A computer-controlled closed anaesthetic breathing system.

We describe the design and working of a computer-controlled, closed anaesthetic breathing system which rapidly achieves and maintains a prescribed end-tidal concentration of isoflurane in oxygen. The system is simple to set up and not expensive; the only nonstandard component is a modified glass syringe. We have demonstrated that gas analysers may contribute as much as the patient to the accumulation of nitrogen within the breathing system. Details of our clinical experience with the system are presented in an accompanying article.