A new method for long-term respiratory assistance using a right ventricular assist device (RVAD) system and a membrane oxygenator (MO) was designed and evaluated. An air-driven RVAD was implanted between the right atrium and the pulmonary artery in five goats and an MO was set on the outlet conduit of the RVAD 2 weeks postoperatively. Two types of MOs [the SciMed (Life Systems) silicone sheet MO and a prototype MO using a novel multilayered composite membrane] were used in this study. Respiratory support with this system under systemic heparinization could be conducted for 4-8 days without major problems accompanied with conventional extracorporeal membrane oxygenation (ECMO) such as surgical bleeding, destruction of the blood components, serum leakage, insufficient bypass flow, and fatal systemic thrombosis. This method opened the possibility for ECMO to be used as a bridge before lung or heart-lung transplantation.