Extracorporeal blood treatment device with function-monitoring system

An extracorporeal blood treatment device having a function-monitoring system, wherein the extracorporeal blood treatment device comprises an afferent line and an efferent line for connecting to the vascular system of a patient, wherein in a first circuit the extracorporeal blood treatment device has at least one first pump arranged between the afferent line and the efferent line for moving the patient's blood, and comprises a temperature adjusting device in a second, liquid-filled circuit that is thermally connected to the first circuit of the extracorporeal blood treatment device by a heat exchanger,

• wherein the function-monitoring system comprises:
• a. a temperature sensor TS2up arranged in the second circuit upstream of the heat exchanger and a temperature sensor TS2down arranged in the second circuit downstream of the heat exchanger;
• b. a temperature sensor TS1down arranged in the efferent line of the first circuit of the extracorporeal blood treatment device downstream of the heat exchanger;
• and
• c. a computer system connected to the temperature sensors (TS2up, TS2down, TS1down) and the temperature adjusting device, and configured to use the temperature adjusting device to induce a temperature bolus in the second circuit of the extracorporeal blood treatment device, to record the temperatures T2up, TS2down, TS1down detected at the temperature sensors TS2up, TS2down, TS1down, respectively, as a function of time and to determine and evaluate corresponding thermodilution curves (TDK), and is furthermore configured to relate TDK2down and TDK1down to one another and to determine an indicator of the extracorporeal blood treatment device function from a ratio of TDK2down and TDK1down, and wherein the indicator of the functionality of the extracorporeal blood treatment device is an indicator of a functionality of a membrane in the extracorporeal blood treatment device.