A fuzzy/logic based decision support system for low-flow/closed-loop anaesthesia

Low flow/closed loop anaesthesia (LFCLA) is the controlled administration of the minimum amount of respiratory and anaesthetic gases required to anaesthetise the patient. At present, the control procedure is manual, with the anaesthetist visually assessing the volume of the reservoir bag and the inspiratory and expiratory gas concentrations. Considering this, the application of fuzzy logic to clinical anasethesia seems ideal. The design of such a system is in two stages. The first stage is of a single gas (oxygen) system, operating in an open decision support mode, based on the 'expert knowledge' of an anaesthetist. Once the design is clinically optimised, the feedback loop will be closed to provide the automatic control of oxygen only. The second stage of the project will be the extension of the system to handle other anaesthetic gases. A graphical user interface, interfaced with a software-driven simulation of the controller, was designed to aid the clinical evaluation and to display the system components.