Stadler A, Linderkamp O
Department of Pediatrics, University of Heidelberg, Federal Republic of Germany.
Microvasc Res. 1989 May;37(3):267-79. doi: 10.1016/0026-2862(89)90045-9.
This study was designed to analyze the flow behavior of red blood cells (RBCs) in circular vessels with diameters of 3 to 6 microns by means of a mathematical model. According to this model, the RBC flow velocity is 1 mm/sec, RBCs assume axisymmetric shape, and the gap between the RBC and the vessel wall allows sufficient lubrication. The flow resistance depends on the surface area and volume of RBCs, the plasma viscosity, and the vessel diameter. Surface area and volume of RBCs from 10 term neonates and 10 adults were determined by means of a micropipet system and plasma viscosity was measured using a capillary viscometer. Neonatal RBCs had larger volumes (107 +/- 6 fl vs 90 +/- 4 fl) and surface areas (154 +/- 7 microns 2 vs 137 +/- 7 microns 2) than adult RBCs (P less than 0.005). Plasma viscosity was lower in neonates than in adults (1.04 +/- 0.10 cP vs 1.26 +/- 0.13 cP; P less than 0.005). The flow model leads to the following conclusions: During the passage of 3- to 6- microns vessels, the large neonatal RBCs are more elongated than the smaller adult RBCs. In vessels with diameters of less than 3.3 microns, the rear of neonatal RBCs becomes convex, whereas this critical vessel diameter is 3.1 microns for adult RBCs. If the cells are suspended in the same medium, neonatal RBCs require a 31% higher driving pressure than adult RBCs to achieve the necessary elongation for passing through a narrow capillary. However, both cell types require similar driving pressures, if the cells are suspended in the corresponding plasma. The tube/discharge hematocrit ratio of neonatal RBCs is 1 to 6% higher than that of adult cells. Relative viscosity of neonatal RBCs is approximately 7% higher compared with adult RBCs, whereas the blood viscosity (relative viscosity times plasma viscosity) is 12% less in neonates than in adults. We conclude that the large size of neonatal RBCs may cause impaired flow in narrow vessels with diameters below the critical value of 3.3 microns. In vessels with diameters of 3.3-6.0 microns, the disadvantage of the large size of neonatal RBCs appears to be completely compensated for by the lowr plasma viscosity in the neonate.
本研究旨在通过数学模型分析直径为3至6微米的圆形血管中红细胞（RBC）的流动行为。根据该模型，RBC流速为1毫米/秒，RBC呈轴对称形状，且RBC与血管壁之间的间隙可提供足够的润滑。流动阻力取决于RBC的表面积和体积、血浆粘度以及血管直径。通过微量移液器系统测定了10名足月新生儿和10名成年人的RBC表面积和体积，并使用毛细管粘度计测量了血浆粘度。新生儿RBC的体积（107±6飞升 vs 90±4飞升）和表面积（154±7平方微米 vs 137±7平方微米）均大于成人RBC（P<0.005）。新生儿的血浆粘度低于成年人（1.04±0.10厘泊 vs 1.26±0.13厘泊；P<0.005）。该流动模型得出以下结论：在通过直径为3至6微米的血管时，较大的新生儿RBC比较小的成人RBC更细长。在直径小于3.3微米的血管中，新生儿RBC的后部会凸出，而成人RBC的这一临界血管直径为3.1微米。如果细胞悬浮在相同介质中，新生儿RBC比成人RBC需要高31%的驱动压力才能实现通过狭窄毛细血管所需的伸长。然而，如果细胞悬浮在相应的血浆中，两种细胞类型所需的驱动压力相似。新生儿RBC的管/排血细胞比高于成人细胞1至6%。新生儿RBC的相对粘度比成人RBC高约7%，而新生儿的血液粘度（相对粘度乘以血浆粘度）比成人低12%。我们得出结论，新生儿RBC的大尺寸可能会导致在直径低于临界值3.3微米的狭窄血管中流动受损。在直径为3.3至6.0微米的血管中，新生儿RBC大尺寸的劣势似乎完全被新生儿较低的血浆粘度所弥补。
