ICU Physiology in 1,000 Words "The Hemodynamics of Prone" by Jon-Emile S. Kenny MD A physiological maelstrom has recently swirled about the hemodynamic effects of the prone position in severe ARDS [1-5]; but how exactly does this maneuver alter the cardiovascular system? A good approach to this problem is a Guytonian one whereby we consider the consequences of the prone position firstly on venous return and secondly on cardiac function.