Search methods and strategy
A literature search was performed in the following databases from their
inception to January 3, 2022: MEDLINE, Embase, Cochrane Central Register
of Controlled Trials (CENTRAL), and Cumulative Index to Nursing and
Allied Health Literature (CINAHL). A manual search of the reference
lists of the review articles on this topic was conducted. Trial
registrations of ClinicalTrials.gov, EU Clinical Trials Register, and
Australian New Zealand Clinical Trials Registry were searched to check
for ongoing trials. The literature search strategies included the
following terms: population (newborn, infant or neonate and low birth
weight, LBW, VLBW, ELBW or preterm, premature) and intervention
(hypercapnia, carbon dioxide, CO2). The full search
strategy used for MEDLINE is presented in the supplementary material
(Supplemental Table A).