Cardiac Control Models

Abstract

The dynamic properties and phase locking phenomena of a nonlinear model of human cardio-respiratory control loops, cardioventilatory coupling (CVC) and respiratory sinus arrhythmia (RSA) are investigated in this thesis. Models of CVC and RSA are achieved by using a coupled circle maps. It is evident that CVC and RSA can both cause phase locking between heartbeats and breathing. Using an analytic function to describe the experimentally defined baroreceptor response curve in a model of RSA, it is shown that a linearised version of the model approximates the dynamic properties of the full model. The baroreflex model reveals that an increase in sympathetic time-delay and heightened sensitivity of the total peripheral resistance both generate sustained blood pressure oscillations, consistent with the Mayer and Traube-Hering waves observed in clinical studies. Arnold's tongues generated by discrete and continuous models of RSA are compared, and possible connections between classes of models are discussed.