Significance of luminal plasma layer resistance in arterial wall oxygen supply

Previous analyses of the arterial wall oxygen supply system have assumed that a cell-free layer of plasma next to the endothelium is the major transport barrier in the lumen. Using a computer simulation, we have quantitatively tested this assumption. Our results show that oxygen diffusion gradients extend significantly into the flowing blood well beyond any plasma layer and that the major luminal transport resistance lies in the flowing blood and not in the plasma layer. The simulation was also employed to compute the effect of a reported 50% drop in plasma oxygen diffusivity. This rather large reduction did significantly lower oxygen levels within the arterial wall tissue. Whether such large reductions in diffusivity ever actually occur in human plasma is a subject of current controversy.