Inhaled Nitric Oxide for Preterm Infants With Severe Respiratory Failure

Inclusion Criteria * Any infant with a birth weight 401 - 1500 grams and \< 34 weeks gestational age with an OI (mean Paw x FiO2 x 100/PaO2) \> 10 on two consecutive blood gases at least 30 minutes apart, but no more than 12 hours apart. or * Infants \> 1500 grams and \< 34 weeks gestational age will be entered in the Larger Preemie Pilot Study if they have an OI greater than or equal to 15 on two consecutive blood gases at least 30 minutes apart, but no more than 12 hours apart. * Infants requiring assisted ventilation with a diagnosis of RDS/HMD, pneumonia and/or sepsis, aspiration syndrome, idiopathic pulmonary hypertension, or suspected pulmonary hypoplasia associated with PROM and/or oligohydramnios. * Greater than or equal to 4 hours after one dose of surfactant. * Less than or equal to 120 hours of age. * All infants must have an indwelling arterial line. Exclusion Criteria * Any infant in whom a decision has been made not to provide full treatment (e.g. chromosomal anomalies or severe birth asphyxia). * Known structural congenital heart disease, except patent ductus arteriosus and atrial-level shunts. * Infants with any major abnormality involving the respiratory system such as congenital diaphragmatic hernia, tracheoesophageal fistula or cystic fibrosis. * Any bleeding diathesis considered to be clinically significant or thrombocytopenia with platelet count \< 50,000. * Prior enrollment into a conflicting clinical trial such as the Neonatal Network Surfactant CPAP trial.Inclusion Criteria