Reduced oxygen-saturation targets in preterm infants results in significantly higher rates of death and disability at age two years, a combined analysis of UK and Australian trials finds.

The Australian Benefits of Oxygen Saturation Targeting (BOOST) II trials enrolled over 2,000 infants born before 28 weeks gestation and randomly assigned them to either lower (85% – 89%) or higher (91% – 95%) oxygen saturation.

The Australian arm led by Professor William Tarnow-Mordi from the neonatal medicine at Sydney Medical School, University of Sydney reported death or disability in 45% of infants in the lower target group, compared with 39.8% in the higher target group.

Similarly in the UK arm death or disability occurred in 50.5% of infants in the lower target group compared to 45.9% in the higher target group.

These findings were not statistically significant; however, when the data was combined the researchers found significant differences between the groups.

The lower-target group had an 11% higher risk for death or disability (RR, 1.11; 95% CI, 1.01 – 1.23; P = .02) and a 20% higher risk for death (RR, 1.20; 95% CI, 1.01 – 1.43; P = .04) than the higher-target group.

“Targeting an intermediate oxygen-saturation range, such as 87% to 93%, vs. a higher range is an untested practice that may increase mortality, because current oximeters permit increasingly disproportionate exposure to hypoxemia as oxygen saturation decreases to below 93%,” Tarnow-Mordi and colleagues wrote in the research that was published in the NEJM.

“At present, the most rigorously evaluated evidence for policy is that targeting an oxygen saturation of 91% to 95% is safer than targeting an oxygen saturation of 85% to 89%,” they concluded.