Kim Sangho, Kong Robert L, Popel Aleksander S, Intaglietta Marcos, Johnson Paul C
Department of Bioengineering, University of California, San Diego, La Jolla, CA 92093-0412, USA.
Am J Physiol Heart Circ Physiol. 2007 Sep;293(3):H1526-35. doi: 10.1152/ajpheart.01090.2006. Epub 2007 May 25.
Separation of red blood cells and plasma in microcirculatory vessels produces a cell-free layer at the wall. This layer may be an important determinant of blood viscosity and wall shear stress in arterioles, where most of the hydraulic pressure loss in the circulatory system occurs and flow regulatory mechanisms are prominent. With the use of a newly developed method, the width of the cell-free layer was rapidly and repeatedly determined in arterioles (10- to 50-microm inner diameter) in the rat cremaster muscle at normal arterial pressure. The temporal variation of the cell-free layer width was non-Gaussian, but calculated mean and median values differed by <0.2 microm. The correlation length of the temporal variations downstream (an indication of mixing) was approximately 30 microm and was independent of pseudoshear rate (ratio of mean velocity to vessel diameter) and of vessel diameter. The cell-free layer width was significantly different on opposite sides of the vessel and inversely related. Increasing red blood cell aggregability reduced this inverse relation but had no effect on correlation length. In the diameter range studied, the mean width of the cell-free layer increased from 0.8 to 3.1 microm and temporal variations increased from 30% to 70% of the mean width. Increased aggregability did not alter either relationship. In summary, the cell-free layer width in arterioles is diameter dependent and shows substantial non-Gaussian temporal variations. The temporal variations increase as diameter increases and are inversely related on opposite sides of the vessel.
微循环血管中红细胞与血浆的分离会在血管壁处产生一个无细胞层。在小动脉中，这一层可能是血液粘度和壁面剪应力的重要决定因素，而循环系统中大部分液压损失都发生在小动脉中，且流量调节机制在此处也很显著。使用一种新开发的方法，在正常动脉压下，对大鼠提睾肌内径为10至50微米的小动脉中无细胞层的宽度进行了快速且重复的测定。无细胞层宽度的时间变化是非高斯分布的，但计算得到的平均值和中值相差小于0.2微米。下游时间变化的相关长度（混合的一个指标）约为30微米，且与假剪切率（平均速度与血管直径之比）和血管直径无关。血管两侧的无细胞层宽度存在显著差异且呈负相关。红细胞聚集性增加会减弱这种负相关，但对相关长度没有影响。在所研究的直径范围内，无细胞层的平均宽度从0.8微米增加到3.1微米，时间变化从平均宽度的30%增加到70%。聚集性增加并未改变这两种关系。总之，小动脉中无细胞层的宽度取决于直径，并呈现出显著的非高斯时间变化。时间变化随着直径的增加而增加，且在血管两侧呈负相关。
