In Vitro Development of Automatic Control for the Actively Filled Electrohydraulic Heart

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Abstract
The in vitro development of automatic control of the actively filled, alternately pumped, volumetrically coupled, electrohydraulic total artificial heart was the goal of this investigation. Control features under study were (a) cardiac output (CO) response to preload; (b) CO relationship to mean arotic pressure (AoP); and (c) control of balanced ventricular outputs. A modified pulmonic valve to increase backflow was used as a balancing mechanism. Hydraulic fluid pressure transudcers monitored diastolic pressures, and microprocesor control of motor speed maintained a mild suction to yield fillng rate dependent on atrial pressure. Results indicated a rise in CO from 5 to 9 L/min, with a change in mean right atrial pressure (RAP) from 0 to 7 mm Hg. No significant difference in CO was found as AoP was varied from 80 to 120 mm Hg with a maximum variation of .+-.0.5 L/min on CO and .+-.1 mm Hg on RAP. Balance was maintained for bronchial flows up to 5% with mean left atrial pressure never exceeding 15 mm Hg. An alternately pumped electrohydraulic heart was automatically controlled to respond sensitively to preload changes. Afterload changes did not alter the CO response curve. Automatically controlled, balanced ventricular outputs were maintained.