Biomedical appliance, comprising: - a device for the oxygenation of blood having at least an inlet fitting and at least an outlet fitting for blood; - a circuit for the pre-filling of said device for the oxygenation; - at least a bag for containing a liquid substance having at least a first and a second mouths, distinct from one another, to allow the liquid substance to come out and reinfuse, respectively; where said circuit comprises: - at least a supply line communicating on one side with the first mouth of said bag and on the other side with the inlet fitting of the device for the oxygenation; - manual pumping means arranged along said supply line and which can be operated to suction the liquid substance from said bag and to convey the liquid substance suctioned this way into the device for the oxygenation; - at least a shunt line which branches out from said supply line and placed between the first mouth of said bag and the inlet fitting of said device for the oxygenation, and that said pumping means are associated with said shunt line; and wherein said circuit comprises - valve means (25, 26) arranged only along said supply line and which can be operated during the suction and conveying of the liquid substance to prevent at least the substance itself from flowing from the device for the oxygenation towards said pumping means and from the latter towards said bag, respectively; where said valve means (25, 26) comprise first and second valve means arranged on opposite sides of said pumping means, said first valve means comprising an unidirectional valve placed between said bag and said shunt line to prevent the liquid substance from flowing towards the bag itself and said second valve means comprising an unidirectional valve placed between said shunt line and said device for the oxygenation to prevent the liquid substance from flowing towards the shunt line itself; - at least a return line, distinct from said supply line, communicating on one side with the outlet fitting of the device for the oxygenation and on the other side directly connected with the second mouth of said bag, said return line being suitable for reintroducing the liquid substance that comes out of said device for the oxygenation, along with the air contained in same, inside said bag. - a device for the oxygenation of blood having at least an inlet fitting and at least an outlet fitting for blood; - a circuit for the pre-filling of said device for the oxygenation; - at least a bag for containing a liquid substance having at least a first and a second mouths, distinct from one another, to allow the liquid substance to come out and reinfuse, respectively; - at least a supply line communicating on one side with the first mouth of said bag and on the other side with the inlet fitting of the device for the oxygenation; - manual pumping means arranged along said supply line and which can be operated to suction the liquid substance from said bag and to convey the liquid substance suctioned this way into the device for the oxygenation; - at least a shunt line which branches out from said supply line and placed between the first mouth of said bag and the inlet fitting of said device for the oxygenation, and that said pumping means are associated with said shunt line; and wherein said circuit comprises - valve means (25, 26) arranged only along said supply line and which can be operated during the suction and conveying of the liquid substance to prevent at least the substance itself from flowing from the device for the oxygenation towards said pumping means and from the latter towards said bag, respectively; where said valve means (25, 26) comprise first and second valve means arranged on opposite sides of said pumping means, said first valve means comprising an unidirectional valve placed between said bag and said shunt line to prevent the liquid substance from flowing towards the bag itself and said second valve means comprising an unidirectional valve placed between said shunt line and said device for the oxygenation to prevent the liquid substance from flowing towards the shunt line itself; - at least a return line, distinct from said supply line, communicating on one side with the outlet fitting of the device for the oxygenation and on the other side directly connected with the second mouth of said bag, said return line being suitable for reintroducing the liquid substance that comes out of said device for the oxygenation, along with the air contained in same, inside said bag.