Abstract: A valve for a medical ventilator comprising a hollow flexible body having at least one outwardly bulging area with a curved inner surface. The hollow flexible body further comprises an inwardly protruding abuttable area positioned between two fixed end points. Further the valve comprises a flow channel located inside said hollow flexible body for passage of a fluid between an inlet and an outlet, a valve seat centrally positioned in said flow channel and an annular element circumferentially arranged around said hollow flexible body. The annular element is arranged to be movable in an axial direction along the flow channel by an actuator unit, and whereby said abuttable area is at least partially repositioned and/or reshaped to control a flow of the fluid through the flow channel.