This test evaluates the competence of the lower esophageal sphincter- the major barrier to reflux-by measuring intraesophageal pH with an electrode attached to a manometric catheter.

Purpose

To evaluate competence of the lower esophageal sphincter
To evaluate gastric reflux in patients who complain of persistent heartburn with or without regurgitation

Patient Preparation

Explain to the patient that this test evaluates the function of the sphincter between the esophagus and stomach. Tell him to fast and avoid smoking after midnight before the test.
Describe the test, including who will perform it and where and its duration (about 45 minutes).
Tell him that a tube will be passed through his mouth into his stomach and that he may experience slight discomfort, a desire to cough, or a gagging sensation.
Just before the test, check the patient's pulse rate and blood pressure, and instruct him to void.
Withhold antacids, anticholinergics, cholinergics, adrenergic blockers, alcohol, corticosteroids, cimetidine, and reserpine for 24 hours before the test. If they must be continued, note this on the laboratory slip.

Procedure And Posttest Care

After the patient is placed in the high Fowler position, the catheter with electrode is introduced into his mouth.
The patient is instructed to swallow when the electrode reaches the back of his throat.
Using a manometer, the examiner locates the lower esophageal sphincter. The catheter is raised 3/4"(2 cm). The patient is told to perform Valsalva's maneuver or lift his legs to stimulate reflux. After he does so, intraesophageal pH is measured.
If the pH is normal, the catheter is passed into the patient's stomach. A prescribed acid solution is instilled over 3 minutes. Then the catheter is raised 3/4" above the sphincter. Again, the patient is asked to perform Valsalva's maneuver or lift his legs and intraesophageal pH is measured.
After the test, tell the patient he may resume his usual diet and restart any medications withheld for the test.
Provide lozenges if the patient complains of a sore throat

Precautions

During insertion, the electrode may enter the trachea instead of the esophagus. If the patient develops cyanosis or paroxysms of coughing, move the electrode immediately.
Observe the patient closely during intubation because arrhythmias may develop.
Clamp the catheter before removing it to prevent aspiration of fluid into the lungs.

Reference values

The pH of the esophagus normally exceeds 5.0.

Abnormal Findings

An intraesophageal pH of 1.5 to 2 indicates gastric acid reflux resulting from incompetence of the lower esophageal sphincter. Persistent reflux leads to chronic reflux esophagitis. Additional studies, such as barium swallow and esophagogastroduodenoscopy, are necessary to diagnose and determine the extent of esophagitis.

Interfering Factors

Failure to adhere to pretest restrictions
Antacids, anticholinergics, and cimetidine (possible lowering of intraesophageal pH because of decrease in gastric secretions or acidity)
Alcohol, cholinergics, reserpine, adrenergic blockers, and corticosteroids (possible elevation of intraesophageal pH because of reflux from a relaxed lower esophageal sphincter or an increase in gastric secretions)

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