Objective To measure tidal volume, plethysmography changes and gas exchange during respiratory support at birth.

Design The following parameters were measured: (1) expired tidal volumes (Vte (mL/kg)) using respiratory function monitoring, (2) changes in plethysmography (AU/kg) per breath using respiratory inductance plethysmography (bands placed around rib cage (RC) and abdomen (AB)) and (3) expired CO₂ (ECO₂) levels using a volumetric CO₂ monitor. For respiratory support, a T-piece resuscitator and facemask were used with peak inspiratory pressure (PIP) 25 cm H₂O and positive end expiratory pressure 5 cm H₂O. Data were analysed during the sustained inflation (SI), positive pressure ventilation (PPV) and breathing on continuous positive airway pressure (CPAP).

Setting The delivery rooms of the Leiden University Medical Center, Leiden, and V. Buzzi, Milan. Patients: 15 preterm infants with a gestational age 28 (27–31) weeks and a birth weight of 1080 (994–1300) g.

Results Vte for PPV inflations, PPV inflations with breathing and spontaneous breathing were significantly different (4.4 (2.5–8.6) vs 8.8 (5.7–11.4) vs 5.7 (3.3–9.8); p<0.0001)). Spontaneous breathing led to the highest ECO₂ levels and during PPV, ECO₂ levels were higher when the inflations coincided with breathing (32 (23–38) vs 20 (13–25) vs 2 (3–11) mm Hg; p<0.0001). Little change in plethysmography amplitude occurred during the SI, PPV and breathing at the RC. There was gain in plethysmography amplitude at the AB during the SI, PPV, but most with breathing.

Conclusions While Vte during breathing on CPAP was lower compared with PPV coinciding with breathing, breathing on CPAP was most effective in gas exchange and plethysmography amplitude gain compared with PPV and PPV coinciding with breathing.