Spatio-temporal variations in cell-free layer formation near bifurcations of small arterioles.

Blood flow partitioning at an arteriolar bifurcation could lead to spatio-temporal variations in cell-free layer formation in the upstream and downstream vessels of the bifurcation. To investigate this effect, we quantitatively analyzed characteristics of the cell-free layer in the vicinity of an arteriolar bifurcation in the rat cremaster muscle in normal physiological flow conditions. To simulate hemorheological relevance to humans, red blood cell aggregation was elevated by infusion of Dextran 500 to levels seen in humans in normal states. Spatial variations of the layer width were observed in both the parent and larger daughter vessels. A more pronounced attenuation of the layer width was generally observed in the parent vessel at its wall adjacent to the side branch than at its opposite wall. A thicker layer width was consistently found at the opposite than adjacent wall of the larger daughter vessel. Accordingly, large asymmetries of the layer widths could be developed on opposite sides of the larger daughter vessel, which were significantly greater (P<0.01) than those observed in the parent vessel. A positive correlation was generally observed between mean layer widths in the downstream vessel and on the side of the parent vessel from which bulk of the flow enters the downstream vessel. The fraction of the downstream layer formation constituted by the side branch decreased with increasing flow fraction in this vessel. These findings confirmed the modulation of the cell-free layer formation near an arteriolar bifurcation, implicated by flow separation at the bifurcation.