NEAR-WALL EXCESS OF PLATELETS INDUCED BY LATERAL MIGRATION OF ERYTHROCYTES IN FLOWING BLOOD

In this study we present experimental data on the inhomogeneous distri bution of platelets in polyethylene tubes (200 mum diam) based on the inverse Fahraeus effect for platelets. It is shown that platelets are expelled toward the red blood cell-depleted marginal layer near the tu be wall by mutual interaction with erythrocytes. By means of a straigh tforward model, the near-wall concentration of platelets could be esti mated from measurements on the average tubular platelet concentration. The marginal layer originates from the hydrodynamic interaction of th e deformable erythrocytes with the tube wall. If the tube diameter is large compared with the size of the erythrocytes, the lateral migratio n effects can effectively be scaled on the absolute distance between t he erythrocytes and the tube wall. This results in the main conclusion that the near-wall concentration of platelets is significantly enhanc ed up to about seven times the average concentration, practically irre spective of the tube diameter in the range of 100-500 mum. Where compa rable, the results of this study are in accordance with experimental d ata of other authors.