The problem of lower esophageal sphincter manometry. An experimental study in vitro

The relation between sphincter pressure recorded by manometry and sphincter function was studied in three different in vitro models of the lower esophageal sphincter (LES). - A LES was simulated on gastroesophageal specimens by application of external pressure (A Starling model - model I), rubber band(s) (model II), or loaded plastic band loop(s) (model III). - Pressure in the simulated sphincters (SP) was recorded by pull-through manometry using either a continuously infused 4.5 mm thick composite catheter with three sidehole channels and a central longer thin endhole channel or a simple thin endhole catheter. SP was recorded with empty stomach (RSP), during gastric filling and at reflux. Gastric pressure at which reflux occurred - opening pressure (OP) - was used as a measure of function of the simulated sphincter. - RSP recorded by the sideholes was the same or higher in model I, higher in model II, and lower in model III than RSP recorded by the endhole. OP was equal to RSP (endhole) in model I but lower than RSP (endhole) in models II and III. External support to the esoPhageal specimen was recorded by the corresponding sidehole as increased pressure. - The models demonstrated a complex relation between recorded SP and OP that, however, could be explained by the different properties of the three models and La Place's law. Both sideholes and endhole seemed to record true pressures but the endhole recorded the pressure in the closed sphincter and was insensitive to pressure asymmetria caused by external support. These studies suggest that RSP recorded by a thin endhole catheter is a direct measure of sphincter strength which we expect determines sphincter function.