Tomotaka Kawakami

Effect of cigarette smoking on gastric emptying of solids in Japanese smokers: a crossover study using the 13C-octanoic acid breath test

BackgroundCigarette smoking is associated with an increased risk of peptic ulcer and gastroesophageal reflux disease. Gastric emptying disorders may play a role in the development of these upper gastrointestinal diseases. Thus, studies examining a link between smoking and gastric emptying disorders have clinical relevance. This study was conducted to investigate the effect of smoking on gastric emptying of solids in Japanese smokers.MethodsThe 13C-octanoic acid breath test was performed in eight male habitual smokers on two randomized occasions (either sham smoking or actively smoking). The time vs 13CO2 excretion rate curve was mathematically fitted to a conventional formula of y (t) = m*k*β*e−k*t*(1 − e−k*t)β−1, and the parameters of k and β were determined: under the crossover protocol, a larger (smaller) β indicates slower (faster) emptying in the early phase, and a larger (smaller) k indicates faster (slower) emptying in the later phase. The half 13CO2 excretion time (t1/2b = −[ln(1 − 2−1/β)]/k) and the time of maximal 13CO2 excretion rate (tmax = [lnβ]/k) were also calculated. Between the two occasions, k, β, t1/2b, and tmax were compared by the Wilcoxon signed-rank test.ResultsAfter smoking, k was significantly increased. No significant differences were found in β, t1/2, and tmax between the two occasions.ConclusionsThe increase in k suggests the acceleration of gastric emptying in the later phase. For the first time, this study has revealed that acute smoking speeds the gastric emptying of solids in Japanese habitual smokers.

Modified 13C-octanoate breath test and impact of sampling points.

In recent years, the 13C-octanoate breath test has attracted attention as a simple and noninvasive method of assessing gastric emptying of solids. However, practical procedures for test meals, parameters used, and sampling points have not yet been established. Moving toward a more convenient method, here we examined the influences of sampling interval and duration on the 13C-octanoate breath test performed on 15 healthy subjects using a commercially-available instant cupcake. Breath samples were obtained every 15 minutes within 4 hours, and every 30 minutes in the subsequent 2 hours. Using computer simulation, the time it took for the fitting curve to peak (Tpeak) was calculated in each setting with each interval (15, 30, 60, and 120 minutes) and test duration (3, 4, 5, and 6 hours). When the sampling interval widened over 30 minutes, the difference from the original 6-hour data became larger than 20% of the coefficient of variance. When the sampling duration was shortened to 3 hours, no appropriate fitting curve could be achieved. These results suggest that a sampling duration of 4 hours at 30-minute intervals seems to be suitable for practical use of the test.