title: Ventilator-associated pneumonia and mortality: a systematic review of observational studies.
abstract: OBJECTIVE
  To determine the attributable mortality of ventilator-associated pneumonia in a systematic review and meta-analysis of observational studies. Ventilator-associated pneumonia is generally believed to increase the mortality of patients. This notion is predominantly based on the results of observational studies.
  
  
  METHODS
  We performed a systematic search strategy using PubMed, Web of Science, and Embase from their inception through February 2007. In addition, a reference and related article search was performed.
  
  
  METHODS
  Studies were included if they reported mortality rates of patients with and without ventilator-associated pneumonia.
  
  
  METHODS
  Fifty-two studies with a total of 17,347 patients met the inclusion criteria. Pooling of all studies resulted in relative risk of 1.27 (95% Confidence Interval = 1.15-1.39), but heterogeneity was considerable (I2 statistic = 69%). The origin of heterogeneity could not be explained by differences in study design, study quality, and diagnostic approach. However, heterogeneity was limited for studies investigating only trauma patients (I2 = 1.3%) or patients with acute respiratory distress syndrome (I2 = 0%), with estimated relative risk of 1.09 (95% Confidence Interval = 0.87-1.37) among trauma patients and 0.86 (95% Confidence Interval = 0.72-1.04) among patients with acute respiratory distress syndrome.
  
  
  CONCLUSIONS
  There is no evidence of attributable mortality due to ventilator-associated pneumonia in patients with trauma or acute respiratory distress syndrome. However, in other nonspecified patient groups, there is evidence for attributable mortality due to ventilator-associated pneumonia, but this could not be quantified due to heterogeneity in study results. More detailed studies, allowing subgroup analyses, are needed to determine the attributable mortality of ventilator-associated pneumonia in these patient populations.
authors.affiliation: Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, The Netherlands. W.G.Melsen@umcutrecht.nl
authors.forename: Wilhelmina G
authors.initials: WG
authors.lastname: Melsen
authors.forename: Maroeska M
authors.initials: MM
authors.lastname: Rovers
authors.forename: Marc J M
authors.initials: MJ
authors.lastname: Bonten
mesh_terms: D000328:Adult; D002423:Cause of Death; D003422:Critical Care / Q000706:statistics & numerical data*; D006801:Humans; D009104:Multiple Trauma / Q000401:mortality*; D053717:Pneumonia, Ventilator-Associated / Q000401:mortality*; D012128:Respiratory Distress Syndrome / Q000401:mortality*; D012306:Risk; D016019:Survival Analysis