Pediatric portable ventricular assist device is still lacking in Japan. We have developed three small axial-flow blood pumps, KPAP1, KPAP2, and KPAP3, which feature in blood contacting surfaces made of polymer and can be disassembled with a screw. Though the impeller diameters are all 12.4 mm, necessary pressure of 100mmHg can be attained at 13000, 12500, 12000 rpm for three pumps, respectively. When the impeller outflow angles were changed from 90 deg to 50 deg, the overall efficiencies have improved from 14% to 16% and the hemolysis rates have improved from 9.3 times to 3.6 times, compared with an extracorporeal centrifugal pump. It is thought to be caused by reduction of fluid dynamic stall.
