dialysis device

Abstract

To prepare fresh dialysate without any concentration bias by sufficiently stirring stock solution for dialysis and dialysis water.SOLUTION: A dialysis apparatus includes a first dialysate container 11 including a feed chamber 11a, a recovery chamber 11b and a variable volume chamber 11c. In a supplying recovery step, the dialysis apparatus executes water removal operation (Fig.3(a)) of withdrawing liquid from the variable volume chamber with a positive displacement pump 13A and reducing the volume of the variable volume chamber, while recovering used dialysate to the recovery chamber; and in a supplying discharge step (Fig.3(b)-(e)), executes stock solution supply operation (Fig. 3(c) and (d)) of withdrawing the liquid from the variable volume chamber with the positive displacement pump, reducing the volume of the variable volume chamber and supplying stock solution for dialysis from stock solution supply means. The positive displacement pump is configured to return the liquid withdrawn in the water removal operation and the liquid withdrawn in the stock solution supply operation to the variable volume chamber after the stock solution supply operation (fig.3(e)) in the supplying discharge step.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a dialysis apparatus, and more particularly to a dialysis apparatus provided with a dialysate container having a supply chamber, a recovery chamber, and a variable volume chamber formed therein, wherein fresh dialysate is prepared by mixing dialysis water and a dialysate stock solution in the supply chamber.

Background Art

[0002] Conventionally, as a dialysis apparatus for use in hemodialysis treatment, a dialysis apparatus provided with a dialysate container in a dialysate circuit through which dialysate flows is known, and the inside of the dialysate container is partitioned into a supply chamber for preparing fresh dialysate, a recovery chamber for recovering used dialysate, and a variable volume chamber formed between the supply chamber and the recovery chamber (Patent Document 1). In such a dialysis apparatus, two dialysate containers are provided. While a liquid supply and recovery step is performed in one dialysate container to supply fresh dialysate from the supply chamber to the dialyzer and recover used dialysate in the recovery chamber, in the other dialysate container, a water supply and drainage step is performed to supply dialysis water to the supply chamber and drain used dialysate from the recovery chamber. During this water supply and drainage step, fresh dialysate is prepared by mixing dialysis water and a dialysate stock solution in the supply chamber. By alternately performing the above steps in each dialysate container, fresh dialysate can be continuously supplied to the dialyzer and used dialysate can be recovered. In the dialysis apparatus of Patent Document 1, the dialysate container is partitioned into a supply chamber, a recovery chamber, and a variable volume chamber by two flexible membranes such as diaphragms. A liquid such as silicone oil is accommodated in the variable volume chamber, and a positive displacement pump is connected. By taking in and out the liquid in the variable volume chamber by the positive displacement pump, the volume of the variable volume chamber can be increased or decreased, and the accommodation volumes of the adjacent supply chamber and recovery chamber can be varied through the flexible membrane. As a result, in the fluid supply and recovery process described above, a predetermined amount of liquid is extracted from the variable volume chamber using the positive displacement pump, and a water removal operation is performed to reduce the volume of the variable volume chamber while the used dialysate is collected in the recovery chamber, thereby removing excess fluid from the patient via the dialyzer. Furthermore, in the water supply and drainage process described above, a predetermined amount of liquid is extracted from the variable volume chamber using the positive displacement pump, reducing the volume of the variable volume chamber and performing a stock solution supply operation in which the stock solution supply means is supplied with dialysis stock solution to the dialysis water passage. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-18540 [Overview of the project] [Problems that the invention aims to solve]

[0004] In the above-mentioned Patent Document 1, during the water removal operation of the liquid supply and recovery process, the liquid extracted from the variable volume chamber is returned to the variable volume chamber in its entirety in preparation for the raw solution supply operation of the next water supply and drainage process, thereby restoring the variable volume chamber to its original volume. This restoration operation is performed before the raw solution supply operation of the water supply and drainage process, and during this time, dialysis water is supplied to the supply chamber. Here, since dialysis conditions such as dialysis time and amount of fluid removed are set for each treatment, the amount of fluid extracted from the variable volume chamber during the fluid removal operation differs from treatment to treatment, and the time required to return the variable volume chamber to its original volume in preparation for the stock solution supply operation of the water supply and drainage process described above is not constant. However, conventionally, assuming that the entire volume of liquid would be removed from the variable volume chamber during the water removal operation, the time required to return the entire volume of liquid that could be contained in the variable volume chamber from the positive displacement pump to the variable volume chamber was set as the above-mentioned recovery time. As mentioned above, when the variable volume chamber is returned to its original volume, dialysis water is supplied to the supply chamber. If dialysis water is supplied to the supply chamber for the same amount of time required to return the entire volume of liquid that can be contained in the variable volume chamber to the variable volume chamber, then during the return time, the supply chamber will be supplied with dialysis water up to about half its volume. On the other hand, when preparing fresh dialysate in the above water supply and drainage process, the dialysate stock solution is diluted with dialysate water to about 15 times its original volume. In this process, supplying the dialysate stock solution to the supply chamber first, and then supplying as much dialysate water as possible afterward, improves the mixing performance because it allows for a continuous flow of dialysate water. However, using the procedure described in Patent Document 1, a large amount of dialysis water is supplied to the supply chamber before the stock solution supply operation in the water supply and drainage process. As a result, there is less dialysis water available for supply after the stock solution supply operation, and sufficient stirring performance cannot be obtained. Therefore, conventional dialysis machines required a stirring means to mix the dialysis water and the dialysis stock solution in the supply passage connecting the supply chamber and the dialyzer. In view of these problems, the present invention provides a dialysis apparatus equipped with a dialysis fluid container having a supply chamber, a recovery chamber, and a variable volume chamber formed inside, which prepares fresh dialysis fluid in the supply chamber, and which is capable of preparing fresh dialysis fluid by thoroughly stirring it with the supply of dialysis water. [Means for solving the problem]

[0005] In other words, the invention of claim 1 comprises a dialysate container having a supply chamber, a recovery chamber, and a variable volume chamber formed inside; a dialysate water passage connected to the supply chamber for supplying dialysate water; a concentrate supply means connected to the dialysate water passage for supplying concentrate for dialysate; a supply passage connected to the supply chamber for supplying fresh dialysate to a dialyzer; a recovery passage connected to the recovery chamber for recovering used dialysate from the dialyzer; a drainage passage connected to the recovery chamber for draining used dialysate; and a positive displacement pump for supplying and draining liquid into the variable volume chamber. The above-mentioned dialysis fluid container alternately performs a fluid supply and recovery process in which fresh dialysis fluid is supplied from the supply chamber to the dialyzer and used dialysis fluid is collected in the recovery chamber, and a water supply and drainage process in which dialysis water is supplied to the supply chamber and used dialysis fluid is drained from the recovery chamber. In the above liquid supply and recovery process, the above positive displacement pump is used Origin volume In a dialysis apparatus, a predetermined amount of liquid is drawn out from a variable volume chamber, and a water removal operation is performed to reduce the volume of the variable volume chamber while collecting used dialysis fluid in the recovery chamber. In the water supply and drainage process, a predetermined amount of liquid is drawn out from the variable volume chamber by the positive displacement pump, reducing the volume of the variable volume chamber, and a stock solution supply operation is performed to supply stock solution for dialysis from the stock solution supply means to the dialysis water passage. In the supply chamber, dialysis water and stock solution for dialysis are mixed to prepare fresh dialysis fluid. The above positive displacement pump is, If the amount of liquid in the variable volume chamber is not insufficient when performing the above stock solution supply operation, then, after the stock solution supply operation in the water supply and drainage process, while supplying dialysis water to the supply chamber, The liquid extracted in the above water removal operation and the liquid extracted in the above stock solution supply operation are used together. Return to the variable volume chamber and restore the variable volume chamber to its original volume. In order to When performing the above-mentioned undiluted liquid supply operation By performing the above water removal operation If the amount of liquid in the variable volume chamber is insufficient, before the stock liquid supply operation in the water supply and drainage process described above... While supplying dialysis water to the supply room Then, the insufficient liquid is returned from the above-mentioned positive displacement pump to the variable volume chamber. This enables the stock solution supply operation, and while dialysis water is supplied to the supply chamber after the stock solution supply operation, the liquid extracted in the water removal operation and the liquid extracted in the stock solution supply operation are returned to the variable volume chamber to restore the variable volume chamber to its original volume. It is characterized by the following: [Effects of the Invention]

[0006] According to the invention of claim 1, the liquid extracted in the water removal operation and the liquid extracted in the stock solution supply operation are returned to the variable volume chamber after the stock solution supply operation in the water supply and drainage process. If the amount of liquid in the variable volume chamber is insufficient when performing the above-mentioned stock solution supply operation, the insufficient amount of liquid shall be returned to the variable volume chamber from the positive displacement pump before the stock solution supply operation in the above-mentioned water supply and drainage process. It is. As a result, the entire amount of liquid that can be contained in the variable volume chamber is not returned to the variable volume chamber before the stock solution supply operation in the water supply and drainage process, as in the conventional method. Therefore, it is possible to extend the time for supplying dialysis water to the supply chamber after the stock solution supply operation in the water supply and drainage process, allowing the dialysis water and the dialysis stock solution to be thoroughly mixed. This makes it possible to prepare fresh dialysis fluid without concentration imbalances. [Brief explanation of the drawing]

[0007] [Figure 1] A diagram of the fluid circuit of the dialysis apparatus according to this embodiment. [Figure 2] Diagram of a positive displacement pump configuration. [Figure 3] A diagram illustrating the operation when the water removal rate is normal. [Figure 4] A diagram illustrating the operation when the water removal rate is at its maximum. [Figure 5] A graph showing the retraction distance and time duration of the piston in a positive displacement pump. [Modes for carrying out the invention]

[0008] The following illustrated embodiment will be described. Figure 1 shows a fluid circuit 1 that constitutes a dialysis machine used for hemodialysis treatment, and comprises a dialyzer 2 for performing hemodialysis, a dialysate circuit 3 for circulating dialysate to the dialyzer 2, and a blood circuit 4 for circulating blood to the dialyzer 2. The dialysate circuit 3 described above is equipped with two dialysate containers, a first dialysate container 11 and a second dialysate container 12. Inside each container, a flexible membrane consisting of two diaphragms divides the container into supply chambers 11a and 12a for preparing fresh dialysate, recovery chambers 11b and 12b for collecting used dialysate, and variable volume chambers 11c and 12c formed between the supply chambers 11a and 12a and the recovery chambers 11b and 12b. Each of the variable volume chambers 11c and 12c contains a liquid such as silicone oil, and the volume of each variable volume chamber can be changed by moving the liquid in and out using the positive displacement pumps 13A and 13B connected to each chamber. This makes it possible to reduce the volume of the variable volume chambers 11c and 12c by removing the liquid from them, thereby expanding the supply chambers 11a and 12a or the recovery chambers 11b and 12b.

[0009] The above dialysis fluid circuit 3 includes a dialysis water passage 5 for supplying the above dialysis water to the supply chambers 11a and 12a of the above first and second dialysis fluid containers 11 and 12, an A stock solution passage 6 connected to the dialysis water passage 5 for supplying the A stock solution to the supply chambers 11a and 12a through the dialysis water passage 5, a B stock solution passage 7 also connected to the dialysis water passage 5 for supplying the B stock solution to the supply chambers 11a and 12a through the dialysis water passage 5, a liquid supply passage 8 for supplying the fresh dialysis fluid prepared in the supply chambers 11a and 12a to the dialyzer 2, a recovery passage 9 for recovering the used dialysis fluid that has passed through the dialyzer 2 into the above recovery chambers 11b and 12b, and a drainage passage 10 for draining the used dialysis fluid from the above recovery chambers 11b and 12b. The above blood circuit 4 consists of an arterial circuit 4A for sending blood from the patient to the dialyzer 2 and a venous circuit 4B for returning blood from the dialyzer 2 to the patient, and a blood pump BP is provided in the arterial circuit 4A. Note that, as the dialysis water for preparing the above fresh dialysis fluid, purified water such as RO water is used. As the dialysis stock solutions, there are an A stock solution mainly composed of sodium chloride and containing calcium chloride, and a B stock solution composed of an aqueous sodium hydrogen carbonate solution. By mixing these A stock solution, B stock solution, and dialysis water at a predetermined ratio, for example, 1:1.26:32.74, the dialysis stock solution is diluted to a predetermined concentration to prepare fresh dialysis fluid.

[0010] A liquid supply pump 22 for sending the above dialysis water is provided in the dialysis water passage 5, and the downstream part of the dialysis water passage 5 branches in two directions and is connected to the supply chambers 11a and 12a of the above first and second dialysis fluid containers 11 and 12. Also, the above A stock solution passage 6 and B stock solution passage 7 are connected to the dialysis water passage 5 in the section between the liquid supply pump 22 and the above first and second dialysis fluid containers 11 and 12. The A stock solution passage 6 is connected to an A stock solution container 23 as the stock solution supply means for accommodating the A stock solution, and the B stock solution passage 7 is connected to a B stock solution container 24 as the stock solution supply means for accommodating the B stock solution. Note that, as the stock solution supply means for the A stock solution and B stock solution, the liquid supply equipment and supply devices provided in the treatment facility where the dialysis device is installed can also be used. Between the liquid supply pump 22 and the connection point of the stock solution A passage 6 in the dialysate water passage 5, a first on-off valve V1 is provided. In the passages branched to the supply chambers 11a and 12a of the first and second dialysate containers 11 and 12, liquid supply valves V2 and V3 are provided respectively. In the stock solution A passage 6, a stock solution A supply valve V4 is provided, and in the stock solution B passage 7, a stock solution B supply valve V5 is provided.

[0011] The upstream part of the liquid supply passage 8 branches in two directions and is connected to the supply chambers 11a and 12a of the first and second dialysate containers 11 and 12 respectively. The downstream end is connected to the dialyzer 2. Supply valves V6 and V7 are provided at the branching parts respectively. The recovery passage 9 has its upstream end connected to the dialyzer 2, and its downstream part branches in two directions and is connected to the recovery chambers 11b and 12b of the first and second dialysate containers 11 and 12 respectively. A liquid feed pump 27 for feeding the used dialysate is provided, and recovery valves V10 and V11 are provided at the branching parts. A closed circuit is formed by these supply chambers 11a and 12a, the liquid supply passage 8, the dialyzer 2, the recovery passage 9, the recovery chambers 11b and 12b. When the liquid feed pump 27 is operated, the dialysate flows from the supply chambers 11a and 12a to the recovery chambers 11b and 12b via the dialyzer 2. The upstream part of the drain passage 10 branches in two directions and is connected to the recovery chambers 11b and 12b of the first and second dialysate containers 11 and 12 respectively. The downstream end is connected to a drain pipe laid in the treatment facility. Drain valves V12 and V13 are provided at the branching parts. When the stock solution A, stock solution B, and dialysate water flow into the supply chambers 11a and 12a from the dialysate water passage 5, the used dialysate is drained from the recovery chambers 11b and 12b to the drain passage 10. In this configuration, fresh dialysate is prepared by mixing concentrate A, concentrate B, and dialysate water in predetermined ratios in the supply chambers 11a and 12a. The entire amount of the prepared fresh dialysate is supplied from the supply chambers 11a and 12a to the dialyzer 2, and the used dialysate that has flowed through the dialyzer 2 is collected in the collection chambers 11b and 12b. The supply and collection process is defined as the period until the collection chambers 11b and 12b are filled and the flow of liquid stops. The supply chambers 11a and 12a are filled with dialysate prepared by supplying dialysate water to the supply chambers 11a and 12a, and the period until the entire amount of used dialysate is drained from the collection chambers 11b and 12b and the flow of liquid stops is defined as the water supply and drainage process. These processes are performed alternately in the first and second dialysate containers 11 and 12. Furthermore, all the valves and pumps arranged in the liquid circuit 1 described above are controlled by a control means C that executes processing according to a program such as a computer.

[0012] Figure 2 shows a positive displacement pump 13A that injects and discharges liquid into and out of the variable volume chamber 11c of the first dialysate container 11, and a positive displacement pump 13B connected to the variable volume chamber 12c of the second dialysate container 12 has the same configuration. The positive displacement pump 13A comprises a piston 32 that is movable back and forth inside a cylindrical housing 31, and a motor 33 that moves the piston 32 back and forth, and its operation is controlled by the control means C. A cylinder chamber 31a for containing liquid is formed in the upper part of the housing 31 as shown in the figure. The tip of the cylinder chamber 31a is tapered and is connected to the variable volume chamber 11c of the first dialysis fluid container 11 via piping (not shown).

[0013] The piston 32 consists of a main body 32a with a through hole formed in the center through which a ball screw 33a connected to the drive shaft of the motor 33 can pass, a cap 32b that closes the tip of the main body 32a, and a ball nut 32c provided at the rear end of the main body 32a that engages with the ball screw 33a. Furthermore, a guide rod 34 is fixed to the side of the ball nut 32c, facing outward, and is inserted into an elongated guide hole 31b formed in the housing 31. This prevents the ball nut 32c from rotating in conjunction with the rotation of the ball screw 33a, and guides the vertical movement of the ball nut 32c and the piston 32. In addition, the housing 31 is provided with an origin sensor 35 that detects the approach of the guide rod 34. Furthermore, a disc-shaped disk 33b is provided on the drive shaft of the motor 33, and the rotational position of the disk 33b is detected by a rotation sensor 36. The control means C detects that the piston 32 has reached the origin position based on the detection of the guide rod 34 by the origin sensor 35. In addition, the rotation angle of the drive shaft of the motor 33 is detected by the rotation position of the disk 33b detected by the rotation sensor 36.

[0014] According to the positive displacement pump 13A having the above configuration, the motor 33 is rotated forward or backward to move the piston 32 forward or backward, thereby discharging or sucking the liquid contained in the cylinder chamber 31a, and the control means C recognizes the position of the piston 32 from the rotation angle of the drive shaft of the motor 33 in the forward and reverse directions. In this embodiment, when the motor 33 is reversed, the piston 32 retracts, liquid is drawn out of the variable volume chamber 11c, and the volume of the variable volume chamber 11c decreases. When the motor 33 is rotated forward, the piston 32 moves forward, liquid is injected into the variable volume chamber 11c, and the liquid that was drawn out into the cylinder chamber 31a is returned to the variable volume chamber 11c, increasing the volume of the variable volume chamber 11c. When the piston 32 reaches the origin position, the variable volume chamber 11c returns to its original volume. With the positive displacement pumps 13A and 13B configured in this way, a predetermined amount of liquid is extracted from the variable volume chambers 11c and 12c. In the liquid supply and recovery process, the volume of the variable volume chambers 11c and 12c is reduced while the used dialysate is recovered into the recovery chambers 11b and 12b, thereby performing a water removal operation. Furthermore, in the water supply and drainage process described above, by reducing the volume of the variable volume chambers 11c and 12c, a concentrate supply operation is performed in which concentrate A is supplied from the concentrate A container 23 connected to the dialysis water passage 5, and concentrate B is supplied from the concentrate B container 24. At the same time, dialysis water is supplied from the dialysis water passage 5 to the supply chambers 11a and 12a, so that concentrate A, concentrate B, and dialysis water are mixed in the supply chambers 11a and 12a to prepare fresh dialysis fluid.

[0015] In a dialysis apparatus configured in this way, dialysis conditions such as treatment time, total amount of fluid removed, and dialysate flow rate to the dialyzer 2 are set in the control means C in advance for each treatment, and the control means C controls the operation of various valves and pumps arranged in the fluid circuit 1 according to the set dialysis conditions. Since the supply of fresh dialysate to the dialyzer 2 is performed by alternately connecting the supply chambers 11a and 12a of the two dialysate containers 11 and 12 to the dialyzer 2, the time required for the liquid supply and recovery process and the liquid supply and drainage process are set to the same time, and the duration of these processes becomes shorter as the dialysate flow rate (flow rate per unit time) to the dialyzer 2 increases. Furthermore, in the above-mentioned fluid supply and recovery process, the operation of the positive displacement pumps 13A and 13B, which are used to extract liquid from the variable volume chambers 11c and 12c as a water removal operation, is controlled according to the water removal rate determined from the treatment time and the total amount of water removed. Furthermore, the faster the ultrafiltration rate, the greater the amount of liquid extracted from the variable volume chambers 11c and 12c in a single fluid supply and recovery process, and the greater the retraction distance of the piston 32 in the positive displacement pumps 13A and 13B. Also, even if the ultrafiltration rate is the same, a lower dialysate flow rate results in a longer duration of the fluid supply and recovery process, and since a larger amount of liquid is extracted from the variable volume chambers 11c and 12c, the retraction distance of the piston 32 also increases. In contrast, the mixing ratio of concentrate A, concentrate B, and dialysis water in the water supply and drainage process is set such that concentrate A, concentrate B, and dialysis water are in a predetermined ratio within the supply chambers 11a and 12a, with the variable volume chambers 11c and 12c being the origin volume, the supply chambers 11a and 12a being the maximum volume, and the recovery chambers 11b and 12b being the minimum volume. In other words, after the required amounts of stock solution A and stock solution B are supplied to the supply chambers 11a and 12a respectively, dialyzing water is supplied to the supply chambers 11a and 12a until they reach their maximum volume, while the variable volume chambers 11c and 12c are returned to their original volume, thereby preparing fresh dialysate of a predetermined concentration. In this case, the operation of the positive displacement pumps 13A and 13B is controlled to extract amounts of liquid corresponding to the pre-set A stock solution and B stock solution from the variable volume chambers 11c and 12c, and then, while supplying dialysis water to the supply chambers 11a and 12a, the variable volume chambers 11c and 12c are controlled to return to their original volume.

[0016] The operation of the dialysis machine having the above configuration when set to a normal fluid removal rate will be explained below using Figures 1, 3, and 5. Figures 3 and 5 illustrate the first dialysate container 11 in Figure 1. While the first dialysate container 11 performs the fluid supply and recovery process, the second dialysate container 12 performs the water supply and drainage process. Subsequently, while the first dialysate container 11 performs the water supply and drainage process, the second dialysate container 12 performs the fluid supply and recovery process. In other words, each process is performed alternately in the first dialysate container 11 and the second dialysate container 12, and the explanation in Figure 3 is also common to the second dialysate container 12. Figure 3(a) shows the state in which, during the fluid supply and recovery process, fresh dialysate is supplied from the supply chamber 11a to the dialyzer 2, used dialysate is recovered from the dialyzer 2 into the recovery chamber 11b of the first dialysate container 11, and a predetermined amount of liquid is extracted from the variable volume chamber 11c by the positive displacement pump 13A, thereby reducing the volume of the variable volume chamber 11c and expanding the recovery chamber 11b. In this fluid supply and recovery process, the fluid supply valve V2 of the dialysis water passage 5 connected to the supply chamber 11a of the first dialysis fluid container 11 and the drain valve V12 of the drain passage 10 connected to the recovery chamber 11b are closed, and the supply valve V6 of the fluid supply passage 8 and the recovery valve V10 of the recovery passage 9 are opened. In this state, the first dialysate container 11 is connected to the dialyzer 2 to form a sealed circuit. Used dialysate is sent from the dialyzer 2 to the recovery chamber 11b by the fluid pump 27 installed in the recovery passage 9. As the volume of the recovery chamber 11b increases due to the inflow of used dialysate, the volume of the supply chamber 11a decreases accordingly, and fresh dialysate is pushed out of the supply chamber 11a into the fluid supply passage 8 and supplied to the dialyzer 2.

[0017] Figure 5 is a graph showing the operation of the piston 32 of the positive displacement pump 13A in a time series during the liquid supply and recovery process and the water supply and drainage process, with the vertical axis of the graph representing the amount of piston 32 retraction. The origin of the vertical axis indicates that the piston 32 is at its forward end, and the variable volume chamber 11c has the volume at the origin. The maximum value of the vertical axis indicates the retracted end of the piston 32, and when the piston 32 reaches its retracted end, the variable volume chamber 11c has the minimum volume. The horizontal axis represents the time interval, with period (a) representing the fluid supply and recovery process, and periods (b) to (e) representing the water supply and drainage process. Below the horizontal axis, the timing of supplying dialysis water to the supply chamber 11a during the water supply and drainage process is shown. Figure 5(A) shows the operation of the piston 32 when the water removal speed is set to the normal water removal speed corresponding to Figure 3, during the water removal operation performed simultaneously with the liquid supply and recovery process described above. Throughout the entire liquid supply and recovery process in period (a), the piston 32 is gradually retracted at a constant speed until it is retracted to about 1 / 5 of its total retraction distance. As a result, liquid is withdrawn from the variable volume chamber 11c at a constant rate, expanding the recovery chamber 11b. The amount of used dialysate flowing into the recovery chamber 11b becomes greater than the amount of fresh dialysate flowing out from the supply chamber 11a, creating a pressure difference in the dialyzer 2 and removing excess fluid from the patient. Then, as shown in Figure 3(a), when the fresh dialysate is completely discharged from the supply chamber 11a into the supply passage 8, the control means C stops the movement of the piston 32 of the positive displacement pump 13A, thereby ending the water removal operation.

[0018] Next, Figures 3(b) to 3(e) show the water supply and drainage process, which is switched over from the water supply and recovery process in Figure 3(a). First, Figure 3(b) corresponds to period (b) in Figure 5(A), and shows the state in which a small amount of dialysis water is supplied to the supply chamber 11a. Specifically, in Figure 3(a), from the state where the supply chamber 11a has reached its minimum volume, the supply valve V2 of the dialysis water passage 5 and the drain valve V12 of the drain passage 10 are opened, while the supply valve V6 of the supply passage 8 and the recovery valve V10 of the recovery passage 9 are closed. At this time, the A concentrate supply valve V4 of the A concentrate passage 6 and the B concentrate supply valve V5 of the B concentrate passage 7 are closed. In this state, the connection between the first dialysate container 11 and the dialyzer 2 is released, and the second dialysate container 12 is connected to the dialyzer 2 to form a sealed circuit. When the first on / off valve V1 of the dialysate water passage 5 is opened, dialysate water flows into the supply chamber 11a by the supply pump 22. However, as shown in period (b) of Figure 5(A), there is no retraction of the piston 32 during this period, and since it is set to be extremely short, a very small amount of dialysis water flows into the supply chamber 11a and a very small amount of used dialysis fluid is discharged from the recovery chamber 11b. As a result, the supply chamber 11a and the recovery chamber 11b, which had formed a sealed circuit in the liquid supply and recovery process, become open, and the pressure is released.

[0019] Next, Figure 3(c) shows the state of the concentrate supply operation, in which concentrate B is supplied to the dialysis water passage 5. Specifically, from the state shown in Figure 3(b), the first on / off valve V1 of the dialysis water passage 5 is closed, the drain valve V12 of the drain passage 10 is closed, and the B concentrate supply valve V5 of the B concentrate passage 7 is opened. Then, as shown in period (c) of Figure 5(A), by retracting the piston 32 in that state, a predetermined amount of liquid is drawn out from the variable volume chamber 11c and the volume is reduced. At this time, since the recovery valve V10 and the drain valve V12 are closed, the volume of the recovery chamber 11b does not change, and only the supply chamber 11a expands. As a result, dialysis water flows from the dialysis water passage 5 into the supply chamber 11a, and B concentrate is supplied by being drawn from the B concentrate container 24 to the dialysis water passage 5 via the B concentrate passage 7. When the piston 32 stops retracting, the flow of concentrate B also stops, and as a result, an amount of concentrate B corresponding to the increase in the volume of the enlarged supply chamber 11a, that is, the amount of liquid drawn out from the variable volume chamber 11c, is supplied from the concentrate B passage 7. At this time, some of the B concentrate will remain in the dialysis water passage 5 between the connection point of the B concentrate supply valve V5 and the supply chamber 11a.

[0020] Next, Figure 3(d) shows the state of the concentrate supply operation, in which concentrate A is subsequently supplied to the dialysis water passage 5. Specifically, from the state shown in Figure 3(c), the first on / off valve V1 of the dialysis water passage 5 is kept closed, the B concentrate supply valve V5 of the B concentrate passage 7 is closed, and the A concentrate supply valve V4 of the A concentrate passage 6 is opened. Then, as shown in period (d) of Figure 5(A), the piston 32 is further retracted in that state to draw a predetermined amount of liquid out of the variable volume chamber 11c and reduce its volume. As a result, the B concentrate that remained in the dialysis water passage 5 flows into the supply chamber 11a, and the A concentrate is supplied by being drawn from the A concentrate container 23 into the dialysis water passage 5 via the A concentrate passage 6. Subsequently, when the piston 32 stops retracting, the flow of concentrate A also stops, and as a result, an amount of concentrate A corresponding to the increase in the volume of the expanded supply chamber 11a, that is, the amount of liquid drawn out from the variable volume chamber 11c, is supplied from the concentrate A container 23 via the concentrate A passage 6. At this time, some of the A concentrate will remain in the dialysis water passage 5 between the connection point of the A concentrate supply valve V4 and the supply chamber 11a.

[0021] Finally, Figure 3(e) shows the state in which dialysis water is supplied to the supply chamber 11a, and fresh dialysis fluid is prepared by mixing the dialysis fluid concentrate and dialysis water inside the supply chamber 11a. Specifically, from the state shown in Figure 3(d), the A stock solution supply valve V4 is closed, the first on / off valve V1 of the dialysis water passage 5 is opened, and the drain valve V12 of the drain passage 10, which had been closed, is opened. As a result, the dialysis water supplied by the liquid supply pump 22 flows through the dialysis water passage 5 and is supplied to the supply chamber 11a along with the retained concentrate A. Inside the supply chamber 11a, concentrate A and concentrate B are mixed with the dialysis water and diluted to a predetermined concentration, thereby preparing fresh dialysis fluid. On the other hand, when the B concentrate, A concentrate, and dialysis water flow into the supply chamber 11a, the volume of the recovery chamber 11b decreases as the volume of the supply chamber 11a increases, and the used dialysis fluid contained in the recovery chamber 11b is discharged into the drainage passage 10. Then, as shown in Figure 3(e), when the supply chamber 11a is filled with fresh dialysate, the recovery chamber 11b reaches its minimum volume, and the used dialysate is completely discharged into the drainage passage 10.

[0022] On the other hand, in Figure 3(e), as shown in period (e) of Figure 5(A), the piston 32 is moved to the origin position in parallel with the operation of supplying dialysis water to the supply chamber 11a, thereby returning the liquid that has been extracted up to that point to the variable volume chamber 11c and restoring the variable volume chamber 11c to its origin volume. Here, at the end of period (d), the volume of the variable volume chamber 11c is such that after the water removal operation in the fluid supply and recovery process shown in Figure 3(a) is completed, the process switches to the water supply and drainage process and the stock solution supply operation shown in Figures 3(c) and 3(d) is performed, drawing stock solution B and stock solution A into the dialysis water passage 5. Therefore, at the end of period (d), the volume of the variable volume chamber 11c is reduced relative to the origin volume, and the piston 32 is retracted to about 3 / 4 of its total retraction distance. Therefore, in the water supply and drainage process, the liquid is returned to the variable volume chamber 11c to restore it to its original volume, in preparation for the next water supply and recovery process. During this period (e), as shown in Figure 3(e), although the liquid supply valve V2 is opened and dialysis water is supplied to the supply chamber 11a, the drain valve V12 is also open, which expands the variable volume chamber 11c towards the recovery chamber 11B, allowing liquid to be injected into the variable volume chamber 11c, and the liquid is returned to the variable volume chamber 11c to restore it to its original volume. Furthermore, the supply of dialysis water to the supply chamber 11a continues even after the variable volume chamber 11c returns to its original volume, and continues until the process switches from the water supply and drainage process to the next fluid recovery process. This allows fresh dialysis fluid to be prepared by mixing the B concentrate and A concentrate already supplied to the supply chamber 11a with the dialysis water, stirring thoroughly, and diluting to a predetermined concentration.

[0023] Next, the operation when the water removal speed is set to the maximum will be explained using Figures 1, 4, and 5. In the case of the normal water removal rate already explained, during the liquid recovery process shown in period (a) of Figures 3(a) and 5(A), only a small amount of liquid (about 1 / 5) is drawn out from the variable volume chamber 11c. Therefore, although the volume of the variable volume chamber 11c decreases relative to the origin volume, it maintains a certain volume. In other words, the amount of liquid remaining in the variable volume chamber 11c (residual liquid amount) is greater than the amount of liquid withdrawn from the variable volume chamber 11c during the supply operation of concentrate B and concentrate A shown in Figures 3(c)(d) and 5(A) during period (c)(d) in the subsequent water supply and drainage process. This makes it possible to withdraw concentrate B and concentrate A without returning the liquid to the variable volume chamber 11c. In contrast, when the water removal rate is set to the maximum, as shown in period (a) of Figures 4(a) and 5(B), the piston 32 is moved to the reverse end during the liquid supply and recovery process to extract all the liquid from the variable volume chamber 11c, so the volume of the variable volume chamber 11c becomes the minimum volume. When the volume of the variable volume chamber 11c reaches its minimum, there is no remaining liquid, and it becomes impossible to draw any more liquid from the variable volume chamber 11c. As a result, it becomes impossible to draw out concentrate B and concentrate A during the concentrate supply operation in the next water supply and drainage process.

[0024] Therefore, before transitioning from the liquid supply and recovery process to the liquid supply and drainage process and starting the stock solution supply operation, the control means C controls the operation of the positive displacement pump 13A so as to return the amount of liquid that is insufficient during the stock solution supply operation, i.e., the insufficient amount of liquid, from the positive displacement pump 13A to the variable volume chamber 11c. Specifically, as shown in Figure 4(b), the supply valve V6 and the recovery valve V10 are closed, while the liquid supply valve V2 and the drain valve V12 are opened, switching from the liquid supply and recovery process to the liquid supply and drain process. This opens the sealed circuit, allowing the liquid to be returned from the positive displacement pump 13A to the variable volume chamber 11c, and dialysis water is supplied to the supply chamber 11a from the dialysis water passage 5. Furthermore, as shown in period (b) of Figure 5(B), the control means C operates the positive displacement pump 13A to advance the piston 32, thereby increasing the volume of the variable volume chamber 11c by returning the insufficient liquid back to the variable volume chamber 11c. Here, the insufficient amount corresponds to the amount of liquid withdrawn from the variable volume chamber 11c to supply the B concentrate and A concentrate during the concentrate supply operation. While it is possible to return a slightly larger amount of liquid than the insufficient amount to the variable volume chamber 11c as a margin, this will reduce the amount of dialysis water supplied after the concentrate supply operation, so it is desirable to return the same amount as the insufficient amount.

[0025] Then, after the insufficient liquid is returned to the variable volume chamber 11c, the concentrate supply operation is started. As shown in Figures 4(c) and 4(d), the drain valve V12 and the first on / off valve V1 are closed, and first the B concentrate supply valve V5 is opened to retract the piston 32 by a predetermined amount corresponding to the supply amount of B concentrate, drawing in B concentrate from the B concentrate container 24. Next, the B concentrate supply valve V5 is closed and the A concentrate supply valve V4 is opened, and the piston 32 is retracted by a predetermined amount corresponding to the supply amount of A concentrate, drawing in A concentrate from the A concentrate container. This state is shown in periods (c) and (d) of Figure 5(B), and in particular, as shown in period (d), the piston 32 reaches its retracted end again, and the variable volume chamber 11c becomes its minimum volume, as shown in Figure 4(d).

[0026] Next, Figure 4(e) shows the state in which, as explained earlier in Figure 3(e), after the stock solution supply operation, the A stock solution supply valve V4 is closed, the drain valve V12 and the first on / off valve V1 are opened, and while dialysis water is supplied to the supply chamber 11a, the piston 32 is advanced to the origin position to return all the liquid back, and the variable volume chamber 11c is returned to its origin volume. In this state, as shown in period (e) of Figure 5(B), during the remaining period of the water supply and drainage process after the stock solution supply operation, the supply of dialysis water continues even after the piston 32 has advanced to the origin position, thereby preparing fresh dialysis fluid of a predetermined concentration inside the supply chamber 11a. In this way, even if the amount of liquid to be extracted from the variable volume chamber 11c during the concentrate supply operation in the water supply and drainage process is insufficient because the entire amount of liquid is extracted from the variable volume chamber 11c during the water removal operation in the water supply and drainage process, the concentrate supply operation can be performed by returning the insufficient amount to the variable volume chamber 11c during the period before the concentrate supply operation (b). In this case as well, since only the amount that was removed during the water removal operation is returned, rather than the entire amount, the period before the stock solution supply operation (b) can be made as short as possible, and the period after the stock solution supply operation (e) can be made longer. As a result, it becomes possible to supply as much dialysis water as possible to the supply chamber 11a during period (e), and the stirring performance due to water supply can be improved.

[0027] Next, we will explain the case where, as shown in Figures 4 and 5(B), the maximum water removal rate is set, and although the amount of liquid remaining in the variable volume chamber 11c is not reduced to zero, the amount of liquid remaining after the water removal operation is insufficient to perform the undiluted liquid supply operation. In other words, in the case of the maximum water removal rate shown in Figure 5(B), there is no remaining liquid in the variable volume chamber 11c at the end of the liquid supply recovery process. Therefore, the deficit is equal to the amount of liquid required for the liquid supply operation to draw out the liquids from the variable volume chamber 11c in order to supply the liquids A and B. However, if there is remaining liquid in the variable volume chamber 11c, the deficit will be the difference between this remaining liquid and the amount of liquid required for the liquid supply operation. This deficit will be returned from the positive displacement pump 13A to the variable volume chamber 11c during the period before the liquid supply operation (b). In contrast, if the amount of liquid remaining after the water removal operation is equal to or greater than the amount of liquid required for the undiluted liquid supply operation, there is no shortage, and as with the case of the normal water removal rate in Figure 5(A), there is no need to return the shortage during period (b).

[0028] Thus, the operation of the piston 32 of the positive displacement pump 13A during the water supply and drainage process (b) differs not only depending on whether or not a shortage occurs, but also on the amount of the shortage. In response to this, the control means C controls the operation of the positive displacement pump 13A according to the dialysis conditions set in advance for each treatment. In other words, the control means C determines the fluid removal rate from the pre-set treatment time and fluid removal amount, and further sets the duration of the fluid supply and recovery process and the fluid supply and drainage process from the set flow rate of fresh dialysate supplied to the dialyzer 2. Then, from these water removal rates and the duration of each process, the amount of liquid to be extracted from the variable volume chamber 11c (water removal and extraction amount) during the period (a) of each liquid supply and recovery process can be determined. Furthermore, from the ratio of stock solution A, stock solution B, and dialysis water of the fresh dialysis fluid to be prepared, the amount of liquid to be withdrawn from the variable volume chamber 11c to supply stock solution A and the amount of liquid to be withdrawn from the variable volume chamber 11c to supply stock solution B can be determined during periods (c) and (d) in the fluid supply and recovery process, and the total amount of liquid (amount of stock solution withdrawn) can be determined by adding these together. Furthermore, as long as the sum of the amount of water removed and the amount of undiluted liquid removed does not exceed the amount of liquid contained in the variable volume chamber 11c of the origin volume, no shortage will occur, and the duration (b) of the water supply and drainage process can be minimized, similar to the case of the normal water removal rate shown in Figure 5(A). In contrast, if the sum of the amount of water removed and the amount of undiluted liquid removed exceeds the amount of liquid contained in the variable volume chamber 11c, the excess amount is treated as a deficit, and the liquid is returned from the positive displacement pump 13A to the variable volume chamber 11c during the water supply and drainage process (b). Furthermore, if the amount of water removed is equal to the amount of liquid contained in the variable volume chamber 11c, then, similar to the case of the maximum water removal rate shown in Figure 5(B), an amount of liquid equal to the amount of raw liquid removed is returned from the positive displacement pump 13A to the variable volume chamber 11c during the water supply and drainage process (b).

[0029] The liquid is then added to and removed from these variable volume chambers 11c by moving the piston 32 of the positive displacement pump 13A, and the amount of movement of the piston 32 is determined according to the amount of water removed, the amount of undiluted liquid removed, and the deficit. The amount of movement of the piston 32 is controlled by the rotation angle (speed) of the motor 33. The control means C determines the amount of fluid removed, the amount of undiluted fluid removed, and any deficits from the pre-set dialysis conditions, and controls the operation of the motor 33 of the positive displacement pump 13A in the fluid supply and recovery process and the fluid supply and drainage process accordingly. In the control means C, the rotation angle of the motor 33 corresponding to the amount of retraction of the piston 32 for extracting the amount of water removed from the variable volume chamber 11c, the rotation angle of the motor 33 corresponding to the amount of retraction of the piston 32 for extracting the amount of undiluted liquid, and the rotation angle of the motor 33 required to move the piston 32 from the retracted end to the origin position are recognized as the number of pulses output for each predetermined rotation angle. The control means C then compares the sum of the number of pulses corresponding to the amount of water removed and the number of pulses corresponding to the amount of undiluted liquid removed with the number of pulses corresponding to the amount of movement of the piston 32 from its retracted end to its origin position to determine whether or not to return liquid from the positive displacement pump 13A to the variable volume chamber 11c during the above period (b), and if it is necessary to return the liquid, it determines the number of pulses corresponding to the deficit. As a result, the control means C rotates the motor 33 forward according to the number of pulses determined during the above period (b) to advance the piston 32 and return the liquid contained in the cylinder chamber 31a to the variable volume chamber 11c. Furthermore, during the period (e) after the concentrate supply operation, when returning the variable volume chamber 11c to its original volume, the control means C rotates the motor 33 forward to advance the piston 32 once the concentrate supply operation is completed. When the origin sensor 35 detects the guide rod 34 fixed to the ball nut 32 on the piston 32, the motor 33 is stopped, thereby returning the variable volume chamber 11c to its original volume. The movement speed of the piston 32, i.e., the rotational speed of the motor 33, is set based on the water removal speed during the water removal operation. For cases where a deficiency is returned during the water supply and drainage process, during the supply of undiluted liquid, and when returning to the origin position, the control means C has pre-set the speed so that it fits within the entire duration (b) to (e) of the water supply and drainage process.

[0030] In Figure 5, we compare the case of the normal water removal rate (A) and the case of the maximum water removal rate (B) with the conventional method (C). First, in (A), where the normal water removal rate is set, almost the entire required amount of dialysis water is supplied during period (e), which is the period of supplying the stock solution (c) and (d). In contrast, in (B), where the maximum water removal rate is set, nearly one-third of the required amount of dialysis water is supplied during period (b), which is before the supplying of the stock solution, and the remainder is supplied during period (e), which is after the supplying of the stock solution. In other words, the period (e) in (B) is shorter than the period (e) in (A), and (B) has lower stirring performance than (A), but it has higher stirring performance than the conventional method in (C). In other words, in the conventional method (C) shown in Figure 5, the retraction distance of the piston 32 in the case of a normal water removal rate is shown by a solid line during period (a), which is the liquid supply and recovery process, and the case of the maximum water removal rate is shown by a dotted line. In the following period (b), in the case of any water removal rate, the piston 32 is advanced to the origin position to return the variable volume chamber 11c to its origin volume. The time set here as the period (b) before the liquid supply operation is set to be sufficient to return the entire amount of liquid from the positive displacement pump 13A to the variable displacement chamber 11c, assuming that the entire amount of liquid is removed from the variable volume chamber during the water removal operation in the liquid supply and recovery process, that is, assuming the amount of retraction of the piston 32 shown by the dotted line in the liquid supply and recovery process. In other words, in the conventional method, even when the water removal rate shown by the solid line in the water supply and recovery process is normal, the duration (b) in the water supply and drainage process is set to the same time as when the maximum water removal rate shown by the dotted line is maximum. Therefore, during period (b), regardless of the amount of piston 32 retraction, i.e., the amount of residual liquid in the variable volume chamber 11c, approximately half the volume of dialysis water in the supply chamber 11a was always supplied. As a result, the period (e) after the stock solution supply operation period was always shortened, and insufficient dialysis water was supplied, resulting in inadequate agitation. In contrast, in the present invention, when the maximum water removal rate shown in Figure 5(B) is set, the duration (e) of the water supply and drainage process is minimized, but it can be made longer than the conventional method shown in Figure 5(C). Furthermore, it is rare for the maximum water removal rate shown in Figure 5(B) to be set, and even if a water removal rate higher than the normal water removal rate shown in Figure 5(A) is set, it will be lower than the maximum water removal rate. In either case, the duration of the water supply and drainage process (e) in the conventional method (C) can be made longer, thus improving the stirring performance compared to the conventional method. [Explanation of symbols]

[0031] 1 Liquid circuit 2 Dialyzer 5 Dialysis water passage 8 Fluid supply passage 9. Recovery passage 10. Drainage passage 11 First dialysate container 12 Second dialysate container 11a, 12a Supply room 11b, 12b Recovery room 11c, 12c Variable volume chamber; 13A, 13B Positive displacement pump 23 A stock solution container (stock solution supply means) 24 B stock solution container (stock solution supply means) C Control device

Claims

[Claim 1] The dialysis fluid container comprises a supply chamber, a recovery chamber, and a variable volume chamber formed inside; a dialysis water passage connected to the supply chamber for supplying dialysis water; a concentrate supply means connected to the dialysis water passage for supplying concentrate for dialysis; a supply passage connected to the supply chamber for supplying fresh dialysis fluid to a dialyzer; a recovery passage connected to the recovery chamber for recovering used dialysis fluid from the dialyzer; a drainage passage connected to the recovery chamber for draining used dialysis fluid; and a positive displacement pump for supplying and draining liquid into the variable volume chamber. The above-mentioned dialysis fluid container alternately performs a fluid supply and recovery process in which fresh dialysis fluid is supplied from the supply chamber to the dialyzer and used dialysis fluid is collected in the recovery chamber, and a water supply and drainage process in which dialysis water is supplied to the supply chamber and used dialysis fluid is drained from the recovery chamber. In the above-mentioned fluid supply and recovery process, a predetermined amount of liquid is extracted from the variable volume chamber with the origin volume using the positive displacement pump, and a water removal operation is performed to reduce the volume of the variable volume chamber while collecting used dialysate into the recovery chamber. In the above-mentioned water supply and drainage process, a predetermined amount of liquid is extracted from the variable volume chamber using the positive displacement pump, reducing the volume of the variable volume chamber, and a stock solution supply operation is performed to supply the stock solution to the dialysate water passage from the stock solution supply means. In the above-mentioned dialysis apparatus, dialysate water and dialysate are mixed in the supply chamber to prepare fresh dialysate. The above-mentioned positive displacement pump, if the amount of liquid in the variable volume chamber is sufficient when performing the above-mentioned stock solution supply operation, returns the liquid extracted in the above-mentioned water removal operation and the liquid extracted in the above-mentioned stock solution supply operation back to the variable volume chamber to restore the variable volume chamber to its original volume while supplying dialysis water to the supply chamber after the stock solution supply operation in the above-mentioned water supply and drainage process. A dialysis apparatus characterized in that, when the amount of liquid in the variable volume chamber becomes insufficient due to the execution of the water removal operation during the execution of the stock solution supply operation, the insufficient liquid is returned to the variable volume chamber from the positive displacement pump while dialysis water is supplied to the supply chamber before the stock solution supply operation in the water supply and drainage process, thereby enabling the stock solution supply operation to be performed, and while dialysis water is supplied to the supply chamber after the stock solution supply operation, the liquid extracted in the water removal operation and the liquid extracted in the stock solution supply operation are returned to the variable volume chamber to restore the variable volume chamber to its original volume.

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