Erythrocyte sedimentation of human blood at varying shear rates

Abstract

Findings are reported on the erythrocyte sedimentation of blood subjected to varying shear rates. The blood was obtained from healthy adult human subjects. Whole blood, anticoagulated with EDTA, was exposed to shear rates from 0.0001 to 10 sec⁻¹ with readings taken at zero shear as control. From zero to 0.01 sec⁻¹ no change in the sedimentation rate was observed. However, from 0.01 sec⁻¹ the sedimentation rate increased, reaching a maximum at 0.1 sec⁻¹. From 0.1 to 10 sec⁻¹ the rate decreased progressively to zero, Individual differences found between donors were not significant. Tentative explanations for the above findings in relation to the various shear rates are discussed. They include the balance and relationships between electrostatic forces and the diffusivity of erythrocytes. Our findings may mirror flow properties in certain parts of the the microcirculation, since erythrocyte sedimentation changes with varying shear rates. It is emphasized that increased erythrocyte sedimentation is not necessarily a sign of disease but can be a physiological occurrence in certain parts of the circulation which may well be one of the prerequisites for maintaining certain functions of the blood. Copley’s hypothesis on blood cellular clumping, proposed in 1958, which brings together the views of Fåhraeus and Knisely, is discussed in connection with the erythrocyte sedimentation, According to his view, intravascular clumping is identical with either rouleau formation, which he considers as reversible aggregation of erythrocytes, or with their agglutination, which is an irreversible process of clumping. It is pointed out that erythrocyte agglutinates may well be an important factor in increased sedimentation rates and be mainly responsible for these in pathological conditions, a problem which is in need of experimental study. In an Appendix to the paper, a mathematical interpretation of the parameters affecting erythrocyte sedimentation is given by S. Oka.1

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With an Appendix compiled by Syoten Oka. Kyorin University School of Medicine, Mitaka, Tokyo, Japan.