Systems, devices, and methods are provided for removing carbon dioxide from a target fluid, such as, for example, blood, to treat hypercarbic respiratory failure or another condition. A device is provided including first and second membrane components for removing dissolved gaseous carbon dioxide and bicarbonate from the fluid, which can be done simultaneously. The device can be in the form of a cartridge configured for use in a dialysis system. A method of treatment is also provided, involving drawing blood from a patient and bringing the patient's blood in contact with a first membrane component having a sweep gas passing therethrough, and a second membrane component having a dialysate passing therethrough. The dialysate's composition can be selected such that charge neutrality is maintained.