The ADU vaporizing unit: A new vaporizer

We determined the performance of the vaporizer of the ADU machine (Anesthes ia Delivery Unit; Datex-Ohmeda, Helsinki, Finland). The effects of carrier gas composition (oxygen, oxygen/N2O mixture, and air) and fresh gas flow (0 .2 to 10 L/min) on vaporizer performance were examined with variable concen trations of isoflurane, sevoflurane, and desflurane across the whole range of each vaporizer's output. In addition, the effects of sudden changes in f resh gas flow and carrier gas composition, back pressure, flushing, and tip ping were assessed. Vaporizer output depended on fresh gas flow, carrier ga s composition, dial settings, and the drug used. Vaporizer output remained within 10% of dial setting with fresh gas flows of 0.3-10 L/min for isoflur ane, within 10% of dial setting with fresh gas flows of 0.5-5 L/min for sev oflurane, and within 13% of dial setting with fresh gas flows of 0.5 to 1 L /min for desflurane. Outside these fresh gas flow ranges, output deviated m ore. The effect of sudden changes in fresh gas flow or carrier gas composit ion, back pressure, flushing, and tipping was minimal. We conclude that the ADU vaporizer performs well under most clinical conditions. Despite a diff erent design and the use of complex algorithms to improve accuracy, the sam e physical factors affecting the performance of conventional vaporizers als o affect the ADU vaporizer.