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

BACKGROUND: Cigarette 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. METHODS: The (13)C-octanoic acid breath test was performed in eight male habitual smokers on two randomized occasions (either sham smoking or actively smoking). The time vs (13)CO(2) excretion rate curve was mathematically fitted to a conventional formula of y (t) = m*k*beta*e(-k*t)*(1 - e(-k*t))(beta-1), and the parameters of k and beta were determined: under the crossover protocol, a larger (smaller) beta indicates slower (faster) emptying in the early phase, and a larger (smaller) k indicates faster (slower) emptying in the later phase. The half (13)CO(2) excretion time (t(1/2b) = -[ln(1 - 2(-1/beta))]/k) and the time of maximal (13)CO(2) excretion rate (t(max) = [lnbeta]/k) were also calculated. Between the two occasions, k, beta, t(1/2b), and t(max) were compared by the Wilcoxon signed-rank test. RESULTS: After smoking, k was significantly increased. No significant differences were found in beta, t(1/2), and t(max) between the two occasions. CONCLUSIONS: The 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.

[The validity of serum acetaminophen concentration at 45 min as an index of gastric emptying rate: a study based on pharmacokinetic theories].

The reliability of the serum acetaminophen (APAP) concentration at 45 min (C45) as a measure of gastric emptying (GE) has been evaluated using a pharmacokinetic simulation work. The present results have revealed that C45 is a useful index to conveniently detect delayed GE, but it is unreliable to measure rapid GE. In addition, the following simple criteria for diagnosis of delayed GE has been proposed based on the pharmacokinetic theories: after ingestion of 20 mg/kg APAP dissolved in a 200 kcal-containing liquid meal, 1) the delayed GE is excluded when C45 > 5.0 micrograms/ml, 2) whether GE is delayed or not is inconclusive when 2.0 < C45 < 5.0 micrograms/ml, and 3) the delayed GE is confirmed when C45 < 2.0 micrograms/ml.

The Wagner-Nelson method can generate an accurate gastric emptying flow curve from CO2 data obtained by a 13C-labeled substrate breath test.

BACKGROUND: In pharmacokinetics, the Wagner-Nelson (W-N) method can accurately estimate the rate of drug absorption from its urinary elimination rate. A stable isotope (13C) breath test attempts to estimate the rate of absorption of 13C, as an index of gastric emptying rate, from the rate of pulmonary elimination of 13CO2. The time-gastric emptying curve determined by the breath test is quite different from that determined by scintigraphy or ultrasonography. In this report, we have shown that the W-N method can adjust the difference. METHODS: The W-N equation to estimate gastric emptying from breath data is as follows: the fractional cumulative amount of gastric contents emptied by time t = Abreath (t)/Abreath (infinity) + (1/0.65).d[Abreath (t)/Abreath (infinity) ]/dt, where Abreath (t) = the cumulative recovery of 13CO2 in breath by time t and Abreath ( infinity ) = the ultimate cumulative 13CO2 recovery. The emptying flow curve generated by ultrasonography was compared with that generated by the W-N method-adjusted breath test in 6 volunteers. RESULTS: The emptying curves by the W-N method were almost identical to those by ultrasound. CONCLUSIONS: The W-N method can generate an accurate emptying flow curve from 13CO2 data, and it can adjust the difference between ultrasonography and the breath test.