Microcomputer control of canine heart rate through chronotropic drug infusion

Cardiovascular changes principally take two forms: (a) inotropic or pressure-related changes, and (b) chronotropic or rate-related changes. Although the two are not mutually exclusive in the biofeedback of a normally functioning animal, this work was concerned principally with affecting the heart rate of a dog by infusing a rate-altering drug. The purpose of this project was to design an external heart-rate control system which consisted of a dog, an infusion pump containing a chronotropic drug and an infusion-pump/heart-rate controller. Input to the system was a target heart rate. The feedback element and the system output was the dog's actual heart rate, ideally being driven to that target heart rate by the controller. A microcomputer-based system was used with proportional derivative control to accommodate the inherent plant delay. Through the use of an inline solid-state relay, on/off control was chosen because of (i) the capability to use any type of infusion pump, and (ii) the simplicity of design due to slow animal response. The experimental results have demonstrated success at overriding the dog's own biological feedback network and driving its heart rate to some artificially chosen target.