title: In vivo efficacy of two heated humidifiers used during CPAP-therapy for obstructive sleep apnea under various environmental conditions.
abstract: OBJECTIVE
  To investigate the humidification performance-defined as the maximum achievable absolute humidity in the CPAP tube-of two heated humidifier systems (HH) offered as CPAP accessories, as a function of ambient air conditions.
  
  
  METHODS
  In 48 patients undergoing CPAP treatment, temperature (T) and relative humidity (RH) in the distal CPAP tube system were measured, with and without either of the two heated humidifiers A (HH-A, n=23), or B (HH-B, n=25), until a steady state was achieved. At the same time, ambient T and RH in the examination room were recorded. T and RH were used to calculate the absolute humidity (AH).
  
  
  METHODS
  University Hospital, Erlangen, Germany. PATICIPANTS: 48 patients with obstructive sleep apnea undergoing CPAP therapy.
  
  
  METHODS
  N/A.
  
  
  RESULTS
  Conditions in the examination room during measurement with the HH-A, T = 22.5+2.1 (16.4-26.0) degrees C and AH = 9.3+2.4 (5.3-13.9) g/m3 did not differ significantly from those prevailing during measurements with the HH-B, T = 22.9+1.9 (18.9-26.3) degrees C and AH = 9.9+2.8 (6.2-16.4) g/m3. The mean humidification performance (steady state AH with HH within the CPAP tube) of the HH-A was 23.5+2.9 (19.1-29.9) g/m3, that of the HH-B 26.8+3.9 (21.0-34.4) g/m3.
  
  
  CONCLUSIONS
  Under the ambient conditions of humidity and temperature, commonly found in European and North American bedrooms, both HH demonstrate a high humidification performance that even falls within the range recommended for intubated patients. The difference between the two HH is small, and probably not clinical relevant. Thus, it would appear that both HH are suitable for the treatment of dry upper airways under CPAP therapy.
authors.affiliation: Medical Department I, University of Erlangen-Nuremberg, Germany. gunther.wiest@med1.imed.uni-erlangen.de
authors.forename: G H
authors.initials: GH
authors.lastname: Wiest
authors.forename: J
authors.initials: J
authors.lastname: Foerst
authors.forename: F S
authors.initials: FS
authors.lastname: Fuchs
authors.forename: A H
authors.initials: AH
authors.lastname: Schmelzer
authors.forename: E G
authors.initials: EG
authors.lastname: Hahn
authors.forename: J H
authors.initials: JH
authors.lastname: Ficker
mesh_terms: D004777:Environment; D005260:Female; D006358:Hot Temperature; D006801:Humans; D006813:Humidity; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration / Q000379:methods*; D011897:Random Allocation; D020181:Sleep Apnea, Obstructive / Q000628:therapy*; D016896:Treatment Outcome