In vivo evaluation of argon plasma coagulation in a porcine model

Background: Argon plasma coagulation (APC) is a noncontact form of monopolar electrocautery. One purported advantage of APC includes a limit to the depth of injury. It is unclear from previous studies whether the depth of injury is limited to superficial tissue layers with the settings used in clinical practice. Objective: To evaluate the depth and the area of APC-induced injury by using new modes of APC delivery in an in vivo porcine model in the setting of colonoscopy. Design: Blinded quasi-experiment. Subjects: Six swine. Intervention: Colonoscopy with the swine under general anesthesia, with application of APC in 2 different pulsed modes and varying power settings and duration of application. Main Outcome Measurements: Surface area and depth of colonic mucosal injury Qualitative histologic analysis of each site of APC application was performed on formalin-fixed specimens after euthanizing the swine. Results: Muscularis propria injury occurred in 22% of lesions with 10 W, 62% of lesions with 20 W, 86% of lesions with 40 W, and 80% of lesions with 60 W Muscularis propria injury occurred in 42% of lesions at I second, 66% of lesions at 3 seconds, and 69% of lesions at 5 seconds. Depth of injury was significantly correlated with total energy delivered (P = .001, r = 0.75). Surface area was significantly associated with total energy delivered (P < .001, r = 0.81). Limitations: This study was performed in distal swine colon rather than human colon. Colon tissue response to APC injury may differ from swine to human colon. The application distance from the APC probe to the colonic tissue may have varied between applications. Conclusions: Muscularis propria injury occurs across a broad range of clinically used APC settings. The frequency of deep injury and the Surface area of the lesion increases with total energy delivered. The lowest power settings (10-20 W) and the shortest durations have the lowest risk of deep tissue injury.