Method for regulating the supply of substituate during extracorporeal blood treatment and extracorporeal blood treatment device comprising a unit for regulating the supply of substituate

Abstract

The present invention relates to a method for regulating supply of substituate in an extracorporeal blood treatment with an extracorporeal blood treatment apparatus comprising a dialyzer divided by a semipermeable membrane into a blood chamber and a dialyzing fluid chamber and a device for supplying substituate. Moreover, the present invention relates to an extracorporeal blood treatment apparatus having a device for regulating supply of substituate. Regulation of supply of substituate in the extracorporeal blood treatment takes place as a function of the rheological loading of the dialyzer. To regulate supply of substituate during extracorporeal blood treatment, rheological loading of the dialyzer is determined from transmembrane pressure on the dialyzer and flow resistance of the dialyzer and substituate rate is increased or reduced according to the loading. The selection of dialyzer parameters or blood parameters is therefore no longer necessary and the distinction between pre-dilution and post-dilution is also made obsolete.

Claims

1. An apparatus for hemodiafiltration treatment, comprising: an extracorporeal blood circuit comprising a blood pump; a dialyzing fluid system; a dialyzer divided by a semipermeable membrane into a blood chamber and a dialyzing fluid chamber, the blood chamber being part of the extracorporeal blood circuit, the dialyzing fluid chamber being part of the dialyzing fluid system, and the blood pump being arranged along the extracorporeal blood circuit upstream of the blood chamber; a substituate dose rate controller configured to increase or decrease a rate of dosing substituate to the extracorporeal blood circuit; a sensor system for ascertaining a rheological loading of the dialyzer, the sensor system comprising a three-point measuring system for measuring transmembrane pressure, and a pressure pulse measuring sensor for measuring longitudinal flow resistance along the dialyzer fibers; and a control unit in communication with the sensor system and the substituate dose rate controller, wherein the sensor system, together with the control unit, is configured to ascertain a transmembrane pressure and a longitudinal flow resistance along the dialyzer fibers, and the control unit is configured to (1) plot a first evaluation quantity (HEMO_Priority) based on a measured transmembrane pressure, (2) plot a second evaluation quantity (BLKD_Priority) based on a measured longitudinal flow resistance along the dialyzer fibers, (3) form a priority pair (HEMO_Priority/BLKD_Priority) from the first evaluation quantity and the second evaluation quantity, (4) compare the priority pair to priority pairs in a two-dimensional matrix that assigns to each priority pair a substituate dose rate increase or decrease value, (5) based on the comparison, assign a corresponding substituate dose rate increase or decrease value, and (6) control a rate of dosing substituate based on the priority pair and the corresponding assigned substituate dose rate increase or decrease value.

2. The apparatus of claim 1, further comprising a memory having stored therein the two-dimensional matrix of priority pairs.

3. The apparatus of claim 1, wherein the first evaluation quantity is scaled to be within an evaluation scale of 0 to 100%, the second evaluation quantity is scaled to be within an evaluation scale of 0 to 100%, the two-dimensional matrix comprises a two-dimensional coordinate system, and the priority pair comprises a point in the two-dimensional coordinate system.

4. The apparatus of claim 1, wherein the substituate dose rate controller comprises a substituate supply device comprising a first substituate pump and being configured to supply substituate at a preset substituate rate to the extracorporeal blood circuit.

5. The apparatus of claim 1, wherein the sensor system comprises a blood pressure sensor in sensing communication with the extracorporeal blood circuit downstream of the blood chamber, the blood pressure sensor being connected to at least two data lines.

6. The apparatus of claim 5, wherein the control unit comprises a control and computing unit in communication, through data lines including the at least two data lines, with the sensor system, the blood pump, and the first substituate dose rate controller.

7. An apparatus for extracorporeal blood treatment, comprising: an extracorporeal blood circuit comprising a blood pump; a dialyzing fluid system, comprising a dialyzing fluid supply line, a dialyzing fluid discharge line having incorporated therein a dialyzing fluid pump, and an ultrafiltrate line that branches off of the dialyzing fluid discharge line and has incorporated therein an ultrafiltrate pump; a dialyzer divided by a semipermeable membrane into a blood chamber and a dialyzing fluid chamber, the blood chamber being part of the extracorporeal blood circuit, the dialyzing fluid chamber being part of the dialyzing fluid system, and the blood pump being arranged along the extracorporeal blood circuit upstream of the blood chamber; a balancing device that is in fluid communication with the dialyzer via a dialyzing fluid supply line and that is located upstream of the dialyzer, said balancing device comprising a first balancing chamber and a second balancing chamber, wherein the first balancing chamber and the second balancing chamber are configured to be operated anti-cyclically, and the balancing device being configured so that that only as much dialyzing fluid can flow via the dialyzing fluid supply line as dialyzing fluid can flow away via the dialyzing fluid discharge line; a substituate supply device comprising a first substituate pump, a substituate supply, and a substituate line, the substituate supply device being in fluid communication with the extracorporeal blood circuit via the substituate line, the substituate supply device being configured to supply substituate at a preset substituate rate to the extracorporeal blood circuit; a sensor system comprising a blood pressure sensor in sensing communication with the extracorporeal blood circuit downstream of the blood chamber, the blood pressure sensor being configured to generate a blood pressure signal, and the blood pressure sensor being connected to at least two data lines; a control and computing unit in communication, through data lines including the at least two data lines, with the sensor system, the blood pump, and the first substituate pump, wherein the control and computing unit is configured to (1) calculate a first evaluation quantity (HEMO_Priority) based on a sensed transmembrane pressure or variable correlating with the transmembrane pressure, (2) calculate a second evaluation quantity (BLKD_Priority) based on a sensed longitudinal flow resistance or variable correlating with the longitudinal flow resistance, (3) form an evaluation pair (HEMO_Priority/BLKD_Priority) from the first evaluation quantity and the second evaluation quantity, and (4) regulate the supply of substituate based on the evaluation pair, wherein the apparatus comprises a memory having stored therein a two-dimensional matrix of evaluation pairs and that assigns to each evaluation pair a value corresponding to a required change in substituate rate, wherein the apparatus is configured to compare the evaluation pair formed by the control and computing unit to the evaluation pairs of the two-dimensional matrix, and regulate the substituate rate by changing the substituate rate by a value corresponding to a required change and assigned to the evaluation pair by the two-dimensional matrix, wherein the sensor system further comprises: a first pressure sensor in communication with the dialyzing fluid system upstream of the dialyzing fluid chamber and located along the dialyzing fluid supply line, the first pressure sensor being configured to sense a first pressure and to generate a first pressure signal; and a second pressure sensor in communication with the dialyzing fluid system downstream of the dialyzing fluid chamber and located along the dialyzing fluid discharge line, the second pressure sensor being configured to sense a second pressure and to generate a second pressure signal, wherein the at least two data lines of the sensor system comprise a first blood pressure data line and a second blood pressure data line, and the control and computing unit is configured to receive the first and second pressure signals via respective data lines including the first and second blood pressure data lines, wherein the blood pump is configured to generate pressure pulses in the extracorporeal blood circuit upstream of the dialyzer, the semipermeable membrane is configured to transmit and attenuate the pressure pulses, and the control and computing unit is configured to split up a pressure signal measured downstream of the dialyzer into a fundamental component and at least one harmonic, the longitudinal flow resistance or the variable correlating with the longitudinal flow resistance being determined based on a ratio of the fundamental component and the at least one harmonic, wherein the sensor system, together with the control and computing unit, is configured to determine the transmembrane pressure, or the variable correlating with the transmembrane pressure, via the blood pressure signal, the first pressure signal, and a second pressure signal, wherein the sensor system, together with the control and computing unit, is also configured to determine the longitudinal flow resistance, or the variable correlating with the flow resistance, via the blood pressure signal but not the first pressure signal, and wherein the first evaluation quantity is scaled to be within an evaluation scale of 0 to 100%, the second evaluation quantity is scaled to be within an evaluation scale of 0 to 100%, the two-dimensional matrix comprises a two-dimensional coordinate system, and the evaluation pair comprises a point in the two-dimensional coordinate system.

8. The apparatus according to claim 7, wherein the control and computing unit is configured to control the first substituate pump to adjust the preset substituate rate by the value corresponding to the required change.

9. The apparatus according to claim 7, wherein the first substituate pump is in fluid communication with the extracorporeal blood circuit to supply substituate to the extracorporeal blood circuit upstream of the dialyzer, and the substituate supply device further comprises a second substituate pump in fluid communication with the extracorporeal blood circuit to supply substituate to the extracorporeal blood circuit downstream of the dialyzer, and the control and computing unit is configured to regulate a ratio between a quantity of the substituate supplied upstream and a quantity of the substituate supplied downstream, based on the evaluation pair.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An example of embodiment of the present invention will be described in greater detail below by reference to the drawings.

(2) In the figures:

(3) FIG. 1 shows the main components of an extracorporeal blood treatment apparatus according to the present invention in a simplified schematic representation and

(4) FIG. 2 shows a matrix, which assigns a value corresponding to the required change in the substituate rate to each evaluation pair characteristic of the rheological loading of the dialyzer.

DETAILED DESCRIPTION

(5) FIG. 1 shows the main components of the blood treatment apparatus according to the present invention, which is a hemo(dia)filtration apparatus, which comprises a dialyzer (filter) 1 which is divided by a semipermeable membrane 2 into a blood chamber 3 and a dialyzing fluid chamber 4. The inlet of blood chamber 3 is connected to one end of a blood supply line 5, into which a blood pump 6, in particular a roller pump generating pressure pulses, is incorporated, while the outlet of the blood chamber is connected to one end of a blood discharge line 7, into which a drip chamber 8 is incorporated. Blood supply line and blood discharge line 5, 7 form, with blood chamber 3 of the dialyzer, extracorporeal blood circuit 9 of the hemodiafiltration apparatus. Blood supply line and blood discharge line 5, 7 are hose lines of a hose set (disposable) inserted into the hemodiafiltration apparatus.

(6) Dialyzing fluid system 10 of the hemodiafiltration apparatus comprises a device 11 for making available dialyzing fluid, which is connected via the first section of dialyzing fluid supply line 12 to the inlet of first balancing chamber half 35a of a balancing device 35. The second section of dialyzing fluid supply line 12 connects the outlet of first balancing chamber half 35a to the inlet of dialyzing fluid chamber 4. The outlet of dialyzing fluid chamber 4 is connected via the first section of a dialyzing fluid discharge line 13 to the inlet of second balancing chamber half 35b. A dialyzing fluid pump 14 is incorporated into the first section of dialyzing fluid discharge line 13. The outlet of second balancing chamber half 35b is connected via the second section of dialyzing fluid discharge line 13 to a drain 15. An ultrafiltrate line 16, which also leads to drain 15, branches off from dialyzing fluid discharge line 13 upstream of dialyzing fluid pump 14. An ultrafiltration pump 17 is incorporated into ultrafiltrate line 16. In commercially available apparatuses, balancing device 35 comprises two parallel balancing chambers which are operated anti-cyclically. For reasons of simplification, only one balancing chamber is represented here.

(7) During the dialysis treatment, the patient's blood flows through blood chamber 3 and the dialyzing fluid flows through dialyzing fluid chamber 4 of the dialyzer. Balancing device 35 ensures that only as much dialyzing fluid can be supplied via the dialyzing fluid supply line as dialyzing fluid can be discharged via the dialyzing fluid discharge line. A preset quantity of fluid (ultrafiltrate) can be withdrawn from the patient at a preset ultrafiltration rate with ultrafiltration pump 17. Ultrafiltration pump 17 is thus part of a device for removing fluid from the blood flowing in extracorporeal circuit 9 through membrane 2 of dialyzer 1, which is referred to as ultrafiltration device 18.

(8) In order to feed the fluid back to the patient, the hemodiafiltration apparatus comprises a substitution device 19, with which a substitution fluid (substituate) can be fed to the blood that is flowing through arterial branch 20 (pre-dilution) and/or venous branch 21 (post-dilution) of extracorporeal blood circuit 9. Substitution device 19 comprises a device 37 for making available substituate, from which a first substituate line 36, into which a first substituate pump 22 is incorporated, leads to the section of blood supply line 5 between blood pump 6 and blood chamber 3. A second substituate line 23, into which a second substituate pump 24 is incorporated, leads from device 37 for making available substituate to drip chamber 8. If the hemodiafiltration apparatus is to be operated solely with post-dilution or pre-dilution, the one or other substituate pump together with the respective substituate line can be dispensed with.

(9) Moreover, the hemodiafiltration apparatus comprises a central control and computing unit 25, which is connected via control lines 6′, 14′, 17′, 22′, 24′ to blood pump 6, dialyzing fluid pump 14, ultrafiltration pump 17 and first and second substituate pump 22, 24.

(10) The extracorporeal blood treatment apparatus comprises a device 26 for regulating the supply of the substituate, which is represented in dashed lines in FIG. 1. Device 26 for regulating the supply of substituate is represented in FIG. 1 as a separate device. It can however also be a component of central control and computing unit 25. Device 26 for regulating the supply of substituate is connected to central control and computing unit 25 via a data line 26′, so that the regulating device can exchange data with the control unit, and in particular can correspondingly control substituate pumps 22, 24 in order to adjust substituate rate Q.

(11) Device 26 for regulating the supply of substituate comprises means 27 for determining the rheological loading of the dialyzer and means 28 for regulating the substituate rate.

(12) Means 27 for determining the rheological loading of the dialyzer in turn comprises means 29 for determining the transmembrane pressure on the dialyzer or a variable correlating with the transmembrane pressure and means 30 for determining the flow resistance of the dialyzer or a variable correlating with the flow resistance. The flow resistance of the dialyzer is to be understood as the longitudinal flow resistance along the hollow fibers of semipermeable membrane 2 of dialyzer 1 on the blood side.

(13) Means 29 for determining the transmembrane pressure (TMP) can be designed in different ways. The measuring device described in EP 0 212 127 A1, for example, can be used to determine the transmembrane pressure. In the present example of embodiment, means 27 for determining the transmembrane pressure comprise a first pressure sensor 31 disposed in dialyzing fluid supply line 12 upstream of dialyzing fluid chamber 4 of dialyzer 1, a second pressure sensor 32 disposed in dialyzing fluid discharge line 16 downstream of the dialyzing fluid chamber of the dialyzer and a third pressure sensor 33 disposed in blood return line 21 downstream of chamber 3 of dialyzer 1. Pressure sensors 31, 32, 33 are connected via data lines 31′, 32′, 33′ to means 29 for determining the transmembrane pressure. Pressure P.sub.1 upstream and pressure P.sub.2 downstream of the dialyzing fluid chamber are measured in dialyzing fluid system 10 by pressure sensors 31 and 32 and pressure P.sub.3 downstream of the blood chamber is measured in extracorporeal blood circuit 9 by pressure sensor 33.

(14) Means 29 for determining transmembrane pressure TMP comprise a suitable computing unit, which calculates the transmembrane pressure according to the following equation:

(15) $TMP=P_3-\frac{P_1+P_2}{2}$

(16) The ascertained value for transmembrane pressure TMP is evaluated as follows. In order to evaluate transmembrane pressure TMP, a first evaluation quantity HEMO Priority is calculated according to the following equation from the measured value for transmembrane pressure TMP and a preset lower limiting value for the transmembrane pressure TMP.sub.LIMIT_LOWER and a preset upper limiting value for the transmembrane pressure TMP.sub.LIMIT_UPPER as well as a preset value range for the transmembrane pressure TMP.sub.LIMIT_RANGE. Parameters TMP.sub.LIMIT_LOWER, TMP.sub.LIMIT_UPPER and TMP.sub.LIMIT_RANGE are ascertained empirically.
HEMO_Priority=((TMP−TMP.sub.LIMIT_LOWER)/TMP.sub.LIMIT_RANGE)×100% wherein TMP.sub.LIMIT_RANGE=TMP.sub.LIMIT_UPPER−TMP.sub.LIMIT_LOWER

(17) Apart from transmembrane pressure TMP, the flow resistance of the dialyzer is ascertained in order to determine the rheological loading of dialyzer 1.

(18) Means 30 for determining the flow resistance comprise means for measuring pressure pulses, which are propagated in the longitudinal direction over the hollow fibers of the semipermeable membrane of the dialyzer on the blood side. The pressure pulses are generated by blood pump 6, which is an occluding hose pump, in particular a roller pump. In the present example of embodiment, pressure sensor 33 disposed downstream of blood chamber 3 in blood return line 21 is used to measure the pressure pulses generated by blood pump 6. A second data line 33″ therefore leads from pressure sensor 33 to means 30 for determining the flow resistance. In order to determine the flow resistance, the pressure signal measured by pressure sensor 33 is split up spectrally into a fundamental component G.sub.0 and first and second harmonics H.sub.1 and H.sub.2, since the attenuation of the pressure pulses along the hollow fibers is connected with the ratio of the amplitudes of the spectral components of first and second harmonics H.sub.1 and H.sub.2 to fundamental component G.sub.0. The theoretical relationship is described in WO 2008/135193 A1.

(19) In order to regulate the substituate flow, the flow resistance is also evaluated as follows. A second evaluation quantity BLKD_priority is calculated from fundamental component G.sub.0 and first and second harmonics H.sub.1 and H.sub.2 as well as empirically established parameters K.sub.1,2, M.sub.1,2 and α according to the following equation

(20) $\mathrm{BLKD\_Priority}=\alpha \times \left(\frac{G_0/H_1-K_1}{2M_1}+\frac{G_0/H_2-K_2}{2M_2}\right)$

(21) The first and second evaluation quantities form an evaluation pair (Hemo_Priority/BLKD_Priority), which is characteristic of the rheological loading of the dialyzer.

(22) The frequency of the fundamental component of the pressure pulses results from the control of blood pump 6. The frequencies of the first and second harmonics of the fundamental component are therefore also known. The splitting-up of the continuous pressure signal into its spectral components preferably takes place with a Fourier transform, particularly preferably by digitalising the measured values of pressure sensor 33 with a discrete Fourier transform, which is carried out in a suitable computing unit.

(23) The advantage of the analysis of the pressure pulses for the determination of the flow resistance lies in the fact that only one sensor downstream of the dialyzer is required. A sensor upstream of the dialyzer, on the other hand, is not required. It is however also possible to determine the flow resistance or a variable correlating with the flow resistance using measurements with four pressure sensors upstream and downstream of the dialyzer on the blood side and dialyzing fluid side. It is also possible to determine approximately the flow resistance or a variable correlating with the flow resistance using a measurement with two pressure sensors downstream of the dialyzer on the blood side and dialyzing fluid side, in that the pressures upstream of the dialyzer on the blood side and dialyzing fluid side are estimated on the basis of operational parameters.

(24) Since the rheological loading of the dialyzer is determined both on the basis of the transmembrane pressure and the flow resistance, the measurement of the transmembrane pressure is sufficient with only two or three pressure sensors instead of the known measurement with four pressure sensors, although the two-point and the three-point measurement of the transmembrane pressure have not always proved to be reliable in practice, since an unsteady behaviour in the region of particularly high transmembrane pressures can occur with the two-point and the three-point measurement.

(25) In the present example of embodiment, the transmembrane pressure and the flow resistance are evaluated in such a way that the evaluation quantities are scaled within an evaluation scale of 0 to 100%. The rheological loading of the dialyzer can be completely described as a point in a two-dimensional coordinate system. The regulation of the substituate rate is based on keeping the rheological loading inside a target area of the matrix. The regulation takes place irrespective of whether a post-dilution or pre-dilution is present.

(26) FIG. 2 shows the two-dimensional matrix, which assigns to each evaluation pair (priority pair) a value which corresponds to the required change in the substituate rate. Consequently, a specific value for the amount of the change in the preset substituate rate is assigned to each value pair stored in the matrix. Inside the matrix there is a nominal line (value range) which connects the evaluation pairs to one another which correspond to the desired dialyzer loading. The nominal line is a line which consists mathematically of the connection in a line running linearly to the priorities and a circular line running around the priority pair (0,0). If the priority pair lies on the nominal line, the substituate rate remains unchanged. The nominal line (value range) is marked in FIG. 2 as an unshaded area. The amount of the change in the substituate rate is represented in FIG. 2 by the density of the shading. The scale on the right in FIG. 2 assigns corresponding changes in the substituate rate to the shaded areas in the coordinate system on the left. The control target here is the unshaded area (0%), which is equivalent to an unchanged substituate dose.

(27) Required substituate rate change α is determined from the matrix in device 26 for regulating the supply of substituate. The substituate rate to be newly adjusted Q.sub.sub, new is calculated as follows:
Q.sub.sub,new=Q.sub.sub,old(1+α)

(28) A specific ultrafiltration rate, which is set using ultrafiltration device 18, is preset for the extracorporeal blood treatment. Furthermore, a selection is made as to whether fluid is to be supplied to or removed from the patient or whether fluid is neither to be supplied to nor removed from the patient. If, for example, fluid is to be removed from the patient, central control and computing unit 25 presets a specific substituate rate. This substituate rate is then rated in such a way that less substituate is supplied to the extracorporeal blood circuit than fluid is removed via membrane 2 of dialyzer 1 by ultrafiltration device 18. This preset substituate rate is increased or reduced by device 26 in order to regulate the supply of substituate according to the method described above. The extracorporeal blood treatment is thus carried out under optimum conditions for the dialyzer.

(29) The regulation of the substituate addition provides not only for a change in the substituate rate, but also a distribution of the supply of substituate upstream and downstream of the dialyzer (pre-dilution and post-dilution). In the case of the supply of substituate both upstream and downstream of the dialyzer, the total dilution quantity for post- and pre-dilution is changed according to the matrix. As a determining parameter for a change instruction for the total dilution quantity, use is made here of the distance of the value pair in the coordinate system characteristic of the rheological loading of the dialyzer from the coordinate origin (0,0) and the angle between the imaginary line, which runs through the coordinate origin (0,0) and the characteristic evaluation pair, and the X-axis or alternatively the Y-axis. Device 26 for regulating the supply of substituate, together with central control and computing unit 25, then sets the flow rates of substituate pumps 22 and 24 in accordance with the ascertained distance and angle.