Development of a compact, sealless, tripod supported, magnetically driven centrifugal blood pump

In this study, a tripod supported sealless centrifugal blood pump was desig ned and fabricated for implantable application using a specially designed D C brushless motor. The tripod structure consists of 3 ceramic balls mounted at the bottom surface of the impeller moving in a polyethylene groove inco rporated at the bottom pump casing. The follower magnet inside the impeller is coupled to the driver magnet of the motor outside the bottom pump casin g, thus allowing the impeller to slide-rotate in the polyethylene groove as the motor turns. The pump driver has a weight of 230 g and a diameter of 6 0 mm. The acrylic pump housing has a weight of 220 g with the priming volum e of 25 ml. At the pump rpm of 1,000 to 2,200, the generated head pressure ranged from 30 to 150 mm Hg with the maximum system efficiency being 12%. W hen the prototype pump was used in the pulsatile mock loop to assist the ve ntricle from its apex to the aorta, a strong correlation was obtained betwe en the motor current and bypass flow waveforms. The waveform deformation in dex (WDI), defined as the ratio of the fundamental to the higher order harm onics of the motor current power spectral density, was computed to possibly detect the suction occurring inside the ventricle due to the prototype cen trifugal pump. When the WDI was kept under the value of 0.20 by adjusting t he motor rpm, it was successful in suppressing the suction due to the centr ifugal pump in the ventricle. The prototype sealless, centrifugal pump toge ther with the control method based on the motor current waveform analysis m ay offer an intermediate support of the failing left or right ventricle bri dging to heart transplantation.