Objective To study the first five inflations during the resuscitation of prematurely born infants and whether the infant's inspiratory efforts influenced the expired tidal volume.

Design Prospective observational study.

Setting Two tertiary perinatal centres.

Patients Thirty infants, median gestational age 30 (23–34) weeks.

Interventions The first five inflations delivered via a face mask and t-piece device were examined using respiratory function monitoring.

Main outcome measures Inflation pressures, inflation times and expiratory volumes were recorded and comparison made of inflations during which the infant made an inspiratory effort (active inflation) or did not (passive inflation).

Results Overall, the median expired tidal volume was 2.5 (0–19.8) ml/kg and was lower for passive (median 2.1 ml/kg, range 0–19.8 ml/kg) compared with active (median 5.6 ml/kg, range 1.2–12.2 ml/kg) inflations (ratio of geometric means 1.85, 95% CI 1.18 to 28%) (p=0.007). Overall, the median face mask leak was 54.5% and was lower for active (34.5%) compared with passive (60.7%) inflations (mean difference in % leak: 12.4%, 95% CI 0.9 to 24%) (p=0.0354). There was a significant positive correlation between the expiratory volumes and the inflation pressures (R2 between subjects 0.19, p=0.04) and a negative correlation between the expiratory tidal volumes and the face mask leaks (R2 between subjects=0.051, p<0.001), but there was no significant correlation between the inflation times and the expiratory tidal volumes.

Conclusion The expired tidal volume, inflation pressures and times during the first five inflations during resuscitation were variable. The expired tidal volumes were significantly greater if the infant inspired during the inflation.