Houston Methodist. Leading Medicine.
Houston Methodist. Leading Medicine

24-Hour Impedance pH

Testing Information: What is a 24-Hour Impedance pH (Nasal Catheter)

What is a 24-Hour Impedance pH (Nasal Catheter)?

The 24 Hour pH Impedance pH Probe test is a test done to detect reflux activity using impedance and pH testing. It categorizes reflux episodes as being acidic or nonacidic using both the pH and impedance information. Since this test provides statistical analysis regarding symptom associations, it allows for the detection of both acid and nonacid reflux in patients with refractory GERD while on or off acid-suppressive therapy.


Some patients may experience some throat discomfort and nosebleed.

Before the procedure

Follow your physician’s instructions regarding discontinuing medications. Drugs such 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 7 days prior to the test. Your physician will instruct you to take these medications or withhold them.

If your physician has instructed you to withhold the above medications and you are experiencing discomfort you may take antacids such as, Rolaids®, Tums® or Mylanta®.

What to do the night before the procedure

Do not eat or drink anything after midnight prior to your test. Do not smoke the day of your test. If you are an asthma patient bring your inhaler.

Preparing for the procedure

The patient is admitted to the Reflux Center as an outpatient. Vital signs are taken.

During the procedure

  1. An esophageal motility test is first done to 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 The catheter is withdrawn slowly as the patient is given sips of water. This portion of the test takes 20 to 25 minutes and the motility catheter is 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 be asked to return the following day to have the probe removed. You will be given written instructions 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 disappears as patients become adjusted to the probe being in place.

After the procedure

You may drive yourself home after the procedure.