Intraesophageal pH monitoring

This test uses a probe to detect a low pH (acidity) in the esophagus. The probe is at the end of a very thin tube that is passed through one side of the nose, swallowed and is advanced to a given location in the bottom of the esophagus. The patient then goes home, participates in his or her usual activities, and the number of GE reflux (backwashing of acid into the esophagus) episodes and length of each episode is recorded by the recording device attached to the probe. The patient also keeps a diary of any symptoms and the times that they occur. The probe is usually worn for 18 to 24 hours so that there is adequate opportunity to detect both daytime and nighttime GE reflux episodes.

Interpretation of results
The physician interpreting the test looks at the number of reflux episodes (esophageal pH below 4.0), how long each lasts, the total percentage of time that the patient has a pH below 4.0 and compares the results to normal values. Using the patient diary, patient symptoms are correlated with the reflux episodes detected by the pH probe. The diary is very important in confirming GERD (gastroesophageal reflux disease) as the cause of a patient's symptoms. It is also important in detecting patients who may not have an increased number of reflux episodes but who have symptoms during their episodes of reflux and therefore have symptomatic GERD.

Most of the time this test is used in conjunction with upper endoscopy in the diagnosis of GERD. It is frequently requested as part of the preoperative (before surgery) work-up for anti-reflux surgery to document abnormal acid reflux. It is sometimes used to determine whether a medication is controlling acid. Disadvantages of this test include patient inconvenience, overlap in test results between normal persons and those with real GERD and difficulty standardizing the test from center to center. 

There is now a new tubeless device called the Bravo pH probe. It is about the size of a vitamin and is attached to the lower esophagus with an upper endoscope. The device does not cause pain, does not interfere with the patient's activities, and records the patient's esophageal pH for about 2 days. The information from the probe is sent to a small recording device that is worn by the patient during the first 2 days after the probe is placed in the esophagus. Within 10 days to two weeks the device drops off the esophagus and harmlessly passes out of the body into the feces. Early studies look good for device in its ability to identify those patients who have GERD.