Das Bigyani, Bishop Jeffrey J, Kim Sangho, Meiselman Herbert J, Johnson Paul C, Popel Aleksander S
Center for Scientific Computation and Mathematical Modeling, University of Maryland, College Park, MD 20742, USA.
Clin Hemorheol Microcirc. 2007;36(3):217-33.
Knowledge of the effects of red blood cell aggregation on blood flow in small vessels is crucial to a better understanding of resistance changes in the venous microcirculation. Recent studies on rat spinotrapezius muscle indicate that enhanced red blood cell aggregation, induced by dextran 500, significantly affects velocity profiles at pseudoshear rates (the ratio of mean velocity to diameter) less than 40 s(-1). Since the use of a power-law model to describe these profiles does not provide a consistent rheological description, we have evaluated using the Casson model that has been widely used to characterize in vitro blood rheology. In the present study, we report experimental values of rat blood viscosity in the presence of dextran 500 and combine these in vitro measurements with previously obtained in vivo venular velocity profiles to determine whether the Casson model can provide a valid description of in vivo velocity profiles. Our analysis shows that the two-phase Casson model with a peripheral plasma layer is in quantitative agreement with experimentally obtained velocity profiles obtained in venules of rat spinotrapezius muscle under low flow rate. These results have implications for pathological low-flow conditions, such as hemorrhage and sepsis, and they quantitatively describe blunted velocity profiles and elevated flow resistance in postcapillary venules.
了解红细胞聚集对小血管内血流的影响对于更好地理解静脉微循环中的阻力变化至关重要。最近对大鼠斜方肌的研究表明，由右旋糖酐500诱导的红细胞聚集增强，在假剪切率（平均速度与直径之比）小于40 s(-1)时，会显著影响速度分布。由于使用幂律模型来描述这些分布并不能提供一致的流变学描述，我们使用了广泛用于表征体外血液流变学的Casson模型进行评估。在本研究中，我们报告了存在右旋糖酐500时大鼠血液粘度的实验值，并将这些体外测量结果与先前获得的体内小静脉速度分布相结合，以确定Casson模型是否能够有效描述体内速度分布。我们的分析表明，具有外周血浆层的两相Casson模型与在低流速下大鼠斜方肌小静脉中实验获得的速度分布在数量上一致。这些结果对诸如出血和脓毒症等病理性低流量状况具有启示意义，并且它们定量描述了毛细血管后小静脉中变钝的速度分布和升高的血流阻力。
