Blood pressure control and correlation dimension

A simple continuous nonlinear model of the human cardiovascular system (CVS) is investigated while focusing on the simulated achieved blood pressure (BP) signal. The beat-to-beat version of this model, introduced by DeBoer et. al. was a simplified linearized version. We present a modified model, which allows investigating the nonlinear dynamics of the CVS and the effect of variations in several physiological parameters on the correlation dimension, D₂. The simulation reveals nonlinear features such as bifurcation, due to variations in the α-sympathetic gain and the respiratory term. In addition, we studied the limitations of calculating D₂ in the presence of noise. The D₂ values obtained from the simulated BP signals are similar to values obtained in our previous experimental animal studies. Our results emphasize that nonlinearity in cardiovascular control is indeed a fundamental feature of the system.