To the Editor:—

We read with interest the case report by Chee and Benumof 1and their comments on the advisability of removal of the burned endotracheal tube.

The decision of whether to extubate a particular patient after a fire in an endotracheal tube must include consideration of the risk/benefit ratio. The danger of extubating a patient when reestablishment of the airway is judged to be difficult is considerable. But the risk of commitment to a tube already involved in a fire is also considerable. Before reventilation of the patient, it is absolutely imperative first to assure that the intraluminal flame 2has been totally extinguished. If not, a severe intraluminal and free-end flame can ignite when oxygen is resupplied, and further patient damage will occur. To evaluate the risk of not removing an endotracheal tube involved in a fire, one must also consider the effect of these flames on the integrity of the tube.

Because polyvinyl chloride endotracheal tubes require an oxygen-enriched atmosphere to sustain combustion, 3an extraluminal surface fire can exist when the extraluminal surface is exposed to an oxygen-enriched atmosphere.

An intraluminal fire can exist when the intraluminal surface is exposed to an oxygen-enriched atmosphere. If the tube is ignited while oxygen flows through the tube, the intraluminal fire that develops spreads toward the oxygen flow.

The products of complete oxidation of polyvinyl chloride produced by the intraluminal flame include carbon dioxide, water, and hydrogen chloride. Because oxidation is often incomplete, products of incomplete oxidation are also produced, including carbon monoxide and hydrogen. These products are present in the gases flowing downstream from the intraluminal flame. Notably, because oxidation is often complete, the downstream gases contain no oxygen. Also included in the downstream gases are products of pyrolysis of polyvinyl chloride, such as short and long carbon chains and carbon rings. Some of the downstream gases are capable of further oxidation and can ignite on reaching an oxidizer such as ambient or alveolar air, producing a free-end flame.

If the intraluminal oxygen available exceeds the fuel supply of polyvinyl chloride, or conversely, if the available fuel supply is less than the available oxygen, the intraluminal flame becomes anchored at the distal end of the tube.

The true significance of the hypothesis of the sparing effect on the lung by the “venting” of the flame via  the tracheostomy stoma is speculative and requires further investigation.

In addition, safe clinical practice dictates against the concomitant use of an oxygen-enriched atmosphere and the proximate use of the electrosurgical unit in the presence of a polyvinyl chloride endotracheal tube. It must be reinforced that nitrous oxide contributes to the oxygen-enriched atmospheres.

Although our studies demonstrate that the intraluminal flame will extinguish on cessation of intraluminal gas flow, if the decision is made that the risk of extubating is greater than the benefit of not extubating, we strongly support lavage of the intraluminal surface with sufficient water or saline. The sufficient amount will vary with the circumstances. However, to be absolutely certain, direct visual inspection is probably necessary to assure that all potential reignition points are extinguished. Because that is impractical and uncertain, it is advisable initially to reventilate with air. Reventilation with oxygen may rekindle an intraluminal and free-end flame from possible nascent smoldering combustion.

Chee WK, Benumof JL: Airway fire during tracheostomy: Extubation may be contraindicated. A NESTHESIOLOGY 1998; 89: 1576–8
Wolf GL, Sidebotham GW, Stern JB: Intraluminal flame spread in tracheal tubes. Laryngoscope 1994; 104: 874–9
Wolf GL, Simpson JI: Flammability of endotracheal tubes in oxygen and nitrous oxide enriched atmosphere. A NESTHESIOLOGY 1987; 67: 236–9