Volume expansion is a cornerstone treatment of acute circulatory failure like during the early hours in patients with septic shock, but it can be a cause of therapeutic dilemma because fluid overload can lead to acute kidney injury, prolongation of mechanical ventilation, acute respiratory distress syndrome, and higher mortality rates.

       Predicting fluid responsiveness with a reliable, easy, and rapid way is essential to know when to start and when to stop fluid therapy especially as patients may react differently to VE.

         Static hemodynamic parameters like inferior vena cava diameter and central venous pressure are unreliable and cannot predict FR precisely; contrarily, dynamic parameters that depend on cyclic changes in cardiac preload caused by mechanical ventilation, leading to variation of stroke volume or pulse pressure have proven to be reliable when predicting FR in hemodynamically unstable patient

       PPV is a common dynamic parameter that can predict FR reliably and can be recorded through most of recent bedside monitors easily using arterial lines; also, it does not need CO monitoring or any other maneuvers to be done.