Development of a new compact centrifugal blood pump system for extracorporeal circulation and its application

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A new compact centrifugal blood pump system for use for cardiac-assisted circuration has been developed by the project members in the first poject year: The impeller of the pump was connected directly to a miniature DC serevomotor by using a simple-gear coupling. Either pulsatile or nonpulsatile flow was produced by controlling the cuttent supply to the motor. Through in vitro tests, the pump characteristics and the degree of hemolysis were evaluated with regard of the configuration of the casing and the impeller. In accordance with the project grograms. the following results have been obtained.1. The semi-open type impeller having the blade angles at the inlet of 20゜and at the outlet of 50゜was the most appropriate a blood pump.2. The pumpgin capacity and the degree of hemolysis produced by the pump with volute casing were significatly improved at high flow rate region compared with those by the pump without volute casing.In the second project year, to analyse myocardial adaptive change of the nucleic acid metabolism in response to the prolonged left ventrecular (LV) pressure load reduction, LV to aorta bypass experiments were carried out in mongrel dogs using the newly developed system. After 10 hours bypadd with 50 - 80 % reduction compared with the control level of the peak-LV pressure, RNA polymerase activity was measured in purified nuclear preparation from left and right ventricular muscles. The of RNA polymerase activity of left to right ventricular muscule showed to decrease as compared with those of the control group. From thies result, it is suggested that the myocardial nucleic acid metabolism change following pressure load reduction would be originated without so much long period of time, and that the myocardial adaptive change would progress an opposite way against the cardiac hypertrophy process.The whole programs of this project were completed in this year with satisfactory results as described above.