Distinction of lower esophageal sphincter strength from sphincter competence

Although an absolute correlation has been impossible to demonstrate, it has long been thought that the manometric magnitude of the lower esophageal sphincter pressure was a good index of lower esophageal sphincter strength, and hence its competence. To study this relationship, 12 adult mongrel cats were surgically fitted with gastric cannulas. The cats were studied by six-lumen, radially-oriented, rapid pullback manometry before and after administration of atropine, and before and after daily perfusion of the distal esophagus with 0.1 N hydrochloric acid. Lower esophageal sphincter strength was determined by the lower esophageal sphincter pressure vector cross-sectional area. This was computed by plotting the lower esophageal sphincter pressure on polar coordinates, and finding the area circumscribed by the vectors. Lower esophageal sphincter competence was determined by measurement of both the intragastric volume and intragastric pressure required to produce gross reflux. Atropine significantly decreased the mean lower esophageal sphincter pressure vector cross-sectional area from 7,963 +/- 2,469 mm Hg to 720 +/- 59 mm Hg (p less than 0.05) and decreased the mean lower esophageal sphincter opening pressure from 30.2 +/- 6.9 mm Hg to 13.2 +/- 4.1 mm Hg (p less than 0.05). However, acid perfusion significantly decreased the lower esophageal sphincter pressure vector cross-sectional area from 6,786 +/- 3,334 mm Hg to 715 +/- 720 mm Hg (p less than 0.05). This indicates that the lower esophageal sphincter has two components, one of which is acid-sensitive and both of which are atropine-sensitive.