A model of arterial pulse propagation and reflection

The arterial tree is depicted as a single transmission line of tapered characteristic impedance with a nonlinear load. This load contains a Zener diode to simulate the ´Waterfall´ behaviour caused by smooth muscle tension around the resistance vessels. A shunt resistor represents arterio-venous shunts. The waterfall reference pressure is related to the peripheral blood flow by a feedback coefficient with a time-constant. This combination provides realistic aortic pressure and flow waveforms and an aortic input impedance similar to a ´Windkessel´ model. To demonstrate low-frequency responses, the amplitude of the input signal is modulated by a binary, pseudo-random noise waveform, synchronised to the pulse and 63 pulse periods long.