Effect of permeability and wall properties on peristaltic transport of chyme in the colon

Permeability of colon wall characterizes the intestinal barrier functional properties. Despite a number of assays to measure and evaluate an intestinal permeability, additional research is nec-essary for clinical use. Due to a lack of standardization and complexity of current methodologies, the results are sometimes not very reliable. Mathematical modeling and numerical simulation may overcome such problems in the intestinal permeability diagnostics. As a first step it is necessary to develop a theoretical model for peristaltic chyme transport in the colon with permeable wall. A transient 2-D FSI simulation of chyme considered as a non-Newtonian fluid and permeable colon wall has been performed. Darcy's law was adopted to simulate fluid absorption in the intestinal wall. Sisco model was used to model the chyme rheology. Chyme flow velocity was obtained as functions of the amplitude and velocity of the peristaltic wave. As the lumen decreases, a region is formed in the fluid domain where velocity increases to maximum value uf = 0,2 cm/s. The distribu-tion of absorption rates in the walls of the colon was obtained in terms of the peristaltic wave parameters. The maximum absorption velocity of particles in the porous domain was 0,08 cm/s (with particles moving in the fluid domain with a maximum velocity of 0,2 cm/s). An increase of wave propagation in two times leads to a change in Darcy's pressure by 2,5 times. Application of the coupled model of fluid-structure interaction and permeability in the colon allows to combine three physical phenomena: the flow of chyme (liquid), the interaction between liquid and solid, and absorption due to permeability. The influence of wave amplitude is predicted to be stronger than the influence of propagating wave speed.