Biomechanical Study of Mechanical Damage of Red Cells in Shear Flows with Reference to Homolysis in Artificial Flow Circuits

本研究主要探讨红细胞在剪切力作用下损伤的生物力学分析，特别是人工流路中的溶血现象。为了阐明红细胞在剪切流中的机械损伤，我们研究了红细胞在剪切流中的流动和变形，并检查了作用在细胞膜上的剪切应力。我们在显微镜下直接观察了人红细胞在剪切流中的运动，以及红细胞膜的变形和破裂。由于红细胞的流动和变形在剪切流中从不保持静止，我们设计了新的流动回路，如反向旋转系统和显微镜频闪系统。通过对细胞图像的增强处理，获得了变形红细胞的清晰图像。由于红细胞的变形取决于悬浮介质的粘度以及流动的剪切速率，因此我们使用了各种高粘度的流体，观察到红细胞在高剪切下变形并最终受损。我们认为红细胞损伤的观点的剪切应力诱导的细胞膜。假设细胞膜为粘弹性壳，对剪切变形的红细胞进行了应力分析，发现细胞膜可能受到循环载荷的作用。我们认为红细胞的损伤主要是由于材料在循环载荷下的疲劳所致。最后，通过对各种人工流路的流动状况的考察，研究了溶血的可能原因。

This project deals with biomachanical analysis of the damage of red cells induced in shear with a special reference to hemolysis in artificial flow circuits. To elucidate the mechanical damage of the red cell in shear flows, we studied the flow and deformation of red cells in shear flows and examined the shear stress acting on the cell membrane. We directly observed the motion of human red cells in shear flows under microscope, and their deformation leading to the rupture of the membrane. Since the flow and deformation of the red cell never remains stationary in shear flow, we devised new flow circuits, such as counter-rotating system, and a microscope-strobe system. By intensifying the cell image, we obtained the clear image of the deformed red cell. Since the deformation of the red cell depends upon the viscosity of the suspending medium as well as the shear rate of flow, we used various fluids of high viscosity.The red cell was observed to be deformed and finally damaged under high shear. We considered the red cell damage from a stand-point of shear stress induced in the cell membrane. Assuming the membrane as an viscoelastic shell, we made stress analysis of the deformed red cell in shear and found that the cell membrane may be subject to the cyclic loading. We concluded that the red cell damage may be partically due to the material fatigue of the cyclic loading.Finally, by examining the flow condition of various artificial flow circuits, possible causes of hemolysis were studied.