Nd-YAG Laser Damage to Metal and Silicone Endobronchial Stents: Delineation of Margins of Safety Using an In Vitro Experimental Model

Abstract

Study objectiveTo identify margins of safety within which bronchoscopic Nd-YAG laser resection can be performed without damaging indwelling tracheobronchial stents. DesignExperimental in vitro study simulating a patient-care environment. MethodsUncovered and covered metal Wallstent (Schneider; Zurich, Switzerland) and Dumon (Bryan Corporation; Woburn, MA) silicone stents were deployed in the tracheobronchial tree of a ventilated and oxygenated (fraction of inspired oxygen, 40%) heart-lung block of a dead canine. Rigid bronchoscopic Nd-YAG (1,064 nm) laser procedures were performed in order to deliver laser energy using fiber-to-target distances of 10 mm and 20 mm, and noncontact, continuous-mode, 1-s pulses at power settings of 10 W, 30 W, and 40 W. The major outcome measure was laser-induced stent damage, defined as discoloration, ignition, or breakage. This was assessed using six power densities: 75 W/cm2, 172 W/cm2, 225 W/cm2, 300 W/cm2, 518 W/cm2, and 690 W/cm2. ResultsThe uncovered Wallstent and the silicone stent remained intact at power densities of 75 W/cm2 (10 W, 20 mm) and 172 W/cm2 (10 W, 10 mm), but were damaged at power densities > 225 W/cm2 (30 W, 20 mm). The covered Wallstent was damaged at all power densities tested. ConclusionUncovered Wallstent and silicone stents are not damaged when Nd-YAG laser energy is delivered using power densities ≤ 172 W/cm2 (10 W, 10 mm). Covered Wallstents, however, had a high likelihood of ignition at all power densities studied.