Blood purification apparatus

Abstract

The present invention provides a blood purification apparatus capable of controlling a pump using an optimal parameter in a measurement step different from a parameter in a treatment step, and highly accurately calculating the ratio of recirculated blood.　The blood purification apparatus comprises: a control unit 16 that controls a pump on the basis of a predetermined parameter; a characteristic change imparting unit capable of imparting, to the concentration change of blood extracorporeally circulated in a blood circuit 1, a local concentration change in which a characteristic peak is formed; a first detection unit 5a and a second detection unit 5b that detect the local concentration change imparted by the characteristic change imparting unit; and a recirculation detection unit 17 that detects recirculated blood on the basis of detection values from the first detection unit 5a and the second detection unit 5b and calculates the ratio of the recirculated blood. In a measurement step for calculating the ratio of the recirculated blood, the control unit 16 performs control after switching the parameter for driving the pump to a measurement parameter different from a treatment parameter for a treatment step for performing blood purification treatment.

Description

Blood purification device

[0001] The present invention relates to a blood purification device that detects recirculated blood, which is blood returned to a patient from a venous blood circuit and then guided back into an arterial blood circuit.

[0002] In general, in blood purification therapy, such as hemodialysis, a patient's blood is circulated extracorporeally through a blood circuit, and blood purification is performed using a dialyzer. However, when, for example, an arterial puncture needle and a venous puncture needle are inserted into a patient's shunt (a site where an artery and a vein are connected by a surgical procedure) to perform extracorporeal circulation, the purified blood returned to the patient through the venous puncture needle may be recirculated back into the blood circuit through the arterial puncture needle without passing through the patient's organs, resulting in recirculation of blood. When this recirculation occurs, the purified blood must be further circulated extracorporeally, which reduces the amount of blood circulating extracorporeally that needs to be purified, resulting in a problem of reduced blood purification efficiency.

[0003] To detect such recirculated blood, a dialysis machine has been proposed that can detect blood recirculation by driving a water removal pump to give a specific peak to the change in concentration of blood circulating extracorporeally, and using this as a marker, as disclosed in Patent Document 1. According to the dialysis machine disclosed in this document, a sensor that detects blood concentration (a sensor that detects hemoglobin concentration) is disposed in the arterial blood circuit, and blood recirculation during dialysis treatment can be detected by detecting the specific peak with this sensor.

[0004] Special Publication No. 2000-502940

[0005] However, conventional blood purification devices have the following problems when calculating the proportion of recirculated blood to determine the recirculation rate or the patient's shunt flow rate. When detecting local concentration changes that form unique peaks in the first and second detection units, the conditions during the measurement process may be unstable depending on the pump's operating status. Furthermore, the local concentration changes may not be accurately detected due to the influence of pulsation caused by the operation of the pump provided in the blood purification device. Similar problems also exist when calculating the proportion of recirculated blood based on changes in other blood characteristics, such as blood temperature, instead of blood concentration. Here, the blood characteristics are not limited to blood concentration but include general blood characteristics, such as blood temperature.

[0006] The present invention has been made in consideration of the above circumstances, and aims to provide a blood purification device that can control the pump during the measurement process using optimal parameters that differ from those used during the treatment process, and that can calculate the proportion of recirculated blood with high accuracy.

[0007] One embodiment of the present invention is a blood purification device that purifies a patient's blood by extracorporeally circulating it through a blood circuit having an arterial blood circuit and a venous blood circuit, and includes: a control unit that controls a pump provided in the device based on predetermined parameters; a characteristic change imparting unit that can impart a local characteristic change in which a peak specific to a concentration change of the blood circulating extracorporeally through the blood circuit; a first detection unit and a second detection unit that are attached to the arterial blood circuit and the venous blood circuit, respectively, and detect the local characteristic change imparted by the characteristic change imparting unit; and a recirculation detection unit that detects recirculated blood, which is blood returned to the patient from the venous blood circuit and is guided back into the arterial blood circuit based on the local characteristic change detected by the first detection unit and the local characteristic change detected by the second detection unit, and calculates the proportion of the recirculated blood, and the control unit controls the pump by changing the parameters for driving the pump to measurement parameters that are different from the treatment parameters used in the treatment step in which blood purification therapy is performed, during a measurement step in which the recirculation detection unit detects the recirculated blood and calculates the proportion of the recirculated blood.

[0008] According to the present invention, during the measurement process in which the recirculation detection unit detects recirculated blood and calculates the proportion of recirculated blood, the control unit changes and controls the parameters for driving the pump to measurement parameters that are different from the treatment parameters used during the treatment process in which blood purification treatment is performed.This means that the pump can be controlled during the measurement process with optimal parameters that are different from those used during the treatment process, and the proportion of recirculated blood can be calculated with high accuracy.

[0009] Schematic diagram showing a blood purification device according to an embodiment of the present invention. Block diagram showing the main components of the blood purification device. Block diagram showing the recirculation detection unit of the blood purification device. Graph showing local concentration changes detected by the second detection unit and the first detection unit of the blood purification device. Flowchart showing the control contents by the control unit of the blood purification device.

[0010] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The blood purification device according to this embodiment purifies a patient's blood while circulating it extracorporeally, and is applied to a hemodialysis device used in hemodialysis treatment. As shown in Fig. 1, this hemodialysis device is capable of mounting a blood circuit 1 connected to a dialyzer 2 as a blood purification unit, and includes a dialysis device main body 6 that supplies dialysate to the dialyzer 2 while removing water from the dialyzer 2, and a control unit 16, a recirculation detection unit 17, and a display unit 18 disposed in the dialysis device main body 6.

[0011] As shown in the figure, the blood circuit 1 is mainly composed of an arterial blood circuit 1a and a venous blood circuit 1b, each made of flexible tubes, with a dialyzer 2 connected between the arterial blood circuit 1a and the venous blood circuit 1b. An arterial puncture needle a is connected to the tip of the arterial blood circuit 1a, and a peristaltic blood pump 3, a debubbling air trap chamber 4a, and a first detector 5a are disposed along the arterial blood circuit 1a. On the other hand, a venous puncture needle b is connected to the tip of the venous blood circuit 1b, and a second detector 5b and a debubbling air trap chamber 4b are disposed along the arterial blood circuit 1a.

[0012] When the blood pump 3 is driven with the arterial puncture needle a and the venous puncture needle b inserted into the patient, the patient's blood passes through the arterial blood circuit 1a, is debubbled in the air trap chamber 4a, and reaches the dialyzer 2. After being purified by the dialyzer 2, the patient's blood passes through the venous blood circuit 1b, is debubbled in the air trap chamber 4b, and returns to the patient's body. In this way, the patient's blood can be purified by the dialyzer 2 while being circulated extracorporeally through the blood circuit 1.

[0013] The dialyzer 2 has a housing formed with a blood inlet port 2a, a blood outlet port 2b, a dialysate inlet port 2c, and a dialysate outlet port 2d, of which the base end of the arterial blood circuit 1a is connected to the blood inlet port 2a, and the base end of the venous blood circuit 1b is connected to the blood outlet port 2b. The dialysate inlet port 2c and the dialysate outlet port 2d are connected to a dialysate inlet line 7 and a dialysate outlet line 8, respectively, which are extended from the dialysis device main body 6.

[0014] The dialyzer 2 contains a plurality of hollow fibers, the interior of which serves as a blood flow path, and the space between the outer circumferential surface of the hollow fibers and the inner circumferential surface of the housing serves as a dialysate flow path. The hollow fibers have many minute pores that penetrate from the outer circumferential surface to the inner circumferential surface, forming hollow fiber membranes, which allow impurities in the blood to pass through into the dialysate.

[0015] On the other hand, the dialysis device main body 6 is configured to include a duplex pump C, a bypass line 9 connected to the dialysate discharge line 8 so as to bypass the drain side Cb of the duplex pump C, a water removal pump 10 connected to the bypass line 9, a pressure pump 11 for causing the dialysate to flow from the dialyzer 2 to the drain side Cb of the duplex pump C, a bubble separating chamber 12, an atmospheric release line 13, and a solenoid valve 14.

[0016] The duplex pump C is disposed across the dialysate inlet line 7 and the dialysate outlet line 8, and serves to introduce dialysate from the dialysate inlet line 7 to the dialyzer 2 and to discharge the dialysate introduced into the dialyzer 2 from the dialysate outlet line 8. That is, the duplex pump C is a metering pump with a supply side Ca and a drain side Cb of approximately equal volume, and the dialysate flow path from the supply side Pa to the drain side Pb (specifically, the flow path downstream of the duplex pump C in the dialysate inlet line 7, the flow path upstream of the duplex pump C in the dialysate outlet line 8, and the dialysate flow path of the dialyzer 2) forms a closed flow path (a flow path that is kept sealed) when the solenoid valve 14 is closed.

[0017] The pressure pump 11 is connected between the dialyzer 2 and the duplex pump C in the dialysate discharge line 8, and serves to flow the dialysate from the dialyzer 2 to the duplex pump C. The pressure pump 11 is a non-positive displacement pump (pressure controlled type) such as a centrifugal type. The water removal pump 10, which will be described later, is also a non-positive displacement pump (pressure controlled type) such as a centrifugal type, similar to the pressure pump 11.

[0018] One end of the dialysate inlet line 7 is connected to the dialysate inlet port 2c of the dialyzer 2, and the other end is connected to a dialysate supply device (not shown) that prepares dialysate of a predetermined concentration. One end of the dialysate outlet line 8 is connected to the dialysate outlet port 2d of the dialyzer 2, and the other end is connected to drainage means (not shown). The dialysate supplied from the dialysate supply device passes through the dialysate inlet line 7 to the dialyzer 2, and then passes through the dialysate outlet line 8 and a bypass line 9 to be sent to the drainage means.

[0019] The ultrafiltration pump 10 is used to remove water from the patient's blood flowing through the dialyzer 2. That is, when the ultrafiltration pump 10 is driven, the volume of the liquid discharged from the dialysate discharge line 8 becomes greater than the volume of dialysate introduced from the dialysate inlet line 7, because the duplex pump C is a fixed-volume type, and water is removed from the blood by the amount of the greater volume.

[0020] The bubble separating chamber 12 is a so-called degassing chamber, and has a predetermined capacity and is connected between the pressure pump 11 and the duplex pump C in the dialysate discharge line 8, so as to be able to capture bubbles in the dialysate. The bypass line 9 described above is extended from the bubble separating chamber 12, as well as an atmosphere release line 13. The tip of the atmosphere release line 13 is open to the atmosphere, and a solenoid valve 14 serving as valve means is connected midway along the line.

[0021] The solenoid valve 14 can be opened and closed to open or close the atmosphere release line 13. In the open state, the bubble separation chamber 12 communicates with the outside air, and in the closed state, the bubble separation chamber 12 is cut off from the outside air. Then, before or after dialysis treatment, the solenoid valve 14 is operated to open the atmosphere release line 13, thereby releasing the air bubbles trapped in the bubble separation chamber 12 into the atmosphere.

[0022] In addition, a supply line La is connected to the dialysate introduction line 7 according to this embodiment. The supply line La is capable of supplying dialysate as a replacement fluid to the blood circuit 1, and its base end is connected to a portion of the dialysate introduction line 7 between the supply side Ca of the duplex pump C and the dialysate introduction port 2c of the dialyzer 2, and its tip branches into a pre-replacement fluid supply line La1 and a post-replacement fluid supply line La2, which are connected to the air trap chamber 4a of the arterial blood circuit 1a and the air trap chamber 4b of the venous blood circuit 1b, respectively.

[0023] A fluid replacement pump 15, which is a peristaltic pump similar to the blood pump 3, is disposed in the supply line La. During the blood purification treatment, by driving the fluid replacement pump 15, the dialysate in the dialysate introduction line 7 is supplied to the arterial blood circuit 1a via the pre-fluid replacement supply line La1, enabling pre-fluid replacement, and is also supplied to the venous blood circuit 1b via the post-fluid replacement supply line La2, enabling post-fluid replacement.

[0024] Here, the atmosphere vent line 13 and the solenoid valve 14 in this embodiment constitute the characteristic change imparting unit of the present invention, and by operating the solenoid valve 14 to open the atmosphere vent line 13, it is possible to impart a local concentration change (characteristic change) with a specific peak by performing a rapid and short-term concentration on the blood flowing through the dialyzer 2. That is, during dialysis treatment, when the solenoid valve 14 is operated to open the atmosphere vent line 13 that is in a closed state, the outlet pressure of the pressure pump 11 becomes approximately equal to atmospheric pressure, and therefore a momentary high negative pressure is generated upstream of the pressure pump 11, and rapid and short-term water removal (hemoconcentration) is performed on the blood flowing through the dialyzer 2 (blood flow path).

[0025] This allows a large amount of water to be removed from the blood in a short time at a pressure far greater than the ultrafiltration pressure generated by driving the water removal pump 10, and a unique peak can be imparted to the change in blood concentration (hematocrit value). The solenoid valve 14 opens the atmosphere vent line 13 in a short time (in this embodiment, the opening of the atmosphere vent line 13 can be set to any time equal to or less than 10 seconds, and even 1 second provides sufficient measurement accuracy), and the solenoid valve 14 is immediately operated to close the atmosphere vent line 13.

[0026] The time for which the solenoid valve 14 opens the air vent line 13 is preferably automatically controlled to be optimal based on blood concentration information (information about the patient's blood concentration) and pressure information (venous pressure, dialysate pressure, etc.). The term "sudden and short-term" in the present invention refers to a magnitude and duration that allows the applied pulse to be confirmed after passing through the circuit, and "unique" refers to a variation pattern that can be distinguished from variations due to other factors such as pump fluctuations or patient movement.

[0027] The first and second detectors 5a, 5b are disposed in the arterial and venous blood circuits 1a, 1b, respectively, to detect the concentration (specifically, the hematocrit value) of the blood flowing through these channels. The first and second detectors 5a, 5b are composed of hematocrit sensors equipped with a light-emitting element such as an LED and a light-receiving element such as a photodiode, and are configured to detect the hematocrit value, which indicates the concentration of the patient's blood, by irradiating the blood with light from the light-emitting element and receiving the transmitted or reflected light with the light-receiving element.

[0028] Specifically, the first detector 5a and the second detector 5b determine the hematocrit value, which indicates the blood concentration, based on the electrical signal output from the light-receiving element. Each component of blood, such as red blood cells and plasma, has its own unique light absorption characteristic. By utilizing this characteristic, the red blood cells required for measuring the hematocrit value can be electro-optically quantified to determine the hematocrit value. The near-infrared light irradiated from the light-emitting element is absorbed and scattered upon entering the blood, and is then received by the light-receiving element. The hematocrit value can be calculated by analyzing the light absorption and scattering rate based on the intensity of the received light.

[0029] The first detector 5a configured as described above is disposed in the arterial blood circuit 1a and therefore detects the hematocrit value of blood collected from the patient via the arterial puncture needle a during dialysis treatment, while the second detector 5b is disposed in the venous blood circuit 1b and therefore detects the hematocrit value of blood purified by the dialyzer 2 and returned to the patient. When a local concentration change is imparted by opening the solenoid valve 14, the second detector 5b detects a local concentration change α forming a characteristic peak P1, as shown in Figure 4, and when the blood returns to the arterial blood circuit 1a and is recirculated, the first detector 5a detects a local concentration change β remaining in the recirculated blood and forming a characteristic peak P2.

[0030] The control unit 16 is composed of, for example, a microcomputer, and as shown in FIG. 2, is electrically connected to pumps such as a duplex pump C that introduces and discharges dialysate to the dialyzer 2 (blood purification unit), a blood pump 3 arranged in the blood circuit 1, a water removal pump 10 that removes water from the blood circulating extracorporeally through the blood circuit 1, a pressure pump 11, a replacement fluid pump 15 that introduces replacement fluid (dialysis fluid) into the blood circuit, and a drug injection pump (not shown) that injects a drug solution such as heparin into the blood circuit 1, as well as electromagnetic valves such as an electromagnetic valve 14 that can impart local concentration changes with peaks specific to changes in blood concentration, and is capable of controlling these pumps and electromagnetic valves.

[0031] 2, the control unit 16 according to this embodiment is connected to an instruction input unit SW2, and an operator can input instructions by operating the instruction input unit SW2. The instruction input unit SW2 may be any unit that can be operated by the operator at any timing to input instructions, and may be, for example, a switch unit displayed on a touch panel (including the display unit 18) or a mechanical switch.

[0032] Furthermore, the first and second detectors 5a, 5b according to this embodiment are electrically connected to a recirculation detector 17 disposed in the dialysis machine main body 6, and the recirculation detector 17 is electrically connected to a display 18 configured as a touch panel. The display 18 displays the local concentration changes α, β detected by the first and second detectors 5a, 5b in a graph, and in addition to the graph display, can also display the ratio of recirculated blood calculated by the recirculation detector 17 in numerical form.

[0033] 2, the display unit 18 according to this embodiment is connected to a switching input unit SW1, and can be switched by the operator operating the switching input unit SW1. The instruction input unit SW2 can be any unit that can be operated by the operator at any timing to input, and may be, for example, a switch unit displayed on a touch panel (including the display unit 18) or a mechanical switch.

[0034] The recirculation detection unit 17 is configured with, for example, a microcomputer, and is capable of detecting recirculated blood, which is blood returned to the patient from the venous blood circuit 1b and then guided back into the arterial blood circuit 1a, based on the local concentration change β detected by the first detection unit 5a and the local concentration change α detected by the second detection unit 5b, and calculating the proportion of recirculated blood (recirculation rate). As shown in Figure 3, the recirculation detection unit 17 according to this embodiment is configured with a monitoring unit 17a, a graph creation unit 17b, a calculation unit 17c, and a memory unit 17d.

[0035] The monitoring unit 17a monitors the changes in blood concentration detected by the first detection unit 5a and the second detection unit 5b over time during blood purification treatment. The graph creation unit 17b creates a graph showing local concentration changes α and β based on the changes in blood concentration monitored over time by the monitoring unit 17a, and the calculation unit 17c calculates the proportion of recirculated blood (recirculation rate) based on the graph created by the graph creation unit 17b. The changes in blood concentration monitored by the monitoring unit 17a, the graph created by the graph creation unit 17b, and the proportion of recirculated blood (recirculation rate) calculated by the calculation unit 17c are stored in the memory unit 17d.

[0036] Specifically, recirculation detection unit 17 determines the change in hematocrit value (concentration change) from first detection unit 5a and second detection unit 5b based on a graph with elapsed time (integrated flow rate or time) on the horizontal axis and blood concentration (hematocrit value) on the vertical axis as shown in Figure 4, and calculates the area S1 of local concentration change α where characteristic peak P1 is formed and the area S2 of local concentration change β where characteristic peak P2 is formed using a mathematical method such as integration. Then, the proportion of recirculated blood (recirculation rate) Rrec is calculated using the following calculation formula.

[0037] Rrec (%)=S2 / S1×100

[0038] The proportion of recirculated blood (recirculation rate) Rrec thus determined is displayed on the display unit 18 so that it can be visually confirmed by a medical professional such as a doctor. If there is no blood recirculation, the above S2 will be 0, and the value displayed as the proportion of recirculated blood will be 0 (%). Furthermore, the display unit 18 according to this embodiment is capable of graphically displaying the local concentration changes detected by the first detection unit 5a and the second detection unit 5b, in addition to the recirculation rate, as shown in FIG. 4 , and is capable of displaying the local concentration change α at which the characteristic peak P1 is formed and the local concentration change β at which the characteristic peak P2 is formed, as curved graphs.

[0039] On the other hand, based on the blood concentrations detected by the first and second detectors 5 a and 5 b, the recirculation detector 17 creates a graph showing local concentration changes α and β, with the horizontal axis representing elapsed time (integrated flow rate or time) and the vertical axis representing blood concentration (hematocrit value), as shown in Fig. 4, and monitors the changes in blood concentration at a predetermined interval (e.g., every 0.1 seconds). This allows the detector 17 to detect the start time R1 and end time R2 of the local concentration change α at which the characteristic peak P1 is formed, and the start time W1 and end time W2 of the local concentration change β at which the characteristic peak P2 is formed, and to accurately calculate the area S1 of the local concentration change α and the area S2 of the local concentration change β.

[0040] 2, the control unit 16 according to this embodiment is provided with a parameter change unit 19, which is comprised of, for example, a predetermined functional circuit (control circuit) constituting a microcomputer, and the parameter change unit 19 changes the parameters for driving the pump (the pump to be controlled) to measurement parameters that are different from the treatment parameters used in the treatment step in which blood purification treatment is performed during the measurement step in which recirculated blood is detected by the recirculation detection unit 17 and the proportion of recirculated blood is calculated. The pumps controlled by the control unit 16 are various pumps included in the hemodialysis apparatus, such as the duplex pump C, the blood pump 3, the water removal pump 10, the pressure pump 11, the replacement fluid pump 15, and the drug injection pump.

[0041] Specifically, the control unit 16 is capable of switching between a measurement process in which the recirculation detection unit 17 detects recirculated blood and calculates the proportion of recirculated blood, and a treatment process in which blood purification treatment is performed. During the measurement process, the control unit temporarily changes to measurement parameters different from the treatment process parameters, controls the pump based on the measurement parameters, and then imparts a local concentration with a unique peak by the characteristic change imparting unit, and the recirculation detection unit 17 detects recirculated blood and calculates the proportion of recirculated blood.

[0042] In addition, the measurement parameters consist of parameters that slow down or stop the driving speed of the pump (the pump to be controlled) from that during the treatment process, and are specific parameters that allow the characteristic change imparting unit to impart a local concentration with a unique peak during the measurement process, and the recirculation detection unit 17 to detect recirculated blood and calculate the proportion of recirculated blood in a stable state.

[0043] In particular, the control unit 16 according to this embodiment temporarily changes the parameters for driving the pump to measurement parameters, drives the pump based on the measurement parameters, and then waits until the blood concentration detected by the first detection unit 5a and the second detection unit 5b becomes stable. On the condition that the blood concentration becomes stable, the characteristic change imparting unit imparts a local concentration with a unique peak, and the recirculation detection unit detects recirculated blood and calculates the proportion of recirculated blood.

[0044] In this manner, in this embodiment, the process of detecting recirculated blood by the recirculation detection unit 17 and calculating the proportion of recirculated blood is performed in a measurement process separate from the treatment process in which blood purification treatment is performed. This measurement process will be described with reference to the flowchart in FIG.

[0045] First, the measurement process is initiated upon input operation of the switch input unit SW1 by the operator. In S1, the parameter change unit 19 of the control unit 16 temporarily changes the parameters of the pump to be controlled to measurement parameters. The pump is then driven based on the measurement parameters. In S2, the control unit 16 waits until the blood concentration detected by the first and second detectors 5a and 5b stabilizes. The measurement parameters are parameters that reduce the drive speed of the pump (the pump to be controlled) from that during the treatment process. Then, upon input operation of the command input unit SW2 by the operator, the control unit 16 proceeds to S3, where the electromagnetic valve 14 is operated to open the vent line 13, thereby generating a localized concentration change with characteristic peaks P1 and P2.

[0046] The process then proceeds to S4, where the recirculation detection unit 17 detects recirculated blood and calculates the proportion of recirculated blood (recirculation rate) based on the local concentration change α detected by the first detection unit 5a and the local concentration change β detected by the second detection unit 5b. The calculated proportion of recirculated blood (recirculation rate) is displayed on the display unit 18 to prompt a medical professional, such as a doctor, to take appropriate action. After the detection of recirculated blood and the calculation of the proportion of recirculated blood (recirculation rate), the process proceeds to S5, where the parameter change unit 19 of the control unit 16 restores the measurement parameters to the treatment parameters. This completes the measurement process, and blood purification therapy can be performed based on the treatment parameters.

[0047] According to this embodiment, during the measurement process in which the recirculated blood detection unit 17 detects the recirculated blood and calculates the proportion of recirculated blood, the control unit 16 changes and controls the parameters for driving the pump to measurement parameters that are different from the treatment parameters used during the treatment process in which blood purification treatment is performed.This means that the pump can be controlled during the measurement process with optimal parameters that are different from those used during the treatment process, and the proportion of recirculated blood can be calculated with high accuracy.

[0048] Although the present embodiment has been described above, the present invention is not limited to this, and for example, the characteristic change imparting unit is not limited to being composed of the air vent line 13 and the solenoid valve 14, and other means may be used as long as they can impart a local concentration change with a unique peak. Furthermore, although the characteristic change imparting unit according to the present embodiment locally changes the blood concentration by concentrating the blood through water removal, the blood may also be locally changed in concentration by diluting it, for example, by introducing a replacement fluid (dialysis fluid) such as a replacement fluid into the blood circuit.

[0049] Furthermore, the first and second detectors 5a and 5b may be configured with a sensor other than a hematocrit sensor (e.g., a sensor for detecting hemoglobin concentration or a sensor for detecting protein concentration) as long as it can detect a change in blood concentration resulting in the formation of a specific peak. Furthermore, the first and second detectors 5a and 5b may be disposed at any location in the arterial and venous blood circuits 1a and 1b, respectively.

[0050] Furthermore, although the change in blood characteristics in this embodiment is a change in blood concentration, it may also be a change in other characteristics, such as a change in blood temperature. For example, it may be possible to use ultrasound, inject a marker (saline solution or microbubbles) into the blood flow, measure the dilution curve using an ultrasound probe, and capture the change in blood flow in the blood circuit in real time, thereby making it possible to quantify the recirculation rate.

[0051] Other examples include a method for evaluating recirculation by injecting a dye into an arterial blood circuit and measuring absorbance in a venous blood circuit, a method for injecting cooled saline into a blood circuit and measuring changes in blood temperature, and calculating the recirculation rate from the rate of temperature change using temperature sensors placed in the arterial and venous blood circuits, a method using electrical impedance to measure changes in the electrical impedance of blood in the blood circuit and analyze changes in blood flow, and calculating impedance changes due to recirculation using the conductivity of saline, and an optical method using infrared spectroscopy (NIRS) to measure changes in blood oxygen saturation and hemoglobin concentration, and evaluating the effects of recirculation by comparing data from the arterial and venous blood circuits.

[0052] The first embodiment of the present invention is a blood purification device that circulates a patient's blood extracorporeally through a blood circuit 1 having an arterial blood circuit 1a and a venous blood circuit 1b, and purifies the blood. The blood purification device includes a control unit 16 that controls a pump provided in the device based on predetermined parameters, a characteristic change imparting unit that can impart a local concentration change in which a peak specific to the concentration change of the blood circulating extracorporeally through the blood circuit 1 is formed, a first detection unit 5a and a second detection unit 5b that are attached to the arterial blood circuit 1a and the venous blood circuit 1b, respectively, and that detect the local concentration change imparted by the characteristic change imparting unit, and and a recirculation detection unit 17 that detects recirculated blood, which is blood returned from the venous blood circuit 1b to the patient and is introduced back into the arterial blood circuit 1a, based on the local concentration change β detected by the first detection unit 5a and the local concentration change α detected by the second detection unit 5b, and calculates the proportion of recirculated blood. During the measurement step in which the recirculation detection unit 17 detects recirculated blood and calculates the proportion of recirculated blood, the control unit 16 controls the pump by changing the parameters for driving the pump to measurement parameters that are different from the treatment parameters used during the treatment step in which blood purification treatment is performed. This makes it possible to control the pump during the measurement step with optimal parameters that are different from those used during the treatment step, and to calculate the proportion of recirculated blood with high accuracy.

[0053] In a second embodiment of the present invention, the measurement parameter in the first embodiment is a parameter that slows down or stops the pump drive speed from that during the treatment step, thereby enabling the characteristic change applying unit to apply a local concentration with a specific peak during the measurement step, and the recirculation detection unit 17 to detect recirculated blood and calculate the proportion of recirculated blood in a stable state.

[0054] In a third embodiment of the present invention, the control unit 16 of the first embodiment temporarily changes the parameters for driving the pump to measurement parameters, drives the pump based on the measurement parameters, and then waits until the blood concentrations detected by the first detection unit 5 a and the second detection unit 5 b reach a stable state, and, on the condition that the blood concentrations reach a stable state, the characteristic change imparting unit imparts a local concentration with a unique peak, and the recirculation detection unit detects recirculated blood and calculates the proportion of recirculated blood. This allows the characteristic change imparting unit to impart a local concentration with a unique peak in a stable state at all times, and allows the recirculation detection unit to accurately detect recirculated blood and calculate the proportion of recirculated blood.

[0055] A fourth embodiment of the present invention is the third embodiment, in which the control unit automatically restores the parameters for driving the pump to the treatment parameters after the recirculation detection unit detects recirculated blood and calculates the proportion of recirculated blood, thereby enabling a smooth transition to the treatment process after the measurement process is completed.

[0056] In a fifth embodiment of the present invention, in the first embodiment, the blood characteristic is blood concentration, thereby detecting recirculating blood based on changes in blood concentration and calculating the proportion of recirculating blood.

[0057] The present invention can also be applied to devices with different external shapes or devices with additional functions, provided that they have the same gist as the present invention.

[0058] 1 Blood circuit 1a Arterial blood circuit 1b Venous blood circuit 2 Dialyzer (blood purification section) 3 Blood pump 4a, 4b Air trap chamber 5a First detection section 5b Second detection section 6 Dialysis device main body 7 Dialysis fluid introduction line 8 Dialysis fluid discharge line 9 Bypass line 10 Water removal pump 11 Pressure pump 12 Air bubble separation chamber 13 Atmospheric release line 14 Solenoid valve 15 Infusion fluid pump 16 Control section 17 Recirculation detection section 18 Display section C Duplex pump La Supply line La1 Pre-infusion fluid supply line La2 Post-infusion fluid supply line SW1 Switching input section SW2 Instruction input section

Claims

1. A blood purification device that purifies a patient's blood by circulating it extracorporeally through a blood circuit having an arterial blood circuit and a venous blood circuit, comprising: a control unit that controls a pump equipped in the device based on predetermined parameters; a characteristic change imparting unit that can impart a local characteristic change with a peak specific to the characteristic change of the blood circulating extracorporeally through the blood circuit; a first detection unit and a second detection unit attached to the arterial blood circuit and the venous blood circuit, respectively, that detect the local characteristic change imparted by the characteristic change imparting unit; and a recirculation detection unit that detects recirculated blood, which is blood returned to the patient from the venous blood circuit and is guided back into the arterial blood circuit based on the local characteristic change detected by the first detection unit and the local characteristic change detected by the second detection unit, and calculates the proportion of the recirculated blood; and the control unit controls the pump by changing the parameters for driving the pump to measurement parameters that are different from the treatment parameters used in the treatment step in which blood purification therapy is performed during the measurement step in which the recirculation detection unit detects the recirculated blood and calculates the proportion of the recirculated blood.

2. The blood purification apparatus according to claim 1, wherein said measurement parameters comprise parameters for slowing down or stopping the pump drive speed from that during said treatment step.

3. The blood purification device of claim 1, wherein the control unit temporarily changes the parameters for driving the pump to measurement parameters, drives the pump based on the measurement parameters, and then waits until the blood characteristics detected by the first and second detection units reach a stable state, and, on the condition that the blood characteristics reach a stable state, the characteristic change imparting unit imparts the local characteristic in which the unique peak is formed, and the recirculation detection unit detects recirculated blood and calculates the proportion of recirculated blood.

4. A blood purification device as described in claim 3, wherein the control unit automatically restores the parameters for driving the pump to the treatment parameters after the recirculation detection unit detects recirculated blood and calculates the proportion of recirculated blood.

5. The blood purification device according to claim 1, wherein the blood characteristic is blood concentration.

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