This paper started many years ago when Steve Wank, of the Digestive Diseases Branch of NIDDK, had this idea to use this new wireless PH detecting SmartPill that you could swallow to determine how much acid your stomach was producing. There really was no noninvasive way to monitor how well medications would work for certain reflux diseases. What he wanted was a model of gastric acid secretion output based on the dynamics of PH when a buffer was added to design a protocol for the experiment. I came up with a simple mass-action model of acid buffering and made some graphs for him. We then tested the model out in a beaker. He thought the model worked better than I did but it was somewhat useful to him in designing the experiment.
BACKGROUND:Gastro-oesophageal reflux disease (GERD) and gastric acid hypersecretion respond well to suppression of gastric acid secretion. However, clinical management and research in diseases of acid secretion have been hindered by the lack of a non-invasive, accurate and reproducible tool to measure gastric acid output (GAO). Thus, symptoms or, in refractory cases, invasive testing may guide acid suppression therapy.
AIM:To present and validate a novel, non-invasive method of GAO analysis in healthy subjects using a wireless pH sensor, SmartPill (SP) (SmartPill Corporation, Buffalo, NY, USA).
METHODS:Twenty healthy subjects underwent conventional GAO studies with a nasogastric tube. Variables impacting liquid meal-stimulated GAO analysis were assessed by modelling and in vitro verification. Buffering capacity of Ensure Plus was empirically determined. SP GAO was calculated using the rate of acidification of the Ensure Plus meal. Gastric emptying scintigraphy and GAO studies with radiolabelled Ensure Plus and SP assessed emptying time, acidification rate and mixing. Twelve subjects had a second SP GAO study to assess reproducibility.
RESULTS:Meal-stimulated SP GAO analysis was dependent on acid secretion rate and meal-buffering capacity, but not on gastric emptying time. On repeated studies, SP GAO strongly correlated with conventional basal acid output (BAO) (r = 0.51, P = 0.02), maximal acid output (MAO) (r = 0.72, P = 0.0004) and peak acid output (PAO) (r = 0.60, P = 0.006). The SP sampled the stomach well during meal acidification.
CONCLUSIONS:SP GAO analysis is a non-invasive, accurate and reproducible method for the quantitative measurement of GAO in healthy subjects. SP GAO analysis could facilitate research and clinical management of GERD and other disorders of gastric acid secretion.