MODELING AND SIMULATION OF PERISTALTIC TRANSPORT AND MIXING IN THE HUMAN GASTROINTESTINAL TRACT

摘要

Despite active research, the mechanism by which food is transported, mixed and absorbed in the human gastro-intestinal tract remains poorly understood. At the University of Iowa Veterans Hospital, clinicians have been treating veterans for abnormal mechanical activity of the stomach and intestine and are pursuing research into such mechanisms, in order to better control and treat such ailments. The pathology experienced by these patients tends to be chronic and somewhat refractory to treatment particularly in the elderly, those with diabetes or after abdominal operations. Abnormal activity is responsible for gastro-esophageal reflux, gastroparesis, diarrhea, and abdominal pain syndromes. Current techniques of imaging and of image analysis should steadily improve ability to obtain information on mechanical activity of stomach and intestines in patients. Yet, for these imaging techniques to provide optimal diagnostic information, one needs to understand, in depth, how the visual parameters of contractions relate to digestion and absorption of nutrients. A key aspect of this improved physical understanding relates to the fluid mechanics of peristaltic transport, which is the major mechanism by which multiphase mixtures (chyme, bile, food particles, waste, nutrients such as proteins etc.) are transported in the human system. Peristalsis involves the periodic squeezing of materials in the entire digestive system (from the oesophagus to the stomach to the large and small intestines) by the active motion of the walls of the tract, as shown in Figure 1. This is a very effective mechanism that has been adopted by the human system and can transport material highly efficiently for decades with minimal wear. We present a mathematical model to fully understand the mechanisms by which peristalsis effects transport in the ileum and quantify the efficiency aspects of transport, mixing and absorption as a function of the peristaltic wave characteristics.