Technical note: a durable impeller pump with rolling bearing and purge system

Our former works demonstrated that the authors' impeller pump could support the circulation of experimental animals for several months without harm to blood elements and organ function of the animals. The termination of the experiments was mostly related to wear of the mechanical bearing and the thrombosis along the bearing. To solve the bearing problem, a magnetic bearing was investigated in our laboratory, resulting in some new problems, such as complicated design and control, considerable energy consumption and lower reliability. Progress in developing an impeller pump for long-term application has been achieved recently. Instead of using a slide bearing, a rolling bearing system has been devised. Its service life is more than ten years due to a wear-proof roller made of ultra-high molecular weight poythene. In order to avoid thrombus formation, a special purge system was introduced to the bearing, thus saline with heparin can be infused through the bearing into the pump. Therefore, the bearing keeps working in the saline, and no thrombus will be formed along the beating. The animal experiments demonstrated that 30 cc fluid infusion per hour continuously or interruptedly is enough to prevent the thrombus formation. With these improvements, the impeller pump was continuously run for one year and no bearing wear was measured in the endurance test. The device weighing 150g is fully implantable, consumes around 9.6 W electric energy by delivering 9 l min(-1) blood flow against 120 mmHg mean pressure and reaches a highest total efficiency, 24.7%, of motor (including controller) and pump at this point, which can produce both pulsatile and non-pulsatile flow according to the requirements.