FIG 1.

Search method, screening criteria, and resulting classification of eligible studies and subsequent derivation of component groups. The arrows numbered 1 to 6 indicate the following steps. (1) An electronic search for systematic reviews containing potentially eligible studies was performed using the search terms “ventilator-associated pneumonia,” “mechanical ventilation,” and “intensive care unit,” each combined with either “meta-analysis” or “systematic review,” up to December 2015. (2) Studies were streamed into one of four categories: studies in which there was no intervention (observational studies), studies with topical polymyxin with or without a CC design, and studies of nonpolymyxin methods of VAP prevention. The studies of nonpolymyxin methods of VAP prevention encompass a broad range of methods. (3) The studies were screened against inclusion and exclusion criteria. (4) A hand search was undertaken for additional studies. (5) Eligible studies were then collated, and any duplicate studies were removed. (6) The component groups, being control (rectangles), intervention (ovals), and observation (diamond) groups, were extracted from each study. Note that the total numbers do not tally, as some systematic reviews provided studies in more than one category and some studies provided groups in more than one category.