Breathing circuit

A breathing circuit is those parts of a breathing apparatus (or breathing system), which direct the flow of supplied breathing gas to, and sometimes from, the user. The breathing circuit may be open, closed, or semi-closed, depending on whether breathing gas is recycled. A closed or semi-closed circuit will include components which remove carbon dioxide from the exhaled gas and add oxygen before it is delivered for inhalation, so that the mixture remains stable and suitable for supporting life. Terminology may vary slightly between fields of application. In diving and industrial rebreathers, the closed or semi-closed breathing circuit may also be called the loop, or breathing loop. In medical equipment the closed or semi-closed circuit may be called the circle system.

A medical breathing system or medical breathing circuit is a medical device used to deliver oxygen, remove carbon dioxide, and deliver inhalational anaesthetic agents to a patient. Originally developed for use in anaesthesiology, many variants of breathing system are in clinical use, but most comprise a source of fresh gas flow, a length of breathing tubing to direct the gas, an adjustable pressure limiting valve to control pressure within the system and direct waste away, and a reservoir bag to allow assisted ventilation.

Types

Medical

There are many forms of breathing system, each having somewhat different mechanisms of action. They have traditionally been classified by the way in which the system interacts with fresh air from the surrounding atmosphere, and by whether the patient rebreathes gases that they have previously exhaled.