Chebbi Rachid
Department of Chemical Engineering, American University of Sharjah, Sharjah, United Arab Emirates.
J Biol Phys. 2018 Dec;44(4):591-603. doi: 10.1007/s10867-018-9508-5. Epub 2018 Sep 15.
Blood flow in micro capillaries of diameter approximately 15-500 μm is accompanied with a lower tube hematocrit level and lower apparent viscosity as the diameter decreases. These effects are termed the Fåhraeus and Fåhraeus-Lindqvist effects, respectively. Both effects are linked to axial accumulation of red blood cells. In the present investigation, we extend previous works using a shear-induced model for the migration of red blood cells and adopt a model for blood viscosity that accounts for the suspending medium viscosity and local hematocrit level. For fully developed hematocrit profiles (i.e., independent of axial location), the diffusion fluxes due to particle collision frequency and viscosity gradients are of equal magnitude and opposite directions. The ratio of the diffusion coefficients for the two fluxes affects both the Fåhraeus and Fåhraeus-Lindqvist effects and is found related to the capillary diameter and discharge hematocrit using a well-known data-fit correlation for apparent blood viscosity. The velocity and hematocrit profiles were determined numerically as functions of radial coordinate, tube diameter, and discharge hematocrit. The velocity profile determined numerically is consistent with the derived analytical expression and the results are in good agreement with published numerical results and experimental data for hematocrit ratio and hematocrit and velocity profiles.
直径约为15 - 500微米的微毛细血管中的血流伴随着较低的管内血细胞比容水平，并且随着直径减小表观粘度降低。这些效应分别被称为法厄斯效应和法厄斯 - 林德奎斯特效应。这两种效应都与红细胞的轴向聚集有关。在本研究中，我们扩展了先前的工作，使用了一种剪切诱导的红细胞迁移模型，并采用了一种考虑悬浮介质粘度和局部血细胞比容水平的血液粘度模型。对于充分发展的血细胞比容分布（即与轴向位置无关），由于颗粒碰撞频率和粘度梯度引起的扩散通量大小相等且方向相反。两种通量的扩散系数之比影响法厄斯效应和法厄斯 - 林德奎斯特效应，并且通过使用一个著名的表观血液粘度数据拟合相关性发现其与毛细血管直径和排出血细胞比容有关。速度和血细胞比容分布通过数值方法确定为径向坐标、管径和排出血细胞比容的函数。通过数值确定的速度分布与推导的解析表达式一致，并且结果与已发表的血细胞比容比、血细胞比容以及速度分布的数值结果和实验数据高度吻合。
