Machine for extracorporeal treatment of blood

A machine for extracorporeal treatment of blood, comprising:

• a blood treatment device having a blood chamber and a fluid chamber, separated one from another by the semipermeable membrane;
• an extracorporeal blood circuit which comprises an arterial line, for taking blood removed from a patient to an inlet of the blood chamber, and a venous line, for returning treated blood from an outlet of the blood chamber to the patient;
• an infusion line connected to the extracorporeal blood circuit and provided with an infusion pump for injecting into the extracorporeal blood an infusion flow of substitution liquid;
• at least an ultrafiltration pump connected to said fluid chamber and configured for ultrafiltration of a liquid through the semipermeable membrane of the blood treatment device;
• at least a blood pump for supplying a flow of liquid to the blood chamber of said blood treatment device;
• at least a first sensor configured for measuring an ultrafiltration flow rate through said semipermeable membrane;
• at least a second sensor configured for measuring an infusion flow rate through said infusion line;
• at least a third sensor for measuring a transmembrane pressure across said semipermeable membrane;
• a controller configured for performing the following operations:
• determining at least one value of an infusion flow rate and at least one value of a transmembrane pressure in a first operating situation of said ultrafiltration pump;
• commanding said ultrafiltration pump to change into a second operating situation which is different from the first operating situation thereof;
• determining at least one value of an infusion flow rate and at least one value of a transmembrane pressure in said second operating situation;
• checking whether said values related to two different operating situations satisfy a predetermined relation with a reference value;
• generating a signal in consequence of said check;
• depending upon the outcome of said check repeating or not the above-described operations;
• and
• finding a maximum or nearly-maximum value for the infusion flow rate as a function of the transmembrane pressure.