• Methemoglobin level [ Time Frame: at baseline then every hour of treatment ] [ Designated as safety issue: Yes ]
• Alveolar-arterial oxygen gradient and ratio [ Time Frame: after 1 hour of treatment ] [ Designated as safety issue: No ]

The purpose of this pilot study is to evaluate whether administration of nitric oxide (NO)gas by oxygen hood at 20 ppm significantly increases PaO2, as compared to placebo gas (oxygen), within one hour of initiation and with no significant adverse effects.

It is possible that administration of inhaled NO to neonates with abnormal gas exchange earlier, rather than later as a rescue therapy in a moribund state, might accelerate the transition of the circulation from the fetal to neonatal physiology and improve oxygenation. This may in turn decrease the need for mechanical ventilation, its associated morbidity and perhaps even ECMO.

This study is designed as a pilot study to evaluate the physiologic efficacy (rather than effect on clinical outcomes) of NO administered by hood in improving oxygenation of neonates with elevated A-a DO2.

• Lung Disease
• Hypoxemia
• Respiratory Acidosis

• Drug: nitric oxide for inhalation
• Drug: Oxygen

• Experimental: Nitric Oxide for Inhalation
• Placebo Comparator: oxygen

Inclusion criteria:

• Gestational age >34 completed weeks (>=35)
• Age <48 hours
• A-a DO2 400 to 600, on two post-ductal arterial blood gases one hour apart, while on 100% O2 by oxygen hood
• Post-ductal arterial access
• Admitted to The University of Alabama Birmingham Regional NICU

Exclusion criteria:

• Cardiac disease (structural disease with right to left or mixing lesions), not including patent ductus arteriosus (PDA) or patent foramen ovale (PFO)
• Rapid deterioration requiring mechanical ventilation before entry into the study
• Major malformations
• Major neurologic or metabolic disorder or other illness leading to hypoventilation and hypercarbia