Background Preterm newborns often need respiratory support for lung liquid clearance and aeration. Previous studies provided tidal volumes during positive pressure ventilation (PPV) and breathing, but very little is known how efficient these are in lung recruitment and gas exchange. Aim was to measure tidal volume, functional residual capacity (FRC) changes and gas exchange during respiratory support in preterm infants at birth.

Methods In preterm newborns needing respiratory support the following measurements were performed: 1) expired tidal volumes (Vte (mL/kg)) using respiratory function monitoring, 2) changes in FRC (AU/kg) per breath using Respiratory Inductance Plethysmography (bands placed around the rib cage (RC) and abdomen (AB)), 3) expired CO₂ using a volumetric CO₂ monitor. For respiratory support a T-piece resuscitator and mask were used with PIP 25 cm H₂O and PEEP 5 cm H₂O. Data was analysed during sustained inflation (SI), the first 30s of PPV and breathing on CPAP.

Results 15 infants were included (median (IQR) gestational age 28 (27–31) weeks, birth weight 1080 (994–1300) grams). There was no difference in Vte between SI, PPV and breathing (table). Gas exchange was more efficient during breathing and inflations coinciding with breathing compared to SI and inflations only (table). Little change occurred during the SI, PPV and breathing measured at the RC. In contrast, there was FRC gain at the AB during the SI, PPV and most with breathing.

Conclusions While tidal volumes during PPV and breathing were similar, breathing was more effective in gas exchange and caused more gain in FRC than PPV.