A new valve for draw-over anaesthesia

The Diamedica non-rebreathing valve has been developed for use in draw-over anaesthesia and can be positioned at the common gas outlet. Its performance was evaluated against the Laerdal, Ruben and Ambu valves under laboratory conditions. Valve resistance during inspiration and expiration was simulated over a range of constant flow conditions. During flows ranging from 5 to 45 l.min(-1) , the Diamedica and Ruben valves exhibited a negligible resistance of < 150 Pa, with the Laerdal and Ambu valves achieving resistance of < 200 Pa. To assess the effects of sterilisation, this procedure was repeated following autoclaving, after which the Diamedica valve exhibited resistance to flow of < 150 Pa at 25 l.min(-1) for inlet resistance and 35 l.min(-1) for outlet resistance. The Diamedica, Ambu and Laerdal valves demonstrated resistance of < 100 Pa when saturated with water, while the Ruben valve exhibited resistance > 500 Pa.