Blood purification device

Abstract

To provide a blood purification device that can accurately determine whether a venipuncture has been performed correctly in a patient. [Solution] The blood purification device 1 comprises a blood purifier 3 capable of purifying blood, a blood circuit 2 having an arterial blood circuit 21 with an arterial puncture needle 211 attached to its tip and a venous blood circuit 22 with a venous puncture needle 221 attached to its tip, an impedance measuring unit 5 having an oscillator 53 that applies an AC voltage between an arterial electrode 51 provided on the arterial blood circuit 21 and a venous electrode 52 provided on the venous blood circuit 22, and capable of measuring the frequency characteristics of the impedance between the arterial electrode 51 and the venous electrode 52, and a puncture determination unit 72 that determines whether the patient has been properly punctured based on the measured impedance frequency characteristics, and further comprises a frequency range determination unit 70 that determines the frequency range of the AC voltage applied by the oscillator 53 according to the liquid in the blood circuit 2.

Description

Technical Field

[0001] The present invention relates to a blood purification device.

Background Art

[0002] Generally, in blood purification treatments such as dialysis treatment, a dialyzer is provided in a blood circuit that extracorporeally circulates a patient's blood, and dialysis fluid is introduced into or withdrawn from the dialyzer to perform blood purification treatment. Note that Patent Document 1 is available as prior art document information related to the invention of this application.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In blood purification treatment, it is necessary to puncture an arterial side puncture needle and a venous side puncture needle in a patient, collect the patient's blood from the arterial side puncture needle, perform blood purification treatment while extracorporeally circulating it in a blood circuit, and then return the purified blood to the patient from the venous side puncture needle. Therefore, it is desired to accurately determine whether the puncture of the arterial side puncture needle or the venous side puncture needle is being performed normally and improve safety.

[0005] Therefore, an object of the present invention is to provide a blood purification device capable of accurately determining whether a puncture in a patient is being performed normally.

Means for Solving the Problems

[0006] A blood purification device according to one embodiment of the present invention comprises a blood purifier capable of purifying blood, an arterial blood circuit having an arterial puncture needle attached to its tip and its proximal end connected to the blood purifier, and a venous blood circuit having a venous puncture needle attached to its tip and its proximal end connected to the blood purifier, for circulating the patient's blood extracorporeally, an impedance measuring unit having an oscillator that applies an alternating current voltage between an arterial electrode provided in the arterial blood circuit and a venous electrode provided in the venous blood circuit, and capable of measuring the frequency characteristics of the impedance between the arterial electrode and the venous electrode, and a puncture determination unit that determines whether the patient has been properly punctured based on the frequency characteristics of the impedance measured by the impedance measuring unit, and further comprises a frequency range determination unit that controls the frequency range of the alternating current voltage applied by the oscillator according to the liquid in the blood circuit. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a blood purification device that can accurately determine whether a puncture has been performed correctly on a patient. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram of a blood purification device according to one embodiment of the present invention. [Figure 2] Figures (a) to (c) show examples of arterial and venous electrodes. [Figure 3] (a) and (b) are diagrams showing examples of the frequency characteristics (impedance distribution) of impedance. [Figure 4] This is the control flow for determining whether a puncture was performed. [Modes for carrying out the invention]

[0009] [Embodiment] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0010] (Overall configuration of blood purification device 1) Figure 1 is a schematic diagram of the blood purification device 1 according to this embodiment. As shown in Figure 1, the blood purification device 1 comprises a blood circuit 2 for circulating the patient's blood outside the body, and a blood purifier 3 provided in the blood circuit 2 that is capable of purifying the blood.

[0011] The blood circuit 2 consists of a flexible tube through which a fluid such as blood flows. The blood circuit 2 has an arterial blood circuit 21 with an arterial puncture needle 211 attached to its tip that can be used to puncture a patient, and a venous blood circuit 22 with a venous puncture needle 221 attached to its tip that can be used to puncture a patient. The proximal ends of the arterial blood circuit 21 and the proximal ends of the venous blood circuit 22 are connected to the blood purifier 3. The arterial blood circuit 21 is equipped with a blood pump 23, which is a squeezing type pump for pumping the fluid in the blood circuit 2. The venous blood circuit 22 is equipped with a gas-liquid separator 24 for separating air bubbles from the fluid flowing through the blood circuit 2.

[0012] The blood purifier 3, also called a dialyzer, has a blood inlet port 3a, a blood outlet port 3b, a dialysate inlet port 3c, and a drain outlet port 3d. The proximal end of the arterial blood circuit 21 is connected to the blood inlet port 3a, and the proximal end of the venous blood circuit 22 is connected to the blood outlet port 3b. The dialysate inlet port 3c is connected to a dialysate inlet line 41 extending from the main body of the device 4, and the drain outlet port 3d is connected to a drain outlet line 42 extending from the main body of the device 4. Inside the blood purifier 3, multiple hollow fibers are housed, and the blood flows inside the hollow fibers, while the dialysate flows outside the hollow fibers. Numerous tiny pores are formed in the hollow fibers, allowing impurities in the blood to permeate into the dialysate. Furthermore, by discharging more drain fluid than dialysate, water is removed from the blood. Although not shown in the diagram, the blood circuit 2 may be equipped with a bubble detector, a pressure sensor, or the like as appropriate.

[0013] (Impedance measurement unit 5) The blood purification device 1 includes an impedance measuring unit 5 capable of measuring the frequency characteristics of the impedance of the liquid in the blood circuit. The impedance measuring unit 5 includes an arterial electrode 51 provided in the arterial blood circuit 21, a venous electrode 52 provided in the venous blood circuit 22, an oscillator 53 that applies an AC voltage between the arterial electrode 51 and the venous electrode 52 and can switch the frequency of the AC voltage, and an impedance measuring instrument 54 that measures the impedance between the arterial electrode 51 and the venous electrode 52 at each frequency.

[0014] Here, the arterial electrode 51 is provided in the arterial blood circuit 21 between the blood pump 23 and the arterial puncture needle 211. The venous electrode 52 is provided in the venous blood circuit 22 between the gas-liquid separator 24 and the venous puncture needle 221. As shown in Figure 2(a), the arterial electrode 51 and the venous electrode 52 consist of cylindrical conductors connected to the flexible tubes that constitute the blood circuit 2. For example, the arterial electrode 51 and the venous electrode 52 are electrically connected to the oscillator 53 by attaching clips from clip-equipped wires extending from the oscillator 53 to the arterial electrode 51 and the venous electrode 52. The specific shapes of the arterial electrode 51 and the venous electrode 52 are not limited to those shown in the figure; they can be any shape that can apply voltage to the liquid flowing in the blood circuit 2, and the electrode structure may not directly touch the liquid. More specifically, the arterial electrode 51 and the venous electrode 52 may be, for example, cylindrical electrode structures provided to surround the flexible tube constituting the blood circuit 2, as shown in Figure 2(b), or electrode structures with two metal plates sandwiching the flexible tube constituting the blood circuit 2, as shown in Figure 2(c). By making the arterial electrode 51 and the venous electrode 52 electrode structures that do not directly come into contact with the liquid, obstruction of the flow of liquid in the blood circuit 2 can be suppressed, and metals with low biocompatibility can be used as electrodes. Note that the electrode structures shown are merely examples, and the electrode structures of the arterial electrode 51 and the venous electrode 52 can be changed as appropriate.

[0015] The oscillator 53 applies an alternating voltage between the arterial-side electrode 51 and the venous-side electrode 52. Further, the oscillator 53 is configured to be able to appropriately change the frequency of the applied alternating voltage from a low frequency (for example, several tens of Hz) to a high frequency (for example, several MHz). The frequency of the alternating voltage applied by the oscillator 53 is determined by a frequency range determination unit 70 described later.

[0016] The impedance measuring device 54 measures the impedance between the arterial-side electrode 51 and the venous-side electrode 52 when an alternating voltage is applied by the oscillator 53. By measuring the impedance with the impedance measuring device 54 while changing the frequency of the alternating voltage applied by the oscillator 53, the impedance for each frequency can be measured. The impedance between the arterial-side electrode 51 and the venous-side electrode 52 measured by the impedance measuring device 54 changes depending on whether or not the patient has been punctured.

[0017] (Hematocrit value detection sensor 9) In the blood purification device 1 according to the present embodiment, the blood circuit 2 is provided with a hematocrit value detection sensor 9 that detects the hematocrit value of the liquid in the blood circuit 2. The detection method of the hematocrit value detection sensor 9 is not particularly limited, and for example, a detection method using an electrochemical measurement technique, an optical detection method, or the like can be used. The hematocrit value is a value representing the ratio of the total volume of red blood cells in the total blood (liquid).

[0018] In blood purification treatment, the hematocrit value of the liquid in the blood circuit 2 changes depending on the situation. For example, at the start of blood withdrawal, since the liquid in the blood circuit 2 changes from physiological saline to blood, the hematocrit value increases. Conversely, at the start of blood return, since the liquid in the blood circuit 2 changes from blood to physiological saline, the hematocrit value decreases. Also, during emergency fluid infusion, since physiological saline is added to the blood in the blood circuit 2, the hematocrit value decreases. Similarly, when performing blood purification treatment accompanied by fluid infusion, the hematocrit value temporarily decreases at the timing of fluid infusion.

[0019] If the hematocrit value of the liquid in the blood circuit 2 changes significantly, the impedance between the arterial side electrode 51 and the venous side electrode 52 will change. As a result, there is a risk that the detection of the frequency characteristics of the impedance will not be performed normally, and there is a risk that the determination of puncture (determination of whether the puncture of the patient is performed normally) described later will not be performed normally. Therefore, in the present embodiment, according to the liquid in the blood circuit 2 (more specifically, according to the hematocrit value of the liquid in the blood circuit 2), by appropriately adjusting the frequency range when measuring the frequency characteristics of the impedance, it is possible to accurately determine whether the puncture is performed normally. Details of this point will be described later.

[0020] (Control device 6) The blood purification device has a control device 6 that controls blood purification treatment and the like. The control device 6 has a control unit 7 and a storage unit 8. The control unit 7 is realized by appropriately combining an arithmetic element, a memory, a storage device, software, an interface, and the like. The storage unit 8 is realized by a memory or a storage device. The control unit 7 has a frequency range determination unit 70, a frequency characteristic acquisition unit 71, a puncture determination unit 72, and an abnormality notification unit 73.

[0021] (Frequency range determination unit 70) 2]]The frequency range determination unit 70 controls the frequency range of the AC voltage applied by the oscillator 53 when measuring the frequency characteristics of the impedance according to the liquid in the blood circuit 2 (according to the type of the liquid and the state of the liquid). In the present embodiment, the frequency range determination unit 70 controls the frequency range of the AC voltage applied by the oscillator 53 according to the hematocrit value of the liquid in the blood circuit 2 detected by the hematocrit value detection sensor 9. <

[0022] The relationship between the hematocrit value and the frequency range of the AC voltage suitable for measuring the impedance frequency characteristics should be determined in advance through experiments or other means. For example, by first determining the relationship between the hematocrit value and the median (or minimum or maximum) value of the frequency range, and then using this relationship to determine the median (or minimum or maximum) value of the frequency range corresponding to the measured hematocrit value, the frequency range can be determined. Note that the specific method for determining the frequency range according to the hematocrit value can be modified as appropriate.

[0023] (Frequency characteristic acquisition unit 71) The frequency response acquisition unit 71 performs a frequency response acquisition process to acquire the frequency response of the impedance based on the impedance measured for each frequency by the impedance measuring instrument 54. The frequency response acquisition unit 71 controls the frequency of the oscillator 53, acquires the impedance measurement results from the impedance measuring instrument 54, and stores them in the measurement result storage unit 81. At this time, the frequency response of the impedance is measured in the frequency range determined by the frequency range determination unit 70, that is, the frequency range corresponding to the hematocrit value. Then, the frequency response acquisition unit 71 obtains the frequency response of the impedance based on the impedance measurement results for each frequency stored in the measurement result storage unit 81. The obtained impedance frequency response is stored in the measurement frequency response storage unit 82.

[0024] In this embodiment, an impedance distribution, which shows the relationship between the resistive and capacitive components of impedance, is used as the frequency characteristic of impedance. More specifically, as shown in Figure 3(a), the impedance distribution is a plot of the resistive and capacitive components of impedance at each measured frequency, with the resistive component value on the horizontal axis and the capacitive component value on the vertical axis. This impedance distribution (i.e., the frequency characteristic of impedance) changes depending on the state of puncture in the patient. Therefore, by comparing the impedance distribution when puncture is performed normally with the measured impedance distribution, it is possible to determine whether puncture has been performed normally in the patient.

[0025] For example, if the arterial electrode 51 or venous electrode 52 is not properly inserted for any reason, the impedance frequency characteristics will change from the initial distribution shown in Figure 3(a) to the distribution shown in Figure 3(b). Therefore, by determining whether the change in the impedance frequency characteristics exceeds a certain level, it is possible to determine that the arterial puncture needle 211 or venous puncture needle 221 has not properly inserted into the blood vessel. Note that the vertical and horizontal axes of the impedance distribution may be swapped, and the resistance component of the impedance may be on the vertical axis and the capacitance component on the horizontal axis.

[0026] (Puncture detection unit 72, normal frequency characteristic memory unit 83) The normal frequency characteristics memory unit 83 stores the impedance frequency characteristics (hereinafter referred to as the normal impedance frequency characteristics) when the puncture to the patient is performed normally. It is known that the impedance frequency characteristics also change depending on the type of fluid flowing through the blood circuit 2, so it is more desirable to store the normal impedance frequency characteristics (impedance distribution) for each fluid flowing through the blood circuit 2 in the normal frequency characteristics memory unit 83.

[0027] The puncture determination unit 72 compares the frequency characteristics of the impedance measured by the impedance measurement unit 5 (i.e., the frequency characteristics of the impedance stored in the measured frequency characteristics storage unit 82 by the frequency characteristics acquisition unit 71) with the frequency characteristics of the impedance under normal conditions stored in the normal frequency characteristics storage unit 83, and determines whether they match.

[0028] In this embodiment, the puncture determination unit 72 is configured to measure the frequency characteristics of the impedance at predetermined time intervals and to determine whether the measured impedance frequency characteristics match those of a normal impedance. This configuration makes it possible to detect, for example, cases where the puncture becomes abnormal due to body movement during blood purification therapy, thereby improving safety.

[0029] The puncture determination unit 72 compares the impedance distributions shown in Figures 3(a) and 3(b) to determine whether the frequency characteristics of the measured impedance match those of the normal impedance. More specifically, the puncture determination unit 72 determines that the two do not match when the change in the frequency characteristics of the measured impedance (the difference between the two) relative to the frequency characteristics of the normal impedance exceeds a certain level.

[0030] Furthermore, the puncture determination unit 72 may make a determination by utilizing the mutual correlation between the resistive and capacitive components that constitute the frequency characteristics of the impedance. For example, if we let R be the resistive component, C be the capacitive component, and x be the frequency at the time of measurement, and let Rref(x) be the resistive component and Cref(x) be the capacitive component in the normal frequency characteristics, and let Rcur(x) be the resistive component and Ccur(x) be the capacitive component in the measured frequency characteristics, then the following relationships (1) and (2) can be obtained. In equations (1) and (2) below, a and b are the lowest and highest frequencies output by the oscillator 53.

[0031]

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[0032]

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[0033] The closer the values ​​of R and C obtained in equations (1) and (2) above are to 0, the closer the frequency characteristics of the measured impedance are to the frequency characteristics of the normal impedance. Therefore, if either or both of the values ​​of R and C obtained in equations (1) and (2) above exceed a preset threshold, it can be determined that the frequency characteristics of the measured impedance do not match the frequency characteristics of the normal impedance. Note that the determination method by the puncture determination unit 72 is not limited to the above, and determination may be made using other pattern matching methods, etc.

[0034] (Anomaly Notification Unit 73) The abnormality notification unit 73 notifies the user or administrator of the abnormality when the puncture determination unit 72 determines that the results do not match. The abnormality notification unit 73 may notify the administrator of the abnormality by sound or light, such as by using a buzzer or warning light, or by displaying a message notifying the administrator of the abnormality on a display unit provided in the blood purification device 1, or by sending an email or the like to the administrator.

[0035] (Control flow during puncture detection) Figure 4 shows the control flow during puncture evaluation. The control flow in Figure 4 is executed when determining whether the puncture was performed correctly. For example, the control flow in Figure 4 is executed at predetermined time intervals during blood purification therapy.

[0036] First, in step S1, the hematocrit value of the fluid in the blood circuit 2 is measured by the hematocrit value detection sensor 9. The measured hematocrit value is acquired by the frequency range determination unit 70 and stored in the memory unit 8. Then, in step S2, the frequency range determination unit 70 determines the frequency range of the AC voltage applied when measuring the impedance frequency characteristics, based on the hematocrit value measured in step S1.

[0037] Subsequently, in step S3, the frequency response acquisition unit 71 uses the impedance measurement unit 5 to measure the impedance while changing the frequency of the voltage applied by the oscillator 53 within the frequency range determined in step S2. The measured impedance for each frequency is stored in the measurement result storage unit 81. Then, in step S4, the frequency response acquisition unit 71 obtains the impedance frequency characteristics (impedance distribution shown in Figures 3(a) and (b)) based on the impedance measurement results for each frequency stored in the measurement result storage unit 81. The obtained impedance frequency characteristics are stored in the measurement frequency characteristics storage unit 82.

[0038] Subsequently, in step S5, the puncture determination unit 72 compares the impedance frequency characteristics obtained in step S4 with the normal impedance frequency characteristics stored in the normal frequency characteristics memory unit 83 to determine if they match. At this time, it is preferable to select an impedance frequency characteristic corresponding to the type of fluid in the blood circuit 2 as the normal impedance frequency characteristics. The type of fluid in the blood circuit 2 can be estimated from the hematocrit value. If Yes (Y) is determined in step S5, the process ends without issuing an abnormality notification. If No (N) is determined in step S5, the abnormality notification unit 73 issues an abnormality notification in step S6. After that, the process ends.

[0039] (Operation and Effects of the Embodiment) As described above, the blood purification device 1 according to this embodiment is equipped with a frequency range determination unit 70 that determines the frequency range of the AC voltage applied by the oscillator 53 according to the liquid in the blood circuit 2. This makes it possible to suppress problems such as inability to accurately measure impedance due to changes in the liquid in the blood circuit 2, and makes it possible to measure the frequency characteristics of impedance in an appropriate frequency range according to the liquid in the blood circuit 2. As a result, it becomes possible to accurately determine whether the puncture has been performed correctly on the patient, thereby improving safety.

[0040] Furthermore, the blood purification device 1 according to this embodiment is equipped with a hematocrit value detection sensor 9 that detects the hematocrit value of the liquid in the blood circuit 2, and the frequency range determination unit 70 determines the frequency range of the AC voltage applied by the oscillator 53 according to the hematocrit value of the liquid in the blood circuit 2 detected by the hematocrit value detection sensor 9. As a result, even when the blood concentration changes, it becomes possible to accurately measure the frequency characteristics of impedance using a frequency range suitable for impedance measurement.

[0041] (Summary of the embodiments) Next, the technical concept understood from the embodiments described above will be described using the reference numerals and other symbols from the embodiments. However, the reference numerals and other symbols in the following description are not limited to the components in the claims that are specifically shown in the embodiments.

[0042] [1] A blood circuit (2) for extracorporeal circulation of the patient's blood, comprising: a blood purifier (3) capable of purifying blood; an arterial blood circuit (21) with an arterial puncture needle (211) attached to its tip and its proximal end connected to the blood purifier (3); and a venous blood circuit (22) with a venous puncture needle (221) attached to its tip and its proximal end connected to the blood purifier (3); and an arterial electrode (51) provided on the arterial blood circuit (21) and a venous electrode (52) provided on the venous blood circuit (22) A blood purification device (1) comprising: an impedance measuring unit (5) having an oscillator (53) that applies an AC voltage in between, capable of measuring the frequency characteristics of the impedance between the arterial electrode (51) and the venous electrode (52); a puncture determination unit (72) that determines whether the patient has been properly punctured based on the frequency characteristics of the impedance measured by the impedance measuring unit (5); and a frequency range determination unit (70) that determines the frequency range of the AC voltage applied by the oscillator (53) according to the liquid in the blood circuit (2).

[0043] [2] The blood purification device (1) according to [1], comprising a hematocrit value detection sensor (9) for detecting the hematocrit value of the liquid in the blood circuit (2), wherein the frequency range determination unit (70) determines the frequency range of the AC voltage applied by the oscillator (53) according to the hematocrit value of the liquid in the blood circuit (2) detected by the hematocrit value detection sensor (9).

[0044] Although embodiments of the present invention have been described above, the embodiments described above do not limit the invention as defined in the claims. Furthermore, it should be noted that not all combinations of features described in the embodiments are necessarily essential for solving the problem of the invention. In addition, the present invention can be implemented with appropriate modifications without departing from its spirit. [Explanation of Symbols]

[0045] 1…Blood purification device 2…Blood circuit 21…Arterial blood circuit 211…Arterial side puncture needle 22…Venous blood circuit 221... Venous puncture needle 3… Blood purifier 5…Impedance measurement section 51...Arterial side electrode 52…Venous side electrode 53…Oscillator 54…Impedance meter 6...Control device 7…Control Unit 70...Frequency range determination unit 71...Frequency response acquisition unit 72...Puncture determination unit 73... Abnormal Information Department 8...Storage section 81…Measurement result storage unit 82…Measurement frequency characteristic storage section 83...Normal frequency response memory unit 9…Hematocrit value detection sensor

Claims

[Claim 1] A blood purifier capable of purifying blood, A blood circuit for extracorporeal circulation of the patient's blood has an arterial blood circuit with an arterial puncture needle attached to its tip and its base connected to the blood purifier, and a venous blood circuit with a venous puncture needle attached to its tip and its base connected to the blood purifier, An impedance measuring unit having an oscillator that applies an AC voltage between the arterial electrode provided in the arterial blood circuit and the venous electrode provided in the venous blood circuit, and capable of measuring the frequency characteristics of the impedance between the arterial electrode and the venous electrode, The system includes a puncture determination unit that determines whether the patient has been properly punctured based on the frequency characteristics of the impedance measured by the impedance measurement unit, Furthermore, it includes a frequency range determination unit that determines the frequency range of the AC voltage applied by the oscillator according to the liquid in the blood circuit. The system includes a hematocrit value detection sensor that detects the hematocrit value of the fluid in the blood circuit, The frequency range determination unit determines the frequency range of the AC voltage applied by the oscillator according to the hematocrit value of the liquid in the blood circuit detected by the hematocrit value detection sensor. Blood purification device.

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