Needle removal detection device

Abstract

Provided is a needle removal detection device 100 having an electrode 2 that can be attached in close contact with the outer circumferential surface of a tube even when the diameter of the tube varies. For this purpose, the electrode 2, which is detachably attached to the outer circumferential surface of the tube 8 connected to a puncture needle 7, is formed of an elastically deformable conductive material and is attached by being pressed against the outer circumferential surface of the tube 8 such that the electrode 2 undergoes elastic deformation.

Description

Needle dislodgement detection device

[0001] The present invention relates to a needle dislodgement detection device.

[0002] Conventionally, a needle dislodgement detection device has been conceived for detecting that an arterial puncture needle or a venous puncture needle has been dislodged from a patient in a hemodialysis apparatus. The principle thereof is that an alternating voltage is applied to an extracorporeal blood circuit formed with the arterial puncture needle and the venous puncture needle as respective ends, and needle dislodgement is detected on the basis of a measurement signal of the current flowing at that time.

[0003] In order to apply an alternating voltage to the aforementioned extracorporeal blood circuit, for example, in Patent Document 1, electrodes are detachably attached from the outside to respective predetermined positions on an arterial-side tube and a venous-side tube that constitute the extracorporeal blood circuit, and an alternating voltage is applied between these electrodes.

[0004] This method has the advantage that, since the electrodes are retrofitted to the tubes, the method can be used in common for various hemodialysis apparatuses having different puncture needle shapes and the like. Furthermore, since the electrodes are detachable, there is also the advantage that manufacturing costs can be reduced compared to a configuration in which electrodes are integrally incorporated in disposable extracorporeal blood circuit constituent components (e.g., puncture needles, tubes, etc.).

[0005] On the other hand, since the distance between the blood and the electrodes is increased by the thickness of the tube, the current measurement signal tends to be weak, and in order to solve this, it is necessary to bring the electrodes into close contact with the tube as much as possible. For example, in Patent Document 1, the electrodes are formed in a tubular shape that comes into close contact with the outer circumferential surface of the tube.

[0006] However, with the above-described configuration, it is necessary to prepare electrodes for each tube of different diameter.

[0007] Japanese Patent No. 7610857

[0008] Accordingly, the present invention has been made to solve the above problems, and an object thereof is to provide a needle dislodgement detection device having electrodes that can be attached in close contact with the outer circumferential surface of a tube even when the diameter of the tube changes.

[0009] In other words, the needle removal detection device according to the present invention has the following configuration.

[0010] [1] A needle removal detection device for detecting when an arterial or venous puncture needle of a hemodialysis machine has been withdrawn from a patient, comprising: a pair of electrodes detachably attached to the outer circumferential surfaces of an arterial tube connected to the arterial puncture needle and a venous tube connected to the venous puncture needle, respectively; a voltage application unit for applying a predetermined voltage between the electrodes; a current measurement unit for measuring the current flowing between the electrodes due to the application of the voltage; and a needle removal detection unit for detecting the withdrawal of the arterial or venous puncture needle based on a current measurement signal output by the current measurement unit, wherein the electrodes are made of an elastically deformable conductive material and are attached by being pressed against the outer circumferential surface of the tube so as to undergo elastic deformation.

[0011] With this configuration, even if the tube diameter changes, the electrode itself elastically deforms to adhere closely to the outer surface of the tube, allowing the same electrode to be attached closely to tubes of various different diameters. Therefore, it is no longer necessary to prepare electrodes according to the tube diameter, as in the past, and parts can be standardized. In addition, because the electrode adheres closely to the tube, the same needle detection accuracy as in the past can be guaranteed.

[0012] [2] The needle removal detection device according to [1], wherein the voltage application unit applies a high-frequency voltage between the electrodes, and the needle removal detection unit detects the removal of the arterial puncture needle or the venous puncture needle based on an extracted signal obtained by extracting a predetermined frequency component from the current measurement signal.

[0013] With this type of device, various types of noise superimposed on the current measurement signal, such as noise caused by vibrations from the blood pump in a hemodialysis machine or noise caused by a person touching the tube, can be effectively removed, thereby improving the accuracy of needle removal detection.

[0014] [3] The needle removal detection device according to [1] or [2], wherein the electrode is composed of a plurality of electrode segments, and when attached to the tube, each electrode segment is configured to clamp the tube from the surroundings.

[0015] With this type of device, electrodes can be easily attached to the tube even after the puncture has been performed.

[0016] [4] The needle removal detection device according to any one of [1] to [3], wherein the electrode segment is held by a plurality of holders that have higher rigidity than the electrode segment, and the electrode is configured to be in the mounted state by engaging each of the holders with each other.

[0017] Because the electrode segments are elastically deformable, it is difficult to stably attach them to the tube on their own. However, a highly rigid holder allows each electrode segment to be securely attached to the tube by clamping it from all sides.

[0018] [5] The electrode is composed of a pair of electrode divisions, and in the mounting state, these electrode divisions clamp the tube from opposing directions, as described in [3] or [4], the needle removal detection device.

[0019] Since the number of electrode divisions is minimized, the structure can be simplified and costs can be reduced.

[0020] According to the present invention configured in this way, it is possible to provide a needle extraction detection device having an electrode that can be attached in close contact with the outer circumferential surface of a tube, even if the diameter of the tube changes.

[0021] This is a schematic diagram showing the configuration of a needle removal detection device according to one embodiment of the present invention. This is an exploded perspective view showing the electrode and its attachment device according to the same embodiment. This is a perspective view showing the state before the electrode is attached to the tube and the state after the electrode is attached to the tube according to the same embodiment. This is a cross-sectional view showing the state before the electrode is attached to the tube and the state after the electrode is attached to the tube according to the same embodiment. This is a flowchart showing the needle removal detection method according to the same embodiment. This is a drawing of the electrode according to another embodiment of the present invention, viewed from the direction of extension of the tube. This is a drawing of the electrode according to yet another embodiment of the present invention, viewed from the direction of extension of the tube. This is a drawing of the electrode and attachment device according to yet another embodiment of the present invention, viewed from the direction of extension of the tube. This is a drawing of the electrode and attachment device according to yet another embodiment of the present invention, viewed from the direction of extension of the tube.

[0022] An embodiment of the needle removal detection device according to the present invention will be described below with reference to the drawings. Note that the drawings may be simplified or exaggerated for ease of understanding. Furthermore, identical components are denoted by the same reference numerals, and their descriptions are omitted as appropriate.

[0023] The needle removal detection device 100 of this embodiment detects when an arterial puncture needle 7(1) or a venous puncture needle 7(2) used in a hemodialysis machine 10 has been removed from the patient.

[0024] Section 1: Explanation of the Hemodialysis Machine Before explaining the needle removal detection device 100, we will first explain the overview of the hemodialysis machine 10.

[0025] As shown in Figure 1, this hemodialysis apparatus 10 comprises a dialyzer 11 for performing hemodialysis, an extracorporeal blood circuit 12 connected to the dialyzer 11 and for circulating blood, and a dialysate circuit 13 connected to the dialyzer 11 and for circulating dialysate. The extracorporeal blood circuit 12 has an arterial side channel 12a and a venous side channel 12b. The arterial side channel 12a is formed by an arterial puncture needle 7(1) and an arterial tube 8(1) connected to the arterial puncture needle 7(1) and the dialyzer 11. In the figure, reference numeral 14c denotes a blood pump provided in the arterial tube 8(1). The venous side channel 12b is formed by a venous puncture needle 7(2) and a venous tube 8(2) connected to the venous puncture needle 7(2) and the dialyzer 11. In the figure, reference numeral 15c denotes a drip chamber for removing air from the blood.

[0026] Section 2: Explanation of the Needle Removal Detection Device

[0027] 1. Overview As shown in Figure 1, the needle removal detection device 100 comprises an arterial electrode 2(1) detachably attached to an arterial tube 8(1), a venous electrode 2(2) detachably attached to a venous tube 8(2), a voltage application unit 4 that applies a high-frequency voltage between these electrodes 2(1) and 2(2), a current measurement unit 5 that detects the current flowing between the electrodes 2(1) and 2(2) to which the high-frequency voltage has been applied by the voltage application unit 4, and a control calculation unit 6 that detects the removal or withdrawal of the arterial puncture needle 7(1) or the venous puncture needle 7(2) based on the current measurement signal obtained by the current measurement unit 5.

[0028] In the following, the arterial electrode 2(1) and venous electrode 2(2) may simply be referred to as electrode 2 if there is no need to distinguish between the arterial and venous sides. The same applies to the arterial tube 8(1), venous tube 8(2), arterial puncture needle 7(1), and venous puncture needle (2).

[0029] 2. Regarding the electrodes, the arterial electrode 2(1) is detachably attached to the arterial tube 8(1), more specifically, on the arterial puncture needle 7(1) side of the blood pump 14c in the arterial tube 8(1), using an attachment device 9.

[0030] The venous electrode 2(2) is detachably attached to the venous tube 8(2), more specifically, to the venous puncture needle 7(2) side of the drip chamber 15c in the venous tube 8(2) using an attachment device 9.

[0031] However, in this embodiment, the electrode 2 is formed of a conductive elastic member, more specifically, conductive silicone rubber. Note that the conductive elastic member is not limited to one formed from a single material, such as the conductive silicone rubber; it may also be a composite material in which an elastically deformable insulating elastic member (e.g., polyurethane foam) is covered with a stretchable conductive fabric.

[0032] This will be explained in detail. As shown in Figures 2 to 4, the electrode 2 is composed of a pair of electrode divisions 21. Flat portions 21a are formed on the opposing surfaces of these electrode divisions 21. The tube 8 is clamped and fixed between these flat portions 21a.

[0033] The attachment device 9 is made of a non-conductive resin with higher rigidity than the tube, and is formed from a pair of retainers 91, as shown in the figure. In the following description, when it is necessary to distinguish between the retainers, they may be denoted as 91(1) and 91(2).

[0034] The holder 91 is a housing-like structure with an opening 91a on one surface. The electrode segment 21 is housed and held within the holder 91 without rattling, such that its flat portion 21a is flush with the opening 91a. In addition, the holder 91 has two opposing notches 91b formed on the surrounding plate that forms the opening 91a.

[0035] One holder 91(1) has an engaging portion 91c, and the other holder 91(2) has an engaged portion 91d. When these engaging portions 91c and 91d engage, each holder 91 engages with the openings 91a of each other in close proximity or in close contact. In this embodiment, the holders 91 are connected by a hinge 92 so that they can be opened and closed, and the engaging portion 91c and 91d are provided at opposing positions on the hinge 92.

[0036] Next, we will explain the procedure for attaching the electrode 2 to the tube 8 using such an attachment device 9.

[0037] First, as shown in Figure 2, the holders 91 are engaged with each other, and the electrode division 21 is fitted into the holder 91 through the opening 91a.

[0038] Next, as shown in Figures 3(a) and 4(a), the holders 91 are positioned so that they can hold the tube 8. Then, the holders 91 are gradually brought closer together to hold the tube 8. At this time, the tube 8 is positioned on the notch 91b.

[0039] When the holders 91 are brought even closer together from this state, the electrode segment 21 is pressed against the side surface of the tube 8 and begins to elastically deform, causing the flat portion 21a to begin to recess along the tube 8. The recessed portion reduces the thickness of the electrode 2 (electrode segment 21), i.e., the dimension along the clamping direction. Then, when the engagement state (mounting state) shown in Figures 3(b) and 4(b) is reached, the electrode segment 21 adheres tightly to almost the entire circumference of the side surface of the tube 8. The tube 8, sandwiched between the electrodes 2, also extends outward through the notch 91b.

[0040] When the tube 8 is clamped in this manner, the tube 8 deforms in a way that makes it appear flattened in cross-section. However, the degree of elastic deformation and thickness of the electrode 2 (electrode segment 21) are determined such that, in the engaged state (mounted state), the cross-sectional area of ​​the tube 8 is at least a predetermined percentage (50% or more, more preferably 70% or more, and even more preferably 80% or more) of that of the natural state. This is to prevent the blood flow in the blood circuit 12 from being inhibited.

[0041] 3 Regarding the voltage application unit The voltage application unit 4 applies a high-frequency voltage between the artery-side electrode 2(1) and the vein-side electrode 2(2), and can be configured using, for example, a function generator. The voltage application unit 4 of the present embodiment is configured to apply a high-frequency voltage with a frequency of 50 kHz and a voltage of 10 Vp-p. Note that the high-frequency voltage is not limited to this, and may be, for example, a high-frequency voltage with a frequency of 5 to 100 kHz and a voltage of 5 to 15 Vp-p.

[0042] 4 Regarding the current measurement unit The current measurement unit 5 converts the current flowing between the artery-side electrode 2(1) and the vein-side electrode 2(2) to which the high-frequency voltage is applied into a voltage, and can be configured using, for example, a differential amplifier circuit that measures the potential difference across a 100 kΩ resistor 51. Note that the resistance value of the resistor 51 is not limited to 100 kΩ.

[0043] 5 Regarding the control arithmetic device (1) Overview The control arithmetic device 6 is configured by a computer having a CPU, an internal memory, an input / output interface, an AD converter, and the like, and based on an inspection program stored in the internal memory, the CPU and peripheral devices cooperate to exert functions as a frequency component extraction unit 61, a needle withdrawal detection unit 62, a reference value setting unit 63, and the like. In addition, the control arithmetic device 6 also performs overall control of the needle withdrawal detection device 100. The functions of this control arithmetic device 6 may be physically configured by a single computer, or may be configured by a plurality of physically separated computers.

[0044] (2) Frequency component extraction unit The frequency component extraction unit 61 extracts a predetermined frequency component from the detection signal obtained by the current measurement unit 5, and can be configured using, for example, a lock-in amplifier or a band-pass filter. The frequency component extraction unit 61 of the present embodiment extracts a component of the same frequency as the high-frequency voltage applied by the voltage application unit 4, and specifically extracts a 50 kHz frequency component from the detection signal.

[0045] (3) Needle dislodgment detection unit The needle dislodgment detection unit 62 detects dislodgment of the arterial puncture needle 7(1) or the venous puncture needle 7(2) based on the extracted signal obtained by the frequency component extraction unit 61. Specifically, the needle dislodgment detection unit 62 detects dislodgment of the arterial puncture needle 7(1) or the venous puncture needle 7(2) by comparing the signal intensity indicated by the extracted signal obtained by the frequency component extraction unit 61 with a predetermined reference value. The reference value in the present embodiment is set by the reference value setting unit 63.

[0046] Here, as a method for detecting dislodgment by the needle dislodgment detection unit 62, for example, (1) a case where the signal intensity falls below the reference value, (2) a case where the signal intensity falls below a predetermined ratio (for example, 80%) of the reference value, or (3) a case where the signal intensity continuously falls below the threshold for a predetermined number of times or for a predetermined time in the above (1) or (2) can be considered.

[0047] (4) Reference value detection unit The reference value setting unit 63 sets the reference value using the extracted signal extracted by the frequency component extraction unit 61 within a predetermined time after the start of dialysis by the hemodialysis apparatus 10. The reference value setting unit 63 of the present embodiment sets the reference value immediately after the start of dialysis. Note that the needle dislodgment detection by the needle dislodgment detection unit 62 is not performed until the reference value is set by the reference value setting unit 63. Then, after the elapse of a predetermined time (after the reference value is set), the needle dislodgment detection unit 62 detects dislodgment of the arterial puncture needle 7(1) or the venous puncture needle 7(2) by comparing the extracted signal obtained by the frequency component extraction unit 61 with the reference value.

[0048] 3. Description of Needle Dislodgment Detection Method Next, a needle dislodgment detection method using the needle dislodgment detection device 100 of the present embodiment will be described with reference to FIG. 5.

[0049] 1. Electrode Attachment First, a patient is punctured with the arterial puncture needle 7(1) and the venous puncture needle 7(2) to complete the preparation for hemodialysis (step S1). In this state, the electrodes 2 are respectively attached to each tube 8 using the attachment device 9 (step S2). At this time, as described above, regardless of the diameter of the tube 8, the divided electrode bodies 21 deform to be recessed, so that the electrodes 2 are brought into close contact along the outer circumferential surface of the tube 8.

[0050] 2. Calibration (Setting of Reference Values) After electrodes 2 are attached to each tube 8, a calibration operation is performed (step S4) simultaneously with the start of dialysis by the hemodialysis machine 10 (step S3). Specifically, a high-frequency voltage is applied to the arterial electrode 2(1) and the venous electrode 2(2) by the voltage application unit 4, and the potential difference between electrodes 2(1) and 2(2) is detected by the current measurement unit 5. In addition, a frequency component extraction unit 61 extracts predetermined frequency components from the detection signal obtained by the current measurement unit 5. Then, a reference value setting unit 63 sets a reference value using the extracted signal extracted by the frequency component extraction unit 61.

[0051] 3. Needle Removal Detection Simultaneously with the completion of the calibration described in (2) above, the needle removal detection unit 62 compares the extracted signal extracted by the frequency component extraction unit 61 with the reference value set by the reference value setting unit 63 to detect the removal of the arterial puncture needle 7(1) or the venous puncture needle 7(2) (step S5). This needle removal detection is performed until hemodialysis by the hemodialysis machine 10 is completed (steps S6, S7). In (2) and (3) above, the voltage application unit 4 continuously applies a high-frequency voltage between electrodes 2(1) and 2(2), and the detection of the potential difference by the current measurement unit 5 and the extraction of frequency components by the frequency component extraction unit 61 are performed continuously.

[0052] Fourth, Effects of this Embodiment According to the needle removal detection device 100 of this embodiment, even if the diameter of the tube 8 changes, the electrode 2 itself undergoes elastic deformation and adheres almost tightly to the outer circumferential surface of the tube 8. Therefore, the same electrode 2 can be attached in close contact to tubes 8 of various different diameters.

[0053] Therefore, unlike in the past, it is no longer necessary to prepare electrodes 2 according to the diameter of the tube 8, which promotes the standardization of parts. In addition, since the electrodes 2 are in close contact with the tube 8, the same needle extraction detection accuracy as in the past can be ensured.

[0054] Furthermore, various types of noise superimposed on the current measurement signal, such as noise caused by vibrations of the blood pump 14c of the hemodialysis machine 10 or noise caused by a person touching the tube, can be effectively removed, thereby improving the accuracy of needle removal detection.

[0055] Furthermore, since the electrode 2 is composed of two electrode segments 21, and these electrode segments 21 move from a disengaged state where they are separated from each other to a mounting state where each electrode segment 21 clamps the tube 8 from all sides, the electrode 2 can be easily attached to the tube 8 even after puncture.

[0056] Since the electrode 2 is elastically deformable, it is difficult to stably attach it to the tube 8 by itself. However, the highly rigid holder 91 allows each electrode segment 21 to be securely attached to the tube 8 by being clamped from all sides.

[0057] Fifth Modified Embodiments Note that the present invention is not limited to the embodiments described above.

[0058] The opposing surface 21c of the electrode segment 21 does not need to be flat. For example, as shown in Figure 6, a groove 21b may be provided on the opposing surface 21c of the electrode segment 21 that contacts the tube 8. The cross-sectional shape of the groove 21b is not limited to this. Also, as shown in Figure 7, the opposing surface 21c of the electrode segment 21 may be protruding or recessed. The opposing surfaces 21c of the electrode segment 21 may have different irregularities. In short, it is sufficient that when the tube 8 is sandwiched, the electrode segment 21 elastically deforms from its natural state, and the surface 21c that contacts the tube 8 becomes recessed.

[0059] Furthermore, the holder 91 may be a flat plate-shaped object bonded to the back surface of the electrode division 21, as shown in Figure 8. As shown in the same figure, each holder 91 may not be hinged together and may be completely separable. In this case, the holders 91 may be sandwiched between separate elastic coupling members such as rubber bands, or engaging and engaged portions as described above may be provided between the opposing sides of each holder 91.

[0060] Furthermore, as shown in Figure 9, the electrode 2 does not have to be divided and may be a single piece. In this case, the holder 91 and the electrode 2 can be used to sandwich the tube 8 from opposite directions.

[0061] Needle removal can be detected simply by a change in the measured current, without performing frequency component extraction as described above.

[0062] Furthermore, it goes without saying that the present invention is not limited to the embodiments described above, and various modifications are possible without departing from its spirit.

[0063] According to the present invention, it is possible to provide a needle extraction detection device having an electrode that can be attached in close contact with the outer circumferential surface of a tube, even if the diameter of the tube changes.

[0064] 100... Needle removal detection device 10... Hemodialysis machine 2... Electrode 21... Electrode segment 7... Puncture needle 8... Tube 9... Attachment device 91... Holder

Claims

1. A needle removal detection device for detecting when an arterial or venous puncture needle of a hemodialysis machine has been withdrawn from a patient, comprising: a pair of electrodes detachably attached to the outer circumferential surfaces of an arterial tube connected to the arterial puncture needle and a venous tube connected to the venous puncture needle, respectively; a voltage application unit for applying a predetermined voltage between the electrodes; a current measurement unit for measuring the current flowing between the electrodes due to the application of the voltage; and a needle removal detection unit for detecting the withdrawal of the arterial or venous puncture needle based on a current measurement signal output by the current measurement unit, wherein the electrodes are made of an elastically deformable conductive material and are attached by being pressed against the outer circumferential surface of the tube so as to undergo elastic deformation.

2. The needle removal detection device according to claim 1, wherein the voltage application unit applies a high-frequency voltage between the electrodes, and the needle removal detection unit detects the removal of the arterial puncture needle or the venous puncture needle based on an extracted signal obtained by extracting a predetermined frequency component from the current measurement signal.

3. The needle extraction detection device according to claim 1, wherein the electrode is composed of a plurality of electrode segments, and in the mounted state attached to the tube, each electrode segment is configured to clamp the tube from the surroundings.

4. The needle removal detection device according to claim 3, wherein the electrode segment is held by a plurality of holders that have higher rigidity than the electrode segment, and the electrode is configured to be in the mounted state by engaging each of the holders with each other.

5. The needle extraction detection device according to claim 3, wherein the electrode is composed of a pair of electrode divisions, and in the mounting state, these electrode divisions clamp the tube from opposing directions.

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