Oxygen diffusion within arterioles and venules

Oxygen transfer was studied within the arterioles and venules (40 to 100 μm in diameter) of a hamster cheek pouch retractor muscle. Previously obtained transluminal oxygen saturation, red blood cell velocity, and hemoglobin concentration were used for the analysis. Because of branching and transfer to the tissue, the measured oxygen profiles across the vessels were nonuniform. At each axial location, the profiles were converted to radial distributions using a convolution algorithm. The results were modeled using a numerical solution of the convective mass transport equation assuming the blood to be a homogenous mixture. Effective diffusion coefficients were found by matching the axial development of the radial oxygen distribution predicted by the analytical model with the experimental data. The resulting oxygen diffusion coefficients were an order of magnitude higher than have been measured in vitro. This appears to support other evidence relating to the higher than expected oxygen transport in the microcirculation.