A bubble-free strategy for saline-immersion endoscopic submucosal dissection: optimized electrosurgical settings and continuous low-pressure saline perfusion

Saline-immersion therapeutic endoscopy and the water pressure method have recently gained attention as novel approaches for endoscopic submucosal dissection (ESD [ 1 ] [ 2 ]). These techniques offer multiple advantages, including stable visualization of the submucosal layer, improved scope maneuverability, and controlled submucosal expansion by buoyancy and hydrostatic pressure. However, during saline-immersion ESD, visibility is often impaired by bubble formation resulting from vaporization and electrolysis during the use of high-frequency devices [ 3 ]. To overcome these issues, we developed continuous low-pressure saline perfusion (CLPSP; [ Fig. 1 ] [ 4 ] [ 5 ]). CLPSP rapidly expels bubbles from the endoscopic field, maintaining a clear view even during active dissection. Nevertheless, when high-voltage modes such as swiftCOAG and forcedCOAG are applied, which are often applied during submucosal dissection to achieve hemostasis, the generation of bubbles remains pronounced because of spark-induced vaporization and electrolysis. Even with continuous saline perfusion, these bubbles can temporarily impair visibility. Fig. 1 A nasogastric tube is in place for continuous low-pressure saline perfusion (CLPSP). Based on these findings, we designed an optimized electrosurgical strategy for bubble-free ESD under saline immersion ([ Fig. 2 ], [ Fig. 3 ] and [ Video 1 ]). All procedures were performed using a VIO3 electrosurgical generator (Erbe Elektromedizin, Tübingen, Germany). Submucosal dissection is performed using endoCUT I (effect 4, duration 1, and interval 2), whereas softCOAG (effect 6–10, QuickStart off) is used for pre-coagulation of larger vessels. Under saline immersion, unlike in air, softCOAG ensures stable current conduction and uniform coagulation, even with a needle-type knife ([ Fig. 4 ]). SoftCOAG delivers a low-voltage continuous current without spark or bubble formation. In the event of bleeding, high-flow saline irrigation maintains visibility, and forcedCOAG achieves hemostasis while suppressing vaporization and spark formation. In addition, CLPSP using automatic water irrigation synchronized with the electrosurgical unit (EIP2; Erbe, Tübingen, Germany) is useful for this technique. Fig. 2 Optimized high-frequency settings used for bubble-free ESD under saline immersion. ESD, endoscopic submucosal dissection. Fig. 3 Combination of optimized high-frequency settings with CLPSP enables bubble-free ESD under saline immersion, maintaining a clear view even during active dissection. CLPSP, continuous low-pressure saline perfusion; ESD, endoscopic submucosal dissection. Download Video A bubble-free strategy for saline-immersion endoscopic submucosal dissection: optimized electrosurgical settings and continuous low-pressure saline perfusion.Video 1 Fig. 4 Pre-coagulation of larger vessels using softCOAG under saline immersion. Stable current conduction allows uniform coagulation without bubble formation. a Large submucosal vessel. b Pre-coagulation using softCOAG (effect 6–10, QuickStart off). c Bleeding prevention and safe cutting during dissection. This combination of optimized high-frequency settings with CLPSP enables bubble-free ESD under saline immersion, preventing inadvertent bleeding and allowing smooth, efficient, and safe dissection. Endoscopy_UCTN_Code_TTT_1AO_2AG_3AD Publication History Article published online: 03 February 2026 © 2026. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting unrestricted use, distribution, and reproduction so long as the original work is properly cited. (https://creativecommons.org/licenses/by/4.0/). Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany