Introduction
Permissive hypercapnia is a mechanical ventilation strategy that tolerates the partial pressure of arterial carbon dioxide (PaCO2) above the normal range (35–45 mmHg). This approach may protect the lung from volutrauma and barotrauma by modulating small tidal volumes and low peak inspiratory pressures. In adult patients with acute respiratory distress syndrome, mechanical ventilation with a low tidal volume using permissive hypercapnia decreased the mortality and duration of mechanical ventilation.1-3However, in pediatric or newborn patients, findings from previous reports on the effectiveness of this strategy are inconsistent and do not provide enough evidence of the safety profile.4,5 In preterm infants, this approach is reported to cause a potential increase in the risk of intraventricular hemorrhage (IVH) due to permissive hypercapnia, which can result in neurodevelopmental impairment (NDI) because hypercapnia causes cerebral vasodilation and increases cerebral blood flow 6.Owing to controversial evidence on this topic, we conducted a systematic review and meta-analysis with an aim to examine the efficacy and safety of permissive hypercapnia, in comparison with the normocapnia strategy, in premature infants on mechanical ventilation.