Effects of Small Changes in Capillary Hydrostatic Pressure on Interstitial Fluids Volume and Proteins Amount: a simulation study

Abstract

Capillaries have an important role in exchanging fluids and solute between vessels and organ tissues constantly in animals including humans. In this study, we present a capillary model based on biological knowledge, aiming at investigating mechanisms of movement of fluids and proteins across the capillary membrane. By applying small changes to the capillary hydrostatic pressure, we observed changes in the fluid volume and the protein amount in the interstitial space. After changing the capillary hydrostatic pressure, the interstitial fluid volume deviated from the original level rapidly, changed its direction, and then approached a steady state slowly, while protein approached a steady state gradually. From mathematical analyses applied to the model, we could obtain a phase plane diagram and confirm that movement of fluids was faster than that of proteins. We report quantitative results on the movement of fluids and proteins, which are difficult to observe directly in living organisms.