Determination of the true phase velocity of arterial pressure waves in vivo.

Results of simultaneously recorded pressure, diameter, flow, and differential pressure from an arterial segment were studied by Fourier analysis. The method was applied to pressure propagation in the femoral artery of anesthetized dogs. Experimental values of phase velocity compared favorably with values predicted from a theoretical wave propagation model. The phase velocity was generally constant for frequencies over 35 rad/sec. At frequencies below 20 rad/sec, it decreased rapidly with decreasing frequency. The frequency variations of the true and apparent phase velocities were significantly different. The characteristic impedance of the femoral artery was a weak function of frequency and nearly independent of the mean arterial pressure. High frequency values of the local fluid impedance above 50 rad/sec were significantly lower than those of the characteristic impedance. It was concluded that the method can be used to obtain reliable values of phase velocity in the physiological frequency range from in vivo measurements.