The Johannesburg A-D circuit switch. A valve device for converting a co-axial Mapleson D into a co-axial Mapleson A system.

A simple valve device is described for a co-axial tubing anaesthetic system which enables selection of the circuit characteristics of either a modified Mapleson A system for spontaneous breathing or a modified Mapleson D system for controlled ventilation. Thus, the system allows an economical fresh gas flow to be used during either controlled or spontaneous ventilation. The mode of ventilation may be changed during anaesthesia without adjusting the patient tubing or the attachment of the system to the anaesthetic machine.