Pulmonary function in newborns after repair of congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is associated with pulmonary hypoplasia that limits survival, but the nature and extent of pulmonary dysfunction in neonates with CDH have not been studied. We performed pulmonary function tests (PFTs) in eight intubated infants who survived neonatal repair of CDH (wt, 3.33 +/- 0.15 kg; age, 20.1 +/- 2.7 d; mean +/- S.E.M.). PFTs obtained from six full-term infants (wt, 3.56 +/- 0.15 kg; age, 25.0 +/- 3.3 d) with no respiratory illness served as controls. The deflation flow-volume curve technique produced maximum expiratory flow-volume (MEFV) curves, giving reproducible measurements of forced vital capacity (FVC) and maximal expiratory flow at 25% of FVC (MEF25). Respiratory system compliance (Crs) and resistance (Rrs) were obtained with a modified passive mechanics technique. In seven of eight infants PFTs were repeated after nebulized bronchodilator (0.1% isoetharine). In neonates surviving CDH repair, as compared to those with normal lung function, FVC was significantly reduced (20.78 +/- 3.32 vs. 39.83 +/- 3.30 mL.kg-1, P less than 0.05). MEF25 was also markedly reduced (20.78 +/- 3.32 vs. 39.83 +/- 3.30 mL.kg-1.s-1, P less than 0.05), indicating lower airway obstruction. After administration of nebulized bronchodilator, PFTs showed significant increases from control values in both FVC (15.9%) and MEF25 (200%) without changes in Crs and Rrs. These findings indicate that neonates with CDH have restrictive lung defects, reflecting hypoplasia. After surgical repair and mechanical ventilation airway reactivity develops, primarily in smaller airways, and this may complicate the postoperative course.