Abstract: A device for the continuous monitoring of blood characteristic quantities in an external cardiovascular supporting circuit, said circuit including a venous line which conveys blood from the patient to an oxygenator, and along which at least one pump is arranged, and an arterial line which returns blood from the oxygenator to the patient, where said oxygenator comprises at least one blood inlet port connected to said venous line and at least one blood outlet port connected to said arterial line, at least one inlet channel and at least one outlet channel of a work gas intended to supply oxygen to the blood and/or to remove carbon dioxide from the same.