title: Performance of the [13C]-acetate gastric emptying breath test during physical exercise.
abstract: BACKGROUND
  The gastric emptying rate of liquids can be determined non-invasively using the [13C]-acetate breath test at rest. The aims of our study were to validate this test during physical exercise against the double-sampling method and to evaluate the time needed for intestinal absorption and the delay between absorption and appearance of 13CO2 in breath, both at rest and during exercise.
  
  
  METHODS
  Fifteen well-trained male subjects were investigated. Gastric emptying was determined simultaneously measuring the 13CO2 breath enrichment after intragastric administration of 0.5 L of carbohydrate solution with 150 mg of [13C]-acetate added and by the double-sampling technique (n = 9). In separate tests, 150 mg of [13C]-acetate was also applied intraduodenally and intravenously (n = 6), both at rest and during exercise. Time-to-peak (TTP) 13CO2 enrichment was determined using a curve fit and was considered as the parameter for gastric emptying.
  
  
  RESULTS
  TTP enrichment derived from the breath test significantly correlated with the gastric emptying half-time obtained from the gastric aspirates. During exercise, median TTP enrichment values after intragastric, intraduodenal (i.d.) and intravenous (i.v.) administration of [13C]-acetate were 22.3, 10.3 and 5.4 min respectively. During exercise, i.d. and i.v. values were reached significantly earlier than at rest.
  
  
  CONCLUSIONS
  The [13C]-acetate breath test can be used as a non-invasive method to determine relative gastric emptying rates of liquids during exercise, but the results are influenced by the rate of absorption and the time needed for subsequent oxidation of [13C]-acetate and exhalation of 13CO2.
authors.affiliation: Maastricht University, the Netherlands. M. vanNieuwenhoven@HB.UNIMAAS.nl
authors.forename: M A
authors.initials: MA
authors.lastname: van Nieuwenhoven
authors.forename: A J
authors.initials: AJ
authors.lastname: Wagenmakers
authors.forename: J M
authors.initials: JM
authors.lastname: Senden
authors.forename: F
authors.initials: F
authors.lastname: Brouns
authors.forename: R J
authors.initials: RJ
authors.lastname: Brummer
mesh_terms: D000085:Acetates / Q000008:administration & dosage / Q000378:metabolism*; D000284:Administration, Oral; D000328:Adult; D001944:Breath Tests; D002247:Carbon Isotopes; D015444:Exercise; D005080:Exercise Test; D005746:Gastric Emptying; D006801:Humans; D007275:Injections, Intravenous; D008297:Male; D005082:Physical Exertion / Q000502:physiology*; D010809:Physical Fitness; D015203:Reproducibility of Results; D012146:Rest
chemical_list: D000085:Acetates; D002247:Carbon Isotopes