title: Protective versus Conventional Ventilation for Surgery: A Systematic Review and Individual Patient Data Meta-analysis.
abstract: BACKGROUND
  Recent studies show that intraoperative mechanical ventilation using low tidal volumes (VT) can prevent postoperative pulmonary complications (PPCs). The aim of this individual patient data meta-analysis is to evaluate the individual associations between VT size and positive end-expiratory pressure (PEEP) level and occurrence of PPC.
  
  
  METHODS
  Randomized controlled trials comparing protective ventilation (low VT with or without high levels of PEEP) and conventional ventilation (high VT with low PEEP) in patients undergoing general surgery. The primary outcome was development of PPC. Predefined prognostic factors were tested using multivariate logistic regression.
  
  
  RESULTS
  Fifteen randomized controlled trials were included (2,127 patients). There were 97 cases of PPC in 1,118 patients (8.7%) assigned to protective ventilation and 148 cases in 1,009 patients (14.7%) assigned to conventional ventilation (adjusted relative risk, 0.64; 95% CI, 0.46 to 0.88; P < 0.01). There were 85 cases of PPC in 957 patients (8.9%) assigned to ventilation with low VT and high PEEP levels and 63 cases in 525 patients (12%) assigned to ventilation with low VT and low PEEP levels (adjusted relative risk, 0.93; 95% CI, 0.64 to 1.37; P = 0.72). A dose-response relationship was found between the appearance of PPC and VT size (R2 = 0.39) but not between the appearance of PPC and PEEP level (R2 = 0.08).
  
  
  CONCLUSIONS
  These data support the beneficial effects of ventilation with use of low VT in patients undergoing surgery. Further trials are necessary to define the role of intraoperative higher PEEP to prevent PPC during nonopen abdominal surgery.
authors.affiliation: From the Department of Intensive Care, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands (A.S.N., S.N.T.H., J.M.B., M.W.H., E.K.W., M.J.S.); Department of Pneumology, Heart Institute (INCOR), Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil (A.S.N., C.S.V.B.); Department of Critical Care Medicine, Hospital Israelita Albert Einstein, São Paulo, Brazil (A.S.N., C.S.V.B.); Department of Anaesthesiology, Düsseldorf University Hospital, Düsseldorf, Germany (M. Beiderlinden, T.T.); Department of Anaesthesiology, Marienhospital Osnabrück, Osnabrück, Germany (M. Beiderlinden); Division of Pulmonary and Critical Care Medicine, Mayo Clinic, Rochester, Minnesota (M. Biehl, O.G., J.S.); Department of Anesthesiology, Hospital Universitar I Germans Trias I Pujol, Barcelona, Spain (J.C.); Department of Anesthesiology, University of Colorado, Aurora, Colorado (A.F.-B., P.M.); Department of Anesthesiology and Critical Care Medicine, Estaing University Hospital, Clermont-Ferrand, France (E.F.); Department of Medical Sciences, Section of Clinical Physiology, University Hospital, Uppsala, Sweden (G.H.); Department of Critical Care Medicine and Anesthesiology (SAR B), Saint Eloi University Hospital, Montpellier, France (S.J.); Department of Anesthesiology and Intensive Care Medicine, Otto-von-Guericke-University Magdeburg, Magdeburg, Germany (A.K., T.S.); Department of Anaesthesiology, Pharmacology and Intensive Care, Faculty of Medicine, University Hospital of Geneva, Geneva, Switzerland (M.L.); State Key Laboratory of Oncology of South China, Sun Yat-sen University Cancer Center, Guangzhou, Guangdong, People's Republic of China (W.-Q.L.); Department of Anesthesiology, The Warren Alpert School of Brown University, Providence, Rhode Island (A.D.M.); Department of Anesthesiology, Hospital for Special Surgery, Weill Medical College of Cornell University, New York, New York (S.G.M.); Department of Intensive Ca
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mesh_terms: D006801:Humans; D011175:Positive-Pressure Respiration / Q000379:methods* / Q000592:standards; D016032:Randomized Controlled Trials as Topic / Q000379:methods / Q000592:standards; D012121:Respiration, Artificial / Q000379:methods / Q000592:standards; D013223:Statistics as Topic / Q000379:methods*; D013990:Tidal Volume / Q000502:physiology