Influence of tissue metabolism and capillary oxygen supply on arteriolar oxygen transport: a computational model

摘要

We present a theoretical model for steady-state radial and longitudinal oxygen transport in arterioles containing flowing blood (plasma and red blood cells) and surrounded by living tissue. This model combines a detailed description of convective and diffusive oxygen transport inside the arteriole with a novel boundary condition at the arteriolar lumen surface, and the results provide new mass transfer coefficients for computing arteriolar O2 losses based on far-field tissue O2 tension and in the presence of spatially distributed capillaries. A numerical procedure is introduced for calculating O2 diffusion from an arteriole to a continuous capillary-tissue matrix immediately adjacent to the arteriole. The tissue O2 consumption rate is assumed to be constant and capillaries act as either O2 sources or sinks depending on the local O2 environment. Using the model, O2 saturation (SO2) and tension (PO2) are determined for the intraluminal region of the arteriole, as well as for the extraluminal region in the neighbouring tissue. Our model gives results that are consistent with available experimental data and previous intraluminal transport models, including appreciable radial decreases in intraluminal PO2 for all vessel diameters considered (12–100µm) and slower longitudinal decreases in PO2 for larger vessels than for smaller ones, and predicts substantially less diffusion of O2 from arteriolar blood than do models with PO2 specified at the edge of the lumen. The dependence of the new mass transfer coefficients on vessel diameter, SO2 and far-field PO2 is calculated allowing their application to a wide range of physiological situations. This novel arteriolar O2 transport model will be a vital component of future integrated models of microvascular regulation of O₂ supply to capillary beds and the tissue regions they support.