24 Hour pH Impedance Probe Test in Children: What to Expect
Why a pH Impedance Probe Test is Performed
A 24 hour Impedance Probe test will determine the severity of acid reflux in adults and children. Often, this test is ordered to determine how severe a child’s acid reflux is, or to determine if prescribed anti-reflux medications are working. Sometimes, a child will have symptoms of acid reflux, but will not show the reflux on “lower level” tests (such as an upper GI barium series or a gastric emptying scintiscan test). The 24 hour pH probe is the “gold standard” test for identifying the presence of acid reflux, and for quantifying the severity.
While some children show outward signs of acid reflux (painful arching of the back, vomiting, and refusal to eat), some children have a form of reflux known as “silent reflux.” In silent reflux, the child does not vomit, and the acid often affects the airways and may cause pneumonia or asthma in a child with no other obvious signs of reflux.
A 24 Hour pH Probe Study
What is a pH Impedance Probe?
A pH Impedance Probe is a thin wire with probes to detect pH level (if acid reflux is present, a low pH will be recorded) and to detect non-acidic reflux. Some children have non-acidic reflux, and an impedance probe will detect reflux with low or high pH.
The probe wire is threaded through the nose and into the esophagus. The most common type of impedance probe is placed just above the lower esophageal sphincter. The placement is usually verified by X-Ray. Some impedance probes have two sensors: one at the lower esophageal sphincter, and another higher up to detect reflux which may reach the airway.
Another type of impedance probe is the “airway” pH probe. This probe is threaded through the nose and placed just behind the uvula. This probe does not detect liquid reflux. Instead, this 24 hour pH probe detects tiny droplets of acid reflux in the airways of a child with laryngo-pharyngeal reflux disease (also known as extra-esophageal reflux disease or “silent reflux”).
The pH Probe Wire is Small
The Traditional Impedance Probe
The traditional 24 hour pH study may be performed on an outpatient basis for older children. In this case, the child must lie still while the probe is threaded through the nose and into the esophagus. The child is often awake for this process: the procedure is not painful, but may frighten the child. It is a good idea to discuss the logistics of the procedure with children who are old enough to cooperate for the procedure. Young children may have to be restrained with a “papoose board” for the insertion of the probe.
Many times, the probe is placed in combination with an endoscopy and biopsy of the esophagus. If an endoscopy is performed, the child will be sedated for both this procedure and the probe placement. This method is the easiest on the child, as the most traumatic part of the procedure (probe placement) is performed while the child is asleep.
Once the probe is placed, the wire will be tucked behind the child’s ear and taped securely into place. The wire will be connected to a monitoring device, which will record any episodes of reflux. The placement of the probe will be verified by an X-ray, and the child will be allowed to either go home with the parent, or will remain in the hospital for an overnight stay.
Very young children will often be admitted to the hospital for an overnight stay once the pH probe is placed. Special arm bands called “no-no’s” are used on the child’s arms. This is to prevent the child from pulling out the pH probe. It is highly important to keep these on the child’s arms- if the probe is pulled out, the entire test will have to be repeated.
For older children who are allowed to return home with the pH probe in place, it may be a good idea to request “no-no’s” for the night-time sleeping hours. A child may accidentally pull out the probe during sleep, and the entire test would have to be repeated. In addition, request extra adhesive tape to re-secure the probe if the original tape becomes wet or dislodged.
The monitoring device has several buttons, which parents will have to activate when certain activities are performed by the child. Eating, sleeping, and any heartburn pain are to be entered by pressing a button when the child is engaged in any of these activities. Parents will be required to keep a log of all of the child’s food intake and meal times, in addition to sleep times.
The results of the study are often available 1-2 weeks after the test has been completed. Once the data is analyzed, the test will show if the child has gastro-esophageal reflux disease (GERD), and the severity of the GERD (if present).
Our Personal Experience with a Traditional pH Impedance Probe
Our own son had his first 24 hour pH probe test run to determine the cause of his refusal to eat and failure-to-thrive problems. He had no outward signs of acid reflux, and his upper GI barium X-ray was entirely normal. He also had a gastric emptying scan which did not show any acid reflux, even though the scan lasted for an entire hour!
He was admitted to the hospital and had the pH probe placed while he was sedated for an upper GI endoscopy. He was only 2 years old, so he was kept in the hospital overnight. The “no-no’s” were placed on his arms, along with socks over his hands to keep the probe from getting dislodged. This was a very trying 24 hours, as it is hard to entertain a toddler who cannot use his hands or play in a rambunctious manner. A portable DVD player is a lifesaver in this situation: there is little else the child can do to keep entertained.
The probe was removed 24 hours after it was placed, and the removal is a very quick procedure. We went home and waited for 2 weeks to get the results. Once the results were obtained, we were shocked. His reflux was so severe, he was literally off the charts for the amount of time he spent with acid in his esophagus. Over 25% of his day was spent with a pH of 1 (this is pure acid) in his esophagus. He was prescribed a proton-pump inhibitor medication and we began to see an improvement in his eating habits. He went from below the 3rd percentile on the weight charts to a healthy 20th percentile within a matter of months.
The Pharyngeal (Airway) pH Probe
Some children with silent reflux will have chronic ear infections, chronic sinus infections, laryngomalacia (a floppy airway near the larynx, or voice box), frequent upper respiratory infections, or a difficulty swallowing (dysphagia). This form of reflux, called laryngo-pharyngeal reflux disease (or LPR) is distinct from GERD. LPR reflux is caused by a dysfunction of the upper esophageal sphincter. Often, LPR reflux is managed by an Ear, Nose and Throat doctor (ENT) rather than a Gastro-Intestinal specialist (GI).
Restech has developed a pH probe which can detect tiny reflux droplets in the airways of the child. This probe is much shorter than the traditional pH probe, and sits just below the uvula (the dangling thing in the back of the mouth). This probe does not require an X-ray to place, because the position of the probe can be determined by looking into the child’s mouth. A red, blinking light can be seen when the child opens his mouth and the tongue is depressed.
Children with chronic upper respiratory problems may have this test performed. Sometimes, silent reflux is difficult to control with proton-pump inhibitors and acid-blocking drugs. A doctor may order this test while a child is on anti-reflux medications, to determine if the drugs are working for the child.
This particular pH probe is generally placed on an outpatient basis, usually in an ENT’s office. The monitoring device to the Restech pharyngeal probe is wireless, so the child does not have to carry the recording device on their back. The device only records within a limited range, however, so be sure to keep the recording device near the child at all times. Like the traditional pH probe, the child’s activities will be monitored by pressing buttons on the device for eating, sleeping, or episodes of heartburn. A log will be kept by the parents to record the child’s daily activities. Some very young children will be kept inpatient for this test, to ensure the probe is not pulled out during the 24 hour recording period.
Bad News: The pH probe Falls Out
Our Personal Experience with the Pharyngeal pH Probe
Our son developed severe obstructive sleep apnea at the age of 2 ½, and the cause was found to be an acquired form of laryngomalacia (floppy larynx). After having four sets of ear tubes placed for chronic ear infections, developing laryngomalacia, and having chronic sinusitis, our ENT wanted to determine if his medication dosages were effective in controlling his reflux. A pharyngeal reflux probe was placed when he was three years old, to monitor the amount of reflux hitting his airway. We had to be sure the reflux was under control prior to having a surgery performed to fix his floppy airway.
This probe was placed on an outpatient basis, and we had to monitor him at home for the duration of the study. He was extremely good about leaving the probe device alone, so we left the “no-no’s” off this time, and allowed him to play quietly at home. At the age of three, the process was much easier because he had the use of his hands and understood that he could not pull the probe out.
Unfortunately, the tape holding the probe in place became wet throughout the night. To our utter dismay, we found him asleep with the probe dislodged at about 5:00am. This was highly frustrating, as there was a high likelihood the entire test would have to be repeated. We returned the probe to the ENT’s office, where the data was collected.
We were contacted shortly after returning the probe to find out that they did have enough data. This was a huge relief, as we did not want to have to repeat the test. Unfortunately, they showed that his medication was not controlling the reflux. They prescribed an acid-blocking medication and we had to repeat the pharyngeal pH probe to demonstrate the reflux was adequately controlled.
The second probe placement went well, and we equipped ourselves with a lot of extra medical tape and the “no-no’s” for use at night. Fortunately, this probe stayed in place and gathered enough data to show that the reflux was under sufficient control for the airway surgery to take place.
pH Impedance Probe Results
It generally takes about 1-2 weeks to obtain the results from the pH probe. The doctor will discuss the results at a follow-up appointment, and will also determine any appropriate treatment strategies.
The pH probe will determine the total percentage of time the pH in the esophagus drops below 4. It will also determine the amount of time the pH is below 4 when the child is upright vs. lying down. The number of reflux episodes will be calculated, along with the number of episodes greater than 5 minutes. The time period of the longest acid reflux event will also be recorded.
A common scoring device for the traditional impedance probe is the DeMeester Score. This score takes a composite of the data obtained for the parameters above, and a normal DeMeester score is less than 14.4.
The Pharyngeal Reflux Probe uses a different scoring method, called the Ryan Score. The normal values for acid exposure in the pharynx are less than the esophageal scores – a Ryan score of 4.88 or higher indicates the presence of LPR (extra-esophageal reflux disease).