Early changes of pulmonary mechanics to predict the severity of bronchopulmonary dysplasia in ventilated preterm infants.

OBJECTIVES

To verify whether early pulmonary mechanics measurements are useful to predict subsequent bronchopulmonary dysplasia (BPD) and its severity.

METHODS

Pulmonary mechanics were studied at 3, 5, 7 and 10 days of age in 52 preterm infants with birth weight < 1250 g, affected by respiratory distress syndrome and ventilated for more than 72 h. Pulmonary function was assessed using a previously standardized method based on the measurement of airflow with a Fleisch OO pneumotachograph and airway pressure with a model P7D differential pressure transducer. At 28 days pulmonary outcome was classified into three groups: no BPD, mild BPD (oxygen dependency and hazy lung on X-ray) and severe BPD (oxygen dependency and Northway stage 3/4).

RESULTS

Of the 52 infants, 39 survived to 28 days: no BPD (11 infants), mild BPD (16 infants) and severe BPD (12 infants). The no-BPD group had significantly higher gestational age and birth weight, fewer males and a lower incidence of patent ductus arteriosus than both BPD groups, while no differences were detected between the BPD groups. Lung compliance was significantly higher in the mild-BPD group than in the severe-BPD group at 7 and 10 days of life (p < 0.01 and p < 0.001, respectively). The corresponding odds ratio confirmed that ventilated infants with lower lung compliance values had a significantly higher probability of developing severe BPD. Respiratory system resistance did not show any predictive value.

CONCLUSIONS

Our findings indicate that low lung compliance values determined on the 7th and 10th days of life are a reliable predictive tool of the severity of later BPD.