After @ and @ hours of noninvasive respiratory support , the NIPPV group was superior to the NCPAP group with respect to the reduction in CO@ retention and improvement in oxygenation ( P < @ ) ; 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 FiO@ > @ , and significantly lower incidence of apnea and ventilator-associated pneumonia ( P < @ ) ; there were no significant differences in the incidence of air leak and abdominal distention between the two groups .