High-resolution esophageal manometry well-tolerated by most children
Manometry has long been the test of choice for assessing esophageal motor function, especially for evaluating the common esophageal complaints of dysphagia and noncardiac chest pain. In children, it also is useful for identifying achalasia and rumination syndrome and for evaluating feeding difficulties and esophageal changes in scleroderma.
Two types of manometry systems can be used to evaluate the esophagus. Conventional manometry uses a water perfused catheter with five to eight sensors displaying point pressure in the form of stacked line tracings. Because of the limited number of sensors and the distance between them, the catheter must be repeatedly repositioned in order to obtain a complete study, making the procedure especially time-consuming and uncomfortable for pediatric patients. Further, accurate interpretation of manometry data, even in experienced centers, can be challenging.
High-resolution manometry (HRM) with esophageal pressure topography (EPT) was designed to overcome these limitations. HRM uses 24 to 36 sensors spaced 1 centimeter apart, allowing readings of both sphincters and the entire esophagus simultaneously in real time. To better visualize this data, EPT, a 3-D plotting format, represents pressure changes visually, with cool colors (blue and green) signifying low pressure and warm colors (orange and red) denoting higher pressure. Time and location within the esophagus are continuous variables, with pressure magnitude indicated at each coordinate by color. This creates an isobaric contour map that more closely aligns EPT with imaging techniques than data analysis. Combined with intraluminal impedance monitoring, which measures the flow of liquids and air in the esophagus, HRM and EPT provide a far more complete study than can be obtained with conventional manometry.
Both conventional and high-resolution manometry can determine the pressure of the upper and lower esophageal sphincters and whether or not a swallow is peristaltic. But the motor function of the esophagus can be described in greater detail using HRM and the Chicago Classification of esophageal motility disorders, which uses an algorithmic scheme to analyze HRM studies.
Two commonly used measurements are the integrative relaxation pressure (IRP) and the distal contractile integral (DCI). The IRP measures the effectiveness of the esophagogastric junction (EGJ) relaxation during swallow by measuring the average minimum pressure for four of the 10 seconds following a swallow. The DCI measures the vigor of the esophageal contraction by combining the length of the esophagus with the contractile amplitude and duration.
Rayna M. Grothe, M.D., a pediatric gastroenterologist at Mayo Clinic's campus in Rochester, Minnesota, explains: "With high-resolution manometry, you can get an accurate reading of sphincter pressure as well as the total strength or vigor of smooth muscle contraction and timing of the peristaltic sequence. The impedance sensors in the high-resolution catheter give a good sense of what is going on functionally. So you have two ways to measure esophageal function — muscle activity and the strength of contractions as well as the flow of fluid or air."
Mayo Clinic's campus in Rochester, Minnesota, has been using HRM for pediatric patients since early 2015, at a rate of about two cases a week. The test is usually performed after upper endoscopy, with placement of the manometry catheter while patients are still under anesthesia. Older children who don't require upper endoscopy are awake, and the catheter is placed using topical nasal anesthesia. Most children do very well. Dr. Grothe says sips of water, deep breathing and quiet encouragement from the nurse are usually help make for successful placement.
HRM is performed in the pediatric postoperative area, with a team of pediatric GI nurses, post-anesthesia nurses and a child life specialist.
"We use Ipads and relaxation techniques during the study, and that works very well," Dr. Grothe says. "We also engage with the children and try to get them to look at the monitor; most are enthralled with the pressure waves and different colors they see when they swallow. Still, it takes patience. Although the study is usually only 10 liquid swallows with each swallow measured over a 20-second time frame, the study will be most successful if children are relaxed and comfortable and not rushed."
One of the main indications for HRM in children is to confirm clinical suspicions of achalasia, a neurodegenerative disorder of the esophagus. Typical features include incomplete relaxation of the lower esophageal sphincter (LES) and lack of peristalsis in the esophagus — both clearly measured with HRM.
"If we find achalasia, manometry can help define treatment, which may be botulinum toxin, pneumatic dilation or surgery. If it's not achalasia, HRM can better identify the problem, such as EGJ outflow obstruction or post-fundoplication dysphagia," Dr. Grothe says. "One of the best examples is scleroderma, in which esophageal motility vigor is low — low DCI — with a hypotensive LES. High-resolution manometry helps define that, whereas upper GI findings can be normal."
She points out that knowing more about esophageal function in relation to patient symptoms can help clinicians better distinguish what is normal from what isn't. In the future, she says, HRM may be particularly helpful for pediatric aerodigestive disorders.
"Aerodigestive children have breathing, swallowing and feeding problems. Physicians often blame reflux and possibly aspiration for these symptoms, but identifying the exact problem with breathing and swallowing gives us a better chance of treating these patients. HRM with impedance may be able to help us better manage complex cases by allowing us to assess the function of the upper and lower esophageal sphincters, esophageal motility and impedance all at the same time," Dr. Grothe says.