Segmental response of the lower esophageal sphincter to increased intragastric pressure

An important controversy exists concerning the adaptive capacity of the lower esophageal sphincter (LES) in response to increases in intragastric pressure. This capacity would characterize the LES as a dynamic element in preventing gastroesophageal reflux (GER). This physiological property was studied in 15 male cats using an experimental model in which the gastroesophageal antireflux barrier was generated eyclusively by the intrinsic tone of the LES. Under these conditions, the intragastric pressure (GP) and sphincter pressure (LESP) were measured by electromanometric procedures. When the gastric lumen was perfused with known volumes (25, 50, 75, 100, 125, 150 ml) of saline solution, increases in GP and LESP were observed. Both pressures increased slowly as the gastric volume rose, and when both values were equal, GER appeared. Studying the physiological properties of the LES by direct methods in this model, we conclude that (a) there is segmental pressure response of the LES when faced with direct opening stimulation such as an increase in GP; and (b) the increase in LES resting tone has a linear relation with the increase in GP.