A cardiopulmonary bypass device may include a first tube configured for connection to a vein and a second tube configured for connection to an artery. The device may further include a pump connected between the first and second tubes. In a first mode, the pump may pump fluid in one direction and in a second mode, the pump may pump fluid in the opposite direction. A control unit may be coupled to the pump to control its operation. Lungs may functions as the oxygenator of the cardiopulmonary bypass device.