Space Technology and CFD Applied to the Development of the DeBakey Heart Assist Device

摘要

Approximately 20 million people worldwide suffer annually from heart failure, a quarter of them in America alone. In the United States, only 2,500 donor hearts are available each year. The DeBakey Ventricular Assist Device (VAD) prolongs life until a suitable transplant heart i s available, and is used to boost blood flow in patients suffering from hemodynamic deterioration, that is, loss of blood pressure and lowered cardiac output. The use of computational fluid dynamics (CFD) technology led to major design improvements in the heart assist device, enabling its human implantation. The DeBakey VAD is a miniaturized heart pump designed to increase blood circulation in heart-failure patients awaiting a transplant. A ventricular assist device has to be small and efficient, generating a 5-liter-per-minute blood flow rate against 100 mm Hg pressure. Because blood i s the operating fluid, the design of a VAD requires that it propel the blood gently, that is, it must minimize damage to the red blood cells. In order to reduce red blood cell damage, the pumping device must be designed to avoid regions of high shear stress and separated flow in the pump. In addition, the blood must be properly washed out of the pump since the formation of blood clots may appear within stagnation regions as a result of previously damaged blood cells. Since the device is small and the operating conditions severe, instrumentation for making necessary flow measurements i s extremely difficult to design. Therefore it became necessary to look at the flow by computational means. The detailed computational flow analysis now affords VAD designers with a view of the complicated fluid dynamic processes inside their devices.