Relationships between short-term blood-pressure fluctuations and heart-rate variability in resting subjects. II: A simple model.

Abstract

A simple model of the beat-to-beat properties of the cardiovascular system is used to interpret the results of spectral analysis of blood-pressure and interval data. The model consists of two equations, one representing the fast regulation of interval by the systolic pressure (baroreflex), the other one representing a Windkessel approximation of the systemic arterial system. The model, when applied to interval and blood-pressure data from resting subjects, explains the lack of respiratory variability in the diastolic pressure values. The baroreflex equation seems to describe the data only in the region of respiratory frequencies. The shape of the phase spectrum of systolic pressures against intervals is modelled by difference equations, but no physiological interpretation of these equations is given.