Abstract
Periodic function can be displayed as summation of sinusoids using Fourier series. In the present study, arterial pressure waveforms during infusion of vasoactive agents were analyzed with Fourier series. Abdominal aortic pressure, abdominal aortic flow in adult anesthetized rats during infusion of Angiotensin II (ANG), Phenylephrine (PHE), Nitroprusside (NP), and Nitroglycerine (NG) were measured. Peripheral vascular resistance (R) was calculated with the pressure and the flow. The pressure waveforms were analyzed with the Fourier series. Harmonic distortion (HD) and mean frequency were calculated from the amplitudes and the frequencies derived by the series. Mean frequency was normalized with the fundamental frequency, which corresponds to pulse rate per second. As results, change in R was inversely proportion to change in HD, and change in normalized mean frequency (NMF). Increase in R with vasopressor i.e., ANG and PHE infusion lowerd the HD and the NMF. Decrease in R with vasodilator i.e., NG and NP infusion made the HD and the NMF larger than those during control. That means the waveform of the arterial pressure during vasopressor infusion is getting similar to the sinusoid of the fundamental frequency, but the waveform is complicated during vasodilator infusion. Thus, changes in HDR and NMF are possibly used as indices of changes in R, but further study is needed to clarify the reason of changes in the waveform. [J Physiol Sci. 2007;57 Suppl:S196]
