Impact of Body Positioning on EndoFLIP Measurements: A Comparative Study of Supine and Left Lateral Decubitus Positions

The Endoluminal Functional Lumen Imaging Probe (EndoFLIP) is an FDA-approved device for patients aged 5 years and older and it utilizes high-resolution impedance planimetry and volume-controlled distension to evaluate the GI lumen including the esophagogastric junction. EndoFLIP has become an invaluable tool in pediatric gastroenterology helping to characterize various luminal conditions including but not limited to esophageal stenosis and compression, screening for dysmotility, guiding esophageal dilation through the selection of the optimal dilator size, among others. Despite its increasing clinical utility, there is currently no standardized protocol for its use and much of the technique is derived from adult practice.

Proceduralists perform measurements based on individual preference, with some favoring the supine position and others preferring the left lateral decubitus position. This lack of consensus has been an active topic of discussion among pediatric advanced endoscopists who perform EndoFLIP, yet no published studies exist comparing measurements obtained in different positions. This variability presents a significant clinical problem because positioning may influence EndoFLIP parameters through several physiological mechanisms. In the supine position, abdominal viscera shift posteriorly, potentially altering esophagogastric junction geometry and increasing intra-abdominal pressure. In the left lateral decubitus position, the gastric fundus falls away from the esophagogastric junction due to gravity, possibly reducing external compression and changing the angle of His. Additionally, diaphragmatic crural tension, thoracic mechanics, and vascular engorgement patterns may differ between positions, all of which could affect luminal measurements. These positional differences have important clinical implications, particularly when comparing preoperative and postoperative measurements, assessing dilation durability within the same procedure, or monitoring disease progression longitudinally over multiple visits. If measurements are obtained in different positions across these clinical scenarios, apparent changes in esophagogastric junction function may be artifactual rather than reflective of true physiological change.

The investigators hypothesize that patient positioning, supine versus left lateral decubitus, impacts EndoFLIP measurements. This is a non-directional hypothesis, as there is currently insufficient evidence to predict whether measurements will be higher or lower in one position compared to the other.

Inclusion criteria

• must be between 5 years and 21 years of age at the time of the procedure, which is within the FDA-approved age range for EndoFLIP use.
• participants must be scheduled to undergo a clinically indicated EndoFLIP procedure at Johns Hopkins Children's Center.
• participants must have a parent or legal guardian who is able to provide written informed consent in English, or with the assistance of translation services for non-English speakers.
• participants who are of appropriate age and developmental capacity must be able to provide assent for study participation.
• participants must be candidates for general anesthesia as determined by the anesthesia team.

Exclusion criteria

• patients younger than 5 years of age or 22 years of age and older will be excluded.
• patients who have contraindications to EndoFLIP will be excluded, including situations where upper endoscopy is generally contraindicated such as known or suspected gastrointestinal perforation, hemodynamic instability, severe coagulopathy, or inability to safely undergo general anesthesia.
• patients who cannot be safely positioned in both supine and left lateral decubitus positions due to medical or anatomical considerations will be excluded.
• pregnant patients will be excluded. Pregnancy status will be determined by patient or guardian report and, when clinically indicated, by urine or serum pregnancy testing per institutional protocols for patients of childbearing potential.
• patients whose parent or legal guardian declines to provide informed consent or patients who decline to provide assent when age-appropriate will be excluded.
• patients for whom the proceduralist or anesthesia team determines that participation in the research protocol would pose additional risk beyond routine clinical care will be excluded.