A composite semiclosed anaesthetic system suitable for controlled or spontaneous respiration.

FOR patients who are breathing spontaneously the Magill attachment or system A (Mapleson, 1954) is the most widely used semiclosed anaesthetic system. A theoretical analysis predicted that if the freshgas inflow were made at least equal to the patient's minute-volume ventilation, then rebreathing would be eliminated (Mapleson, 1954). A similar conclusion has been reached experimentally by various workers. For patients whose respiration is manually controlled, however, a recent study (Waters and Mapleson, 1961) has shown that system D involves less rebreathing than system A. In the course of that investigation, an arrangement was devised which enabled the anaesthetist to change over easily from one to the other. This is now described in the belief that it may have some value in ordinary clinical anaesthesia when it is desired to avoid the use of soda lime.