Pathological changes of the three clinical types of laryngeal burns based on a canine model.

Objective: The study was designed to examine pathological changes of inhalational laryngeal burns of three clinical types: congestive, oedematous and obstructive.

Methods: A total of 18 healthy, male, adult Beagle dogs were randomly assigned to inhale hot dry air at room temperature (group C), 80°C (Group 1), 160°C (Group 2) or 320°C (Group 3) for 20min to induce inhalation injury. Each larynx was evaluated and scored based on the 'clinical scoring and typing system of laryngeal burns at early stage'. Tissue samples of the epiglottis, laryngeal vestibule, vocal folds and infraglottic cavity of the larynx were observed microscopically and evaluated based on a 'pathological scoring system'.

Results: Pathological changes of the larynxes of groups 1 and 2 were primarily characterised by slight atrophy of the mucosa and mild oedema of the submucosal tissues. Group 3 larynxes showed two distinct pathological changes: oedematous and atrophic types. The larynxes of the atrophic type showed lower clinical scores (29.5±0.7 vs. 44.3±2.1) but higher pathological scores (18.6±3.2 vs. 13.7±1.8) than the larynxes of the oedematous type.

Conclusion: Severe laryngeal burns could manifest as severe laryngeal oedema or atrophic change. The laryngeal burns of the atrophic type might suggest an unsatisfactory prognosis, although it had less risk of laryngeal obstruction at an early stage.