Interaction of Fluid Movement and Particle Diffusion Across Capillary Walls

The rate of transcapillary exchange of substances delivered to or removed from the tissue by blood depends on the concentration difference across the capillary wall. This concentration difference results in an osmotic effect that can have considerable influence on capillary-tissue fluid exchange. However, fluid exchange also affects the plasma and tissue concentrations of the various substances. Therefore, the determination of substrate concentration profiles involves an interaction of many microcirculatory phenomena, including capillary-tissue fluid exchange. In this paper a general mathematical model is presented that describes the interaction of multiple exchangeable solutes. The resulting equations are solved to give the concentration profiles of different substances and their effect on fluid exchange for various normal and pathological situations of physiological interest.