Patent GB-1233156-A (GB)
IPC: A61M60/554
Filed: 1969-06-23
Abstract: 1,233,156. Artificial heart. UNITED STATES ATOMIC ENERGY COMMISSION. 23 June, 1969 [11 July, 1968], No. 31487/69. Heading A5R. [Also in Division F2] An artificial heart system includes artificial systemic and pulmonary ventricular sacs 28, 24 actuated by a fluid reciprocated by fluid actuated pumps 37, 36 respectively, the pumps being driven through switching means 61, 62 by fluid from high and low pressure, conduits 58, 59 to effect systole and diastole of the sacs alternately, the switching being effectable by full systolic and full diastolic actuation of the pumps.  As described the heart system comprises artificial right or pulmonary and left or systemic ventricles 23, 27 connected via one-way valves to natural atria 13, 15 or atrial remnants and to the pulmonary and systemic circulation systems. The ventricles each comprise a flexible plastics sac 24, 28 in a semi-rigid housing 25, 29 connected by conduits 38, 47 to pumps 36, 37. During systole, a pumping fluid is pumped into the housings to compress the sacs and during diastole the pumping fluid is withdrawn to the pumps. The pumping fluid is moved by bellows 39, 48 between diaphragms 41, 50 and chamber housings, the diaphragms being moved leftward and rightward by pairs of driving bellows 42' 42, 43'43, 51'51, 52'52. Bellows 39 and 48 are annular with evacuated spaces 40, 49, and cooperate with bellows 81, 84 maintained at ambient atmospheric pressure via line 82 and flexible sac 83, to ensure that during diastole, pressure in the veins is maintained substantially at atmospheric pressure to prevent their collapse. The driving bellows of the pump 37 connected to the left ventricle (where a relatively greater pressure is needed to drive blood through the systemic circulatory system than through the pulmonary system) are connected alternatively to high and low pressure gas lines 58, 59 via spool valve 62 to move the diaphragm 50 alternately left and right. Movement of the spool valve 62 is controlled by bistable fluid switch 61 which comprises high pressure inlet 64 and high pressure outlets 65, 66. The outlets of the fluid switch are also connected to the corresponding inlet and outlet passages of the pulmonary ventricle pump 36. Being a bistable, fluid switch, high pressure gas flows through either outlet 65 or 66 until back pressure, as a result of the diaphragm 41 having moved fully in one or other direction, causes high pressure gas stream to switch to the other outlet in the switch, to move the spool valve and diaphragm 41 the other way until the process is repeated. Working fluid from the spool valve and bellows 42 &c. vents ultimately to the low pressure line 59, from which it returns to the high pressure line via heat exchangers 137 and compressor 56. Because of the need for a lower pressure to be supplied to the pulmonary or right ventricle than to the systemic or left ventricle, the high pressure gas from the high pressure line is supplied indirectly to the pulmonary pump via the switch.  To provide a variable rate of pumping dependant on demand, exhaust of gases from the pumps during diastole is controlled by throttle valves 79, 80 (Figs. 3 and 4, not shown) controlled by the pressure of blood in the left and right atria respectively acting through fluid amplifiers 92, 96 (and Fig. 2 not shown). To ensure that systole is initiated within a prescribed period of time, especially when the body is relaxed, a fluid condenser 85 between restrictors 86, 87 is connected in a line 45 between fluid switch outlet passage 65 and a switching inlet 89 so that after a predetermined delay, the capacitor will fill and pressure from the switching passage will cause the output of switch 61 to transfer to outlet passage 66 initiating systole irrespective of the position of diaphragm 41.  Excess heat from the gas is transferred to the pumping fluid by heat exchanger 137, and from the pumping fluid to the blood by heat exchanger 136 and the walls of sac 24.