[Assessment of 44 heat and moisture exchange filters. What to choose?]

If the use of heat and moisture exchange filter (HMEF) in anaesthesia is recommended by the French Society of Anaesthesia and Intensive Care (SFAR), the criteria's choice are not clearly defined. Many HMEF are proposed by manufacturers which technical characteristics are different.

The aim of this study was to evaluate the HMEF using items of the American Association of Respiratory Care (AARC) and technical dossiers.

All manufactures producing filters have been contacted to give their technical dossiers. Forty-eight filters have been analyzed (13 mechanical filters, 31 electrostatic filters). Each item has been scaled 0, 5 or 10. The final result was on 10.

Seventeen filters had a note superior to 5. There were 8 mechanical filters and 9 electrostatic filters. The difference between the filters was the size of the micro-organisms tested and the duration of the test. Some filters were not tested by independent laboratories (N = 8). There were differences between the commercial documentation and on Internet and the technical dossiers (N = 12).

We noted the good quality of the filters particularly concerning criters recommended by the Sfar (filter medium, filtration efficiency, microbial challenge number and duration of the test). The electrostatic filters recently used in anaesthesia have high performance concerning filtration efficiency. To supprime the moisture output criteria did not change the results.

Criteria's used by manufactures to evaluate there filters are not always precised or too restrictive. The technical tests, the international norms, the certificates of validation, the ergonomic qualities and the definition of our needs are the main elements of choice of a filter.