INHIBITION OF RESTING LOWER ESOPHAGEAL SPHINCTER PRESSURE BY PHARYNGEAL WATER STIMULATION IN HUMANS

Background/Aims: Normal inhibition of lower esophageal sphincter (LES) tone occurs during swallowing and belching. However, it is known that it may occur independently of these functions. The aim of this study was to characterize the effect of pharyngeal water stimulation on rest ing LES pressure. Methods: The effect of rapid-pulse and slow continuo us intrapharyngeal injection of minute increments of water on the rest ing tone of the upper and LES of 14 healthy young volunteers was evalu ated by concurrent manometry, submental electromyography, and respirog raphy. Results: At a threshold volume, pharyngeal water injection indu ced an isolated LES relaxation in all volunteers. The threshold volume inducing LES relaxation by rapid-pulse injection, 0.16 +/- 0.01 mL, w as significantly lower than that with slow continuous injection (0.5 /- 0.05 mL) (P < 0.05). The duration and magnitude of LES relaxation w ere not volume dependent. The duration of LES relaxation induced by ra pid-pulse injection was significantly longer than that of swallows. Co nclusions: Minute amounts of liquid injected into the pharynx induce L ES relaxation different from that of the normal swallow. Neither the d uration nor the magnitude of this relaxation is volume dependent. Wher eas the contribution of this finding to the mechanism of transient LES relaxation remains to be ascertained, it may partially explain the va riability of the basal LES pressure.