Functional origin of reflected pressure waves in a multibranched model of the human arterial system.

The effects of wave travel and wave reflection were simulated in a mathematical model of the whole arterial tree consisting of 142 uniform transmission line segments. The arterial model was partitioned into three separate segments: upper limbs, trunk, and lower limbs. Aging was simulated by increasing average pulse wave velocities of these segments (10.9-12.9, 8.0-11.7, and 9.0-11.3 m/s for upper limbs, trunk, and lower limbs, respectively). Reflection coefficients at the terminal elements were altered to simulate vasodilation (0.0) and vasoconstriction (0.95). The impedance patterns and spatial distribution of pressure waveforms generated by the model simulating aging and vasoconstriction were similar to in vivo measurements by other investigators. Reflected pressure waves from each segment reached the ascending aorta and contributed differently to the late systolic peak on the aortic pressure wave. Aging does not alter the origin of these reflected pressure waves in the trunk. Aortic impedance and pressure wave changes induced by simulation of dilation of splanchnic bed were similar to those observed experimentally with nitroglycerin.