Differential effect of long-term esophageal acid exposure on mechanosensitivity and chemosensitivity in humans

Background & Aims: Chronic tissue injury in the esophagus associated with gastroesophageal reflux disease may result in sensitization of afferent pathways mediating mechanosensitivity and chemosensitivity. The aim of this study was to evaluate the sensitivity to intraluminal acid and to distention of the esophagus in patients with mild-to-moderate gastroesophageal reflux disease. Methods: Perceptual responses to intraluminal acid perfusion and to esophageal distention and pressure volume relationships were evaluated in 10 healthy volunteers and in 11 patients. Mechanosensitivity was evaluated with a barostat using unbiased distention protocols and verbal descriptor ratings of sensations. Chemosensitivity to acid was determined at baseline and after a 1-month treatment of acid suppression. Results: Patients showed enhanced perception of acid perfusion but not of esophageal distension. Chemosensitivity but not mechanosensitivity was correlated with reflux symptoms and with the degree of endoscopical ly shown tissue injury at baseline. Tissue injury was not associated with altered compliance. Conclusions: Mild-to-moderate chronic tissue injury in gastroesophageal reflux disease differentially affects mechanosensitive and chemosensitive afferent pathways. Chronic acid reflux by itself is not likely to play a role in reported esophageal hypersensitivity to distention in patients with noncardiac chest pain.