Blood damage and turbulence: in vitro study of the turbulence-induced hemolysis in a Taylor-Couette-System

湍流引起的血液损伤是心室辅助装置等心血管植入物临床使用中的一个巨大问题。目的：研究湍流对离体血液的损伤作用。这还没有实现，因为流体力学中常用的湍流室不适合研究血液流动。使用一个实验湍流室，泰勒-库埃特系统（TCS）与反向旋转的圆柱体，湍流可以产生，和血液损伤所造成的湍流特性可以进行实验研究。最新技术水平：在国际文献中，血液损伤对心室辅助器械的重要性被判定为一个重要问题。提出了各种损伤模型，但各模型之间以及模型与基础实验之间缺乏共识。目前，没有已知的体外模型，其允许使有限的血液体积经受限定的湍流。假设：假设是，可以在特殊的TCS中对湍流引起的血液损伤进行实验研究。在该流动室中，内筒和外筒可以彼此独立地旋转。当以不同的旋转速度反向旋转时，在两个圆筒之间的差距中产生无特征的湍流。到目前为止，这种效应尚未用于研究湍流引起的血液损伤。此外，在相同的库埃特流动室中可以产生具有相似平均剪切速率的几乎均匀的层流剪切流。利用这一特性，可以直接比较层流和湍流条件。方法：使用具有反向旋转圆柱体的TCS，在差距中产生湍流。使用相同的流动室，差距中的流体可以经受具有相同平均剪切速率的层流和湍流剪切流。使用模拟血液多相行为的测试流体和两个速度分量LDA探针来研究流动特性。特征湍流参数作为旋转速度的函数进行评估，并且将研究流动条件、湍流强度、时间的影响以及这些湍流参数的方差。对于血液损伤的评估，使用当前临床标准方法研究动物和健康志愿者的血液样品。最后，将开发基于湍流参数的血液损伤预测模型。

Blood damage caused by turbulence is a huge problem in the clinical use of cardiovascular implants such as ventricular assist devices. Objective: The objective of the project is to investigate the blood damage caused by turbulence in-vitro. This has not yet been achieved, as turbulence chambers commonly used in fluid mechanics are not suited for investigation of blood flows. Using an experimental turbulence chamber, a Taylor-Couette system (TCS) with counter-rotating cylinders, turbulence can be generated, and blood damage caused by turbulent flow features can be investigated experimentally. State of the art: The importance of blood damage for ventricular assist devices is judged as an important issue in the international literature. A variety of damage models is presented, but there is a lack of consensus between the respective models as well as between models and underlying experiments. Currently, there is no in-vitro model known, which permits to subject a limited blood volume to a defined turbulence. Hypothesis: The hypothesis is, that blood damage caused by turbulence can be experimentally investigated in a special TCS. In this flow chamber the inner and the outer cylinder can be rotated independently from each other. When counter rotating with distinct rotational speeds, featureless turbulence is generated in the gap between both cylinders. So far, this effect was not yet used for the investigation of blood damage due to turbulence flows. Furthermore, a nearly homogenous laminar shear flow with similar average shear rates can be generated in the same Couette flow chamber. Using this feature, a direct comparison between laminar and turbulent flow conditions can be performed. Methods: Using the TCS with counter rotating cylinders, a turbulent flow is generated in the gap. Using the same flow chamber, the fluid in the gap can be subjected to laminar and turbulent shear flow with the same average shear rate. The flow characters are investigated using a test fluid modelling the multiphasic behavior of blood and a two velocity-component LDA probe. Characteristic turbulence parameters are assessed as a function of rotational speed and effects of flow conditions, turbulence intensity, time will be investigated as well as the variance of those turbulent parameters. For the assessment of blood damage, blood samples of animals and healthy volunteers are investigated with current clinical standard methods. Finally, a model for prediction of blood damage based on turbulence parameters will be developed.