J Neurogastroenterol Motil 2024; 30(2): 251-252  https://doi.org/10.5056/jnm23190
Ambulatory Impedance-pH Assessment Is the Industry Standard But Is It Always the Best Choice?
Frederick W Woodley,1,2,3* Carlo Di Lorenzo,1,2,3 and Raul Sanchez1,2,3
1Center for Motility Disorders, Nationwide Children’s Hospital, Columbus, OH, USA; 2Division of Gastroenterology, Nationwide Children’s Hospital, Columbus, OH, USA; and 3Department of Pediatrics, The Ohio State University College of Medicine, Columbus, OH, USA
Received: December 14, 2023; Accepted: January 18, 2024; Published online: April 30, 2024
© The Korean Society of Neurogastroenterology and Motility. All rights reserved.

cc This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

TO THE EDITOR: Multichannel intraluminal impedance and pH monitoring (MII-pHM) is the gold standard for assessing gastroesophageal reflux (GER) in infants, children and adults, due to its ability to detect nonacid (pH ≥ 4) reflux events.1-3

MII-pHM testing is usually performed for the purposes of assessing the efficacy of anti-reflux medications or for assessing the temporal relationships between various symptoms and GER.4 When a test is ordered, it is scheduled as either an ambulatory test or an inpatient test; the ambulatory choice is usually performed at a more typical home setting and the inpatient test is performed in a medical center or hospital. There are considerations that should be made prior to deciding a particular format.

If the test is to assess the efficacy of acid suppression therapy, the study may be executed as an ambulatory study. If the patient displays behavior that suggests he or she will pull the catheter, the patient should be evaluated as an inpatient where 24-hour surveillance is available. If the temporal relationship between GER and symptoms occurring during the night is of interest, then an inpatient study should be considered as it would be unlikely that the typical caregiver would remain awake all night to assess symptoms. During an inpatient study, a constant attendant can monitor the overnight symptoms and guard against dislocation of the catheter.

Before an ambulatory MII-pHM test, detailed written instructions, describing what should happen over the course the 24-hour test, are given to the family before being instructed to return 24 hours after the start of the study.

There are benefits to ambulatory testing. First, the patients are able to return to their normal home environment where they will be less stressed. Second, with exception of the acidic foods and beverages restriction, they will be able to eat the foods that they would normally eat. Third, the patients can sleep in their own bed where they will have familiar sleep conditions (lighting, temperature, noise levels, bedding, etc). Fourth, the cost of testing is greatly reduced.

The intended purpose of the ambulatory option was to use a portable recording device that would permit testing in the patient’s natural environment, with the aim of identifying certain foods and/or behaviors that trigger GER.5-7 For this to work optimally, extensive documentation (the event or behavior and the corresponding time of occurrence) of every detail of the 24-hour study would need to be provided to the analyst. Only in this way, could a thorough assessment be possible.

Problems can arise, however, when instructions are not carefully followed. Ambulatory pediatric studies, in particular, can become problematic when supervision in the home is not possible due to a substantial number of siblings, or when patients live in households where the caregiver(s) have special needs. There are a number of issues that could arise during the study: (1) the catheter could become displaced within the esophagus, (2) expensive equipment could become damaged (eg, become wet), (3) important symptoms are not recorded, (4) erroneous data is entered into the box when a child is allowed to play with the buttons, and (5) the caregiver could misidentify symptoms.

In summary, while still the industry standard, not every patient is a suitable candidate for an ambulatory MII-pHM study. It may be helpful for referring clinicians to consult with their social work and/or behavior health colleagues before choosing an ambulatory or inpatient format.

Financial support:


Conflicts of interest


Author contributions

Frederick W Woodley wrote the letter; and Carlo Di Lorenzo and Raul Sanchez made significant contributions during editing.

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