Objectives. We sought to determine factors that would predict the development of subglottic stenosis (SGS) and tracheomalacia (TM) in preterm infants. The utility of a semiquantitative measurement of airway dimensions was assessed in relation to signs of airway complications. We also sought to determine from a high-risk population of infants those likely to have abnormal findings identified by bronchoscopic examination.

Methods. Prospective airway endoscopy was performed for preterm infants who were intubated for 7 days or more or who demonstrated chronic oxygen needs beyond 28 days after birth and 36 weeks postconceptional age. Subjects were 117 preterm (less than 36 weeks' gestation) infants from two level III intensive care nurseries. Endoscopy was used to classify the type and degree of airway injury. Subglottic stenosis was defined subjectively and compared with an objective measurement using subglottic spatial relations described as a trans- subglottic/vocal cord ratio (TSG/VC). Clinical signs and symptoms and other risk factors were evaluated as significant predictors of SGS and TM, identified by bronchoscopy.

Results. Moderate or severe airway abnormalities were identified in 32 patients (27.3%); 13 with SGS, 17 with TM, and 2 with both. All but one infant with TSG/VC less than 0.83 had signs and symptoms of airway dysfunction. Variables more commonly found in patients with SGS included greater number of intubations, use of inappropriately large endotracheal tubes, and longer duration of intubation. Higher averaged mean airway pressure during the first week after birth and lower gestational age were clinical features associated with TM.

Conclusions. Flexible bronchoscopic evaluation of a high-risk population demonstrated a higher incidence of moderate or severe SGS or TM than previously suspected. Subglottic stenosis and TM appear to have different etiologies based on different factors associated with their development. The TSG/VC ratio correlated well with obstructive symptoms and may represent a means to quantitate clinically subglottic narrowing. Infants with chronic lung disease who have persistently elevated partial pressure of carbon dioxide, apnea, or phonation abnormalities are most likely to have airway abnormalities identifiable by bronchoscopy.

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