Table 1 Categories of randomised controlled trials of inhaled nitric oxide in preterm infants.

Category	Description	RCTs	References
Early prophylactic treatment	Treatment of babies requiring mechanical ventilation or nasal CPAP, <72 h of age and at risk of death/BPD, irrespective of the severity of respiratory disease	2	1,11
Early rescue treatment	Treatment of babies with established respiratory failure in the first week of life, based on severity of respiratory disease	5	3, 12–15
Late treatment	Treatment of babies requiring ventilation or nasal CPAP ⩾72 h and at risk of death/BPD, irrespective of the severity of respiratory disease	2	2, 16

BPD, bronchopulmonary dysplasia; CPAP, continuous positive airway pressure, RCT, randomised controlled trial.