We will search the Cochrane Database of Systematic Reviews and include reviews published from March 2011 corresponding to the latest update in the Cochrane risk of bias tool. 
Cochrane Database of Systematic Reviews
We will conduct a meta-epidemiologic study of RCTs included in Cochrane systematic reviews assessing any intervention used in adult patients admitted to the ICU.  The outlined meta-epidemiologic study will assess time trends in risk of bias and sample sizes in RCTs assessing ICU interventions. 
Meta-epidemiologic study