2018 Volume 7 Pages 141-145
An extracorporeal membrane oxygenator (ECMO) is used for the management of severe heart or respiratory failure. In the conventional ECMO system, centrifugal blood pumps are commonly used in recent years. However, a relatively high rotational speed is required to perfuse against the high hydrodynamic resistance of the system circuit. High rotational speed causes high shear stress. To provide a blood pump that can be operated at a lower rotational speed than conventional centrifugal blood pumps, we propose a novel high-pressure type rotary blood pump named the toroidal convolution pump (TCP). In the TCP, fluid that acquires centrifugal force from rotation of the impeller is returned to the impeller through the flow path and again acquires centrifugal force. With repetition of this cycle, fluid is accelerated to generate high pressure. We investigated the performance and basic property of the TCP using an experimental model and computational fluid dynamic (CFD) analysis. The TCP generated pump output of 5 L/min against a pressure head of 350 mmHg at a rotational speed of 2450 rpm. This rotational speed is much lower than that of conventional centrifugal blood pumps, which is usually higher than 3000 rpm. The efficiency of the TCP including the motor was approximately 4.2% at that setting. CFD analysis showed symmetrical pressure distribution about the central pivot bearing. The pressure difference between inlet and outlet ports was approximately 40% higher than that of the experimental model. We found no excessive negative pressure that would cause hemolysis. Although we identified areas of high sheer stress, hemolysis is estimated to be low because of the short exposure time to the high sheer stress. We found no stagnant area that would cause thrombus formation.