Anesthesia Breathing Circuits

Anesthesia breathing systems serve as a conduit to deliver anesthetic and other gases to a patient. Various designs of breathing systems have been created to serve this function. One method of classifying anesthesia breathing systems is based on how gas flows: open, semi-open, semi-closed, and closed.
The function of any breathing circuit is to deliver oxygen and anesthetic gases, and eliminate carbon dioxide.
Mapleson breathing systems are used for delivering oxygen and anaesthetic agents and to eliminate carbon dioxide during anaesthesia. They consist of different components: Fresh gas flow, reservoir bag, breathing tubes, expiratory valve, and patient connection.
Because a typical adult circle breathing circuit (with 5-foot-long inspiratory and expiratory limbs) has a volume of approximately 7 L, 1 mL of a volatile anesthetic liquid in such a circuit will produce a concentration of nearly 3% (approximately 200 mL/7000 mL) on complete mixing.