Augmentation and facilitation of oxygen transfer in flowing hemoglobin solutions

Oxygen transfer was studied in hemoglobin solutions in tube flow at wall shear rates between 200 s-1 and 1000 s-1. Measurements of the bulk oxygen transfer are compared with an analytical model including the effect of the carrier-facilitation of the hemoglobin. Over the range considered this increases the effective diffusion coefficient by almost a factor of three. The addition of hemolyzed red cells, keeping the total hemoglobin concentration constant, provided an additional increase in the effective diffusion coefficient of over 60%. This implies that a sizable increase occurs in the effective diffusion of the hemoglobin molecule, apparently due to the motion of the red cells in the shear field of the fluid. The increase in transport matches well with quantitative estimates of the translational motion of red blood cells.