Recommendations for domiciliary use of heat and moisture exchangers in artificial ventilation

Patients that are artificially ventilated via tracheostomy may need heating and humidification of inspired gas. Neat and moisture exchangers (HME) are widely used in domiciliary ventilation and manufacturers recommend changin g them every 24 hours without any scientific evidence. We have reviewed exi sting evidence which shows that 48 h total use of HME does not increase res istance to airflow and is not associated with increased incidence of infect ion. However the efficiency of humidification varies according to HME: Hydr ophobic units give inadequate humidification and should be changed after 24 h of use. Hygroscopic HME are variable and only those giving an absolute h umidity of 25 to 30 mg H2O/L should be used for more than 24 h. Condensatio n in the flex-tube is significantly correlated with values for absolute hum idity and this may help to evaluate the efficiency of HME.