Gastroenterology Procedure Unit
An impedance study is a test done to find out if contents from the stomach are coming up into the esophagus (food tube). It helps evaluate acid and non-acid gastroesophageal reflux.
In this test, a thin, flexible tube is passed through the nose, down the back of the throat, and into the esophagus. The tube is carefully taped into place on your child's cheek. The end of the tube is attached to computer which will remain at your child's bedside throughout the study.
Because of the computer, your child will need to stay overnight in the hospital. Your child will need to stay in the room close to her bed. She will also need to use a bedside commode (toilet) instead of walking to the bathroom. You may want to bring books, small toys, videotapes or other items to occupy your child while she is in bed.
How long does it take?
An Impedance Study takes 18 to 24 hours. The tube is left in place for this time. You will be asked to keep a diary of your child's activity during the study. The doctor will use the diary to compare the computer reading with your child's activity.
How should I prepare my child?
Your child must have an empty stomach for an impedance study.
- If your child is younger than six months, he must have NOTHING to eat or drink for two hours before the scheduled procedure time.
- If your child is older than six months, he must have NOTHING to eat or drink for four hours before the scheduled procedure time.
If your child takes any medication that reduces the amount of acid in the stomach (such as ranitidine (Zantac), omeprazole (Prilosec), Prevacid, Pepcid, as well as Maalox, Tums, or Gelusil) , please ask your child's doctor if he should continue those medications as usual or if he should stop taking the medication three days before the test.
When you talk with your child about the test, explain in simple terms why it is needed.
What happens before the test?
This tube is usually placed in the Endoscopy Unit on Farley 3. You and your child will then be admitted to an inpatient floor. If your child is already in the hospital, the test will be done on his/her hospital unit.
If your child is not already a patient in the hospital, you must first register in the Admitting Department located on Main 1 in the main hospital in Boston.
Please arrive in the Admitting Department one hour before the scheduled time of the test. It is important that you are on time, so that the study does not have to be canceled. Studies usually begin on time. However, sometimes there are unexpected delays.
After you registering at Admitting, you will go to the Endoscopy Unit in the Farley Building on the third floor. (From the Main Lobby, take the stairs or glass elevator to the Farley Building. Take the Farley/Pavilion elevators to the third floor. Follow the signs for the Endoscopy Unit.)
When you arrive at the Endoscopy Unit, a nurse will greet you and your child, explain the test, and answer your questions.
What happens during the test?
- The nurse will check your child's height to determine where to place the tube. To help calibrate the computer, your child will dip his or her finger into liquids in two test tubes.
- The nurse will pass a tube through your child's nose into the stomach. You may stay with your child while the tube is passed. Infants and young children will be snuggled in a blanket to help them to feel secure and stay still while the tube is being passed. Older children, who are more likely to cooperate, may prefer to sit in a chair while the nurse passes the tube. Passing the tube may cause your child to cough, sneeze, or gag. This feeling will pass after the tube is taped in place. Once in place, the tube should not bother your child.
- Once the tube is taped in place, your child will have an X-ray to check the exact position of the tube. Depending on the X-ray results, the tube may have to be repositioned and retaped. Special sleeves may be put on infants and small children to prevent them from bending their elbows and pulling out the tube.
- You will be asked to write down what your child is doing while the tube is in place, such as eating, sleeping and coughing. Your child's nurse will explain exactly what needs to be written down to help with the study.
- The tube will be removed the next day by a member of the GI staff. Removing the tube takes less than a minute and does not hurt. Some children cough or sneeze.
How will we be informed of the results?
When the tube is removed, the information recorded in the computer will be interpreted by a Children's GI doctor. Call your child's primary doctor one week after the study for the results.
When to call your child's doctor or nurse
If your child is sick 24 to 48 hours before the test is scheduled, call the GI/Endoscopy Unit at 617-355-6172 between 7 a.m. and 3 p.m. Ask to speak to one of the nurses.
If you have any questions about the test, call the above number.
For emergencies, you can call a GI doctor 24 hours a day. Call the hospital page operator at 617-355-6369, and ask for the GI fellow on call.