Treatment with lucinactant, a peptide-containing synthetic lung surfactant, will be evaluated in young children with acute respiratory failure who require mechanical ventilation (life support), to determine if it is safe and if treatment with lucinactant will reduce the number of days a child needs mechanical ventilation (life support).

Determine the safety and tolerability of administration of a peptide-containing synthetic lung surfactant, lucinactant, in children up to two years of age and assess whether treatment with lucinactant can decrease the duration of mechanical ventilation in young children.

Inclusion Criteria:

• ≥ 38 weeks (corrected age) to 2 years (24 months)
• Intubated and mechanically ventilated (MV) for ≥ 6 hours and anticipated need for MV for ≥ 24 hours
• Persistent hypoxia
• Written informed consent

Exclusion Criteria:

• Mechanical Ventilation for > 48 hours
• Oxygenation index ≥ 25, if arterial line was avialable
• Pre-existing clinically significant or palliated/uncorrected cardiac disease adversely affecting cardiopulmonary function and gas exchange
• Neuromuscular disease or hypotonia
• Upper airway disease
• Baseline requirment for supplemental oxygen
• Untreated pneumothorax
• Off-label use of commercially available surfactant outside neonatal period
• History of prematurity and passive immunoprophylaxis with humanized monoclonal antibody
• Head injury with Glasgow Coma Scale < 8
• Brain death or impending brain death
• Do not resuscitate orders
• Cardiopulmonary resuscitation within 6 hours of meeting entry criteria
• Experimental therapy in which the intervention potentially affects respiratory outcomes
• Any transplant recipient
• Meconium aspiration syndrome
• Bordetella pertussis infection confirmed via laboratory tests and/or highly suspected pertussis infection

14 days from randomization or until resolution of adverse events.