Patient instructions for esophageal impedance study

Multichannel intraluminal impedance (MII) is a new technique that measures gas or liquid reflux into the esophagus. It is useful in patients who have reflux of substances which are not acidic and therefore would not be detected by the pH study or the Bravo capsule. It may be used alone or in combination with the pH study. As in the standard pH study, the impedance study also uses a small catheter passed through the nose into the esophagus. The catheter is attached to the waist recorder, and the patient is asked to perform his or her regular daily activities.

A small catheter (pH catheter) will be passed through one side of your nose. The catheter will be advanced into the esophagus. The catheter will remain in place for 24 hours. The catheter will be attached to a small recording device which may be secured around the waist or over the shoulder.

Please arrive 30 minutes prior to your appointment for registration. If you are unable to keep your appointment, you must cancel at least 48 hours in advance or you will be referred back to your primary care physician.


  • Wear loose comfortable clothing that buttons up in front.
  • Do not eat or drink anything six hours before pH catheter placement.
  • No proton pump inhibitors for at least seven days (e.g. Prevacid, Prilosec, Aciphex, Nexium, Protonix)
  • No H-2 blockers for 48 hours (Axid, Pepcid, Tagment, Cimetideine, Zantac).
  • No antacids 24 hours before catheter placement (Maalox, Mylanta, Tums, Gaviscon)
  • No x-rays while the catheter is in place.
  • You may not shower or tub bathe while catheter is in place. Sponge bathe only.
  • Do not operate a microwave while probe is in place.

If this study is being performed to test effectiveness of medicine, the patient should continue their normal medcation.

If you have any questions or concerns, please call the Gastroenterology Unit, Monday through Friday, 7:30 a.m. - 4 p.m. at 916-734-5561.