24-Hour Impedance pH

The 24-hour impedance pH (nasal catheter) probe test detects reflux activity. It categorizes reflux episodes as being acidic or nonacidic using both the pH and impedance information. This test provides statistical analysis regarding symptom associations, allowing for the detection of both acid and nonacid reflux in patients with refractory gastroesophageal reflux disease (GERD), while the patient is on or off acid-suppressive therapy.
About the 24-Hour Impedance pH Procedure
You will be admitted as an outpatient where staff will take your vital signs. Expect the following steps to occur during your procedure: 

1. An esophageal motility test will first determine correct placement of the impedance pH probe. This involves inserting a very small catheter into the nostril and advancing it into the stomach. The catheter is withdrawn slowly as you take sips of water. This portion of the test takes 20 to 25 minutes and the motility catheter will be removed at the completion.

2. Next, a different catheter, called an impedance pH probe, is inserted into the nostril and advanced into the esophagus. The impedance pH probe will remain in place for 24 hours and is connected to a small recorder that you will carry on a strap over your shoulder. You will return the following day to have the probe removed. Written instructions will include information regarding diet, medications, smoking and bathing. You will also be provided a diary sheet to record selected events throughout the 24-hour period.
3. While the impedance pH probe is in place, some patients experience irritation in the throat, which can be relieved by taking sips of water; do not use throat lozenges, as they may change the results of the test. Some patients report more difficulty sleeping than usual because of awareness of the probe. Although the probe does not prevent eating or drinking, some patients find these activities somewhat uncomfortable. This discomfort lessens as you adjust to the probe being in place.

Drugs such as proton pump inhibitors (AcipHex®, Prilosec®, Prevacid®, Protonix®, Nexium®) or H2 blockers (Axid®, Pepcid®, Tagamet®, Zantac®) may affect test results. It is preferable that these drugs be withheld seven days prior to the test, but you should follow your physician’s instructions regarding discontinuing medications. If your physician has instructed you to withhold the medications listed above and you are experiencing discomfort, you may take antacids, such as Rolaids®, Tums® or Mylanta®. 

The night before the procedure, do not eat or drink anything after midnight. Do not smoke the day of your test. If you are an asthma patient, bring your inhaler.
Some patients may experience a nosebleed. You may drive yourself home after the procedure.


Houston Methodist provides diagnostic testing, including the 24-hour impedance pH procedure, at the following convenient locations.