Sudden interruption of gas flow through a Schrader oxygen coupler unit.

The flow of oxygen to an anaesthetic gas machine suddenly and completely stopped during the course of a general anaesthetic. The cause of the failure was traced to a Schrader oxygen coupler check unit. During servicing, one component of the check unit had inadvertently been replaced by a similar but inappropriate component. Interruption of oxygen flow resulted from a loss of contact between two components of the check unit. This incident raises questions about the basic design and safety of Schrader coupler check units.