Prediction of arterial input impedance spectrum by an asymmetric t-tube model terminated with an opportune complex load
Journal
Journal of the Chinese Institute of Engineers, Transactions of the Chinese Institute of Engineers,Series A/Chung-kuo Kung Ch'eng Hsuch K'an
Journal Volume
15
Journal Issue
5
Pages
533-547
Date Issued
1992
Author(s)
Abstract
Abstract Arterial impedance is determined by physical properties of blood and vessel walls. Such factors include the blood viscosity and density, the wall viscoelasticity, and the vessel diameter. To account for wave transmission and reflection properties in arterial systems, an asymmetric T‐tube model, which consists of two uniform, viscoelastic tubes of different lengths representing the upper and lower extremities, is provided to simulate the arterial impedance spectrum. Each terminal complex load is a revised windkessel with compliance as well as resistance and inductance. Using representative data from the literature, parametric analysis shows that when peripheral compliances are increased, small moduli in the low frequency portions of the impedance spectra are produced, whereas alterations of either the characteristic impedances or inductances of the terminations have little effect on input impedance. The result of small moduli in the low frequency portions of the impedance spectrum associated with increasing peripheral compliances is quite different from that of the model of Liu et al. In animal studies and in theoretical considerations, there is evidence that the impedance spectrum predicted by our model can more closely mimic the impedance spectrum of the arterial system than that of Liu's model. Alteration of peripheral resistance only affects the impedance modulus at its dc term. Change in the elasticity or effective lengths of the tubes results in shifts in the positions of the maxima and minima similar to those observed experimentally. Alteration of the viscosity of the vessel walls or of the blood affects the fluctuations of the impedance spectra without affecting the positions of the maxima and minima. Thus, this simple model associated with transmission line theory provides more insight into the individual influence of various parameters of the proximal and peripheral vasculature on central hemodynamics.
Type
journal article