Analysis of flow behavior of blood-biomaterial interfaces

剪切力是一个张量，被认为是溶血的基本因素，而溶血程度是一个标量。因此。作者提出了能量耗散率E（J/m^3）作为剪切应力的广义替代，并对血浆游离血红蛋白给出了以下表达式：H=kE^αt（其中，k和α为常数，H：血红蛋白水平）此外，由于应力类型，即粘性应力和雷诺应力，阈值剪切水平的差异被认为仅与暴露时间有关。因此，初步的体外溶血试验已经进行了使用，以澄清层流和湍流对hemolysis的影响，在本实验中，两种类型的具有不同粘度的悬浮介质被用来检查一个足够宽的范围内的雷诺数，而不改变红细胞压积或暴露时间。将牛红细胞悬浮在盐水中用于湍流条件，悬浮在葡聚糖溶液中用于层流条件。悬浮液的粘度分别为1.56cP和5.20cP。血液在100-500 Pa的剪切应力下循环90 min。计算Blasius摩擦因子以验证流动条件为层流或湍流。实验结果表明，湍流条件下的溶血速率是层流条件下的4倍，说明粘性应力和雷诺应力对溶血的影响并不总是相等的。然后，可以认为能量耗散在预测溶血水平方面起重要作用。

Shear stress, which is a tensor value, is regarded as an essential factors of hemolysis, but hemolysis level is a scalar value. Therefore. the authors proposed energy dissipation rate E (J/m^3) as a generalized substitute for shear stress and have formulated the following expression for plasma free hemoglobin.H=kE^αt (where, k and α are constant values, H : hemoglobin level)In addition, the difference in the threshold shear level due to the type of stress, namely viscous and Reynolds stress, is believed to be related only to the exposure time. Therefore, preliminary in vitro hemolysis test has been performed using to clarify the effects of laminar and turbulent flows on hemolysis.In the present experiments, two types of suspension media with different viscosities were used to examine a sufficiently wide range of Reynolds numbers without altering hematocrit or exposure time. Bovine red blood cells were suspended in saline for turbulent flow condition and in dextran solution for laminar flow condition. The viscosity of the suspensions were 1.56cP and 5.20cP, respectively. Blood was circulated for 90 min under the shear stress of 100-500 Pa.Blasius friction factor was calculated to verify flow condition as a laminar or turbulent. The experimental results exhibited that hemolysis rate under turbulent flow was four times higher than that under laminar flow, suggesting that the effect of viscous and Reynolds stress on hemolysis is not always equal. Then, it became possible to consider that energy dissipation took an important role to predict a level of hemolysis.