Development of a wearable pneumatic total artificial heart system aimed at permanent use

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A wearable pneumatic total artificial heart (PTAH) system with compact wearable pneumatic drive (WPD) unit was developed. The PTAH system consists of left and right diaphragm-type blood pumps and two WPD units. Two blood pumps were designed to fit anatomy, and these had housing made of polyurethane resin. The sizes of the left and right pumps are 95 x 68 x 49 mm and 104 x 74 x 44 mm. The stroke volumes of the left and right pump are 85 and 94 ml, respectively. The WPD unit consists of a brushless DC motor, a crankshaft, a cylinder-piston, non-circular gears, and air pressure regulation valves. Driving air pressure is generated by the cylinder-piston. The non-circular gears generate the fixed systolic ratio. The size and weight of the WPD unit are 20 x 8.5 x 20 cm and 1.8 kg, respectively.The performance of the PTAH system was confirmed using an overflow-type mock circulation test. The pump output of more than 8 L/min using the left blood pump was achieved. The mean electric power consumption was approximately 20 W at 105bpm of pump rate.The fundamental performance of the PTAH system was evaluated in acute animal experiment. The left and right pumps were implanted in a calf weighing 98 kg. Two WPD units with fixed systolic ratio of 35 and 44% were connected to the left and right blood pumps with 2 m air hoses, respectively. The cardiac output ranged from 3.9 to 5.4 L/min at mean aorta pressures from 108 to 115 mmHg at pump rates from 60 to 100 bpm. The average electric power consumption in each WPD unit varied from 5.3 to 17.6 W according to the beating rate, and the efficiency was estimated from 2 to 9%.