BACKGROUND: There have been a lot of methods that prevent catatrophic airway fires during laser surgery, but none of them can protect endotracheal tube cuff exposed directly to laser beam. This study was performed to know the preventive effect of viscous lidocaine-filled cuffs on laser-induced combustion, and to know how long we can maintain positive pressure ventilation if laser beam broke out cuff perforation. METHODS: Transparent acrylic trachea attached to artificaial lung was intubated with 8.0 ID polyvinylchloride endotracheal tube. Cuff was filled with 8ml of saline or saline and viscous lidocaine mixture with 2:1 or 4:1 ratio. Positive pressure ventilation with air in tidal volume of 500 ml was begun. The laser output was set to 10 watt/sec in the continuous mode with beam diameter of 1 mm. Laser beam was directed perpendicularly at the part of the cuff protruding between endotracheal tube shaft and acrylic trachea, and laser emission was continued until the cuff was perforated or combusted. RESULTS: There was no case of laser-induced fires. After the perforation of cuff, the tidal volume was slowly decreased in 2:1 mixture of saline and viscous lidocaine filled cuff compared to others (P<0.05). CONCLUSION: 2:1 mixture of saline and viscous lidocaine may be used as an efficient inflating material of endotracheal tube cuffs on laser airway surgery.