The increasing demand on available donor organs makes isolated machine perfusion an attractive tool to improve graft quality prior to implantation. The present study focuses on the role of red blood cells in normothermic organ perfusion by using an ex vivo pig kidney model. The study aims to analyze if high renal flow rates during cell free perfusion compared to red blood cell supplemented solution during long-term perfusion could be detrimental and if high oxygen partial pressures in perfusate may negatively impact organ integrity. The research is intended to contribute to a more facilitated and safe clinical application of normothermic perfusion technique prior to transplantation.