The commonly accepted model for gastric emptying suggests that the 'antral mill' is responsible for the triturition and subsequent emptying of solid food from the stomach. Little is known about the contribution to solid emptying made by other digestive mechanisms such as acid-pepsin secretion. We have investigated the effect of inhibiting gastic secretion on the rate at which a solid test meal emptied from the stomach. Using a radiolabelled beefburger, we performed paired gammacamera studies on consecutive days in 10 fasted, healthy volunteers to compare gastric emptying of the test meal with and without oral cimetidine (400 mg 1 hour before the test, 800 mg at the start of the meal). Inhibition of acid-pepsin secretion by cimetidine was associated with an appreciable delay in the rate of emptying of the burger from the stomach (Tso cimetidine 187 (16) Studies carried out in dogs and humans suggest that digestible solids must be reduced to particles less than 1 mm in diameter before they will empty from the stomach.'2 This process of triturition is usually ascribed to the mechanical action of the 'antral mill,' although it is possible that acid and pepsin in gastric secretions also help to fragment solid food particles by breaking down connective tissue proteins. The H2 receptor antagonist cimetidine inhibits gastric acid and pepsin secretion-5 and might therefore affect gastric emptying of digestible solids by delaying disruption of large fragments of chewed food into a fine particulate suspension. To test the hypothesis that gastric secretions have a physiological role in the breakdown and emptying of solid food, we have measured the rate at which a radiolabelled beefburger emptied from the stomach before and after acid secretion had been blocked by cimetidine. MethodsStudies were carried out in 10 healthy volunteers (five men, five women) aged 18-34 years, each of whom had given written informed consent. This study received approval from the local Sheffield Hospitals Ethical Sub-committee.Paired gastric emptying studies, one with cimetidine and one without, were performed in a random order on consecutive days in semirecumbent, fasted subjects using a gammacamera (Model 1201 Pho-gamma III, NuclearChicago, Europa NV, Amsterdam, The Netherlands) positioned anteriorly over the abdomen. The oral dose of cimetidine (Tagamet, Smith Kline and French, Philadelphia PA, USA) used to suppress acid secretion was 1 -2 g (400 mg given one hour before the study and 800 mg with the meal, to ensure that reduced gastric secretion was maintained throughout the study). In an attempt to standardise the size of swallowed food particles subjects were fed 1 cm cubes of radiolabelled beefburger over a five minute period.
Applied potential tomography is a new, non-invasive technique that yields sequential images of the resistivity of gastric contents after subjects have ingested a liquid or semi-solid meal. This study validates the technique as a means of measuring gastric emptying. Experiments in vitro showed an excellent correlation between measurements of resistivity and either the square of the radius of a glass rod or the volume of water in a spherical balloon when both were placed in an oval tank containing saline. Altering the lateral position of the rod in the tank did not alter the values obtained. Images of abdominal resistivity were also directly correlated with the volume of air in a gastric balloon. Profiles of gastric emptying of liquid meals obtained using APT were very similar to those obtained using scintigraphy or dye dilution techniques provided that acid secretion was inhibited by cimetidine. Profiles of emptying of a mashed potato meal using APT were also very similar to those obtained by scintigraphy. Measurements of the emptying of a liquid meal from the stomach were reproducible if acid secretion was inhibited by cimetidine. Thus, APT is an accurate and reproducible method of measuring gastric emptying of liquids and particulate food. It is inexpensive, well tolerated, easy to use and ideally suited for multiple studies in patients, even those who are pregnant. A preliminary study is also presented that assesses the technique as a means of measuring gastric acid secretion. Comparison of resistivity changes with measured acid secretion following the injection of pentagastrin shows good correlations. APT might offer a non-invasive alternative to the use of a nasogastric tube and acid collection.
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