Osmolality- and hematocrit- mediated flow behavior of RBC suspensions in 33 μ m ID tubes

Abstract

The effects of suspending medium osmolality (166 to 736 mosm/kg) on relative viscosity (η _r) and tube hematocrit (H_T) measured in 33 diameter tubes were studied for 40, 47 and 57% feed hematocrit (H_Fk) suspensions of human RBC in buffer. At all feed hematocrits, η _r increased sharply for the hypertonic media, but was essentially insensitive to hypotonicity. H_T/H_F was less affected by osmolality (13% change over the entire range of osmolality and feed hematocrit). Viscosities could not be calculated from the experimental H_T values. However, η _r could be predicted from RBC number concentration and the tube diameter/RBC volume ratio via a semi-empirical model. RBC transport efficiency depended on both feed hematocrit and osmolality, and was maximal at or near isotonic conditions. Our results appear applicable to non-isotonic regions of the microcirculation, and to estimation of flow resistance for RBC with abnormal cellular mechanical properties.