Anaesthetic Breathing Systems

The function of breathing is to maintain a supply of oxygen to the lungs for oxygenation of the tissues, and to remove carbon dioxide from the body. When used for spontaneous ventilation, a breathing circuit must enable a patient to breathe satisfactorily without significantly increasing the work of breathing or the physiological deadspace. It must also conduct inhalational anaesthetic agents to the patient. The volume of gas inspired and expired with each breath is the tidal volume (normally 6-10ml.kg-1), the total volume breathed in a minute is the minute volume and the volume of gas in the lungs at the end of normal expiration is the functional residual capacity (FRC).