<p><b>BACKGROUND</b>Hypoxemic respiratory failure (HRF) is one of the most common causes for neonatal infants requiring aggressive respiratory support. Inhaled nitric oxide (iNO) has been established routinely as an adjunct to conventional respiratory support in developed countries. The aim of this study was to investigate effects of iNO in neonates with HRF in resource limited condition with no or limited use of surfactant, high frequency oscillatory ventilation (HFOV) and extracorporeal membrane oxygenation.</p><p><b>METHODS</b>A non-randomized, open, controlled study of efficacy of iNO was conducted over 18 months. Eligible term and near-term neonates from 28 hospitals with HRF (oxygenation index > 15) were enrolled prospectively into two groups as either iNO or control. Oxygenation improvement and mortality as primary endpoint were determined in relation with dosing and timing of iNO, severity of underlying diseases, complications and burden. Intention-to-treat principle was adopted for outcome assessment. Response to iNO at 10 or 20 parts per million (ppm) was determined by oxygenation in reference to the control (between-group) and the baseline (within-group).</p><p><b>RESULTS</b>Compared to 93 controls, initial dose of iNO at 10 ppm in 107 treated infants significantly improved oxygenation from first hour (P = 0.046), with more partial- and non-responders improved oxygenation with subsequent 20 ppm NO (P = 0.018). This effect persisted on days 1 and 3, and resulted in relatively lower mortalities (11.2% vs. 15%) whereas fewer were treated with surfactant (10% vs. 27%), HFOV (< 5%) or postnatal corticosteroids (< 10%) in both groups. The overall outcomes at 28 days of postnatal life in the iNO-treated was not related to perinatal asphyxia, underlying diseases, severity of hypoxemia, or complications, but to the early use of iNO. The cost of hospital stay was not significantly different in both groups.</p><p><b>CONCLUSIONS</b>With relatively limited use of surfactant and/or HFOV in neonatal HRF, significantly more responders were found in the iNO-treated patients as reflected by improved oxygenation in the first three days over the baseline level. It warrants a randomized, controlled trial for assessment of appropriate timing and long-term outcome of iNO.</p>