Rationale: Premature newborns frequently require manual ventilation for resuscitation during which lung injury occurs. Although surfactant protein (SP)-D regulates pulmonary inflammation, SP-D levels are low in the preterm lung. Commercial surfactants for treatment of respiratory distress syndrome do not contain SP-D.
Objectives: To determine whether addition of recombinant human SP-D (rhSP-D) to commercial surfactant influences lung inflammation in ventilated premature newborn lambs.
Methods: Prematurely delivered lambs (130 d gestation age) were resuscitated with 100% O(2) and peak inspiratory pressure 40 cm H(2)O for 20 minutes and then treated with Survanta or Survanta containing rhSP-D. Ventilation was then changed to regulate tidal volume at 8 to 9 ml/kg. At 5 hours of age lambs were killed for sample collection.
Measurements and main results: Sequential blood gas and tidal volume were similar in lambs treated with or without rhSP-D, indicating that lung immaturity and ventilatory stress used to support premature lambs were comparable between the two groups. Ventilation caused pulmonary inflammation in lambs treated with surfactant alone. In contrast, surfactant containing rhSP-D decreased neutrophil numbers in bronchoalveolar lavage fluid and decreased neutrophil elastase activity in lung tissue. IL-8 mRNA and IL-8 protein were significantly decreased in the +rhSP-D group lamb lungs, to 20% of those in controls. The addition of rhSP-D also rendered Survanta more resistant to plasma protein inhibition of surfactant function.
Conclusions: Treatment with rhSP-D-containing surfactant inhibited lung inflammation and enhanced the resistance of surfactant to inhibition, supporting its potential usefulness for prevention of lung injury in the preterm newborn.