INTESTINAL GAS-DYNAMICS AND TOLERANCE IN HUMANS

Background & Aims: Abdominal symptoms are often attributed to intestin al gas. In humans, gas production and composition have been previously investigated, but intestinal gas dynamics and tolerance remain virtua lly unknown. The aim of this study was to establish the relationship b etween intestinal gas loads, evacuation, perception of symptoms, and o bjective abdominal distention in healthy humans. Methods: A dose-respo nse study was performed in 46 healthy subjects; intestinal gas was inf used for 3 hours (0, 1, 4, 12, and 30 mL/min), and anal gas evacuation , symptom perception, and abdominal distention were measured, A mixtur e of gases was infused in venous proportions to minimize diffusion. An al gas recovery and calculations of gas retention were validated using sulfur hexafluoride as a nonabsorbable gaseous marker, Results: At al l of the infusion rates, gas evacuation rapidly equilibrated and paral leled gas infusion without significant differences in perception. Only 6 subjects retained >400 mt gas, and 5 of them developed abdominal di stention and symptoms, By contrast, all but 4 of the 41 subjects witho ut retention tolerated the gas loads without discomfort, Conclusions: Intestinal gas tolerance is normally high, because expeditious gas tra nsit and evacuation prevent gas pooling and symptoms. When this protec tive mechanism is insufficient, gas retention occurs, and it causes ab dominal symptoms and distention.