Blood purification device

Abstract

Provided is a blood purification device capable of calculating a proportion of recirculated blood with high accuracy by accurately detecting a start point of time of at least a local characteristic change.　The present invention is provided with: a characteristic change imparting unit that can impart a local concentration change in which a peak specific to concentration changes in blood circulating extracorporeally in a blood circuit 1 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 recirculating blood on the basis of a local concentration change β detected by the first detection unit 5a and a local concentration change α detected by the second detection unit 5b, and that calculates the proportion of recirculating blood. The recirculation detection unit 17 detects a noise waveform γ detected immediately before detection of the local concentration changes and identifies a start time point R1 of the local concentration change α on the basis of the noise waveform γ.

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 a local concentration change is applied, the detected local concentration change may vary depending on the patient's condition, the treatment environment, etc. Therefore, in order to accurately calculate the proportion of recirculated blood, it is necessary to accurately grasp the start and end points of the local concentration change. Therefore, the present applicant has conducted extensive research to accurately detect at least the start point of the local concentration change in order to accurately calculate the proportion of recirculated blood. 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, 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 accurately calculate the proportion of recirculated blood by accurately detecting at least the start or end point of a local characteristic change.

[0007] One embodiment of the present invention is a blood purification device that circulates a patient's blood extracorporeally through a blood circuit having an arterial blood circuit and a venous blood circuit, and purifies the blood. The blood purification device comprises: a characteristic change imparting unit that can impart a local characteristic change having a peak specific to a characteristic 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 from the venous blood circuit to the patient and then 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 a ratio of the recirculated blood. The recirculation detection unit detects a noise waveform detected immediately before the local characteristic change is detected, and identifies the start time of the local characteristic change based on the noise waveform.

[0008] Another 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 characteristic change imparting unit that can impart a local characteristic change having 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 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 from the venous blood circuit to the patient and is guided back to the arterial blood circuit and flows therein, 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 ratio of the recirculated blood, and the recirculation detection unit sequentially searches back to the start of detection of the local characteristic change, using the time point at which a specific peak in the local characteristic change was detected as a reference, and identifies the time point at which the characteristic change changed from decreasing to increasing as the start time of the local characteristic change.

[0009] Yet another embodiment of the present invention is a blood purification device that circulates a patient's blood extracorporeally through a blood circuit having an arterial blood circuit and a venous blood circuit, and purifies the blood, comprising: a characteristic change imparting unit that can impart a local characteristic change in which 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 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 ratio of the recirculated blood, and the recirculation detection unit detects the amount of change in the local characteristic change over time or with the accumulated blood flow rate after the specific peak is detected, and identifies the point in time when the amount of change changes from a decrease to an increase as the end point of the local characteristic change.

[0010] According to the present invention, the ratio of recirculated blood can be calculated with high accuracy by accurately detecting at least the start or end point of a local characteristic change.

[0011] Schematic diagram showing a blood purification device according to an embodiment of the present invention. Block diagram showing the main configuration 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 control details by the control unit of the blood purification device. Flowchart showing control details during the measurement process by the recirculation detection unit of the blood purification device according to the first embodiment of the present invention. Graph for explaining the measurement process by the recirculation detection unit. Flowchart showing control details during the measurement process by the recirculation detection unit of the blood purification device according to the second embodiment of the present invention. Graph for explaining the measurement process by the recirculation detection unit. Flowchart showing control details during the measurement process by the recirculation detection unit of the blood purification device according to the third embodiment of the present invention. Graph for explaining the measurement process by the recirculation detection unit. Flowchart showing control details during the measurement process by the recirculation detection unit of the blood purification device according to the fourth embodiment of the present invention. Graph for explaining the measurement process by the recirculation detection unit. Flowchart showing control details during the measurement process by the recirculation detection unit of the blood purification device according to the fifth embodiment of the present invention.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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).

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 2, the display unit 18 according to this embodiment is connected to a switching input unit SW1, and can perform switching input by the operator operating the switching input unit SW1. Such 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] Rrec (%)=S2 / S1×100

[0040] 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.

[0041] 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.

[0042] 7, the recirculation detection unit 17 according to this embodiment is configured to detect a noise waveform γ detected immediately before the local concentration change α is detected, and to identify the start time point R1 of the local concentration change α based on the noise waveform γ. The noise waveform γ is generated as a precursor noise of the local concentration change α detected by the second detection unit 5b when the solenoid valve 14 constituting the characteristic change imparting unit is changed from a closed state to an open state to impart a local concentration change.

[0043] Specifically, after detecting peak P3 of noise waveform γ, recirculation detector 17 identifies the point at which the concentration change changes from a decrease to an increase as start point R1 of local concentration change α. For example, the maximum or minimum value of the detected blood concentration is updated every predetermined period, and the concentration change is considered to have decreased when the blood concentration value decreases from the maximum value, and to have increased when the blood concentration value increases from the minimum value.

[0044] Furthermore, for example, the recirculation detection unit 17 can sequentially detect the slope or area for each predetermined period in a graph showing concentration changes over time or with the accumulated blood flow rate, and can detect decreases (a downward trend to the right in the graph) and increases (an upward trend to the right in the graph) in concentration changes based on the detected changes in slope or area.

[0045] The peaks of the waveforms in the graph (peak P1 specific to the local concentration change α, peak P2 specific to the local concentration change β, and peak P3 of the noise waveform γ) can be found by calculating the maximum value of each waveform. The slope for each predetermined period can be found by applying a least-squares method or other calculation method to the curve within the period, and the area for each predetermined period can be found by applying an integration method or other calculation method to the curve within the period.

[0046] However, in this embodiment, the process of detecting recirculated blood using 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. During this measurement process, the control unit 16 changes the parameters for driving the pumps to be controlled (duplex pump C, blood pump 3, water removal pump 10, pressurization pump 11, fluid replacement pump 15, chemical solution infusion pump, etc.) to measurement parameters different from those used in the treatment process in which blood purification treatment is performed. This measurement process will be described based on the flowchart in Figure 5.

[0047] First, the measurement process is initiated upon input operation of the switch input unit SW1 by the operator. In S1, the control unit 16 temporarily changes the pump to be controlled to a measurement parameter, drives the pump based on the measurement parameter, and then in S2, waits until the blood concentration detected by the first detector 5a and the second detector 5b stabilizes. The measurement parameter is a parameter that slows or stops the pump (the pump to be controlled) from the speed during the treatment process. Then, upon input operation of the command input unit SW2 by the operator, the process proceeds to S3, where the solenoid valve 14 is operated to open the air vent line 13, thereby generating a localized concentration change with characteristic peaks P1 and P2.

[0048] The process then proceeds to S4, where the recirculation detection unit 17 detects recirculated blood 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, and calculates the proportion of recirculated blood (recirculation rate). 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 action. After the recirculated blood is detected and the proportion of recirculated blood (recirculation rate) is calculated, the process proceeds to S5, where the control unit 16 returns from the measurement parameters to the treatment parameters, provided that the operator operates the switch input unit SW1. This completes the measurement process, and blood purification therapy can be performed based on the treatment parameters.

[0049] Next, specific control by the recirculation detection unit 17 for measurement S4 in the measurement step will be described with reference to the flowchart of Fig. 6. After a local concentration change is imparted in S3 of Fig. 5, the recirculation detection unit 17 detects a noise waveform γ in Sa1, and when the noise waveform γ is detected, the end of the noise waveform γ is detected in Sa2. The end of the noise waveform γ can be determined by detecting peak P3 of the noise waveform γ and then detecting the point in time at which the concentration change changes from a decrease to an increase from peak P3, and this end can be taken as the start point R1 of the local concentration change α.

[0050] Then, proceeding to Sa3, the areas S1 and S2 shown in FIG. 4 are calculated based on 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 the recirculation rate (Rrec (%)), which is the proportion of recirculated blood, can be calculated from the ratio of these areas S1 and S2.

[0051] According to this embodiment, the recirculation detection unit 17 detects the noise waveform γ that is detected immediately before the local concentration change α is detected, and identifies the start point R1 of the local concentration change α based on the noise waveform γ.Therefore, by using the noise waveform γ to accurately detect at least the start point R1 of the local concentration change α, the ratio of recirculated blood can be calculated with high accuracy.

[0052] Next, a blood purification apparatus according to a second embodiment of the present invention will be described. The blood purification apparatus according to this embodiment purifies a patient's blood while circulating it extracorporeally, and is applied to a hemodialysis apparatus used in hemodialysis treatment. As shown in Fig. 1, this hemodialysis apparatus comprises a blood circuit 1 connected to a dialyzer 2 as a blood purification unit, a dialysis apparatus 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 apparatus main body 6. Note that components similar to those in the first embodiment are designated by the same reference numerals, and detailed descriptions thereof will be omitted.

[0053] As in the first embodiment, the recirculation detector 17 generates 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), based on the blood concentrations detected by the first detector 5 a and the second detector 5 b, as shown in Fig. 4. The graph also monitors the blood concentration changes at a predetermined interval (e.g., every 0.1 seconds). This allows 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, to be detected, and the area S1 of the local concentration change α and the area S2 of the local concentration change β to be calculated with high accuracy.

[0054] Here, the recirculation detection unit 17 according to this embodiment 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 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 ratio of recirculated blood (recirculation rate).

[0055] In particular, the recirculation detection unit 17 of this embodiment is configured to, as shown in Figure 9, use the time when a specific peak P1 in the local concentration change α is detected as a reference point and sequentially search back to the start of detection of the local concentration change α (i.e., search in the direction f from the time of the specific peak P1 in Figure 9), and identify the time when the concentration change changes from a decrease to an increase as the start time R1 of the local concentration change α.

[0056] The peaks of the waveforms in the graph (peak P1 specific to the local concentration change α, peak P2 specific to the local concentration change β, and peak P3 of the noise waveform γ) can be found by calculating the maximum value of each waveform, as in the first embodiment. Also, the slope for each predetermined period can be found by applying a calculation method such as the least squares method to the curve within the period, as in the first embodiment, and the area for each predetermined period can be found by applying a calculation method such as integration to the curve within the period.

[0057] However, in this embodiment, as in the first embodiment, the process of detecting recirculated blood using 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. During this measurement process, the control unit 16 changes the parameters for driving the pumps to be controlled (duplex pump C, blood pump 3, water removal pump 10, pressurization pump 11, fluid replacement pump 15, drug solution infusion pump, etc.) to measurement parameters different from those used in the treatment process in which blood purification treatment is performed. This measurement process is as described in the first embodiment based on the flowchart in FIG. 5.

[0058] Next, the specific control by the recirculation detection unit 17 for measurement S4 (see FIG. 5) in the measurement step will be described with reference to the flowchart in FIG. 8. After a local concentration change is given in S3 of FIG. 5, a specific peak P1 of the local concentration change α is detected by the recirculation detection unit 17 in Sb1. After the specific peak P1 is detected, the process proceeds to Sb2, where, using the time point at which the specific peak P1 was detected as a reference, a sequential search is performed (sequential search in the direction f) going back to the start of detection of the local concentration change α, and the time point at which the concentration change changes from a decrease to an increase can be determined as the start time R1 of the local concentration change α.

[0059] Then, proceeding to Sb3, the areas S1 and S2 shown in FIG. 4 are calculated based on 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 the recirculation rate (Rrec (%)), which is the proportion of recirculated blood, can be calculated from the ratio of these areas S1 and S2.

[0060] According to this embodiment, the recirculation detection unit 17 uses the time when a specific peak P1 in the local concentration change α is detected as a reference point and sequentially searches back to the start of detection of the local concentration change α, and identifies the time when the concentration change changes from a decrease to an increase as the start time R1 of the local concentration change α.Therefore, by using the specific peak P1 to accurately detect at least the start time R1 of the local concentration change α, the proportion of recirculated blood can be calculated with high accuracy.

[0061] Next, a blood purification apparatus according to a third embodiment of the present invention will be described. The blood purification apparatus according to this embodiment purifies a patient's blood while circulating it extracorporeally, and is applied to a hemodialysis apparatus used in hemodialysis treatment. As shown in Fig. 1, this hemodialysis apparatus comprises a blood circuit 1 connected to a dialyzer 2 as a blood purification unit, a dialysis apparatus 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 apparatus main body 6. Note that components similar to those in the first embodiment are designated by the same reference numerals, and detailed descriptions thereof will be omitted.

[0062] As in the first embodiment, the recirculation detector 17 generates 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), based on the blood concentrations detected by the first detector 5 a and the second detector 5 b, as shown in Fig. 4. The graph also monitors the blood concentration changes at a predetermined interval (e.g., every 0.1 seconds). This allows 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, to be detected, and the area S1 of the local concentration change α and the area S2 of the local concentration change β to be calculated with high accuracy.

[0063] 11, the recirculation detection unit 17 according to this embodiment is configured to detect the amount of change in the local concentration change a over time or with the cumulative blood flow rate after the detection of the characteristic peak P1, and identify the point at which the amount of change changes from a decrease to an increase as the end point R2 of the local concentration change a. Specifically, the recirculation detection unit 17 sequentially (in this embodiment, for each cycle) calculates the value of the blood concentration on the graph after the detection of the characteristic peak P1 in the local concentration change a, and identifies the point at which the calculated value of the blood concentration on the graph becomes a minimum as the end point R2.

[0064] For example, the recirculation detection unit 17 can sequentially calculate the blood concentration value of the graph for each period after detecting the characteristic peak P1 of the local concentration change α, and identify the position where the calculated blood concentration value of the graph changes from a decrease to an increase as the minimum value. Furthermore, if the blood concentration value does not change from a decrease to an increase and remains constant (if the graph is flat), the position where the blood concentration value first changes to a constant value can be identified as the minimum value. Furthermore, if the blood concentration value continues to decrease, the measurement end position can be identified as the minimum value. The waveform peaks in the graph (the characteristic peak P1 of the local concentration change α and the characteristic peak P2 of the local concentration change β) can be determined by calculating the maximum value of each waveform.

[0065] However, in this embodiment, the process of detecting recirculated blood using 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. During this measurement process, the control unit 16 changes the parameters for driving the pumps to be controlled (duplex pump C, blood pump 3, water removal pump 10, pressurization pump 11, fluid replacement pump 15, chemical solution infusion pump, etc.) to measurement parameters that are different from those used in the treatment process in which blood purification treatment is performed. This measurement process is the same as in the first embodiment and will be described based on the flowchart in FIG. 5.

[0066] First, when the measurement process is initiated upon the operator's operation of the switch input unit SW1, the control unit 16 temporarily changes the pump to be controlled to a measurement parameter in S1, drives the pump based on the measurement parameter, and then waits until the blood concentration detected by the first detector 5a and the second detector 5b stabilizes in S2. These measurement parameters consist of parameters that slow or stop the drive speed of the pump (the pump to be controlled) from that during the treatment process. Then, upon the operator's operation of the command input unit SW2, the process proceeds to S3, where the solenoid valve 14 is operated to open the atmosphere vent line 13, thereby creating a localized concentration change with characteristic peaks P1 and P2.

[0067] The process then proceeds to S4, where the recirculation detection unit 17 detects recirculated blood 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, and calculates the proportion of recirculated blood (recirculation rate). After the recirculated blood is detected and the proportion of recirculated blood (recirculation rate) is calculated, the process proceeds to S5, where the control unit 16 restores the measurement parameters to the treatment parameters, provided that the operator operates the switch input unit SW1. This completes the measurement process, and blood purification therapy can be performed based on the treatment parameters.

[0068] Next, specific control by the recirculation detection unit 17 for measurement S4 of the measurement step will be described with reference to the flowchart in Figure 10. After the local concentration change is given in S3 of Figure 5, the recirculation detection unit 17 detects a characteristic peak P1 of the local concentration change α in Sc1. When the characteristic peak P1 is detected, the minimum concentration value after the detection of the characteristic peak P1 is detected in Sc2. This minimum value can be obtained by sequentially calculating the blood concentration value on the graph after the characteristic peak P1 of the local concentration change α is detected, and the point at which the calculated blood concentration value on the graph reaches its minimum can be identified as the end point R2.

[0069] Then, proceeding to Sc3, the areas S1 and S2 shown in FIG. 4 are calculated based on 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 the recirculation rate (Rrec (%)), which is the proportion of recirculated blood, can be calculated from the ratio of these areas S1 and S2.

[0070] According to this embodiment, the recirculation detection unit 17 sequentially calculates the value of the blood concentration on the graph after the characteristic peak P1 in the local concentration change α is detected, and identifies the point in time at which the calculated blood concentration value on the graph becomes the minimum as the end point R2.Therefore, by determining the minimum value of the blood concentration after the characteristic peak P1 and accurately detecting at least the end point R2 of the local concentration change α, the proportion of recirculated blood can be calculated with high accuracy.

[0071] Next, a blood purification apparatus according to a fourth embodiment of the present invention will be described. The blood purification apparatus according to this embodiment purifies a patient's blood while circulating it extracorporeally, and is applied to a hemodialysis apparatus used in hemodialysis treatment. As shown in Fig. 1, this hemodialysis apparatus comprises a blood circuit 1 connected to a dialyzer 2 as a blood purification unit, a dialysis apparatus 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 apparatus main body 6. Note that components similar to those in the first embodiment are designated by the same reference numerals, and detailed descriptions thereof will be omitted.

[0072] As in the first embodiment, the recirculation detector 17 generates 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), based on the blood concentrations detected by the first detector 5 a and the second detector 5 b, as shown in Fig. 4. The graph also monitors the blood concentration changes at a predetermined interval (e.g., every 0.1 seconds). This allows 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, to be detected, and the area S1 of the local concentration change α and the area S2 of the local concentration change β to be calculated with high accuracy.

[0073] Here, the recirculation detection unit 17 according to this embodiment 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 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 ratio of recirculated blood (recirculation rate).

[0074] In particular, the recirculation detection unit 17 according to this embodiment is configured to sequentially (for each cycle in this embodiment) calculate the slope of the graph (the slope of the line m connecting two points in the figure) after detecting a characteristic peak P1 in the local concentration change α, as shown in FIG. 13 , and identify the point at which the calculated slope of the graph becomes horizontal (the slope is 0) as the end point R2. Note that, as in the first embodiment, the waveform peaks in the graph (the characteristic peak P1 of the local concentration change α and the characteristic peak P2 of the local concentration change β) can be determined by calculating the maximum value of each waveform. Furthermore, the slope for each predetermined cycle can be determined using a calculation method such as the least squares method for the curve within the cycle.

[0075] However, in this embodiment, as in the first embodiment, the process of detecting recirculated blood using 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. During this measurement process, the control unit 16 changes the parameters for driving the pumps to be controlled (duplex pump C, blood pump 3, water removal pump 10, pressurization pump 11, fluid replacement pump 15, drug solution infusion pump, etc.) to measurement parameters different from those used in the treatment process in which blood purification treatment is performed. This measurement process is as described in the first embodiment based on the flowchart in FIG. 5.

[0076] Next, the specific control content by the recirculation detection unit 17 for measurement S4 (see FIG. 5) in the measurement step will be described with reference to the flowchart in FIG. 12. After a local concentration change is given in S3 of FIG. 5, a specific peak P1 of the local concentration change α is detected by the recirculation detection unit 17 in Sd1. After the specific peak P1 is detected, the process proceeds to Sd2, where the slope of the graph after the specific peak P1 is detected is calculated sequentially, and the point in time when the calculated slope of the graph becomes horizontal (slope is 0) is identified as the end point R2.

[0077] Then, proceeding to Sd3, the areas S1 and S2 shown in FIG. 4 are calculated based on 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 the recirculation rate (Rrec (%)), which is the proportion of recirculated blood, can be calculated from the ratio of these areas S1 and S2.

[0078] According to this embodiment, the recirculation detection unit 17 sequentially calculates the slope of the graph after the characteristic peak P1 in the local concentration change α is detected, and identifies the point at which the calculated slope of the graph becomes horizontal as the end point R2. Therefore, by determining the slope of the graph after the characteristic peak P1 and accurately detecting at least the end point R2 of the local concentration change α, the proportion of recirculated blood can be calculated with high accuracy.

[0079] Next, a blood purification apparatus according to a fifth embodiment of the present invention will be described. The blood purification apparatus according to this embodiment purifies a patient's blood while circulating it extracorporeally, and is applied to a hemodialysis apparatus used in hemodialysis treatment. As shown in Fig. 1, this hemodialysis apparatus comprises a blood circuit 1 connected to a dialyzer 2 as a blood purification unit, a dialysis apparatus 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 apparatus main body 6. Note that components similar to those in the first embodiment are designated by the same reference numerals, and detailed descriptions thereof will be omitted.

[0080] As in the first embodiment, the recirculation detector 17 generates 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), based on the blood concentrations detected by the first detector 5 a and the second detector 5 b, as shown in Fig. 5. The graph also monitors the blood concentration changes at a predetermined interval (e.g., every 0.1 seconds). This allows 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, to be detected, and the area S1 of the local concentration change α and the area S2 of the local concentration change β to be calculated with high accuracy.

[0081] Here, the recirculation detection unit 17 according to this embodiment 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 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 ratio of recirculated blood (recirculation rate).

[0082] In particular, the recirculation detection unit 17 according to this embodiment is configured to sequentially (in this embodiment, for each cycle) calculate the area of ​​the graph (the area Sn of the region between two points in the figure) after detecting a characteristic peak P1 in the local concentration change α, as shown in FIG. 15 , and identify the point at which the rate of change in the calculated area of ​​the graph decreases as the end point R2. Note that, as in the first embodiment, the waveform peaks in the graph (the characteristic peak P1 of the local concentration change α and the characteristic peak P2 of the local concentration change β) can be determined by calculating the maximum value of each waveform. Furthermore, the area for each predetermined cycle can be determined by using a calculation method such as integration on the curve within the cycle.

[0083] However, in this embodiment, as in the first embodiment, the process of detecting recirculated blood using 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. During this measurement process, the control unit 16 changes the parameters for driving the pumps to be controlled (duplex pump C, blood pump 3, water removal pump 10, pressurization pump 11, replacement fluid pump 15, etc.) to measurement parameters that are different from those used in the treatment process in which blood purification treatment is performed. This measurement process is as described in the first embodiment based on the flowchart in FIG. 5.

[0084] Next, the specific control content by the recirculation detection unit 17 for measurement S4 (see FIG. 5) in the measurement process will be described with reference to the flowchart in FIG. 14. After a local concentration change is given in S3 of FIG. 5, a specific peak P1 of the local concentration change α is detected by the recirculation detection unit 17 in Se1. After the specific peak P1 is detected, the process proceeds to Se2, where the area of ​​the graph after the specific peak P1 is detected is sequentially calculated, and the point in time at which the rate of change in the calculated area of ​​the graph decreases is identified as the end point R2.

[0085] Then, proceeding to Se3, the areas S1 and S2 shown in FIG. 5 are calculated based on 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 the recirculation rate (Rrec (%)), which is the proportion of recirculated blood, can be calculated from the ratio of these areas S1 and S2.

[0086] According to this embodiment, the recirculation detection unit 17 sequentially calculates the area of ​​the graph after a specific peak P1 in the local concentration change α is detected, and identifies the point at which the rate of change in the calculated area of ​​the graph decreases as the end point R2.Therefore, by determining the area of ​​the graph after the specific peak P1 and accurately detecting at least the end point R2 of the local concentration change α, the proportion of recirculated blood can be calculated with high accuracy.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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 characteristic change imparting unit (an air-opening line 13 and an electromagnetic valve 14) 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, and 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 changes α and β imparted by the characteristic change imparting unit. The blood circulation detecting unit 17 detects a noise waveform γ detected immediately before the local concentration change is detected and identifies a start time R1 of the local concentration change α based on the noise waveform γ. This makes it possible to accurately detect at least the start time R1 of the local concentration change α using the noise waveform γ, thereby enabling the ratio of recirculated blood to be calculated with high precision.

[0092] In the second embodiment of the present invention, the recirculation detector 17 of the first embodiment detects the peak P3 of the noise waveform γ and then identifies the point in time when the concentration change changes from a decrease to an increase as the start point R1 of the local concentration change α. This makes it possible to accurately identify the start point R1 of the local concentration change α using the noise waveform γ.

[0093] In a third embodiment of the present invention, in the second embodiment, the recirculation detector 17 sequentially detects the slope or area for each predetermined period in a graph showing the concentration change over time or with the accumulated blood flow rate, and detects the decrease or increase in the concentration change based on the detected change in slope or area. This allows the start time R1 of the local concentration change α to be identified smoothly and accurately using the noise waveform γ.

[0094] A fourth 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 device comprises a characteristic change imparting unit (an air-opening line 13 and an electromagnetic valve 14) that can impart a local concentration change with a peak specific to the concentration change of the blood circulating extracorporeally through the blood circuit 1, 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 changes α and β imparted by the characteristic change imparting unit, and a detection unit 5b that detects the local concentration changes α and β imparted by the characteristic change imparting unit. The recirculation detection unit 17 detects recirculated blood, which is blood returned to the patient from the venous blood circuit 1b and then introduced back into the arterial blood circuit 1a, based on the detected local concentration change β and the local concentration change α detected by the second detection unit 5b, and calculates the proportion of recirculated blood.The recirculation detection unit 17 uses the time when a specific peak P1 in the local concentration change α is detected as a reference point and sequentially searches back to the start of detection of the local concentration change α, identifying the time when the concentration change changes from a decrease to an increase as the start time R1 of the local concentration change.This allows the proportion of recirculated blood to be calculated with high accuracy by accurately detecting at least the start time R1 of the local concentration change α using the specific peak P1.

[0095] In a fifth embodiment of the present invention, in the fourth embodiment, the recirculation detector 17 sequentially detects the slope or area for each predetermined period in a graph showing the concentration change over time or with the accumulated blood flow rate, and detects the decrease or increase in the concentration change based on the detected change in slope or area. This allows the start time R1 of the local concentration change α to be smoothly and accurately identified using a specific peak P1.

[0096] The sixth 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 characteristic change imparting unit (an air-opening line 13 and an electromagnetic valve 14) that can impart a local concentration change with a peak specific to the concentration change of the blood circulating extracorporeally through the blood circuit 1, 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 changes α and β imparted by the characteristic change imparting unit, and a detection unit 5c that detects the local concentration changes α and β imparted by the first detection unit 5a. The blood purification apparatus is equipped with a recirculation detection unit 17 that detects recirculated blood, which is blood returned from the venous blood circuit 1b and then introduced back into the arterial blood circuit 1a, based on the local concentration change β detected by the first detection unit 5b and the local concentration change α detected by the second detection unit 5b, and calculates the proportion of recirculated blood. The recirculation detection unit 17 detects the amount of change in the local concentration change α over time or with the integrated blood flow rate after the detection of the specific peak P1, and identifies the point in time when the amount of change changes from a decrease to an increase as the end point R2 of the local concentration change α. This makes it possible to accurately calculate the proportion of recirculated blood by accurately detecting at least the end point R2 of the local concentration change α.

[0097] In the seventh embodiment of the present invention, in the sixth embodiment, the recirculation detection unit 17 sequentially calculates the blood concentration value on the graph after the specific peak P1 in the local concentration change α is detected, and identifies the point in time when the calculated blood concentration value on the graph becomes the minimum as the end point R2. This makes it possible to accurately identify the end point R2 of the local concentration change α by determining the minimum value after the specific peak P1 is detected.

[0098] In the eighth embodiment of the present invention, in the sixth embodiment, the recirculation detection unit 17 sequentially calculates the slope of the graph after the characteristic peak P1 in the local concentration change α is detected, and identifies the point in time at which the calculated slope of the graph becomes horizontal as the end point R2. This makes it possible to accurately identify the end point R2 of the local concentration change α by determining the slope of the graph after the characteristic peak P1 is detected.

[0099] In the ninth embodiment of the present invention, in the sixth embodiment, the recirculation detection unit 17 sequentially calculates the area of ​​the graph after a specific peak P1 in the local concentration change α is detected, and identifies the time point at which the rate of change in the calculated area of ​​the graph decreases as the end time point R2. This makes it possible to accurately identify the end time point R2 of the local concentration change α by calculating the area of ​​the graph after the specific peak P1 is detected.

[0100] A tenth embodiment of the present invention is any one of the first, fourth, and sixth embodiments, in which the recirculation detection unit detects recirculated blood and calculates the ratio of recirculated blood in a measurement process separate from the treatment process in which blood purification treatment is performed.

[0101] An eleventh embodiment of the present invention is the tenth embodiment, further comprising a switching input unit or an instruction input unit that can be operated by an operator, and the measurement process is performed as a predetermined process on the condition that the switching input unit or the instruction input unit is operated.

[0102] A twelfth aspect of the present invention is any one of the first, fourth, and sixth aspects, wherein the blood characteristic is blood concentration, thereby making it possible to detect recirculating blood based on changes in blood concentration and calculate the proportion of recirculating blood.

[0103] 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.

[0104] 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 characteristic change imparting unit that can impart a local characteristic change with a peak that is specific to the characteristic 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 then 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 ratio of the recirculated blood, wherein the recirculation detection unit detects a noise waveform detected just before the local characteristic change is detected, and identifies the start point of the local characteristic change based on the noise waveform.

2. The blood purification device according to claim 1, wherein the recirculation detection unit identifies the point at which the characteristic change changes from a decrease to an increase after detecting the peak of the noise waveform as the start point of the local characteristic change.

3. The blood purification device according to claim 2, wherein the recirculation detection unit sequentially detects the slope or area for each predetermined period in a graph showing the change in the characteristic over time or with the cumulative blood flow rate, and detects a decrease or increase in the change in the characteristic based on the detected change in the slope or change in the area.

4. 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 characteristic change imparting unit that can impart a local characteristic change in which 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 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 to the arterial blood circuit and flows therein, 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 ratio of the recirculated blood, wherein the recirculation detection unit sequentially searches back to the start of detection of the local characteristic change, using the time when a specific peak in the local characteristic change was detected as a reference, and identifies the time when the characteristic change changed from decreasing to increasing as the start time of the local characteristic change.

5. The blood purification device according to claim 4, wherein the recirculation detection unit sequentially detects the slope or area for each predetermined period in a graph showing the change in the characteristic over time or with the cumulative blood flow rate, and detects a decrease or increase in the change in the characteristic based on the detected change in the slope or change in the area.

6. 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 characteristic change imparting unit that can impart a local characteristic change in which 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 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 ratio of the recirculated blood, wherein the recirculation detection unit detects the amount of change in the local characteristic change over time or with the cumulative blood flow rate after the specific peak is detected, and identifies the point in time when the amount of change changes from a decrease to an increase as the end point of the local characteristic change.

7. The blood purification device according to claim 6, wherein the recirculation detection unit sequentially calculates the value of the blood characteristic of the graph after a specific peak in the local characteristic change is detected, and identifies the time when the calculated value of the blood characteristic of the graph becomes the minimum value as the end time.

8. A blood purification device as described in claim 6, wherein the recirculation detection unit sequentially calculates the slope of the graph after a specific peak in the local characteristic change is detected, and identifies the end point as the point at which the calculated slope of the graph becomes horizontal.

9. A blood purification device as described in claim 6, wherein the recirculation detection unit sequentially calculates the area of ​​the graph after a specific peak in the local characteristic change is detected, and identifies the point at which the rate of change in the calculated area of ​​the graph decreases as the end point.

10. A blood purification device as described in any one of claims 1, 4, and 6, wherein the recirculation detection unit detects recirculated blood and calculates the proportion of recirculated blood in a measurement process separate from the treatment process in which blood purification treatment is performed.

11. A blood purification device as described in claim 10, which is provided with a switching input unit or an instruction input unit that can be operated by an operator, and in which the measurement process is performed as a predetermined process conditional on input operation of the switching input unit or the instruction input unit.

12. A blood purification apparatus according to any one of claims 1, 4 and 6, wherein the blood characteristic is blood concentration.

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