NEW METHODOLOGIES FOR THE DESIGN OF SMALL BLOOD PUMPS

这项研究的长期目标是让较小的成年患者可以使用脉搏心脏替代系统。这不是一件微不足道的事情，因为脉动血泵尺寸的减小会影响(1)泵的流体动力学，(2)泵和执行器的能量，以及(3)血液接触材料所承受的压力。因此，我们认为这里所描述的研究对于为所有成年患者提供人工心脏和搏动性心脏辅助设备是至关重要的。我们建议通过三个具体目标来研究泵尺寸减小的基本原理：第一，我们将比较体外流场测量与体内血栓形成和溶血测量。具体地说，我们将使用激光多普勒测速仪和粒子图像测速仪来测量根据不同比例参数设计的泵室中的流体速度和剪切率，具有高空间和时间分辨率。经典的无量纲分析将作为缩放的指导，以实现流体动力学相似性，并出于预测目的对这些测量进行推广。这些发现的意义将通过在小牛身上进行体内研究来评估，这些研究使用完全植入的全人工心脏，使用相同的泵室，在类似的流体动力学条件下。血栓形成将通过血液学研究和外植体分析进行评估。血小板和纤维蛋白的粘附性将通过组织学检查和表观荧光显微镜，使用荧光标记的血小板和纤维蛋白原进行量化。新的快速制造方法将被用来制造这些实验所需的各种泵室。其次，我们将利用对能量转换器、血泵、循环、控制器和能量传输系统的计算机模拟，建立控制系统能量性能的关系。因此，我们将优化主要子系统，以最大限度地降低功耗。结果将在模拟循环回路上进行验证。第三，我们将利用有限元分析研究减小泵腔尺寸和泵形状参数对生物材料应力的影响。预测的应变将使用静压泵室进行验证。我们希望这项研究将广泛应用于脉动血泵的设计，特别是通过提高我们对复杂、时变流场中流体动力学与血栓形成之间关系的理解。这项工作需要外科、工程学、流体力学和血液学等多学科的努力，以及有效制造血泵系统和进行必要的体外和体内研究的手段。

The long-term objective of this research is to make pulsatile heart replacement systems available to smaller adult patients. This is a non- trivial matter, because reduction in the size of a pulsatile blood pump affects (1) the fluid dynamics of the pump, (2) the energetics of the pump and actuator, and (3) the stresses experienced by the blood contacting materials. Thus, we consider studies such as those described here to be critical to the availability of artificial hearts and pulsatile ventricular assist devices for the full spectrum of adult patients. We propose to study the underlying principles of pump size reduction through three specific aims: First, we will compare in vitro measurements of the flow field with in vivo measures of thrombogenesis and hemolysis. Specifically, we will use Laser Doppler Anemometry and Particle Image Velocimetry to measure fluid velocity and shear rate, with a high degree of spatial and temporal resolution, in pump chambers designed according to various scaling parameters. Classical dimensionless analysis will serve as guidance in scaling to achieve fluid dynamic similitude, and to generalize these measurements for predictive purposes. The significance of these findings will be assessed through in vivo studies in calves using completely implanted total artificial hearts, using the same pump chambers under similar fluid dynamic conditions. Thrombogenesis will be assessed through hematology studies and explant analysis. Platelet and fibrin adhesion will be quantified using histological examination and epi-fluorescence microscopy, using fluorescently labeled platelets and fibrinogen. Novel rapid manufacturing methods will be used to fabricate the variety of pumping chambers required for these experiments. Secondly, we will develop relationships governing energetic performance of the system, utilizing a computer simulation of the energy converter, blood pump, circulation, controller, and energy transmission system. We will thereby optimize the major subsystems to minimize power consumption. Results will be validated on a mock circulatory loop. Thirdly, we will study the effects of reduced pump chamber size and pump shape parameters on biomaterial stresses using finite element analysis. Predicted strains will be validated using staticly pressurized pump chambers. We expect that this research will be broadly applicable to pulsatile blood pump design, especially by improving our understanding of the relationships between fluid dynamics and thrombogenesis in a complex, time-varying flow field. This work requires a multi-disciplinary effort in surgery, engineering, fluid mechanics, and hematology, with the means to efficiently manufacture blood pump systems and carry out the necessary in vitro and in vivo studies.