Breathing systems

Breathing systems are the fundamental components that couple the patient's respiratory system to the anaesthetic machine, and enable the intermittent respiratory pump to be fed by a continuous flow of gas. although often consisting of only a few simple components, the correct functioning of these components is vital to the safe conduct of anaesthesia. Valve-based breathing systems have been the mainstay of adult anaesthetic practice for many years, whilst, historically, non-valved systems have been preferred in paediatric practice because of their lower imposed respiratory load. Various classifications of breathing systems are discussed, although that proposed more than 50 years ago by Mapleson remains the preferred choice. Whilst 'rebreathing' is often seen as abad thing, some breathing systems preferentially allow the recycling of alveolar dead-space gas that has already been warmed and humidified and can hardly be considered to be undesirable. the use of 'circle-type' breathing systems is increasingly supplanting the use of more traditional breathing systems for the maintenance of anaesthesia because of their reduced environmental pollution and much greater economy.