Safety of anaesthesia breathing circuit connectors

Conical connectors used in anaesthesia breathing circuits are prone to accidental disconnections. We tested 291 connectors of 15 and 22 mm size and found that most did not comply with dimensional requirements in voluntary standards such as those issued by the Canadian Standards Association (CSA) and the American National Standards Institute (ANSI). However, measurements of disconnecting force showed no strong correlation with dimensional accuracy as determined by the standard gauge tests. When wrung together, metal-to-metal or plastic-to-plastic joints were considerably stronger than metal-to-plastic joints. Wrung joints were much stronger than connections made with a straight push, which showed no marked dependence on the type of material. Our results indicate that improved compliance with dimensional standards as determined by existing gauge tests will not improve connector performance. Rather, what is needed is a performance standard based on practical criteria. Under such a standard, some materials may prove unsuitable for friction-fit connections.