Metal Endotracheal Tubes

In 1978, Norton and De Vos^[82] introduced a nonflammable endotracheal tube constructed as an interlocking stainless steel spiral coil, resembling electrical cable armor (Baxter Healthcare Cop., Niles, IL). The manufacture of this endotracheal tube has been discontinued. Its walls were not airtight, and although this property allowed a cooling gas flow to the exterior surface, it could make ventilation difficult in patients with relatively noncompliant lungs, particularly because the tube had no inflatable cuff. Jet ventilation with a modified Sanders Venturi coupler was suggested as a means to overcome this problem, ^[83] as was the use of a separate, slide-on cuff, but these are all flammable and pose an ignition risk.

Two other metal endotracheal tubes are commercially available and are approved for use with specific lasers. The Laser Flex tube (Mallinckrodt Inc., St. Louis, MO) is an airtight stainless steel spiral with two distal, saline-inflatable PVC cuffs (redundant in case of puncture of the proximal cuff). This tube is resistant to CO₂ and KTP laser energy,^[84] but not the Nd:YAG laser.^[78] The Bivona Fome-Cuf (Bivona Inc., Gary, IN) is an aluminum spiral tube with an outer covering of silicone and a unique, self-inflating foam sponge-filled cuff, which prevents deflation after puncture. This feature allows continued positive-pressure ventilation and segregation of airway gases from the operative site, but it may lead to injury if a puncture of the cuff or of the filling tube prevents deflation before removal. The Fome-Cuf is approved for use only with pulsed CO₂ lasers.

The use of laser-resistant endotracheal tubes requires particular care to prevent mucosal abrasions, because these tubes tend to be bulkier and more rigid than conventional tubes. Surgeons must ensure that laser energy is not reflected from smooth metal surfaces and directed at sensitive structures. Use of a metal endotracheal tube does not imply absolute protection from ignition; 50 W of an Nd:YAG beam focused to 0.68 mm has been reported to ignite a Laser Flex tube in 6 seconds. ^[85]