title: Variable versus conventional lung protective mechanical ventilation during open abdominal surgery: study protocol for a randomized controlled trial.
abstract: BACKGROUND
  General anesthesia usually requires mechanical ventilation, which is traditionally accomplished with constant tidal volumes in volume- or pressure-controlled modes. Experimental studies suggest that the use of variable tidal volumes (variable ventilation) recruits lung tissue, improves pulmonary function and reduces systemic inflammatory response. However, it is currently not known whether patients undergoing open abdominal surgery might benefit from intraoperative variable ventilation.
  
  
  METHODS
  The PROtective VARiable ventilation trial ('PROVAR') is a single center, randomized controlled trial enrolling 50 patients who are planning for open abdominal surgery expected to last longer than 3 hours. PROVAR compares conventional (non-variable) lung protective ventilation (CV) with variable lung protective ventilation (VV) regarding pulmonary function and inflammatory response. The primary endpoint of the study is the forced vital capacity on the first postoperative day. Secondary endpoints include further lung function tests, plasma cytokine levels, spatial distribution of ventilation assessed by means of electrical impedance tomography and postoperative pulmonary complications.
  
  
  CONCLUSIONS
  We hypothesize that VV improves lung function and reduces systemic inflammatory response compared to CV in patients receiving mechanical ventilation during general anesthesia for open abdominal surgery longer than 3 hours. PROVAR is the first randomized controlled trial aiming at intra- and postoperative effects of VV on lung function. This study may help to define the role of VV during general anesthesia requiring mechanical ventilation.
  
  
  BACKGROUND
  Clinicaltrials.gov NCT01683578 (registered on September 3 3012).
authors.forename: Peter M
authors.initials: PM
authors.lastname: Spieth
authors.forename: Andreas
authors.initials: A
authors.lastname: Güldner
authors.forename: Christopher
authors.initials: C
authors.lastname: Uhlig
authors.forename: Thomas
authors.initials: T
authors.lastname: Bluth
authors.forename: Thomas
authors.initials: T
authors.lastname: Kiss
authors.forename: Marcus J
authors.initials: MJ
authors.lastname: Schultz
authors.forename: Paolo
authors.initials: P
authors.lastname: Pelosi
authors.forename: Thea
authors.initials: T
authors.lastname: Koch
authors.affiliation: Pulmonary Engineering Group, Department of Anesthesiology and Intensive Care Medicine, University Hospital Dresden, Technische Universität Dresden, Fetscherstrasse 74, 01307 Dresden, Germany. mgabreu@uniklinikum-dresden.de.
authors.forename: Marcelo
authors.initials: M
authors.lastname: Gama de Abreu
mesh_terms: D000005:Abdomen / Q000601:surgery*; D000768:Anesthesia, General; D002985:Clinical Protocols; D005858:Germany; D006801:Humans; D007249:Inflammation / Q000175:diagnosis / Q000209:etiology / Q000517:prevention & control*; D007430:Intraoperative Care / Q000379:methods*; D008168:Lung / Q000503:physiopathology; D055370:Lung Injury / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control*; D061646:Operative Time; D012107:Research Design; D012121:Respiration, Artificial / Q000009:adverse effects / Q000379:methods*; D012129:Respiratory Function Tests; D013997:Time Factors; D016896:Treatment Outcome