RESPIRATION AND THE AIRWAY Delivery of tidal volume from four anaesthesia ventilators during volume-controlled ventilation: a bench study

Editor’s key points † This study investigated the accuracy of delivered tidal volume in four new ventilators under different conditions. † Set and delivered tidal volumes differed when compliance and resistance were changed, although the effect of fresh gas flow was less. † Some of the new ventilators tested were more accurate than others. † The clinical significance of these findings is uncertain, but anaesthetists should be aware of the potential for imprecision. Background. Tidal volume (VT) must be accurately delivered by anaesthesia ventilators in the volume-controlled ventilation mode in order for lung protective ventilation to be effective. However, the impact of fresh gas flow (FGF) and lung mechanics on delivery of VT by the newest anaesthesia ventilators has not been reported. Methods. We measured delivered VT (VTI) from four anaesthesia ventilators (AisysTM, FlowiTM, PrimusTM, and ZeusTM) on a pneumatic test lung set with three combinations of lung compliance (C, ml cm H2O ) and resistance (R, cm H2O litre 21 s): C60R5, C30R5, C60R20. For each CR, three FGF rates (0.5, 3, 10 litre min) were investigated at three set VTs (300, 500, 800 ml) and two values of PEEP (0 and 10 cm H2O). The volume error 1⁄4 [(VTI 2 VTset)/VTset] × 100 was computed in body temperature and pressuresaturated conditions and compared using analysis of variance.