Inclusion and exclusion criteria
All included studies met the following criteria: (1) randomized controlled trial (RCT) or cohort study; (2) the intervention group was given NHFOV and the comparison group was given NIPPV as initial respiratory support or post-extubation respiratory support; and (3) at least one of the following outcome parameters was reported. The primary outcome was the rate of intubation or reintubation, indicating the need for IMV after non-invasive respiratory support or extubation. The secondary outcomes included: (i) the duration of non-invasive ventilation, (ii) total oxygen therapy time, (iii) length of hospital stay (LOS) , (iv) blood gas analysis indices (PaO2 and PaCO2 levels and SpO2/FiO2 ratios) 1 h and 24 h after non-invasive respiratory support and (v) adverse outcomes, including air leak, abdominal distension, BPD, intraventricular hemorrhage (IVH), retinopathy of prematurity (ROP), necrotizing enterocolitis (NEC), nasal injury, periventricular leukomalacia, pneumothorax (PNX) and apnea.
The exclusion criteria were: (1) non-clinical studies, (2) research protocols, (3) duplicated reports or secondary or post-hoc analyses of the same study population or (4) lack of sufficient information related to baseline or outcome data.