Importance of convection to the enhancement of erythrocyte sedimentation rates in inclined tubes

Abstract

Erythrocytes were settled from whole blood in standard 200 × 2.5 mm erythrocyte settling rate tubes placed vertically and at various angles from 85° to 15° from the horizontal. In all cases sedimentation rates measured along the slope increased with decreasing angle from the horizontal. Vertical settled distances rapidly increased down to an angle of 70° and then changed very little even down to angles as shallow as 30°. Evidence is presented that convection plays a significant role in the inclined settling of erythrocytes, as has already been demonstrated with clay, or glass bead suspensions in water. Inclined settling enhancements obtained are quite similar to those observed under similar conditions with yeast cells in aqueous glucose.