Abstract
A monitoring method for an extracorporeal blood treatment machine, a monitoring device of an extracorporeal blood treatment machine, and an extracorporeal blood treatment machine including a monitoring device. The monitoring device is configured to detect a signal representing a concentration of pollutants in a used dialysis liquid, to automatically evaluate a signal course with respect to at least one predetermined indicator for an existing recirculation, and to automatically initiate a recirculation measurement or automatically output a request for initiating a recirculation measurement to a user upon determination of the at least one indicator.
Claims
1. A monitoring device of an extracorporeal blood treatment machine, the monitoring device 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; differentiate the signal for evaluation in order to calculate a differential signal and compare it with a threshold value, wherein a certain frequency or duration of threshold value overruns and/or a one-time threshold value overrun of said threshold value or of another threshold value is recognized as the signal course indicator or signal course pattern for the existing recirculation; and automatically initiate a recirculation measurement or automatically output a request for initiating a recirculation measurement to a user upon determination of the at least one signal course indicator or signal course pattern.
2. The monitoring device according to claim 1, wherein the signal represents a Kt/V value or is a raw signal from which the Kt/V value is calculated.
3. The monitoring device according to claim 1, wherein the threshold value depends on a desired treatment time and 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 claim 1, 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 the expected treatment time with a desired treatment time, wherein a clear shortfall or a clear overshoot of the desired treatment time serves as the signal course indicator or signal course pattern for the existing recirculation.
5. The monitoring device according to claim 1, which is further configured for comparing the signal course with previously stored reference patterns or patterns of the signal course which occur with an existing recirculation, and to recognize a sufficient correspondence of the signal with the previously stored reference patterns or patterns of the signal course as the signal course indicator or signal course pattern for the existing recirculation.
6. The monitoring device according to claim 1, which is further configured to initiate a plausibility check after determining the at least one signal course indicator or signal course pattern.
7. The monitoring device according to claim 6, which within a framework of the plausibility check, is further configured for comparing an occurrence of the at least one signal course indicator or signal course pattern with further sensor data, 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 claim 6, wherein the at least one signal course indicator or signal course pattern comprises a plurality of signal course indicators or signal course patterns that are determined and compared within a framework of the plausibility check.
9. A monitoring method of a monitoring device according to claim 1, comprising the steps of: detecting a signal representing a concentration of pollutants in a used dialysis liquid; automatically evaluating the signal course with respect to the at least one predetermined signal course indicator or signal course pattern for the existing recirculation; and automatically initiating a recirculation measurement or outputting an automatic request for initiating a recirculation measurement to a user if the at least one signal course indicator or signal course pattern has been determined.
10. The monitoring method according to claim 9, further comprising the step of initiating a plausibility check.
11. An extracorporeal blood treatment machine comprising a monitoring device according to claim 1.
12. The monitoring method according to claim 10, wherein the step of initiating the plausibility check is performed immediately after the at least one signal course indicator or signal course pattern has been determined.
Description
BRIEF DESCRIPTION OF THE DRAWING FIGURES
[0030] In the following, an embodiment of the present invention is described in more detail on the basis of the attached Figures. These are merely illustrative and are not intended to limit the scope of the present invention.
[0031] FIGS. 1a-1f show Kt/V signal courses according to an embodiment of the invention, which may indicate a present recirculation.
[0032] FIG. 2a shows a typical, recirculation-free spKt/V signal course and its derivation.
[0033] FIG. 2b shows a jumping spKt/V signal course and its derivation.
[0034] FIG. 3 schematically shows an extracorporeal blood treatment machine with a monitoring device according to the invention.
[0035] FIG. 4 shows a flow chart illustrating a procedure for determining and processing a recirculation indicator.
DETAILED DESCRIPTION
[0036] FIGS. 1a to 1f each show a diagram in which a course of a Kt/V signal Kt/V.sub.Actual over time t is represented as a solid line. Furthermore, a desired Kt/V value Kt/V.sub.Desired of 1.2 is marked in the diagram. A dashed line indicates a theoretical linear Kt/V course Kt/V.sub.theo, with which the desired Kt/V value Kt/V.sub.Desired is reached at a defined desired treatment time t.sub.Desired. These Figures differ as described in the following with regard to the signal characteristics illustrated.
[0037] FIG. 1a shows a flat signal course of the Kt/V signal Kt/V.sub.Actual. The Kt/V signal Kt/V.sub.Actual is much flatter than the theoretical Kt/V course Kt/V.sub.theo and the desired Kt/V value Kt/V.sub.Desired is not expected to be reached within the desired treatment time t.sub.Desired. This can be an indication of a present recirculation, since in this case the blood flowing through the filter, which must actually be cleaned, is diluted by the already cleaned, recirculated blood. In this way, a concentration of pollutants dissolved in the blood decreases much more slowly than expected, which can be measured in the used dialysis liquid e.g. by means of the ADIMEA™ brand system from B. Braun. Accordingly, the Kt/V signal Kt/V.sub.Actual shown in FIG. 1a serves as an indicator for an existing recirculation. FIG. 1b shows a flat signal course, similar to FIG. 1a, which in addition is volatile or unsteady. A signal course without jumps as in FIG. 1a occurs more frequently in a treatment with a catheter connected to the patient than in extracorporeal blood treatments. The unsteady course shown in FIG. 1b may indicate turbulences in a shunt through which a patient is connected to the extracorporeal blood treatment machine, or may indicate frequent movements of the patient. Also this circumstance, both in combination with the flat signal course and as a stand-alone feature, may indicate an existing recirculation and as an indicator for it. In other words, a constant recirculation will be indicated by a jumping curve and a poor treatment outcome. This can be identified by observing repetitive, short-term changes in the slope of the curve and the poor treatment outcome (for a longer-term trend or prognosis of the signal or Kt/V value at the end of the treatment).
[0038] FIG. 1c shows a strongly increasing signal course of the Kt/V signal Kt/V.sub.Actual. The Kt/V signal Kt/V.sub.Actual is significantly steeper than the theoretical Kt/V course Kt/V.sub.theo, and the desired Kt/V value Kt/V.sub.Desired is expected to be reached well before the desired treatment time t.sub.Desired is reached. This can be an indication of an existing, increasing recirculation, since in this case an increasing amount of already purified blood flows back through the shunt into the extracorporeal blood treatment machine, so that the blood flowing through the filter, which still has to be cleaned, is increasingly diluted by already purified, recirculated blood. In this way, a Kt/V measuring cell measuring the Kt/V signal Kt/V.sub.Actual determines a steady decrease of the concentration of pollutants, which basically indicates a successful extracorporeal blood treatment, although the decrease of the concentration of pollutants is mainly due to the increasing recirculation and the actual treatment result deteriorates increasingly. This is mostly noticeable by the fact that the extracorporeal blood treatment appears to be much more efficient than expected. Accordingly, a Kt/V signal course that increases far too much can also be an indicator for an existing recirculation. FIG. 1d shows a steep signal course according to FIG. 1c, which additionally, as already described in more detail in the context of FIG. 1b, is volatile or unsteady, which can serve as an indicator for an existing recirculation either alone or in combination with a steep signal course. In other words, an increasing recirculation is indicated by a jumping signal and a good treatment result, which reflects the increasing degree of recirculation. Indicators are thus short-term changes in the slope of the signal course and the treatment result which is too good (for a longer-term trend or a prognosis of the signal or Kt/V value at the end of the treatment).
[0039] FIG. 1e and FIG. 1f each show a Kt/V signal Kt/V.sub.Actual in the course of which a sudden, strong increase occurs. In FIG. 1e, this increase occurs at the beginning of the measurement, whereas in FIG. 1f it only occurs in the course of the measurement. Such a sudden, strong increase of the Kt/V signal Kt/V.sub.Actual 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. Accordingly, 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 liquid. Thus, such a sudden, strong increase of the Kt/V signal can also serve as an indicator for an existing recirculation.
[0040] FIG. 2a shows a typical, recirculation-free Kt/V signal (left), in particular a spKt/V signal, as it is recorded, for example, by the ADIMEA™ brand system from B. Braun, and its derivative (right), wherein the derivative was calculated in regular, relatively short time intervals. It can be seen that the recirculation-free Kt/V signal increases essentially linearly. It is only at the beginning of the measurement and towards the end of the spKt/V signal course shown here that irregularities occur, wherein the former can be attributed to a slightly delayed start of the measurement. These irregularities are represented as signal peaks in the derivative of the spKt/V signal, which otherwise runs essentially uniformly with a mean slope starting from zero. A threshold value S is defined such that the derivative of a theoretical or linear spKt/V signal course is always lower. The two signal peaks of the derivative of the spKt/V signal (of the differential signal) occurring in FIG. 2a reach or exceed this threshold value S.
[0041] FIG. 2b shows the corresponding Kt/V signal (left), in particular the spKt/V signal, in a case where recirculation may have occurred, and the derivative (right) of the signal, wherein the derivative was calculated at regular, relatively short time intervals. It can be seen that the Kt/V signal jumps strongly in this case. These jumps or irregularities result in a strongly fluctuating derivative of the spKt/V signal with a multitude of both positive and negative signal peaks. The threshold value S, which is defined such that the derivative of a normal, recirculation-free spKt/V signal course is always lower, is often reached and exceeded. If there is a certain number, e.g. three or four, of such exceedances of the threshold value S, this is seen as an indicator for an existing recirculation.
[0042] FIG. 3 schematically shows an extracorporeal blood treatment machine 1. During an extracorporeal blood treatment, blood from a patient is supplied to a filter 2 or dialyzer via a blood supply line 4 having an arterial pressure sensor 3, and the blood from the filter 2 is returned to the patient via a blood discharge line 6 having a venous pressure sensor 5. The blood flows through the filter 2, with pollutants from the blood passing through a semipermeable membrane into a dialysis liquid flowing through the filter 2 in the countercurrent principle. For this purpose, fresh dialysis liquid is fed through a dialysis liquid supply line 7 into the filter 2 and the used dialysis liquid is discharged from the filter 2 through a dialysis liquid discharge line 8. In the dialysis liquid discharge line 8, a Kt/V measuring cell 9 is arranged, which measures the Kt/V signal course during an extracorporeal blood treatment preferably continuously. 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 method described below with reference to FIG. 4.
[0043] The monitoring device 10 receives or determines the Kt/V signal in step S1. In step S2, the signal is analyzed as described for example with reference to FIGS. 2a and 2b and it is determined whether one of the indicators for an existing recirculation described above with reference to FIG. 1a to if is present. If no such indicator is determined (marked “no” in FIG. 4), the monitoring device 10 returns to step S1. However, if one of the indicators is determined (marked “yes” in FIG. 4), a plausibility check is carried out with step S3, wherein further sensor data, e.g. measured values of the venous pressure sensor 5 and if applicable of the arterial pressure sensor 7, current operating parameters of the extracorporeal blood treatment machine 1, or the presence of further indicators are checked to determine whether the presence of recirculation can be a plausible cause for the occurrence of the indicator determined in step S2. If the plausibility check is negative (marked “no” in FIG. 4), the monitoring device 10 returns to step S1. However, if the plausibility check is positive (marked “yes” in FIG. 4), step S4 outputs a trigger or trigger signal, which is either directly output to a recirculation measuring cell 11, whereby an accurate, reliable recirculation measurement is initiated automatically, by means of which a request to initiate a recirculation measurement is automatically output to a user, e.g. via a display or an audible signal.
