Capnography to check the safety of Bain circuit

The test of the inner tube integrity is an important checklist prior to the safe use of Bain's breathing system. This is because the major concern with the use of Bain's circuit is the potential malfunctioning of the circuit due to avulsion of the inner fresh gas delivery tube at the machine end which will turn the outer tube into dead space, a hazard recognized by Hannallah. Pethick test although widely used may not be foolproof to detect leaks in the inner tube. Ghani suggested the use of a plunger to perform the inner tube occlusion. Partially or completely occluded outer tube may produce a false positive result. Using very high flows or prolonged occlusion may cause damage to anesthetic machine due to high pressure.