A miniaturized cardiopulmonary bypass circuit for a mouse comprises at least one venous catheter connected to a patient, a dual channel peristaltic pump having one channel to move the blood by tubing from the patient, an oxygenator that removes gases from the blood and mixes the blood with fresh gases to oxygenate the blood, the blood being moved from the oxygenator to the arterial catheter by the dual channel peristaltic pump, and an arterial catheter. The blood is pumped by a two-channel roller pump into an inlet nozzle, where the flow of blood is transformed from tubular flow to planar flow. Gas exchange occurs inside the case while the blood flows down the central component. Blood then flows down the central component into the arterial reservoir. The arterial reservoir is connected to the second channel of the pump, and returned to the patient through a cannula.