Volume guaranteed? Accuracy of a volume-targeted ventilation mode in infants

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 (PaCO 2 ) 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 PaCO 2 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 (r 2 =−0.64, p 2 =0.04, p=0.21). There was an inverse linear relationship between V Te and PaCO 2 without VTV (r 2 =0.26, p=0.004), but not with VTV (r 2 =0.04, p=0.10), and less PaCO 2 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 PaCO 2 more stable. VTV algorithm differences may exist in other devices.