Osmotic deformability of erythrocytes at various shear stresses

Red blood cell (RBC) deformability is greatly affected by the osmolality, and maximum deformability, which is determined as maximal elongation index (EI_max), is usually observed in isotonic conditions at high shear stresses (>20 Pa). Therefore, we examined osmotic RBC deformability over a range of shear stresses (0.5–20 Pa). We found that the RBC deformability at low shear stresses (1–3 Pa) was maximum in hypotonic conditions (225–250 mOsm/kg H₂O), which is slightly lower than the normal range of osmolality in plasma (290–310 mOsm/kg H₂O). The phenomenon that O_max (the osmolality at EI_max) is dependent on applied shear stress could play an important role in microcirculation in which osmolality varies widely.