Surfactant dysfunction may contribute to the development of bronchopulmonary dysplasia (BPD) in persistently ventilated preterm infants. The investigators conducted a multi-center, randomized, blinded pilot study to assess the safety and efficacy of late administration of surfactant (Calfactant - high in protein B) in combination with prolonged inhaled nitric oxide in preterm infants \< 1000 grams birthweight (BW). Calfactant is one of several types of exogenous surfactant. Calfactant has the highest % of surfactant protein B of the different types.
