Blood purification device

Abstract

A blood purification device (1) comprises: a blood purifier (3) capable of purifying blood; a blood circuit (2) including an arterial-side blood circuit (21) which has an arterial-side puncture needle (211) attached on the distal end thereof, and a venous-side blood circuit (22) which has a venous-side puncture needle (221) attached on the distal end thereof; an impedance measurement unit (5) including an oscillator (53) that applies an alternating-current voltage across an arterial-side electrode (51) provided to the arterial-side blood circuit (21) and a venous-side electrode (52) provided to the venous-side blood circuit (22), the impedance measurement unit being capable of measuring frequency characteristics of the impedance between the arterial-side electrode (51) and the venous-side electrode (52); and a puncture determination unit (72) for determining, on the basis of the measured frequency characteristics of the impedance, whether a patient has been punctured normally. The blood purification device also comprises a frequency range determination unit (70) for determining the frequency range of the alternating-current voltage applied by the oscillator (53) in accordance with the liquid in the blood circuit (2).

Description

Blood purification device

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

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in a blood circuit that extracorporeally circulates a patient's blood, and dialysis fluid is introduced into or withdrawn from the dialyzer to perform a blood purification treatment.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

[0003] U.S. Patent Application Publication No. 2008 / 0195021

[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.

[0006] A blood purification device according to an embodiment of the present invention includes a blood purifier capable of purifying blood, an arterial side blood circuit having an arterial side puncture needle capable of puncturing a patient attached to its tip and a base end connected to the blood purifier, a venous side blood circuit having a venous side puncture needle capable of puncturing a patient attached to its tip and a base end connected to the blood purifier, a blood circuit for extracorporeally circulating a patient's blood, an oscillator for applying an alternating voltage between an arterial side electrode provided in the arterial side blood circuit and a venous side electrode provided in the venous side blood circuit, an impedance measurement unit capable of measuring the frequency characteristics of the impedance between the arterial side electrode and the venous side electrode, and a puncture determination unit for determining whether a patient has been normally punctured based on the frequency characteristics of the impedance measured by the impedance measurement unit. Further, a frequency range determination unit for controlling the frequency range of the alternating voltage applied by the oscillator according to the liquid in the blood circuit is provided.

[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.

[0008] This is a schematic diagram of a blood purification device according to one embodiment of the present invention. This is a diagram showing an example of arterial and venous electrodes. This is a diagram showing an example of arterial and venous electrodes. This is a diagram showing an example of the frequency characteristics (impedance distribution) of impedance. This is a diagram showing an example of the frequency characteristics (impedance distribution) of impedance. This is the control flow during puncture determination.

[0009] [Embodiments] Hereinafter, embodiments of the present invention will be described with reference to the attached 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 the dialysate supply, 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 is equipped with an impedance measurement unit 5 capable of measuring the frequency characteristics of the impedance of the liquid in the blood circuit. The impedance measurement 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 2A, the arterial electrode 51 and the venous electrode 52 consist of cylindrical conductors connected to the flexible tube that constitutes the blood circuit 2. For example, the arterial electrode 51 and the venous electrode 52 are electrically connected to the oscillator 53 by attaching the clips of the clipped 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, and any shape that can apply voltage to the liquid flowing in the blood circuit 2 is acceptable, 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 2B, or electrode structures with two metal plates sandwiching the flexible tube constituting the blood circuit 2, as shown in Figure 2C. 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 current voltage between the arterial electrode 51 and the venous electrode 52. The oscillator 53 is also configured to appropriately change the frequency of the applied alternating current voltage from a low frequency (e.g., several tens of Hz) to a high frequency (e.g., several MHz). The frequency of the alternating current voltage applied by the oscillator 53 is determined by the frequency range determination unit 70, which will be described later.

[0016] The impedance meter 54 measures the impedance between the arterial electrode 51 and the venous electrode 52 when an AC voltage is applied by the oscillator 53. By changing the frequency of the AC voltage applied by the oscillator 53 and measuring the impedance with the impedance meter 54, the impedance for each frequency can be measured. The impedance between the arterial electrode 51 and the venous electrode 52 measured by the impedance meter 54 changes depending on whether or not a puncture is performed on the patient.

[0017] (Hematocrit Value Detection Sensor 9) In the blood purification device 1 according to this embodiment, the blood circuit 2 is equipped with a hematocrit value detection sensor 9 for detecting 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 method or an optical detection method can be used. The hematocrit value is a value that represents the ratio of the total volume of red blood cells to the total blood (liquid).

[0018] In blood purification therapy, the hematocrit value of the fluid in blood circuit 2 changes depending on the situation. For example, at the start of blood withdrawal, the hematocrit value increases because the fluid in blood circuit 2 changes from saline to blood. Conversely, at the start of blood return, the hematocrit value decreases because the fluid in blood circuit 2 changes from blood to saline. Also, during emergency fluid replacement, the hematocrit value decreases because saline is added to the blood in blood circuit 2. Similarly, when performing blood purification therapy with fluid replacement, the hematocrit value temporarily decreases at the time of fluid replacement.

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

[0020] (Control device 6) The blood purification device 1 is equipped with a control device 6 that controls blood purification treatment, etc. The control device 6 has a control unit 7 and a storage unit 8. The control unit 7 is realized by appropriately combining computing elements, memory, storage device, software, interface, etc. The storage unit 8 is realized by memory and 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) The frequency range determination unit 70 controls the frequency range of the AC voltage applied by the oscillator 53 when measuring the impedance frequency characteristics, according to the liquid in the blood circuit 2 (depending on the type of liquid and the state of the liquid). In this 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 Response 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, in 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 3A, the impedance distribution is a plot of the resistive and capacitive components of impedance for 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 3A to the distribution shown in Figure 3B. 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 been 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 determination unit 72, normal frequency characteristic memory unit 83) The normal frequency characteristic memory unit 83 stores the impedance frequency characteristics when the puncture to the patient is performed normally (hereinafter referred to as the normal impedance frequency characteristics). 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 characteristic 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 frequency characteristics of the impedance match those of a normal patient. 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 3A and 3B 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 relationship between the resistive component and the capacitive component 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 if we let Rref(x) be the resistive component and Cref(x) be the capacitive component in the normal frequency characteristics, and Rcur(x) be the resistive component and Ccur(x) be the resistive component in the measured frequency characteristics, then we can obtain the following relationships (1) and (2). In equations (1) and (2) below, a and b are the lowest and highest frequencies output by the oscillator 53.

[0031]

[0032]

[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 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) When the puncture determination unit 72 determines that the results do not match, the abnormality notification unit 73 notifies the user or administrator of the abnormality. 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 an abnormality notification message 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 determination) Figure 4 shows the control flow during puncture determination. The control flow in Figure 4 is executed when determining whether the puncture has been 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 storage unit 8. Then, in step S2, the frequency range determination unit 70 determines the frequency range of the AC voltage to be applied when measuring the frequency characteristics of the impedance, based on the hematocrit value measured in step S1.

[0037] Subsequently, in step S3, the frequency characteristic 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 characteristic acquisition unit 71 obtains the impedance frequency characteristics (impedance distribution shown in Figures 3A and 3B) 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 characteristic 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 storage 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 Embodiments) Next, the technical concept understood from the embodiments described above will be described using the reference numerals, etc., from the embodiments. However, the reference numerals, etc., in the following description are not limited to the components in the claims that are specifically shown in the embodiments.

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

[0043] [2] The blood purification apparatus (1) according to [1], further 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 alternating 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] As described above, the embodiments of the present invention have been described. However, the embodiments described above do not limit the invention according to the claims. Also, it should be noted that not all combinations of features described in the embodiments are essential means for solving the problems of the invention. Further, the present invention can be appropriately modified and implemented without departing from its gist.

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

Claims

1. A blood purification device comprising: a blood purifier capable of purifying blood; an arterial blood circuit having an arterial puncture needle attached to its tip and connected to the blood purifier at its base, and a venous blood circuit having a venous puncture needle attached to its tip and connected to the blood purifier at its base, for extracorporeal circulation of the patient's blood; 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; 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 comprising a frequency range determination unit that determines the frequency range of the alternating current voltage applied by the oscillator according to the liquid in the blood circuit.

2. The blood purification apparatus according to claim 1, comprising a hematocrit value detection sensor for detecting the hematocrit value of the liquid in the blood circuit, wherein 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.

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