Study objectives: To test the incendiary characteristics of various silicone endobronchial stents under the impact of the Nd-YAG laser.
Design: In vitro study in the laser laboratory of a university-affiliated city hospital.
Setting: The experiments were performed in a reaction chamber under controlled oxygen concentrations. The radiolucent and radiopaque Dumon silicone stent (Novatech; Aubagne, France) and the tracheal part of the Dynamic stent (Ruesch AG; Kernen, Germany) were tested. The Dumon stents were either clean, covered with a thin layer of blood, or mounted on fresh pig tracheal wall. The laser was aimed on them perpendicularly from distances of 1.0 cm and 0.5 cm.
Interventions: Minimal oxygen concentration to allow ignition and impact time for power outputs (POs) between 10 W and 80 W were determined.
Measurements and results: The lowest oxygen concentration that allowed ignition of some stents was 40%. The clean radiolucent stent could not be ignited with up to 100% ambient oxygen concentration. Radiopacity, presence of blood, tracheal wall, and metal, as well as higher PO and shorter distance of the laser probe decreased impact time to ignition. The radiopaque blood-covered stent was most easily ignited. For this stent, at a PO of 40 W, impact time to ignition was 1.5 +/- 0.2 s, and at 30 W was 2.6 +/- 0.3 s.
Conclusions: At ambient oxygen concentrations > or = 40%, silicone stents can catch fire. Depending on the condition of the stent, the distance of the laser probe, and PO, ignition can occur after short impact times. To prevent stent ignition, oxygen concentration should be kept < 40%. When unusual circumstances require working with higher oxygen concentrations, pulse duration needs to be limited or stent removal might be considered before firing the laser.