title: Association between use of lung-protective ventilation with lower tidal volumes and clinical outcomes among patients without acute respiratory distress syndrome: a meta-analysis.
abstract: BACKGROUND
  Lung-protective mechanical ventilation with the use of lower tidal volumes has been found to improve outcomes of patients with acute respiratory distress syndrome (ARDS). It has been suggested that use of lower tidal volumes also benefits patients who do not have ARDS.
  
  
  OBJECTIVE
  To determine whether use of lower tidal volumes is associated with improved outcomes of patients receiving ventilation who do not have ARDS.
  
  
  METHODS
  MEDLINE, CINAHL, Web of Science, and Cochrane Central Register of Controlled Trials up to August 2012.
  
  
  METHODS
  Eligible studies evaluated use of lower vs higher tidal volumes in patients without ARDS at onset of mechanical ventilation and reported lung injury development, overall mortality, pulmonary infection, atelectasis, and biochemical alterations.
  
  
  METHODS
  Three reviewers extracted data on study characteristics, methods, and outcomes. Disagreement was resolved by consensus.
  
  
  RESULTS
  Twenty articles (2822 participants) were included. Meta-analysis using a fixed-effects model showed a decrease in lung injury development (risk ratio [RR], 0.33; 95% CI, 0.23 to 0.47; I2, 0%; number needed to treat [NNT], 11), and mortality (RR, 0.64; 95% CI, 0.46 to 0.89; I2, 0%; NNT, 23) in patients receiving ventilation with lower tidal volumes. The results of lung injury development were similar when stratified by the type of study (randomized vs nonrandomized) and were significant only in randomized trials for pulmonary infection and only in nonrandomized trials for mortality. Meta-analysis using a random-effects model showed, in protective ventilation groups, a lower incidence of pulmonary infection (RR, 0.45; 95% CI, 0.22 to 0.92; I2, 32%; NNT, 26), lower mean (SD) hospital length of stay (6.91 [2.36] vs 8.87 [2.93] days, respectively; standardized mean difference [SMD], 0.51; 95% CI, 0.20 to 0.82; I2, 75%), higher mean (SD) PaCO2 levels (41.05 [3.79] vs 37.90 [4.19] mm Hg, respectively; SMD, -0.51; 95% CI, -0.70 to -0.32; I2, 54%), and lower mean (SD) pH values (7.37 [0.03] vs 7.40 [0.04], respectively; SMD, 1.16; 95% CI, 0.31 to 2.02; I2, 96%) but similar mean (SD) ratios of PaO2 to fraction of inspired oxygen (304.40 [65.7] vs 312.97 [68.13], respectively; SMD, 0.11; 95% CI, -0.06 to 0.27; I2, 60%). Tidal volume gradients between the 2 groups did not influence significantly the final results.
  
  
  CONCLUSIONS
  Among patients without ARDS, protective ventilation with lower tidal volumes was associated with better clinical outcomes. Some of the limitations of the meta-analysis were the mixed setting of mechanical ventilation (intensive care unit or operating room) and the duration of mechanical ventilation.
authors.affiliation: Department of Critical Care Medicine, ABC Medical School, Santo André, São Paulo, Brazil. aryserpa@terra.com.br
authors.forename: Ary
authors.initials: A
authors.lastname: Serpa Neto
authors.forename: Sérgio Oliveira
authors.initials: SO
authors.lastname: Cardoso
authors.forename: José Antônio
authors.initials: JA
authors.lastname: Manetta
authors.forename: Victor Galvão Moura
authors.initials: VG
authors.lastname: Pereira
authors.forename: Daniel Crepaldi
authors.initials: DC
authors.lastname: Espósito
authors.forename: Manoela de Oliveira Prado
authors.initials: Mde O
authors.lastname: Pasqualucci
authors.forename: Maria Cecília Toledo
authors.initials: MC
authors.lastname: Damasceno
authors.forename: Marcus J
authors.initials: MJ
authors.lastname: Schultz
mesh_terms: D006801:Humans; D007902:Length of Stay; D008171:Lung Diseases / Q000503:physiopathology* / Q000628:therapy*; D055370:Lung Injury / Q000503:physiopathology* / Q000628:therapy*; D016032:Randomized Controlled Trials as Topic; D012121:Respiration, Artificial; D012306:Risk; D013990:Tidal Volume; D016896:Treatment Outcome