The PaCO ( 2 ) ( mmHg , 1 mmHg = 0.133 kPa ) , oxygen index ( OI ) at 12-24 h , and FiO ( 2 ) at 24 h post-ventilation in BiPAP and SBiPAP groups were lower than that in NCPAP groups with significant difference ( 44 9 and 45 9 vs. 50 9 , 2.76 0.96 and 2.79 0.60 vs. 3.24 0.72 , 0.34 0.10 and 0.35 0.07 vs. 0.39 0.07 ; F = 4.456 , 5.146 and 4.123 ; P = 0.014 , 0.007 and 0.019 , respectively ) .