This pilot study was a randomized, placebo-controlled, clinical trial to test the safety of using the intravenous form of Prostaglandin E1 (PGE1) in an inhaled form for treatment of hypoxemic respiratory failure in term newborns. The study planned to enroll 50 infants diagnosed with hypoxemic respiratory failure at nine NICHD Neonatal Research Network sites, and randomly assign them to receive one dose over a 72-hour period of either high concentration PGE1 (300 ng/kg/min), low concentration PGE1 (150 ng/kg/min), or placebo (normal saline, the diluent for the drug). In addition to determining the safety, optimal dose, and duration of the therapy, this pilot trial planned to evaluate the feasibility of conducting a larger, multi-center randomized, blinded placebo-controlled trial.