Evaluation of the fluid-movement contribution to the oxygen transport in tissue

Abstract

The model of diffusive O2 transport from capillary to tissue was established by Krogh a century ago. This model is incomplete as it ignores the often inevitable convective O2 transport via fluid movement. Here, we propose a one-dimensional physical-phenomenological model to evaluate the contribution of fluid movement to the O2 transport in tissue. Both the O2 gradient and the total O2 flux are found to be sensitive to the fluid movement. For small flow rates with a Peclet number Pe < 1, a critical flow rate, udc, is introduced to characterize the contribution of fluid movement to the O2 transport, as well as to evaluate the fluid contribution in O2-deficient tissues and the cytoplasm movement inside muscle fibers. During hemostasis, the O2 flux contributed by the interstitial flow even below a rate of 2 m/s, although negligible near the capillary, can be significant for the tissue residing far from the capillary. For an isolated intramyocyte mitochondrion, the cytoplasm movement can play a key role in the O2 transport. These considerations point to the scenario of an external force to drive the fluid movement leading to an accelerated O2 transport to sustain the mitochondrial consumption. Our model offers a comprehensive picture of the O2 transport in tissue by including both the concentration gradient and the hydraulic pressure gradient. It predicts that even with a small external force, damaged tissues with higher permeability can yield larger rates of interstitial flow promoting O2 transport for tissue recovery. HighlightsO_LIThe fluid movement can play a significant role in O2 transport in tissue with high Prandtl number{nu} /D ~ 103; C_LIO_LIA critical flow rate, udc, is introduced to evaluate the convective transport flux by the fluid in tissue for Pe < 1. C_LIO_LIO2 transport in tissue is a result of the balance between hydraulic pressure gradient induced flux and concentration gradient induced flux. C_LIO_LIOur model indicates more O2 pumped by convective transport into the O2 -deficient region where the O2 diffusive flux cannot penetrate. C_LIO_LIThe cytoplasm movement can excite more O2 flux to the mitochondria with higher myoglobin concentration. C_LI