RESUMO
In carbon dioxide (CO2) laser surgery of the larynx, the potentially dangerous combination of laser-induced heat in an oxygen-enriched atmosphere typically occurs when jet ventilation is used or due to an insufficiently blocked endotracheal tube. Until now, no limitations for safe oxygen concentrations or laser intervals have been established. The aim of this study was to investigate and quantify the factors that may contribute to an airway fire in laryngeal laser surgery. Fat, muscle and cartilage were irradiated with a CO2 laser at 2, 4, 6 and 8 W in five different oxygen concentrations with and without smoke exhaustion. The time to ignition was recorded for each different experimental setup. Fat burnt fastest, followed by cartilage and muscle. The elevation of laser energy or oxygen concentration reduced the time to inflammation of any tissue. The elevation of oxygen by 10 % increases the risk of inflammation more than the elevation of laser power by 2 W. Under smoke exhaustion, inflammation and burning occurred delayed or were even inhibited at lower oxygen concentrations. Lasing in more than 50 % oxygen is comparatively dangerous and can cause airway fire in less than 5 s, especially when laser energies of more than 5 W are applied. In equal or lower than 50 % oxygen, an irradiation interval of 5 s can be considered a comparatively safe time limit to prevent inflammation in laryngeal laser surgery. Smoke exhaustion should always be applied.
