A Novel Method for Determining the Inner Diameter of the Esophageal Body Using a Non-Compliant Balloon Catheter and Pressure/Volume Monitoring and Inflation System

Abstract

Background: Esophageal physiological testing includes manometry, 24-hr pH, esophagram, and impedance testing. More recently, it is possible to measure the inner diameter (ID) of the esophageal body (EB) using a non-compliant balloon with a pressure/volume monitoring/inflation system. Methods: This technology was developed as an adjunct to balloon-based ablation of Barrett's esophagus (BE) using the HALO360 Ablation System (BÂRRX Medical, Sunnyvale, CA). Prior to ablation, ID measurement of the EB is required to: 1) select an ablation balloon size that fits the targeted EB, to ensure electrode contact and mitigate against overstretch, and 2) set ablation energy density (J/cm2) based on the EB ID. The sizing catheter has a non-compliant balloon with outer diameter (OD) 33.7 mm and length 4 cm. Calibration is first performed to record the balloon volume at 4 psi (HALO360 generator). The calibrated (deflated) balloon is passed over a wire, positioned in the EB (5-cm proximal to the top of the BE in cases of ablation), auto-inflated to 4 psi, held at steady state for ∼3 seconds, then auto-deflated. The system displays ID (mm), based on pressure/volume at steady state. Prior to human use, a bench model using 24 cylinders of varying ID (22-33.5 mm) were measured with the system and results of measured vs. actual ID were compared. Thereafter, the system was evaluated in patients undergoing ablation of BE, comparing measured ID, selected ablation balloon ID, and ablation effect. Results: In the cylinder testing, 72 measurements were obtained. The median difference between measured and actual ID was -0.3 mm (IQR -0.5 to 0.0) or -1.2% (IQR -1.7 to 0.0). Thereafter, 238 measurements were made in 34 patients who were undergoing ablation. In the first 20 patients, balloon migration occurred near the gastroesophageal junction (GEJ), confounding measurements. In the final 14 patients, starting higher in the EB resulting in highly reproducible EB ID estimates (median EB ID 25.9 mm, range 21.7-32.6). In 14/14 (100%) cases, an accurate estimate of targeted EB ID was achieved, based on subsequent electrode size and effect. Conclusion: This is the first report of a novel method for measuring the ID in the EB. The results are accurate (within 0.3 mm) and reproducible, and the device is now implemented as an adjunct to ablation of BE (HALO360 Ablation System). Other potential applications may include characterization of non-cardiac CP, quantifying success of stricture dilation, and assessing complications of gastric bypass, fundoplication, and surgical anastomoses.