Spectral Analysis of Arterial Blood Pressure in the Rat

In the present study, a low-compliance passive pressure transducer and a microprocessor-based data acquisition system were used to obtain recordings of time-varying blood pressure in the femoral arteries of anesthesized rats. Discrete spectral analysis techniques were used to analyze the pressure-time records and to quantify the contributions to the arterial pressure profile of frequencies in the band from 0 to 128 Hz. In accordance with previous studies in other species, most of the energy in the spectra obtained was concentrated in narrow bands corresponding to harmonics of the cardiac and respiratory cycles. The spectra also provided evidence consistent with either an autoregressive component or an ultra-low-frequency blood pressure rhythm of unidentified origin, but did not indicate the presence of either Traube-Hering or splenic "waves" in the arterial system of the rat.