An animal model for endotracheal tube-related laryngeal injury using hypoxic ventilation

To explore whether hypoxic ventilation could allow a practical animal model of laryngotracheal injury secondary to endotracheal intubation.

Randomized controlled animal study.

Animal laboratory in a tertiary pediatric hospital.

Eight Sus scrofa piglets (15-18 kg) were anesthetized and intubated for 4 hours, with a 6-mm cuffed endotracheal tube. They were randomly assigned to either constant hypoxic ventilation (oxygen saturation under 70%) or nonhypoxic ventilation. Endotracheal tube cuff pressure was manually controlled and maintained at a constant level. After 4 hours, fluorescein dye was administered intravenously to highlight areas of hypoperfusion within the larynx. The animals were euthanized at the end of the procedure, and the larynx and trachea were harvested for gross and histological examination. The pathologist was blinded to the ventilation group. The severity of laryngeal injury was graded between 0 and 4 by a senior pathologist.

The experiment protocol was successfully completed in all animal subjects. The animals undergoing hypoxic ventilation showed a significantly higher median injury grade than the nonhypoxic animals (2 vs 1, respectively; P = .003). Damage was significantly worse in the hypoxic group at all anatomical sublevels.

Endotracheal tube-related laryngeal injury was demonstrated after only 4 hours of intubation using this animal model, and hypoxic ventilation increased the severity of injury. This study therefore provides an animal model that may be suitable for future investigation and prevention of intubation injury.