OBJECTIVE We investigated the necessity of using sterile water in humidifiers for avoiding respiratory tract infections during nasal continuous positive airway pressure (nCPAP) therapy. METHODS Water in a convection-type humidifier (Sirius; Heinen and Löwenstein GmbH; Bad Ems, Germany) was labeled with (99m)Tc-diethylenetriamine penta-acetic acid. Low-flow (2 L/min, 4 L/min, or 6 L/min) and high-flow (31 to 46 L/min) rates were applied, rates typical for nCPAP. Heat and moisture exchange filters were placed behind the start of the tube to measure any radioactive aerosol. RESULTS We demonstrated that no radioactive aerosols were produced, either with low or high flows. CONCLUSIONS The convection-type humidifier produces water vapor but does not aerosolize the water. We conclude that bacteria, other microorganisms, or even solutes that may be contained in the water cannot be transported into the air and thus will not be deposited in the lung. In order to avoid respiratory tract infections, sterile water is not required, at least in this particular humidifier. We suggest that nonsterile tap water is probably a safe alternative.
M. Wenzel, M. Klauke, Frank Gessenhardt