Effect of lower esophageal sphincter distension and acidification on esophageal pressure and electromyographic activity: The identification of the ``sphinctero-esophageal excitatory reflex{''

Background. The mechanism of esophageal acid clearance through augmenting esophageal peristalsis in response to gastroesophageal reflux (GER) is not exactly known. We investigated the hypothesis that lower esophageal sphincter (LES) dilatation rather than the refluxed acid affected reflex increase in the esophageal peristaltic activity aiming at clearing the esophagus of the refluxed acid. Methods. The esophageal pressure and electromyographic (EMG) activity response to esophageal sphincter balloon distension in increments of 2 mL of saline was recorded in 17 healthy volunteers (10 men, 7 women, mean age 43.6 11.2 years). The test was repeated in 10 of 17 volunteers while the esophageal sphincter was being anesthetized. The response of the esophageal pressure and electromyographic activity to lower esophageal acidification was also tested. Results. Lower esophageal sphincter balloon distension with 2 mL of saline produced esophageal pressure increase to a mean of 34.2 5.3 cm H2O (P < 0.001). Increase of the balloon distending volume produced results similar to the 2-mL distension (p > 0.05). The esophageal electrical activity increased on esophageal balloon distension; the increase was similar with distensions of 2 mL up to 10 mL. There was no esophageal pressure or electrical activity response to distension of the anesthetized lower esophageal sphincter or to lower esophageal sphincter acidification. Conclusions. During gastroesophageal reflux episodes, the lower esophageal sphincter dilatation and not acidification appears to initiate increased esophageal peristalsis, which clears the esophagus of the refluxed acid. The increased esophageal peristalsis on lower esophageal sphincter dilatation is suggested to be reflex in nature and is mediated through the ``sphincteroesophageal excitatory reflex.{''} This reflex may be of diagnostic significance in esophageal motility disorders; however, this point needs further studies. (c) 2005 by The Society of Thoracic Surgeons.