Which Humidification Technology Should Be Used for Invasive and Noninvasive Ventilation?

Abstract

Humidification of gases delivered to patients is always necessary during invasive mechanical ventilation (with a minimum humidity of 30 mg H₂O/l) and most often during noninvasive ventilation (there is currently no clear recommendation on the humidity level required in this situation). Heat and moisture exchangers (HME) and heated humidifiers (HH) can be used. Contrary to usual belief, HH are not always the most efficient to humidify gases. Clinicians should be aware that in some situations (high temperature in the room or sun directly on the humidifier), gases are not sufficiently humidified and there is no efficient monitoring of the moisture currently proposed routinely. Before choosing a HME to humidify the gases, the very heterogeneous humidity performance of the devices proposed on the market must be known. Their humidification performance is reduced mainly in case of hypothermia. Their other limitation is the additional dead space that reduces CO₂ elimination during controlled mechanical ventilation, especially in situations where the respiratory rate is high and the tidal volumes low (as in acute respiratory distress syndrome, ARDS). During spontaneous ventilation, this additional dead space may increase the respiratory work of breathing. This may be compensated by an increase in pressure support levels especially during weaning tests. Based on the analysis of the various data in the literature, we recommend the use of HME as first-line, following the contra-indications (especially hypothermia). The heated humidifiers should be used in case of protective ventilation, especially in ARDS.