Response of porcine lower esophageal sphincter to increasing intraabdominal pressure.

The response of lower esophageal sphincter pressure to increasing intraabdominal pressure was investigated in six anesthetized pigs while measuring the intraabdominal pressure directly with a perfused catheter and recording continuously from the lower esophageal sphincter using a manometric catheter incorporating a constantly perfused sleeve. Studies were conducted both before and after the administration of intravenous atropine. Resting lower esophageal sphincter pressure was 8 mm Hg (3-19 mm Hg). In response to inflation of the peritoneal cavity with carbon dioxide gas, lower esophageal sphincter pressure rose significantly more than intraabdominal pressure whether the stomach was empty or full. In three of the six pigs, phasic lower esophageal sphincter pressure variations occurred as intraabdominal pressure increased. These variations were unrelated to respiration. Resting lower esophageal sphincter pressure was little affected by 75 micrograms/kg intravenous atropine which also had no effect on the lower esophageal sphincter response to increasing intraabdominal pressure. We conclude that, in the pig, the lower esophageal sphincter pressure increases more than the intraabdominal pressure in response to challenge and that excitatory cholinergic fibers do not mediate this response.