[Comparative study of the efficiency of bacterial filters in long-term mechanical ventilation]

Two commercially available bacterial filters to be used as part of the mechanical ventilation unit during anaesthesia were tested for hygienic criteria. Manufacturers claim that bacterial breathing filters have a filtration capacity of about 99.995%, so that there would be no need for thermal disinfection of tubing and ventilation circuits after each use. One filter is designed for a single use only, the other can be used up to 24 times after sterilisation. Both filters consist of hydrophobic glass fibres.

During simulated mechanical ventilation for 24 h, an alcoholic suspension of Bacillus subtilis was atomized in front of the filters tested. A gelatin membrane filter was integrated in the ventilation circuit and captured the filtered gas behind the test filter.

During simulated mechanical ventilation for 24 h, the filtration capacity of both the disposable and reusable filters (Table 2) did not confirm the manufacturers' short-term technical findings over 8 s (DIN-EN 143).

The use of bacterial filters during mechanical ventilation reduces the probability of bacterial contamination, but does not make sterilisation of the tubes and ventilation circuit unnecessary.