Aims The goal of the study was to compare preductal SpO₂ in the first 10 min after birth in preterm infants treated with non-invasive continuous positive airway pressure (CPAP) and air with a published nomogram of preductal SpO₂ in preterm infants who received no medical intervention, and to examine gender differences.

Design Prospective observational study.

Patients and methods We enrolled infants of ≤32 weeks gestation who were spontaneously breathing with heart rate >100 bpm, and treated with face mask CPAP and air during postnatal stabilisation. SpO₂ limits were targeted at ≥75% at 5 min and ≥85% at 10 min and heart rate at >100 bpm. FIO₂ was titrated against SpO₂. Preductal SpO₂, airway pressure and FIO₂ were recorded with a data acquisition system from birth until stabilisation. Babies receiving supplemental oxygen (>21%), positive pressure ventilation, were intubated and/or received chest compressions or drugs were excluded.

Results Measurements were obtained in 102 babies with median gestational age of 29 (range: 24–31) weeks. Median SpO₂ was significantly higher in the observational group than in the reference range at 3 min (82% (CI 71% to 85%) vs 76% (CI 67% to 83%); p<0.05), at 4 min (87% (CI 81% to 90%) vs 81% (CI 72% to 88%); p<0.05), at 5 min (92% (CI 88% to 95%) vs 86% (CI 80% to 92%); p<0.05), at 6 min (94% (CI 90% to 97%) vs 90% (CI 81% to 95%); p<0.05), at 7 min (95% (CI 92% to 97%) vs 92% (CI 85% to 95%); p<0.05), at 8 min (96% (CI 93% to 98%) vs 92% (CI 87% to 96%); p<0.05) and at 9 min (97% (CI 92% to 99%) vs 93% (CI 87% to 96%); p<0.05). Female babies achieved targeted SpO₂ significantly earlier than male babies.

Conclusions Preterm babies receiving CPAP and air and especially female subjects achieve reference oxygen saturation more rapidly than spontaneously breathing preterm babies without respiratory aid.