title: Effectiveness of heat and moisture exchangers in preventing ventilator-associated pneumonia in critically ill patients: a meta-analysis.
abstract: BACKGROUND
  Patients may acquire ventilator-associated pneumonia (VAP) by aspirating the condensate that originates in the ventilator circuit upon use of a conventional humidifier. The bacteria that colonize the patients themselves can proliferate in the condensate and then return to the airways and lungs when the patient aspirates this contaminated material. Therefore, the use of HME might contribute to preventing pneumonia and lowering the VAP incidence. The aim of this study was to evaluate how the use of HME impacts the probability of VAP occurrence in critically ill patients.
  
  
  METHODS
  On the basis of the acronym "PICO" (Patient, Intervention, Comparison, Outcome), the question that guided this review was "Do critically ill patients under invasive mechanical ventilation present lower VAP incidence when they use HME as compared with HH?". Two of the authors of this review searched the databases PUBMED/Medline, The Cochrane Library, and Latin-American and Caribbean Literature in Health Sciences, LILACS independently; they used the following keywords: "heat and moisture exchanger", AND "heated humidifier", AND "ventilator-associated pneumonia prevention". This review included papers in the English language published from January 1990 to December 2012.
  
  
  RESULTS
  This review included ten studies. Comparison between the use of HME and HH did not reveal any differences in terms of VAP occurrence (OR = 0.998; 95% CI: 0.778-1.281). Together, the ten studies corresponded to a total sample of 1077 and 953 patients in the HME and HH groups, respectively; heterogeneity among the investigations was low (I(2) < 50%). Information about the outcome mortality was available in only eight of the ten studies. The use of HME and HH did not afford different results in terms of mortality (OR = 1.09; 95% CI: 0.864-1.376). The total sample size was 884 and 762 patients, respectively. Heterogeneity among the studies was low (I(2) = 0.0%).
  
  
  CONCLUSIONS
  Current meta-analysis was not sufficient to definitely exclude an associate between heat and moisture exchangers and VAP. Despite the methodological limitations found in selected clinical trials, the current meta-analysis suggests that HME does not decrease VAP incidence or mortality in critically ill patients.
authors.affiliation: Escola de Enfermagem de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP Brazil ; Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto - USP, Divisão de Terapia Intensiva, Departamento de Cirurgia e Anatomia - 2o andar, Av. Bandeirantes, 3900 - Bairro Monte Alegre, Ribeirão Preto, SP Brazil.
authors.forename: Mayra Gonçalves
authors.initials: MG
authors.lastname: Menegueti
authors.affiliation: Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto - USP, Divisão de Terapia Intensiva, Departamento de Cirurgia e Anatomia - 2o andar, Av. Bandeirantes, 3900 - Bairro Monte Alegre, Ribeirão Preto, SP Brazil.
authors.forename: Maria
authors.initials: M
authors.lastname: Auxiliadora-Martins
authors.affiliation: Departamento de Medicina Social, Av. Bandeirantes, 3900 - Bairro Monte Alegre, Ribeirão Preto, SP Brazil.
authors.forename: Altacílio Aparecido
authors.initials: AA
authors.lastname: Nunes
mesh_terms: D016638:Critical Illness / Q000453:epidemiology / Q000628:therapy*; D006358:Hot Temperature / Q000627:therapeutic use*; D006801:Humans; D006813:Humidity; D053717:Pneumonia, Ventilator-Associated / Q000175:diagnosis / Q000453:epidemiology / Q000517:prevention & control*; D012121:Respiration, Artificial / Q000009:adverse effects* / Q000379:methods; D016896:Treatment Outcome
keywords: Critically ill patients; Heat and moisture exchangers; Ventilator-associated pneumonia
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