Picart C, Piau J M, Galliard H, Carpentier P
Laboratoire de Rhéologie, Université Joseph Fourier-Grenoble 1, Institut National Polytechnique de Grenoble, France.
Biorheology. 1998 Jul-Oct;35(4-5):335-53. doi: 10.1016/S0006-355X(99)80015-8.
Red blood cell (RBC) aggregation is of prime importance in vivo and in vitro for low flow rates. It may be estimated by rheometrical measurements at low shear rates, but these are perturbed by slip and migrational effects which have already been highlighted in the past. These effects lead to a torque decay with time so that the true value of the stress at low shear rates may be greatly underestimated. Elevated aggregation being associated with different diseases, pathological blood samples show more pronounced perturbing effects and a strong time dependency in low shear rate rheometry. To test the dependence of slip and migrational effects on RBC aggregation, and particularly to determine the way in which they depend upon fibrinogen concentration ([Fb]), a home-made measuring system with roughened internal and external walls (170 microns roughness) was used to study low shear rate rheometry for RBC suspensions in PBS buffer containing albumin (at 50 g/l) and fibrinogen at various concentrations. The influences of hematocrit, shear rate, and fibrinogen concentration were investigated. Particular attention was paid to data acquisition at low shear rates (10(-3) s-1 to 3 x 10(-2) s-1). The combined influence of hematocrit and fibrinogen was investigated by adjusting hematocrit to 44 or 57% and fibrinogen concentration ([Fb]) to 3.0-4.5-6.5 g/l. Microscopic observations of the blood samples at rest were performed. They showed that different structures were formed according to fibrinogen concentration. The rheometrical measurements indicated that torque decay with shearing duration was strongly dependent on fibrinogen concentration and on shear rate at fixed hematocrit. Migrational and slip effects were more pronounced as shear rate decreased, fibrinogen concentration was raised, and hematocrit was lowered. The results have been explained on the basis of the expected microstructure of flowing blood in relation to the microscopic observations at rest.
红细胞（RBC）聚集在体内和体外对于低流速而言至关重要。它可以通过低剪切速率下的流变测量来估计，但这些测量会受到滑移和迁移效应的干扰，过去已经强调过这些效应。这些效应导致扭矩随时间衰减，以至于低剪切速率下应力的真实值可能被大大低估。聚集增加与不同疾病相关，病理血样在低剪切速率流变测量中显示出更明显的干扰效应和强烈的时间依赖性。为了测试滑移和迁移效应与红细胞聚集的相关性，特别是确定它们依赖于纤维蛋白原浓度（[Fb]）的方式，使用了一种内壁和外壁粗糙（粗糙度为170微米）的自制测量系统来研究在含有白蛋白（50 g/l）和不同浓度纤维蛋白原的PBS缓冲液中红细胞悬浮液的低剪切速率流变学。研究了血细胞比容、剪切速率和纤维蛋白原浓度的影响。特别关注了低剪切速率（10^(-3) s^(-1)至3×10^(-2) s^(-1)）下的数据采集。通过将血细胞比容调整为44%或57%，纤维蛋白原浓度（[Fb]）调整为3.0 - 4.5 - 6.5 g/l，研究了血细胞比容和纤维蛋白原的综合影响。对静置血样进行了显微镜观察。结果表明，根据纤维蛋白原浓度形成了不同的结构。流变测量表明，在固定血细胞比容下，扭矩随剪切持续时间的衰减强烈依赖于纤维蛋白原浓度和剪切速率。随着剪切速率降低、纤维蛋白原浓度升高和血细胞比容降低，迁移和滑移效应更加明显。已根据流动血液的预期微观结构与静置时的显微镜观察结果对结果进行了解释。
