Background Positive pressure ventilation (PPV) remains the cornerstone of respiratory support after birth. Effectiveness of PPV in the DR may be compromised by leak, obstruction and inappropriate tidal volume (V_T) delivery.

Aim Describe leak, obstruction and V_T during spontaneous breathing amongst preterm infants transitioning in the DR and interaction of these breaths with mask ventilation.

Methods Patients were enrolled from the control arm of a randomised trial investigating the use of a respiratory function monitor (RFM) in the DR; infants < 32 weeks who were stabilised by paediatric trainees unaware of RFM data were included. During spontaneous breathing on mask continuous positive airway pressure (CPAP) and the delivery of PPV, airway pressures, gas flow and V_T were recorded. Data were analysed by breath type.

Results In 29 infants, a total of 3864 inflations (mechanical) and inspirations (infant breaths) were analysed (Table 1). Overall mask leak was highest during spontaneous inspirations occurring between manual inflations and those during CPAP. The average V_T was highest during combined inspiration and inflation.

Conclusion Preterm infants are active participants in stabilisation in the DR. V_T and mask leak vary depending on the interaction between the infant’s breathing efforts and the inflations provided by the resuscitator.