Performance of the [C-13]-acetate gastric emptying breath test during physical exercise

Background The gastric emptying rate of liquids can be determined non-invas ively using the [C-13]-acetate breath test at rest. The aims of our study w ere to validate this test during physical exercise against the double-sampl ing method and to evaluate the time needed for intestinal absorption and th e delay between absorption and appearance of (CO2)-C-13 in breath, both at rest and during exercise. Design Fifteen well-trained male subjects were investigated. Gastric emptyi ng was determined simultaneously measuring the (CO2)-C-13 breath enrichment after intragastsic administration of 0.5 L of carbohydrate solution with 1 50 mg of [C-13]-acetate added and by the double-sampling technique (n = 9). In separate tests, 150 mg of [C-13]-acetate was also applied intraduodenal ly and intravenously (n = 6), both at rest and during exercise. Time-to-pea k (TTP) (CO2)-C-13 enrichment was determined using a curve fit and was cons idered as the parameter for gastric emptying. Results TTP enrichment derived from the breath test significantly correlate d with the gastric emptying half-time obtained from the gastric aspirates. During exercise, median TTP enrichment values after intragastric, intraduod enal (i.d.) and intravenous (i.v.) administration of [C-13]-acetate were 22 .3, 10.3 and 5.4 min respectively. During exercise, i.d. and i.v. values we re reached significantly earlier than at rest. Conclusion The [C-13]-acetate breath test can be used as a non-invasive met hod to determine relative gastric emptying rates of liquids during exercise , but the results are influenced by the rate of absorption and the time nee ded for subsequent oxidation of [C-13]-acetate and exhalatian of (CO2)-C-13 .