Homogenisation of the distribution of lung aeration as a result of moving from a) the supine to b) the prone position during acute respiratory distress syndrome. Homogenisation of the distribution of lung aeration as a result of moving from a) the supine to b) the prone position during acute respiratory distress syndrome. The red circle represents the heart. White circles: normally aerated lung areas; grey circles: poorly aerated lung areas; black rectangle: non-aerated lung areas; green rectangle: consolidated lung areas. Claude Guérin Eur Respir Rev 2014;23:249-257 ©2014 by European Respiratory Society