Pharyngeal/upper esophageal sphincter pressure dynamics in humans. Effects of pharmacologic agents and thermal stimulation.

Extensive physiological studies of swallowing have been carried out in laboratory animals; however, similar studies in humans have been limited by available technology. In this study we describe the use of a solid-state circumferential sphincter transducer to define manometric characteristics of the human pharynx and upper esophageal sphincter (UES). Effects of pharmacologic agents and thermal stimulation are also described. We studied nine normal volunteers on three separate days. All studies were done in the upright position and consisted of a station pull-through of the UES and six wet swallows with the sphincter transducer in the most proximal segment of the UES and a posteriorly oriented single transducer 5 cm proximal in the pharynx. Baseline studies preceded all drug studies. Effects of bethanechol were studied on day 1, cold stimulation and benzonatate on day 2, edrophonium and atropine on day 3. The UES resting pressure showed large intrasubject day-to-day variations; however, mean values did not differ. There were no effects on UES relaxation or swallow coordination with any of the pharmacologic agents, although benzonatate produced multiple pharyngeal contractions.