MONITORING DEVICE FOR RECIRCULATION DETERMINATION

Description

[0001] The present disclosure relates to a monitoring device of an extracorporeal blood treatment machine, which is designed to detect a signal during dialysis treatment that represents a pollutant concentration in used dialysis fluid, as well as an associated monitoring method and an extracorporeal blood treatment machine with such a monitoring device. Technical background

[0002] In extracorporeal blood treatments, particularly dialysis, blood is drawn from a patient's blood vessel at a blood collection site via a shunt, purified in an extracorporeal blood treatment machine, especially a dialysis machine, and then returned to the patient downstream of the blood collection site via the same shunt. It sometimes happens that already purified blood flows back through the shunt to the collection site and is reintroduced into the extracorporeal blood treatment machine. This recirculation "dilutes" the blood entering the extracorporeal blood treatment machine with recirculated, already purified blood, thus impairing the effectiveness of the blood treatment. Therefore, recirculation is a significant concern in extracorporeal blood treatments.Any occurrence of recirculation should be detected as quickly and reliably as possible, and countermeasures should be initiated immediately. State of the art

[0003] To definitively determine recirculation, various point-based measurement methods exist for individual measurements, such as a commercially available system called Transonic. However, these methods do not allow for the reliable immediate detection of recirculation as soon as it occurs. Furthermore, online measurement methods are available, but these involve significant costs and equipment requirements.

[0004] In extracorporeal blood therapy, in addition to recirculation, a multitude of other parameters are monitored and adjusted. One example is the monitoring of treatment effectiveness / progression in an extracorporeal blood treatment machine, particularly a dialysis machine, using a Kt / V value (where K = clearance, t = dialysis time, and V = urea distribution volume), which is calculated from spectroscopic measurements and reflects the reduction in the concentration of uremic toxins in the used dialysis fluid. The Adimea system from B. Braun is one example of such a system, providing online information on treatment progress and enabling highly accurate real-time measurement of the Kt / V value, specifically a Kt / V Adimea value or a spKt / V value (single spool Kt / V value), during treatment.Adimea measures UV absorption in the dialysate outflow (i.e., in the used dialysis fluid) as a measure of the urea concentration in the patient's plasma, which is proportional to the concentration of UV-absorbing (urea-dependent) substances in the patient's blood. This proportionality also occurs at a constant recirculation rate, although the corresponding proportionality factor can change.

[0005] Accordingly, it is known that certain behavioral patterns of the Kt / V value, particularly of a Kt / V Adimea value (for example, a sudden increase in the corresponding curve after a reduction in blood flow rate), can indicate recirculation. However, the Kt / V value depends on a multitude of other factors, such as patient-specific parameters, various problems in the machine's piping system, various operating parameters of the extracorporeal blood treatment machine, and the set dialysis dose, which can be adjusted during treatment. Furthermore, the behavioral patterns indicative of recirculation either only occur with a specific parameter change, such as the aforementioned reduction in blood flow rate, and thus do not allow for online measurement, or are difficult or impossible to detect due to the large number of parameters involved.The current state of the art, as described above, involves either using additional, complex measuring devices for online measurement or, for example, performing individual measurements at regular intervals. While these measurements are reliable and accurate, they can lead to recirculation not being detected immediately. Therefore, the development of recirculation monitoring systems has so far focused heavily on improving measuring devices for online measurement.

[0006] For example, EP 2 783 716 A1 discloses a method that enables the detection of recirculation in a patient's access or a change in recirculation during ongoing blood treatment using a dialyzer. During the blood treatment, successive measurements are taken by a sensor at the dialyzer outlet, and a limit value is set for each measurement generated by the sensor or a quantity derived therefrom. If the measurement or the quantity derived therefrom reaches or exceeds the limit value, an action, such as the generation of a visual and / or audible warning, is initiated. Furthermore, a corresponding device and a corresponding computer program are described.

[0007] EP 2 783 715 B1 discloses a control method for a dialysis machine to enable the detection of recirculation on the dialyze fluid side in an arteriovenous inlet / outlet element, preferably a shunt, wherein the dialysis machine has at least one dialyze fluid inlet and at least one dialyze fluid outlet for a selected dialyze fluid and at least one dialyze fluid pump, which are in fluidic communication with at least one dialyzer, wherein a sensor is located downstream of the dialyzer in the direction of dialyze fluid flow, which detects a change in a physicochemical parameter of the outflowing dialyze fluid. Summary of the invention

[0008] The object of the invention is to reduce the disadvantages of the prior art. In particular, a simple, cost-effective monitoring device for an extracorporeal blood treatment machine is to be provided, which makes it possible to automatically, quickly, and reliably detect suspected signs of recirculation, for example, to prevent a patient from receiving an insufficient dialysis dose in the long term. Subsequently, a single measurement can verify or refute whether recirculation is actually present.

[0009] The problem underlying this invention is solved by a monitoring device with the features of claim 1. Advantageous embodiments are the subject of the dependent claims and will be explained later.

[0010] An analysis of the problems described above regarding state-of-the-art recirculation measurements revealed that these problems can be solved without requiring the detection of recirculation immediately after its occurrence (which is not achievable through individual measurements) or a reliable determination and measurement of existing recirculation (which is not possible using a Kt / V signal), in order to still enable a fast and reliable determination of recirculation.

[0011] The problem underlying the invention is solved by a monitoring device of an extracorporeal blood treatment machine, which is designed to detect a signal that (essentially continuously) represents a pollutant concentration in used dialysis fluid. This monitoring device is further designed to automatically evaluate the signal's progression or signal profile with respect to at least one predetermined indicator / signal profile indicator / signal profile pattern for a given recirculation and, upon detection of the at least one indicator, to output a trigger signal that automatically initiates a recirculation measurement or automatically prompts a user to initiate a recirculation measurement. A prerequisite for selecting the signal and the measuring cell that detects the signal (e.g.,The Kt / V measuring cell of the Adimea system requires a very stable and reliably measurable signal. A recirculation measuring cell, designed to perform recirculation measurements preferably as a single measurement, can accurately and reliably determine or verify existing recirculation. This advantageously allows for the immediate detection of recirculation and prevents patients from receiving an insufficient dialysis dose in the long term.

[0012] The monitoring device is further designed to differentiate the signal in order to calculate a differential signal. This differential signal can then be compared with at least one threshold value, whereby a specific frequency (e.g., more than three or four times) or duration of threshold exceedances, preferably within a specific time period, can be used as one of the indicators of existing recirculation. In this way, in particular, a sudden signal fluctuation and, if applicable, a significantly greater than expected decrease in pollutant concentration can be detected. Alternatively or additionally, a single threshold exceedance of the same or a different, higher threshold value can be detected as one of the indicators of existing recirculation. This makes it possible, in particular, to detect a sudden, sharp increase in the signal.Alternatively or additionally, a specific frequency or duration of instances where a further, lower threshold is undercut, preferably within a specific time period, can also be used as an indicator. This can be attributed to a fluctuating signal pattern and possibly to a significantly weaker decrease in pollutant concentration than expected. Accordingly, various indicators of recirculation can be derived from a simple differentiation of the signal (from the differential signal), which is a simple operation requiring little computational power.

[0013] The threshold(s) depend on the target treatment time and a signal value from one or more previous extracorporeal blood treatments of the specific patient, for example, an average of such signal values. This allows patient-specific parameters to be taken into account. For example, Kt / V values ​​at specific time points, a Kt / V signal waveform or its shape, a number of slope changes in the signal waveform, the magnitude of deviations between different signal waveforms, typical variability for the specific patient, averages, etc., can be considered as a reference for calculating the rapid value(s). For example, a number of acceptable signal jumps in a Kt / V signal for the specific patient can be adjusted, for instance, if the patient is known to be frequently restless, but recirculation has not yet been determined.

[0014] In other words, signal curves depicting the pollutant concentration in used dialysis fluid during extracorporeal blood treatment were analyzed, particularly with regard to recirculation. Various indicators were derived from the signal curve that can suggest recirculation in the currently treated patient. For example, the signal curve may indicate significantly reduced dialysis efficiency, i.e., a pollutant concentration decreasing much more slowly than expected, if constant recirculation is present. This can be explained by the fact that the blood being purified by the extracorporeal blood treatment machine is diluted by the already purified, recirculated blood, and thus relatively few pollutants can be removed. On the other hand, the signal curve may give the impression that the pollutant concentration is decreasing much faster than expected.The dialysis efficiency is significantly higher than expected, which may indicate increasing recirculation of already purified blood. Furthermore, an erratic, jumpy signal pattern may occur, which could be due to turbulence in the shunt through which the extracorporeal treatment machine is connected to the patient, or to patient-related parameters such as frequent patient movement. Such turbulence or frequent patient movement can also promote recirculation. Accordingly, an erratic, jumpy signal pattern can also indicate recirculation. Additionally, a single, sharp spike in the signal pattern may occur when recirculation begins. These signal patterns indicative of recirculation can, of course, overlap.

[0015] The indicators thus determined were stored in the monitoring device according to the invention, in particular in a storage unit thereof, so that this device can automatically isolate and recognize the indicators during the signal measurement. However, since the indicators can also have a multitude of other causes, a trigger or a release signal is subsequently issued after the relevant indicator has been determined. This trigger or release signal automatically initiates, for example, a precise individual measurement and preferably issues a warning signal if the presence of recirculation is confirmed. Alternatively, the trigger or release signal automatically indicates to the user that such an individual measurement should be initiated manually. In this way, it is possible to utilize the immediacy of the signal measurement without having to forgo a reliable determination of recirculation.Subsequently, the results of the recirculation or individual measurements thus initiated or triggered are preferably stored in a history for automatic or manual evaluation or control. Furthermore, automatically triggered / initiated measurements are preferably distinguished from manually triggered / initiated measurements, for example, by different colors or markers.

[0016] Preferably, the signal represents a Kt / V value, in particular a Kt / V-Adimea value determined with Adimea, or is a raw signal, preferably intensity and / or absorbance values ​​from a spectroscopic measurement, on the basis of which the Kt / V value can be calculated. The Kt / V value is routinely determined in various ways during extracorporeal blood treatments, for example, using the Adimea system from B. Braun, which enables a very stable and reliable online measurement of the Kt / V signal.

[0017] Preferably, the threshold value(s) depend on a target treatment time and a target signal value and / or a theoretically calculated signal value. For example, a Kt / V Watson value can be used for the entire treatment or parts of the treatment. With the Kt / V Watson value, the urea distribution volume (V) is calculated according to a so-called Watson formula, whereby the clearance (K) is determined either based on the properties of the dialyzer and / or the blood and, if applicable, the dialysis fluid flow, or using a table or similar. That is, the signal profile is compared with an ideal or theoretical signal profile, and a certain degree of deviation from this ideal or theoretical signal profile is used as an indicator of recirculation.

[0018] Preferably, the monitoring device can be configured to calculate an expected treatment time from the signal, indicating when a target signal value is expected to be reached, and to compare this with the target treatment time. A significant shortfall and / or a significant exceedance of the target treatment time serves as an indicator of recirculation. In other words, the intersection point of the signal with a target signal value or a target pollutant concentration is calculated based on its average slope. A significant shortfall (for example, an expected treatment time of 60% of the target treatment time) indicates that the pollutant concentration is decreasing significantly faster than expected, and a significant exceedance indicates that the pollutant concentration is decreasing significantly more slowly than expected.This is particularly advantageous because, through this monitoring of the expected treatment time, even signal curves with significant jumps can be easily evaluated with regard to their mean slope or with regard to the expected treatment duration.

[0019] Alternatively or additionally, it can be advantageous to compare the signal waveform with known, pre-stored signal waveform patterns that occur during recirculation, and to identify sufficient similarity between the signal and these known patterns as an indicator of recirculation. Such pre-stored patterns can be signal waveforms or templates typical of recirculation, for example, with a sudden, sharp rise or frequent jumps. In this case, the monitoring system is configured to frequently or continuously compare the signal waveform with these patterns, for example, using cross-correlation calculations, and to identify sufficient similarity as one of the indicators of recirculation.This approach is particularly advantageous when the raw signal, especially an intensity and / or absorption signal, is used to determine the indicator, as this eliminates the need for some potentially computationally intensive signal processing steps.

[0020] According to one aspect of the present invention, the monitoring device can be designed to initiate a plausibility check after the detection of at least one indicator, preferably immediately thereafter. That is, an additional check is initiated as soon as an indicator has been detected, in which it is verified whether the indicator can actually point to possible recirculation, or whether its presence is probable, or whether there are other parameters that could have triggered the appearance of the indicator. This is advantageous because unnecessary recirculation measurements can be avoided in this way, thereby minimizing disruption to the course of extracorporeal blood therapy and / or its monitoring.

[0021] Preferably, as part of the plausibility check, the occurrence of the indicator can be compared with other sensor data, preferably venous pressure. For example, if a frequently fluctuating signal pattern (especially a Kt / V curve) occurs, possibly simultaneously with strong fluctuations in arterial and venous pressure detected by corresponding pressure sensors, pressure readings from a venous pressure sensor are analyzed. If these pressure readings exceed a defined, possibly patient-specific, threshold value, such as 150 mmHg, possibly immediately after or concurrently with such signal patterns, this is an additional indication of a change in vascular access or suboptimal needle placement. Accordingly, in this case, the plausibility check result is positive, and a recirculation measurement is automatically initiated or a corresponding prompt is automatically issued to the user.

[0022] Alternatively or additionally, the appearance of the indicator can be compared with a change in an operating state or parameter of the extracorporeal blood treatment machine. For example, it is checked whether an operating parameter was changed (especially immediately) before the indicator appeared and whether the change in the signal curve associated with the indicator can be attributed to this changed operating parameter, which would lead to a negative plausibility check result. Furthermore, for example, if the indicator of a significantly excessive drop in pollutant concentration immediately follows a previous reduction in the blood flow rate, it can strengthen the suspicion of recirculation and thus lead to a positive plausibility check result.

[0023] Furthermore, the monitoring device can be configured to detect several indicators and compare them as part of a plausibility check. In this case, the monitoring device checks whether several of the indicators described above occur simultaneously, such as a frequently fluctuating signal pattern combined with a significantly too rapid or too slow decrease in the pollutant concentration. If so, it outputs a positive plausibility check result; if no further indicator is detected, it outputs a negative plausibility check result. This type of plausibility check can be performed based solely on the signal pattern. That is, no comparison with other sensors or the control system of the extracorporeal blood treatment machine is necessary.

[0024] Preferably, the monitoring device is further adapted to initiate additional measurements in a case where the recirculation measurement shows that no recirculation is present, in order to determine other possible causes for the presence of at least one indicator.

[0025] Furthermore, the problem underlying the invention is solved by a monitoring method of a monitoring device which corresponds to the monitoring device according to the invention described above. The monitoring method comprises the following steps: acquiring a signal that represents a pollutant concentration in used dialysis fluid, automatically evaluating the signal's trend with respect to at least one predetermined indicator for existing recirculation, and automatically initiating a recirculation measurement or issuing an automatic prompt to a user to initiate a recirculation measurement when the at least one indicator has been detected, in particular via a trigger or a trigger signal. Preferably, a further step can be provided in which a plausibility check is initiated after, and preferably immediately after, the at least one indicator has been detected.

[0026] Furthermore, the problem underlying the invention is solved by an extracorporeal blood treatment machine, preferably a dialysis machine, with a monitoring device described above.

[0027] Regarding the more detailed design of the monitoring method described above and the extracorporeal blood treatment machine, reference is made to the above description of the monitoring device according to the invention.

[0028] In other words, recirculation directly affects the shape of a Kt / V curve (Kt / V as f(t)). Since this shape is primarily monitored by the Adimea system, any deviation from the expected curve shape can be caused by recirculation. Indications of recirculation include, for example, jumps in the curve, a very flat, monotonic shape, an excessively steep slope, and so on. Various measures can be used for plausibility checks, such as comparing the results with stored curves, comparing them with values ​​determined using another method (e.g., Kt / V Watson), and additionally comparing them with the current machine state. The derivative of the Kt / V curve, especially the spKt / V curve, can be used in conjunction with a defined threshold value to identify a discontinuous slope. Repeated exceedance of the threshold then serves as a trigger for a recirculation measurement.

[0029] Or, to put it another way, the Kt / V curve, especially the spKt / V curve, and its derivatives can be continuously monitored during treatment. This data can then be used to test for uneven curve rises based on a threshold value. Peak values ​​exceeding the threshold can be counted. If the threshold is exceeded multiple times, for example, more than three or four times, the machine issues a warning indicating possible recirculation, or it can automatically initiate a measurement of this recirculation. A suitable threshold value can be determined from a desired treatment time and a target Kt / V value, or from a (desired) treatment time and a Kt / V value from previous treatments, or from a (desired) treatment time and a theoretically calculated Kt / V value using a Watson-V system, where the dialyzer's specifications must be known.

[0030] A similar approach is possible with the raw signals, i.e., intensity or absorbance. Likewise, searching for specific patterns using known distance measures could be employed to detect particular features or indicators within the respective curves. Additionally, linking features could contribute to increased trigger robustness, as could comparing them with other machine state variables, since parameter changes to the machine can sometimes generate certain features. Checking the machine state at the time a feature is detected can also serve as a plausibility check.

[0031] Examples of further features are described below: If a Kt / V curve exhibits abrupt changes and, for example, a venous pressure also exceeds a defined, possibly patient-specific, threshold (e.g., 150 mmHg), this would be an additional indication of a change in vascular access. Significantly elevated venous pressures can be an indicator of outflow stenosis. If there are no significant variations in the Kt / V curve, but its rise is considerably steeper than the expected rise for the respective patient, this can also serve as a trigger event (i.e., as a trigger for issuing the trigger or trigger signal). That is, the Kt / V curve can be significantly higher than a predicted, linear treatment course (Kt / V signal curve), so that the Kt / V target of, for example, 1.2 appears to be reached after only 60% of the treatment time.In such a case, exceeding an absolute threshold for the rise of the Kt / V curve / Kt / V signal pattern could serve as a trigger (indicator). Alternatively, determining the intersection point of the target Kt / V curve with the actual Kt / V curve or the predicted Kt / V curve (extrapolated from the currently available Kt / V data) could serve as a criterion. If this intersection point on the time axis lies significantly before the estimated time, this can indicate that significant recirculation is present. Since patient movements can lead to fluctuations in pressure, but also to fluctuations in the Kt / V curve, an additional analysis of simultaneously occurring, large fluctuations in arterial and venous pressure provides an indication of such movement. If a high venous pressure, a peak / signal spike in the derivation of the Kt / V curve / differential signal or similar is subsequently observed, a recirculation measurement can be initiated. Character description

[0032] An embodiment of the present invention is described in more detail below with reference to the accompanying figures. These figures are for illustrative purposes only and are not intended to limit the scope of the present invention. Fig. 1a bis Fig. 1f Kt / V signal curves according to an embodiment of the invention are shown, which may indicate a recirculation. Fig. 2a shows a typical, non-recirculating spKt / V signal waveform and its derivative and Fig. 2b shows a jumping spKt / V signal waveform and its derivative. Fig. 3 Figure 1 schematically shows an extracorporeal blood treatment machine with a monitoring device according to the invention. Fig. 4 shows a flowchart illustrating a process for determining and processing a recirculation indicator.

[0033] Fig. 1a bis Fig. 1f Each figure shows a diagram in which the course of a Kt / V signal Kt / Vactual over time t is represented as a solid line. Furthermore, a target Kt / V value Kt / Vtarget of 1.2 is indicated in the diagram. A dashed line shows a theoretical, linear Kt / V curve Kt / Vneo, where the target Kt / V value Kt / Vtarget is reached at a specific target treatment time ttarget. These figures differ with regard to the signal curves they depict, as described below.

[0034] Fig. 1a The Kt / V signal Kt / V Actual shows a flat signal curve. The Kt / V signal Kt / Vist is significantly flatter than the theoretical Kt / V curve Kt / Vtneo, and the target Kt / V value Kt / V Target is not expected to be reached within the target treatment time t Target. This may indicate recirculation, as in this case the blood flowing through the filter, which actually needs to be purified, is diluted by the already purified, recirculated blood. In this way, the concentration of pollutants dissolved in the blood decreases significantly more slowly than expected, which can be measured in the used dialysis fluid, for example, using the Adimea system from B. Braun. Accordingly, the Fig. 1a The Kt / V signal shown is an indicator of existing recirculation. Fig. 1b shows a flat signal curve, similar to that in Fig. 1a , which is additionally discontinuous or erratic. A signal waveform without jumps, as in Fig. 1a It occurs more frequently with treatment using a catheter connected to the patient than with extracorporeal blood treatments. The in Fig. 1b The depicted, erratic signal pattern may indicate turbulence in a shunt through which a patient is connected to the extracorporeal blood treatment machine, or it may be due to frequent patient movement. This, in combination with the flat signal pattern or as an isolated feature, can also point to and serve as an indicator of existing recirculation. In other words, constant recirculation will be indicated by a fluctuating curve and a poor treatment outcome. This can be identified by observing repetitive, short-term changes in the curve's slope and the poor treatment outcome (given a longer-term trend or a prediction of the signal or Kt / V value at the end of treatment).

[0035] Fig. 1c The signal curve shows a sharply rising Kt / V curve (Kt / V Actual). The Kt / V curve (Kt / V Actual) is significantly steeper than the theoretical Kt / V curve (Kt / V theo), and the target Kt / V value (Kt / V Target) is likely reached well before the target treatment time (t Target) is reached. This could indicate increasing recirculation, as in this case, more and more already purified blood flows back through the shunt into the extracorporeal blood treatment machine. Consequently, the blood flowing through the filter, which still needs to be purified, is increasingly diluted by already purified, recirculated blood.In this way, a Kt / V measuring cell, which measures the Kt / V signal (actual Kt / V), detects a steady decrease in the pollutant concentration, which generally indicates successful extracorporeal blood therapy, even though the decrease in pollutant concentration is mainly due to increasing recirculation and the actual treatment outcome is progressively worsening. This is usually noticeable because the extracorporeal blood therapy appears significantly more efficient than expected. Accordingly, a significantly excessive increase in the Kt / V signal can also be an indicator of existing recirculation. Fig. 1d shows a steep signal curve according to Fig. 1c , which additionally, as already mentioned in the context of Fig. 1b More precisely, the signal may be erratic or unsteady, which, both on its own and in combination with a steep signal curve, can serve as an indicator of recirculation. In other words, increasing recirculation is indicated by an erratic signal and a good treatment outcome, reflecting the increasing degree of recirculation. Therefore, indicators include short-term changes in the slope of the signal curve and an excessively good treatment outcome (given a longer-term trend or a forecast of the signal or Kt / V value at the end of treatment).

[0036] Fig. 1e und Fig. 1f Each shows a Kt / V signal Kt / V Ist, during which a sudden, sharp increase occurs. Fig. 1e This increase occurs at the beginning of the measurement, while it occurs during Fig. 1f This sudden, sharp increase in the Kt / V signal (Kt / VIst) only occurs during the course of the procedure. Such a sudden, sharp rise in the Kt / V signal can be attributed to the fact that, in the case of recirculation, the blood to be purified is suddenly diluted by the recirculated, already purified blood. Consequently, the concentration of pollutants in the blood decreases, resulting in a sudden increase in the Kt / V value, which is determined by measuring the used dialysis fluid. Thus, such a sudden, sharp increase in the Kt / V signal can also serve as an indicator of recirculation.

[0037] Fig. 2a Figure 1 shows a typical non-recirculating Kt / V signal (left), in particular an spKt / V signal such as that recorded using B. Braun's Adimea, and its derivative (right), which was calculated at regular, relatively short time intervals. It can be seen that the non-recirculating Kt / V signal increases essentially linearly. Irregularities occur only at the beginning of the measurement and towards the end of the spKt / V signal waveform shown here, the former being attributable to a slightly delayed start of the measurement. These irregularities are represented as signal peaks in the derivative of the spKt / V signal, which is otherwise essentially uniform with a mean slope of zero. A threshold value S is set such that the derivative always lies below this value for a theoretical or linear spKt / V signal waveform. The two in Fig. 2a The signal peaks occurring in the derivative of the spKt / V signal (the differential signal) reach or exceed this threshold S.

[0038] Fig. 2b The figure shows the corresponding Kt / V signal (left), specifically the spKt / V signal, in a case where recirculation may be present, as well as the derivative (right) of the signal, calculated at regular, relatively short time intervals. It can be seen that the Kt / V signal exhibits significant fluctuations in this case. These fluctuations or irregularities result in a highly variable derivative of the spKt / V signal with numerous positive and negative signal peaks. The threshold S, which is set such that the derivative always remains below it in a normal, non-recirculating spKt / V signal pattern, is frequently reached and exceeded. A certain number of such threshold exceedances, e.g., three or four, is considered an indicator of recirculation.

[0039] Fig. 3 Figure 1 schematically shows an extracorporeal blood treatment machine 1. During extracorporeal blood treatment, blood from a patient is supplied to a filter 2 or dialyzer via a blood supply line 4 equipped with an arterial pressure sensor 3, and the blood is returned from the filter 2 to the patient via a blood outlet 6 equipped with a venous pressure sensor 5. The blood flows through the filter 2, and waste products from the blood pass through a semipermeable membrane into a dialysis fluid flowing countercurrently through the filter 2. Fresh dialysis fluid is supplied to the filter 2 via a dialysis fluid supply line 7, and the used dialysis fluid is drained from the filter 2 via a dialysis fluid outlet 8. A Kt / V measuring cell 9 is located in the dialysis fluid outlet 8, which preferably continuously measures the Kt / V signal profile during extracorporeal blood treatment.This Kt / V measuring cell 9 transmits the Kt / V signal to a monitoring device 10 (alternatively, the Kt / V measuring cell 9 can be part of the monitoring device 10), which then performs the following with reference to . Fig. 4 carries out the described procedure.

[0040] The monitoring device 10 receives or determines the Kt / V signal in step S1. In step S2, the signal is processed, for example, with reference to Fig. 2a und 2b described, analyzed, and determined whether any of the above with reference to Fig. 1a bis 1f The described indicators for existing recirculation are present. If no such indicator is determined (in Fig. 4 (marked "no"), monitoring device 10 returns to step S1. However, if one of the indicators is detected (in Fig. 4 (marked with "yes"), a plausibility check is performed in step S3, in which further sensor data, such as readings from the venous pressure sensor 5 and, if applicable, the arterial pressure sensor 7, current operating parameters of the extracorporeal blood treatment machine 1, or the presence of other indicators are checked to determine whether the presence of recirculation could be a plausible cause for the occurrence of the indicator determined in step S2. If the plausibility check is negative (in Fig. 4 (marked "no"), monitoring device 10 returns to step S1. However, if the plausibility check is positive (in Fig. 4 (marked with "yes"), a trigger or activation signal is output in step S4, which is either directly output to a recirculation measuring cell 11, thereby automatically initiating an accurate, reliable recirculation measurement, or by which a request to initiate a recirculation measurement is automatically issued to a user, for example via a display or an audible signal. Liste der Bezugszeichen

[0041] 1 Extracorporeal blood treatment machine 2 Filter 3 Arterial pressure sensor 4 Blood supply 5 Venous pressure sensor 6 Blood drainage 7 Dialysis fluid supply 8 Dialysis fluid drainage 9 Kt / V measuring cell 10 Monitoring device 11 Recirculation measuring cell S1 Acquisition of the Kt / V signal S2 Analysis of the Kt / V signal / Determination of one of the indicators S3 Plausibility check S4 Output of the trigger signal Kt / V Actual Measured Kt / V Signal Kt / V Theoretical Kt / V Curve Kt / V Target Target Kt / V Value t Target Target Treatment Time

Claims

1. A monitoring device of an extracorporeal blood treatment machine, which is configured to detect a signal continuously representing a concentration of pollutants in a used dialysis liquid and to automatically evaluate a signal course with respect to at least one predetermined signal course indicator or signal course pattern for an existing recirculation, characterized in that the monitoring device is further configured to differentiate the signal for evaluation in order to calculate a differential signal and compare it with at least one threshold value, wherein a certain frequency or duration of threshold value overruns and / or a one-time threshold value overrun of the same or another threshold value is recognized as a signal course indicator or signal course pattern for an existing recirculation, and upon determination of the at least one signal course indicator or signal course pattern, to automatically initiate a recirculation measurement or automatically output a request for initiating a recirculation measurement to a user.

2. The monitoring device according to any of the preceding claims, wherein the signal represents a Kt / V value or is a raw signal, preferably intensity and / or absorption values of a spectroscopic measurement on the basis of which the Kt / V value can be calculated.

3. The monitoring device according to claim 1 or 2, wherein the threshold value depends on a desired treatment time as well as a desired signal value and / or a signal value of a previous extracorporeal blood treatment and / or a theoretically calculated signal value.

4. The monitoring device according to any of the preceding claims, which is arranged for calculating, from the signal, an expected treatment time at which a desired signal value is expected to be reached, and for comparing it with a desired treatment time, wherein a clear shortfall or a clear overshoot of the desired treatment time serves as a signal course indicator or signal course pattern for an existing recirculation.

5. The monitoring device according to any of the preceding claims, which is configured for comparing the signal course with known, previously stored reference patterns or patterns of a signal course which occur with an existing recirculation, and to recognize a sufficient correspondence of the signal with the known reference patterns or patterns as a signal course indicator or signal course pattern for an existing recirculation.

6. The monitoring device according to any of the preceding claims, which is further configured to initiate a plausibility check after the determination of the at least one signal course indicator or signal course pattern, preferably immediately thereafter.

7. The monitoring device according to claim 6, which within the framework of the plausibility check is configured for comparing the occurrence of the signal course indicator or signal course pattern with further sensor data, preferably a venous pressure, a change in an operational state or parameter of the extracorporeal blood treatment machine or a theoretically calculated signal course.

8. The monitoring device according to any of claims 6 and 7, wherein several signal course indicators or signal course patterns are determined and compared within the framework of the plausibility check.

9. An extracorporeal blood treatment machine, preferably a dialysis machine, comprising a monitoring device according to any of the preceding claims.