NEW METHODOLOGIES FOR THE DESIGN OF SMALL BLOOD PUMPS

这项研究的长期目标是使搏动心脏替代系统适用于体型较小的成人患者。这是一件非常重要的事情，因为脉动式血泵尺寸的减小会影响(1)泵的流体动力学，(2)泵和执行器的能量学，以及(3)血液接触材料所经历的应力。因此，我们认为这些研究对于为所有成年患者提供人工心脏和搏动性心室辅助装置至关重要。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：首先，我们将比较体外流场测量与体内血栓形成和溶血测量。具体而言，我们将使用激光多普勒风速法和粒子图像测速法在根据不同尺度参数设计的泵室中测量流体速度和剪切速率，具有高度的时空分辨率。经典的无量纲分析将作为尺度的指导，以实现流体动力学的相似性，并将这些测量推广到预测目的。这些发现的意义将通过在小牛体内的研究进行评估，使用完全植入的全人工心脏，在相似的流体动力学条件下使用相同的泵室。血栓形成将通过血液学研究和外植体分析进行评估。使用荧光标记的血小板和纤维蛋白原，通过组织学检查和外显荧光显微镜对血小板和纤维蛋白粘附进行量化。新的快速制造方法将用于制造这些实验所需的各种泵室。其次，我们将利用能量转换器、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，以尽量减少功耗。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缩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。我们期望这项研究将广泛适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和血栓形成之间关系的理解。这项工作需要在外科、工程、流体力学和血液学等多学科的努力下，有效地制造血泵系统，并进行必要的体外和体内研究。

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.