Airway fires pose a risk during laser microlaryngoscopy, and neurosurgical cotton patties, used to prevent tissue injury from stray laser beams, are a potential ignition source. Using a configuration approximating clinical practice, we experimentally assessed the relative impact of changing different ‘fire triad’ components on the occurrence of airway fires, in order to better inform patient care.

The relative effects of wet vs dry neurosurgical patties, oxygen concentration and laser power setting on the patty ignition time were studied in a cadaveric porcine model. Data were analysed using t-test and two-way analysis of variance.

Dry patties ignited after 2.3 ± 1.2 seconds (average ± standard deviation) of continuous 5 W laser fire at 50 per cent oxygen concentration, compared with 63.9 ± 27.8 seconds for wet patties under the same laser and oxygen settings (p < 0.0001). There was a statistically significant reduction in the time to patty ignition when laser power settings were increased from 5 to 7.5 W, but no further reductions occurred when the power was further increased to 10 W (p < 0.05; Tukey test for multiple comparisons; two-way analysis of variance). There was no significant reduction in the time to ignition between oxygen concentrations of 50 and 75 per cent, but the time to ignition fell significantly when the oxygen concentration was further increased to 100 per cent.

We suggest that surgical patties should always be soaked and should be used for relatively short periods, in order to prevent drying. If at all possible clinically, prolonged laser use at high power settings and ventilation with 100 per cent oxygen should be avoided.