After 1 and 6 hours of noninvasive respiratory support , the NIPPV group was superior to the NCPAP group with respect to the reduction in CO2 retention and improvement in oxygenation ( P < 0.05 ) ; in addition , compared with the NCPAP group , the NIPPV group had significantly lower rates of second endotracheal intubation and second PS use , significantly shorter duration of invasive respiratory support and time of FiO2 > 0.21 , and significantly lower incidence of apnea and ventilator-associated pneumonia ( P < 0.05 ) ; there were no significant differences in the incidence of air leak and abdominal distention between the two groups .