Intrasubject variability of gastric emptying in the critically ill using a stable isotope breath test

Background and aims: Isotope breath tests are increasingly used to evaluate the effects of prokinetic drugs on gastric emptying. The aim was to assess intrasubject variability in gastric emptying, when using an isotope breath test in the critically ill. Methods: A retrospective analysis of data was undertaken in 12 patients who had gastric emptying measurements on consecutive days using a ¹³C-octanoic acid breath test. The gastric emptying coefficient - GEC (a global index for the gastric emptying rate), and the t₅₀ (calculated time for 50% of meal to empty) were calculated, together with the coefficient of variability for these parameters. Data are mean (SD). Results: Neither GEC (day 1: 3.3 (0.8) vs. day 2: 3.1 (0.6); P = 0.31) nor t₅₀ (day 1: 127 (43) min vs. day 2: 141 (48) min; P = 0.46) were significantly different between the two days. Intrasubject variability was less for GEC (15.6%) than for t₅₀ (31.8%). Conclusion: There is only modest intrasubject variability in GEC measurements using the ¹³C-octanoic acid breath test in critically ill patients. As such, it may be an acceptable measurement tool to assess the effects of prokinetic drugs in this group.