WO2011069645A1

WO2011069645A1 - Device and method for monitoring an electrically operated pump arranged in a liquid system of an extracorporeal blood treatment device

Info

Publication number: WO2011069645A1
Application number: PCT/EP2010/007451
Authority: WO
Inventors: Ulrich Wernicke
Original assignee: Fresenius Medical Care Deutschland Gmbh
Priority date: 2009-12-11
Filing date: 2010-12-08
Publication date: 2011-06-16
Also published as: EP2509653A1; DE102009057858B4; EP2509653B1; DE102009057858A1

Abstract

The invention relates to a device and a method for monitoring an electrically operated pump arranged in a liquid system, in particular a dialysis liquid system, of an extracorporeal blood treatment device arranged, in particular an electric pump for delivering dialysis liquid. The device (30) according to the invention for monitoring is characterized by an evaluation unit (30b) comprising means for continuously determining the predefined threshold value, to which the pump flow or a quantity correlating with the pump flow are compared. In order to detect a periodically occurring increase of the pump flow or the quantity correlating with the pump flow, the pump flow or the quantity correlating with the pump flow is compared to the continuously calculated threshold value. Since the predefined threshold value is continuously adjusted, the aging of the pump or the delivery rate thereof has no influence on generating the control signal. A readjustment or calibration of the pump is therefore not necessary. Thus, the control signal is generated with a high amount of certainty and great reliability.

Description

Device and method for monitoring an im

Fluid system of an extracorporeal

Blood treatment device arranged electrically operated pump

The invention relates to a device and a method for monitoring an electrically operated pump arranged in the fluid system, in particular dialysis fluid system, of an extracorporeal blood treatment device, in particular an electric pump for conveying dialysis fluid.

The known devices for extracorporeal blood treatment, for example, devices for hemodialysis (HD) or hemofiltration (HF) and hemodiafiltration (HDF), have balancing systems for the exact accounting of the one

Dialyzer supplied fresh dialyzing fluid and discharged from the dialyzer spent dialysis fluid, taking into account the withdrawn via the membrane of the dialyzer the patient amount of liquid. The known volumetric balancing systems work with one or more balancing chambers, each of which is separated from a flexible partition in two balance chamber halves. By alternately filling and emptying the two chamber halves exactly equal volumes of dialysis fluid can be supplied to the dialyzer and removed from the dialyzer.

For pumping the fluids in the fluid system of the extracorporeal

Blood treatment devices generally use electrically operated pumps. In the known balancing systems, the problem arises of controlling the electrically operated pumps in such a way that the balancing chamber halves are alternately filled. The dialysis fluid pump must then be stopped when the fresh dialysis fluid in the one half of the balancing chamber consumes it

Dialysis fluid has displaced from the other half balance chamber. Then the balance chamber half, which previously contained used dialysis fluid, again with fresh dialysis fluid and the balance chamber half, the previously fresh

Contained dialysis fluid again filled with spent dialysis fluid. This process is referred to below as switching the balance chamber. To switch the balance chamber in the known balancing valves in the leading to the balance chamber halves supply lines and the of the

Balancing chamber halves arranged outgoing discharge lines. Such a thing

Balancing system is known for example from US 6,042,784.

When the movable partition in the balancing chamber when filling the one

Balancing half and emptying of the other half balance chamber has reached its end position, the pump current of the electrically operated pump increases to promote the

Dialysis fluid on. Balancing devices are known in which the time profile of the pump current for controlling the electrically operated pump and the valves in the dialysis fluid system is monitored. When the pump current exceeds a predetermined threshold, a control signal (trigger) is generated to stop the dialysis fluid pump and switch the valves.

The monitoring of the pump current has proven itself in practice. The disadvantage, however, is that the pump current depends on various factors that may change. For example, the pumps, in particular the gear pumps used, a permanent wear, which increases with age of the pump

Pump current changes. The pump current is also dependent on the set delivery rate of the pump. This shows that the change in the pump current due to changed flow rates is significantly greater than the increase of the pump current when the movable partition in the balancing chamber has reached the end position.

The invention has for its object to provide a device for monitoring an arranged in the fluid system of an extracorporeal blood treatment device electrically operated pump, which detects the periodically occurring current increase with high reliability and high security.

In addition, the invention has the object, a method for

Monitoring an extracorporeal in the fluid system

Blood treatment device arranged to provide electrically operated pump with which with high reliability and high security a periodically occurring current increase of the pump current can be detected.

Another object of the invention is to provide an extracorporeal blood treatment device with such a device for monitoring the fluid system of the

Blood treatment device arranged to provide electrically operated pump.

The solution of these objects is achieved according to the invention with the features of

Claims 1, 9 and 10. Advantageous embodiments of the invention are

Subject of the dependent claims.

The monitoring device according to the invention is characterized in that the evaluation unit has means for continuously determining the predetermined limit value with which the pump current or a variable correlating with the pump current is compared. A continuous determination of the predetermined limit value is understood as meaning both a continuous and a discontinuous determination of the limit value. The only decisive factor is that the specified limit value is constantly adjusted during monitoring.

The means for comparing the pump current or the pump current

correlating quantities are designed such that the pump current or the quantity correlating with the pump current is compared with the continuously calculated limit value for detecting a periodically occurring increase in the pump current or the quantity correlating with the pump current. Since the predetermined limit value is continuously adjusted, for example, the aging of the pump or its delivery rate has no influence on the generation of the control signal. A readjustment or

Calibration of the pump is therefore not required. Thus, the control signal is generated with high reliability and high reliability.

The correlating with the pump current size, for example, in a

Measuring resistor resistance drop, which is calculated according to Ohm's law from the product of current and resistance. In a preferred embodiment, the means for continuously determining the predetermined limit are arranged such that the predetermined limit is determined on the basis of two characteristic values which are continuously determined. The first value is characteristic of the pumping current or magnitude correlating with the pumping current prior to the periodic rise, while the second value of the pumping current or magnitude correlates with the pumping current during the periodic increase in pumping current or the magnitude correlating with the pumping current is.

In a further preferred embodiment, the first value is the minimum value of the pump current or the quantity correlating with the pump current prior to the periodically occurring increase, while the second value is the maximum value of the pump current or the quantity correlating with the pump current during the periodically occurring increase. From the minimum value and the maximum value, the predetermined limit value is then determined.

The predetermined limit value is calculated in a particularly preferred embodiment from the minimum value and the maximum value. In a particularly preferred embodiment, the predetermined limit value is the sum of the minimum value and the half of the difference between the maximum and minimum values. Consequently, the predetermined limit between minimum and maximum value lies on the edge of the current increase.

For the continuous adjustment of the two values for the calculation of the given

Limit value, the pump current or the correlating with the pump current variable is preferably monitored continuously or discontinuously, wherein the currently measured value for the pump current or the correlating with the pump current size with the previously determined minimum value or with the previously determined

Maximum value for the pump current or the correlating with the pump current size is compared. If the currently measured value is less than or greater than the previously measured value, the currently measured value is assumed to be the new minimum value or maximum value. A further particularly preferred embodiment provides that upon detection of a periodically occurring increase in the pump current or the quantity correlating with the pump current, a timer is started with a predetermined time interval, wherein the generation of the control signal is suppressed within the predetermined time interval. This has the advantage that interfering pulses occurring in practice on the measuring signal, which are to be fed back to the switching of the balancing chamber, can have no influence on the generation of the control signal. It is also advantageous if, during the predetermined time interval, the determination of the first and second values, in particular the minimum and maximum values for the pump flow or the variable correlating with the pump flow, is interrupted. This avoids that interference pulses on the measurement signal to a wrong adaptation of the given

Limit value can lead.

In the following an embodiment of the invention will be explained in more detail with reference to the drawings.

Show it:

Fig. 1 shows a device for extracorporeal blood treatment with a device for monitoring the fluid in the

Blood treatment device arranged dialysis fluid pump in a highly simplified schematic representation and

Fig. 2 shows the time course of the pump flow of the

Dialysis fluid pump of the device for extracorporeal

Blood treatment of Fig. 1 correlating size.

Fig. 1 shows the essential components of the device according to the invention for extracorporeal blood treatment in a highly simplified schematic representation of the device according to the invention for monitoring the arranged in the dialysis fluid system of the blood treatment device pump for conveying

Dialysis fluid grouted. The extracorporeal blood treatment device has a dialyzer or filter 1, which passes through a semipermeable membrane 2 into a blood chamber 3 and a

Dialysis fluid chamber 4 is divided. From the patient leads one

Blood supply line 5 to the inlet 3A of the blood chamber 3, while from the outlet 3B of the blood chamber 3 of the dialyzer 1, a Blutabführleitung 6 leads to the patient. In the blood supply line 5, a blood pump 7 for conveying the blood in the extracorporeal blood circulation I is connected.

The dialysis fluid system II of the blood treatment device comprises a

Balancing Device 8. Since balancing devices and blood treatment devices are generally known to the person skilled in the art, the balancing device 8 only becomes strong

simplified schematic representation shown. The balancing facility balances fresh versus used dialysis fluid. The fresh dialysis fluid is provided in a dialysis fluid source 9. From the dialysis fluid source 9, a dialysis fluid supply line 10 leads to the inlet 4A of FIG

Dialysis fluid chamber 4, while from the outlet 4B of

Dialysing fluid chamber 4 a dialysis fluid discharge line 11 leads to a drain 12.

The balancing device 8 is connected to the dialysis fluid supply and discharge line 10, 11. In the section of the Dialysierflüssigkeitsabführleitung 11 between dialyzer 1 and balancing device 8 is a dialysis fluid 13 for

Conveying the dialysis fluid. The dialysis fluid pump 13 is an electrically operated pump, in particular a gear pump.

The balancing device 8 preferably has two balancing chambers, of which only one balancing chamber 14 is shown schematically. The balance chamber 14 is divided by a movable partition 15 into a first and second balance chamber half 16, 17. The balancing chamber half 16 or 17 has an inlet 16A or 17A and a drain 16B or 17B. In the inlet or outlet of each balance chamber half 16, 17 is a shut-off device 18 A, 18 B or 19 A, 19 B connected to shut off the inlet and outlet or to be able to open. The shut-off valves are electromagnetically actuated valves, the be opened or closed to a balance chamber half with fresh or

to fill used dialysis fluid and to empty the other half of the balance chamber with spent or fresh dialysis fluid. With the opening or

Closing the respective shut-off valves, the dialysis fluid pump 13 must be stopped or started. The dialysis fluid pump must be stopped when one half of the balancing chamber is completely filled and the other balancing chamber half is completely emptied. The change between filling and emptying the

Balance chamber halves in the individual balance chamber cycles is referred to below as switching the balance chamber 14.

The balancing device described above is generally known to the person skilled in the art. Such a balancing device is described, for example, in DE 28 38 414 and US Pat. No. 6,042,784. Balancing devices can be used in the known extracorporeal blood treatment devices not only for balancing fresh versus used dialysis fluid, but also for balancing fresh dialysis fluid against substitution fluid.

The blood treatment device further has a central control unit 20, which via a control line T with the blood pump 7 and a control line 8 'with the

Balancing device 8 and a control line 13 'is connected to the dialysis fluid pump 13. The central control unit 20 actuates the shut-off devices 18A, 18B or 19A, 19B of the balancing device 8 and the dialysis fluid pump 13, so that fresh and used dialysis fluid are balanced, while the

Dialysis fluid flows through the dialysis fluid 4 of the dialyzer 1.

The device 30 for monitoring the dialysis fluid pump 13 arranged in the dialysis fluid system II will be described below. Instead of

Dialysis fluid pump, however, can also be monitored by an electrically operated substituate pump if dialysis fluid should be balanced against substitution fluid. The monitoring device 30 communicates via a data line 31 with the central control and computing unit 20. The monitoring device 30 can also be part of the control unit 20. The monitoring device 30 generates a control signal which the central control and processing unit 20 receives via the data line 31. When the control unit 20 receives the control signal, the control unit controls the balancer 8, which

Dialysis fluid 13 and the shut-off valves 18A, 18B and 19A, 19B such that the balance chamber 14 is switched, the dialysis fluid pump 13 is stopped.

The monitoring device 30 has a measuring unit 30A, which is connected to the dialysis fluid pump 13 via a measuring line 30A '. The measuring unit 30A measures a voltage U _meS s dropping across a measuring resistor (not shown), which is proportional to the pump current I of the dialysis fluid pump 13 according to Ohm's law.

In addition, the monitoring device 30 has an evaluation unit 3 OB for evaluating the time profile of the measured voltage U _meS s- _die

Evaluation unit 30B has means 31 for comparing the measured voltage U _mes s with a predetermined limit Utngger and means 32 for generating the control signal when the measured voltage U _{mess is} greater than the predetermined limit value Utrigger. Furthermore, the evaluation unit 3 OB means 33 for continuously determining the predetermined limit U ^ gger, which will be described below.

Fig. 2 shows the time course of the measured with the measuring unit 30A Voltage Umess- In Fig. 2 it can be seen that the voltage U s _MES at time points ti, t _2, ... t _n increases when the movable partition 15 the balance chamber 14 has reached its end position, ie, for example, the balance chamber half 16 completely filled and the balance chamber half 17 is completely emptied. At this time, the

Dialysis fluid pump 13 are stopped to switch the balance chamber. This is the time when the control signal is to be generated. Fig. 2 shows three consecutive balance chamber clocks T _l5 T ₂ , T ₃ .

For detecting the increase in current indicated by arrows in FIG. 2, ie the rising edge of the current increase, the current measured with the measuring unit 30A becomes Voltage U _meS s compared with a predetermined limit value Utrigger. If the measured voltage is greater than the predetermined limit, the positive edge of the current increase is detected.

The predetermined limit Utrig er is calculated from the measured voltage U _m j _n before the occurrence of the current increase and the measured voltage Umax during the current increase according to the following equation.

Utrigger ~ Umin ⁺ (Umax ^- U _m in) / 2) (1)

In this case, U _m j _{n is} the minimum voltage, ie the voltage before the stop of the flexible partition to the wall of the balance chamber and U _max the maximum voltage at the stop of the partition to the wall of the balance chamber.

For initialization, two values for U _m i _n and U _ma x are first determined. For this purpose, the voltage is measured continuously. If the instantaneously measured voltage U _{mess is} greater than the previously measured voltage, the instantaneous measured voltage is assumed to be the maximum value U _{max of} the voltage, while the instantaneous measured voltage is assumed to be the minimum value of the measured voltage U _m i _n , if present measured value of the voltage is less than the previously measured value of the voltage. Consequently, during initialization, U _m in and U _max are continuously updated. During initialization, the occurrence of the first increase in current is detected when the difference between U _max and U _m j _{n is} greater than a first predetermined limit value. For the subsequent balancing chamber cycles, the predetermined limit value is calculated continuously according to equation (1), whereby U _m i _n and U _ma x are continuously adapted.

The calculation of the new limit value in a balancing chamber cycle takes place in each case on the basis of the previously updated values for U _m i _n and O _max . As a result, the default limit Utrigger is re-set for each balancing chamber clock when the values have changed. So if the measured voltage or pump current should increase due to the aging of the pump, it will be due to the aging of the pump

attributable increase in the quiescent current in the calculation of the predetermined Limit value consideration. Also, a current increase of the quiescent current is taken into account, which is due to a higher flow rate of the pump. Therefore, the positive edge of the current increase with high reliability and large

Safety can be detected independently of these factors.

In practice, it has been shown that interference pulses can occur on the measuring signal U _meSs immediately after the switching of the balance _chamber . These glitches may result in generation of a control signal when the glitch is greater than the threshold. The interference pulses can also lead to the determination of incorrect values for U _max .

The means 33 for continuously determining the predetermined limit value have a timer 33 A, which sets a predetermined time interval At after the determination of a current increase in a previous balance chamber cycle. During this predetermined time interval At, the generation of a new control signal in a subsequent balancing chamber clock is suppressed. The predetermined time interval Δt is dimensioned such that interference pulses can no longer be expected after the time interval has expired. In any case, the time interval must be less than the time between two balancing chamber cycles, since otherwise the control signal for the next switching of the balancing chamber could not be generated.

During the predetermined time interval Δt, preferably not only the generation of the control signal is interrupted, but also the determination of new values for U _m i _n and U _max , so that the values for U _m i _n and U _{max are} only updated if glitches occur the measurement signal is no longer expected.

Claims

claims

1. A device for monitoring an electrically operated pump arranged in the fluid system of an extracorporeal blood treatment device with a measuring unit (30A) for measuring the pump current or a variable correlating with the pump flow, an evaluation unit (30B) for evaluating the time profile of the

Pump current or the correlating with the pump current size, comprising:

Means (31) for comparing the pump current or the quantity correlating with the pump flow with a predetermined threshold,

Means (32) for generating a control signal when the pump current or the magnitude correlating with the pump current is greater than the predetermined threshold, characterized in that the evaluation unit (30B) comprises means (33) for continuously determining the predetermined threshold value Utrigger on the basis of the pump current or the quantity correlating with the pump current, wherein the means (31) for comparing the pump current or the variable correlating with the pump current are designed such that the pump current or the quantity correlating with the pump current is at the continuously determined limit value Detection of a periodically occurring increase in the pump current or the size correlated with the pump current is compared.

2. Device according to claim 1, characterized in that the means (33) for continuously determining the predetermined limit value Utngger are formed such that the predetermined limit value is calculated from a first value U _m i _n , for the pump flow or with the Pump current correlating magnitude before the periodic increase of the pump current is characteristic, and a second value U _{max is} calculated, which is characteristic of the pump current or the pump current correlating factor during the periodic increase of the pump current or the pump current correlating magnitude.

3. Apparatus according to claim 2, characterized in that the first value of the minimum value U _m j _{n of} the pump current or with the pump current

is correlated magnitude before the periodically occurring rise, wherein the means (33) for continuously determining the predetermined limit value are designed such that the pump current or with the pump current

correlating size is continuously monitored to the minimum value.

4. The device according to claim 3, characterized in that the means (33) for continuously determining the predetermined limit value are designed such that the value currently measured with the measuring unit (30A) for the

Pump current is compared with the previously determined minimum value for the pump current, wherein the currently measured value is assumed as a new minimum value when the currently measured value is smaller than the previously determined minimum value.

5. Device according to one of claims 2 to 4, characterized in that the second value of the maximum value U _{max of} the pump flow or with the

Pump current correlating magnitude during the periodic increase, wherein the means (33) for continuously determining the predetermined

Limit value are formed such that the pump current or the correlating with the pump current size continuously monitored to the maximum value becomes.

6. The device according to claim 5, characterized in that the means (33) for continuously determining the predetermined limit value are designed such that the value currently measured by the measuring unit (30A) for the

Pump current is compared with the previously determined maximum value for the pump current, wherein the currently measured value is assumed as a new maximum value when the currently measured value is greater than the previously determined maximum value.

7. Device according to one of claims 1 to 6, characterized in that the means (33) for continuously determining the predetermined limit value, a timer (33A) having a predetermined time interval, wherein the means (33) for continuously determining the predetermined limit value such in that the timer (33A) is started when an increase of the pump current or the quantity correlated with the pump current is detected, wherein the generation of the control signal is interrupted within the predetermined time interval.

8. Device according to one of claims 5 to 7, characterized in that the means (33) for continuously determining the predetermined limit value are formed such that the predetermined limit Logg _it is calculated from a correlated with the measured pump current size as follows:

Utrigger ^- U _m in + ((U _m ax ^- U _m j _n ) / 2) where: U _m i _{n is} the minimum value for the magnitude correlating with the pump current and Umax is the maximum value for the magnitude correlating with the pump current.

9. A device for operating a balance chamber of a balancing device of an extracorporeal blood treatment device with an electrically operated pump (7), characterized in that a device according to one of Claims 1 to 8 for monitoring the electrically operated pump (7) is provided for operating the balance chamber.

10. A device for extracorporeal blood treatment with a device according to one of claims 1 to 9.

11. A method for monitoring an electrically operated pump arranged in the fluid system of an extracorporeal blood treatment device, comprising the following method steps:

Measuring the pump current or a quantity correlating with the pump current,

Evaluation of the time course of the pump flow or with the

Pump current correlating magnitude, wherein: the pump current or the value correlating with the pump current is compared with a predetermined limit, and a control signal is generated when the pump flow or with the

Pumping current correlating magnitude is greater than the predetermined limit value, characterized in that the predetermined limit is determined based on the time course of the pump current or the correlating with the pump current size continuously, the pump current or the correlating with the pump current size with the continuously determined Limit for detecting a periodically occurring increase of the pump current or the correlating with the pump current size is compared.

12. The method according to claim 11, characterized in that the predetermined limit value is calculated from a first value which is characteristic of the pump current or the quantity correlating with the pump current before the periodically occurring increase of the pump current, and a second value is calculated is characteristic of the pump current or the quantity correlating with the pump current during the periodically increasing pump current or the quantity correlated with the pump current.

13. The method according to claim 12, wherein the first value is the minimum value of the pump current or the quantity correlating with the pump current before the periodically increasing pump current or the quantity correlating with the pump current, the pump current or the pump current correlating Size is continuously monitored for the minimum value.

14. The method according to claim 13, characterized in that the currently

measured value for the pump current is compared with the previously determined minimum value for the pump current, wherein the currently measured value is assumed as a new minimum value when the currently measured value is smaller than the previously determined minimum value.

15. The method according to any one of claims 12 to 14, characterized in that the second value of the maximum value of the pump current or the correlating with the pump current magnitude during the periodically occurring increase of the

Pump current or the size correlating with the pump current, wherein the pump current or the correlating with the pump current size is continuously monitored to the maximum value.

16. The method according to claim 15, characterized in that the currently

measured value for the pump current or with the pump current

correlating size with the previously determined maximum value for the Pump current is compared, wherein the currently measured value is assumed as a new maximum value when the currently measured value is greater than the previously determined maximum value.

17. The method according to any one of claims 11 to 16, characterized in that a timer is started with a predetermined time interval when an increase in the pump current or the correlating with the pump current size is detected, wherein within the predetermined time interval, the generation of the control signal is interrupted ,

18. The method according to any one of claims 15 to 17, characterized in that the predetermined limit Utngger is calculated as follows:

Utngger ^- U _m j _n Ί ^" ((Umax ^- U _m in) / 2) where: U _m i _{n is} the minimum value for the magnitude correlating with the pump current and U _{max is} the maximum value for the magnitude correlating with the pump current.

19. A method for operating a balance chamber of a balancing an extracorporeal blood treatment device with an electrically operated pump, characterized in that the electrically operated pump is monitored by a method according to any one of claims 11 to 18.