Response of lower esophageal sphincter to alterations of intraabdominal pressure.

It is well documented that lower esophageal sphincter pressure increases significantly in response to increases in intraabdominal pressure in order to maintain the gastroesophageal barrier. The mechanism by which this response is elicited is controversial. It has been suggested that the response of the sphincter persists after the intraabdominal pressure stimulus is removed. The present study sought to define the response of the sphincter to increased intraabdominal pressure (achieved by straight leg raising) by continuously monitoring it with the Dent sleeve in a group of 10 normal volunteers. A reproducible pressure profile was observed in both the sphincter and the stomach, characterized by an initial peak, a sustained plateau, and a second peak. The pressure profiles of the stomach and the sphincter were closely approximated and peak and plateau pressures for both did not differ significantly. The onset and offset of the pressure increase were simultaneous in the stomach and the sphincter. No significant changes in sphincter pressure were noted when the rapid pull-through technique was used. This study defines the pressure profiles of the stomach and the lower esophageal sphincter zone during increased intraabdominal pressure in man. Our data suggest that the response of the sphincter is passively mediated.