A paracorporeal respiratory assist lung (900), comprising a housing (920) having an outer body including an upper portion and a lower portion an upper gas port (945) located on the upper portion a lower gas port (940) located on the lower portion an upper blood inlet (930) located on the upper portion a blood outlet (935) located on the housing and disposed away from the upper blood inlet a plurality of gas permeable fiber membranes configured to form a stationary fiber bundle (950) disposed within the housing and connected to and in fluid communication with the upper gas port and lower gas port, the stationary fiber bundle extending from about the upper portion to about the lower portion of the housing to define a length of the fiber bundle a recirculation gap (990) configured between the housing and the fiber bundle a rotatable core (960) disposed within the fiber bundle a blood distribution impeller (970) embodied within the rotatable core that is in fluid communication with the upper blood inlet and an internal gap (992) configured between the rotatable core and the fiber bundle.
