Anaesthetic machine and breathing system contamination and the efficacy of bacterial/viral filters.

Contamination of the anaesthetic machine and breathing system by the environment and by patient exposure has been shown to occur. Outside the intensive care setting, however, it is difficult to demonstrate that the anaesthetic machine and breathing system are a vector for patient cross-infection. Bacterial and viral filters for use within the breathing system have been shown to be very effective for filtration, yet their use has not been demonstrated to be of benefit in the prevention of cross-infection between patients. Several instances of patient morbidity are a direct consequence of filter use. The use of bacterial/viral filters may represent another step towards defensive medical practice.