A study of the premature neonatal airway.

Children born prematurely are now enjoying improved survival with advances in neonatology and ventilatory support. A study of upper airway size in specimens from 39 prematurely born children reveals 7.7% having a cricoid ring diameter greater or equal to the diameter of the tracheal rings. The more commonly expected relationship of the cricoid ring being smaller than the tracheal rings existed in the rest. This may be of importance in instrumentation or intubation of the airway in premature neonates. The gestational age was a better indicator of cricoid ring diameter than birth weight. From these findings a formula for reliably predicting the cricoid diameter is proposed, aiding the clinician in endotracheal tube or airway instrument selection. The combined lung weights were directly related to airway diameter irrespective of measurements of tracheal or cricoid rings. This has not been previously reported and would imply the existence of laryngo-tracheo-broncho-pulmonary hypoplasia in the premature infant.