Pulsatile volume displacement pump. (A) Illustration of pulsatile volume displacement pump demonstrating how a typical pump works. Blood flow enters the pump as the flexible diaphragm/membrane is pulled downward in the image. This movement is driven by a pusher plate controlled by a motor. The mechanism varies, depending on the specific pump. With one-way valves at the inlet and outlet, this leads to fluid entering from the ventricle, while the outflow valve remains closed. Flow exits the pump as the pusher plate pushes upward, thereby deflecting the flexible diaphragm, which increases pressure within the pump. The pressure change closes the inflow valve and opens the outflow valve. Blood flow is then driven out of the pump. (B) The shear stress distribution within an example pediatric 15 cubic centimeter volume displacement pump during the ejection of blood from the pump.⁸ Note that shear stress is pump-specific and depends on the pump volume. It also varies in time and along the depth of the image.