Affiliations: Rheology Laboratory, Department of Mechanical Engineering, The University of Texas at Austin, Austin, TX 78712, U.S.A.
Abstract: Significant internal structural changes occur in flowing blood when shear strain exceeds the critical value of 1 (unit strain), forcing alignment of the erythrocytes and releasing trapped plasma, which in turn leads to the formation of multiple layers of plasma on which oriented and compacted cells slide. These effects are identified in the inflections in the shear rate dependence of viscoelasticity of normal blood and in the viscous and elastic stress-to-strain relationships. Theoretical factors for plasma release and cell compaction allow calculation of the viscous and elastic properties of the cell layers from measured whole blood viscoelasticity and plasma viscosity. The new plasma release-cell layering theory encompasses, reinterprets and unifies many diverse previous observations relating to how blood flows, and provides a new understanding of the roles of red cell deformability and aggregation tendency.
