Time-variant parametric model for the 24-H evaluation of the closed-loop α-baroreceptive gain

Spectral analysis of RR scries. obtained from ECG. and systolic arterial pressure (SAP) series. obtained from continuous recording of pressure signal. is now a well established tool for the quantification of Autonomic Nervous System status in controlling the cardiovascular parameters. In particular bivariate parametric models are able to describe mutual relationships between RR and SAP signals, and to calculate the a-baroreceptive gain evaluating how oscillations in pressure systolic values can affect oscillation in heart rate. in the frequency bands in which the signals present high coherence values (LF and HF bands). In this paper continuous extraction of tx-gain is obtained by making the bivariate model time-variant and able to follow and describe transient phenomena. The bivariate model is updated recursively according to the dynamic variations of the signals. The algorithm is employed for the beat-to-beat evaluation of a-parameter during 24-hour recording, and the determination of the circadian modifications of the spectral parameters is analyzed with beat-to-beat discretization.