Characteristics of lower esophageal sphincter relaxation induced by pharyngeal stimulation with minute amounts of water

Background & Aims: Injection of minute amounts of water in the pharynx leads to a long-duration lower esophageal sphincter (LES) relaxation that is an important feature of a transient LES relaxation. The aims of this study were to determine if a pharyngeal stimulus-induced LES relaxation is associated with crural diaphragm inhibition, esophageal common cavity, and acid reflux in normal subjects. Methods: Esophageal and LES pressure, crural diaphragm electromyographs, and pH were recorded in the fasting and postprandial states in normal subjects. The pharynx was stimulated by injection of water at bolus volumes of 0.05 and 0.1 mL and then in 0.1-mL increments. Results: Pharyngeal stimulation induced a long-duration LES relaxation in the absence of swallow and esophageal peristalsis. In the fasting state, none of the LES relaxations induced by pharyngeal stimulation were associated with inhibition of crural diaphragm, esophageal common cavity, and acid reflux. In the postprandial periods, only 8% of the pharyngeal stimuli resulted in crural diaphragm inhibition and esophageal common cavity. Esophageal reflux was found only at the times of simultaneous LES and crural diaphragm relaxation. Conclusions: Stimulation of the pharynx has different effects on the LES and crural diaphragm. Relaxation of crural diaphragm along with LES relaxation is essential for the occurrence of gastroesophageal reflux in normal subjects.