title: Heated humidification versus heat and moisture exchangers for ventilated adults and children.
abstract: BACKGROUND
  Humidification by artificial means must be provided when the upper airway is bypassed during mechanical ventilation. Heated humidification (HH) and heat and moisture exchangers (HMEs) are the most commonly used types of artificial humidification in this situation.
  
  
  OBJECTIVE
  To determine whether HHs or HMES are more effective in preventing mortality and other complications in people who are mechanically ventilated.
  
  
  METHODS
  We searched the Cochrane Central Register of Controlled Trials (The Cochrane Library 2010, Issue 4) and MEDLINE, EMBASE and CINAHL (January, 2010) to identify relevant randomized controlled trials.
  
  
  METHODS
  We included randomized controlled trials comparing HMEs to HHs in mechanically ventilated adults and children. We included randomized crossover studies.
  
  
  METHODS
  We assessed the quality of each study and extracted the relevant data. Where appropriate, results from relevant studies were meta-analyzed for individual outcomes.
  
  
  RESULTS
  We included 33 trials with 2833 participants; 25 studies were parallel group design (n = 2710) and 8 crossover design (n = 123). Only 3 included studies reported data for infants or children. There was no overall effect on artificial airway occlusion, mortality, pneumonia, or respiratory complications; however, the PaCO(2) and minute ventilation were increased when HMEs were compared to HHs and body temperature was lower. The cost of HMEs was lower in all studies that reported this outcome. There was some evidence that hydrophobic HMEs may reduce the risk of pneumonia and that blockages of artificial airways may be increased with the use of HMEs in certain subgroups of patients.
  
  
  CONCLUSIONS
  There is little evidence of an overall difference between HMEs and HHs. However, hydrophobic HMEs may reduce the risk of pneumonia and the use of an HMEs may increase artificial airway occlusion in certain subgroups of patients. Therefore, HMEs may not be suitable for patients with limited respiratory reserve or prone to airway blockage. Further research is needed relating to hydrophobic versus hygroscopic HMEs and the use of HMEs in the pediatric and neonatal populations. As the design of HMEs evolves, evaluation of new generation HMEs will also need to be undertaken.
authors.forename: Margaret
authors.initials: M
authors.lastname: Kelly
authors.forename: Donna
authors.initials: D
authors.lastname: Gillies
authors.forename: David A
authors.initials: DA
authors.lastname: Todd
authors.forename: Catherine
authors.initials: C
authors.lastname: Lockwood
mesh_terms: D000328:Adult; D002648:Child; D006358:Hot Temperature / Q000627:therapeutic use*; D006801:Humans; D006813:Humidity / Q000592:standards; D016032:Randomized Controlled Trials as Topic; D012121:Respiration, Artificial / Q000009:adverse effects / Q000379:methods* / Q000401:mortality