Extracorporeal membrane oxygenation (ECMO) is a technique that can support gas-exchange and cardiac function in patients with acute respiratory or cardiac failure that is not responsive to conservative treatment. ECMO is a high-risk procedure in critically ill patients and both technical and patient-related complications frequently occur. We report on a patient with end-stage pulmonary fibrosis (histiocytosis x), in whom ECMO was used as bridge to urgent lung transplantation. Respiratory insufficiency necessitating ECMO therapy was due to spontaneous pneumothorax with bronchopleural fistula. Access was initially made by femoral veno-venous canulation. Due to right heart failure, access was switched to veno-arterial using the two existing canulae as efferent system and implanting a third canula on the femoral artery using a graft. Despite marked hemodynamic improvement after this intervention, high flow rates creating high premembrane pressures were required to ensure oxygenation. High levels of carboxyhemoglobin (COHb) occurred, most likely due to massive mechanical hemolysis in the ECMO circuit. This may have had detrimental effects by further complicating tissue oxygenation. We recommend that COHb should routinely be checked in ECMO patients.