Assessment of lung mechanics for the prediction and evaluation of pulmonary outcome in preterm infants

Background: The assessment of lung mechanics in preterm infants is of potential value for the early evaluation of lung disease and pulmonary outcomes. We aimed (i) to identify early predictors of respiratory outcome from lung mechanics obtained in week 1 of life in preterm infants below 32 weeks gestational age (GA) and (ii) to evaluate which clinical factors are associated with lung mechanics at 36 weeks postmenstrual age (PMA). Methods: Lung mechanics were assessed by the Forced Oscillation Technique using a mechanical ventilator (Fabian HFOi, Acutronic, Hirzel, Switzerland) that superimposed small amplitude oscillations (10 Hz) on a continuous positive pressure during spontaneous tidal breathing in unsedated infants. Reactance (Xrs), representing the elasticity of the respiratory system, was computed from flow and pressure data. Measurements were performed on days 2, 4, and 7 of life and at 36 PMA. Results: 61 infants (GA 29.2±1.9 w , weight 1225±376 g, respiratory support 24±21 d, supplemental O2 6 ± 15 d) were studied. There was a significant negative association between the duration of respiratory support and Xrs measured on days 2 and 7. A multilevel model including Xrs on days 2 and 7 and GA explained 54% of the variability in duration of respiratory support vs 38% explained by a model including only GA. Xrs at 36 weeks PMA was not significantly associated with either GA, birth weight, days of respiratory support or O2 requirement. Conclusion: Early assessment of Xrs has the potential to improve prediction of pulmonary outcome.