An artificial lung including a housing having a circular outer wall being enclosed by a first surface and a second surface to define an interior volume, a blood inlet port to permit inlet flow of blood to the housing, a blood outlet port to permit outlet flow of the blood from the housing, a gas inlet port to permit inlet flow of a gas to the housing, a gas outlet port to permit outlet flow of the gas from the housing, and a plurality of baffles concentrically disposed within the housing. The baffles are positioned to define a flow path between the blood inlet port and the blood outlet port. Each of the baffles includes a gate opening to permit flow of the blood along the flow path. A fiber bundle is disposed between the baffles within the flow create mixing and improve gas exchange efficiency.