Kinsey 1956.

Methods	Central telephone randomization ensured adequate allocation concealment. The ratio of experimental group : control group was 2:1 in first 3 months of enrolment. Following that, 574 infants were consecutively allocated to the experimental group and had no concurrent controls. These infants are not included in this review. The number of infants excluded before randomization is not known. Randomization was stratified by birth weight categories and institution. The intervention was not blinded and the blinding of outcome assessments is unclear. The follow‐up rate for outcome measures was 97%. There were detailed power calculations.
Participants	212 infants with BW <1500g who survived to 48 hours. Enrolment commenced in July 1953. The mean BW in the two groups was 1242g (restricted) and 1234g (liberal) respectively. Infants were followed until 2.5 months of age.
Interventions	Experimental group (restricted oxygen): received oxygen only if clinical condition indicated and maximum FiO2 permitted was 0.5. Control group (liberal oxygen): received supplemental oxygen in excess of 50% for a minimum of 28 days and were then weaned over 3 days.
Outcomes	Vascular RLF (any stage) in survivors Vascular RLF (severe stages) in survivors Cicatricial RLF (any grade) in survivors Cicatricial RLF (severe grades) in survivors Mortality (48 hours‐40 days) Of the 144 infants assigned to the restricted oxygen group, 36 died before 40 days and 4 were lost to follow‐up. There were 15 deaths and no losses to follow‐up among the 68 infants allocated to the liberal oxygen group.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Adequate sequence generation?	Low risk	Block and stratified randomization.
Allocation concealment?	Low risk	Central telephone randomization.
Blinding? All outcomes	High risk	Blinding not stated.
Incomplete outcome data addressed? All outcomes	Low risk	Follow‐up was 97%. Reasons were given for loss to follow‐up (e.g. death)
Free of selective reporting?	Low risk	There were 21 tables and 8 appendices tables of results and measured data reporting various analyses of the outcome data and breakdown of the characteristics of the populations from all the participating centres.