Effect of peristaltic dysfunction on esophageal volume clearance

We studied clearance of acid from the esophagus and esophageal emptying in normal subjects. A 15-ml bolus of 0.1 N hydrochloric acid (pH 1.2) radiolabeled with [99mTc]sulfur colloid was injected into the esophagus, and the subject swallowed every 30 seconds. Concurrent manometry and radionuclide imaging showed nearly complete emptying of acid from the esophagus by an immediate secondary peristaltic sequence, although esophageal pH did not rise until the first swallow 30 seconds later. Esophageal pH then returned to normal by a series of step increases, each associated with a swallow-induced peristaltic sequence. Saliva stimulation by an oral lozenge shortened the time required for acid clearance, whereas aspiration of saliva from the mouth abolished acid clearance. Saliva stimulation or aspiration did not affect the virtually complete emptying of acid volume by the initial peristaltic sequence. We conclude that esophageal acid clearance normally occurs as a two-step process: (1) Virtually all acid volume is emptied from the esophagus by one or two peristaltic sequences, leaving a minimal residual amount that sustains a low pH, and (2) residual acid is neutralized by swallowed saliva.

Oesophageal acid clearing has been measured by counting the number of swallows needed to raise the lower oesophageal pH from 1.5 to 5.0 after instilling 15 ml 0.1 N hydrochloric acid. Normal subjects all had a result less than 12, as did asymptomatic patients with hiatal hernias. Patients with symptomatic gastrooesophageal reflux tended to have abnormal acid clearance, as did those with oesophageal motility disorders. Acid clearance correlated well with the mean duration of spontaneous episodes of acid reflux during 15-hour continuous recordings of lower oesophageal pH. Abnormal acid clearance was improved by raising the bedhead, by medical treatment for oesophagitis, and by metoclopramide. We conclude that abnormal acid clearing may result from disturbed oesophageal motility and render patients with these disorders susceptible to reflux oesophagitis. However, it also seems that gastrooesophageal reflux may lead to impaired acid clearance, both by creating abnormal motility and by effects on the oesophageal wall, and thus lead to a ;vicious-spiral' oesophagitis. In treating gastrooesophageal reflux, attention must be paid to improving acid clearance.