Development of nutating centrifugal blood pump

Summary

Conventional centrifugal blood pumps have drawbacks: blood degeneration at hot spots in the bearing in closed magnetic coupling drive and infection and contamination through the shaft seal in direct motor drive. To overcome these problems, Baurmeister and Affeld proposed and developed a centrifugal pump with a.nutating (non rotating) impeller, the so-called tea spoon pump. However, a great reduction in hydrolysis is necessary with this pump. Pump performance, therefore, had to be improved. This was done by the following: (a) annular flow passage surrounded with an inner guide wall and outer housing wall; (b) contoured inlet and outlet passage. These amendments serve to achieve rectified flow in the same manner as a piston (impeller) pushing blood in an endless cylinder (annular passage). Centrifugal force as a result of rotating blood flow sustains the pressure difference between the outlet and inlet.

Initially, we tried to make a simplified two-dimensional prototype and then proceeded with three-dimensional models. We experimentally examined the optimum size of the impeller and optimum contour of the housing. To adjust the pump characteristics according to flow rate, we also tried to adopt a flexible outlet diffuser with variable cross section. By means of hemolysis tests compared with results with the roller pump, pump performance is still undergoing improvement.