Lung recruitment at birth does not improve lung function in immature lambsreceiving surfactant

Background: Iri mature animals with surfactant deficiency induced by lung l avage, the therapeutic effect of exogenous surfactant is enhanced by a lung recruitment maneuver. We then tested whether a lung recruitment maneuver a t birth immediately before surfactant treatment would improve lung function also in preterm lambs with surfactant deficiency due to immaturity. Methods: Ten newborn lambs with a gestational age of 127 days were randomiz ed to receive surfactant either before the first breath or immediately afte r a lung recruitment maneuver consisting of five sustained inflations of 8, 16 or 32 ml/kg. Functional residual capacity was measured by sulfur hexaflu oride washout, and inspiratory capacity as well as maximal compliance were obtained from a static expiratory pressure-volume curve after the lungs had been inflated to 35 cm H2O. In addition, blood gases were obtained. Measur ements were made at 15, 45, 175, 135, 170 and 230 min afterbirth. Post mort em histological examinations of the lungs were performed in a blinded fashi on. Results: The lung recruitment maneuvers did not improve oxygenation. Inspir atory capacity, static compliance and functional residual capacity at 4 h, as well as post mortem intrapulmonary air volume, had an inverse relation t o the size of inflations given at birth. There was also a negative correlat ion between size of inflations at birth and response to surfactant therapy, as assessed by lung microscopy. Conclusion: Lung recruitment at birth does not improve the response to surf actant in immature lambs, but may instead have an adverse effect on lung fu nction and morphology.