Results
Of the 24 consecutive neonates treated with both HFOV and INO, 18 		 (75%) responded and 6 (25%) did not respond to the treatment. Three neonates 		 died in the responding group, while all the non-responders died (P 		 =0.0001). The survival rate was 62.5% among all neonates.
The underlying diseases of the responders and non-responders are 		 depicted in Table 1. In addition to severe PPHN, six 		 neonates had birth asphyxia, 13 had MAS, three had congenital diaphragmatic 		 hernia (CDH) and two had RDS. Of the 13 neonates with MAS, 12 responded to INO, 		 while none of the infants with CDH responded to INO therapy.
Inhalation of NO significantly decreased OI (P < 0.0001) 		 and improved the a/A ratio (P < 0.0001) within the first 2 h of INO 		 therapy in 61.1% of the responders, and the remaining responded gradually 		 during the INO treatment. However, OI and a/A ratio remained almost the same 		 throughout the treatment in the non-responders and the non-survivors (Tables 		 2 and 3). Four of the responders 		 (two with MAS and two with RDS) became INO-dependent and required 		 phosphodiesterase inhibitor (dipyridamole) to wean them from INO. Tolazoline 		 was unsuccessfully attempted in two neonates in the referring hospitals. 		 Methemoglobin and nitrogen dioxide were maintained below 5% during INO therapy. 		 The average age when INO was started was 2.6 days (range 1–11 days). The mean 		 duration of INO used in all neonates was 4.6 days (range 1–10 days). Three 		 neonates responded to INO but died of other causes. The first neonate had 		 severe intracranial hemorrhage, Klebsiella pneumoniae sepsis, renal 		 failure and, consequently, brain death. The second neonate had Escherichia 		 coli sepsis and interstitial lung disease. The lung biopsy revealed a 		 diffuse alveolar damage. The third neonate developed multiple pneumatoceles in 		 both lungs and the lung biopsy showed proliferative phase of diffuse alveolar 		 damage. Subsequent lung tissue culture was positive for 		 methicillin-resistant Staphylococcal aureus.
Table 1  The underlying diseases of all infants
Table 2  Comparison between responders and non-responders  OI, oxygenation index; a/A, arterial/alveolar oxygen ratio; INO, 				inhalational nitric oxide. All values shown as mean ± SEM; 				*P < 0.05.
Table 3  Comparisons between survivors and non-survivors  OI, oxygenation index; a/A, arterial/alveolar oxygen ratio; INO, 				inhalational nitric oxide. All values shown as mean ± SEM; *P < 0.05.