Toward a durable impeller pump with mechanical bearings.

Our former work demonstrated that our impeller pump could support the circulation of experimental animals for several months without harm to blood elements or organ function. The termination of the experiments was mostly related to wear of the mechanical bearing and thrombosis along the bearing. To solve the bearing problem, we investigated a magnetic bearing in our lab, which resulted in some new problems, such as complicated design and control, considerable energy consumption, and lesser reliability. Progress in developing an impeller pump for long-term application has recently been achieved. Instead of using a sliding bearing system, we devised a rolling bearing system. Its service life is more than 10 years because of a wearproof roller made of ultra high molecular weight polythene. To avoid thrombus formation, we introduced a special purge system to the bearing, allowing the saline with heparin to be infused through the bearing into the pump. The bearing, therefore, keeps working in the saline, and no thrombus will be formed. Animal experiments demonstrated that a 30 ml fluid infusion per hour is enough to prevent thrombus formation. With these improvements, the impeller pump has continuously run for 8 months, and no bearing wear can be measured. The device, weighing 150 g, is fully implantable, consumes approximately 9.6 watts, and delivers a 9L/min blood flow against a 120 mm Hg mean pressure and reaches a highest total efficiency of 24.7% for the motor (including the controller) and pump. The system can produce both pulsatile and nonpulsatile flow according to requirements.