BLOOD TREATMENT DEVICE WITH AUTOMATIC SUBSTITUTION VOLUME COMPENSATION

Description

[0001] The present disclosure relates to a blood treatment device, in particular a dialysis machine, for use in (continuous) blood treatment / dialysis therapies, in particular renal replacement therapies, comprising: an extracorporeal blood circuit, a dialyzer and a dialyzer fluid circuit, wherein the extracorporeal blood circuit and the dialyzer fluid circuit are separated from each other by a membrane provided in the dialyzer, through which blood (using a dialyzer fluid solution) can be filtered; and at least one substitution solution pump, which is configured to supply a substitution solution to the extracorporeal blood circuit before and / or after the dialyzer. State of the art

[0002] Blood treatment devices are already known from the prior art. For example, EP 0 321 754 A1 discloses a blood treatment device with a filter divided into two chambers by a membrane. An extracorporeal blood circuit is placed through one chamber of the filter. The other chamber of the filter is connected to an ultrafiltration unit, which is configured to extract ultrafiltrate from the other chamber by means of an ultrafiltrate pump. The blood treatment device includes a substitution unit, which is configured to supply a substitution fluid to the blood circuit by means of a substitution pump. Furthermore, the blood treatment device includes a balance that balances the extracted amount of ultrafiltrate and the supplied amount of substitution fluid by weighing the ultrafiltrate container and the substitution fluid container with their respective contents.In addition, the blood treatment device includes a control unit for controlling the ultrafiltrate pump and the substitution pump.

[0003] Another document, EP 0 829 265 B1, also discloses a blood treatment device which has an interface for a disposable tubing set, a variety of pumps such as a blood pump, a syringe pump, an ultrafiltrate pump and a substitution pump, load cells for measuring the weight of bags containing fluids required for blood treatment, a user interface comprising a touchscreen display and a control unit for controlling the processes of the blood treatment device.

[0004] EP 3 015 123 A1 discloses a blood treatment device for use in blood treatment therapies, comprising an extracorporeal blood circuit, a dialyzer, and a dialyzer fluid circuit, wherein the extracorporeal blood circuit and the dialyzer fluid circuit are separated from each other by a membrane provided in the dialyzer, through which blood can be filtered. The blood treatment device includes at least one substitution solution pump, which is configured to supply a substitution solution to the extracorporeal blood circuit before and / or after the dialyzer. According to the disclosure in EP 3 015 123 A1, a deviation between a predetermined target volume and an actual volume of a supplied substitution solution is calculated.The deviation in the substitution volume is processed into a substitution correction value or amount, which can then be output as a percentage of the set substitution flow or in another suitable form. A regulated substitution flow is corrected by the previously determined percentage. EP 3 015 123 A1 provides a complex control system ("feedback control") for compensating for deviations in the substitution volume.

[0005] US 2002 / 150476 A1 discloses a control system with different modes for a fluid pump for a blood treatment device. In a Back Off Response Mode, a parameter, such as the pump's flow rate, can be controlled by gradually reducing the pump speed by a fixed percentage until the flow rate is no longer above a setpoint.

[0006] Further state of the art can be found in EP 0 373 455 A1, CA 2 580 848 A1, US 5,470,483 A, WO 94 / 11093 A1, DE 33 13 421 A1, WO 92 / 00768 A1, WO 2018 / 017623 A1, and US 9,089,639 B2.

[0007] During dialysis treatment, events can occur that prevent the desired, ideal / optimal substitution fluid volume / substitution solution volume, as set by the user, from being achieved. This can happen, for example, when starting / restarting the substitution solution pump / pump flow rate at the beginning of therapy. Furthermore, errors can occur in the delivery of the substitution solution, such as when a bag containing the substitution solution is not correctly connected to the tubing that delivers the solution to the extracorporeal circulation.

[0008] The state of the art has the fundamental disadvantage that deviations (i.e., differences / residues) between a (predetermined) ideal / optimal target volume set by a user and an actual / truly controlled volume of the supplied substitution solution cannot be easily and automatically compensated. Brief description of the Revelation

[0009] The purpose of this disclosure is therefore to avoid or at least mitigate the disadvantages of the prior art. In particular, the blood treatment device is to be designed in such a way that it gradually compensates for deviations / differences between an ideal / optimal target volume and an actually controlled volume of the supplied substitution solution or residues of the actually controlled volume with respect to the ideal target volume over the course of a therapy, so that ultimately the ideal (desired) target volume is (re)achieved.

[0010] This task is solved in a blood treatment device of this type by having a control unit which is configured to calculate a difference between a (predetermined) ideal / optimal target volume set by a user and an actual / truly controlled volume of the supplied substitution solution, and to temporarily increase a controlled (throughput) rate / delivery rate / flow rate / controlled volume flow of the substitution solution pump by a predetermined fixed percentage, which is less than or equal to 5%, (compared to a preset / original or normal / desired / actually required flow rate of the substitution solution pump), by appropriately controlling the pump, until the deviation between the actually controlled volume and the ideal target volume no longer exists, i.e., the actually controlled volume corresponds to the ideal target volume.

[0011] In other words, the control unit of this disclosure calculates a deviation between volumes, specifically between a target volume of the substitution solution to be delivered to the extracorporeal circulation and the actual delivered volume. In particular, it calculates a shortfall in the actual volume compared to the target volume. If a shortfall exists, the flow rate of the substitution pump is temporarily increased for a specific period. The core of the disclosure is that the percentage increase in the flow rate of the substitution pump is limited to a maximum of 5%. Accordingly, the control unit sets a new, increased flow rate.As soon as there is no difference between the actual controlled volume and the target volume / no residue remains, the original / normal / preset / actually required / desired flow rate of the substitution solution pump is restored. Deviations between the ideal target volume and the actual controlled volume of the supplied substitution solution can thus be automatically compensated in a simple manner, as revealed.

[0012] In other words, the control unit according to the present disclosure is configured to compensate for the difference between the ideal target volume and the actually controlled volume by temporarily increasing the controlled flow rate of the at least one substitution solution pump by the predetermined, fixed percentage.

[0013] Advantageous embodiments are claimed in the dependent claims and are explained below.

[0014] It is advantageous if the predetermined, fixed percentage by which the volumetric flow rate of the substitution solution is increased is at least 1% and at most 5%. If the percentage is between 1% and 5%, the deviation or residue is eliminated promptly, but not too quickly, so that the control unit can react in time when the actual controlled volume corresponds to the ideal target volume and reset the flow rate of the substitution solution pump back to the (desired) initial value. This preferably prevents the actual controlled volume from exceeding the target volume during an increase in the flow rate.Furthermore, it has been shown that if the percentage is greater than 1%, the actual volume flow / flow rate is normally large enough to compensate for the events mentioned above that contribute to the target substitution fluid volume / substitution solution volume not being reached.

[0015] Preferably, the predetermined fixed percentage is set by the control unit depending on the missing volume, such that the predetermined fixed percentage is set higher when the deviation between the actual controlled volume and the ideal target volume is large than when the deviation between the actual controlled volume and the ideal target volume is small. For example, the predetermined fixed percentage is set to 1% when the deviation between the actual controlled volume and the ideal target volume is small, and to 5% when the deviation between the actual controlled volume and the ideal target volume is large. However, any percentage increase between 1% and 5% is also conceivable.

[0016] Furthermore, it is advantageous to consider therapy stoppage times triggered by an alarm when calculating the deviation between the actual volume and the target volume. When an alarm is triggered, therapy is always stopped. Consequently, no replacement solution is administered to the extracorporeal circulation. Therefore, no fluid volume needs to be compensated for during the alarm / therapy stoppage, and the control unit does not include any administered / delivered quantity in its calculations during this time.

[0017] It is advantageous if the control unit is set up to issue an alarm if it detects that even with a 5% increase in the flow rate of the substitution solution pump, the deviation between the actual volume and the target volume cannot be compensated.

[0018] Advantageously, the control unit is set up to increase the flow rate of the substitution solution pump only if other restrictions / conditions do not prohibit this.

[0019] Preferably, the control unit is configured to calculate the difference or residue between the ideal target volume and the actually controlled volume using the profile of the (controlled unit's) flow rate of the at least one substitution solution pump.

[0020] It is advantageous, if the control unit is set up, to adjust the flow rate or volume flow of at least one substitution solution pump.

[0021] Preferably, when the at least one substitution solution pump is (re)started, the flow rate / volume flow rate increases slowly / continuously / linearly, so that a desired flow rate / volume flow rate is only reached after a predetermined short period of time.

[0022] In particular, the volume flow rate increases linearly from zero to the desired flow rate (volume flow) when starting / restarting.

[0023] Preferably, the control unit is configured to temporarily increase the flow rate by a predetermined fixed percentage after reaching the desired flow rate / volume flow rate, in order to slowly / continuously reduce the difference / residue between the actually controlled volume and the ideal target volume, which results from the slow / continuous increase of the flow rate during start / restart, until the difference or residue between the actually controlled volume and the ideal target volume no longer exists, i.e., the actually controlled volume corresponds to the ideal target volume.

[0024] Advantageously, the control unit is further configured to reduce or compensate for the resulting residue or difference between the ideal target volume and the actual controlled volume (subsequently) if the controlled flow rate of the substitution solution pump needs to be temporarily reduced (for example, due to a temporary blockage of the dialyzer) by temporarily increasing the controlled flow rate of the substitution solution pump by a predetermined fixed percentage, while appropriately controlling the pump, until the difference or residue between the actual controlled volume and the ideal target volume no longer exists, i.e., the actual controlled volume corresponds to the ideal target volume.

[0025] The control unit can also be configured to temporarily reduce the controlled flow rate of the substitution solution pump by a predetermined fixed percentage in the event that the actual controlled volume of the supplied substitution solution is larger than the ideal target volume set by the user, until there is no longer any deviation between the actual controlled volume and the ideal target volume, i.e., the actual controlled volume corresponds to the ideal target volume.

[0026] Preferably, the blood treatment device includes a weighing device, in particular a load cell, for measuring the weight of a bag, in particular a disposable bag, containing the substitution solution.

[0027] It is advantageous if the extracorporeal blood circulation and the dialysis fluid circuit are designed as disposable tubes, which are connected to an interface provided on the dialysis machine.

[0028] Preferably, the multitude of pumps includes, in addition to the substitution solution pump, at least one blood pump, one syringe pump and one ultrafiltrate pump.

[0029] The blood treatment device preferably also includes a barcode reader which is configured to read barcodes applied to disposable items such as disposable tubing or their outer packaging.

[0030] Furthermore, the blood treatment device preferably includes a user interface comprising a display with a touch screen.

[0031] The blood treatment device is preferably configured for wired communication.

[0032] The control unit of the blood treatment device is preferably designed as at least one processor, preferably several processors.

[0033] In other words, the disclosure relates to a dialysis machine. The dialysis machine contains a barcode reader. Furthermore, the dialysis machine contains a user interface or a touchscreen display. The dialysis machine also has an interface for a disposable tubing set, which includes a blood side and a dialysis fluid side, separated from each other by a (semi-)permeable membrane to filter blood (using a dialysis fluid solution). A replacement solution is supplied to the blood side before / after a dialyzer. The dialysis machine includes a blood pump, a syringe pump, an ultrafiltrate pump, a replacement solution pump, etc. The dialysis machine is equipped for wired communication / has wired communication devices.The dialysis machine features software specifically designed for use in continuous dialysis therapies, such as renal replacement therapy. This software runs on multiple processors within the dialysis machine. Furthermore, the dialysis machine incorporates an integrated power management system. It also includes weighing devices, particularly load cells, which measure the weight of disposable bags containing the fluids required for dialysis therapy (e.g., dialysis solution, replacement solution).

[0034] The system, or rather the dialysis machine, is designed to compensate for any discrepancies between the actual and target volumes of the replacement fluid during therapy, ensuring that the target volume is ultimately reached. If the system detects a discrepancy between the target and actual volumes, the replacement fluid flow rate is temporarily increased by 1% to 5% (depending on the volume deficit). This function is deactivated once the discrepancy is resolved. Brief description of the characters

[0035] The revelation is further explained below with the help of figures. They show: Fig. 1 a schematic view of a blood treatment device according to the present disclosure; Fig. 2 a flow diagram illustrating the automatic compensation of a volume of the substitution solution taking place in the control unit according to the disclosure; and Fig. 3 a diagram showing a time course of a substitution solution flow rate according to the present disclosure. Character description

[0036] The figures are purely schematic and serve solely to aid in understanding the present revelation. Identical elements are marked with the same reference symbols.

[0037] Fig. 1Figure 1 shows a schematic view of an extracorporeal blood treatment device (dialysis machine) 2. The blood treatment device 2 is fundamentally designed for use in both continuous and intermittent blood treatment therapies, particularly renal replacement therapies. The blood treatment device 2 is specifically designed as an acute dialysis machine and is thus essentially intended for use in intensive care units with predominantly unstable patients. The blood treatment device 2 of this disclosure can, in principle, perform a variety of different blood treatment therapies (e.g., slow continuous ultrafiltration (SCUF), continuous venous-venous hemofiltration (CVVH), continuous venous-venous hemodialysis (CVVHD), continuous venous-venous hemodiafiltration (CVVHDF), therapeutic plasma exchange (TPE), etc.), dilution modes (e.g.,Predilution, postdilution, pre- and postdilution), as well as types of anticoagulation (e.g. none, heparin, citrate, etc.) are performed.

[0038] The blood treatment device 2 basically comprises an extracorporeal circuit 4, a dialyzer (hemofilter) 6, and a dialysate circuit 8. The extracorporeal circuit 4 and the dialysate circuit 8 are separated from each other by a membrane 10 provided in the dialyzer 6, through which blood can be filtered using a dialysate solution or without using a dialysate solution.

[0039] The extracorporeal circuit 4 comprises an arterial section 12 and a venous section 14. It is generally intended that the arterial section 12, in particular one end thereof, should be connected to an artery of a patient, especially an intensive care patient. Furthermore, it is intended that the venous section 14, in particular one end thereof, should be connected to a vein of a patient, especially an intensive care patient.

[0040] The arterial section 12, extending from an arterial end 16 in the direction of blood flow towards the dialyzer 6, comprises an arterial pressure sensor 18, an (arterial) blood pump 20, and a dialyzer inlet pressure sensor 22. The venous section 14, extending from the dialyzer 6 in the direction of blood flow towards a venous end 24, comprises a venous expansion chamber or air trap 26, a safety air detector 28, and a safety valve 30. Venous pressure can be measured at / downstream of the venous expansion chamber 26 via a venous pressure sensor 32.

[0041] As from Fig. 1As can be seen, the venous expansion chamber 26 is connected to a substitution solution bag / container 34. A substitution solution pump 36 is provided and configured to pump a substitution solution from the substitution solution bag 34 into the extracorporeal blood circulation 4, in particular into the venous section 14 thereof (into the venous expansion chamber 26).

[0042] The dialysis fluid circuit 8 has at least one outlet 38 for ultrafiltrate / spent dialysis fluid (dialysate) / other liquid. In principle, the ultrafiltrate / dialysate / other liquid can flow via the outlet 38 from the dialyzer 6 to a collection bag / container 40 for ultrafiltrate / dialysate / etc. An ultrafiltrate pressure sensor 42, a blood leak detector 44, and an ultrafiltrate pump 46 are arranged or provided in the outlet 38, flowing from the dialyzer 6 towards the collection bag 40.

[0043] As from Fig. 1 As further shown, in addition to the substitution solution bag 34 and the collection bag 40, another bag / container 48 is provided. Depending on the desired blood treatment therapy, bag 48 can contain, for example, a substitution solution / fluid or a dialysis fluid.

[0044] For example, if hemodialysis / hemofiltration treatment, etc., is to be performed using the extracorporeal blood treatment device 2—that is, a blood treatment therapy in which dialysis fluid flows through the dialyzer 6, thus transporting substances from the extracorporeal circuit 4 to the dialysis fluid circuit 8 via both diffusion and convection—the bag 48 contains dialysis fluid. If a first valve 50 is now opened and both a second valve 52 and a third valve 54 are closed, the dialysis fluid can be pumped to the dialyzer 6 via a pump 56.

[0045] Alternatively, if the extracorporeal blood treatment device 2 is to be used for hemofiltration, etc., i.e., a blood treatment therapy in which no dialysis fluid flows through the dialyzer 6 and thus substance transport from the extracorporeal circuit 4 to the dialysis fluid circuit 8 occurs solely via convection / filtration, the bag 48 can contain a substitution solution. If the first valve 50 and the second valve 52 are closed and the third valve 54 is opened, the substitution solution can be pumped from the bag 48 into the arterial section 12 of the extracorporeal circuit 4 (predilution). If the first valve 50 and the third valve 54 are closed and the second valve 52 is opened, the substitution solution can be pumped from the bag 48 into the venous section 14 of the extracorporeal circuit 4 (postdilution).When the first valve 50 is closed and the second valve 52 and the third valve 54 are opened, the substitution solution from the bag 48 can be pumped into both the arterial section 12 and the venous section 14 of the extracorporeal circuit (pre- and post-dilution). According to the present disclosure, pre- and post-dilution can also be achieved by pumping the substitution solution from the substitution solution bag 34 into the venous section 14 of the extracorporeal circuit 4 using the substitution solution pump 36 (post-dilution), and simultaneously pumping the substitution solution from the bag 48 into the arterial section 12 of the extracorporeal circuit 4 using the pump (substitution solution pump) 56 (pre-dilution).

[0046] As from Fig. 1As can be further seen, a liquid heater 58 and a pressure sensor 60 are provided between the pump 56 and the valve arrangement consisting of the first valve 50, the second valve 52 and the third valve 54.

[0047] Each of the three bags—the substitution solution bag 34, the collection bag 40, and the bag 48—is equipped with a load cell: a first load cell 62, a second load cell 64, and a third load cell 66. The first load cell 62 is configured to measure and monitor the weight of the substitution solution bag 34. The second load cell 64 is configured to measure and monitor the weight of the collection bag 40. The third load cell 66 is configured to measure and monitor the weight of the bag 48.

[0048] The extracorporeal blood treatment device 2 further comprises a control unit (CPU) 68, which receives information from the sensors provided in the blood treatment device 2 and which controls the actuators provided in the blood treatment device 2. According to the disclosure, this provides, in particular, a software-supported therapy. The control unit 68 receives information in particular from the arterial pressure sensor 18, the dialyzer inlet pressure sensor 22, the safety air detector 28, the venous pressure sensor 32, the ultrafiltrate pressure sensor 42, the blood leak detector 44, the pressure sensor 60, the first load cell 62, the second load cell 64, the third load cell 66, etc. The control unit 68 controls in particular the blood pump 20, the safety valve 30, the substitution solution pump 36, the ultrafiltrate pump 46, the first valve 50, the second valve 52, the third valve 54, the pump 56, the liquid heater 58, etc.Furthermore, the control unit 68 communicates with a user interface 70 designed as a touchscreen display. For example, the control unit 68 can be configured to display a warning or alarm on the user interface 70. Additionally, information entered by a user on the user interface 70 can be transmitted to the control unit 68.

[0049] As from Fig. 1As already evident, the present disclosure essentially relates to the control of the substitution solution pump 36 and the pump 56 (when the pump 56 operates as a substitution solution pump). The present disclosure as a whole essentially relates to a control system operated by the control unit 68. The control unit 68 can, in particular, calculate a difference or a residual volume between an ideal / optimal target volume of the supplied substitution solution, set by a user, and an actual controlled volume of the supplied substitution solution. For this purpose, the control unit 68 uses a time-dependent profile of the flow rate of the substitution solution pump 36 or the pump 56.

[0050] If the control unit 68 detects / becomes aware (through a corresponding calculation) that there is a difference or a shortfall between an ideal / optimal target volume set by a user and an actual / real controlled volume of the supplied substitution solution, the control unit 68 temporarily increases a controlled flow rate of the substitution solution pump 36 or the pump 56 by a predetermined fixed percentage. This means that the flow rate of the substitution solution pump 36 or the pump 56 is set higher than a normally required flow rate by a predetermined fixed percentage.A normally required flow rate is understood to be a flow rate by which the ideal / optimal target volume set by a user could be achieved if there were no residue / difference between the set target volume and the actually controlled volume of the supplied substitution solution.

[0051] The predetermined fixed percentage can generally be set to a value between 1% and 5%. It can also be configured that the predetermined fixed percentage is set higher when the deviation between the actual volume and the target volume is large than when the deviation is small. For example, the predetermined fixed percentage can be set to 1% when the deviation is small and to 5% when the deviation is large. In any case, however, the percentage set by the control unit (depending on the difference / residue) is already preset and predetermined.

[0052] As disclosed, the flow rate / volume flow of the substitution solution pump 36 or the pump 56 is increased by the predetermined fixed percentage until the difference or residue between the actually controlled volume and the ideal target volume no longer exists, i.e., the actually controlled volume (again) corresponds to the ideal target volume.

[0053] Fig. 2Figure 68 illustrates the revelatory process of automatic volume compensation of a substitution solution. The control unit 68 first calculates the actual controlled volume of the substitution solution supplied to an extracorporeal circuit 4. The control unit 68 then compares the actual controlled volume supplied to the extracorporeal circuit 4 with a (predetermined) ideal target volume. If the actual supplied volume is less than the ideal target volume, the control unit increases the flow rate of a substitution solution pump by a predetermined, fixed percentage, which is a maximum of 5%. The control unit 68 then continues to compare the target volume with the actual volume. Only when the target volume equals the actual volume does the control unit 68 reset the flow rate of the substitution solution pump to the initial / required value.The described routine only ends when the therapy is complete.

[0054] Fig. 3 Figure 1 shows a diagram depicting the time course of a substitution solution flow rate Q controlled by the control unit 68 and controlled by the substitution solution pump 36 or the pump 56. In particular, it shows Fig. 3, that when the substitution solution pump 36 or pump 56 is started or restarted, the substitution solution flow rate Q increases slowly / continuously / linearly (from zero), so that a desired, user-set ideal flow rate Qideal, which would result in the ideal / optimal target volume being supplied to the extracorporeal circuit 4 (if it were already set / present from the beginning), is only reached at time t1. According to the present disclosure, the controlled substitution solution flow rate Qcontrolled is not (yet) set to the user-set ideal flow rate Qideal from time t1, but initially continues to increase linearly until a controlled flow rate Qcontrolled is reached, which is higher than the ideal flow rate Qideal by a predetermined, fixed percentage. This is in Fig. 3This is the case at time t2. Now the controlled flow rate is temporarily held at a constant value until the volume not yet supplied at the start (see "-V" in Fig. 3 ), meaning the deficit or difference was completely compensated (see "+V in Fig. 3 This is in Fig. 3 This is the case at time t3. At time t3, the controlled flow rate Q is finally adjusted to the ideal flow rate Q. Reference symbol list

[0055] 2 Blood treatment device / dialysis machine 4 Extracorporeal circuit 6 Dialyzer 8 Dialysis fluid circuit 10 Membrane 12 Arterial section 14 Venous section 16 Arterial end 18 Arterial pressure sensor 20 (Arterial) blood pump 22 Dialyzer inlet pressure sensor 24 Venous end 26 Venous expansion chamber / Air trap 28 Safety air detector 30 Safety valve 32 Venous pressure sensor 34 Substitution solution bag 36 Substitution solution pump 38 Drain 40 Collection bag 42 Ultrafiltrate pressure sensor 44 Blood leak detector 46 Ultrafiltrate pump 48 Bag 50 First valve 52 Second valve 54 Third valve 56 Pump 58 Fluid warmer 60 Pressure sensor 62 First load cell 64 Second load cell 66 Third load cell 68 Control unit 70 User interface

Claims

1. Blood treatment device (2), in particular dialysis device, for use in blood treatment therapies, in particular renal replacement therapies, comprising: an extracorporeal blood circuit (4), a dialyzer (6) and a dialysis fluid circuit (8), wherein the extracorporeal blood circuit (4) and the dialysis fluid circuit (8) are separated from each other via a membrane (10) provided in the dialyzer (6), via which blood can be filtered; at least one substitution solution pump (36, 56), which is configured to supply a substitution solution to the extracorporeal blood circuit (4) before and / or after the dialyzer (6); characterized by a control unit (68) which is configured to calculate a backlog between an ideal target volume set by a user and an actually controlled volume of the supplied substitution solution, and to temporarily increase a controlled flow rate of the substitution solution pump (36, 56) under corresponding driving thereof by a predetermined, fixed percentage which is less than or equal to 5%, specifically until the backlog between the actually controlled volume and the ideal target volume no longer exists, i.e. the actually controlled volume corresponds to the ideal target volume.

2. Blood treatment device (2) according to claim 1, characterized in that the predetermined, fixed percentage by which the flow rate of the substitution solution is increased is at least 1% and at most 5%.

3. Blood treatment device (2) according to claim 1 or 2, characterized in that the predetermined, fixed percentage is set by the control unit (68) depending on the missing volume, so that the predetermined, fixed percentage is set higher when the deviation between the actual volume and the target volume is large, than when the deviation between the actual volume and the target volume is small.

4. Blood treatment device (2) according to one of the preceding claims, characterized in that the control unit (68) is configured to increase the flow rate of the substitution solution pump (36, 56) only if other restrictions do not prohibit this.

5. Blood treatment device (2) according to one of the preceding claims, characterized in that the control unit (68) is configured to calculate the backlog between the ideal target volume and the actually controlled volume using the course of the flow rate of the at least one substitution solution pump (36, 56).

6. Blood treatment device (2) according to one of the preceding claims, characterized in that the control unit (68) is configured to adjust the flow rate of the at least one substitution solution pump (36, 56).

7. Blood treatment device (2) according to claim 6, characterized in that when starting or restarting the at least one substitution solution pump (36, 56), the flow rate slowly increases so that a desired ideal flow rate is reached only after a predetermined, short time period.

8. Blood treatment device (2) according to claim 7, characterized in that after reaching the desired ideal flow rate, the flow rate is temporarily increased by the predetermined, fixed percentage in order to slowly reduce the backlog between the actually controlled volume and the ideal target volume, which results from the slow increase of the flow rate at start-up or restart, specifically until the backlog between the actually controlled volume and the ideal target volume no longer exists, i.e. the actually controlled volume corresponds to the ideal target volume.

9. Blood treatment device (2) according to one of the preceding claims, characterized in that the control unit (68) is configured so that, if the controlled flow rate of the substitution solution pump (36, 56) has to be temporarily reduced, the resulting backlog between the ideal target volume and the actually controlled volume is subsequently reduced or compensated for, by temporarily increasing the controlled flow rate of the substitution solution pump (36, 56) by the predetermined, fixed percentage under appropriate driving thereof, specifically until the backlog between the actually controlled volume and the ideal target volume no longer exists, i.e. the actually controlled volume corresponds to the ideal target volume.