title: Efficacy of heat and moisture exchangers in preventing ventilator-associated pneumonia: meta-analysis of randomized controlled trials.
abstract: OBJECTIVE
  Several randomized controlled trials (RCT) have examined the effect of antibacterial humidification strategies, particularly the replacement of heated humidifiers (HH) by heat and moisture exchangers (HME), in preventing ventilator-associated pneumonia (VAP). The present meta-analysis reviews these RCTs.
  
  
  METHODS
  RCTs were identified by searching the Medline and Cochrane Central Register of Controlled Trials databases from 1990 to 2003. We included RCTs using HMEs in the treatment group and HHs in the control group and reporting the incidence of pneumonia as a study outcome. Two investigators independently abstracted key data on design, population, intervention and outcome of the studies.
  
  
  RESULTS
  Between 1990 and 2003 eight RCTs met the inclusion criteria of this analysis. Pooling the results from these studies revealed a reduction in the relative risk of VAP in the HME group (0.7), particularly in MV with a duration of at least 7 days (five RCTs, relative risk 0.57).
  
  
  CONCLUSIONS
  This meta-analysis found a significant reduction in the incidence of VAP in patients humidified with HMEs during MV, particularly in patients ventilated for 7 days or longer. This finding is limited by the exclusion of patients at high risk for airway occlusion from some of the studies. Moreover, contraindications (tenacious secretions, airway obstructive disease, hypothermia) and technical issues of HMEs must be considered. Further RCTs are necessary to examine the wider applicability of HMEs and their extended use.
authors.affiliation: Institut für Medizinische Mikrobiologie und Krankenhaushygiene, Medizinische Hochschule Hannover, Carl-Neuberg-Strasse 1, 30625 Hanover, Germany. kola.axel@mh-hannover.de
authors.forename: Axel
authors.initials: A
authors.lastname: Kola
authors.forename: Tim
authors.initials: T
authors.lastname: Eckmanns
authors.forename: Petra
authors.initials: P
authors.lastname: Gastmeier
mesh_terms: D000389:Air Conditioning / Q000379:methods*; D006361:Heating; D006801:Humans; D006813:Humidity; D007362:Intensive Care Units; D011014:Pneumonia / Q000209:etiology / Q000517:prevention & control; D016032:Randomized Controlled Trials as Topic; D012121:Respiration, Artificial / Q000009:adverse effects*