Session PB6.4

Evaluation of Blood Pulse Wave Velocity and Arterial Relaxation Time Constant

WC Hu*, JJ Wang, LY Shyu, HM Cheng,
CH Chen, YT Shih, YJ Sun

Chung Yaun Christian University
Chung Li, Taiwan

Based on circuit theorem, arterial pressure wave function could be described and quantified using Windkessels model. The derivation of model that was proposed using periodic function to describe pulsatile hemodynamics in artery was commonly accepted. The decay waveform in Windkessels model was the characteristic arterial impedance of the model, if the decay function of pressure wave was modeled as aortic valve closed. It is similar to the impedance function of capacitor discharge in the Windkessels model. And, the time constant of the decay waveform is the feature of arterial system by the definition of Windkessels model. On the other hand, there was a transmission line theory that assumed the finite pulse wave velocity in the artery. The spatial and temporal pressure gradients in arterial system were recognized as the feature of compliance in the artery. That was utilizing the propagation models of delay and wave reflection in blood pressure that derived the pulse wave velocity (PWV) into indexing the pathological and physiological condition of arterial system. The higher the value of PWV is indicating the severer of the arteriosclerosis. However, the relationship of the relaxation time constant of Windkessels model and PWV was not described. We have collected data to correlate the pulse wave velocity to the relaxation constant. The blood pressure waveform from 12 patients using oscillometric method and invasive pressure waveform of 14 patients at aortic root were acquired. Their pulse wave velocities were acquired at same the sitting. The mean and standard deviation of the pulse wave velocity was 1595.63±301.56 cm/sec. The mean and standard deviation of the relaxation constant of the brachial arterial BP was -0.8±0.13 and at aortic root was -0.85±0.14. The correlations of the relaxation constants at brachial artery and aortic root to the pulse wave velocity are 0.87. The result showed that the higher the pulse wave velocity the smaller the relaxation constant. The faster the pulse wave velocity is associated with longer decay time.

(Abstract Control Number: 177)