[Heat and moisture exchanging filters for conditioning of inspired gases in adult anesthesia and resuscitation].

OBJECTIVES

Heat and moisture-exchanging filters (HMEFs) are increasingly used in clinical practice. At the same time, new scientific data are available which clarify the benefits of these devices.

DATA SOURCES

We searched in the Medline database for all papers written in English or French, without limiting date of publication, using the following key-words separately or in combination: humidity, temperature, mechanical ventilation, equipment.

STUDY SELECTION

From the 200 articles provided by Medline, we selected those directly concerning HMEFs. Some older studies and those on HMEFs no longer available were excluded.

DATA EXTRACTION

Principle data available from the literature were analysed.

DATA SYNTHESIS

Humidification and warming of the inspired gas mixture is mandatory during mechanical ventilation. There is a direct link between HMEF performance and the characteristics of tracheal secretions. This justified the recommendation for the use of HMEFs with a humidity output above 30 mg of water per litre of gas mixture. In this case, HMEFs are as efficient as conventional heated humidifiers. HMEFs seem to decrease the rate of nosocomial pneumonia in comparison with heated humidifiers. HMEFs induce a slight increase of dead space which should be taken into consideration during weaning from mechanical ventilation. There are demonstrable data in the literature suggesting the possibility of cross viral infection via the anaesthetic machine when an HMEF is not used. There are no data which suggest a specific type of HMEF regarding viral filtration.

CONCLUSION

According to the literature data, using an HMEF is essential in anaesthesia and is highly recommended in intensive care.