Selection Criteria for the systematic review
This systematic review included studies that compared the effectiveness
of the two respiratory strategies (permissive hypercapnia versus
targeting normocapnia) on mortality and morbidity in preterm infants on
mechanical ventilation. All published randomized controlled trials
(RCTs), non-RCTs, interrupted time series, cohort studies, case-control
studies, and controlled before-and-after studies were eligible for
inclusion in this review. Unpublished RCTs were eligible if sufficient
information on risk of bias assessment was obtained. No language
restrictions were applied, but the selected articles were required to
have an English abstract. This systematic review excluded studies
without sufficient data regarding the outcomes to be summarized,
duplicate studies or data, and animal studies. Studies were excluded if
they assessed only infants on noninvasive mechanical ventilation without
intubation (e.g., those on continuous positive airway pressure
[CPAP] or high-flow nasal cannula). Six important outcomes were
selected a priori for assessment in this systematic review: (1)
mortality at discharge from the neonatal intensive care unit (NICU) or
at postmenstrual age of 36 weeks; (2) bronchopulmonary dysplasia (BPD),
defined as oxygen use or respiratory pressure support [e.g., CPAP,
high-flow nasal cannula at a rate of >2 L/min] at
postmenstrual age of 36 weeks; (3) a composite outcome of death or BPD;
(4) severe IVH (Grades III or IV of Papille’s classification);7 (5) cystic periventricular leukomalacia (cystic
PVL); (6) necrotizing enterocolitis (NEC; Bell’s criteria ≥2a)8; and (7) NDI (cerebral palsy, cognitive deficit, and
vision or hearing impairment).