- Email: [email protected]
The resistance to carbon dioxide laser ignition of a new endotracheal tube: Xomed laser-shield II
Original Contributions The Resistance to Carbon Dioxide Laser Ignition of a New Endotracheal Tube: Xomed Laser-Shield II James M. Green, MD,* Rene M. Gonzalez, MD,? Nasser Sonbolian, MD,+ Paul Rehkopf, CCE§ Department of Anesthesiology, burgh, Pittsburgh, PA.
*Resident, Department of Anesthesiology and Critical Care Medicine tClinica1 Associate Professor, Department of Anesthesiology and Critical Care Medicine; Chief Anesthesiologist, Eye and Ear Institute Pavilion SClinical Associate Professor, Department of Anesthesiology and Critical Care Medicine Klinical Instructor of Ophthalmology, partment of Ophthalmology
De-
Address reprint requests to Dr. Gonzalez at the Department of Anesthesiology, Eye and Ear Hospital of the University of Pittsburgh, 230 L.othrop Street, Pittsburgh, PA 15213, USA. Received for publication March 12, 1991; revised manuscript accepted for publication September 20, 1991. 01992 Butterworth-Heinemann J. Clin. Anesth. 4:89-92,
1992.
Eye and Ear Hospital
of the University
of Pitts-
Study Objective: To assess the resistance of a new endotracheal tube to penetration and ignition by a carbon dioxide (COJ laser at a clinically relevant power setting. Design: An unblinded, in vitro trial simulating clinical conditions. Setting: The operating room at a university medical center. Patients: None. Interventions: A CO, laser at 20W with a beam diameter of 1 mm was directed onto the Xomed Laser-Shield II at several points: both perpendicular and tangential to the portion of the tube covered by the protective wrap, to the unwrapped silicone tubing just proximal to the cuff, to the cuff filled with saline and methylene blue, and to the unwrapped silicone tubing distal to the cuff. Trials were performed with or without supplemental oxygen (OJ blown onto the study site and with a 6 Llmin flow through the tube containing one offour concentrations of 0, in O,-air admixtures: 21%, JO%, 4076, and 100%. Measurements and Main Results: Under all conditions, the laser did not penetrate the protective wrap, but the overlying polytetrafluoroethylene (Tejlon) sheet was vaporized to an area equal to the size of beam application. The cuff was penetrated b the laser within 5 seconds. The unprotected silicone portion of the tube was penetrated by the laser in a@roximately 5 seconds, and time to formation of a blowtorch phenomenon shortened with increasing the percentage of 0,flowing through the tube. Conclusions: The protective coating of the Xomed Laser-Shield II is laser-resistant, but the unprotected silicone proximal and distal to the cuff is laser-vulnerable and can, under certain conditions, promote a blowtorch phenomenon. This tube would be acceptable for use in oral and pharyngeal laser surgery, but we recommend its use only in well-ventilated areas, out of concern for exposure to the products of the @rolysis of Teflon, specifically the development of polymer-fume fever. Keywords: fire.
Laser,
carbon
dioxide;
tube,
endotracheal;
equipment
failure,
Introduction The carbon dioxide (CO,) laser is frequently used in the treatment of upper airway pathologies. Use of the laser near the endotracheal tube during airway surgery has been shown to carry the risk of endotracheal tube ignition and (PVC), red rubber, and the Xomed Laserairway fire. 1-3 Polyvinylchloride
J. Clin. Anesth.,
vol. 4, March/April
1992
89
Original Contributions Shield (Xomed Corp., Jacksonville, FL) endotracheal tubes have previously been shown to be combustible when struck by a CO, laser.4 Xomed has recently introduced the Laser-Shield II endotracheal tube (FZgure I). This tube is composed of clear, supple silicone surrounded by two thin wraps. The inner wrap is an overlapping spiral aluminum strip. The outer wrap consists of a seamless Teflon sheet. Distal to the protective wrap is approximately 1.0 cm of unprotected silicone tubing. Further distal is an unprotected high-volume, low-pressure cuff. The resistance of this tube to penetration and ignition by a CO, laser was tested at a clinically relevant power setting.
wrapped. The CO, laser was directed perpendicularly to these portions of the tube in separate trials with no 0, blown by it but with a 6 Limin flow through the tube containing one of four concentrations of 0, in O,-air admixtures: 21%, 30%, 40%, and 100% (0% air).
Results
A Coherent CO, laser (Model 45OXL, Coherent, Palo Alto, CA) was used. Its output was set at 20W in the continuous mode for up to 1 minute with a beam diameter of 1.0 mm. The Xomed Laser-Shield II (inside diameter 7.0 mm, outside diameter 10.6 mm) was placed on moist towels. The laser was aimed perpendicularly and tangentially to the long axis of the tube at several points along its body and at the cuff filled with saline and methylene blue. During testing, the laser was held at a constant distance from the endotracheal tube. This coincided with the laser’s focal length (approximately 5 cm) and yielded the smallest spot size. Trials involving laser application to the protective wrap were conducted in three environments: (1) in room air, (2) with 100% oxygen (0,) blown by the tube, and (3) with 100% 0, blown by the tube and 100% 0, flowing through the tube at 6 Wmin. The cuff, filled with saline and methylene blue, was tested without supplemental 0,. As shown in Figure I, approximately 1 cm of silicone tube proximal to the cuff is not covered by the protective wrap. The silicone tube distal to the cuff also is un-
With the COP laser aimed perpendicularly to the protective wrap, the Teflon vaporized within approximately 5 seconds, revealing the underlying aluminum wrap. The laser did not penetrate the aluminum wrap in room air or with added 0,. The Teflon wrap did not ignite, and essentially no smoke was observed. Only an area of Teflon the size of the laser’s spot was removed. With the CO, laser aimed tangentially to the protective wrap, the Teflon again vaporized within approximately 5 seconds. Again, the aluminum wrap was exposed, but even with the tube flexed, there was no evidence of penetration through the overlap of the strips. When the CO, laser was directed onto the cuff, it was punctured immediately, emitting a stream of the salinemethylene blue solution. When the laser was directed onto the unwrapped portion of the silicone tube proximal to the cuff, the tube was penetrated within approximately 5 seconds regardless of the concentration of 0, flowing through the tube. When this segment was tested with 100% 0, flowing through the tube, a vigorous blowtorch effect (Figure 2) resulted as the tube was penetrated. This did not extinguish until well after the 0, flow was discontinued. With 40% 0, flowing through the tube, despite penetration of the tube at approximately 5 seconds and a small flame on the outside of the silicone tube at the site of laser impact, a blowtorch effect did not develop until 15 seconds later. Again, this was sustained despite discontinuance of the laser and the supplemental 0, flow. With
Figure 1. The Xomed Laser-Shield II endotracheal tube. (A) The laser-resistant wrapping. (B) The unprotected silicone proximal to the cuff. (C) The cuff inflated with saline and methylene blue. (D) The unprotected silicone distal to the cuff.
Figure 2. The blowtorch effect demonstrated when the unprotected silicone proximal to the cuff was struck by the laser while supplemental oxygen was insufflated through the tube.
Materials and Methods
90
J. Clin. Anesth., vol. 4, March/April 1992
Xomed Laser-Shield
30% 0, flowing through the tube, there was penetration at 5 seconds and a small external flame, but a blowtorch effect did not develop for 25 seconds. Again, it continued after discontinuance of the laser beam and the 0, flow. Once the blowtorch effect was extinguished in all three of these trials, both the distal, unwrapped end of the tube (including the cuff) and a variable portion of the silicone tube underneath the protective wrap disintegrated into charred, friable fragments and dust (Figure 3). With 21% 0, (air) flowing through the tube, penetration occurred at approximately 5 seconds, and there was a small external flame during laser impact but no blowtorch effect. The silicone of this portion of the tube was moderately deformed by the end of the 60-second trial. The unwrapped silicone tube distal to the cuff yielded the same results when tested as did the segment of unwrapped silicone tube proximal to the cuff.
Discussion The CO, laser is being used increasingly often, especially in surgery of the upper airway, because of its precision, hemostatic properties, and reductions in postoperative edema and pain, as compared with conventional surgery. Accidental contact of the laser with the endotracheal tube is reported to be frequent,j and this occurrence carries the risk of an airway fire, which can have tragic consequences.” In view of the frequency with which the laser beam is misdirected onto the endotracheal tube, several methods have been tried and attempts have been made to develop a more laser-resistant tube. It has been shown that adhesive 3M #425 aluminum tape (3M, St. Paul, MN) and copper foil tape (Venture Tape Corp., Rockland, MD), when wrapped carefully in an overlapping fashion, can protect PVC and red rubber tubing from ignition by CO, and Nd-Yag lasers.7 One study has shown minimal advantage of the original Xomed tube over unwrapped red rubber or PVC tubes.” The Laser-Shield II is the most recent laser-resistant
Figure 3. The unprotected silicone after being extinguished.
II and the CO,, laser: Green et al.
tube developed by Xomed. It has the advantages of being flexible, thin-walled, and smooth on both the inner and outer surfaces. The thin outer Teflon wrap provides a smooth surface to prevent mucosal scraping that might otherwise occur if the underlying aluminum wrapping were to brush against tissue. Our study supports Xomed’s claims that the protective wrap is adequately laser-resistant (by withstanding perpendicular laser application) and adequately layered (as the tangential direction of laser application did not penetrate any of the overlaps of the stripping). The vaporization of the outer Teflon coating by the laser did not seem to cause any mechanical problems, although theoretically, exposure of the underlying aluminum wrap could reflect the laser beam onto normal tissue. In addition, if wrapping of the aluminum strips was defective under the overlying Teflon wrap, vaporization of the Teflon could allow penetration of the silicone tube and possible ignition. As the edges of the aluminum strips can be seen under the thin Teflon wrap, one should inspect the Laser-Shield II before use to ensure that the aluminum strips are properly overlapped. The pyrolysis products of Teflon are known to cause pulmonary edema and mucosal ulceration;8 however, these results would most likely require more Teflon to be heated than is present on the Xomed Laser-Shield II.* An entity known as “polymer-fume fever” also may occur as a result of exposure to the pyrolysis products of Teflon and in doses as small as that vaporized by a single spot.* “Polymer-fume fever” is a syndrome of chest tightness, malaise, shortness of breath, fever and chills, and coughing lasting 24 to 36 hours after exposure, withConcern is then raised not out long-term sequelae. g~Lo only for the patient but also for the operating room personnel should the Xomed Laser-Shield II be used for laser surgery in anything but a very well ventilated area.” The cuff of the Laser-Shield II is not laser-resistant, but as has been reported previously, filling the cuff with saline should provide a heat sump to decrease the likelihood of ignition.“J3 The span of tube distal to the end of the protective wrapping and proximal to the cuff appears to be a design flaw. This area of the tube could easily be struck and ignited by the laser beam. When ignited, it sustains a blowtorch-type phenomenon when concentrations of 0, of 30% or more flow through the tube, although longer laser contact time is required when the percentage of 0, is decreased. Even though a blowtorch effect did not develop with 21% 0, flowing through the tube, the smaller external flame supported by the silicone and the laser could damage adjacent tissue. Also worrisome is the formation of friable pieces of charred silicone, which could be difficult to remove from the airway. While carrying the risk of introducing another foreign object into the airway, wrapping the unprotected span of tubing with laser-resistant tape or placing saline-soaked
*Personal communication with William L. Sprout, MD, E. I. DuPont De Nemours & Co., Haskell Laboratory, Newark, DE.
J. Clin. Anesth.,
vol. 4, March/April
1992
91
Original
Contributions
pledgets (pledgets are contained in the product package, and their use is recommended by the manufacturer) around this area could provide a greater margin of safety. I4 The simplest solution would be for the manufacturer to extend the laser-resistant wrapping over this vulnerable area and, preferably, under the entire cuff. We conclude that the wrapped portion of the new Xomed Laser-Shield II demonstrates significant CO, laser resistance at the settings described and would be acceptable for oral and pharyngeal laser surgery, but only in a very well ventilated area, out of concern for exposure to the products of pyrolysis of Teflon. The lack of protective wrap up to and under the cuff represents a laservulnerable area that imposes the risk of possible tube ignition and airway fire. Thus, the entire distal, unprotected portion of the tube is potentially unsafe against a misdirected CO, laser beam, especially during laryngeal or tracheal laser surgery. A change in design might reduce this risk.
Burgess G III, LeJeune F Jr: Endotracheal tube ignition during laser surgery of the larynx. Arch Otolaryngol 1979;105:561-2. Casey K, Fairfax W, Smith S, Dixon J: Intratracheal fire ignited by the Nd-Yag laser during treatment of tracheal stenosis. Chest 1979;84:295-6. Cozine K, Rosenbaum L, Askanazi J, Rosenbaum S: Laserinduced endotracheal tube fire. Anesthesiology 1981;55:583-5. Sosis M, Dillon F, Harwood T: A comparison of COP laser
J. Clin.
Anesth.,
6. 7.
8.
9. 10. 11.
12.
References
92
5.
vol. 4, March/April
1992
13.
14.
ignition of the Xomed, PVC and rubber tracheal tubes [Abstract]. CanJ Anaesth 1990;37:S87. Pashayan A, Gravenstein J, Cassisi N, McLaughlin G: The helium protocol for laryngotracheal operations with CO, laser: a retrospective review of 523 cases. Anesthesioloa 1988;68: 801-4. Schramm V, Mattox D, Stool S: Acute management of laserignited intratracheal explosion. Laryngoscope 198 I;9 1: 14 17-26. Sosis MB, Heller S: A comparison of special endotracheal tubes for use with the CO, laser [Abstract]. Anesthesiolog3j 1988; 69:A251. Lee K, Zapp J, Sarver J: Ultrastructural alterations of rat lung exposed to pyrolysis products of polytetrafluoroethylene (PTFE, Teflon). La6 Invest 1976;35: 152-60. Harris D: Polymer-fume fever. Lancet 1951;261:1008-11. Lewis C, Kerby G: An epidemic of polymer-fume fever.,IAMA 1965;191:103-6. Seidel W, Scherer K Jr, Cline D Jr, Olson A, Bonesteel J: Chemical, physical and toxicological characterization of fumes produced by heating tetrafluoroethene homopolymer and its copolymers with hexafluoropropene and perfluoro (propyl vinyl ether). Cke?n RPS Toxicol 1991;4:229-36. LqJeune F Jr, LeTard F, Guice C, Marice H: Heat sink protection against lasering endotracheal cuffs. Ann Otol Rhinol Imyngol 1982;91:606-7. Rubiano R, Chang J, Larson C, Lawler R, Rehkopf P: Precautions in use of a new endotracheal tube for laser surgery. Anesth Arlalg 185;64: 1037-8. Sosis MB: Saline soaked pledgets prevent CO2 laser induced tracheal tube cuff ignition [Abstract]. Can] Amesth 1990;37:S87.
*Resident, Department of Anesthesiology and Critical Care Medicine tClinica1 Associate Professor, Department of Anesthesiology and Critical Care Medicine; Chief Anesthesiologist, Eye and Ear Institute Pavilion SClinical Associate Professor, Department of Anesthesiology and Critical Care Medicine Klinical Instructor of Ophthalmology, partment of Ophthalmology
De-
Address reprint requests to Dr. Gonzalez at the Department of Anesthesiology, Eye and Ear Hospital of the University of Pittsburgh, 230 L.othrop Street, Pittsburgh, PA 15213, USA. Received for publication March 12, 1991; revised manuscript accepted for publication September 20, 1991. 01992 Butterworth-Heinemann J. Clin. Anesth. 4:89-92,
1992.
Eye and Ear Hospital
of the University
of Pitts-
Study Objective: To assess the resistance of a new endotracheal tube to penetration and ignition by a carbon dioxide (COJ laser at a clinically relevant power setting. Design: An unblinded, in vitro trial simulating clinical conditions. Setting: The operating room at a university medical center. Patients: None. Interventions: A CO, laser at 20W with a beam diameter of 1 mm was directed onto the Xomed Laser-Shield II at several points: both perpendicular and tangential to the portion of the tube covered by the protective wrap, to the unwrapped silicone tubing just proximal to the cuff, to the cuff filled with saline and methylene blue, and to the unwrapped silicone tubing distal to the cuff. Trials were performed with or without supplemental oxygen (OJ blown onto the study site and with a 6 Llmin flow through the tube containing one offour concentrations of 0, in O,-air admixtures: 21%, JO%, 4076, and 100%. Measurements and Main Results: Under all conditions, the laser did not penetrate the protective wrap, but the overlying polytetrafluoroethylene (Tejlon) sheet was vaporized to an area equal to the size of beam application. The cuff was penetrated b the laser within 5 seconds. The unprotected silicone portion of the tube was penetrated by the laser in a@roximately 5 seconds, and time to formation of a blowtorch phenomenon shortened with increasing the percentage of 0,flowing through the tube. Conclusions: The protective coating of the Xomed Laser-Shield II is laser-resistant, but the unprotected silicone proximal and distal to the cuff is laser-vulnerable and can, under certain conditions, promote a blowtorch phenomenon. This tube would be acceptable for use in oral and pharyngeal laser surgery, but we recommend its use only in well-ventilated areas, out of concern for exposure to the products of the @rolysis of Teflon, specifically the development of polymer-fume fever. Keywords: fire.
Laser,
carbon
dioxide;
tube,
endotracheal;
equipment
failure,
Introduction The carbon dioxide (CO,) laser is frequently used in the treatment of upper airway pathologies. Use of the laser near the endotracheal tube during airway surgery has been shown to carry the risk of endotracheal tube ignition and (PVC), red rubber, and the Xomed Laserairway fire. 1-3 Polyvinylchloride
J. Clin. Anesth.,
vol. 4, March/April
1992
89
Original Contributions Shield (Xomed Corp., Jacksonville, FL) endotracheal tubes have previously been shown to be combustible when struck by a CO, laser.4 Xomed has recently introduced the Laser-Shield II endotracheal tube (FZgure I). This tube is composed of clear, supple silicone surrounded by two thin wraps. The inner wrap is an overlapping spiral aluminum strip. The outer wrap consists of a seamless Teflon sheet. Distal to the protective wrap is approximately 1.0 cm of unprotected silicone tubing. Further distal is an unprotected high-volume, low-pressure cuff. The resistance of this tube to penetration and ignition by a CO, laser was tested at a clinically relevant power setting.
wrapped. The CO, laser was directed perpendicularly to these portions of the tube in separate trials with no 0, blown by it but with a 6 Limin flow through the tube containing one of four concentrations of 0, in O,-air admixtures: 21%, 30%, 40%, and 100% (0% air).
Results
A Coherent CO, laser (Model 45OXL, Coherent, Palo Alto, CA) was used. Its output was set at 20W in the continuous mode for up to 1 minute with a beam diameter of 1.0 mm. The Xomed Laser-Shield II (inside diameter 7.0 mm, outside diameter 10.6 mm) was placed on moist towels. The laser was aimed perpendicularly and tangentially to the long axis of the tube at several points along its body and at the cuff filled with saline and methylene blue. During testing, the laser was held at a constant distance from the endotracheal tube. This coincided with the laser’s focal length (approximately 5 cm) and yielded the smallest spot size. Trials involving laser application to the protective wrap were conducted in three environments: (1) in room air, (2) with 100% oxygen (0,) blown by the tube, and (3) with 100% 0, blown by the tube and 100% 0, flowing through the tube at 6 Wmin. The cuff, filled with saline and methylene blue, was tested without supplemental 0,. As shown in Figure I, approximately 1 cm of silicone tube proximal to the cuff is not covered by the protective wrap. The silicone tube distal to the cuff also is un-
With the COP laser aimed perpendicularly to the protective wrap, the Teflon vaporized within approximately 5 seconds, revealing the underlying aluminum wrap. The laser did not penetrate the aluminum wrap in room air or with added 0,. The Teflon wrap did not ignite, and essentially no smoke was observed. Only an area of Teflon the size of the laser’s spot was removed. With the CO, laser aimed tangentially to the protective wrap, the Teflon again vaporized within approximately 5 seconds. Again, the aluminum wrap was exposed, but even with the tube flexed, there was no evidence of penetration through the overlap of the strips. When the CO, laser was directed onto the cuff, it was punctured immediately, emitting a stream of the salinemethylene blue solution. When the laser was directed onto the unwrapped portion of the silicone tube proximal to the cuff, the tube was penetrated within approximately 5 seconds regardless of the concentration of 0, flowing through the tube. When this segment was tested with 100% 0, flowing through the tube, a vigorous blowtorch effect (Figure 2) resulted as the tube was penetrated. This did not extinguish until well after the 0, flow was discontinued. With 40% 0, flowing through the tube, despite penetration of the tube at approximately 5 seconds and a small flame on the outside of the silicone tube at the site of laser impact, a blowtorch effect did not develop until 15 seconds later. Again, this was sustained despite discontinuance of the laser and the supplemental 0, flow. With
Figure 1. The Xomed Laser-Shield II endotracheal tube. (A) The laser-resistant wrapping. (B) The unprotected silicone proximal to the cuff. (C) The cuff inflated with saline and methylene blue. (D) The unprotected silicone distal to the cuff.
Figure 2. The blowtorch effect demonstrated when the unprotected silicone proximal to the cuff was struck by the laser while supplemental oxygen was insufflated through the tube.
Materials and Methods
90
J. Clin. Anesth., vol. 4, March/April 1992
Xomed Laser-Shield
30% 0, flowing through the tube, there was penetration at 5 seconds and a small external flame, but a blowtorch effect did not develop for 25 seconds. Again, it continued after discontinuance of the laser beam and the 0, flow. Once the blowtorch effect was extinguished in all three of these trials, both the distal, unwrapped end of the tube (including the cuff) and a variable portion of the silicone tube underneath the protective wrap disintegrated into charred, friable fragments and dust (Figure 3). With 21% 0, (air) flowing through the tube, penetration occurred at approximately 5 seconds, and there was a small external flame during laser impact but no blowtorch effect. The silicone of this portion of the tube was moderately deformed by the end of the 60-second trial. The unwrapped silicone tube distal to the cuff yielded the same results when tested as did the segment of unwrapped silicone tube proximal to the cuff.
Discussion The CO, laser is being used increasingly often, especially in surgery of the upper airway, because of its precision, hemostatic properties, and reductions in postoperative edema and pain, as compared with conventional surgery. Accidental contact of the laser with the endotracheal tube is reported to be frequent,j and this occurrence carries the risk of an airway fire, which can have tragic consequences.” In view of the frequency with which the laser beam is misdirected onto the endotracheal tube, several methods have been tried and attempts have been made to develop a more laser-resistant tube. It has been shown that adhesive 3M #425 aluminum tape (3M, St. Paul, MN) and copper foil tape (Venture Tape Corp., Rockland, MD), when wrapped carefully in an overlapping fashion, can protect PVC and red rubber tubing from ignition by CO, and Nd-Yag lasers.7 One study has shown minimal advantage of the original Xomed tube over unwrapped red rubber or PVC tubes.” The Laser-Shield II is the most recent laser-resistant
Figure 3. The unprotected silicone after being extinguished.
II and the CO,, laser: Green et al.
tube developed by Xomed. It has the advantages of being flexible, thin-walled, and smooth on both the inner and outer surfaces. The thin outer Teflon wrap provides a smooth surface to prevent mucosal scraping that might otherwise occur if the underlying aluminum wrapping were to brush against tissue. Our study supports Xomed’s claims that the protective wrap is adequately laser-resistant (by withstanding perpendicular laser application) and adequately layered (as the tangential direction of laser application did not penetrate any of the overlaps of the stripping). The vaporization of the outer Teflon coating by the laser did not seem to cause any mechanical problems, although theoretically, exposure of the underlying aluminum wrap could reflect the laser beam onto normal tissue. In addition, if wrapping of the aluminum strips was defective under the overlying Teflon wrap, vaporization of the Teflon could allow penetration of the silicone tube and possible ignition. As the edges of the aluminum strips can be seen under the thin Teflon wrap, one should inspect the Laser-Shield II before use to ensure that the aluminum strips are properly overlapped. The pyrolysis products of Teflon are known to cause pulmonary edema and mucosal ulceration;8 however, these results would most likely require more Teflon to be heated than is present on the Xomed Laser-Shield II.* An entity known as “polymer-fume fever” also may occur as a result of exposure to the pyrolysis products of Teflon and in doses as small as that vaporized by a single spot.* “Polymer-fume fever” is a syndrome of chest tightness, malaise, shortness of breath, fever and chills, and coughing lasting 24 to 36 hours after exposure, withConcern is then raised not out long-term sequelae. g~Lo only for the patient but also for the operating room personnel should the Xomed Laser-Shield II be used for laser surgery in anything but a very well ventilated area.” The cuff of the Laser-Shield II is not laser-resistant, but as has been reported previously, filling the cuff with saline should provide a heat sump to decrease the likelihood of ignition.“J3 The span of tube distal to the end of the protective wrapping and proximal to the cuff appears to be a design flaw. This area of the tube could easily be struck and ignited by the laser beam. When ignited, it sustains a blowtorch-type phenomenon when concentrations of 0, of 30% or more flow through the tube, although longer laser contact time is required when the percentage of 0, is decreased. Even though a blowtorch effect did not develop with 21% 0, flowing through the tube, the smaller external flame supported by the silicone and the laser could damage adjacent tissue. Also worrisome is the formation of friable pieces of charred silicone, which could be difficult to remove from the airway. While carrying the risk of introducing another foreign object into the airway, wrapping the unprotected span of tubing with laser-resistant tape or placing saline-soaked
*Personal communication with William L. Sprout, MD, E. I. DuPont De Nemours & Co., Haskell Laboratory, Newark, DE.
J. Clin. Anesth.,
vol. 4, March/April
1992
91
Original
Contributions
pledgets (pledgets are contained in the product package, and their use is recommended by the manufacturer) around this area could provide a greater margin of safety. I4 The simplest solution would be for the manufacturer to extend the laser-resistant wrapping over this vulnerable area and, preferably, under the entire cuff. We conclude that the wrapped portion of the new Xomed Laser-Shield II demonstrates significant CO, laser resistance at the settings described and would be acceptable for oral and pharyngeal laser surgery, but only in a very well ventilated area, out of concern for exposure to the products of pyrolysis of Teflon. The lack of protective wrap up to and under the cuff represents a laservulnerable area that imposes the risk of possible tube ignition and airway fire. Thus, the entire distal, unprotected portion of the tube is potentially unsafe against a misdirected CO, laser beam, especially during laryngeal or tracheal laser surgery. A change in design might reduce this risk.
Burgess G III, LeJeune F Jr: Endotracheal tube ignition during laser surgery of the larynx. Arch Otolaryngol 1979;105:561-2. Casey K, Fairfax W, Smith S, Dixon J: Intratracheal fire ignited by the Nd-Yag laser during treatment of tracheal stenosis. Chest 1979;84:295-6. Cozine K, Rosenbaum L, Askanazi J, Rosenbaum S: Laserinduced endotracheal tube fire. Anesthesiology 1981;55:583-5. Sosis M, Dillon F, Harwood T: A comparison of COP laser
J. Clin.
Anesth.,
6. 7.
8.
9. 10. 11.
12.
References
92
5.
vol. 4, March/April
1992
13.
14.
ignition of the Xomed, PVC and rubber tracheal tubes [Abstract]. CanJ Anaesth 1990;37:S87. Pashayan A, Gravenstein J, Cassisi N, McLaughlin G: The helium protocol for laryngotracheal operations with CO, laser: a retrospective review of 523 cases. Anesthesioloa 1988;68: 801-4. Schramm V, Mattox D, Stool S: Acute management of laserignited intratracheal explosion. Laryngoscope 198 I;9 1: 14 17-26. Sosis MB, Heller S: A comparison of special endotracheal tubes for use with the CO, laser [Abstract]. Anesthesiolog3j 1988; 69:A251. Lee K, Zapp J, Sarver J: Ultrastructural alterations of rat lung exposed to pyrolysis products of polytetrafluoroethylene (PTFE, Teflon). La6 Invest 1976;35: 152-60. Harris D: Polymer-fume fever. Lancet 1951;261:1008-11. Lewis C, Kerby G: An epidemic of polymer-fume fever.,IAMA 1965;191:103-6. Seidel W, Scherer K Jr, Cline D Jr, Olson A, Bonesteel J: Chemical, physical and toxicological characterization of fumes produced by heating tetrafluoroethene homopolymer and its copolymers with hexafluoropropene and perfluoro (propyl vinyl ether). Cke?n RPS Toxicol 1991;4:229-36. LqJeune F Jr, LeTard F, Guice C, Marice H: Heat sink protection against lasering endotracheal cuffs. Ann Otol Rhinol Imyngol 1982;91:606-7. Rubiano R, Chang J, Larson C, Lawler R, Rehkopf P: Precautions in use of a new endotracheal tube for laser surgery. Anesth Arlalg 185;64: 1037-8. Sosis MB: Saline soaked pledgets prevent CO2 laser induced tracheal tube cuff ignition [Abstract]. Can] Amesth 1990;37:S87.