To evaluate the effectiveness of intratracheal administration of synthetic protein-free pulmonary surfactant in neonates at risk of developing RDS or with established RDS.

Comparison 1: Does intratracheal administration of synthetic protein-free pulmonary surfactant compared to air placebo or normal saline or no treatment reduce mortality and other complications of preterm birth in preterm infants at risk of developing RDS?

Comparison 2: Does intratracheal administration of synthetic protein-free pulmonary surfactant compared to air placebo or normal saline or no treatment reduce mortality and other complications of preterm birth in preterm infants with clinical and/or radiologic evidence of respiratory distress syndrome requiring assisted ventilation?