A double perfusion‐pump

THE heart-lung preparation of Starling and his co-workers has provided a means, extensively used, of studying the functions of the mammalian heart when working against an artificial and adjustable peripheral resistance, which replaces the natural resistance of the systemic vascular system. Many schemes have been devised and used, on the other hand, in which the blood has been perfused through the living vessels of an organ or part of the body by use of an artificial pump. Our original object in devising the pump here described was to produce an adjustable mechanism which could be used to replace the heart, and to carry on both major and minor circulations of the whole body. This would obviously require two synchronously working pumps. Since the two pumps would be working against widely different resistances it was further important that their throws should be rapidly and independently adjustable while running, so as to maintain such equality of output on the two sides as would prevent accumulation of blood on one side of the system, with deleterious back-pressure on the capillaries of the lungs or of the rest of the body, as the case might be. If the pumps and tubular connections were perfectly non-distensible, it should, theoretically, be possible to dispense with such adjustment; the two pumps being set to deliver equal amounts per stroke, they should continue to do this whatever changes occurred in the relation of the pressures they had to overcome. In practice, however, it would be very difficult to make a system of such ideal rigidity. The apparatus which we designed, in which diaphragmpumps were used, certainly would not have it. The arrangement was accordingly devised which enabled the throw of either pump lever to be increased or decreased quickly and adjusted with delicacy. Emb 1 ey and Martin (This Journal, 32. p. 147. 1905) used two rubber bulbsyringes, compressed by adjustable rotating cams, for a similar purpose. Our apparatus should give greater rapidity and precision of control, but the principle is the same.