Predictive control by physical activity rate of a total artificial heart during exercise

No control method has yet been established for the total artificial heart (TAH) during exercise. As the simple intrinsic control method does not significantly increase cardiac output (CO), this study attempted to develop a new TAH control method that increases the CO during exercise in a manner similar to a natural heart (NH) by predicting changes in CO as a time function (TF) at various treadmill speeds. The control method for TAH was as follows: 1) an arbitrary grade of treadmill exercise was loaded onto the TAH goat; 2) a TF at this grade of treadmill exercise was determined from the physical activity rate (PAR) measurement, defined as the time average of the increase in vertical acceleration of the body; 3) operating parameters of both pumps were controlled in accordance with the TF using the computer algorithm. With the predictive control method changes in CO in the TAH were almost the same as in the NH, whereas no increase in CO occurred with the fixed control method (FC), in which operating parameters remained unchanged during exercise. Changes in blood lactate and catecholamines tended to be less than with the FC.