Cardiovascular physiology: simulation of steady state and transient phenomena by using the equivalent electronic circuit.

By using commercially available software it is readily possible to design electronic circuits and to analyze them. By introducing the concept of equivalent quantities a simulation of various physiological phenomena is possible. This includes the steady state as well as various complex transient phenomena. This paper describes the use of an equivalent electronic circuit in simulating the cardiovascular system. It allows a stepwise upgrading. The first step is a one-ventricle circuit similar to the Starling heart-lung preparation. The final step is an equivalent circuit allowing simulation of various normal as well as pathological states (e.g. effects of heart rate, negative intrathoracic pressure, exercise, hemorrhage, heart failure, and hypertension). The degree of disturbance can be set by adjusting the value of single components. Following this, the optimal type of compensation (e.g. the increase in blood volume in failure of the right ventricle; systemic venoconstriction in failure of the left ventricle) of the basic disturbance can be searched for, activated and the consequences studied. The described approach has been found a useful tool in teaching physiology and pathophysiology for postgraduate medical students.