IMPEDANCE AND WAVE REFLECTION IN ARTERIAL SYSTEM - SIMULATION WITH GEOMETRICALLY TAPERED T-TUBES

The aortic input impedance is simulated by an asymmetric T-tube model loaded with complex loads. A geometric tapering is incorporated to rep resent the vasculature, assuming a triangular distribution of the wave transmission paths. Parametric analyses using physiological data demo nstrate that the predicted impedance and reflection coefficient spectr um (RCS) closely mimic the experimental data. The simulation also reve als several significant features. As diameter tapering can minimise th e presence and influence of wave reflections, the impedance modulus st ays relatively constant with two distinct minima. The frequency of fir st minimum of impedance modulus is evidence of the tube elasticity and load compliance in the lower extremity, and the frequency of second m inimum is evidence of those in the upper extremity. The high-frequency portion of the impedance modulus is affected by the tube elasticity, but not by the load compliance. The impedance spectrum at higher frequ encies shows no notable fluctuations corresponding to a decrease in bl ood or wall viscosity. Furthermore, the low-frequency range in RCS is dominated by the longer lower body tube, and the high-frequency range by the shorter upper body tube. This geometrically tapered T-tube is c onsidered a more natural model for the description of the systemic art erial system.