An improved method for the determination of the pulse transmission characteristics of arteries in vivo.

Abstract

Based on the wave transmission line theory, a method to determine the arterial complex propagation coefficient from the Fourier components of natural pressure pulses is described. The coefficient is composed of the damping constant (.alpha.) and the phase constant (.beta.). In the arterial system, forward- and backward-traveling waves are superimposed. In the new procedure, 2 pressure recordings are needed. The relationship between forward and backward waves is defined by occluding the artery directly behind the distal measuring point so that total positive reflection occurs. The method was applied in the common carotid arteries of 9 dogs. The arterial diameter is recorded by a photoelectric device and the characteristic impedance (Z) is determined. For the frequency range of 1.25-12 Hz, .alpha. increased from 0.003 to 0.01 Neper/cm, and .beta. from 0.02 to 0.1 radian/cm. The phase velocity was 9-11 m/s. The Z modulus was between 7000 and 12,000 CGS [cmgs] units and dropped slightly with increasing frequency. The results and the accuracy of the various methods are compared.