Abstract

When evaluating an innovative intervention in a randomised controlled trial (RCT), choosing an appropriate control intervention is necessary for a clinically meaningful result. An RCT reported in 2000 addressed the relative merits of two tidal volume ventilatory strategies, 6 ml/kg (innovative) and 12 ml/kg (control), in patients with acute respiratory distress syndrome. Critics claim that the 12 ml/kg volume did not represent the clinical practice standard at that time, and that lower tidal volumes had been used in some patients prior to randomisation. The trialists responded that current practice involved the use of a broad range of tidal volumes, including 12 ml/kg. Appropriate control interventions for RCTs can be ensured by: a systematic review of the relevant literature; a formal survey of expert clinicians; and publication of the proposed research protocol to solicit critical appraisal. A global survey of experts during the RCT’s design stage would have been of probative value in determining the appropriate control tidal volume. Hypothetical, but plausible, results of such a survey are presented and examined to demonstrate the value of this method.