Systems Theory and the Anaesthetist

The application of the various aspects of systems theory has increased steadily over the last 10 years and has proved useful in such diverse fields as surgical services (Spratt et al. 1974), public health (Haas 1974), education (Harrington 1966), nephrology (Bigelow et al. 1973), medical information (Davis 1973), behavior (Shooster 1974), internal medicine (Guyton et al. 1972), metaphysics (Gayer 1972), and sociology (Attinger & Millendorfer 1968). More recently, rystems analysis has been applied to anaesthetic systems in the engineering literature (Smith & Schwede: 1972) and has begun to appear in the anaesthesia literature (Brows 1973). The anaesthetist in the operating room is part of a complex system. In its simplest form the latter involves the anaesthetist, the anaesthesia delivery system, the patient and the surgeon. This discussion is intended to introduce the anaesthetist to some of the terminology and techniques common to the systems analysis approach. Examples have been drawn from biological aystems in man which have proved useful to describe in feedback control terms. Where possible, the examples used are those most relevant to anaesthesiology.