The device (1) for the continuous monitoring of blood characteristic quantities in an external cardiovascular supporting circuit (2), said circuit (2) comprising a venous line (3), an oxygenator (4), a pump (5), and an arterial line (6), comprising: a sensor (7) suitable for the measurement of the venous saturation (SAT V) and a sensor (8) suitable for the measurement of the arterial saturation (SAT A) of oxygen； a sensor (11) suitable for the measurement of the flow of blood (Qb) sent by the pump (5) to the oxygenator (4)； a sensor (12) suitable for the measurement of the hemoglobin (Hb)； data entering means by the operator； an electronic control unit (14) provided with a microprocessor (15) and operationally connected to a display (16), and further comprising a sensor (19) suitable for the measurement of the flow of work gas (Gf) and a capnometer (20) adapted to measure the concentration of carbon dioxide in the blood； wherein said microprocessor (15) is provided with means adapted to calculate the quantity relating to the amount of carbon dioxide removed by the oxygenator (V`CO2ML) and the quantity relating to the amount of oxygen transferred by the oxygenator (V`CO2ML), the microprocessor (15) being programmed to display in numerical form on the display (16) the values of all the quantities measured and calculated and in graphic form at least some of said values, being further provided means for acquiring the quantity relating to the amount of carbon dioxide removed from the patient's lung (V`CO2NL) and the microprocessor being provided with means adapted to calculate the quantity relating to the amount of total removed carbon dioxide (V'CO2total).
