BOOST-II UK

Which oxygen saturation level should we use for very premature infants? A randomised controlled trial.

Trial started: 2007  Trial ended: 2014 

Summary

Objectives

To compare the effects of targeting a lower oxygen saturation range (85–89%) or a higher range (91–95%) on death or disability at 2 years in infants born before 28 weeks' gestation.

Methods

Two randomised controlled trials conducted in Australia and the United Kingdom involving infants born before 28 weeks' gestation. Infants were randomised to a target oxygen saturation range of either 85–89% or 91–95%. During the trials, the oximeters were revised to correct a calibration-algorithm artifact.

Outcome measures

Primary outcome: Death or disability at 2 years' corrected age.

Results

A total of 1135 infants were enrolled in Australia and 973 in the United Kingdom before recruitment was stopped following an interim analysis that identified increased mortality at 36 weeks' corrected gestational age. In the Australian trial, death or disability occurred in 45.0% of infants in the lower-target group and 39.8% in the higher-target group (adjusted relative risk 1.12, 95% confidence interval 0.98 to 1.27; p = 0.10). In the UK trial, using data from infants monitored with revised oximeters, death or disability occurred in 50.5% of infants in the lower-target group and 45.9% in the higher-target group (adjusted relative risk 1.10, 95% confidence interval 0.97 to 1.24; p = 0.15).

In post hoc combined analyses including all oximeters, death or disability occurred in 48.1% of infants in the lower-target group and 43.1% in the higher-target group (relative risk 1.11, 95% confidence interval 1.01 to 1.23; p = 0.02), and death occurred in 21.2% and 17.7%, respectively (relative risk 1.20, 95% confidence interval 1.01 to 1.43; p = 0.04). Among infants monitored using revised oximeters, death occurred in 24.5% of the lower-target group compared with 16.9% of the higher-target group (relative risk 1.45, 95% confidence interval 1.16 to 1.82; p = 0.001).

Conclusions

Targeting an oxygen saturation range of 85–89%, compared with 91–95%, did not result in a statistically significant increase in death or disability at 2 years within either trial individually. However, post hoc combined analyses showed increased risks of death or disability and of death alone with the lower oxygen saturation target.

Summary based on: Tarnow-Mordi W, Stenson B, Kirby A, et al. Outcomes of Two Trials of Oxygen-Saturation Targets in Preterm Infants. New England Journal of Medicine. 2016;374(8):749–760. https://doi.org/10.1056/NEJMoa1514212.