Open Access Open Badges Study protocol

Variable versus conventional lung protective mechanical ventilation during open abdominal surgery: study protocol for a randomized controlled trial

Peter M Spieth1, Andreas Güldner1, Christopher Uhlig1, Thomas Bluth1, Thomas Kiss1, Marcus J Schultz2, Paolo Pelosi3, Thea Koch1 and Marcelo Gama de Abreu1*

Author Affiliations

1 Pulmonary Engineering Group, Department of Anesthesiology and Intensive Care Medicine, University Hospital Dresden, Technische Universität Dresden, Fetscherstrasse 74, 01307 Dresden, Germany

2 Department of Intensive Care Medicine, Academic Medical Center at the University of Amsterdam, Meidbergdreef 9, 1105 AZ Amsterdam, The Netherlands

3 IRCCS AOU San Martino-IST, Department of Surgical Sciences and Integrated Diagnostics, University of Genoa, Largo Roseanna Benzi 8, 16132 Genoa, Italy

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Trials 2014, 15:155  doi:10.1186/1745-6215-15-155

Published: 2 May 2014



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.


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.


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.

Trial registration NCT01683578 (registered on September 3 3012).

Mechanical ventilation; Variable ventilation; General anesthesia; Abdominal surgery; Lung protective ventilation; Pulmonary complications