Endoscopic examination of the neonatal larynx at extubation: a prospective study of variables associated with laryngeal damage.

Despite postmortem and clinical studies, the etiological factors that determine why only a proportion of intubated neonates develop subglottic stenosis remain unclear. This prospective study was initiated to identify factors that were associated with laryngeal abnormalities secondary to intubation. Thirty neonates were examined at extubation by two independent observers blinded to the neonate's ventilatory history. Thirty-six possible prognostic indicators were recorded for each neonate. After screening by univariate (chi 2) analysis, 10 indicators were selected for further analysis. Of these 10 selected only two indicators showed an association with the laryngeal appearance. Active neonates had significantly more abnormalities in the supraglottis (P = 0.004) than those who were quiescent. Younger neonates had more abnormalities in the glottis though the significance level was marginal (P = 0.056). Other prognostic indicators, including birthweight, gestational age, duration of intubation and frequency of intubation, were not significantly related to laryngeal appearance. This study supports the hypothesis that the etiology of laryngotracheal stenosis is multifactorial, and has identified two possible etiological factors: age and neonatal activity. Neonatal activity has not been identified previously as an etiological factor. The contribution of individual factors may vary from one neonatal unit to another, as a result of variation in intubation, ventilation and extubation policy. This could explain the inconsistency in etiological factors identified by previous studies. It is therefore not yet possible to recommend a standard technique for the ventilation of premature neonates that would further reduce the incidence of laryngotracheal stenosis.