Contamination of anaesthetic tubing--a real hazard?

This study aimed to find whether a patient placed on an anaesthetic machine could contaminate the tubing resulting in possible cross-infection to subsequent patients. Twenty randomly chosen anaesthetic circuits were collected after use during operations and cultured for bacteria and fungi. These were compared with ten circuits which had been washed and dried. Another ten washed circuits were attached to an anaesthetic machine and each circulated with air for four hours before similar cultures were performed. No accepted respiratory pathogens were found contaminating the tubing in any of the above situations. Cleaned circuits purposely seeded with either 'viridans streptococci' or staphylococcal bacteriophage were attached to an anaesthetic machine, the other end being held over an air sampler to collect organisms which might be blown out. Seeded tubing did not contaminate the air passing through it, demonstrating that dry anaesthetic gases do not facilitate pick-up and carriage of microorganisms.