Diagnosis of tracheal injury in mechanically ventilated premature infants by flexible bronchoscopy. A pilot study. Flexible bronchoscopy (FB) is uniquely suited for the study of large airway lesions in the ventilated premature infant. However, no standardized clinical scoring system of distal tracheal injury exists and the adverse consequences of FB in ventilated premature infants are not well described. Using a prototype Olympus fiberoptic ultrathin bronchoscope with a directable tip and an outer diameter of 2.2 mm, we serially scored distal tracheal injury in conventionally ventilated premature infants on the basis of mucosal and obstructive changes observed at bronchoscopy. In addition, we prospectively evaluated the incidence of adverse cardiovascular and pulmonary effects during, immediately after, and within 1 h of FB. We performed 21 FBs in eight conventionally ventilated premature infants with birth weight of 1,239 +/- 438 g and gestational age of 30 +/- 3 weeks. The carina and mainstem bronchi were easily visualized in all infants using the prototype bronchoscope. During the first several days of life, moderate-to-severe distal tracheal mucosal injury occurred frequently, while moderate-to-severe obstructive injury occurred infrequently. Distal mucosal injury appeared to improve during the fourth week of life. Mild distal obstructive injury began to appear during the second week of life. Adverse consequences of FB observed in our patient population included transient hypoxemia and bradycardia during FB, changes in systolic blood pressure immediately and within 1 h after FB, and emesis immediately after FB. Serious adverse cardiovascular or pulmonary effects were not observed. We conclude that FB can be performed safely with appropriate monitoring and is a useful tool in the clinical assessment and serial evaluation of distal tracheal injury in ventilated premature infants. We speculate that moderate-to-severe distal tracheal mucosal injury may be associated with the development of later obstructive injury. On the basis of this preliminary study, further prospective investigations of tracheal injury in ventilated premature infants appear to be warranted. 