Hypercapnia and the neonate

‘Permissive hypercapnia’ is a familiar term in neonatal intensive care, given the widespread adoption of low‐tidal‐volume ventilation strategies applied with the goal of decreasing respiratory morbidity. Recent evidence suggesting that hypercapnic acidosis may itself have protective effects on the lung and other organs has led to the coining of a new phrase, ‘therapeutic hypercapnia’, which also encompasses the use of supplemental inspired CO2.