Control of a mock circulatory system to simulate the short-term baroreflex

A mock circulatory system (MCS) integrated with the baroreceptor reflex, a neurological function that regulates the mean systemic arterial pressure (P
sa
) by adjusting heart rate, ventricular contractility, and systemic resistance through negative feedback, was developed to simulate the key hemodynamic variables in response to various physiological load changes. The MCS consists of two compliance chambers representing the left atrium and systemic artery, a proportional valve as a variable resistor mimicking the systemic vascular resistance (SVR), and a centrifugal pump as a current source simulating the pumping mechanism of the heart. The model of the baroreceptor reflex was implemented in software to generate the reference signals of the cardiac output (CO) and SVR. These two reference signals along with the models of the centrifugal pump and the proportional valve were used to control the rotational speed of the pump and the gap of the valve such that the desired CO and SVR can be reached. Performance of the MCS was tested under different cardiovascular demand levels from resting to heavy exercise. The test results show that this simple MCS was able to simulate the response of key hemodynamic variables comparable to the same variables produced by a complex model from a computer simulation. The MCS performed well in simulating the hemodynamic variables under resting and mild exercise conditions. This novel MCS implementation provides a much more physiological meaningful tool comparing with existing MCS. It is a valuable asset for studying the physiology of the circulation, for heart assist devices testing, and for bioengineering education.