Novel Endoscopic Application of a New Flexible Fiber CO2 Laser for Esophageal Mucosal Ablation

Abstract

Background: The CO2 laser is one of the most widely used surgical tools in the aerodigestive tract because of its predictable penetration depth and minimal collateral damage due to efficient absorption of CO2 laser energy by tissue water content. Until recently, endoscopic use was limited by lack of an efficient delivery system. We evaluated the performance, efficacy, and safety of a novel, photonic band gap CO2 laser developed by OmniGuide Inc. for esophageal mucosal ablation in a swine model.Methods: Initial evaluation was performed on ex vivo swine esophageal tissue followed by endoscopic studies in freshly euthanized swine at 7, 10, 15, 20W power and 0, 1, 2, 5 & 10 mm distances, using continuous and pulsed current, to determine optimal performance settings. In an IACUC-approved protocol, 4 Yorkshire pigs were placed on omeprazole, fasted and underwent circumferential ablation of the distal 6 cm of the esophagus at 10W continuous current. The animals were survived 14 & 28 days to evaluate delayed tissue effects. Prior to necropsy, the proximal esophagus was ablated to evaluate the homogeneity of ablation and depth of injury immediately after single and repeat ablation with the laser. Results: Based on tissue & cadaveric studies, a setting of 10 W continuous current and a 5 mm working distance were deemed optimal. In the survival study, the treated pigs resumed a normal diet within 24 hours and showed no signs of dysphagia or weight loss. Pathology at 2 and 4-weeks revealed squamous re-epithelialization with absent to minimal histologic evidence of injury and no strictures. In the freshly ablated areas, a single application of the laser produced complete transepithelial ablation of 96% of the treated surface area with a depth of injury extending to the muscularis mucosa in 68% and superficial (upper 10%) submucosa in 32%. With immediate sloughing and reapplication to the same area, 100% ablation was achieved with a similar depth of injury (34% superficial submucosa). One animal, ablated twice, had a focal injury to the superficial muscularis propria related to direct ‘wedging’ of the laser into the wall; however, no transmural injury was noted in any of the pigs. Conclusion: These porcine studies suggest a promising role for the flexible fiber CO2 laser in esophageal mucosal ablation. Homogeneous ablation was achieved with a predictable penetration depth (even with repeat application), and minimal tissue injury. These results warrant further evaluation of the laser as an ablative device for Barrett's as it may overcome the limitations of currently available technologies including perforation, stricture, and lack of homogeneous ablation.