Page reviewed by: Mr Nicholas Boyle BM MS FRCS 03/07/20
This is a test performed over a 24 hour period to determine how frequently fluid and/or gas from the stomach refluxes into the oesophagus. Traditionally, measuring reflux involves a pH test which measures acid exposure in the oesophagus over this 24 hour period. This can be very useful for determining abnormal acid reflux and its association with a patient’s symptoms. However, it has now become recognised that some patients’ symptoms are caused by reflux from the stomach which is not acidic. This can be missed by standard pH testing and, consequently, patients are told that their symptoms are not reflux-related when in fact they are. We, therefore, combine the pH test with impedance monitoring. Where the traditional method is limited to measuring only the presence or absence of acid, the combined test can also monitor episodes of non-acid reflux.
A small tube called a catheter containing a specially constructed probe is passed through the nostril to the back of the oesophagus. The probe detects the changes in electrical resistance and also measures the pH levels around the oesophagus. These measurements are relayed via the catheter to a portable recorder which is worn for the duration of the test. When symptoms are experienced they can be recorded by the patient by pushing a button. After the 24-hour test is complete the probe is removed and the data is collected for interpretation. Although the procedure can feel uncomfortable, it is not usually painful.
By measuring impedance combined with traditional pH measures, any movement of gas or liquid is recognised, regardless of acidity, allowing a more thorough evaluation. As well as reflux and reflux symptoms, swallowing behaviours such as aerophagia can be studied and their association with reflux recorded by the probe. Impedance-pH monitoring is also able to evaluate the extent of reflux along the length of the oesophagus or beyond the larynx (voice box). This is especially useful for evaluating reflux symptoms affecting the throat, including globus (a lump in the throat feeling), hoarseness and chronic cough. These symptoms are common, especially in laryngo-pharyngeal reflux (LPR), which can be related to reflux of all kinds.