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This study evaluates the effect of intraabdominal pressure increases on lower esophageal sphincter (LES) pressure in normal subjects and in patients with reflux esophagitis. Intraabdominal and intragastric pressure were increased by abdominal compression, the Valsalva maneuver, and leg raising. In normal subjects changes in pressure recorded from the LES equaled the changes in gastric pressure induced by abdominal compression and Valsalva. Consquently the LES-gastric pressure gradient remained unchanged. During leg raising, pressure recorded from the LES increased more than gastric pressure, thereby increasing the LES-gastric pressure gradient. Although statistically significant, the LES pressure increases associated with leg raising were modest, unrelated to initial sphincter pressure, and unaffected by atropine. When individuals demonstrating a "common cavity" phenomenon were exculed, LES pressure changes during abdominal compression were similar in patients with esophagitis and in normal volunteers. Consequently, response of the LES to abdominal compression generally does not separate patients with esophagitis from normal subjects. We believe that the LES responses to increased intra-abdominal pressure observed in this study are better accounted for by mechanical factors than by a physiologic adaptive response of intrinsic LES tone.

A need exists for accurate pressure recording of pharyngeal motor events. Results of this study indicate that accurate quantitation of pharyngeal motor activity is not possible using a water-filled catheter system, even when high infusion rates are used. An intraluminal strain gauge system, however, achieves high-fidelity recording. Quantitation of pharyngeal peristalsis using the intraluminal strain gauge system reveals peristaltic pressure amplitudes higher than those hitherto recorded. In normal subjects, peristaltic amplitude averages about 200 mmHg in the hypopharynx, complexes in one subject being as high as 600 mmHg. A zone of relatively low pressure exists in the oropharynx. Mean pharyngeal wave duration decreases progressively in an aboral direction, from 1.0 to 0.3 s, and peristaltic wave speeds range between 9 and 25 cm/s. Accurate quantitation of pharyngeal peristaltic variables provides the necessary basis for characterization and assessment of pharyngeal motor disorders.

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