Simulation of hemodynamics and regulatory mechanisms in the cardiovascular system based on a nonlinear and time-varying model

Abstract

Software is developed to simulate pressure- flow relationships and regulatory mecha nisms in the cardiovascular system. The core of the software is a set of state equations that characterizes the cardiovascular dynamics based on an analog electrical model. The state is propagated forward in time by numerical integration with a time step of 1 ms. Nonlinear and time-varying elements are treated in the simulation by updating the state equations every 5 ms. Hemodynamic waveforms from each cardiac cycle are averaged and used as input to several models of circulatory regulation. The regulatory mechanisms under investigation include the systemic autoregulation, the carotid baroreflex, and the effect of intramyocardial accumulation of calcium ions on left ventricular contractility. It is shown that the simulation accurately represents several observations of the cardiovascular dynamics and physiology. The software should be valuable for develop ing hypotheses and protocols of in vivo studies, for integrating and interpreting experimental results, and as a tool of computer aided instruction.