Waveforms in the arterial tree

System identification techniques were employed to characterize the dynamics in the arterial system. Arterial pressure and flow waveforms were obtained from computer simulations using a complex model and from experiments in domestic swine. Transfer functions were identified by using an iterative least-squares approach. It was shown that the aortic input impedance can be sufficiently characterized by a 1st-order system and the transfer function between aorta and femoral artery is dominated by a 2nd-order system. Within a scale factor the estimated aortic flow waveform matched well with the measured (less than 1% error). Thus, the proposed method provides for the cycle-by-cycle determination of flow waveform from aortic root pressure and should be useful for studying circulatory dynamics and regulatory control mechanisms