Major surgery is associated with high complication rates. Several risk scores exist to assess individual patient risk before surgery but have limited precision.

Novel prognostic factors can be included as additional building blocks in existing prediction models. A candidate prognostic factor, measured by cardiopulmonary exercise testing, is ventilatory efficiency (VE/VCO2).

The aim of this systematic review was to summarise evidence regarding VE/VCO2 as a prognostic factor for postoperative complications in patients undergoing major surgery.

A medical library specialist developed the search strategy.

No database-provided limits, considering study types, languages, publication years, or any other formal criteria were applied to any of the sources.

Two reviewers assessed eligibility of each record and rated risk of bias in included studies.