Long term extracorporeal membrane oxygenation can be used in cases of severe lung failure to maintain sufficient gas exchange without the need to apply higher ventilationpressures which damage the lung additionally. The use of cardiopulmonary bypass devices is well established inside the operating room. The usage of such devices as long-term support in the intensive care unit is still experimental and limited to few cases. This is because neither machine architecture nor staff situation provides for the long term application scenario. In the joint research Project %u201Dsmart ECLA%u201D we target an advanced ECMO device featuring an automation system capable of maintaining gas concentrations automatically. One key requirement for systematic controller design is the availability of a process model, which will be presented in this article.