Abstract
According to Windkessel theory, diastolic pressure waveform is a function of the total peripheral resistance and the compliance of the artery. Higher compliance makes the decrescence gentler, and the waveform would be further different from the input pressure waveform made by the cardiac contraction. Frequency analysis of the arterial pressure waveform shows fundamental frequency (F) derived from the heart rate and harmonic frequency which is the integral multiple of the F. In the present study, we measured abdominal aortic pressure, abdominal aortic flow, and the diameter during infusion of Nitroprusside with the speed of 1, 0.6, 0.3 μg/kg/h. The compliance was calculated from the pulse pressure and volume change calculated by the diameter and the length of the aorta. The compliance was also calculated with first order of the Windkessel theory. High frequency centroid (HFC), which is amplitude-weighted mean frequency of the third to seventh peaks of the harmonic waveform was analyzed. HFC was normalized by F. Total harmonic distortion (THD), which is an index of distortion from a pure sine wave was also analyzed. Measured compliance and the calculated compliance of the aorta were significantly correlated. Normalized HFC and both measured compliance and the calculated compliance also showed significant linear correlation. THD did not show significant correlation between the compliance. These results suggest HFC can be an index of the compliance or the aorta, and the compliance may be analyzed from the aortic pressure waveform only. [J Physiol Sci. 2006;56 Suppl:S133]
