We read with great interest the paper of Giani and colleagues titled «Prone positioning during venovenous extracorporeal membrane oxygenation for acute respiratory distress syndrome: a pooled individual patient data analysis» published in the critical care journal [1]. We are surprised that their meta-analysis failed to show a survival beneft for prone positioning during venovenous extracorporeal membrane oxygenation (VV ECMO). We would like to postulate that this was due to the limitation of the statistical methods.