A system for lung assist, comprising: a fiber bundle section (200, 200a) comprising a fiber bundle housing (220, 220a) defining a fiber bundle compartment (222, 222a) therein, a fiber bundle (300, 300a) positioned within the fiber bundle compartment (222, 222a), the fiber bundle (300, 300a) comprising a plurality of hollow gas permeable fibers, the plurality of hollow gas permeable fibers being adapted to permit diffusion of gas between blood and an interior of the plurality of hollow gas permeable fibers, the plurality of hollow gas permeable fibers being positioned such that blood flows around the plurality of hollow gas permeable fibers when flowing through the fiber bundle compartment (222, 222a), the fiber bundle housing (220, 220a) further comprising a gas inlet (260, 260a) in fluid connection with the fiber bundle housing (220, 220a) and in fluid connection with inlets of the plurality of hollow gas permeable fibers, a gas outlet (264, 264a) in fluid connection with the fiber bundle housing (220, 220a) and in fluid connection with outlets of the plurality of hollow gas permeable fibers, a blood outlet (250, 250a) in fluid connection with a first end of the fiber bundle (300, 300a) and a first interface (270, 270a), and a base section comprising a housing comprising a pressurizing section, which comprises a pressurizing compartment, and an interface section, the interface section comprising an extending section which extends at an angle from the pressurizing section and a second interface formed on the extending section and configured to form a releasable, sealing connection with the first interface (270, 270a) of the fiber bundle section (200, 200a), a pressurizing mechanism within the pressurizing compartment, a blood inlet in fluid connection with the pressurizing compartment and a conduit in fluid connection with the pressurizing compartment at a first end of the conduit via which pressurized fluid exits the pressurizing compartment, the conduit comprising a flow channel which extends through the extending section to a second end in the second interface, wherein the second end of the conduit is placed in fluid connection with a second end of the fiber bundle (300, 300a) when the fiber bundle housing (220, 220a) of the fiber bundle section (200, 200a) is connected to housing of the base section via the first interface (270, 270a) and the second interface. a fiber bundle section (200, 200a) comprising a fiber bundle housing (220, 220a) defining a fiber bundle compartment (222, 222a) therein, a fiber bundle (300, 300a) positioned within the fiber bundle compartment (222, 222a), the fiber bundle (300, 300a) comprising a plurality of hollow gas permeable fibers, the plurality of hollow gas permeable fibers being adapted to permit diffusion of gas between blood and an interior of the plurality of hollow gas permeable fibers, the plurality of hollow gas permeable fibers being positioned such that blood flows around the plurality of hollow gas permeable fibers when flowing through the fiber bundle compartment (222, 222a), the fiber bundle housing (220, 220a) further comprising a gas inlet (260, 260a) in fluid connection with the fiber bundle housing (220, 220a) and in fluid connection with inlets of the plurality of hollow gas permeable fibers, a gas outlet (264, 264a) in fluid connection with the fiber bundle housing (220, 220a) and in fluid connection with outlets of the plurality of hollow gas permeable fibers, a blood outlet (250, 250a) in fluid connection with a first end of the fiber bundle (300, 300a) and a first interface (270, 270a), and a base section comprising a housing comprising a pressurizing section, which comprises a pressurizing compartment, and an interface section, the interface section comprising an extending section which extends at an angle from the pressurizing section and a second interface formed on the extending section and configured to form a releasable, sealing connection with the first interface (270, 270a) of the fiber bundle section (200, 200a), a pressurizing mechanism within the pressurizing compartment, a blood inlet in fluid connection with the pressurizing compartment and a conduit in fluid connection with the pressurizing compartment at a first end of the conduit via which pressurized fluid exits the pressurizing compartment, the conduit comprising a flow channel which extends through the extending section to a second end in the second interface, wherein the second end of the conduit is placed in fluid connection with a second end of the fiber bundle (300, 300a) when the fiber bundle housing (220, 220a) of the fiber bundle section (200, 200a) is connected to housing of the base section via the first interface (270, 270a) and the second interface.