Objectives Volume-targeted ventilation (VTV) is widely used and may reduce lung injury, but this assumes the clinically set tidal volume (V_Tset) is accurately delivered. This prospective observational study aimed to determine the relationship between V_Tset, expiratory V_T (V_Te) and endotracheal tube leak in a modern neonatal ­volume-targeted ventilator (VTV) and the resultant partial arterial pressure of carbon dioxide (PaCO₂) relationship with and without VTV.

Design Continuous inflations were recorded for 24 hours in 100 infants, mean (SD) 34 (4) weeks gestation and 2483 (985) g birth weight, receiving synchronised mechanical ventilation (SLE5000, SLE, UK) with or without VTV and either the manufacturer’s V4 (n=50) or newer V5 (n=50) VTV algorithm. The V_Tset, V_Te and leak were determined for each inflation (maximum 90 000/infant). If PaCO₂ was sampled (maximum of 2 per infant), this was compared with the average V_Te data from the preceding 15 min.

Results A total of 7 497 137 inflations were analysed. With VTV enabled (77 infants), the V_Tset−V_Te bias (95% CI) was 0.03 (−0.12 to 0.19) mL/kg, with a median of 80% of V_Te being ±1.0 mL/kg of V_Tset. Endotracheal tube leak up to 30% influenced V_Tset−V_Te bias with the V4 (r²=−0.64, p<0.0001; linear regression) but not V5 algorithm (r²=0.04, p=0.21). There was an inverse linear relationship between V_Te and PaCO₂ without VTV (r²=0.26, p=0.004), but not with VTV (r²=0.04, p=0.10), and less PaCO₂ within 40–60 mm Hg, 53% versus 72%, relative risk (95% CI) 1.7 (1.0 to 2.9).

Conclusion VTV was accurate and reliable even with moderate leak and PaCO₂ more stable. VTV algorithm differences may exist in other devices.