Extracorporeal blood treatment device

Abstract

The present invention relates to an extracorporeal blood treatment device having a blood treatment unit 1 divided by a semipermeable membrane 2 into a first compartment 3, which is part of a fluid system II, and a second compartment 4, which is part of an extracorporeal blood circuit I. Furthermore, the present invention relates to a method for operating such a blood treatment device. The blood treatment device according to the present invention comprises a pressure-based control device 32 cooperating with a control unit 31 for the valve device 21, which is designed to establish a fluid connection between the upstream part 20A and the downstream part 20B of the flow path 20 in a special operating mode only if the pressure-based control device 32 detects an operating state that ensures that in this special operating mode the liquid in the flow path 20 flows in the direction of the flow path 10 leading to the outlet 11. It is therefore ensured that the liquid in question can only enter the flow path 10 leading to the outlet 11, but not into another flow path 8 in which new treatment liquid is located.

Description

Technical Field

[0001] The present invention relates to an extracorporeal blood treatment device comprising a blood treatment unit divided by a semipermeable membrane into a first compartment that is part of a fluid system and a second compartment that is part of an extracorporeal blood circuit. The present invention also relates to a method for operating such a blood treatment device.

Background Art

[0002] Known dialysis devices comprise an extracorporeal blood circuit and a dialysis fluid system. The dialysis fluid system comprises a dialysis fluid supply line leading from a dialysis fluid source to a dialysis fluid chamber of a dialyzer and a dialysis fluid discharge line leading from the dialysis fluid chamber of the dialyzer to a drain. The extracorporeal blood circuit comprises an arterial blood line leading from a patient's arterial puncture site to a blood chamber and a venous blood line leading from the blood chamber to a patient's venous puncture site. While dialysis fluid flows through the dialysis fluid chamber of the dialyzer, there is mass transfer between the blood chamber and the dialysis fluid chamber through the semipermeable membrane of the dialyzer.

[0003] The fluid system of a known extracorporeal blood treatment device, e.g., a dialysis device, is generally constructed such that a new medical treatment fluid, e.g., dialysis fluid, flows into a first compartment of the blood treatment unit at a predetermined flow rate and used treatment fluid flows out of the first compartment of the blood treatment unit and into a drain. Thus, the fluid system of a known blood treatment device generally has at least one fluid line and a first flow path designed as a flow path for supplying a new treatment fluid from a fluid source to the first compartment of the blood treatment unit and at least one fluid line and a second flow path designed as a flow path for discharging used treatment fluid from the first compartment of the blood treatment unit to a drain. To reduce the risk of contamination, the first flow path and the second flow path of a known blood treatment device are separated from each other.

[0004] The fluid systems of known blood treatment devices generally have additional flow paths, each required for a particular operating mode. These particular operating modes include, for example, filling the blood treatment device with a cleaning agent and / or a disinfectant for blood treatment, or preparing the blood tubing system. Forming a flow connection between a first flow path and a second flow path during the preparation of blood treatment or during blood treatment in case of a malfunction, thereby bypassing the blood treatment unit, is also a particular operating mode.

[0005] To control the fluid flow, the fluid system of a known blood treatment device can include a valve device having one or more shut-off members, and a control unit for operating the valve device such that the valve device assumes one operating position for one operating mode and another operating position for another operating mode.

[0006] The flow path for a particular operating mode comprises an upstream portion upstream of a valve device having at least one valve, and a downstream portion downstream of the valve device. The valve device is designed such that a fluid connection is established between the upstream and downstream portions of the flow path in a first operating position of the valve device, and the fluid connection is interrupted in a second operating position of the valve device. For an individual operating mode, it may be necessary for the downstream portion of the flow path for the particular operating mode to be in flow connection with a second flow path, such that, when the flow connection of the flow path is not interrupted, a fluid, for example a dialysis fluid, can flow directly from the upstream portion via the second flow path into the drain.

[0007] For example, from EP2844313B1, a dialysis device is known that comprises two separate flow paths through which fresh dialysis fluid and used dialysis fluid flow during blood treatment. The fluid system of the dialysis device has a valve device having a plurality of shut-off members for carrying out a flushing process. SUMMARY OF THE INVENTION

[0008] The object of the present invention is to provide additional safety measures in order to further reduce the risk of contaminating a blood treatment device due to used fluid flowing into new fluid.

[0009] According to the present invention, this object is achieved by the features of the independent claims. The dependent claims relate to preferred embodiments of the present invention.

[0010] The blood treatment device according to the present invention has a valve device provided in a flow path for a special operation mode. The valve device is designed such that a fluid connection is established between the upstream portion and the downstream portion of the flow path for the special operation mode in the first operating position of the valve device, and the fluid connection is interrupted in the second operating position of the valve device. Further, the blood treatment device has a pressure-based check device that interacts with a control unit for operating the valve device, and the pressure-based check device is configured such that the fluid connection between the upstream portion and the downstream portion of the flow path for the special operation mode can be established only when the pressure-based check device detects an operating state in which the fluid in the flow path for the special operation mode surely flows toward a flow path leading to a drain. Thereby, the problematic fluid can only flow into the flow path leading to the drain, and it is ensured that the fluid does not enter another flow path where the new treatment fluid is located.

[0011] Regarding the monitoring of the flow direction according to the present invention, in the special operation mode, it is basically irrelevant which fluid line the fluid flows through or what kind of fluid it is.

[0012] In a preferred embodiment, the pressure-based check device includes an upstream pressure gauge for measuring an upstream pressure in the upstream portion of the flow path for the special operation mode, a downstream pressure gauge for measuring a downstream pressure in the downstream portion of the flow path, and an evaluation unit that receives measurement signals from the upstream pressure gauge and the downstream pressure gauge. The evaluation unit is configured such that the upstream pressure is compared with the downstream pressure, and when the upstream pressure is higher than the downstream pressure, it indicates an operating state in which the fluid is surely flowing toward the second flow path.

[0013] The control unit and / or evaluation unit can be part of the central control and arithmetic unit of the blood treatment device. The pressure can be measured by a pressure gauge arranged in the upstream or downstream part of the flow path for a special operation mode, or by a pressure gauge arranged in a fluid line fluidly connected to the part in question. It is preferable to use a pressure gauge already provided in a conventional blood treatment device for monitoring blood treatment.

[0014] When a malfunctioning operating state is indicated, various countermeasures can be taken. For example, an acoustic, visual, or tactile alarm can be issued to warn the medical staff and they can respond accordingly.

[0015] The control unit of the valve device or the central control and arithmetic unit of the blood treatment device can be configured to introduce countermeasures to bring about a correct pressure state or to perform method steps when receiving a signal from an evaluation unit signaling a malfunctioning operating state.

[0016] In another embodiment, the pressure-based check device generates an enable signal for the control unit, and the control unit is configured to operate the valve device so that the valve device takes the first operating position only when the control unit receives a control signal and an enable signal for switching the control unit to the special operation mode. As a result, a flow connection can be established by the valve device only when it is ensured that no fluid enters the part of the fluid system where the new treatment fluid is located.

[0017] In another embodiment, the fluid system of the blood treatment device needs to have a special structure in which a first flow path is divided by a semipermeable membrane into a first filter chamber and a second filter chamber of a first filter. This filter can function as a sterilizing filter for fresh dialysis fluid. The upstream portion of the first flow path connects a fluid source to the first filter chamber of the filter, and the downstream portion of the first flow path connects the second filter chamber of the filter to the inlet of the first compartment of the blood treatment unit. In this embodiment, the upstream portion of the flow path for the special operation mode can be a line portion that is fluidly connected to the downstream portion of the first flow path. The downstream portion of the flow path for the special operation mode is fluidly connected to the second flow path and thus to the drain, so that in the special operation state, a fluid connection can be established downstream of the sterilizing filter between the first flow path for the new treatment fluid and the second flow path for the used treatment fluid, thereby bypassing the blood treatment unit.

[0018] In this embodiment, the first pressure gauge can be arranged downstream of the first flow path, and the second pressure gauge can be arranged in the second flow path. If pressure gauges are already provided in other fluid lines of the blood treatment device to monitor pressure, it may be convenient not to directly arrange pressure gauges in the upstream and downstream portions of the flow path for the special operation mode.

[0019] In another embodiment where the extracorporeal blood circuit includes a venous blood line and an arterial blood line, the upstream portion of the flow path for the special operation mode is a line portion of the venous blood line or a line portion that is fluidly connected to the venous blood line. In this embodiment, by monitoring the flow direction, it becomes possible for the fluid to flow only from the venous blood line to the drain, the first pressure gauge can be arranged in the venous blood line, and the second pressure gauge can be arranged in the second flow path.

[0020] In the method according to the invention for operating an extracorporeal blood treatment device, before a flow connection is established between an upstream part of a flow path for a special operating state and a downstream part of the flow path for the special operating state that is flow-connected to a second flow path, the upstream pressure in the upstream part of the flow path for the special operating state and the downstream pressure in the downstream part are measured. The flow connection between the upstream part and the downstream part of the flow path for the special operating state is established only if the upstream pressure is higher than the downstream pressure.

[0021] Two embodiments of the invention are described in detail below with reference to the following drawings.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0023] A blood treatment device, in particular a blood (dialysis) filtration device, is equipped for operation with a blood treatment unit 1, in particular a dialyzer, which is divided by a semipermeable membrane 2 into a first compartment 3, in particular a dialysate chamber, and a second compartment 4, in particular a blood chamber.

[0024] A blood supply line 5 to which a blood pump 6 is connected leads to an inlet 4a of the blood chamber 4, and a blood return line 7 leads out from an outlet 4b of the blood chamber 4. The blood supply line 5 and the blood return line 7, together with the blood chamber 4, form an extracorporeal blood circuit I of the blood treatment device. The fluid system II of the blood treatment device is described below. The blood supply line 5 and the blood return line 7 are part of a tube system connected to the blood treatment device.

[0025] The fluid system II of the blood treatment device, particularly the dialysis fluid system, comprises a dialysis fluid supply line 8 leading from a dialysis fluid source 9 to an inlet 3a of the dialysis fluid chamber 3, and a dialysis fluid discharge line 10 leading from an outlet 3b of the dialysis fluid chamber 3 to a drain 11. The dialysis fluid supply line 8 has a first portion 8A leading from the dialysis fluid source 9 to a first filter chamber 12A of a first sterilizing filter 12, and the first sterilizing filter 12 is divided by a semipermeable membrane 12C into a first filter chamber 12A and a second filter chamber 12B. One chamber 13A of a balancing device 13 is connected to the first portion 8A of the dialysis fluid supply line 8. A second portion 8B of the dialysis fluid supply line 8 leading to the dialysis fluid chamber 3 extends from the second filter chamber 12B of the first sterilizing filter 12.

[0026] To obtain replacement fluid from the dialysis fluid, a blood (dialysis) filtration device can comprise a second sterilizing filter 14, which is divided by a semipermeable membrane 15 into a first filter chamber 16 and a second filter chamber 17. The first filter chamber 16 of the second sterilizing filter 14 is connected to the second portion 8B of the dialysis fluid supply line 8. The replacement fluid line is not shown in FIG. 1.

[0027] The dialysis fluid discharge line 10 is divided into two portions 10A and 10B leading to the drain 11. A dialysis fluid pump 18 is connected to the first portion 10A, and an ultrafiltrate pump 19 is connected to the second portion 10B. Further, the other chamber 13B of the balancing device 13 is connected to the second portion 10B.

[0028] During blood treatment, new dialysis fluid flows from the dialysis fluid source 9 into the dialysis fluid chamber 3, and the used dialysis fluid exits the dialysis fluid chamber 3 and flows into the drain 11. The dialysis fluid supply line represents a first flow path 8 through which new dialysis fluid flows from the dialysis fluid source 9 into the dialysis fluid chamber 3, and the dialysis fluid discharge line represents a second flow path 10 through which the used dialysis fluid flows from the dialysis fluid chamber 3 into the drain 11. These flow paths form all parts of the associated lines, including the components connected to the lines.

[0029] A bypass line 20 leading to the dialysis fluid discharge line 10 branches off from a second part 8B of the dialysis fluid supply line 8 downstream of the second filter chamber 12B of the first sterilizing filter 12. A first valve device 21 having an electromagnetically operable shut-off member 21A is connected to the second bypass line 20. The bypass line represents a flow path 20 provided for a special operating mode. This operating mode can be, for example, a malfunction, such as the detection of an incorrect composition of the dialysis fluid, which can be detected by measuring the conductivity. If this malfunction occurs, the shut-off member 21A of the first valve device 21 is opened so that the dialysis fluid can be guided to the drain 11 while bypassing the dialyzer 1. To isolate the dialyzer 1, a shut-off member 22 is provided upstream of the dialysis fluid chamber 3 and a shut-off member 23 is provided downstream.

[0030] Hereinafter, the line part of the bypass line 20 connected to the dialysis fluid supply line 8 is referred to as the upstream part 20A of the flow path 20 for the special operating mode, and the line part of the bypass line 20 connected to the dialysis fluid discharge line 10 is referred to as the downstream part.

[0031] The second filter chamber of the second sterilizing filter 14 is connected to the dialysis fluid discharge line 10 via a connection line 24. A second valve device 25 having an electromagnetically actuable shut-off member 25A is connected to the connection line 24. A connection 26 (port) to which the venous blood line 7A can be connected for flushing the venous blood line 7A (FIG. 2) is located upstream of this shut-off member 25A. A shut-off member 27 that is closed for the flushing process is provided upstream of the connection 26. Flushing of the venous blood line 7A is another example of a special operating mode that will be described in detail with reference to FIG. 2.

[0032] Additional lines, shut-off members, or connections (ports), for example, the line indicated by reference numeral 28, shut-off members 29, 30, or connection 35 (port), etc. can also be provided, but are not important for the understanding of the present invention.

[0033] The blood treatment device has a control unit 31 configured to be able to open and close the shut-off members 21A and 25A of the first valve device 21 and the second valve device 25, respectively. Control lines for the electromagnetically actuable shut-off members 21A and 25A of the first valve device 21 and the second valve device 25 are indicated by reference numerals 21' and 25' in FIGS. 1 and 2, respectively. The control unit 31 can also operate other shut-off members.

[0034] The blood treatment device has a check device 32 including an evaluation unit 32A that receives measurement signals from a first pressure gauge 33 and a second pressure gauge 34.

[0035] In the embodiment shown in FIG. 1, the first pressure gauge 33 is arranged in the downstream portion 8B of the dialysis fluid supply line 8 to measure the pressure P1 in this line portion, while the second pressure gauge 34 is arranged in the dialysis fluid discharge line 10 upstream of the dialysis fluid pump 18 and the ultrafiltrate pump 19 to measure the pressure P2 in this line portion. The two pressure gauges 33, 34 are connected to the check device 32 via signal lines 33', 34'.

[0036] The first shut-off member 21A and the second shut-off member 25A are closed during blood treatment. When a special operation mode is specified, the control unit 31 receives a control signal for opening the first shut-off member 21A or the second shut-off member 25A. In the present embodiment, it is assumed that the control unit 31 receives a control signal for opening the first or second shut-off member from a central control and arithmetic unit (not shown) of the blood treatment device, and this unit controls the preparation of the blood treatment device for blood treatment and the blood treatment itself.

[0037] The evaluation unit 32A calculates the difference between the pressure P1 measured by the first pressure gauge 33 and the pressure P2 measured by the second pressure gauge 34, and generates an enable signal received by the control unit 31 when the difference is greater than 0, that is, when P1 > P2. The control unit 31 opens the first shut-off member 21A or the second shut-off member 25A only when it receives both the corresponding control signal for the first or second shut-off member from the central control and arithmetic unit and the enable signal from the evaluation unit 32A.

[0038] When the control unit 31 receives the corresponding control signal for the "bypass" operation mode, a flow connection is established between the upstream portion 20A and the downstream portion 20B of the flow path 20 for this special operation mode only when the pressure is P1 > P2. As a result, new dialysis fluid is ensured to flow from the first flow path 8 into the second flow path 10 and thus into the drain 11. When the pressure is P1 < P2, the enable signal is not generated, so there is no risk that the used dialysis fluid from the second flow path 10 will enter the first flow path 8 for the new dialysis fluid. In FIG. 1, the flow direction of the dialysis fluid when the blocking member 21A of the first valve device 21 is open is indicated by an arrow. Other operating states can also be considered for the bypass operation. For example, non-physiological dialysis fluid cannot enter the dialyzer 1. When P1 < P2, suitable measures can be taken to increase the pressure P1 in the first flow path 8. These measures may involve closing the blocking member 22 in the first flow path 8 upstream of the dialysis fluid chamber 3 of the dialyzer 1. When the blocking member 22 is closed so that P1 > P2, the blocking member 21A can be opened. Instead of the blocking member 21A, the blocking member 29 can also be opened.

[0039] FIG. 2 shows the extracorporeal blood treatment device of FIG. 1 in a state where the venous tube line 7A is connected to the connection portion 26 to prepare for blood treatment, so that the flushing fluid can flow through the venous blood line 7A to the drain 11 when the blocking member 25A of the second valve device 25 is open. To flush the venous blood line 7A, the blocking member 27 upstream of the blocking member 25A of the second valve device 25 is closed. In this embodiment, the first pressure gauge is the pressure gauge 33(2) arranged in the venous blood line 7A and measuring the pressure P1 in this line upstream of the blocking member 25A of the second valve device 25. The second pressure gauge is the pressure gauge 34 arranged in the dialysis fluid discharge line 10 and measuring the pressure P2 in this line, similar to the first embodiment of FIG. 1.

[0040] When the venous blood line 7A is connected to the connection part 26 and the control unit 31 receives a corresponding control signal for the special operation mode "flushing of the blood line", the shut-off member 25A of the second valve device 25 is opened only when the pressure is P1 > P2. As a result, it is ensured that the flushing fluid flows only towards the second flow path 10. In FIG. 2, the flow direction of the flushing fluid when the shut-off member 25A of the second valve device 25 is open is indicated by an arrow.

[0041] Only one of the two embodiments may be implemented in the blood treatment device. However, it is also possible to implement both embodiments. The flow direction can also be monitored in other "critical flow paths" by the check device according to the present invention. In this sense, it should be understood that the two operation modes described are only one embodiment of the "critical flow path". The invention described in the claims of the present application at the time of original filing is appended below. [1] An extracorporeal blood treatment device designed to be connected to a blood treatment unit divided by a semipermeable membrane into a first compartment that is part of a fluid system and a second compartment that is part of an extracorporeal blood circuit, wherein the fluid system has at least one fluid line and includes a first flow path designed as a flow path for supplying fresh treatment fluid from a fluid source to the first compartment of the blood treatment unit, and has at least one fluid line and includes a second flow path designed as a flow path for discharging used treatment fluid from the first compartment of the blood treatment unit to a drain, at least one additional flow path having at least one fluid line is provided for a special operation mode, the flow path having an upstream portion upstream of a valve device having at least one shut-off member and a downstream portion downstream of the valve device and in fluid connection with the second flow path, the valve device being designed such that a fluid connection is established between the upstream portion and the downstream portion of the flow path for the special operation mode in a first operating position of the valve device and the fluid connection is interrupted in a second operating position of the valve device, a control unit is provided for operating the valve device such that the valve device takes the first operating position for the special operation mode and the second operating position for another operation mode, a pressure-based check device interacting with the control unit is provided, the pressure-based check device being designed such that a fluid connection can be established between the upstream portion and the downstream portion of the flow path for the special operation mode only when the pressure-based check device detects an operating state in which the fluid in the flow path for the special operation mode reliably flows towards the second flow path. An extracorporeal blood treatment device characterized by this. [2] The pressure-based check device includes an upstream pressure gauge for measuring the upstream pressure in the upstream portion of the flow path for the special operation mode, a downstream pressure gauge for measuring the downstream pressure in the downstream portion of the flow path for the special operation mode, and an evaluation unit configured to receive measurement signals from the upstream pressure gauge and the downstream pressure gauge and compare the upstream pressure with the downstream pressure. When the upstream pressure is higher than the downstream pressure, the evaluation unit indicates an operating state in which it is ensured that the fluid flows towards the second flow path. The extracorporeal blood treatment device according to [1]. [3] The pressure-based check device is configured such that the pressure-based check device generates an enable signal for the control unit. The control unit is configured to operate the valve device to take the first operating position only when the control unit receives a control signal for switching to the special operation mode and the enable signal from the pressure-based check device. The extracorporeal blood treatment device according to [1] or [2]. [4] The first flow path includes a first filter divided by a semipermeable membrane into a first filter chamber and a second filter chamber, an upstream portion of the first flow path connecting the fluid supply source to the first filter chamber of the filter, and a downstream portion of the first flow path connecting the second filter chamber of the filter to the inlet of the first section of the blood treatment unit. The upstream portion of the flow path for the special operation mode is a line portion fluidly connected to the downstream portion of the first flow path. The extracorporeal blood treatment device according to any one of [1] to [3]. [5] The first pressure gauge is disposed in the downstream portion of the first flow path, and the second pressure gauge is disposed in the second flow path. The extracorporeal blood treatment device according to [4]. [6] The extracorporeal blood circuit includes an arterial blood line and a venous blood line. The upstream portion of the flow path for the special operation mode is a line portion of the venous blood line or a line portion fluidly connected to the venous blood line. The extracorporeal blood treatment device according to any one of [1] to [5]. [7] The extracorporeal blood treatment device according to [6], wherein the first pressure gauge is arranged in the venous blood line, and the second pressure gauge is arranged in the second flow path. [8] The extracorporeal blood treatment device according to any one of [1] to [7], wherein the exchange unit is a dialyzer divided by a semipermeable membrane into a dialysate chamber and a blood chamber. [9] A method for operating an extracorporeal blood treatment device, comprising a blood treatment unit divided by a semipermeable membrane into a first compartment that is part of a fluid system and a second compartment that is part of an extracorporeal blood circuit, wherein the fluid system has at least one fluid line and includes a first flow path designed as a flow path for supplying fresh treatment fluid from a fluid source to the first compartment of the blood treatment unit, and has at least one fluid line and includes a second flow path designed as a flow path for discharging used treatment fluid from the first compartment of the blood treatment unit to a drain, wherein upstream pressure in the upstream portion of the flow path for a special operating state and downstream pressure in the downstream portion of the flow path for the special operating state that is flow-connected to the second flow path are measured before a flow connection is established between the upstream portion of the additional flow path for the special operating state and the downstream portion of the flow path for the special operating state, and the flow connection is established only when the upstream pressure is higher than the downstream pressure.

[10] The first flow path includes a first filter divided by a semipermeable membrane into a first filter chamber and a second filter chamber, an upstream portion of the first flow path connecting the fluid source to the first filter chamber of the filter, and a downstream portion of the first flow path connecting the second filter chamber of the filter to an inlet of the first compartment of the blood treatment unit, wherein fluid flow through the flow path for a special operating mode from the downstream portion of the first flow path to the second flow path is established only when the upstream pressure in the upstream portion is higher than the downstream pressure in the downstream portion of the flow path for the special operating mode The method according to [9], characterized by this.

[11] The method according to

[10] , wherein the upstream pressure is measured by a pressure gauge arranged in the downstream portion of the first flow path, and the downstream pressure is measured by a pressure gauge arranged in the second flow path.

[12] The extracorporeal blood circuit includes an arterial blood line and a venous blood line, and the fluid flow through the flow path for the special operating state from the venous blood line to the second flow path is established only when the upstream pressure in the upstream portion is higher than the downstream pressure in the downstream portion of the flow path for the special operating state. The method according to any one of [9] to

[11] .

[13] The upstream pressure is measured by a pressure gauge disposed in the venous blood line, and the downstream pressure is measured by a pressure gauge disposed in the second flow path. The method according to

[12] .

[14] The exchange unit is a dialyzer divided into a dialysate chamber and a blood chamber by a semipermeable membrane. The method according to any one of [9] to

[13] .

[15] The fluid flowing through the flow path for the special operating state is a dialysate or a flushing fluid. The method according to any one of [9] to

[14] .

Claims

1. An extracorporeal blood treatment device designed to be connected to a blood treatment unit divided by a semipermeable membrane into a first compartment that is part of a fluid system and a second compartment that is part of an extracorporeal blood circuit, wherein the fluid system has at least one fluid line and comprises a first flow path designed as a flow path for supplying fresh treatment fluid from a fluid source to the first compartment of the blood treatment unit, and has at least one fluid line and comprises a second flow path designed as a flow path for discharging used treatment fluid from the first compartment of the blood treatment unit to a drain, at least one additional flow path having at least one fluid line is provided for a special operating mode, the at least one additional flow path being upstream of a valve device having at least one shut-off member, having an upstream portion fluidly connected to the first flow path and a downstream portion downstream of the valve device and fluidly connected to the second flow path, the valve device being designed such that a fluid connection is established between the upstream portion and the downstream portion of the at least one additional flow path for the special operating mode in a first operating position of the valve device and the fluid connection is interrupted in a second operating position of the valve device, a control unit is provided for operating the valve device such that the valve device takes the first operating position for the special operating mode and the second operating position for another operating mode, a pressure-based check device interacting with the control unit is provided, the pressure-based check device being designed such that a fluid connection can be established between the upstream portion and the downstream portion of the at least one additional flow path for the special operating mode only when the pressure-based check device detects an operating state in which the fluid in the at least one additional flow path for the special operating mode flows from the first flow path towards the second flow path leading to the drain and does not enter the first flow path. An extracorporeal blood treatment device characterized by this.

2. The pressure-based check device includes an upstream pressure gauge for measuring an upstream pressure in the upstream portion of the at least one additional flow path for the special operation mode, a downstream pressure gauge for measuring a downstream pressure in the downstream portion of the at least one additional flow path for the special operation mode, and an evaluation unit configured to receive measurement signals from the upstream pressure gauge and the downstream pressure gauge and compare the upstream pressure with the downstream pressure. When the upstream pressure is higher than the downstream pressure, the evaluation unit indicates an operating state in which it is ensured that the fluid flows towards the second flow path. The extracorporeal blood treatment device according to claim 1.

3. The pressure-based check device is configured to generate an enable signal for the control unit, and the control unit is configured to operate the valve device to take the first operating position only when the control unit receives a control signal for switching to the special operation mode and the enable signal from the pressure-based check device. The extracorporeal blood treatment device according to claim 1 or 2.

4. The first flow path includes a first filter divided by a semipermeable membrane into a first filter chamber and a second filter chamber, an upstream portion of the first flow path connecting the fluid supply source to the first filter chamber of the filter, and a downstream portion of the first flow path connecting the second filter chamber of the filter to an inlet of the first section of the blood treatment unit. The upstream portion of the at least one additional flow path for the special operation mode is a line portion fluidly connected to the downstream portion of the first flow path. The extracorporeal blood treatment device according to any one of claims 1 to 3.

5. The extracorporeal blood treatment device according to claim 4, which directly or indirectly quotes claim 2, wherein the upstream pressure gauge is arranged in the downstream portion of the first flow path and the downstream pressure gauge is arranged in the second flow path.

6. The extracorporeal blood circuit includes an arterial blood line and a venous blood line, and an upstream portion of the at least one additional flow path for the special operation mode is a line portion of the venous blood line or a line portion fluidly connected to the venous blood line. The extracorporeal blood treatment device according to any one of claims 1 to 5, characterized in that.

7. The extracorporeal blood treatment device according to claim 6, which directly or indirectly quotes claim 2, characterized in that the upstream pressure gauge is arranged in the venous blood line and the downstream pressure gauge is arranged in the second flow path.

8. The extracorporeal blood treatment device according to any one of claims 1 to 7, characterized in that the blood treatment unit is a dialyzer divided into a dialysate chamber and a blood chamber by a semipermeable membrane.

9. A method for operating an extracorporeal blood treatment device, Comprising a blood treatment unit divided by a semipermeable membrane into a first compartment that is part of a fluid system and a second compartment that is part of an extracorporeal blood circuit, The fluid system has at least one fluid line and includes a first flow path designed as a flow path for supplying fresh treatment fluid from a fluid source to the first compartment of the blood treatment unit, and has at least one fluid line and is designed as a flow path for discharging used treatment fluid from the first compartment of the blood treatment unit to a drain. A second flow path, Before a flow connection is established between an upstream portion of an additional flow path for a special operating state and a downstream portion of the additional flow path for the special operating state that is flow-connected to the second flow path, an upstream pressure in the upstream portion of the additional flow path for the special operating state and a downstream pressure in the downstream portion are measured, and the flow connection is established only when the upstream pressure is higher than the downstream pressure. A method, characterized in that.

10. The first flow path includes a first filter divided by a semipermeable membrane into a first filter chamber and a second filter chamber, an upstream portion of the first flow path connecting the fluid source to the first filter chamber of the filter, and a downstream portion of the first flow path connecting the second filter chamber of the filter to an inlet of the first compartment of the blood treatment unit. The fluid flow through the additional flow path for the special operating mode from the downstream portion of the first flow path to the second flow path is established only when the upstream pressure in the upstream portion is higher than the downstream pressure in the downstream portion of the additional flow path for the special operating mode. The method according to claim 9, characterized in that.

11. The method according to claim 10, characterized in that the upstream pressure is measured by a pressure gauge arranged in the downstream portion of the first flow path, and the downstream pressure is measured by a pressure gauge arranged in the second flow path.

12. The extracorporeal blood circuit comprises an arterial blood line and a venous blood line. The fluid flow through the additional flow path for the special operating state from the venous blood line to the second flow path is established only when the upstream pressure in the upstream portion is higher than the downstream pressure in the downstream portion of the additional flow path for the special operating state. The method according to any one of claims 9 to 11.

13. The method according to claim 12, characterized in that the upstream pressure is measured by a pressure gauge arranged in the venous blood line, and the downstream pressure is measured by a pressure gauge arranged in the second flow path.

14. The method according to any one of claims 9 to 13, characterized in that the blood treatment unit is a dialyzer divided into a dialysate chamber and a blood chamber by a semipermeable membrane.

15. The method according to any one of claims 9 to 14, characterized in that the fluid flowing through the additional flow path for the special operating state is a dialysate or a flushing fluid.

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