressure pulse leading edge is found to become steeper in the stiffening section. The peak height of the pressure pulse is found to increase by about 50% and the velocity pulse to decrease by about 30% as the disturbance propagates over a distance of 70 cm. These values agree qualitatively with the experimental physiological values given by McDonald. Most of the pressure peaking takes place upstream of the stiffening section.