A ten-year audit of fresh gas flows in a New Zealand hospital: the influence of the introduction of automated agent delivery and comparisons with other hospitals.

Reducing fresh gas flow (FGF) rates with volatile anaesthetics reduces waste, with positive financial and environmental consequences. We have audited FGF since 2001 by analysis of data collected from anaesthetic machines. We recently introduced Aisys(®) (GE Healthcare, Madison, WI, USA) machines that allow automated control of end-tidal levels of volatile anaesthetics. In 2009 the mean FGF was 1.27 l/minute, which was lower than 2001 (2.05 l/minute) and 2006 (1.43 l/minute) and similar to two other New Zealand hospitals. Following introduction of the Aisys(®), mean FGF initially increased to 1.5 l/minute, but fell to 1.09 l/minute over the following 12 months. Median FGF showed a similar pattern and is now <600 ml/minute. Since introduction of the Aisys(®) workstation the proportion of time with flow rates >4 l/minute has increased. The proportion of time spent in automated delivery mode has increased from 35% to 63%. Users valued the workload reduction with end-tidal control. Our findings suggest that in daily practice, with a wide range of practitioners at different levels of training and a broad patient mix, mean flow rates of around 1.3 l/minute with median flows in the range 0.5 to 1.0 l/minute are achievable targets.