Date of Award

Fall 1968

Degree Type

Thesis - Restricted

Degree Name

Master of Science (MS)

Department

Biomedical Engineering

First Advisor

Horgan, James D.

Second Advisor

Lade, R. W.

Third Advisor

Lange, Ramon L.

Abstract

The cardiovascular system provides man with a means of transport so that nutrient and oxygen may be supplied to and waste products removed from all of his cells. Man has long studied and attempted to understand the complex blood pressure and blood flow in this system and to relate them to measurable mechanical events and parameters such as heart muscle contraction, heart valve closure or the resistance to flow of arteries and veins. Blood flow in the circulatory system is closely regulated by a variety of autoregulatory and autonomic nervous control mechanisms. The tissues autoregulate flow by adjusting muscle tone at the origin of the capillaries to allow or constrict flow as their oxygen or nutrient needs vary. Heterometric autoregulation causes the ventricles to contract with increased force when the heart muscle becomes stretched while holding larger quantities of blood than usual. Homeometric autoregulation increases the strength of cardiac contraction without requiring an increase in muscle fiber length during increased heart work load. The sympathetic and parasympathetic nervous systems provide neural control of the rate and the strength of contraction of the heart muscle, and control of resistance of the arterioles, small arteries, venules and small veins. Pressoreoeptors in arterial walls provide pressure information to the autonomic nervous system. No model of the circulatory system has ever attempted to include all of these control mechanisms. This thesis will study the effect of malfunctions to the system in the form of stenotic and insufficient heart valves using a model which contains no autoregulatory or neural control loops. Such simulations can not hope to duplicate the complex, integrated response of the cardiovascular system, but the "open loop" response may provide insight into the amount and type of "closed loop" control required for each type of simulation.

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