Flow path condition detection method and blood purification device

Abstract

To provide a channel state detection method and a blood purification device which can estimate a flow rate even in a circuit having no flow meter, as well as, allow a user to grasp an abnormality occurring in the circuit.SOLUTION: A method which estimates a state of a blood-flowing channel in a blood purification device 1 comprises: measuring a downstream side pressure Pb by a downstream side pressure measurement unit 13b provided between a dialyzer 20 and a blood return unit 3; and calculating, by a control unit 30, an estimated blood return flow rate Fv flowing in the blood return unit 3, based on a secondary correlation equation between the downstream side pressure Pb stored in the control unit 30 and a setting flow rate Fs of a roller pump 15 and the downstream side pressure Pb measured by the downstream side pressure measurement unit 13b.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a flow path state detection method and a blood purification device, and more particularly to a flow path state detection method for detecting abnormalities in circuits provided in a dialysis device for performing dialysis or a blood purification device for performing blood exchange, and to a blood purification device having a function for detecting such circuit abnormalities. [Background technology]

[0002] A dialysis device has a circulation circuit (hereinafter sometimes referred to as a dialysis circuit) that extracts blood from the human body, dialyzes the blood in a dialyzer, and returns the dialyzed blood to the human body. The dialysis circuit is equipped with a blood flow pump that pumps the blood.

[0003] However, under normal conditions of treatment using a dialysis machine, abnormalities in the flow path of the circulation circuit may occur. If such abnormalities occur, the desired dialysis efficiency may not be achieved and there is a possibility that they may have adverse effects on the patient, so it is necessary to quickly discover and deal with the abnormality in the flow path.

[0004] Patent Document 1 discloses a blood purification device having an extracorporeal circulation circuit using a centrifugal pump, and discloses that the flow resistance of blood flowing through a flow path can be calculated using the flow rate measured by a flow meter installed in the circuit and the rotation speed of the centrifugal pump, and that blood flow abnormalities in the extracorporeal circulation circuit can be identified based on this blood flow resistance. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-36934 Summary of the Invention [Problem to be solved by the invention]

[0006] The technology of Patent Document 1 may be applicable to devices that use a centrifugal pump to deliver fluid when a flow meter is installed in the circuit. However, many general dialysis devices do not have a flow meter or use a roller pump to deliver fluid, and the technology of Patent Document 1 cannot be applied to such dialysis devices.

[0007] Furthermore, the technology of Patent Document 1 can detect that an abnormality has occurred in the circuit due to blood flow resistance, but cannot identify the abnormality that has occurred.

[0008] In view of the above circumstances, the present invention aims to provide a flow path condition detection method and a blood purification device that can estimate the flow rate even in a circuit that does not have a flow meter and that can identify abnormalities occurring in the circuit. [Means for solving the problem]

[0009] <Flow path state detection method> The flow path state detection method of the present invention is a method for estimating the state of a flow path through which blood flows in a blood purification device having a blood collection unit that collects blood from a human body, a blood purification unit having a blood purifier that purifies the blood collected by the blood collection unit and a liquid delivery unit that delivers the blood upstream of the blood purifier, a blood return unit that returns the blood purified by the blood purification unit to the human body, and a control unit that controls the operation of the liquid delivery unit of the blood purification unit, characterized in that a downstream pressure measurement unit provided between the blood purifier and the blood return unit measures downstream pressure, and the control unit calculates an estimated return blood flow rate through the blood return unit based on a quadratic correlation equation between the downstream pressure and the set flow rate of the liquid delivery unit that is stored in the control unit and the downstream pressure measured by the downstream pressure measurement unit. <Blood purification device> The blood purification apparatus of the present invention comprises a blood collection unit that collects blood from a human body, a blood purification unit having a blood purifier that purifies the blood collected by the blood collection unit and a liquid delivery unit that delivers the blood, the liquid delivery unit being located upstream of the blood purifier, a blood return unit that returns the blood purified by the blood purification unit to the human body, and a control unit that controls the operation of the liquid delivery unit of the blood purification unit, wherein the blood purification unit has a downstream pressure measurement unit located between the blood purifier and the blood return unit, and the control unit has a function of calculating an estimated return blood flow rate through the blood return unit based on a quadratic correlation equation between the set flow rate and downstream pressure of the liquid delivery unit, which is stored in the control unit, and the downstream pressure measured by the downstream pressure measurement unit. [Effects of the Invention]

[0010] According to the present invention, the blood flow rate (return blood flow rate) flowing through the blood return section can be estimated based on the downstream pressure. Furthermore, it is also possible to estimate an abnormality in the flow path based on the return blood flow rate. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram of a blood purification device 1 of the present embodiment. [Figure 2] FIG. 1 is a schematic diagram of a circuit used in an experiment. [Figure 3] FIG. 10 is a diagram showing the experimental results of a blood purifier flow rate confirmation experiment. [Figure 4] FIG. 10 is a diagram showing the results of an experiment to confirm the return blood flow rate. [Figure 5] FIG. 10 is a diagram showing the results of an experiment to confirm the return blood flow rate. [Figure 6] FIG. 10 shows the results of an experiment to confirm the influence of the vent pressure on the estimated blood purifier flow rate and the estimated blood return flow rate. [Figure 7] FIG. 10 is a diagram showing the experimental results of a test simulating clogging of a dialyzer. [Figure 8] FIG. 10 is a diagram showing the experimental results of a test simulating clogging of the flow path in the blood return section. [Figure 9] FIG. 10 is a diagram showing the experimental results of a confirmation experiment of venting pressure. [Figure 10] FIG. 10 is a diagram showing the results of an experiment conducted to confirm the relationship between the actually measured venting pressure and the estimated venting pressure. DETAILED DESCRIPTION OF THE INVENTION

[0012] Next, an embodiment of the present invention will be described with reference to the drawings. The blood purification device of this embodiment is a device used to purify blood, and is characterized by its ability to accurately estimate the actual flow rate of liquid flowing through the device and to identify circuit abnormalities occurring within the device's flow path.

[0013] The use of the blood purification device of this embodiment is not particularly limited, and it can be used, for example, as a dialysis device for dialyzing blood, a blood purification device for performing plasma exchange, etc. In the following, a case where the blood purification apparatus of this embodiment is used as a dialysis apparatus will be described as a representative example.

[0014] <Blood purification device 1 of this embodiment> Next, the basic configuration of the blood purification device 1 of this embodiment will be described with reference to the drawings. As shown in FIG. 1, the blood purification device 1 of this embodiment includes a blood collection unit 2 that collects blood from a human body, a dialysis unit 10 that dialyzes the blood collected by the blood collection unit 2, a blood return unit 3 that returns the blood dialyzed by the dialysis unit 10 to the human body, and a control unit 30 that controls the operation of the dialysis unit 10. The dialysis unit 10 corresponds to the blood purification unit in the claims.

[0015] <Blood Collection Department 2> 1, the blood collection unit 2 includes a needle 2a for puncturing a person's blood vessel or shunt, and a tube 2b with the needle 2a attached to its tip. The base end of the tube 2b is connected to the suction side of the roller pump 15 of the dialysis unit 10 directly or via another tube or pipe.

[0016] <Dialysis Department 10> As shown in Fig. 1, the dialysis unit 10 is a device in which a roller pump 15 and a dialyzer 20 are connected in series by tubes, piping, etc. (hereinafter, sometimes simply referred to as tubes, etc.). Specifically, in the dialysis unit 10, the discharge side of the roller pump 15 and the inlet side of the dialyzer 20 are connected by tubes, etc. In other words, in the dialysis unit 10, the roller pump 15 and the dialyzer 20 are connected by tubes, etc. so that they are arranged in the order of the roller pump 15 and the dialyzer 20 from the upstream side to the downstream side of the blood to be dialyzed (from left to right in Fig. 1).

[0017] <Roller pump 15> The roller pump 15 is a typical roller pump. For example, the roller pump 15 has a roller pump segment equipped with a tube that forms part of the flow path through which blood flows in the dialysis unit 10, a roller unit around which the tube of the roller pump segment is wound, and a casing that sandwiches the tube between the roller unit and the roller unit. Therefore, when the roller pump 15 is operated, the roller unit rotates and the pair of rollers sequentially crush and smooth the tube, allowing the roller pump 15 to pump blood.

[0018] Although the roller pump 15 corresponds to the fluid sender referred to in the claims, the fluid sender for sending blood provided in the blood purifier is not limited to the roller pump 15, and any known fluid sender can be used. An example of the fluid sender in the blood purification apparatus 1 of this embodiment is a centrifugal pump.

[0019] <Dylyzer 20> The dialyzer 20 is used for general dialysis and has spaces separated by a dialysis membrane. Blood can be dialyzed by passing blood through one space and dialysate through the other. The structure of the dialyzer 20 is not particularly limited, and any structure that has the function of dialyzing blood using dialysate can be used. For example, a dialyzer having a main body with a hollow space and a hollow fiber membrane that functions as a dialysis membrane and is disposed in the hollow space of the main body can be used.

[0020] When the blood purification apparatus 1 of this embodiment is used for purposes other than dialysis, an appropriate device may be used instead of the dialyzer 20. For example, in the case of a blood purification apparatus that performs plasma exchange, a plasma separator may be used instead of the dialyzer 20.

[0021] The dialyzer 20 corresponds to the blood purifier in the claims.

[0022] <Pressure measurement unit 13> The dialysis unit 10 is provided with a pressure measurement unit 13 in addition to the roller pump 15 and the dialyzer 20. Specifically, an upstream pressure measurement unit 13a of the pressure measurement unit 13 that measures the pressure inside the tube is provided in the tube connecting the roller pump 15 and the dialyzer 20. The upstream pressure measurement unit 13a is equipped with a drip chamber that has an air trap function to remove gases mixed in the blood.

[0023] Further, downstream of the dialyzer 20, a downstream pressure measuring section 13b of the pressure measuring unit 13 for measuring the pressure inside the tube etc. is provided. The downstream pressure measuring section 13b is equipped with a drip chamber having an air trap function to remove gases mixed in the blood etc.

[0024] The configurations of the upstream pressure measurement unit 13a and the downstream pressure measurement unit 13b of the pressure measurement unit 13 are not particularly limited, and they do not have to be equipped with a drip chamber as described above. Known pressure gauges capable of measuring the pressure inside a tube or the like can be used as the upstream pressure measurement unit 13a and the downstream pressure measurement unit 13b.

[0025] <Blood return part 3> As shown in Fig. 1, the blood return unit 3 includes a needle 3a that is inserted into a person's blood vessel or shunt, and a tube 3b with the needle 3a attached to its tip. The base end of the tube 3b is connected to the blood return side of the dialyzer 20 in the dialysis unit 10, either directly or via another tube or piping. For example, in Fig. 1, the tube 3b is connected to the blood return side of the dialyzer 20 in the dialysis unit 10 via the downstream pressure measurement unit 13b.

[0026] <Control unit 30> The control unit 30 controls the operation of the roller pump 15 of the dialysis unit 10. The control unit 30 is electrically connected to the measurement units 13a and 13b of the pressure measurement unit 13, and information relating to the measured values ​​measured by the measurement units 13a and 13b of the pressure measurement unit 13 is transmitted to the control unit 30. In other words, the control unit 30 has the function of controlling the operation of the roller pump 15 of the dialysis unit 10 based on information relating to the measured values ​​measured by the measurement units 13a and 13b of the pressure measurement unit 13.

[0027] This control unit 30 has the function of estimating the operating state of the blood purification device 1 of this embodiment based on information regarding the measurement values ​​measured by each measurement unit 13a, 13b of the pressure measurement unit 13, and the function of controlling the operating state of the blood purification device 1 of this embodiment (specifically, the operating state of the roller pump 15 of the dialysis unit 10) based on the estimated operating state.

[0028] The functions of the control unit 30 for estimating the operating state of the blood purification apparatus 1 of this embodiment include a function (blood purifier flow rate estimation function S1) for estimating the blood flow rate through the dialyzer 20 of the dialysis unit 10 (hereinafter, sometimes referred to as blood purifier flow rate) and a function (blood return flow rate estimation function S2) for estimating the blood flow rate through the blood return unit 3 (hereinafter, sometimes referred to as return blood flow rate). The control unit 30 also has a function (flow path state detection function S3) for estimating the flow path state based on the blood purifier flow rate estimated by the blood purifier flow rate estimation function S1 and the return blood flow rate estimated by the return blood flow rate estimation function S2, and a function (depletion blood pressure estimation function S4) for estimating the blood pressure upstream of the roller pump 15 of the dialysis unit 10 (hereinafter, sometimes referred to as depletion blood pressure). These functions will be described later.

[0029] The control unit 30 may have all of the above functions, or may have only one of these functions, or may have only a selected few of the above functions (for example, only the blood purifier flow rate estimation function S1 and the return blood flow rate estimation function S2).

[0030] <Dialysis Work Using the Blood Purification Apparatus 1 of the Present Embodiment> Since the blood purification device 1 of this embodiment has the above-described configuration, dialysis is performed as follows.

[0031] First, before administering the blood purification apparatus 1 of this embodiment to a patient undergoing dialysis, priming of the dialysis unit 10 is performed. For example, the needle 2a is removed from the tip of the tube 2b of the blood collection unit 2, and a device or instrument (such as a bag) that supplies cleaning fluid or dialysate is connected to the tip of the tube 2b. The needle 3a is also removed from the tip of the tube 3b of the blood return unit 3, leaving the tip of the tube 3b of the blood return unit 3 open. In this state, by operating the roller pump 15 while supplying cleaning fluid or dialysate, the cleaning fluid or dialysate can be circulated through the inside of the tubes of the dialysis unit 10, the inside of the dialyzer 20, the tube 2b of the blood collection unit 2, and the tube 3b of the blood return unit 3. Therefore, the blood flowing parts of the blood purification apparatus 1 of this embodiment can be cleaned, and the blood flowing parts of the blood purification apparatus 1 of this embodiment can be filled with cleaning fluid or dialysate.

[0032] Once priming is complete, the roller pump 15 is stopped. Then, the tip of the tube 2b of the blood collection unit 2 and the tip of the tube 3b of the blood return unit 3 are connected to the needle 2a of the blood collection unit 2 and the needle 3a of the blood return unit 3, which have been inserted into the patient's blood vessels and shunt, respectively, and preparation for dialysis is complete (see Figure 1).

[0033] When preparation for dialysis is complete, the set flow rate is set in accordance with the treatment conditions and the roller pump 15 is operated. Then, blood collected from the patient by the blood collection unit 2 is dialyzed by the dialyzer 20 and returned to the patient through the blood return unit 3, so that dialysis can be performed by the blood purification device 1 of this embodiment.

[0034] The blood purification device 1 of this embodiment does not necessarily have to include the blood collection unit 2 and the blood return unit 3. In other words, the blood purification device 1 of this embodiment may have only the dialysis unit 10. In this case, the blood collection unit 2 and the blood return unit 3 are prepared separately when in use, and then connected to the dialysis unit 10 when performing dialysis.

[0035] The following describes each function of the control unit 30 described above.

[0036] <Blood purifier flow rate estimation function S1> The blood purifier flow rate estimation function S1 is a function that calculates the blood flow rate (estimated blood purifier flow rate Ff) that actually flows through the blood purification device 1 of this embodiment when the roller pump 15 is operated. Specifically, the blood purifier flow rate estimation function S1 calculates a filter pressure difference Pd, which is the differential pressure between the upstream pressure Pa measured by the upstream pressure measurement unit 13a and the downstream pressure Pb measured by the downstream pressure measurement unit 13b, and calculates the estimated blood purifier flow rate Ff based on this filter pressure difference Pd and a linear correlation equation between the filter pressure difference Pd and the blood flow rate Fa in the blood purifier, which is stored in the control unit 30.

[0037] The linear correlation equation used is determined as follows. First, for the blood purification device 1 of this embodiment, the roller pump 15 is operated to flow blood while measuring the blood removal flow rate Fa (see FIG. 2), and the range of flow rates where the set flow rate Fs of the roller pump 15 matches the blood removal flow rate Fa (hereinafter, sometimes referred to as the matching range) is determined (see FIG. 3(A)).

[0038] Once the coincidence range is determined, the upstream pressure Pa and downstream pressure Pb are measured while changing the set flow rate Fs of the roller pump 15. This makes it possible to obtain a relational expression between the filter pressure difference Pd and the set flow rate Fs of the roller pump 15. As shown in Figure 3(B) , within the coincidence range, a linear correlation is obtained between the filter pressure difference Pd and the set flow rate Fs of the roller pump 15, so the relational expression between the filter pressure difference Pd and the set flow rate Fs of the roller pump 15 becomes a linear correlation expression.

[0039] If such a linear correlation equation is stored in the control unit 30, the estimated blood purifier flow rate Ff can be calculated by measuring the upstream pressure Pa and downstream pressure Pb and calculating the filter pressure difference Pd. The estimated blood purifier flow rate Ff can be calculated simply by calculating the filter pressure difference Pd and applying it to the linear correlation equation, so if the upstream pressure Pa and downstream pressure Pb are continuously measured, the estimated blood purifier flow rate Ff can be continuously calculated in real time.

[0040] <Return blood flow estimation function S2> The blood return flow rate estimation function S2 is a function for calculating the blood flow rate (estimated blood return flow rate Fv) that is actually returned to the human body from the blood return section 3. Specifically, the blood return flow rate estimation function S2 calculates the estimated blood return flow rate Fv based on the downstream pressure Pb measured by the downstream pressure measurement section 13b and a nonlinear regression equation between the downstream pressure Pb and the estimated blood purifier flow rate Ff stored in the control section 30.

[0041] The nonlinear regression equation used is determined as follows: First, in the blood purification device 1 of this embodiment, similar to the blood purifier flow rate estimation function S1, the roller pump 15 is operated to flow blood while measuring the blood removal flow rate Fa, and the range of flow rates (sometimes called the coincidence range) in which the set flow rate Fs of the roller pump 15 matches the blood removal flow rate Fa is determined (see Figure 4(A)).

[0042] Once the coincidence range is determined, the upstream pressure Pa and downstream pressure Pb are measured while changing the set flow rate Fs of the roller pump 15, and the estimated blood purifier flow rate Ff is calculated using the blood purifier flow rate estimation function S1 described above. Then, a relational expression between the downstream pressure Pb and the estimated blood purifier flow rate Ff can be obtained. As shown in Figure 4(B), within the coincidence range, a correlation expressed by a nonlinear regression equation is obtained between the downstream pressure Pb and the estimated blood purifier flow rate Ff.

[0043] Here, if there is no blockage or the like in the flow path of the blood return section 3, the blood removal flow rate Fa (in other words, the blood flow rate flowing through the dialysis section 20) and the blood flow rate flowing through the blood return section 3 should be the same, so by using a nonlinear regression equation that shows the relationship between the downstream pressure Pb and the estimated blood purifier flow rate Ff, the estimated blood return flow rate Fv can be calculated from the downstream pressure Pb.

[0044] Therefore, if a nonlinear regression equation showing the relationship between the downstream pressure Pb and the estimated blood purifier flow rate Ff, in other words, a nonlinear regression equation showing the relationship between the downstream pressure Pb and the estimated blood return flow rate Fv, is stored in the control unit 30, the estimated blood return flow rate Fv can be estimated by measuring the downstream pressure Pb. Furthermore, since all that is required is to measure the downstream pressure Pb and apply it to the nonlinear regression equation, the estimated blood return flow rate Fv can be continuously estimated in real time by continuously measuring the downstream pressure measuring unit 13b.

[0045] <Another example of the blood return flow rate estimation function S2> In the above example, the return blood flow rate estimation function S2 was described as calculating the estimated return blood flow rate Fv based on the downstream pressure Pb and a nonlinear regression equation between the downstream pressure Pb and the estimated blood purifier flow rate Ff stored in the control unit 30.

[0046] The estimated blood return flow rate Fv can also be calculated based on a nonlinear regression equation between the downstream pressure Pb and the set flow rate Fs of the roller pump 15. In other words, it is possible to calculate the estimated blood return flow rate Fv even if the blood purification device 1 or the dialysis unit 10 does not have the upstream pressure measuring unit 13a.

[0047] In this case, the nonlinear regression equation used is determined as follows: First, for the blood purification apparatus 1 of this embodiment, an aqueous liquid (such as a dialysis fluid or a cleaning solution) and a blood liquid (such as bovine blood or the blood to be actually dialyzed) are flowed through the blood purification apparatus 1 by operating the roller pump 15, and a correlation diagram is created between the set flow rate Fs of the roller pump 15 and the downstream pressure Pb (sometimes called PbW for the aqueous system and PbB for the blood system). A correlation expressed by a quadratic correlation equation is obtained between the set flow rate Fs of the roller pump 15 and the downstream pressure Pb (see FIG. 5(A)).

[0048] Next, a correlation diagram is created between the water system downstream pressure PbW and the blood system downstream pressure PbB measured under the same conditions for the set flow rate Fs of the roller pump 15. As a result, a correlation expressed by a linear correlation equation is obtained between the water system downstream pressure PbW and the blood system downstream pressure PbB (see Figure 5(B)).

[0049] Once the above-mentioned quadratic correlation equation and linear correlation equation are obtained, the blood system downstream pressure PbB, i.e., the downstream pressure Pb measured during actual dialysis, can be input into the linear correlation equation between the water system downstream pressure PbW and the blood system downstream pressure PbB to convert the blood system downstream pressure PbB to the water system downstream pressure PbW. Then, by inputting the converted value of the water system downstream pressure PbW into the quadratic correlation equation between the set flow rate Fs of the roller pump 15 and the water system downstream pressure PbW, the estimated blood return flow rate Fv can be calculated.

[0050] Therefore, if the first-order correlation equation between the water system downstream pressure PbW and the blood system downstream pressure PbB and the second-order correlation equation between the set flow rate Fs of the roller pump 15 and the water system downstream pressure PbW are stored in the control unit 30, the estimated blood return flow rate Fv can be calculated even when only the downstream pressure Pb is measured. Furthermore, since the downstream pressure Pb is simply measured and applied to the nonlinear regression equation, the estimated blood return flow rate Fv can be continuously estimated in real time by continuously measuring the downstream pressure measuring unit 13b.

[0051] The second-order correlation equation between the set flow rate Fs of the roller pump 15 and each downstream pressure (PbW and PbB), and the first-order correlation equation between the aqueous system downstream pressure PbW and the blood system downstream pressure PbB may be calculated by the control unit 30 using the aqueous system downstream pressure PbW and the blood system downstream pressure PbB measured during the priming operation and the subsequent dialysis operation, or may be obtained in advance by a preliminary experiment or the like.

[0052] In the above example, the blood system downstream pressure PbB is converted to the water system downstream pressure PbW, and the converted water system downstream pressure PbW is input into a quadratic correlation equation between the set flow rate Fs of the roller pump 15 and the water system downstream pressure PbW to calculate the estimated blood return flow rate Fv. However, the blood system downstream pressure PbB may also be directly input into a quadratic correlation equation between the set flow rate Fs of the roller pump 15 and the blood system downstream pressure PbB to calculate the estimated blood return flow rate Fv.

[0053] <Flow path status detection function S3> The flow path state detection function S3 is a function that determines abnormalities occurring in the dialyzer 20 of the dialysis unit 10 and the flow path (tube 3b, etc.) of the blood return unit 3 based on the estimated blood purifier flow rate Ff and estimated blood return flow rate Fv calculated by the blood purifier flow rate estimation function S1 and blood return flow rate estimation function S2. Specifically, the flow path state detection function S3 detects abnormalities occurring in the dialyzer 20 of the dialysis unit 10 and the flow path (tube 3b, etc.) of the blood return unit 3 based on time fluctuations of the estimated blood purifier flow rate Ff and estimated blood return flow rate Fv calculated by the blood purifier flow rate estimation function S1 and blood return flow rate estimation function S2 in real time.

[0054] The flow path state detection function S3 calculates the blood flow ratio (Ff / Fv) between the estimated blood purifier flow rate Ff and the estimated blood return flow rate Fv at the same timing. If there is no abnormality in the dialyzer 20 of the dialysis unit 10 or the flow path of the blood return unit 3, the estimated blood purifier flow rate Ff and the estimated blood return flow rate Fv will be the same flow rate, and the blood flow ratio will be 1 (see part X in Figure 7).

[0055] On the other hand, if a clog or the like occurs in the dialyzer 20 of the dialysis unit 10, the upstream pressure Pa increases, which increases the filter pressure difference Pd, and therefore the estimated blood purifier flow rate Ff increases. On the other hand, the downstream pressure Pb does not change, so the estimated blood return flow rate Fv does not change. Therefore, the blood flow rate ratio becomes greater than 1 (see part Y in Figure 7). In other words, when the time variation of the blood flow rate ratio increases beyond 1, it can be determined that a clog or the like has occurred in the dialyzer 20 of the dialysis unit 10 at that timing.

[0056] Furthermore, if a blockage or the like occurs in the flow path of the blood return section 3, the downstream pressure Pb increases, and the estimated blood return flow rate Fv increases. On the other hand, if there is no blockage or the like in the dialyzer 20 of the dialysis section 10, the upstream pressure Pa increases by the same amount as the downstream pressure Pb increases, so the filter pressure difference Pd does not change and the estimated blood purifier flow rate Ff does not change. In other words, the estimated blood purifier flow rate Ff does not change but the estimated blood return flow rate Fv increases, so the blood flow rate ratio becomes smaller than 1 (see part Z in Figure 8). In other words, if the blood flow rate ratio decreases below 1 with time, it can be determined that a blockage or the like has occurred in the flow path of the blood return section 3 at that timing.

[0057] As described above, by calculating the blood flow ratio (Ff / Fv) between the estimated blood purifier flow rate Ff and the estimated blood return flow rate Fv at the same timing and checking its time variation, the control unit 30 can check for abnormalities occurring in the dialyzer 20 of the dialysis unit 10 or the flow path of the blood return unit 3, and can also determine where the abnormality is occurring (i.e., whether it is the dialyzer 20 of the dialysis unit 10 or the flow path of the blood return unit 3).

[0058] Furthermore, since the time variation curve has a positive or negative peak at the timing when an abnormality occurs, it is possible to confirm that an abnormality had occurred even after the abnormality has been resolved. Therefore, by providing the flow path condition detection function S3, it is possible to identify the cause of the abnormality and take action before a situation arises that would cause the device to stop operating.

[0059] In the above example, an abnormality is determined based on the time variation curve of the blood flow ratio (Ff / Fv). However, if the abnormality is limited to the dialyzer 20 of the dialysis unit 10, it is also possible to determine the abnormality based solely on the time variation curve of the estimated blood purifier flow rate Ff. In other words, it is also possible to determine that a blockage or the like has occurred in the dialyzer 20 of the dialysis unit 10 when the estimated blood purifier flow rate Ff increases above 1. Furthermore, if the abnormality is limited to the flow path of the blood return unit 3, it is also possible to determine the abnormality based solely on the time variation curve of the estimated blood return flow rate Fv. In other words, it is also possible to determine that a blockage or the like has occurred in the estimated blood return flow rate Fv when the estimated blood return flow rate Fv increases. However, using the time variation curve of the blood flow ratio (Ff / Fv) makes it less susceptible to fluctuations in flow resistance due to changes in blood viscosity, etc. The estimated blood purifier flow rate Ff and the estimated blood return flow rate Fv fluctuate due to flow resistance caused by changes in blood viscosity, etc., but the blood flow rate ratio (Ff / Fv), which is the ratio between the two, eliminates (or reduces) the effect of flow resistance on the time fluctuations, thereby improving the accuracy of detecting blockages in the dialyzer 20 of the dialysis unit 10 and the flow path of the blood return unit 3.

[0060] In the time variation curves of the estimated blood purifier flow rate Ff, the estimated blood return flow rate Fv, and the blood flow ratio (Ff / Fv), the flow rate and ratio may increase from a nearly constant flow rate or a blood flow ratio (Ff / Fv) of 1, or may continuously increase or decrease. In this case, when the flow rate and ratio are continuously increasing or decreasing, the "time of increase" and "time of decrease" refer to the time when the slope changes from the previous rate of increase or decrease (i.e., the slope of the time variation curve (average slope over a certain period of time)). For example, when the flow rate or ratio is gradually increasing (decreasing), even if the flow rate or ratio increases or decreases, if the increase or decrease follows the previous slope, it is not considered an "increase" or "decrease." Instead, the "time of increase" or "decrease" is considered to be the time when the slope of the time variation curve becomes larger than the previous slope or the slope becomes the opposite of the previous slope.

[0061] <Ventilator blood pressure estimation function S4> The venting pressure estimation function S4 is a function that calculates the upstream pressure (estimated venting pressure Ps) of the roller pump 15. Specifically, the venting pressure estimation function S4 calculates an estimated blood flow ratio (Ff / Fs) between the estimated blood purifier flow rate Ff calculated by the blood purifier flow rate estimation function S1 and the set flow rate Fs of the roller pump 15, and calculates the estimated venting pressure Ps based on this estimated blood flow ratio (Ff / Fs) and the relational expression between the estimated blood flow ratio (Ff / Fs) and the venting pressure Pg stored in the control unit 30.

[0062] The relational expression between the estimated blood flow ratio (Ff / Fs) and the dialysis blood pressure Pg is calculated as follows:

[0063] First, the upstream pressure Pa and downstream pressure Pb are measured while changing the set flow rate of the roller pump 15. At the same time, the vent pressure Pg is measured upstream of the roller pump 15. This makes it possible to obtain a relational expression between the estimated blood flow ratio (Ff / Fs) and the vent pressure Pg. As shown in Figure 9(A), a correlation expressed by a polynomial is obtained between the estimated blood flow ratio (Ff / Fs) and the vent pressure Pg.

[0064] If a polynomial that expresses the correlation between the estimated blood flow ratio (Ff / Fs) and the venting blood pressure Pg is stored in the control unit 30, the estimated venting blood pressure Ps can be calculated by calculating the estimated blood flow ratio (Ff / Fs), which is the ratio of the estimated blood purifier flow rate Ff obtained by measuring the upstream pressure Pa and the downstream pressure Pb to the set flow rate Fs of the roller pump 15 instructed by the control unit 30. Then, since the estimated blood flow ratio (Ff / Fs) is simply calculated and applied to the polynomial, the estimated venting blood pressure Ps can be continuously calculated in real time by continuously measuring the upstream pressure Pa and the downstream pressure Pb.

[0065] During dialysis, if the needle 2a of the blood collection unit 2 shifts position and the tip of the puncture needle comes into contact with the blood vessel wall, the dialysis pressure may drop. An abnormal drop in dialysis pressure may also occur if the wrong puncture needle is selected or the shunt flow rate drops. This can lead to a decrease in dialysis efficiency or hemolysis, so immediate action must be taken to ensure that the dialysis pressure is appropriate.

[0066] The blood purification device 1 of this embodiment has a venting blood pressure estimation function S4, and as described above, the estimated venting blood pressure Ps can be continuously grasped in real time, which has the advantage that the cause of the venting blood pressure can be quickly grasped and an abnormal venting blood pressure condition can be resolved.

[0067] The correlation equation between the estimated blood flow ratio (Ff / Fs) and the depletion pressure Pg may be determined by a preliminary test using the blood purification apparatus 1 of this embodiment, or may be calculated based on data obtained during the priming procedure when actually performing dialysis using the blood purification apparatus 1 of this embodiment. That is, a pressure gauge for measuring the depletion pressure Pg may be provided in the flow path upstream of the roller pump 15 (see FIG. 2), and during the priming procedure, the control unit 30 may simultaneously measure the upstream pressure Pa, the downstream pressure Pb, and the depletion pressure Pg while changing the set flow rate Fs of the roller pump 15, and calculate the above-mentioned correlation equation using the results and the measured values ​​of the set flow rate Fs of the roller pump 15, the upstream pressure Pa, the downstream pressure Pb, and the depletion pressure Pg during the dialysis procedure after the priming procedure.

[0068] <Other methods of using the blood purification device 1 of this embodiment> The blood purification device of this embodiment can be used not only in cases where blood is collected from a human body, purified, and returned to the human body, as in dialysis as described above, but also in cases where blood has already been collected or separated from the human body and purified. In this case, the blood collection unit need only be capable of drawing blood and does not necessarily have to be equipped with a needle. Similarly, the blood return unit need only be capable of supplying blood to a container or the like and does not necessarily have to be equipped with a needle. [Example]

[0069] It was confirmed that the method of the present invention can appropriately estimate the blood purifier flow rate, return blood flow rate, and withdrawal blood pressure, and that the calculated blood purifier flow rate and return blood flow rate can be used to determine abnormalities in the circulation circuit of the dialysis unit or the flow path of the return blood unit.

[0070] The experiment was performed using the circuit shown in Figure 2. The circuit consisted of a roller pump (Nikkiso: DCS-72) and a dialyzer (Asahi Kasei Medical: APS-15SA) connected in series via a tube (inner diameter 6.6 mm). Dialysis needles (Medicit Co.: Happy Cass; effective length 33 mm, with side holes, outer diameter 16G / inner diameter 18G) were attached to both ends of the tube. The tube was also equipped with an ultrasonic flowmeter (Transonic: model HT-310) to measure blood flow upstream of the roller pump, and a pressure gauge (Nagano Keiki: KH15-L63PWR) to measure the pressure upstream and downstream of the dialyzer and the pressure upstream of the roller pump.

[0071] For this circuit, the tip of the dialysis needle was immersed in bovine blood (hematocrit value 30, 40%, 36.5 degrees) and the roller pump was operated to measure the flow rate of bovine blood actually flowing through the circuit, the upstream and downstream pressures of the dialyzer, and the upstream pressure of the roller pump (equivalent to the dialysis blood pressure).

[0072] <Blood purifier flow rate verification experiment> First, it was confirmed that the flow rate of a blood purifier can be estimated from the filter pressure difference by the method of the present invention.

[0073] As a preliminary experiment, the range of flow rates where the set flow rate Fs of the roller pump and the blood removal flow rate Fa matched was confirmed by operating the roller pump while measuring the blood flow rate (blood removal flow rate) through the circuit shown in Figure 2. As shown in Figure 3(A), it was confirmed that the set flow rate Fs of the roller pump and the blood removal flow rate Fa matched up to a set flow rate Fs of approximately 300 ml / min.

[0074] Therefore, the filter pressure difference Pd was calculated from the upstream pressure Pa and downstream pressure Pb of the dialyzer, which were measured at the same time, and a correlation diagram was created between the filter pressure difference Pd and the set flow rate Fs of the roller pump (see Figure 3(B)).A linear correlation was observed between the filter pressure difference Pd and the set flow rate Fs of the roller pump up to a set flow rate Fs of 300 ml / min, so a linear correlation equation between the filter pressure difference Pd and the set flow rate Fs of the roller pump was calculated.

[0075] When the estimated blood purifier flow rate Ff calculated based on this linear correlation equation and the filter pressure gradient Pd was compared with the actually measured blood removal flow rate Fa, a very high correlation was confirmed, i.e., the two matched, as long as the blood removal flow rate Fa was in the range of up to 300 ml / min (see Figure 3(C)). Here, when there is no blockage in the flow path of the circuit, the blood removal flow rate Fa and the blood purifier flow rate match, so the above results show that the estimated blood purifier flow rate Ff and the actual blood purifier flow rate essentially match.

[0076] From the above results, it was confirmed that the method of the present invention makes it possible to estimate the actual blood flow rate (blood purifier flow rate) with high accuracy from the filter pressure difference.

[0077] <Experiment to confirm blood return flow rate> Next, it was confirmed that the return blood flow rate can be estimated from the downstream pressure by the method of the present invention.

[0078] <Experiment 1> In Experiment 1, it was confirmed that the return blood flow rate could be estimated using a nonlinear regression equation of the estimated blood purifier flow rate Ff and downstream pressure Pb.

[0079] The estimated blood purifier flow rate Ff was calculated using the same method as in the blood purifier flow rate confirmation experiment. A correlation diagram between the estimated blood purifier flow rate Ff and the downstream pressure Pb was then created (see Figure 4(B)). A nonlinear regression equation between the estimated blood purifier flow rate Ff and the downstream pressure Pb was successfully created in the range where the roller pump set flow rate Fs was up to 300 ml / min.

[0080] When the estimated blood return flow rate Fv calculated based on this nonlinear regression equation and the downstream pressure Pb was compared with the actually measured blood removal flow rate Fa, a very high correlation was confirmed, i.e., the two matched, as long as the blood removal flow rate Fa was in the range of up to 300 ml / min (see Figure 4(C)). Here, when there is no clogging in the flow path of the circuit, the blood removal flow rate Fa and the blood return flow rate match, so the above results show that the estimated blood return flow rate Fv and the actual blood return flow rate essentially match.

[0081] From the above results, it was confirmed that the method of the present invention can estimate the return blood flow rate with high accuracy using the downstream pressure by using a nonlinear regression equation of the estimated blood purifier flow rate Ff and the downstream pressure.

[0082] <Experiment 2> In experiment 2, it was confirmed that the blood return flow rate could be estimated using a nonlinear regression equation of the roller pump's set flow rate Fs and downstream pressure Pb.

[0083] First, a correlation diagram was created using water between the roller pump's set flow rate Fs and downstream pressure Pb (water system downstream pressure PbW), and a quadratic correlation equation between the roller pump's set flow rate Fs and the water system downstream pressure PbW was created (see Figure 5(A)). Similarly, a correlation diagram was created using bovine blood between the roller pump's set flow rate Fs and downstream pressure Pb (blood system downstream pressure PbB), and a quadratic correlation equation between the roller pump's set flow rate Fs and the blood system downstream pressure PbB was created (see Figure 5(A)).

[0084] Next, a correlation diagram was created between the water system downstream pressure PbW and the blood system downstream pressure PbB, measured under the same conditions with the set flow rate Fs of the roller pump 15. A linear correlation equation between the water system downstream pressure PbW and the blood system downstream pressure PbB was then created (see Figure 5(B)).

[0085] The estimated blood return flow rate Fv calculated based on the above-mentioned quadratic correlation equation and linear correlation equation was compared with the actually measured blood removal flow rate Fa. Specifically, the blood system downstream pressure PbB was input into a linear correlation equation between the water system downstream pressure PbW and the blood system downstream pressure PbB to convert the blood system downstream pressure PbB to the water system downstream pressure PbW. This converted water system downstream pressure PbW was then input into a quadratic correlation equation between the set flow rate Fs of the roller pump 15 and the water system downstream pressure PbW to calculate the estimated blood return flow rate Fv. A very high correlation was confirmed between the calculated estimated blood return flow rate Fv and the blood removal flow rate Fa, i.e., they were consistent (see Figure 5(C)). Here, when there is no clogging in the circuit flow path, the blood removal flow rate Fa and the blood return flow rate are consistent, so the above results indicate that the estimated blood return flow rate Fv and the actual blood return flow rate are substantially consistent.

[0086] From the above results, it was confirmed that, according to the method of the present invention, by using a linear correlation equation between the water system downstream pressure PbW and the blood system downstream pressure PbB and a quadratic correlation equation between the set flow rate Fs of the roller pump 15 and the water system downstream pressure PbW, the blood return flow rate can be estimated with high accuracy from the downstream pressure alone.

[0087] <Confirmation experiment for detecting flow path condition> Next, we confirmed that the method of the present invention can estimate circuit abnormalities using the estimated blood purifier flow rate and estimated blood return flow rate. The estimated blood purifier flow rate and estimated blood return flow rate were determined using the same methods as those used in the above-mentioned blood purifier flow rate confirmation experiment and blood return flow rate confirmation experiment.

[0088] In the experiment, we first confirmed whether the influence of the vent pressure Pg on the estimated blood purifier flow rate Ff and the estimated blood return flow rate Fv was confirmed. The vent pressure Pg state was simulated by blocking the tubing upstream of the roller pump (see Figure 2). As shown in Figure 6, even when the vent pressure was changed and the operating state of the roller pump was changed, the fluctuations in the measured vent flow rate Fa and the fluctuations in the estimated blood purifier flow rate Ff and the estimated blood return flow rate Fv were almost consistent. In other words, it was confirmed that the estimated blood purifier flow rate Ff and the estimated blood return flow rate Fv accurately reflect the decrease in blood flow rate (i.e., the decrease in blood purifier flow rate and the decrease in blood return flow rate) that accompanies a decrease in the vent pressure Pg.

[0089] Next, it was confirmed that clogging of the dialyzer and the blood return flow path can be estimated from the estimated blood purifier flow rate Ff and the estimated blood return flow rate Fv.

[0090] Blockage of the dialyzer was simulated by blocking the tubing between the dialyzer and the pressure gauge measuring the downstream pressure Pb (see Figure 2), and blockage of the blood return flow path was simulated by blocking the tubing downstream of the pressure gauge measuring the downstream pressure Pb (see Figure 2).

[0091] As shown in Figures 7 and 8, at the timing simulating a clogged dialyzer (see part Y in Figure 7), the estimated blood return flow rate Fv does not change, but the estimated blood purifier flow rate Ff has a positive peak. Furthermore, at the timing simulating a clogged blood return flow path (see part Z in Figure 8), the estimated blood purifier flow rate Ff does not change, but the estimated blood return flow rate Fv has a positive peak. This confirms that a clogged dialyzer does not affect the estimated blood return flow rate Fv, and that a clogged blood return flow path does not affect the estimated blood purifier flow rate Ff. Therefore, it was confirmed that the occurrence of a clogged dialyzer or a clogged blood return flow path and the location of the clog can be estimated from the estimated blood purifier flow rate Ff and the estimated blood return flow rate Fv.

[0092] As shown in Figures 7 and 8, when the blood flow ratio (Ff / Fv) between the estimated blood purifier flow rate Ff and the estimated blood return flow rate Fv is calculated, the blood flow ratio (Ff / Fv) has a positive peak at the timing simulating clogging of the dialyzer, and a negative peak at the timing simulating clogging of the blood return flow path, and it can be confirmed that the blood flow ratio is 1 when there is no clogging in either the dialyzer or blood return flow path. In other words, it was confirmed that by calculating the blood flow ratio (Ff / Fv) between the estimated blood purifier flow rate Ff and the estimated blood return flow rate Fv, it is possible to determine the occurrence of clogging in the dialyzer or the blood return flow path and the location of the clogging, even when the set blood flow rate Fs fluctuates.

[0093] From the above results, it was confirmed that the method of the present invention makes it possible to identify blockages in the dialyzer or in the blood return flow path by using the estimated blood purifier flow rate and the estimated blood return flow rate.

[0094] As shown in Figures 6 and 7, the estimated blood purifier flow rate Ff and the estimated blood return flow rate Fv immediately return to their original levels when the blockage in the tube is removed. This confirms that the estimated blood purifier flow rate Ff and the estimated blood return flow rate Fv can accurately determine not only the occurrence of blockages in the dialyzer or the blood return flow path, but also the removal of blockages.

[0095] <Experiment to confirm ventilated blood pressure> Next, we confirmed that the infusion pressure can be estimated using the estimated blood purifier flow rate and the set flow rate of the roller pump by the method of the present invention. The estimated blood purifier flow rate was calculated using the same method as in the experiment to confirm the actual blood flow rate described above.

[0096] In the experiment, the estimated blood flow ratio (Ff / Fs) between the estimated blood purifier flow rate Ff and the set flow rate Fs of the roller pump was calculated. Then, a correlation diagram between the obtained estimated blood flow ratio (Ff / Fs) and the ventilator pressure Pg was created (see Figure 9(A)). A relational equation (polynomial) between the estimated blood flow ratio (Ff / Fs) and the ventilator pressure Pg was created.

[0097] When the estimated dialysis blood pressure Ps calculated based on this relational expression (polynomial) and the estimated blood flow ratio was compared with the actually measured dialysis blood pressure Pg, a high correlation was confirmed (see Figure 9(B)).

[0098] We also varied the vent pressure Pg to confirm whether the above correlation could be obtained regardless of its magnitude. The vent pressure was simulated by blocking the tube upstream of the roller pump (see Figure 2). As shown in Figure 10, when the vent pressure Pg was varied, the measured vent pressure Pg and the estimated vent pressure Ps closely matched within a certain vent pressure Pg range (-150 mmHg to -400 mmHg in Figure 10). However, a discrepancy arose between the two values ​​above -150 mmHg or below -400 mmHg. However, because a change in the vent pressure Pg has almost no effect on the vent flow rate Fa within the range above -150 mmHg, the discrepancy does not affect the operation of the device (i.e., actual dialysis treatment). On the other hand, the discrepancy does not pose a problem in the range below -400 mmHg, which is a range where actual dialysis is not performed (a range where dialysis cannot be performed). That is, it is believed that the method of the present invention can accurately estimate the dialysis pressure in the range of -150 mmHg to -400 mmHg, where it is important to know the dialysis pressure in actual dialysis treatment.

[0099] From the above results, it was confirmed that the method of the present invention can accurately estimate the dialysis blood pressure within the practical range of the dialysis machine. [Industrial Applicability]

[0100] The flow path state detection method of the present invention is suitable as a method for estimating the flow rate of blood flowing through the circuit of a blood purification device and the state of the flow path. [Explanation of symbols]

[0101] 1. Blood purification device 2. Blood Collection Department 2a Needle part 2b tube 3 Blood return department 3a Needle part 3b tube 10 Dialysis Department 13 Pressure measurement section 13a Upstream pressure measurement section 13b Downstream pressure measurement section 15 Roller pump 20 Dialysis machine 30 Control Unit Pa Upstream pressure Pb Downstream pressure PbW Downstream pressure of water system PbB Downstream blood pressure Pd filter pressure gradient Pg dialysis blood pressure Ps Estimated diastolic blood pressure S1 Blood Purifier Flow Rate Estimation Function S2 Return blood flow estimation function S3 Flow path condition detection function S4 Intake blood pressure estimation function Ff Estimated blood purifier flow rate Fa Blood removal flow rate Fs Set flow rate of roller pump 15 Fv Estimated return blood flow

Claims

1. A method for estimating the state of a flow path through which blood flows in a blood purification device having a blood collection unit that collects blood from a human body, a blood purification unit having a blood purifier that purifies the blood collected by the blood collection unit and a blood delivery unit that delivers the blood upstream of the blood purifier, a blood return unit that returns the blood purified by the blood purification unit to the human body, and a control unit that controls the operation of the blood delivery unit of the blood purification unit, comprising: a downstream pressure measuring unit provided between the blood purifier and the blood return unit measures the downstream pressure; The control unit calculates an estimated blood return flow rate through the blood return section based on a quadratic correlation equation between the downstream pressure and the set flow rate of the liquid sender, which is stored in the control unit, and the downstream pressure measured by the downstream pressure measuring unit. A flow path state detection method characterized by:

2. The second-order correlation equation is This is a blood system quadratic correlation equation between the downstream pressure of the blood system obtained using a blood system liquid and the set flow rate of the liquid sender.

2. The method for detecting a flow path state according to claim 1.

3. The second-order correlation equation is an aqueous second-order correlation equation between the aqueous downstream pressure obtained by using an aqueous liquid and the set flow rate of the liquid transporter; The control unit includes: a linear correlation equation between the downstream pressure of the blood system obtained by using a blood-based liquid and the downstream pressure of the water system is stored; The control unit Calculating an aqueous system downstream pressure based on the downstream pressure measured by the downstream pressure measuring unit and the primary correlation equation, and calculating the estimated blood return flow rate based on the calculated aqueous system downstream pressure and the aqueous system secondary correlation equation.

2. The method for detecting a flow path state according to claim 1.

4. The control unit performs a preliminary experiment in a priming operation, The control unit calculates the relational expression based on the results of the preliminary experiment.

4. The method for detecting a flow path state according to claim 1, 2 or 3.

5. The control unit determines that an abnormality has occurred in the flow path of the blood return unit at a timing when the time variation curve of the estimated blood return flow rate calculated by the control unit increases.

5. The flow path state detection method according to claim 1, wherein the flow path state detection method is a flow path state detection method.

6. The liquid feeder is a roller pump.

6. The flow path state detection method according to claim 1, wherein the flow path state detection method is a flow path state detection method.

7. a blood collection unit for collecting blood from a human body; a blood purification unit having a blood purifier that purifies the blood collected by the blood collection unit and a blood delivery unit that delivers the blood and is provided upstream of the blood purifier; a blood return unit that returns the blood purified by the blood purification unit to the human body; a control unit that controls the operation of the fluid pump of the blood purification unit, The blood purification unit includes: a downstream pressure measuring unit provided between the blood purifier and the blood return unit, The control unit The control unit has a function of calculating an estimated blood return flow rate through the blood return section based on a quadratic correlation equation between the set flow rate of the blood sender and the downstream pressure stored in the control unit and the downstream pressure measured by the downstream pressure measuring unit. A blood purification device characterized by:

8. The second-order correlation equation is This is a blood system quadratic correlation equation between the downstream pressure of the blood system obtained using a blood system liquid and the set flow rate of the liquid sender.

8. The blood purification apparatus according to claim 7.

9. The second-order correlation equation is an aqueous second-order correlation equation between the aqueous downstream pressure obtained by using an aqueous liquid and the set flow rate of the liquid transporter; The control unit includes: a linear correlation equation between the downstream pressure of the blood system obtained by using a blood-based liquid and the downstream pressure of the water system is stored; The control unit a function of calculating an aqueous system downstream pressure based on the downstream pressure measured by the downstream pressure measuring unit and the primary correlation equation, and calculating the estimated blood return flow rate based on the calculated aqueous system downstream pressure and the aqueous system secondary correlation equation; 8. The blood purification apparatus according to claim 7.

10. The control unit The control unit has a function of determining that an abnormality has occurred in the flow path of the blood return unit at the timing when the time variation curve of the estimated blood return flow rate calculated by the control unit increases.

10. The blood purification apparatus according to claim 7, 8 or 9.

11. The liquid feeder is a roller pump.

11. The blood purification apparatus according to claim 7, wherein the blood purification system is a blood purification system.

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