The influence of red blood cell aggregation and deformability on the viscoelasticity, erythrocyte sedimentation-rate and density of blood

The application of the high resolution density measurement technique is extended to hemorheological investigations. The density measurement is used to continously track the sedimentation properties of red blood cells in blood samples anticoagulated with isotonic sodium citrate solution. In the same step the volume fraction of red blood cells, the hematocrit, is calculated from the density of the homogeneous suspension and that of the separated plasma layer. The hematocrit determined by density measurements is somewhat smaller than the hematocrit evaluated by centrifugation techniques. The ratio of the two values is related to the packing density of red blood cells that can be reached with a centrifuge. The packing density of normal red blood cells correlates significantly with corrected viscoelastic data calculated from the complex viscosity of 50 normal blood samples (P<0.001). Since this correlation is evaluated for blood samples with normal erythrocyte sedimentation-rates, this dependence is suggested to be due to slight differences in the deformability of red blood cells.