Hemodialysis device

Abstract

To prevent occurrence of excess water removal by restricting leakage of dialysis fluid from a water removal pump as much as possible.SOLUTION: A water removal pump 20 provided in a hemodialyzer 1 includes a piston 24 provided within a cylinder 21 so as to be moved forward and backward and having a notch 24a formed at a tip, a joint mechanism 25 connected to the piston 24, and a motor 26 to drive the piston 24 via the joint mechanism 25. The piston 24 rotates once during one reciprocation of the piston 24, while an inhalation phase in which dialysis fluid flows into a housing chamber 21a from an inhalation port 22 and a discharge phase in which the dialysis fluid in the housing chamber 21a is discharged from a discharge port are executed, thereby sending the dialysis fluid. A control means C controls a revolution speed of the piston 24 during the discharge phase so as to be faster than a revolution speed of the piston 24 during the inhalation phase.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a hemodialysis apparatus, and more particularly to a hemodialysis apparatus provided with a water removal passage and a water removal pump for water removal in a dialysate circuit.

Background Art

[0002] Conventionally, hemodialysis apparatuses for the purpose of hemodialysis treatment and the like are known. A hemodialysis apparatus includes a dialyzer for performing hemodialysis, a dialysate circuit connected to the dialyzer, and a water removal passage and a water removal pump provided in the dialysate circuit for removing water from the dialyzer (Patent Document 1). When performing water removal during hemodialysis treatment, water removal is performed from the dialyzer by operating the water removal pump. Control means for controlling the water removal pump is configured to set the water removal rate or the amount of water removal according to the patient. A so-called piston pump is employed for the water removal pump. The piston pump includes a cylinder having an accommodation chamber formed therein and a suction port and a discharge port formed at opposite positions, a piston provided movably forward and backward inside the cylinder and having a notch formed at its tip, a joint mechanism connected to the piston, and a motor for driving the piston via the joint mechanism. When the piston is rotated once while the piston makes one reciprocation by the motor, during that time, an inhalation phase in which the notch of the piston communicates with the suction port and dialysate flows into the accommodation chamber, and a discharge phase in which the notch communicates with the discharge port and dialysate is discharged from the accommodation chamber are alternately performed, and water removal is performed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Here, when the above-described water removal pump is used for a long time, the piston wears out and dialysis fluid leaks from between the piston and the cylinder, resulting in over-water removal where more dialysis fluid flows through the water removal passage than the set water removal amount, and more water is extracted from the patient than the water removal amount determined by the doctor. There was a problem that this might threaten the patient's life. In view of such problems, the present invention provides a hemodialysis device capable of suppressing leakage of dialysis fluid in a water removal pump and preventing the occurrence of over-water removal as much as possible.

Means for Solving the Problems

[0005] That is, the hemodialysis device according to the present invention is a hemodialysis device including a dialyzer that performs hemodialysis, a dialysis fluid circuit connected to the dialyzer, and a water removal passage and a water removal pump provided in the dialysis fluid circuit for removing water from the dialyzer, The above-described water removal pump includes a cylinder in which an accommodation chamber is formed inside and a suction port and a discharge port are formed at opposite positions, a piston provided movably forward and backward inside the cylinder and having a notch formed at the tip, a joint mechanism connected to the piston, a motor that drives the piston via the joint mechanism, and control means that controls the motor. In the hemodialysis device in which the joint mechanism rotates the piston once during one reciprocation of the piston, and an inhalation phase in which dialysis fluid flows into the accommodation chamber from the suction port and an ejection phase in which the dialysis fluid in the accommodation chamber is discharged from the discharge port are performed, The above-described control means is characterized in that it controls the motor of the water removal pump so that the rotation speed of the piston in the discharge phase is higher than the rotation speed of the piston in the inhalation phase.

Effects of the Invention

[0006] First, as a result of conducting an experiment using a water removal pump with a worn piston, a large amount of leakage of the above-described dialysis fluid was observed in the discharge phase. Therefore, in the present invention, by controlling the rotation speed of the piston in the discharge phase to be higher than the rotation speed of the piston in the suction phase, leakage of the dialysate in the discharge phase can be suppressed as much as possible, and it becomes possible to prevent the risk to the patient due to ultrafiltration. BRIEF DESCRIPTION OF THE DRAWINGS

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

[0008] The present invention will be described below with reference to the illustrated embodiments. FIG. 1 shows the liquid circuit of the hemodialysis apparatus 1, and the hemodialysis apparatus 1 is controlled by control means C. As the control means C, a computer system such as a microcontroller or a microcomputer can be used. The hemodialysis apparatus 1 includes a dialyzer 2 that performs dialysis between blood and dialysate by diffusion and ultrafiltration, a blood circuit 3 connected to the dialyzer 2 for circulating blood, and a dialysate circuit 4 connected to the dialyzer 2 for circulating dialysate. The dialysate circuit 4 includes two identical first metering chambers 11 and second metering chambers 12. The interiors of the first and second metering chambers 11 and 12 are partitioned by diaphragms into a supply chamber 11a, 12a for accommodating fresh dialysate and a recovery chamber 11b, 12b for accommodating used dialysate. A liquid supply passage 13 communicating with a dialysate supply means (not shown) and a dialysate supply passage 14 for supplying fresh dialysate to the dialyzer 2 are connected to the supply chambers 11a, 12a of the two first and second metering chambers 11 and 12. In addition, the recovery chambers 11b and 12b are connected to a dialysate recovery passage 15 for recovering the used dialysate that has passed through the dialyzer 2, and a drainage passage 16 for discharging the used dialysate to a drainage destination such as a drainage tank (not shown).

[0009] A water supply pump (not shown) is provided in the liquid supply passage 13, and the downstream portion of the liquid supply passage 13 branches in two directions and is respectively connected to the supply chambers 11a and 12a of the first and second metering chambers 11 and 12. Liquid supply valves V1 and V2 that are opened and closed under the control of the control means C are provided at each branching portion. The upstream portion of the dialysate supply passage 14 branches in two directions and is respectively connected to the supply chambers 11a and 12a of the first and second metering chambers 11 and 12. Supply valves V3 and V4 that are opened and closed under the control of the control means C are provided at each branching portion. The downstream portion is connected to the dialyzer 2. The upstream portion of the dialysate recovery passage 15 is connected to the dialyzer 2, and the downstream portion branches in two directions and is respectively connected to the recovery chambers 11b and 12b of the first and second metering chambers 11 and 12. Recovery valves V5 and V6 that are opened and closed under the control of the control means C are provided at this branching portion. Furthermore, a dialysate pump 17 and a degassing tank 18 are provided in series at a position upstream of the branching portion in the dialysate recovery passage 15. The upstream portion of the drainage passage 16 branches in two directions and is connected to the recovery chambers 11b and 12b of the first and second metering chambers 11 and 12. Drainage valves V7 and V8 that are opened and closed under the control of the control means C are provided at this branching portion, and the downstream portion is connected to a drainage tank (not shown). In the hemodialysis apparatus 1 of this embodiment, in order to perform a water removal operation for removing excess water in the blood during dialysis treatment, a water removal passage 19 is provided between the dialysate recovery passage 15 and the drainage passage 16, and a water removal pump 20 controlled by the control means C is provided in the water removal passage 19.

[0010] According to the dialysis fluid circuit 4 having the above configuration, during dialysis treatment, the fresh dialysis fluid supplied to the supply chambers 11a and 12a of the first and second metering chambers 11 and 12 is alternately sent to the dialyzer 2 through the dialysis fluid supply passage 14, and the used dialysis fluid that has passed through the dialyzer 2 is alternately recovered into the recovery chambers 11b and 12b through the dialysis fluid recovery passage 15. When ultrafiltration is performed during dialysis treatment, the ultrafiltration pump 20 is operated to discharge the used dialysis fluid from the dialysis fluid recovery passage 15 to the drainage passage 16 through the ultrafiltration passage 19. Since the configuration and operation of the dialysis fluid circuit 4 having such a configuration are already known in the art, further description thereof will be omitted. Also, since the components whose descriptions are omitted in FIG. 1 are also known configurations in the art, the descriptions will be omitted.

[0011] Next, FIG. 2 is an explanatory diagram of the cross-section and operation of the ultrafiltration pump 20. Here, the ultrafiltration pump 20 can be configured by a piston pump known in the art, and for example, the ultrafiltration pump described in Patent Document 1 can be used as it is. The ultrafiltration pump 20 includes a cylinder 21 in which an accommodation chamber 21a is formed inside and a suction port 22 and a discharge port 23 are formed at opposite positions, a piston 24 that is provided inside the cylinder 21 so as to be able to move forward and backward and has a notch 24a formed at its tip, a joint mechanism 25 connected to the piston 24, and a motor 26 that drives the piston 24 through the joint mechanism 25, and the motor 26 is controlled by the control means C. The cylinder 21 and the piston 24 are made of a ceramic excellent in corrosion resistance and wear resistance, and a cap 27 is attached to the opening of the piston 24 through a ring seal (not shown).

[0012] The suction port 22 and the discharge port 23 provided on the side portion of the cylinder 21 are provided at positions facing each other with the center of the cylinder 21 interposed therebetween. The upstream side portion of the water removal passage 19 is connected to the suction port 22, and the downstream side portion of the water removal passage 19 is connected to the discharge port 23. The piston 24 reciprocates in the cylinder 21 while rotating by the motor 26 and the coupling mechanism 25. The notch 24a formed at the tip portion of the piston 24 faces the suction port 22 side or the discharge port 23 side as the piston 24 rotates. The coupling mechanism 25 is composed of a member 25a fixed to the rotation shaft of the motor 26 and a spherical bearing 25b provided on the inner wall of the member 25a. A portion of the piston 24 protruding from the cylinder 21 is connected in a state of penetrating through the spherical member of the spherical bearing 25b. The coupling mechanism 25 is configured to rotate the piston 24 once during one reciprocation of the piston 24. When the piston 24 rotates and the notch 24a faces the suction port 22 side, the dialysate flows into the accommodation chamber 21a from the suction port 22. When the notch 24a faces the discharge port 23 side, the dialysate in the accommodation chamber 21a is discharged from the discharge port 23.

[0013] Hereinafter, the operation of the water removal pump 20 having the above configuration will be described. Here, the lower diagrams of the cross-sectional views of the water removal pump 20 shown in FIGS. 2(a) to (d) are shown as views of the rotational positions of the piston 24 in each state as seen from below the cross-sectional views shown in FIGS. 2(a) to (d). In this embodiment, the piston 24 rotates clockwise in the cylinder 21. FIG. 2(a) shows a state where the piston 24 is located at the forward end, and shows a state immediately after the dialysate in the accommodation chamber 21a has been completely discharged from the discharge port 23. At this time, the notch 24a of the piston 24 is not in communication with either the suction port 22 or the discharge port 23. In the following description, the rotational position of the piston 24 at this time is set to 0° (or 360°).

[0014] Figure 2(b) shows a state where the piston 24 is retracting while rotating, and the notch 24a communicates with the intake port 22. When the piston 24 rotates from the state of Fig. 2(a), a part of the notch 24a of the piston 24 comes into communication with the intake port 22, and the dialysate in the water removal passage 19 starts to flow into the accommodation chamber 21a. As the piston 24 rises with the rotation of the piston 24, the volume of the accommodation chamber 21a increases, and accordingly, dialysate flows into the accommodation chamber 21a. In the following description, the rotational position of the piston 24 at this time is set to 90°.

[0015] Figure 2(c) shows a state where the piston 24 is located at the retracted end, indicating a state where the maximum amount of dialysate is accommodated in the accommodation chamber 21a. When the piston 24 further rotates from the state of Fig. 2(b), the communication state between the notch 24a of the piston 24 and the intake port 22 is gradually eliminated. However, since the piston 24 is still retracting during this period, dialysate continues to flow into the accommodation chamber 21a. When the piston 24 reaches the state of Fig. 2(c) and the piston 24 reaches the retracted end, the communication state between the notch 24a of the piston 24 and the intake port 22 is eliminated, and the inflow of further dialysate stops. On the other hand, in the state of Fig. 2(c), since the notch 24a of the piston 24 does not communicate with the discharge port 23 either, the dialysate is not discharged. In the following description, the rotational position of the piston 24 at this time is set to 180°.

[0016] Figure 2(d) shows a state where the piston 24 now advances while rotating, and the notch 24a communicates with the discharge port 23. When the piston 24 rotates from the state of Fig. 2(c), a part of the notch 24a of the piston 24 comes into communication with the discharge port 23, and the discharge of the dialysate from the accommodation chamber 21a to the water removal passage 19 starts. As the piston 24 rotates and moves forward, the volume of the accommodation chamber 21a decreases. Therefore, the dialysate accommodated in the accommodation chamber 21a is pushed out into the water removal passage 19 and discharged. In the following description, the rotational position of the piston 24 at this time is set to 270°.

[0017] Then, as the piston 24 further rotates from the state shown in Fig. 2(d), the piston 24 makes one full rotation and returns to the state shown in Fig. 2(a). Along with this, the piston 24 reciprocates once in the cylinder 21. When the piston 24 rotates from the state shown in Fig. 2(d), the communication state between the notch 24a of the piston 24 and the discharge port 23 is gradually eliminated. However, since the piston 24 continues to move forward during this period, the dialysate is discharged from the accommodation chamber 21a. When the piston 24 reaches the state shown in Fig. 2(a) and reaches the forward end, the communication state between the notch 24a of the piston 24 and the discharge port 23 is eliminated, and the discharge of the dialysate stops.

[0018] Thus, in the water removal pump 20 of this embodiment, the piston 24 is rotated once while the piston 24 reciprocates once by the joint mechanism 25. During this period, the dialysate flows into the accommodation chamber 21a from the suction port 22, and the dialysate in the accommodation chamber 21a is discharged from the discharge port 23. More specifically, from immediately after Fig. 2(a) to immediately before Fig. 2(c) passing through Fig. 2(b), that is, while the piston 24 rotates in the range of 0° to 180°, the piston 24 moves from the forward end toward the rear end, and the notch 24a communicates with the suction port 22 so that the dialysate flows into the accommodation chamber 21a. On the contrary, from immediately after Fig. 2(c) to immediately before Fig. 2(a) passing through Fig. 2(d), that is, while the piston 24 rotates in the range of 180° to 360°, the piston 24 moves from the rear end toward the forward end, and the notch 24a communicates with the discharge port 23 so that the dialysate is discharged from the accommodation chamber 21a. When performing hemodialysis treatment, the doctor sets the amount of water to be removed according to the patient's physical condition or the like, and the control means C sets the water removal rate by the water removal pump 20 according to the set amount of water to be removed. Then, the control means C controls the motor 26 of the water removal pump 20 according to the set water removal rate to drive the piston 24. When the water removal rate is high, the time required for one rotation of the piston 24 is short, and when the water removal rate is low, the time required for one rotation of the piston 24 is long.

[0019] As described above, the cylinder 21 and the piston 24 constituting the water removal pump 20 of this embodiment are made of ceramic, but it is inevitable that they will deteriorate due to long-term use, and as shown in FIG. 3, the tip of the piston 24 will wear into a tapered shape. Even when the tip of the piston 24 wears into a tapered shape in this way, when the piston 24 is located on the forward end side, as shown in FIG. 3(a), no gap is formed between the cylinder 21 and the piston 24, so dialysis fluid leakage is unlikely to occur. On the other hand, when the piston 24 is located on the rearward end side, as shown in FIG. 3(b), a gap is formed between the cylinder 21 and the tip of the piston 24, so the dialysis fluid flowing in from the suction port 22 will pass through this gap and leak out from the discharge port 23. When such dialysis fluid leakage occurs in the water removal pump 20, more dialysis fluid than the set amount of water to be removed will be discharged into the drainage passage 16 through the water removal passage 19 by the amount of this dialysis fluid leakage. That is, over-water removal will occur where more water removal is performed than the amount of water to be removed set by the doctor. This over-water removal will extract more water from the patient than the set amount, which may threaten the patient's life. In view of such problems, in the hemodialysis apparatus 1 of this embodiment, even when the piston 24 is worn, the water removal pump 20 is controlled to suppress dialysis fluid leakage as much as possible, so as to maintain an accurate amount of water to be removed. Here, when the inventor actually measured the amount of leakage of the dialysis fluid using the worn water removal pump 20 of the piston 24, the leakage of the dialysis fluid was confirmed from the time when the rotation angle of the piston 24 was 180°, and the most leakage of the dialysis fluid was confirmed when the rotation angle was 230°.

[0020] FIG. 4 shows a graph of the operation of the water removal pump 20 with respect to the elapsed time and the discharge amount (mL / deg.). The horizontal axis represents the elapsed time, and the vertical axis represents the discharge amount of the water removal pump 20 (the discharge amount per rotation angle (degree) (mL)). In FIG. 4, the solid line indicates the operation of the piston 24 according to this embodiment, and the broken line indicates the operation when the piston 24 is rotated at a constant speed. Here, the origin of the vertical axis indicates that the piston 24 is in the suction phase or the discharge phase based on the rotation angle of the piston 24 or the position in the cylinder 21. Also, as shown in FIG. 4, the time required for one rotation of the piston 24 in this embodiment is adjusted to the time required for one rotation of the piston in the prior art. Therefore, the amount of water removed by one rotation of the piston in the water removal pump 20 of this embodiment and the water removal pump of the prior art is the same.

[0021] First, explaining the prior art shown by the broken line, the suction phase indicates a state where the notch 24a communicates with the suction port 22 formed in the cylinder 21 by the rotation of the piston 24. Here, the suction phase in the prior art indicates a state where the piston 24 rotates in the range of the rotation angle of 0° to 180°. On the other hand, the discharge phase indicates a state where the notch 24a communicates with the discharge port 23 formed in the cylinder 21 by the rotation of the piston 24, indicating a state where the piston 24 rotates in the range of the rotation angle of 180° to 360°. And in the prior art, since the piston 24 is rotated at a constant speed, when it is rotated once during one reciprocation of the piston 24, the suction phase and the discharge phase require the same time.

[0022] In contrast, in the water removal pump 20 of this embodiment, as described above, since dialysis fluid leakage was observed when the rotational position of the piston 24 reached 180°, the discharge phase is set such that the piston 24 rotates in the range of a rotational angle of 180° to 360°, and the suction phase is set such that the piston 24 rotates in the range of a rotational angle of 0° to 180°. And in this embodiment, the control means C controls the motor 26 of the water removal pump 20 so as to control the rotational speed of the piston 24 in the discharge phase to be higher than the rotational speed of the piston 24 in the suction phase. Specifically, from the state shown in FIG. 2(a) until the rotational angle of the piston 24 immediately before FIG. 2(c) reaches 180°, the control means C decelerates the rotational speed of the motor 26. Subsequently, from the state where the rotational angle of the piston 24 is 180° through FIG. 2(d) to the state shown in FIG. 2(a), the control means C accelerates the rotational speed of the motor 26. Here, since the time required for the piston 24 to make one rotation is set to be the same as that of the water removal pump of the prior art, the time required for the discharge phase during one rotation of the piston 24 is shorter than the time required for the suction phase. In the present technology, the rotational angle of the discharge phase is set to 180° to 360°, and the rotational speed of the piston 24 in the discharge phase is controlled to be higher than the rotational speed of the piston 24 in the suction phase (rotational angle: 0° to 180°). However, the discharge phase may be set in a range, for example, from around 160° to 360° at the end of the suction phase, so that a sufficiently high rotational speed is reached at the time when the rotational angle of the piston 24 at which dialysis fluid leakage starts reaches 180°.

[0023] By shortening the time required for the discharge phase as in the water removal pump 20 of this embodiment, the time during which the piston 24 is located on the retreat end side can be shortened, and the amount of dialysis fluid leakage observed in the discharge phase can be reduced as much as possible. Therefore, even when there is wear on the piston 24, it is possible to prevent over-dehumidification where the amount of dehumidified water increases during the dehumidification operation, and it is possible to suppress the impact on the patient. In addition, by making the time required for the discharge phase shorter than the time required for the inhalation phase, the suction operation of the dialysate by the dehumidification pump 20 during the inhalation phase becomes slower. As a result, the suction of the dialysate in the dialyzer 2 becomes gentle, and it is also possible to obtain the effect of reducing clotting (coagulation) of the patient's blood due to a rapid pressure change and clogging of the hollow fiber membrane of the dialyzer 2.

[0024] As described above, the amount of dehumidified water during dialysis treatment is determined by the doctor according to the patient. However, when the amount of dehumidified water is small, the dehumidification speed becomes low. Therefore, when comparing per one rotation of the piston 24, the time that the piston 24 is located on the retracted end side becomes relatively long, and accordingly, the leakage of the dialysate in the discharge phase becomes large. Therefore, the control means C is configured to vary the ratio of the time required for the discharge phase to the time required for the inhalation phase according to the set amount of dehumidified water. That is, when the dehumidification speed is set low, in order to minimize the time that the piston 24 is located on the retracted end side, the rotation speed of the piston 24 in the discharge phase is set high so that the time required for the discharge phase is minimized. For example, when the dehumidification speed is set to 0.1 L / h, the rotation speed of the piston 24 in the discharge phase is rotated at a speed approximately 4100% higher than when the piston 24 is rotated at a constant speed, while the rotation speed of the piston 24 in the inhalation phase is rotated at a speed approximately 50% higher than when rotated at a constant speed. On the other hand, when the dehumidification speed is set to 0.9 L / h, the rotation speed of the piston 24 in the discharge phase is rotated at a speed approximately 500% higher than when rotated at a constant speed, while the rotation speed of the piston 24 in the inhalation phase is rotated at a speed approximately 50% higher than when rotated at a constant speed. Note that the rotational speed of the piston 24 in the drainage phase and the inhalation phase described above is just an example, and it can be appropriately changed according to the leakage state of the piston 24 and the set water removal rate.

[0025] In addition, in the hemodialysis device 1 in the above embodiment, when there is no wear on the piston 24, such as when a new water removal pump 20 is provided, the leakage as described above does not occur, so the rotation of the piston 24 may be constant. In this case, the control means C can integrate the operation time of the water removal pump 20 and start control to vary the rotational speed of the piston 24 as described above in accordance with the timing when the piston 24 wears. Alternatively, it may be directly measured whether leakage occurs, and when leakage occurs, control to vary the rotational speed of the piston 24 as described above may be started.

[0026] Also, when performing hemodialysis treatment using the hemodialysis device 1, in addition to the above water removal rate, the liquid delivery amount of the dialysate by the dialysate pump 17 provided in the dialysate recovery passage 15 is also set. However, the higher this liquid delivery amount is, the higher the pressure acting on the suction port 22 of the water removal pump 20 becomes, so the leakage at the piston 24 as described above is likely to occur. Therefore, the control means C may perform control to vary the rotational speed of the piston 24 as described above when the liquid delivery amount of the dialysate by the dialysate pump 17 is large. In this case, a pressure sensor may be provided in the dialysate recovery passage 15 to measure the pressure of the dialysate, and when the pressure of the dialysate becomes equal to or higher than a predetermined value, control to vary the rotational speed of the piston 24 as described above may be performed.

Explanation of Reference Numerals

[0027] 1 Hemodialysis device 2 Dialyzer 4 Dialysate circuit 19 Water removal passage 20 Water removal pump 21 Cylinder 22 Suction port 23 Discharge port 24 pistons 24a notch 25 coupling mechanism 26 motor C control means

Claims

1. A hemodialysis device that performs hemodialysis, a dialysate circuit connected to the hemodialysis device, and a hemodialysis device provided in the dialysate circuit and having a water removal passage and a water removal pump for removing water from the hemodialysis device, The water removal pump includes a cylinder having an accommodation chamber formed therein and an intake port and a discharge port formed at opposite positions, a piston provided movably forward and backward inside the cylinder and having a notch formed at the tip, a joint mechanism connected to the piston, a motor for driving the piston via the joint mechanism, and control means for controlling the motor, In the hemodialysis device, the joint mechanism rotates the piston once during one reciprocation of the piston, and an intake phase in which dialysate flows into the accommodation chamber from the intake port and a discharge phase in which the dialysate in the accommodation chamber is discharged from the discharge port are performed, The control means controls the motor of the water removal pump so that the rotation speed of the piston in the discharge phase is higher than the rotation speed of the piston in the intake phase. A hemodialysis device characterized by this.

2. The control means controls the motor of the water removal pump so that when the same water removal rate is set, the time required for the piston of the water removal pump to make one rotation and the time required when the rotation speed of the piston is set to be constant are the same. The hemodialysis device according to claim 1, characterized in that it is set as follows.

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