METHOD FOR LEAKAGE TESTING OF A HEAT EXCHANGER OF A BLOOD TREATMENT DEVICE

Abstract

The invention relates to a method for leak testing a heat exchanger of a blood treatment device, comprising transporting a liquid such that the liquid flows through the heat exchanger into a liquid circuit of the blood treatment device and flows out of the liquid circuit through the heat exchanger; during the transport of the liquid, selectively changing a chemical property and / or a physical property of the liquid at at least a first predetermined section of the liquid circuit; monitoring the temporal evolution of the chemical property and / or the physical property at at least one further predetermined section of the liquid circuit by means of a sensor arranged at the respective further predetermined section; checking by means of a computing device whether the temporal evolution fulfills one or more predetermined criteria;and detecting a leak in the heat exchanger if the time course meets the predetermined criteria(s).

Description

TECHNICAL AREA

[0001] The invention relates to a method for leak testing of a heat exchanger of a blood treatment device and to a blood treatment device. BACKGROUND OF THE INVENTION

[0002] Blood treatment devices, such as dialysis systems, typically include a heat exchanger that uses the heat from the outgoing fluid, such as the dialysate, to preheat the incoming permeate, which is colder than the outgoing fluid. Leaks in the heat exchanger are not detected in current blood treatment devices. Instead, it is assumed that no undetected leaks occur.

[0003] Therefore, there is a risk that contamination, for example through the transfer of outgoing fluid, such as used dialysate, into incoming fluid, such as fresh permeate or onto the dialysis fluid side, will not be detected.

[0004] The invention is based on the objective of providing a method that addresses at least some of the problems outlined above, in particular enabling reliable detection of leaks in the heat exchanger. SUMMARY OF THE INVENTION

[0005] The invention provides a method, particularly a computer-implemented method, for leak testing a heat exchanger of a blood treatment device and a blood treatment device according to the independent claims. Specific embodiments are found in the dependent claims.

[0006] The invention relates to a method, particularly a computer-implemented method, for leak testing a heat exchanger of a blood treatment device, comprising transporting a liquid such that the liquid flows through the heat exchanger into a liquid circuit of the blood treatment device and flows out of the liquid circuit through the heat exchanger; during the transport of the liquid, selectively changing a chemical property and / or a physical property of the liquid at at least a first predetermined section of the liquid circuit; monitoring the temporal evolution of the chemical property and / or the physical property at at least one further predetermined section of the liquid circuit by means of a sensor arranged at the respective further predetermined section;Checking, using a computer system, whether the time course fulfills one or more predetermined criteria; determining, in particular using the computer system, a leak in the heat exchanger if the time course fulfills the predetermined criterion(s).

[0007] In other words, a method can be provided for systematically testing the tightness of a heat exchanger, specifically checking for leaks where outgoing fluid passes into the incoming fluid. A property of the fluid is deliberately altered. The temporal evolution of this property is monitored at a specific point. This point can be chosen such that a characteristic curve (relative or absolute) is observed when outgoing fluid passes into the incoming fluid.

[0008] The criteria(s) of the present procedure described above can be chosen in such a way as to establish this characteristic course.

[0009] The leak can be detected at various sections of the fluid circuit and using various measured parameters, which fall under claim 1 and are specified in more detail by way of example in the preferred embodiments.

[0010] For example, the process can include monitoring the properties of the liquid based on physical quantities such as conductivity, absorption, scattering, or the like. These physical properties change due to changes in the chemical properties, especially the composition, of the liquid.

[0011] The tightness requirement refers specifically to the seal between a first flow path in the heat exchanger, for example, the flow path for the incoming fluid, and a second flow path, for example, the flow path for the outgoing fluid. If the seal is compromised, i.e., if a leak exists, fluid can exchange between the first and second flow paths. In particular, outgoing fluid can enter the flow path for the incoming fluid. This scenario is extremely critical in blood treatment devices, as harmful substances can reach a patient. Furthermore, in dialysis, for example, the efficiency of the procedure is reduced.

[0012] The claimed leak test enables reliable detection of leaks, especially the type of leak described above.

[0013] As seen above, the fluid is transported in such a way that it flows through the heat exchanger into a fluid circuit of the blood treatment device and flows out of the fluid circuit through the heat exchanger.

[0014] The flow paths in the heat exchanger can be designed to allow heat exchange between the incoming and outgoing fluids. Under normal operating conditions, the incoming fluid may be colder than the outgoing fluid, so that heat is transferred from the outgoing fluid to the incoming fluid within the heat exchanger. However, a temperature difference or heat exchange is not necessarily required during the leak test.

[0015] The heat exchanger can be, for example, a tube heat exchanger, a plate heat exchanger, a spiral heat exchanger, a shell and tube heat exchanger, a jacketed tube heat exchanger, or hybrid forms thereof, the disclosure being not limited to these examples.

[0016] The liquid can be transported, for example, using one or more pumps, although other transport methods are also conceivable.

[0017] Examples and explanations of the first predetermined section and the second predetermined section can be found below.

[0018] A chemical property can include the composition of the liquid, in particular which substance(s) are contained in the liquid and / or in what dilution and / or quantity the substance(s) are present in the liquid. A chemical property can also be, for example, the pH value of the liquid. Physical properties can include, for example, optical properties such as absorption or scattering and / or conductivity. These physical properties change due to changes in the chemical properties, especially the composition of the liquid.

[0019] A targeted modification of the chemical and / or physical properties of a section can involve providing a sensor to measure the properties of the liquid within that section. This can be done, for example, without contact or with contact; in other words, the sensor does not necessarily have to be located in the liquid's flow path. Examples are given below.

[0020] Monitoring the temporal evolution of a property using a sensor can involve acquiring and optionally processing sensor readings at multiple points in time. This processing can include, for example, deriving the property from the measured values, preprocessing raw measurements, and / or determining a function that represents the temporal evolution of the property.

[0021] The sensor's placement in a section can imply that it measures a property within that section. Depending on the sensor type, this can involve non-contact measurement of the liquid, for example, optical measurement within the section. Optical measurement is appropriate, for instance, when monitoring an optical property of the liquid. Alternatively, the liquid in that section can come into contact with the sensor, allowing for the measurement of its properties. For example, a contact-based conductivity measurement can be performed within the liquid.

[0022] As seen above, the procedure includes checking whether the time course meets one or more predetermined criteria. The criteria may include the presence of an increase (possibly additional compared to a course without a leak), a decrease (possibly additional compared to a course without a leak), and / or a spike (possibly additional compared to a course without a leak), and / or a steeper or flatter curve compared to a course without a leak. Alternatively or additionally, the criteria may include the presence of an increase, decrease, and / or spike within a specific time period, for example, a period chosen relative to the time of the targeted change and / or relative to a point in time of a feature in the measured signal (a signal spike or the like).

[0023] As can be seen from the description of the examples below, these criteria can indicate a leak, in particular the passage of outgoing liquid into the incoming liquid.

[0024] According to the present disclosure, the method includes detecting a leak in the heat exchanger if the time course meets the predetermined criteria.

[0025] The detection can optionally trigger the issuance of a warning and / or the automatic initiation of security measures.

[0026] If leak detection occurs (only) when several criteria are met, these criteria can relate to the temporal evolution of a single property at a single section, for example, the presence of an additional reading and that the additional reading occurs within a specific time window. Alternatively or additionally, the criteria can relate to the same property measured by multiple sensors at different sections. Alternatively or additionally, the criteria can also relate to multiple properties, for example, an optical property and conductivity measured by different sensors. In other words, the procedure can include monitoring and verification at the same section and / or at one or more other predetermined sections.

[0027] Using multiple criteria can offer various advantages, depending on how they are implemented. For example, it can provide redundancy, such as requiring only one criterion to be met to detect a leak. The robustness of the leak test can be increased, for instance, by only detecting a leak if multiple criteria are met, particularly all criteria. Safety can be enhanced by only confirming a leak if none of the criteria are met. This can provide an additional function beyond simply detecting a leak.

[0028] The criteria are predefined and can be derived, for example, from predicted and / or empirically determined curves, particularly in comparison to the curves for a sealed heat exchanger. Examples are given below. These may be case-dependent criteria that the expert will adapt appropriately in each individual case, especially when quantitative criteria (e.g., relative times of the signal curve) are used, which depend on the system design.

[0029] The computing system can comprise one or more computing facilities, in particular a distributed computing system. The computing system can include local computers and / or servers and / or mobile user devices.

[0030] According to the present disclosure, the at least one first predetermined section may comprise an addition section. The targeted modification may involve changing the chemical and / or physical properties by adding a substance to the liquid, by changing the amount or dosage of a substance added to the liquid, and / or by diluting the liquid at the addition section. For example, water, aqueous concentrate, and / or powdered concentrate may be added, and / or the addition may be temporarily increased, reduced, or stopped.

[0031] According to the present disclosure, the at least one further predetermined section can comprise a first measuring section arranged downstream of the addition section in the direction of flow, and the sensor can comprise a first sensor arranged at the first measuring section and monitoring the chemical property. The chemical property can be monitored directly or indirectly by a measured quantity correlated with the chemical and / or physical property, for example, the electrical conductivity of the liquid.

[0032] The predetermined criterion may include the requirement that the time course of the signal from the first sensor exhibits two consecutive signal spikes.

[0033] In other words, the signal may show an initial spike over time. This spike can be caused, for example, directly by the addition of the substance, a change in the amount added, or by dosing or diluting the liquid. With a leak-free heat exchanger, no further spike should occur after this initial spike, assuming all other conditions remain constant. However, if outgoing fluid in the heat exchanger leaks into the incoming fluid, the modified composition of the fluid will cause another spike at the sensor when it reaches this point. Therefore, the mere presence of a second spike can indicate a leak. The criterion can thus be the presence of two consecutive spikes.In principle, if the dimensions and flow rate are known, a temporal criterion for the second signal deflection relative to the time of addition and / or the first signal deflection can also be applied, based on when the liquid modified by the transfer is expected to reach the sensor.

[0034] Typically, in the example above, the signal spikes will appear as peaks, possibly with a plateau, if the targeted change is not constant but occurs over a (short) limited period of time.

[0035] The example above allows for automatic plausibility checks, as the first signal reading indicates that the sensor is working and the change in the property was successful and detectable, and the second signal reading then indicates the leak.

[0036] According to the present disclosure, the at least one further predetermined section may comprise a second measuring section which is arranged upstream in the direction of flow with respect to the addition section, and the sensor may comprise a second sensor which is arranged at the second measuring section and monitors the chemical property, wherein the predetermined criterion may include that the time course of the signal of the second sensor exhibits a signal deflection.

[0037] In this configuration, since the injection section is located downstream of the measuring section, no signal is expected with a sealed heat exchanger, as the liquid should simply flow out of the liquid circuit after the injection section and not reach the sensor. Therefore, if the sensor registers at least one signal, this indicates that outgoing liquid has entered the incoming liquid, thus bringing modified liquid to the sensor. Here, as in the previous example, a time criterion can also be applied, based on when the modified liquid is expected to reach the sensor.

[0038] In this example, the signal deflection will typically be a peak, possibly with a plateau, if the targeted change is not constant but occurs over a (short) limited period of time.

[0039] The above example makes it possible to detect leaks even in configurations where no sensor is or can be placed downstream of the feed section.

[0040] According to the present disclosure, the first predetermined section can comprise a dialyzer, and the targeted modification can comprise changing the physical, in particular optical, property by operating the dialyzer and the resulting passage of a substance from the blood side of the dialyzer into the liquid. The at least one further predetermined section can comprise a third measuring section arranged upstream of the dialyzer in the direction of flow, and the sensor can comprise a third sensor arranged on the third measuring section that monitors the physical, in particular optical, property, wherein the predetermined criterion can include that the time course of the signal from the third sensor exhibits a signal deflection.

[0041] During dialysis, substances known as uremic toxins pass into the fluid; these can be detected by the third sensor. These toxins should exit the fluid circuit with the outflowing fluid, so there should be no signal spike upstream of the dialyzer. However, if there is a leak in the heat exchanger and outflowing fluid enters the inflowing fluid, these substances will enter the inflowing fluid and be detected by the sensor.

[0042] Typically, the substances will alter the physical, especially optical, properties of the liquid. Therefore, the sensor could, for example, be a sensor that measures a physical, especially optical, property.

[0043] In the present example, the signal deflection would typically manifest as a single change from a first signal value to a second signal value, as long as dialysis operation is maintained and nothing else is altered. Unlike a targeted change that occurs over a (short) limited period, a new equilibrium will be established.

[0044] As seen below, there are also cases in which the fluid is temporarily routed through a bypass instead of the dialyzer. This case is explained in more detail below, and the signal would then typically appear as two peaks: one when switching to the bypass and one when switching back to dialysis. In the latter case, a toxin bolus that builds up during bypass operation would reach the sensor. After the peak, however, the signal would likely not return to the level before the peak, but rather to the level before switching to the bypass.

[0045] One or more criteria for the temporal evolution can check the above signal changes, possibly in combination with a temporal criterion.

[0046] Examples where a targeted change is caused by the addition of substances can be difficult to implement during ongoing dialysis operations and may even disrupt the process. The example described above allows for reliable leak detection even during dialysis.

[0047] According to the present disclosure, the targeted modification can include changing the physical, in particular optical, property by switching between a first flow path of the liquid through the liquid circuit and a second flow path of the liquid through the liquid circuit, wherein the first flow path passes through a dialyzer and the second flow path passes through a bypass line around the dialyzer.

[0048] Switching elements may be provided to allow switching between the two flow paths, in particular automatically through appropriate control.

[0049] According to the present disclosure, the at least one further predetermined section can comprise a fourth measuring section which is arranged downstream in the direction of flow with respect to the dialyzer and the bypass line, and the sensor can comprise a fourth sensor which is arranged on the fourth measuring section and monitors the physical, in particular optical, property.

[0050] According to the present disclosure, the targeted modification can include switching from the first flow path to the second flow path, and the predetermined criterion can include that the time course of the signal of the third and / or fourth sensor immediately after switching is flatter than a reference course of the signal in a dense heat exchanger.

[0051] In other words, the property can be changed by passing the liquid through the bypass line instead of through the dialyzer.

[0052] This prevents uremic substances from passing into the fluid, and the concentration of non-uremic substances should change rapidly, particularly decreasing. However, if a leak in the heat exchanger allows fluid to pass from the outgoing to the incoming fluid, the signal will change more slowly, for example, decreasing more slowly. Thus, the curve will be flatter compared to the reference curve with a leak-free heat exchanger. The change in the signal can be considered a damped or slower change than in the reference curve.

[0053] This example also has the advantage that it is possible to reliably detect a leak in dialysis operations.

[0054] According to the present disclosure, the targeted change can include switching from the second flow path to the first flow path, and the predetermined criterion can include that the time course of the signal from the fourth sensor and / or the third sensor after switching exhibits an additional signal peak compared to a reference course of the signal in a dense heat exchanger. That is, after switching, the fluid is directed through the dialyzer instead of through the bypass line.

[0055] Switching to the dialyzer flow path again alters the composition and, in particular, the optical properties of the fluid downstream of the dialyzer and bypass line, due to the presence of uremic substances. This change will initially be immediately visible in the signal. However, no further signal spike should be observed if the heat exchanger is leak-free. The signal should stabilize at a certain value. A second signal spike, under otherwise unchanged conditions, indicates that the outgoing fluid is passing into the incoming fluid, and that a further signal spike occurs after the first. Therefore, detecting this additional signal spike indicates a leak. The criterion can thus be based on the presence of this additional signal spike, or more specifically, on the presence of both signal spikes.Additionally, a temporal criterion can also be applied, based on the expectation of when, in relation to the first signal deflection and / or the time of switching, the second signal deflection should be observed.

[0056] This example also has the advantage of allowing reliable detection of a leak during dialysis. Furthermore, by detecting two signal spikes, similar to what was described above, the functionality of the sensor and the detectability of a change in the fluid's properties based on the first signal spike can be verified.

[0057] According to the present disclosure, changing the chemical and / or physical property can be achieved by applying a bolus, in particular a conductivity bolus, to the injection section. The at least one criterion can include the sensor signal, in particular from a conductivity sensor, indicating the bolus, in particular indicating it at least once if the sensor is located upstream of the injection section in the direction of flow, or indicating it at least twice if the sensor is located downstream of the injection section in the direction of flow.

[0058] The indication of the bolus can be, for example, the signal deflection described above, such as a peak.

[0059] Conductivity is a suitable measure for chemical properties because it can depend on the chemical composition, more precisely the concentration of substances in the solution, and allows for a fast, inexpensive and simple measurement, especially compared to many chemical detection methods.

[0060] According to the present disclosure, this can include at least one criterion that the respective signal deflection occurs within a predetermined time interval, wherein the time interval includes a time point dependent on the flow rate and the geometry of the liquid circuit and the dialyzer, at which the volume of the liquid on which the change of the property was carried out is expected to reach the corresponding sensor, in particular, in the case of two signal deflections, when the volume reaches the sensor for the second time, possibly relative to the time of the earlier signal deflection.

[0061] As explained in detail above, a temporal criterion can be used in combination with other criteria. For example, if a first criterion, such as the presence of two signal spikes, is met, it can then be checked whether these spikes also meet a second criterion, such as the two signal spikes occurring at a specific time interval. This allows for more reliable detection overall.

[0062] It should be noted here that, unless explicitly stated otherwise, the features of the process in the present disclosure relate in particular to the intended operation of the blood treatment device designed accordingly.

[0063] The present disclosure also provides a blood treatment device.

[0064] The blood treatment device comprises an adjustment mechanism designed to selectively modify a chemical and / or physical property of the fluid at at least a first predetermined section of the fluid circuit during fluid transport. The adjustment mechanism may, for example, be configured to add substances to the fluid and / or to switch between a bypass line and a dialyzer, particularly automatically by a control unit.

[0065] The blood treatment device comprises a sensor for monitoring the temporal evolution of the chemical and / or physical properties at at least one further predetermined section of the fluid circuit, in particular wherein the sensor is arranged at the respective further predetermined section.

[0066] The blood treatment device includes a computing system designed to check whether the time course meets one or more predetermined criteria and to detect a leak in the heat exchanger if the time course meets the predetermined criterion(s). In particular, the computing system can also be configured to control the adjustment mechanism.

[0067] The blood treatment device comprises a fluid circuit and a heat exchanger, wherein the fluid circuit and the heat exchanger are arranged such that during operation a fluid is transported in such a way that the fluid flows into the fluid circuit of the blood treatment device through the heat exchanger and flows out of the fluid circuit through the heat exchanger.

[0068] The blood treatment device can be configured at least for collecting, degassing, and / or warming fluid as part of extracorporeal blood treatment. The blood treatment device can also be configured for adding concentrates to produce dialysis fluid and / or for fluid balance monitoring, including ultrafiltration. The blood treatment device can include a blood pump, a dialyzer, a pressure sensor, and / or a tubing system. The blood treatment device can also include one or more actuators and / or one or more (additional) sensors for performing dialysis treatment.

[0069] According to the present disclosure, the at least one first predetermined section may comprise an addition section, and the blood treatment device may include an addition device configured for adding a substance to the liquid, changing the amount or dosage of a substance added to the liquid, and / or diluting the liquid at the addition section to selectively modify its chemical and / or physical properties. The addition device may include an adjustment mechanism as described above, configured in particular for adjusting the amount and / or rate of addition of the substance to the liquid, especially controlled by the controller.

[0070] The at least one further predetermined section can include a first measuring section arranged downstream of the addition section in the direction of flow, and the sensor can include a first sensor arranged at the first measuring section that monitors the chemical property, wherein the predetermined criterion includes that the time course of the signal from the first sensor exhibits two successive signal peaks. For example, the first sensor can be a conductivity sensor.

[0071] The at least one further predetermined section can include a second measuring section arranged upstream of the addition section in the direction of flow, and the sensor can include a second sensor arranged at the second measuring section that monitors the chemical property, wherein the predetermined criterion can include that the time course of the signal from the second sensor shows a signal deflection. For example, the second sensor can be a conductivity sensor or an optical sensor.

[0072] According to the present disclosure, the first predetermined section can comprise a dialyzer, and the targeted modification can include changing the physical, in particular optical, property by operating the dialyzer and the resulting passage of a substance, for example via a semipermeable membrane, from the blood side into the fluid on the dialyzer fluid side of the dialyzer. The at least one further predetermined section can comprise a third measuring section arranged upstream of the dialyzer in the direction of flow, and the sensor can comprise a third sensor arranged on the third measuring section that monitors the physical, in particular optical, property, wherein the predetermined criterion can include that the time course of the signal from the third sensor exhibits a signal deflection.For example, the third sensor could be an optical sensor, such as an absorption measuring device.

[0073] According to the present disclosure, the blood treatment device can comprise a dialyzer and a bypass line, a first flow path of the fluid through the fluid circuit passing through the dialyzer, and a second flow path through the fluid circuit passing by the bypass line around the dialyzer, and at least one switching element, in particular a valve, configured for switching between the first flow path and the second flow path. The switching element can form the adjustment mechanism or be part of the adjustment mechanism. The switching element can be automatically switchable by means of the control system.

[0074] The targeted modification can include changing the physical, particularly optical, property by switching between the first and second flow paths using the switching element. In particular, the at least one further predetermined section can include a fourth measuring section arranged downstream of the dialyzer and the bypass line in the flow direction, and the sensor can include a fourth sensor located at the fourth measuring section that monitors the physical, particularly optical, property. For example, the fourth sensor can be an optical sensor, such as an absorption meter, transmission meter, reflection meter, fluorescence meter, or a laser-induced plasma spectroscopy meter.

[0075] The targeted modification can involve switching from the first flow path to the second flow path, and the predetermined criterion can include that the time course of the signal from the fourth sensor immediately after switching is flatter than a reference signal course for a sealed heat exchanger. Alternatively or additionally, the targeted modification can involve switching from the second flow path to the first flow path, and the predetermined criterion can include that the time course of the signal from the fourth sensor and / or the third sensor after switching exhibits an additional signal peak compared to a reference signal course for a sealed heat exchanger.

[0076] In particular, the blood treatment device may be configured to carry out the procedure according to the present disclosure, especially as described above.

[0077] The method of the present disclosure can be carried out in particular using the blood treatment device of the present disclosure, especially as described above.

[0078] The features and advantages described in connection with the procedure also apply accordingly to the blood treatment device. BRIEF DESCRIPTION OF THE FIGURES

[0079] Further examples and embodiments are explained below with reference to the figures. These show: Fig. 1 a schematic representation of a process according to the present disclosure; Fig. 2 a schematic representation of a system according to the present disclosure; Fig. 3 a schematic representation of a signal curve during bolus administration; Fig. 4 A schematic representation of a signal waveform in a bypass circuit. DETAILED DESCRIPTION OF THE INVENTION

[0080] In Fig. Figure 1 schematically illustrates a method for leak testing of a heat exchanger of a blood treatment device according to the present disclosure.

[0081] The procedure comprises, in step S11, transporting a liquid such that the liquid flows through the heat exchanger into a liquid circuit of the blood treatment device and flows out of the liquid circuit through the heat exchanger.

[0082] The method comprises, in step S12, during the transport of the liquid, the targeted modification of a chemical property and / or a physical, for example optical, property of the liquid at at least one first predetermined section of the liquid circuit.

[0083] The method comprises, in step S13, monitoring the temporal evolution of the chemical property and / or the physical, for example optical, property at at least one further predetermined section of the liquid circuit by means of a sensor which is arranged at the respective further predetermined section;

[0084] For example, the method includes monitoring based on physical quantities (conductivity, absorption, scattering or the like) that change due to a change in chemical composition.

[0085] The procedure includes, in step S14, checking using a computer system whether the time course meets one or more predetermined criteria.

[0086] The procedure includes, in step S15, detecting a leak in the heat exchanger if the time course meets the predetermined criteria.

[0087] The method can be used, for example, with the blood treatment device according to the present disclosure, in particular also as described in Fig. 2. However, it is also conceivable to perform the procedure using other blood treatment devices.

[0088] In Fig. Figure 2 shows an example of a blood treatment device 100 according to the present disclosure.

[0089] The blood treatment device comprises a fluid circuit 27 and a heat exchanger 2, wherein the fluid circuit and the heat exchanger are arranged such that during operation a fluid is transported in such a way that the fluid flows into the fluid circuit of the blood treatment device through the heat exchanger and flows out of the fluid circuit through the heat exchanger.

[0090] The blood treatment device comprises an adjustment mechanism, for example concentrate delivery device 5, concentrate delivery device 9, valve 15, valve 20 and / or valve 26, which is designed to selectively change a chemical property and / or a physical property of the liquid at at least one first predetermined section 11, 16, 25 of the liquid circuit during the transport of the liquid.

[0091] The blood treatment device comprises a sensor 8, 12, 21, 40 for monitoring the temporal evolution of the chemical property and / or the physical property at at least one further predetermined section of the fluid circuit, wherein the sensor is in particular arranged at the respective further predetermined section.

[0092] The blood treatment device includes a computing system 28, which is designed to check whether the time course meets one or more predetermined criteria and to detect a leak in the heat exchanger if the time course meets the predetermined criterion(s).

[0093] In an example, the at least one first predetermined section can comprise an addition section 7, 11 and the blood treatment device can include an addition device, for example the concentrate conveying device 5 and / or 9, which is configured to add a substance to the liquid, to change an addition quantity or dosage of a substance to the liquid and / or to dilute the liquid at the addition section in order to selectively change the chemical property and / or physical property.

[0094] The at least one further predetermined section can comprise a first measuring section 12a, which is arranged downstream in the flow direction with respect to the addition section 11, and the sensor can comprise a first sensor 12, which is arranged at the first measuring section 12a and monitors the chemical property, wherein the predetermined criterion includes that the time course of the signal of the first sensor has two successive signal peaks.

[0095] The at least one further predetermined section can comprise a second measuring section 8a, which is arranged upstream in the direction of flow with respect to the addition section 11, and the sensor can comprise a second sensor 8, which is arranged on the second measuring section 8a and monitors the chemical property, wherein the predetermined criterion includes that the time course of the signal of the second sensor has a signal deflection.

[0096] The at least one first predetermined section can comprise a dialyzer 16 and the targeted modification includes changing the chemical and / or physical, in particular optical, property by operating the dialyzer and the resulting transfer of a substance from the blood side of the dialyzer into the liquid. The at least one further predetermined section can comprise a third measuring section 40a, which is arranged upstream of the dialyzer 16 in the direction of flow, and the sensor can comprise a third sensor 40, which is arranged on the third measuring section 40a and monitors the physical property, wherein the predetermined criterion includes that the time course of the signal of the third sensor exhibits a signal deflection.

[0097] The blood treatment device can optionally also include a bypass line 25 and a first flow path of the fluid through the fluid circuit, which passes through the dialyzer 16, and a second flow path through the fluid circuit, which passes by the dialyzer 16 via the bypass line 25.

[0098] The blood treatment device may include at least one switching element, in particular valve 15, 20 and / or 26, which is designed to switch between the first flow path and the second flow path.

[0099] The targeted modification can include changing the chemical and / or physical, especially optical, properties by switching between the first flow path and the second flow path using the switching element.

[0100] The at least one further predetermined section can comprise a fourth measuring section 21a, which is arranged downstream in the flow direction with respect to the dialyzer 16 and optionally the bypass line 25, and the sensor can comprise a fourth sensor 21, which is arranged at the fourth measuring section 21a and monitors the physical property. The targeted change can include switching from the first flow path to the second flow path.The predetermined criterion can then include that the time course of the signal from the fourth sensor is flatter immediately after switching than a reference course of the signal in a sealed heat exchanger and / or the targeted change includes switching from the second flow path to the first flow path, and wherein the predetermined criterion includes that the time course of the signal from the fourth sensor after switching exhibits an additional signal peak compared to a reference course of the signal in a sealed heat exchanger. In particular, when checking for the flatter course, the fourth measuring section 21 can be arranged downstream with respect to the dialyzer and the bypass line (see sensor 21).

[0101] As mentioned above, a heat exchanger allows heat from the outgoing dialysate to be used to preheat the incoming permeate, which is colder than the dialysate. In current systems, this heat exchanger is generally assumed to be inherently reliable, meaning it is not expected to leak. However, in the event of a leak in the heat exchanger, the transfer of used dialysate to the fresh permeate or dialysis fluid side cannot be detected by standard dialysis machines. This could, in the worst-case scenario, lead to contamination of the dialysis fluid side.

[0102] As shown above, the present disclosure provides a method for checking the leak tightness of a heat exchanger in a blood treatment device (hereinafter described using a dialysis system as an example). For instance, a bolus can be applied on the dialysis fluid side (i.e., upstream of the dialyzer), and this bolus can be measured upstream of the application point if the heat exchanger leaks. The application point is, for example, the addition point (addition section) where a concentrate is added to the fluid, or the dialyzer itself.

[0103] Possible methods and devices according to the present disclosure have already been explained above, in particular with reference to Fig. 1 and Fig. 2.

[0104] The following will refer again to the Fig. Taking 2, further non-restrictive examples are explained in detail.

[0105] Fig. Figure 2 shows a schematic and simplified example of a blood treatment device 100, here using a dialysis system as an example. The fluid is also referred to as high-purity water or permeate, dialysis fluid, or used water or dialysate, depending on its position in the fluid circuit and its state. High-purity water, the so-called permeate, enters system 100 via inlet 1 and passes through heat exchanger 2. Heat transfer takes place in heat exchanger 2. The permeate absorbs thermal energy from the dialysate flowing through line 23 and is thus preheated. The permeate then flows through line 3 and into temperature control unit 4, where the water is heated to the required temperature, if necessary. Heat exchanger 2 can also be an integral component of temperature control unit 4.Driven by the first concentrate conveying device 5, a first concentrate from a first concentrate source 6 is added to the (optionally heated) water via the outlet 7. The amount added is monitored by a first measuring device 8 (also referred to as a sensor). In the same way, a second concentrate is extracted from a second concentrate source 10 by means of a second concentrate conveying device 9 and added to the water or the mixture of water and the first concentrate via the second outlet 11. The amount added is monitored by the second measuring device 12 (also referred to as a sensor). Driven by a first conveying device 13, the water or the mixture of water and at least one concentrate flows through the balancing device 14 and the dialyzer inlet valve 15 into the dialyzer or blood filter 16.The dialyzer 16 has a semipermeable membrane 17 which divides the dialyzer 16 into a dialysate side 18 and a blood side 19.

[0106] During dialysis, blood to be purified is drawn from a blood source P through the arterial line 30 by the blood pumping device 31 and conveyed through the blood side 19 of the dialyzer 16. Through selective diffusion and filtration, waste products pass from the blood side 19 across the semipermeable membrane 17 to the dialysate side 18. The resulting dialysate leaves the dialyzer 16 through the dialyzer outlet valve 20 and passes through an optional third measuring device 21.

[0107] This measuring device is preferably an optical sensor that measures or at least estimates the concentration of uremic substances in the dialysate. Absorption measurement is a suitable measuring principle. The dialysate is illuminated with nearly monochromatic light, preferably UV light with a wavelength between 200 and 320 nm, particularly 280 ± 15 nm, and the measurement is taken on the opposite side. The attenuation of the light, the so-called absorbance, is proportional to the concentration of at least one uremic substance.

[0108] The second pumping device 22 pumps the dialysate into the balancing device 14, which allows controlled removal of excess water from the blood source P. From there, it flows through line 23 to the heat exchanger 2 and then into the drain 24. Under normal operating conditions, the bypass line 25 is not used due to the closed bypass valve 26. However, the bypass valve 26 can be opened during bypass operation. When valves 15 and 20 are closed, the fluid from line 3 flows directly into line 23 via the bypass line 25. The optional fourth measuring device 40 (also referred to as a sensor) is similar to the optional third measuring device 21 and is located in line 3 between the heat exchanger 2 and the dialyzer 16.

[0109] As explained above, if heat exchanger 2 is defective, dialysate from line 23 can flow into and contaminate permeate-carrying or dialyze fluid-carrying line 3. This would also lead to a reduction in dialysis efficiency. The present disclosure describes a method for detecting a defect or leak in heat exchanger 2. This allows these problems to be identified and remedied.

[0110] The following will refer, by way of example, to… Fig. 2. It has been shown how, according to the present disclosure, a leak test can be made possible in various ways and at different points in the fluid circuit.

[0111] In a first example, which is based on the Fig. As described in section 3, a conductivity bolus is applied by the concentrate delivery device 9. This bolus can be routed either through the bypass line 25 or through the dialyzer 16. If the heat exchanger 2 is defective, part of the applied bolus enters line 3 and proceeds to the measuring device 8, which may be, for example, a temperature-compensating conductivity probe, resulting in a measurable change in conductivity. The bolus can be positive or negative. This means that the delivery rate of the concentrate delivery device 9 can be briefly increased or decreased. The latter is possible if the concentrate delivery device 9 has already been dosing.

[0112] Fig. Figure 3 shows, as an example, the signal waveforms at measuring devices 8 and 12 during a positive bolus flow through the concentrate pump 9. Due to the leak in the defective heat exchanger 2, the bolus, after passing through the hydraulic system (liquid circuit), may be registered in a weakened form at measuring device 8 and shortly thereafter again by measuring device 12. Therefore, it would even be sufficient to have the bolus generated by the concentrate pump 9 registered exclusively by measuring device 12, or a bolus generated by the concentrate pump 5 registered exclusively by measuring device 8. For the sake of completeness, a bolus generated by pump 5 can also be registered exclusively by sensor 12.

[0113] If the check is performed according to this principle during ongoing dialysis, the bolus can be bypassed around the dialyzer 16 via the bypass line 25 for the duration of the application, as previously described, in order to avoid altering the blood source P. Alternatively, a negative bolus can follow a positive one, so that there is no net diffusive change across the semipermeable membrane 17. The procedure can also be performed when no blood source P is yet connected and can only be carried out when concentrate is first aspirated from the concentrate source 10. This would be the case at the beginning of the preparation of the dialysis fluid. In this case, the conductivity change through the concentrate delivery device 9 does not need to be bolus-shaped, since any change could be detected by the measuring device 8.As soon as a leaking heat exchanger 2 is detected, the invention basically provides that the dialysis machine gives an optical, acoustic and / or haptic indication.

[0114] In a second example, the leak test is based on the assumption that the permeate or fresh dialyzer fluid upstream of the dialyzer 16 is free of contaminants, i.e., contains no uremic toxins, if the heat exchanger is leak-free. A leaking heat exchanger 2 can also be detected using the measuring device 40 in line 3. During therapy, uremic toxins diffuse from the blood side 19 across the membrane 17 to the dialysate side 18. Due to a defect, these toxins would pass from line 23 into line 3. A simple absorption measurement with the device 40 would thus allow the transfer of light-absorbing uremic toxins to be measured. The measuring device 40 can be located anywhere in line 3 between the heat exchanger 2 and the dialyzer 16.

[0115] In a third example, which is based on the Fig. As illustrated in Figure 4, a circuit to and from a bypass line is used for leak testing. Some dialysis machines already have a measuring device 21 (also referred to as a sensor) in the form of an optical sensor in the dialysate line 23 downstream of the dialyzer 16 to determine the dialysis effectiveness. If the measuring device 21 is located downstream of the bypass line 25, a leaking heat exchanger can be detected as follows. First, the system 100 is in normal operation during dialysis. That is, the dialysis fluid flows through the dialyzer 16 and picks up uremic toxins from the blood source P. The measuring device 21 detects light-absorbing substances.

[0116] When system 100 is switched to bypass mode, valves 15 and 20 close and valve 26 opens. In this state, fresh dialysis fluid flows through bypass line 25 and displaces the used dialysate in line 23. If heat exchanger 2 were functioning correctly, the measurement signal at device 21 would now drop sharply or even approach zero (see Fig. 4, solid line in the bypass). In the case of a defective heat exchanger 2, however, the drop in the measurement signal at 21 would take longer, since part of the contaminated dialysate is recirculated in heat exchanger 2 (see Fig. 4, dashed line in the bypass).

[0117] During the bypass, the dialysis fluid enclosed on dialysate side 18 becomes saturated with the permeable substances from the continuing blood circulation. This continues until a diffusive equilibrium is established between blood side 19 and dialysate side 18. The concentration of waste products on dialysate side 18 is now much higher than during normal operation.

[0118] When the bypass is now terminated or the system switches back to normal operation, the fresh dialyzer fluid displaces the saturated dialysate, whereupon a signal deflection can be detected at measuring device 21 due to the increased concentration. In the case of a defective heat exchanger 2, this bolus of uremic toxins would enter line 3 and, after passing through dialyzer 16, would again be detectable as a deflection at measuring device 21 (see Fig. 4, dashed line after the large deflection after the end of the bypass). However, if no substances pass through, i.e., if heat exchanger 2 is sealed / intact, a renewed deflection of the measurement signal would not be measurable (see Fig. 4, solid line after the large deflection after the end of the bypass).

[0119] Below is an explanation of the reference symbols in the example described above: 1 Permeate feed 2 heat exchangers 3 lines 4. Temperature control device 5 first concentrate conveying device 6 first concentrate source 7 Mouth of the first concentrate source 8 first measuring device 9 second concentrate conveying device 10 second concentrate source 11 Mouth of the second concentrate source 12 second measuring device 13 first conveying device 14 Accounting institution 15 Dialyzer inlet valve 16 Dialyzer 17 semipermeable membrane 18 Dialysate side 19 Blood page 20 Dialyzer outlet valve 21 third measuring device 22 second conveying device 23 Management 24 Drain 25 Bypass line 26 Bypass valve 27 Fluid Cycle 28 Computing system 30 arterial lines 31 Blood pumping device 32 venous line 40 fourth measuring device 100 dialysis systems P Blood source

[0120] Although the invention is illustrated and described in detail in the drawings and the preceding description, these illustrations and descriptions are to be considered exemplary and not limiting. The invention is not limited to the disclosed embodiments. In view of the preceding description and the drawings, it will be obvious to the person skilled in the art that various modifications can be made within the scope of the invention as defined in the claims.

Claims

[1] Method for leak testing of a heat exchanger (2) of a blood treatment device (100), comprising Transporting (S11) a liquid such that the liquid flows through the heat exchanger (2) into a liquid circuit (27) of the blood treatment device (100) and flows out of the liquid circuit (27) through the heat exchanger (2), during the transport of the liquid, targeted modification (S12) of a chemical property and / or a physical property of the liquid at at least one first predetermined section (7, 11, 16, 25) of the liquid cycle (27); Monitoring (S13) the temporal evolution of the chemical property and / or the physical property at at least one further predetermined section of the liquid circuit (27) by means of a sensor (8, 12, 21, 40) which is arranged at the respective further predetermined section; Check (S14) using a computer system (28) whether the time course meets one or more predetermined criteria; Determining (S15) a leak in the heat exchanger (2) if the time course meets the predetermined criteria. [2] Method according to claim 1, wherein the at least one first predetermined section (7, 11, 16, 25) includes an additional section (7, 11), and wherein the targeted modification includes changing the chemical and / or physical property by adding a substance to the liquid, changing the amount or dosage of a substance added to the liquid and / or by diluting the liquid at the addition section (7, 11). [3] Method according to claim 2, wherein the at least one further predetermined section comprises a first measuring section (12a) which is arranged downstream in the direction of flow with respect to the addition section (7, 11), and the sensor (8, 12, 21, 40) comprises a first sensor (12) which is arranged on the first measuring section (12a) and monitors the chemical and / or physical property, wherein the predetermined criterion comprises that the time course of the signal of the first sensor (12) has two successive signal peaks. [4] Method according to claim 2 or 3, wherein the at least one further predetermined section comprises a second measuring section (8a) arranged upstream in the flow direction with respect to the addition section (7, 11), and the sensor (8, 12, 21, 40) comprises a second sensor (8) arranged on the second measuring section (8a) and monitoring the chemical and / or physical property, wherein the predetermined criterion comprises that the time course of the signal of the second sensor (8) exhibits a signal deflection. [5] Method according to any of the preceding claims, wherein the first predetermined section (11, 16, 25) comprises a dialyzer (16) and the targeted modification comprises a change in the chemical and / or physical property by operating the dialyzer (16) and the resulting passage of a substance from the blood side (19) of the dialyzer (16) into the liquid and wherein the at least one further predetermined section comprises a third measuring section (40a) which is arranged upstream in the flow direction with respect to the dialyzer (16), and the sensor (8, 12, 21, 40) comprises a third sensor (40) which is arranged on the third measuring section (40a) and monitors the chemical and / or physical property, wherein the predetermined criterion includes that the time course of the signal of the third sensor (40) exhibits a signal deflection. [6] Method according to any of the preceding claims, wherein the targeted modification comprises changing the chemical and / or physical property by switching between a first flow path of the liquid through the liquid circuit and a second flow path of the liquid through the liquid circuit, wherein the first flow path passes through a dialyzer (16) and the second flow path passes through a bypass line (25) past the dialyzer (16). [7] Method according to claim 6, wherein the at least one further predetermined section comprises a fourth measuring section (21a) which is arranged downstream in the direction of flow with respect to the dialyzer (16) and the bypass line (25), and the sensor (8, 12, 21, 40) comprises a fourth sensor (21) which is arranged on the fourth measuring section (21a) and monitors the chemical and / or physical property. [8] Method according to claim 7, wherein the targeted change comprises switching from the first flow path to the second flow path and wherein the predetermined criterion comprises that the time course of the signal of a third sensor (40) and / or the fourth sensor (21) immediately after switching is flatter than a reference course of the signal in a dense heat exchanger. [9] Method according to claim 7 or 8, wherein the targeted changing comprises switching from the second flow path to the first flow path and wherein the predetermined criterion includes that the time course of the signal of the fourth sensor (21) after switching shows an additional signal deflection compared to a reference course of the signal in a dense heat exchanger, and / or wherein the at least one further predetermined section comprises a third measuring section (40a) which is arranged upstream in the flow direction with respect to the dialyzer (16), and the sensor (8, 12, 21, 40) comprises a third sensor (40) which is arranged on the third measuring section (40a) and monitors the chemical and / or physical property, wherein the predetermined criterion comprises that the time course of the signal of the third sensor (40) after switching has an additional signal deflection compared to a reference course of the signal in a dense heat exchanger. [10] Method according to one of the preceding claims, wherein the changing of the chemical and / or physical property is an application of a bolus, in particular a conductivity bolus, to the / an addition section (7, 11) and which comprises at least one criterion that the sensor signal, in particular a conductivity sensor, indicates the bolus, in particular indicates it at least once if the sensor (8, 12, 21, 40) is arranged upstream of the addition section in the direction of flow, or indicates it at least twice if the sensor (8, 12, 21, 40) is arranged downstream of the addition section in the direction of flow. [11] Method according to one of the preceding claims, wherein the at least one criterion comprises that the respective signal deflection occurs within a predetermined time interval, the time interval containing a time point dependent on the flow velocity and the geometry of the liquid circuit (27) and the dialyzer (16), at which the volume of the liquid at which the change of the property was carried out is expected to reach the corresponding sensor (8, 12, 21, 40), in particular, in the case of two signal deflections, when the volume reaches the sensor (8, 12, 21, 40) for the second time. [12] Blood treatment device (100) comprising a liquid circuit (27) and a heat exchanger (2), wherein the liquid circuit (27) and the heat exchanger (2) are arranged such that during operation a liquid is transported in such a way that the liquid flows through the heat exchanger (2) into the liquid circuit (27) of the blood treatment device (100) and flows out of the liquid circuit (27) through the heat exchanger (2), an adjustment mechanism (5, 9, 15, 20, 26) designed to selectively change a chemical property and / or a physical property of the liquid at at least one first predetermined section (7, 11, 16, 25) of the liquid circuit (27) during the transport of the liquid; a sensor (8, 12, 21, 40) designed to monitor the temporal evolution of the chemical property and / or the physical property at at least one further predetermined section of the liquid circuit (27); and a computing system (28) designed to check whether the time course meets one or more predetermined criteria and to detect a leak in the heat exchanger (2) if the time course meets the predetermined criterion(s). [13] Blood treatment device (100) according to claim 12, wherein the at least one first predetermined section (11, 16, 25) comprises an addition section (7, 11), and the blood treatment device comprises an addition device configured for adding a substance to the liquid, changing the amount added or dosage of a substance to the liquid and / or diluting the liquid at the addition section (11) for the purpose of selectively changing the chemical and / or physical properties, in particular wherein the at least one further predetermined section comprises a first measuring section (12a) arranged downstream in the flow direction with respect to the addition section (11), and the sensor (8, 12, 21, 40) comprises a first sensor (12) arranged at the first measuring section (12a) and monitoring the chemical property, wherein the predetermined criterion includes that the time course of the signal of the first sensor (12) exhibits two successive signal peaks, and / or wherein the at least one further predetermined section comprises a second measuring section (8a) which is arranged upstream in the direction of flow with respect to the addition section (11), and the sensor (8, 12, 21, 40) comprises a second sensor (8) which is arranged on the second measuring section (8a) and monitors the chemical and / or physical property, wherein the predetermined criterion includes that the time course of the signal of the second sensor (8) exhibits a signal deflection. [14] Blood treatment device (100) according to claim 12 or 13, wherein the first predetermined section (11, 16, 25) comprises a dialyzer (16) and the targeted modification comprises a change in the chemical and / or physical property by operating the dialyzer (16) and the resulting passage of a substance, in particular via a semipermeable membrane, from the blood side of the dialyzer into the liquid on the dialyzer fluid side of the dialyzer, and wherein the at least one further predetermined section comprises a third measuring section (40a) which is arranged upstream in the direction of flow with respect to the dialyzer (16), and the sensor (8, 12, 21, 40) comprises a third sensor (40) which is arranged on the third measuring section (40a) and monitors the chemical and / or physical property, wherein the predetermined criterion includes that the time course of the signal of the third sensor (40) exhibits a signal deflection. [15] Blood treatment device (100) according to one of claims 12 to 14, comprising a dialyzer (16) and a bypass line (25), a first flow path of the liquid through the liquid circuit (27), which passes through the dialyzer (16), and a second flow path through the liquid circuit (27), which passes through the bypass line (25) past the dialyzer (16), at least one switching element, in particular a valve (15, 20, 26), designed to switch between the first flow path and the second flow path, wherein the targeted modification includes a change in the chemical and / or physical property by switching between the first flow path and the second flow path using the switching element, wherein in particular the at least one further predetermined section comprises a fourth measuring section (21a) which is arranged downstream in the direction of flow with respect to the dialyzer (16) and the bypass line (25), and the sensor (8, 12, 21, 40) comprises a fourth sensor (21) which is arranged on the fourth measuring section (21a) and monitors the chemical and / or physical property, wherein, in particular, the targeted modification includes switching from the first flow path to the second flow path and wherein the predetermined criterion includes that the time course of the signal of the fourth sensor (21) immediately after switching is flatter than a reference course of the signal in a dense heat exchanger (2) and / or the targeted modification includes switching from the second flow path to the first flow path and wherein the predetermined criterion includes that the time course of the signal of the fourth sensor (21) and / or the third sensor (40) after switching has an additional signal deflection compared to a reference course of the signal in a dense heat exchanger (2).

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