Diagnostics: Esophageal Impedance or pH Probe

An esophageal dual pH probe test is a diagnostic procedure used to measure the frequency and severity of acid reflux in the esophagus. During the test, a thin tube with sensors is inserted through the nose or mouth and down into the esophagus. The sensors at two different points along the tube measure the pH levels of the acid in the esophagus over a time period—usually 24 hours. This test helps to determine the frequency and duration of acid reflux episodes, providing valuable information for diagnosing conditions such as gastroesophageal reflux disease (GERD).

An esophageal impedance study is similar to a pH probe study but differs in that the sensors measure the presence of a liquid using the physical property of impedance rather than pH. Sensing the presence of liquid of any pH offers the advantage of detecting reflux that may not be very acidic, a phenomenon called non-acid reflux.

While the thin tube of a pH or impedance test is in place, the patient is instructed to go about their usual activities, including eating, drinking, sleep, work and other activities so that the results obtained represent an average day. A portion of the tube is visible at the patient’s nostril and the tube is felt in the throat, but these factors are manageable.