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 forpatients aged 5 years and older and it utilizes high‐resolution impedance planimetry andvolume‐controlled distension to evaluate the GI lumen including the esophagogastricjunction. EndoFLIP has become an invaluable tool in pediatric gastroenterology helping tocharacterize various luminal conditions including but not limited to esophageal stenosisand compression, screening for dysmotility, guiding esophageal dilation through theselection of the optimal dilator size, among others. Despite its increasing clinicalutility, there is currently no standardized protocol for its use and much of thetechnique is derived from adult practice.Proceduralists perform measurements based on individual preference, with some favoringthe supine position and others preferring the left lateral decubitus position. This lackof consensus has been an active topic of discussion among pediatric advanced endoscopistswho perform EndoFLIP, yet no published studies exist comparing measurements obtained indifferent positions. This variability presents a significant clinical problem becausepositioning may influence EndoFLIP parameters through several physiological mechanisms.In the supine position, abdominal viscera shift posteriorly, potentially alteringesophagogastric junction geometry and increasing intra‐abdominal pressure. In the leftlateral decubitus position, the gastric fundus falls away from the esophagogastricjunction due to gravity, possibly reducing external compression and changing the angle ofHis. Additionally, diaphragmatic crural tension, thoracic mechanics, and vascularengorgement patterns may differ between positions, all of which could affect luminalmeasurements. These positional differences have important clinical implications,particularly when comparing preoperative and postoperative measurements, assessingdilation durability within the same procedure, or monitoring disease progressionlongitudinally over multiple visits. If measurements are obtained in different positionsacross these clinical scenarios, apparent changes in esophagogastric junction functionmay be artifactual rather than reflective of true physiological change.The investigators hypothesize that patient positioning, supine versus left lateraldecubitus, impacts EndoFLIP measurements. This is a non‐directional hypothesis, as thereis currently insufficient evidence to predict whether measurements will be higher orlower in one position compared to the other.