Bacterial filters protect anaesthetic equipment in a low-flow system

We have recently described a low-flow system with mechanical ventilation in which there was an open connection between the circle and ventilator. In the present study bacterial contamination and the role of bacterial filters at different points in the system were studied. Filters between the tracheal tube and circle are an effective barrier, but their absence did not increase contamination of either the circle or the ventilator. Some filters are also effective as heat and moisture exchangers if situated at the tracheal tube. Because of the lack of bacterial contamination, a prolonged interval between disinfection of the open connection and ventilator is acceptable, which reduces wear and costs.