Abstract: The task was to create a multifunctional system for the extracorporeal circulation (ECC) for a heart-lung bypass, which primarily makes use of the advantages of a minimized ECC system, but which in the case of need at any time can also be used universally and at low risk as another closed and open ECC system. Besides, it shall provide the option of an automatic negative pressure and volume compensation when being used as minimized ECC system. According to the invention, a special reservoir (48), particularly a venous cardiotomy reservoir, for blood and/or priming solution is presented, which consists of a form-stable bottom part (57), wherein a level sensor (57) can be integrated, and a flexible part (56) located on top of it, which seeks to increase its volumetric capacity. The equipment is used in the artificial circulation of patients by the use of a heart-lung machine.