Variable versus conventional lung protective mechanical ventilation during open abdominal surgery (PROVAR): a randomised controlled trial

Br J Anaesth. 2018 Mar;120(3):581-591. doi: 10.1016/j.bja.2017.11.078. Epub 2017 Dec 1.


Background: Experimental studies showed that controlled variable ventilation (CVV) yielded better pulmonary function compared to non-variable ventilation (CNV) in injured lungs. We hypothesized that CVV improves intraoperative and postoperative respiratory function in patients undergoing open abdominal surgery.

Methods: Fifty patients planned for open abdominal surgery lasting >3 h were randomly assigned to receive either CVV or CNV. Mean tidal volumes and PEEP were set at 8 ml kg-1 (predicted body weight) and 5 cm H2O, respectively. In CVV, tidal volumes varied randomly, following a normal distribution, on a breath-by-breath basis. The primary endpoint was the forced vital capacity (FVC) on postoperative Day 1. Secondary endpoints were oxygenation, non-aerated lung volume, distribution of ventilation, and pulmonary and extrapulmonary complications until postoperative Day 5.

Results: FVC did not differ significantly between CVV and CNV on postoperative Day 1, 61.5 (standard deviation 22.1) % vs 61.9 (23.6) %, respectively; mean [95% confidence interval (CI)] difference, -0.4 (-13.2-14.0), P=0.95. Intraoperatively, CVV did not result in improved respiratory function, haemodynamics, or redistribution of ventilation compared to CNV. Postoperatively, FVC, forced expiratory volume at the first second (FEV1), and FEV1/FVC deteriorated, while atelectasis volume and plasma levels of interleukin-6 and interleukin-8 increased, but values did not differ between groups. The incidence of postoperative pulmonary and extrapulmonary complications was comparable in CVV and CNV.

Conclusions: In patients undergoing open abdominal surgery, CVV did not improve intraoperative and postoperative respiratory function compared with CNV.

Clinical trial registration: NCT 01683578.

Trial registration: NCT01683578.

Keywords: Abdominal surgery; General anaesthesia; Lung protective ventilation; Mechanical ventilation; Variable ventilation.

Publication types

  • Comparative Study
  • Randomized Controlled Trial

MeSH terms

  • Abdomen / surgery*
  • Adult
  • Aged
  • Aged, 80 and over
  • Female
  • Humans
  • Lung / physiopathology*
  • Male
  • Middle Aged
  • Postoperative Complications / prevention & control*
  • Respiration Disorders / physiopathology
  • Respiration Disorders / prevention & control*
  • Respiration, Artificial / methods*
  • Time Factors
  • Total Lung Capacity
  • Treatment Outcome

Associated data