Blood Flow Through Channels and Clearances in Implantable Pumps

Implantable rotary blood pumps are very effective at supporting patients with heart failure. New designs demonstrate distinct advantages over their predecessor diaphragm type pumps and have generated vast interest in the medical devices community, as demonstrated by hundreds of technical publications and newer commercially available devices. In addition to mechanical design criteria, these pumps share the requirement of moving a relatively large amount of blood through a miniaturized pump without damaging the blood cells. The fluid channels within the impeller are typically 1–3 mm wide and the clearance between the blades, rotating at 2,000–10,000 rpm, and the stationary housing is approximately 100–300μm. This paper gives examples of experimental and numerical methods to characterize the flow field, and a summary of how the flow affects blood cells and design strategies to minimize blood damage.