SURFACTANT PROTEIN A (SP-A) AND INFLAMMATORY CHANGES IN TRACHEAL ASPIRATES FROM VENTILATED NEWBORN INFANTS

Abstract

Bronchopulmonary dysplasia (BPD) following respiratory distress syndrome (RDS) has been correlated with persistent surfactant deficiency, a prolonged neutrophil influx and a decreased macrophage response in tracheal aspirate contents during the second half of the first week. These variables have not been studied comparing mild (type 1) and severe (type 2) forms of BPD. We prospectively measured SP-A, protein concentration, neutrophil and macrophage counts in 376 tracheal aspirate samples of 105 consecutively ventilated newborn infants in a longitudinal fashion. Fifty-eight patients had RDS (group A), 28 had pulmonary diseases other than RDS (group B) and 19 had no lung disease (group C). At day 1, RDS patients had lower levels of SP-A, protein, neutrophil and macrophage counts than infants of groups B and C. Among patients with RDS, survival without BPD was associated with an increase in tracheal SP-A concentration, neutrophil and macrophage count between day 1 and day 3 to 5; type 1 BPD was associated with an increase in SP-A without a cellular influx, and ‘poor outcome’ (type 2 BPD or nonsurvival at day 28) was associated with neither SP-A increase nor inflammatory response. Our findings confirm that a sustained increase in tracheal surfactant concentration and macrophage count is associated with RDS survival without BPD. However, contrary to current understanding, it is suggested that cure of RDS also requires a neutrophil inflammatory response, which is absent in type 1 and type 2 BPD patients and nonsurvivors. The latter two also fall to produce surfactant. Early treatment with corticosteroids may therefore not be appropriate for these infants.