A rapid-response u.v. halothane meter.

The design and performance characteristics of an instrument for monitoring halothane concentrations which operates on the principle of the absorption of u.v. light are described. The innovation is that the entire exhaled breath passes through the sample cell, enabling the breath-by-breath halothane concentration to be measured accurately and instantaneously. Stablized power supplies, solid-state circuitry and filtering make the instrument stable and selective. A valve prevents rebreathing of gas exposed previously to u.v. light in the sample cell. Inspired and end-tidal concentrations are displayed digitally and an analog output is available also. Zero and gain drift were negligible after an initial settling period, and interference from other respiratory gases was not detectable. The monitor is suitable for use during anaesthesia for adults and children.