Effect of extraluminal oxygen on carbon dioxide laser ignition of endotracheal tubes.

Ignition times of endotracheal tubes used in laser surgery have been determined in room air with oxygen flowing through the tube. Using uncuffed endotracheal tubes in children, we measured the oxygen level around the endotracheal tube at the vocal cords and found that it closely approximates the inspired oxygen concentration. We then tested Rusch red rubber and polyvinyl chloride endotracheal tubes while varying the external oxygen concentration. Little difference in ignition time was found for the polyvinyl chloride tube. The red rubber tube ignited significantly faster as the ambient oxygen levels were increased to as little as 30%. Our tests indicate that uncuffed red rubber tubes are not safer than polyvinyl chloride tubes when used with the carbon dioxide laser. All endotracheal tubes used with the laser should be tested for ignition at various extraluminal oxygen concentrations.