Method for regulating the supply of substituate during extracorporeal blood treatment and extracorporeal blood treatment device comprising a unit for regulating the supply of substituate

An apparatus for extracorporeal blood treatment, comprising:

• an extracorporeal blood circuit comprising a blood pump;
• a dialyzing fluid system, comprising a dialyzing fluid supply line, a dialyzing fluid discharge line having incorporated therein a dialyzing fluid pump, and an ultrafiltrate line that branches off of the dialyzing fluid discharge line and has incorporated therein an ultrafiltrate pump;
• a dialyzer divided by a semipermeable membrane into a blood chamber and a dialyzing fluid chamber, the blood chamber being part of the extracorporeal blood circuit, the dialyzing fluid chamber being part of the dialyzing fluid system, and the blood pump being arranged along the extracorporeal blood circuit upstream of the blood chamber;
• a balancing device that is in fluid communication with the dialyzer via a dialyzing fluid supply line and that is located upstream of the dialyzer, said balancing device comprising a first balancing chamber and a second balancing chamber, wherein the first balancing chamber and the second balancing chamber are configured to be operated anti-cyclically, and the balancing device being configured so that that only as much dialyzing fluid can flow via the dialyzing fluid supply line as dialyzing fluid can flow away via the dialyzing fluid discharge line;
• a substituate supply device comprising a first substituate pump, a substituate supply, and a substituate line, the substituate supply device being in fluid communication with the extracorporeal blood circuit via the substituate line, the substituate supply device being configured to supply substituate at a preset substituate rate to the extracorporeal blood circuit;
• a sensor system comprising a blood pressure sensor in sensing communication with the extracorporeal blood circuit downstream of the blood chamber, the blood pressure sensor being configured to generate a blood pressure signal, and the blood pressure sensor being connected to at least two data lines;
• a control and computing unit in communication, through data lines including the at least two data lines, with the sensor system, the blood pump, and the first substituate pump,
• wherein the control and computing unit is configured to (1) calculate a first evaluation quantity (HEMO_Priority) based on a sensed transmembrane pressure or variable correlating with the transmembrane pressure, (2) calculate a second evaluation quantity (BLKD_Priority) based on a sensed longitudinal flow resistance or variable correlating with the longitudinal flow resistance, (3) form an evaluation pair (HEMO_Priority/BLKD_Priority) from the first evaluation quantity and the second evaluation quantity, and (4) regulate the supply of substituate based on the evaluation pair,
• wherein the apparatus comprises a memory having stored therein a two-dimensional matrix of evaluation pairs and that assigns to each evaluation pair a value corresponding to a required change in substituate rate,
• wherein the apparatus is configured to compare the evaluation pair formed by the control and computing unit to the evaluation pairs of the two-dimensional matrix, and regulate the substituate rate by changing the substituate rate by a value corresponding to a required change and assigned to the evaluation pair by the two-dimensional matrix,
• wherein the sensor system further comprises:
• a first pressure sensor in communication with the dialyzing fluid system upstream of the dialyzing fluid chamber and located along the dialyzing fluid supply line, the first pressure sensor being configured to sense a first pressure and to generate a first pressure signal;
• and
• a second pressure sensor in communication with the dialyzing fluid system downstream of the dialyzing fluid chamber and located along the dialyzing fluid discharge line, the second pressure sensor being configured to sense a second pressure and to generate a second pressure signal,
• wherein the at least two data lines of the sensor system comprise a first blood pressure data line and a second blood pressure data line, and the control and computing unit is configured to receive the first and second pressure signals via respective data lines including the first and second blood pressure data lines,
• wherein the blood pump is configured to generate pressure pulses in the extracorporeal blood circuit upstream of the dialyzer, the semipermeable membrane is configured to transmit and attenuate the pressure pulses, and the control and computing unit is configured to split up a pressure signal measured downstream of the dialyzer into a fundamental component and at least one harmonic, the longitudinal flow resistance or the variable correlating with the longitudinal flow resistance being determined based on a ratio of the fundamental component and the at least one harmonic,
• wherein the sensor system, together with the control and computing unit, is configured to determine the transmembrane pressure, or the variable correlating with the transmembrane pressure, via the blood pressure signal, the first pressure signal, and a second pressure signal,
• wherein the sensor system, together with the control and computing unit, is also configured to determine the longitudinal flow resistance, or the variable correlating with the flow resistance, via the blood pressure signal but not the first pressure signal, and
• wherein the first evaluation quantity is scaled to be within an evaluation scale of 0 to 100%, the second evaluation quantity is scaled to be within an evaluation scale of 0 to 100%, the two-dimensional matrix comprises a two-dimensional coordinate system, and the evaluation pair comprises a point in the two-dimensional coordinate system.