The purpose of the study is to determine whether additional surfactant(Infasurf) doses at 7 to 10 days of life time will improve lung function in premature infants, allowing a decrease in required oxygen concentration and ventilator settings.

Pulmonary surfactant is required for normal lung function. Preliminary data from previous trials suggest that more than half of chronically ventilated premature infants, greater than 1 week of age, have at least one episode of surfactant dysfunction, as measured in vitro, associated with a low surfactant protein B content. We propose to enroll premature infants less than 1250 gm birthweight, between days 5 and 21 of life who are intubated, mechanically ventilated, with a respiratory decompensation, defined as a severity score (mean airway pressure x FIO2) rising from a baseline of < 1.8 to > 3.5, sustained for > 24 hours. Infants will receive two doses of Infasurf surfactant, 12-24 hours apart, at the standard dose of 3 ml/kg. Primary outcome is the change in respiratory severity score at 72 hours post surfactant treatment compared to pre-treatment. Sample size is 31 infants, study duration is 3 years, and recruitment of study patients will occur at the Hospital of the University of Pennsylvania, and Women and Children's Hospital of Buffalo.

Inclusion Criteria:

• Less than 1250 gm birthweight
• Day 5-21 of life
• Intubated and mechanically ventilated, with respiratory decompensation, defined as the majority of daily severity scores (calculated every 6 hr from average of respiratory settings over 3-4 hour period) rising from baseline < 1.8, to > 3.5, sustained for >24hr. Note: Prior surfactant therapy at birth is neither an inclusion nor exclusion criterion.

Exclusion Criteria:

• Serious congenital malformations
• Life expectancy < 7 days from enrollment
• Patent ductus arteriosus at time of decompensation
• Pulmonary hemorrhage as cause of respiratory decompensation
• Active air leak syndrome at time of decompensation
• Postnatal steroid therapy for lung disease