A theoretical analysis of nonsteady-state oxygen transfer in layers of hemoglobin solution

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.

Diffusion coefficients of oxygen and hemoglobin as obtained simultaneously from photometric determination of the oxygenation of layers of hemoglobin solutions

The oxygenation of layers of deoxygenated hemoglobin solutions after a sudden exposure to a gas containing oxygen at a partial pressure P1 has been studied by a photometric method. Layer thicknesses varied between 50 and 250 micron, hemoglobin concentrations between 0.1 and 0.34kg/l, and oxygen partial pressures between 4.65 and 93.1 kPa (35 and 700 mmHg). The diffusion chamber containing the layer of hemoglobin solution permitted a step change in gas atmosphere without changing the optical apparatus constant. The following results were obtained: 1. The oxygen saturation increase is independent of the layer thickness when expressed as a function of time divided by layer thickness squared (normalized oxygenation time). This justifies the assumption of chemical equilibrium between oxygen and hemoglobin in the range considered. 2. The oxygen saturation increases proportionally to the square root of time over a wide range of oxygenation as expected. This range reaches to almost 100% oxygenation at P1=93.1kPa (700mmHg) but less far as P1 is lower. Thus at high P1 values there is a sharp boundary between the oxygenated and deoxygenated part of the layer allowing the application of the advancing front concept. 3. Fitting the theoretical equations derived in a preceding paper to the experimental results provides simultaneous values of the oxygen permeability (or, knowing oxygen solubility, of the oxygen diffusion coefficient) and of the hemoglobin diffusion coefficient. These values agree fairly well with values obtained by other authors from experiments yielding the diffusion coefficients of oxygen or hemoglobin separately.