The failure had a higher Apache II score (20.8 ± 2.9 versus 18 ± 1.9; p=0.01), a lower Glasgow score (14.37 ± 1.04 versus 15 ± 00; p=0.04) at admission and lower PaO2/FiO2 (128.4 ± 6.3 versus 174.3 ± 43; p=0.008), higher respiratory rate (31.6 ± 5.8 versus 26.1 ± 5.4; p=0.04) after 2 hours of NIPPV.