A Digital Simulation Of The Human Cardiovascular System*

This paper shows how a model of the human cardiovascular system was developed on a digital computer and how this model was used to test some important theories of cardiovascular physiology. An algorithm for the rapid numerical solution of non-linear ordinary differential equations is introduced and applied to the state differential equation of the hydraulic system model. A brief account of the physiological reflexes that control blood pressure, as studied by animal experimentation, is given and shown to suggest the particular hydraulic parameters which are controlled in each refiex, as well as the approximate dynamics of these reflexes. The digital implementation of the reflexes are then outlined and their effect when used to control parameters of the hydraulic system model is studied.Next, it is demonstrated how experimentation in the form of computer simulation trials can be utilized to characterize the above reflexes more accurately so that certain key experimental phenomena observed in the human may be reproduced in the model. These phenomena are indicative of a highly non-linear control system and may be reproduced in the model if “on–off” control of simulated peripheral resistance and venomotor tone is implemented. Thus, it is illustrated how a computer model may be used to assess the nature of a biological control system and even specify important elements in this system.