title: Sterile water is unnecessary in a continuous positive airway pressure convection-type humidifier in the treatment of obstructive sleep apnea syndrome.
abstract: 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.
authors.affiliation: Annostr. 1, Krankenhaus Kloster Grafschaft, Zentrum für Pneumologie, Beatmungs- und Schlafmedizin, D-57392 Schmallenberg, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Wenzel
authors.forename: Matthias
authors.initials: M
authors.lastname: Klauke
authors.forename: Frank
authors.initials: F
authors.lastname: Gessenhardt
authors.forename: Dominic
authors.initials: D
authors.lastname: Dellweg
authors.forename: Peter
authors.initials: P
authors.lastname: Haidl
authors.forename: Bernd
authors.initials: B
authors.lastname: Schönhofer
authors.forename: Dieter
authors.initials: D
authors.lastname: Köhler
mesh_terms: D000336:Aerosols; D045422:Continuous Positive Airway Pressure / Q000379:methods*; D006801:Humans; D012891:Sleep Apnea Syndromes / Q000628:therapy*; D013242:Sterilization; D014867:Water / Q000592:standards*
chemical_list: D000336:Aerosols; D014867:Water