Medical system and liquid circulation system

Abstract

The purpose of the present invention is to provide a medical system and a liquid circulation system capable of efficiently delivering a liquid to a treatment area of a brain while suppressing variation in intracranial pressure. This medical system comprises a control unit that sets a first period 211 for injecting a liquid into a body cavity and not discharging the liquid from the body cavity, sets a second period 212 for discharging the liquid from the body cavity without injecting the liquid into the body cavity, and alternately repeats the first period 211 and the second period 212, executing control for setting the injection amount of the liquid in the first period 211 to be substantially the same as the discharge amount of the liquid in the second period 212.

Description

Medical and Fluid Circulation Systems

[0001] The present invention relates to a medical system and a fluid circulation system used in the treatment of brain diseases.

[0002] When a brain disease, such as cerebral infarction, occurs, the blood flow that supplies oxygen to brain cells is blocked, which can damage the brain cells. Therefore, when a cerebral infarction occurs, early reperfusion of blood flow is necessary. One proposed treatment for cerebral infarction is to inject a highly oxygenated solution, such as oxygenated cerebrospinal fluid, into the body cavity where the cerebrospinal fluid is present in the patient, thereby directly supplying oxygen to oxygen-deficient brain cells.

[0003] Patent Document 1 discloses a catheter system capable of injecting and suctioning a liquid into and from a living body using a single lumen. The catheter system described in Patent Document 1 includes a catheter, an injection drive unit that supplies fluid to an injection port through a lumen in a tubular body, a suction drive unit that suctions the fluid from a suction port through the lumen in the tubular body, a detection unit that detects the state of intracranial pressure, and a control unit that controls the injection drive unit and the suction drive unit. The suction port of the catheter is closed when the injection port of the catheter is open. The injection port of the catheter is also closed when the suction port of the catheter is open. The control unit alternately operates the injection drive unit and the suction drive unit so that the state of intracranial pressure detected by the detection unit is within a certain range.

[0004] When a liquid such as a highly oxygenated solution is injected into a body cavity for the purpose of treating a brain disease, it is necessary to maintain intracranial pressure within a certain range. The normal range of intracranial pressure is approximately 5 mmHg or more and 15 mmHg or less. Fluctuations in the pressure from the inside of the skull to the spinal cavity can cause brain damage. For example, if intracranial pressure rises to 20 mmHg or more, intracranial hypertension (i.e., various symptoms caused by stress on brain tissue) can occur. On the other hand, if intracranial pressure falls to 5 mmHg or less, hypocerebrospinal fluid pressure syndrome (i.e., various symptoms caused by the inability to maintain the position of brain tissue) can occur.

[0005] Body cavities containing cerebrospinal fluid (e.g., the subarachnoid space and ventricles) are nearly closed spaces. Therefore, in order to maintain a constant intracranial pressure, the amount of cerebrospinal fluid in the body cavities must be kept within a certain range. To maintain the amount of cerebrospinal fluid in the body cavities within a certain range, it is necessary to quickly drain the same amount of cerebrospinal fluid as the amount of fluid injected into the body cavity.

[0006] However, when a liquid is injected into a body cavity by circulating it with a pump through an infusion catheter and a drainage catheter inserted into the subarachnoid space near the lumbar spine, depending on the timing of the injection and drainage, a flow (i.e., a local steady flow) of the liquid injected into the body cavity from the infusion catheter's inlet toward the drainage catheter's outlet can form. This results in a problem in that the flow of liquid from the infusion catheter's inlet toward the treatment area of ​​the brain is small, making it difficult to efficiently deliver the liquid to the treatment area of ​​the brain.

[0007] To solve this problem, it is conceivable to position the inlet of the injection catheter near the brain and the outlet of the drainage catheter near the lumbar vertebrae, thereby providing sufficient distance between the inlet and outlet and minimizing the effects of local steady flow. However, if an attempt is made to insert a catheter close to the brain, the catheter would have to be inserted a long distance into the curved subarachnoid space, which is surrounded by nerve tissue such as the spinal cord. Inserting such a catheter deep into the subarachnoid space carries the risk of damaging the nerve tissue, so it is desirable to keep the catheter insertion length as short as possible.

[0008] Furthermore, when injecting a fluid into a body cavity by circulating the fluid using a pump through an infusion catheter and an outflow catheter inserted into the subarachnoid space near the lumbar spine, maintaining a constant volume of cerebrospinal fluid within the body cavity requires controlling parameters such as the cross-sectional area of ​​the lumen of the infusion catheter and the outflow catheter, the fluid resistance due to the surface properties of the lumen, and their lengths to maintain a constant volume of infusion and outflow. However, variations in the aforementioned parameters occur due to variations in the catheter manufacturing process and deformation of the cross-sectional shape of the catheter lumen during use. This makes it difficult to maintain a constant volume of infusion and outflow.

[0009] In addition, it is desirable that the liquid circulation circuit be a closed system to prevent infection. However, if the liquid circulation circuit is a closed system, there is a risk that the total volume of the liquid may increase compared to the initial volume due to the generation of bubbles in the circulation circuit due to the cavitation phenomenon, or that the total volume of the liquid may decrease compared to the initial volume due to the loss of water due to evaporation during the process of oxygenating the cerebrospinal fluid. If the total volume of the liquid increases or decreases in a closed circulation circuit, there is a risk that intracranial pressure may not be maintained within a certain range.

[0010] International Publication No. 2021 / 192539

[0011] The present invention has been made in consideration of the above circumstances, and aims to provide a medical system and a fluid circulation system that can efficiently deliver fluid to a treatment area of ​​the brain while suppressing fluctuations in intracranial pressure.

[0012] The present invention is (1) a medical system for injecting a liquid into a body cavity in which cerebrospinal fluid of a subject is present and discharging the liquid present in the body cavity from the body cavity, the medical system being characterized in that it sets a first period in which the liquid is injected into the body cavity but not discharged from the body cavity, and a second period in which the liquid is not injected into the body cavity but is discharged from the body cavity, and is equipped with a control unit that executes control to alternately repeat the first period and the second period and set the amount of liquid injected in the first period to be substantially the same as the amount of liquid discharged in the second period.

[0013] According to the medical system (1) described above, the control unit injects a liquid into the body cavity during a first period without draining the liquid from the body cavity. Furthermore, the control unit does not inject the liquid into the body cavity during a second period, but drains the liquid from the body cavity. The control unit alternates between the first period and the second period, making the amount of liquid injected and the amount of liquid drained substantially equal. This allows the same amount of liquid to be injected and drained alternately, as long as the allowable fluctuation range of intracranial pressure is not exceeded. Therefore, the liquid injection and drainage are not performed simultaneously, and the generation of a local steady flow of the liquid injected from the inlet into the body cavity toward the outlet can be suppressed. Therefore, the liquid injected into the body cavity flows toward the treatment region of the brain according to the injection direction and injection flow rate. Furthermore, turbulence caused by resistance between the liquid injected into the body cavity and the cerebrospinal fluid in the body cavity agitates the liquid and the cerebrospinal fluid. Furthermore, diffusion due to differences in the concentration of oxygen and other components contained in the liquid progresses. This allows the liquid to be efficiently delivered to the treatment region of the brain. Furthermore, because the volume of fluid injected is substantially the same as the volume of fluid removed, the volume of cerebrospinal fluid in the body cavity can be kept within a certain range, thereby preventing large fluctuations in intracranial pressure.

[0014] (2) In the medical system of (1) above, it is preferable that the period from the start of the first period to the end of the second period is substantially constant. According to the medical system of (2) above, at least one of agitation of the liquid and cerebrospinal fluid and diffusion due to differences in the concentration of oxygen or the like contained in the liquid proceeds stably. This allows the liquid to be efficiently delivered to the treatment area of ​​the brain. Furthermore, the amount of cerebrospinal fluid in the body cavity can be stably maintained within a certain range. This allows fluctuations in intracranial pressure to be suppressed.

[0015] (3) In the medical system of (1) or (2), it is preferable that the control unit further sets a third period between the first period and the second period, during which the liquid is not injected into the body cavity and the liquid is not discharged from the body cavity. According to the medical system of (3), diffusion due to differences in concentration of oxygen and the like contained in the liquid progresses more rapidly depending on the length of the third period. This allows the liquid to be delivered to the treatment area of ​​the brain more efficiently.

[0016] (4) In the medical system of (3), the third period is preferably longer than the first period. According to the medical system of (4), the time during which diffusion due to differences in concentration of oxygen and the like contained in the liquid progresses is longer than the time during which the liquid is injected. This allows for more efficient delivery of the liquid to the treatment area of ​​the brain.

[0017] (5) In the medical system of (3) or (4), the third period is preferably 1 second or longer. This medical system ensures time for diffusion due to differences in the concentration of oxygen and other components contained in the liquid to proceed. This allows the liquid to be efficiently delivered to the treatment area of ​​the brain.

[0018] (6) In any of the medical systems (3) to (6) above, it is preferable that the control unit further sets the third period between the second period and the first period, and that the first time of the third period set between the first period and the second period is longer than the second time of the third period set between the second period and the first period.

[0019] According to the medical system of (6) above, the first time of the pause period (i.e., the third period) between the infusion and discharge of the liquid is longer than the second time of the pause period (i.e., the third period) between the discharge and infusion of the liquid. This more reliably prevents the occurrence of a local steady flow of the liquid injected from the inlet into the body cavity toward the discharge port, and ensures that time is provided for diffusion due to differences in the concentration of oxygen and other substances contained in the liquid to proceed. This allows for more efficient delivery of the liquid to the treatment area of ​​the brain.

[0020] (7) In any of the medical systems (1) to (6) above, it is preferable that the discharge rate of the liquid during the second period is slower than the injection rate of the liquid during the first period. According to the medical system of (7) above, the discharge rate of the liquid during the second period is slower than the injection rate of the liquid during the first period. This reduces the speed at which the liquid injected from the injection port into the body cavity moves toward the outlet, ensuring time for the liquid to diffuse toward the brain immediately after being injected from the injection port into the body cavity. This allows the liquid to be efficiently delivered to the treatment area of ​​the brain.

[0021] (8) In any of the medical systems (1) to (7) above, the control unit preferably initially sets a zeroth period during which the liquid is injected or discharged in an amount less than the injection amount in the first period and the discharge amount in the second period, and starts a period between the first period and the second period in which the liquid moves in a different direction from the zeroth period after the zeroth period. According to the medical system of (8) above, by reducing the volume change in the subarachnoid space during the initial zeroth period, the volume change in the subarachnoid space during the first and second periods after the zeroth period fluctuates within a range including the original volume. Therefore, the volume change can be prevented from exceeding the allowable fluctuation range. This allows fluctuations in intracranial pressure to be kept within the allowable fluctuation range.

[0022] (9) In the medical system of (8) above, it is preferable that the injection amount in the zero period is substantially half of the injection amount in the first period, and the discharge amount in the zero period is substantially half of the discharge amount in the second period. According to the medical system of (9) above, it is possible to more reliably prevent intracranial pressure from exceeding the allowable fluctuation range due to the initial injection of liquid in the first period. This makes it possible to more reliably keep fluctuations in intracranial pressure within the allowable fluctuation range.

[0023] (10) In any of the medical systems (1) to (9) above, it is preferable that the control unit, at the end of the control, executes control to inject the liquid into the body cavity to bring the amount of cerebrospinal fluid close to the amount that was present in the body cavity at the start of the control, or to discharge the liquid from the body cavity to bring the amount of cerebrospinal fluid close to the amount that was present in the body cavity at the start of the control.

[0024] According to the medical system of (10) above, the amount of cerebrospinal fluid at the end of control of the medical system can be set to be substantially the same as the amount of cerebrospinal fluid present in the body cavity at the start of control of the medical system. Therefore, the intracranial pressure at the end of control of the medical system can be set to be substantially the same as the intracranial pressure at the start of control of the medical system. This makes it possible to suppress fluctuations in intracranial pressure between the end of control of the medical system and the start of control of the medical system.

[0025] (11) Any of the medical systems (1) to (10) above further includes an injection catheter for injecting the liquid into the body cavity and a discharge catheter for discharging the liquid from the body cavity, and it is preferable that the distance between the tip of the injection catheter and the tip of the discharge catheter is 30 centimeters or less when the control starts to be executed.

[0026] According to the medical system of (11) above, because the injection and discharge of the liquid are alternately repeated in equal amounts, even if the distance between the tip of the injection catheter and the tip of the discharge catheter is 30 centimeters or less at the start of control execution, the occurrence of a local steady flow of the liquid injected from the injection port into the body cavity toward the discharge port can be suppressed, thereby enabling the liquid to be efficiently delivered to the treatment area of ​​the brain without inserting the injection catheter deeply into the living body.

[0027] (12) In the medical system of (1) above, it is preferable that the control unit further executes control to deflate a balloon that is placed in the body cavity and is capable of expanding and contracting during the first period, and to expand the balloon during the second period.

[0028] According to the medical system of (12) above, the control unit injects a liquid into the body cavity during a first period without draining the liquid from the body cavity, and further deflates a balloon disposed within the body cavity by an amount equal to the volume of the liquid. This allows the control unit to suppress fluctuations in the volume of the body cavity as a closed space during the first period when the liquid is being injected into the body cavity, thereby suppressing fluctuations in intracranial pressure. Furthermore, the control unit does not inject a liquid into the body cavity during a second period when the liquid is being drained from the body cavity, and further expands a balloon disposed within the body cavity by an amount equal to the volume of the liquid. This allows the control unit to suppress fluctuations in the volume of the body cavity as a closed space during the second period when the liquid is being drained from the body cavity, thereby suppressing fluctuations in intracranial pressure.

[0029] During the first and second periods, slight volume fluctuations may occur due to the difference between the amount of fluid discharged and the amount of balloon inflation, or the difference between the amount of fluid injected and the amount of balloon deflation. In this case, the volume fluctuation is within the tolerance range of the subject's body cavity's own volume fluctuation capacity, i.e., the compliance required to maintain intracavity pressure. Therefore, the body deforms in response to a decrease or increase in the amount of fluid, thereby canceling out the volume fluctuations while maintaining a constant intracranial pressure.

[0030] In addition, in the medical system described in (12), the inflation and deflation of a balloon can be used as an auxiliary measure. By inflating and deflating the balloon to a volume smaller than the volume of fluid delivered and discharged, the volume fluctuations within the body cavity are partially counteracted, and the volume fluctuations are suppressed to fall within the range that can be handled by the compliance of the living body. This not only enables the delivery and deflation of a larger volume of fluid that exceeds the high compliance range, but also achieves the same effect as when the balloon is inflated and deflated by the same volume as the volume of fluid delivered and discharged.

[0031] (13) In the medical system of (12) above, it is preferable that the control unit simultaneously injects the liquid and contracts the balloon during the first period, and simultaneously discharges the liquid and expands the balloon during the second period.

[0032] According to the medical system of (13) above, the control unit simultaneously injects the liquid and deflates the balloon during the first period. The control unit can further suppress fluctuations in the volume of the body cavity during the first period when the liquid is injected into the body cavity. As a result, fluctuations in intracranial pressure during the first period are further suppressed. Furthermore, the control unit simultaneously drains the liquid and expands the balloon during the second period. As a result, the control unit can further suppress fluctuations in the volume of the body cavity during the second period when the liquid is drained from the body cavity. As a result, fluctuations in intracranial pressure during the second period are further suppressed.

[0033] (14) In the medical system of (12) or (13) above, it is preferable that the control unit sets the amount of contraction of the balloon during the first period to be substantially equal to the amount of liquid injected, and sets the amount of expansion of the balloon during the second period to be substantially equal to the amount of liquid discharged.

[0034] According to the medical system of (14) above, the control unit sets the balloon deflation amount during the first period to be substantially equal to the amount of liquid injected. Therefore, the amount of liquid increased within the body cavity (i.e., the volume) is substantially equal to the amount by which the balloon deflated within the body cavity (i.e., the volume). Therefore, the volume of the body cavity does not change substantially during the first period. This more reliably suppresses fluctuations in intracranial pressure during the first period. Furthermore, the control unit sets the balloon inflation amount during the second period to be substantially equal to the amount by which the liquid is discharged. Therefore, the amount of liquid decreased within the body cavity (i.e., the volume) is substantially equal to the amount by which the balloon expanded within the body cavity (i.e., the volume). Therefore, the volume of the body cavity does not change substantially during the second period. This more reliably suppresses fluctuations in intracranial pressure during the second period.

[0035] (15) In any of the medical systems (12) to (14) above, it is preferable that the control unit further sets a third period between the first period and the second period and between the second period and the first period, during which the liquid is not injected into the body cavity and the liquid is not discharged from the body cavity, and maintains the balloon in the contracted state during the third period between the first period and the second period, and maintains the balloon in the expanded state during the third period between the second period and the first period.

[0036] According to the medical system of (15) above, diffusion due to differences in the concentration of oxygen and the like contained in the liquid progresses more rapidly depending on the length of the third period, thereby enabling more efficient delivery of the liquid to the treatment area of ​​the brain.

[0037] The present invention (16) is a liquid circulation system that circulates a liquid by injecting the liquid into a body cavity in which cerebrospinal fluid is present and discharging the liquid outside the body cavity, the liquid circulation system comprising: an injection catheter that injects the liquid into the body cavity; a discharge catheter that discharges the liquid from inside the body cavity to outside the body cavity; a liquid supply line connected to the injection catheter; a liquid drainage line connected to the discharge catheter; a first liquid supply unit provided on the liquid supply line and moving the liquid; a second liquid supply unit provided on the drainage line and moving the liquid; and a single control unit that controls the first liquid supply unit and the second liquid supply unit.

[0038] According to the liquid circulation system of (16), the system is divided into a circuit including the infusion catheter and the drainage catheter (i.e., the biological circuit section) and a circuit including the fluid supply line connected to the infusion catheter and the drainage line connected to the drainage catheter (i.e., the system circuit section). Furthermore, a first fluid supply section provided on the fluid supply line for moving the liquid, and a second fluid supply section provided on the drainage line for moving the liquid, function as a fluid supply section shared by the biological circuit section and the system circuit section. This configuration of the liquid circulation system allows the system circuit section to respond to increases in the total volume of liquid caused by cavitation and decreases in the total volume of liquid caused by evaporation while maintaining the conditions on the biological side, thereby minimizing increases and decreases in the volume of liquid within the biological circuit. This suppresses fluctuations in intracranial pressure.

[0039] (17) It is preferable that the liquid circulation system of (16) above further comprises a liquid storage section for storing at least one of the liquid to be injected into the body cavity and the liquid discharged from the body cavity, and a liquid treatment device provided in the liquid delivery line between the liquid storage section and the first liquid delivery section for treating the liquid.

[0040] (18) In the liquid circulation system of (16), the liquid treatment device is preferably an oxygenation device that adds oxygen to the liquid discharged outside the body cavity. According to the liquid circulation system of (18), it is possible to efficiently deliver a highly oxygenated solution to a treatment region of the brain while suppressing fluctuations in intracranial pressure.

[0041] (19) In the liquid circulation system of any one of (16) to (18) above, it is preferable that the control unit repeatedly drives the first liquid delivery unit and the second liquid delivery unit alternately.

[0042] According to the fluid circulation system described in (19) above, the injection and discharge of fluid are alternately repeated in equal amounts as long as the intracranial pressure does not exceed the allowable fluctuation range. Therefore, the injection and discharge of fluid are not performed simultaneously, and the occurrence of a local steady flow, i.e., a local steady flow of fluid injected into the body cavity from the injection port toward the discharge port, which occurs when the injection and discharge of fluid are performed simultaneously, can be suppressed. Therefore, the fluid injected into the body cavity flows toward the treatment area of ​​the brain according to the injection direction and injection flow rate. Furthermore, turbulence caused by resistance between the injected fluid and the cerebrospinal fluid in the body cavity agitates the fluid and the cerebrospinal fluid. Furthermore, diffusion due to differences in the concentration of oxygen and other components contained in the fluid progresses. This allows the fluid to be efficiently delivered to the treatment area of ​​the brain.

[0043] (20) In any of the liquid circulation systems (16) to (19) above, it is preferable that the control unit controls the sum of the injection amount of the liquid ejected while the first liquid delivery unit is operating continuously or intermittently without starting the second liquid delivery unit, and the discharge amount of the liquid ejected while the second liquid delivery unit is operating continuously or intermittently without starting the first liquid delivery unit, within a certain range from the time of initial start-up.

[0044] According to the liquid circulation system of (20) above, fluctuations in the amount of cerebrospinal fluid from the initial activation of the first liquid delivery unit and the second liquid delivery unit can be kept within a certain range. This makes it possible to more reliably prevent intracranial pressure from exceeding the allowable fluctuation range. This makes it possible to more reliably keep fluctuations in intracranial pressure within the allowable fluctuation range.

[0045] (21) It is preferable that the liquid circulation system of (16) above further comprises a balloon that is placed in the body cavity and is capable of expanding and contracting, and that the control unit further controls the expansion and contraction of the balloon.

[0046] According to the liquid circulation system of (21) above, the control unit can suppress fluctuations in the volume of the body cavity as a closed space by controlling the operation of the first liquid delivery unit, the operation of the second liquid delivery unit, and the expansion and contraction of the balloon placed in the body cavity, thereby suppressing fluctuations in intracranial pressure.

[0047] (22) The liquid circulation system of (21) above has a balloon fluid storage section that stores an expansion fluid for expanding the balloon, and further includes a balloon driving section that performs the operations of injecting the expansion fluid from the balloon fluid storage section into the balloon and sending the expansion fluid from inside the balloon into the balloon fluid storage section, and it is preferable that the balloon driving section injects the expansion fluid into the balloon to expand the balloon and discharges the expansion fluid from the balloon to deflate the balloon.

[0048] According to the liquid circulation system of (22) above, a balloon driver is further provided. The balloon driver has a balloon fluid reservoir that stores an inflation fluid for inflating the balloon, and performs operations of injecting the inflation fluid from the balloon fluid reservoir into the balloon and discharging the inflation fluid from the balloon. The balloon driver injects the inflation fluid into the balloon to inflate it. Meanwhile, the balloon driver discharges the inflation fluid from the balloon to deflate it. This allows the balloon driver to individually control the inflation and deflation of the balloon. This allows the timing and speed of fluid injection and balloon deflation, as well as the timing and speed of fluid discharge and balloon inflation, to be more appropriately set. This further suppresses fluctuations in intracranial pressure.

[0049] According to the present invention, it is possible to provide a medical system and a fluid circulation system that can efficiently deliver fluid to a treatment area of ​​the brain while suppressing fluctuations in intracranial pressure.

[0050] FIG. 1 is a schematic diagram illustrating an overview of a medical system according to an embodiment of the present invention. FIG. 2 is a plan view illustrating the vicinity of an inlet of an injection catheter according to this embodiment. FIG. 3 is a plan view illustrating the vicinity of an outlet of a discharge catheter according to this embodiment. FIG. 4 is a cross-sectional view taken along the section B-B of FIG. 3. FIG. 5 is a schematic diagram illustrating the flow of liquid occurring in a body cavity immediately after the start of liquid circulation. FIG. 6 is a schematic diagram illustrating the flow of liquid occurring in a body cavity during liquid circulation. FIG. 7 is a schematic diagram illustrating the flow of liquid occurring in a body cavity after liquid circulation has been stopped. FIG. 8 is a graph illustrating the relationship between the amount of injection and the amount of discharge, and the amount of fluid in a body cavity, according to the control of this embodiment. FIG. 9 is a schematic diagram illustrating the flow of liquid occurring in a body cavity during injection under the control of this embodiment. FIG. 10 is a schematic diagram illustrating the flow of liquid occurring in a body cavity during stoppage of control of this embodiment. FIG. 11 is a graph illustrating the relationship between the amount of injection and the amount of discharge, and the amount of fluid in a body cavity, according to a first modification of the control of this embodiment. FIG. 11 is a graph illustrating the relationship between the amount of injection and the amount of discharge, and the amount of fluid in a body cavity, according to a second modification of the control of this embodiment. FIG. 12 is a graph illustrating the relationship between the amount of injection and the amount of discharge, and the amount of fluid in a body cavity, according to a third modification of the control of this embodiment. FIG. 1 is a schematic diagram illustrating an outline of an experiment conducted by the present inventor. FIG. 2 is a table illustrating an example of the results of an experiment conducted by the present inventor. FIG. 3 is a photograph showing the state of an experiment conducted by the present inventor. FIG. 4 is a schematic diagram illustrating an outline of a liquid circulation system according to the present embodiment. FIG. 5 is a schematic diagram illustrating the operation of a liquid circulation system according to the present embodiment. FIG. 6 is a schematic diagram illustrating the operation of a liquid circulation system according to the present embodiment. FIG. 7 is a schematic diagram illustrating the operation of a liquid circulation system according to the present embodiment. FIG. 8 is a schematic diagram illustrating the operation of a liquid circulation system according to the present embodiment. FIG. 9 is a schematic diagram illustrating the operation of a liquid circulation system according to a first modified example of the present embodiment. FIG. 10 is a schematic diagram illustrating the operation of a liquid circulation system according to the present modified example. FIG. 11 is a schematic diagram illustrating the operation of a liquid circulation system according to the present modified example. FIG. 12 is a schematic diagram illustrating the outline of a liquid circulation system according to a second modified example of the present embodiment. FIG. 13 is a schematic diagram illustrating a modified example of a medical device according to the present embodiment. FIG. 14 is a graph showing the relationship between injection amount, discharge amount, balloon volume, and intrabody cavity fluid amount under control of a medical system according to the second modified example of the present embodiment.

[0051] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the embodiments described below are preferred specific examples of the present invention, and therefore various technically preferable limitations are applied, but the scope of the present invention is not limited to these aspects unless otherwise specified in the following description to the effect that the present invention is limited. Furthermore, in each drawing, similar components are given the same reference numerals, and detailed descriptions thereof will be omitted as appropriate.

[0052] FIG. 1 is a schematic diagram illustrating an overview of a medical system according to an embodiment of the present invention. A medical system 2 according to this embodiment injects a liquid into a body cavity containing cerebrospinal fluid (CSF) of a subject and drains the liquid from the body cavity. CSF is primarily present in the subarachnoid space and ventricles. In other words, the body cavities containing CSF include the subarachnoid space and ventricles.

[0053] As shown in FIG. 1 , the medical system 2 includes a control unit 21, a pump 22, and a medical device 5. The control unit 21 is connected to the pump 22 and transmits a control signal to the pump 22 to control its operation. The pump 22 operates based on the control signal transmitted from the control unit 21, aspirating and discharging cerebrospinal fluid from the subject's body cavity via the medical device 5, as indicated by arrow A1 in FIG. 1 . The cerebrospinal fluid discharged from the body cavity by the pump 22 is converted into a liquid with a higher oxygen concentration (i.e., a highly oxygenated solution) than that of normal cerebrospinal fluid, for example, by an oxygenation mechanism (not shown). Then, as indicated by arrow A2 in FIG. 1 , the pump 22 injects the liquid into the body cavity via the medical device 5.

[0054] The liquid injected into the body cavity is not limited to a highly oxygenated solution. For example, the liquid injected into the body cavity may be a drug-containing liquid obtained by adding a drug to cerebrospinal fluid during extracorporeal circulation, or may be cerebrospinal fluid filtered to remove undesirable substances during extracorporeal circulation. Alternatively, the liquid injected into the body cavity may be cerebrospinal fluid that has been subjected to some kind of treatment, such as irradiation with energy or heating, before being returned to the body cavity. For convenience of explanation, the following description may cite an example in which the liquid injected into the body cavity is a highly oxygenated solution. Furthermore, lactated Ringer's solution may be used as a substitute for cerebrospinal fluid during the initial stages of treatment. In this embodiment, cerebrospinal fluid, artificial cerebrospinal fluid such as lactated Ringer's solution, and a mixture of cerebrospinal fluid and lactated Ringer's solution may be collectively referred to as a liquid.

[0055] As shown in FIG. 1 , the medical device 5 includes a drainage catheter 51 and an injection catheter 52. The device is inserted into the subarachnoid space near the lumbar vertebrae with the patient in a lateral position. For safety during insertion, the tip of the injection catheter 52 is preferably positioned between the sixth thoracic vertebra (T6) and the first lumbar vertebra (L1). For example, as indicated by arrow A11 in FIG. 1 , the drainage catheter 51 aspirates cerebrospinal fluid present in the body cavity through an outlet 511 and discharges it outside the body cavity. For example, as indicated by arrow A13 in FIG. 1 , the injection catheter 52 injects liquid from an inlet 521 into a body cavity, such as the subarachnoid space, where cerebrospinal fluid is present. Note that, as an example, in FIG. 1 , the drainage catheter 51 and the injection catheter 52 are inserted from the first lumbar vertebra (L1), and the outlet 511 at the tip of the drainage catheter 51 is positioned near the eleventh thoracic vertebra (T11). However, the insertion positions and distal end positions of the drainage catheter 51 and the injection catheter 52 are not particularly limited as long as they are positioned to ensure safety during insertion.

[0056] Fig. 2 is a plan view showing the vicinity of the inlet of the injection catheter of this embodiment, Fig. 3 is a plan view showing the vicinity of the outlet of the discharge catheter of this embodiment, and Fig. 4 is a cross-sectional view taken along the line B-B in Fig. 3.

[0057] As shown in FIG. 3 , the distal end of the drainage catheter 51 opens as a drainage port 511 and is positioned in the subarachnoid space near the lumbar vertebrae. For example, as indicated by arrows A11 and A12 in FIG. 3 , the drainage catheter 51 is inserted into the subarachnoid space of the subject, and cerebrospinal fluid present in the subarachnoid space near the lumbar vertebrae is aspirated through the drainage port 511 into a space 53 (see FIG. 4 ) between the inner lumen 513 of the drainage catheter 51 and the outer surface of the injection catheter 52. As described above with reference to FIG. 1 , the force for aspirating the cerebrospinal fluid is provided by the pump 22. Then, as indicated by arrow A1 in FIG. 1 , the drainage catheter 51 discharges the cerebrospinal fluid through the space 53 to the outside of the subject's body cavity.

[0058] The outer diameter of the injection catheter 52 is smaller than the inner diameter of the drainage catheter 51. The injection catheter 52 is positionable in the lumen 513 of the drainage catheter 51. The injection catheter 52 is not coupled to the drainage catheter 51 and is movable through the lumen 513 of the drainage catheter 51 along the longitudinal direction D1 (see FIG. 3 ) of the drainage catheter 51. Because the distal end of the drainage catheter 51 is open as the drainage port 511, as shown in FIG. 3 , the distal end of the injection catheter 52 can pass through the drainage port 511 of the drainage catheter 51.

[0059] This allows the tip of the injection catheter 52 to be exposed from the outlet 511 of the drainage catheter 51 in the longitudinal direction D1 of the drainage catheter 51. The distance in the longitudinal direction D1 between the tip of the drainage catheter 51 and the tip of the injection catheter 52 exposed from the outlet 511 of the drainage catheter 51 can be adjusted to a predetermined distance. In this specification, the "predetermined distance" can be, for example, between 0 cm and 30 cm. This can avoid risks that may arise when inserting the catheter deeply into the patient's subarachnoid space.

[0060] As shown in Fig. 2, the tip of the injection catheter 52 is opened as an injection port 521, and is placed in the subarachnoid space after passing through the outlet 511 of the drainage catheter 51. For example, as shown by arrow A13 in Fig. 2, the injection catheter 52 is inserted into the patient's subarachnoid space, and liquid is injected into the cerebrospinal fluid present in the subarachnoid space through the lumen 523 (see Fig. 4) of the injection catheter 52. Note that, as described above with reference to Fig. 1, the force for injecting the liquid into the cerebrospinal fluid is provided by the pump 22.

[0061] Next, the flow of liquid occurring in a body cavity during liquid circulation will be described with reference to the drawings. Fig. 5 is a schematic diagram illustrating the flow of liquid occurring in a body cavity immediately after liquid circulation begins. Fig. 6 is a schematic diagram illustrating the flow of liquid occurring in a body cavity during liquid circulation. Fig. 7 is a schematic diagram illustrating the flow of liquid occurring in a body cavity after liquid circulation has stopped.

[0062] As shown in Fig. 5, immediately after the start of liquid circulation, the liquid 91 injected into the body cavity through the inlet 521 of the infusion catheter 52 flows forward (i.e., toward the brain) as indicated by arrow A13 in Fig. 5, for example, until the suction flow when cerebrospinal fluid is discharged from the outlet 511 of the discharge catheter 51 reaches the inlet 521, as will be described later with reference to Fig. 6. The flow rate of the liquid 91 flowing forward is slightly higher than in the case described later with reference to Fig. 6. Furthermore, in the short period of time immediately after the start of liquid circulation, there is almost no diffusion due to differences in the concentrations of oxygen, drugs, and the like contained in the liquid (hereinafter referred to as "oxygen, etc." for convenience of explanation).

[0063] 6 , during liquid circulation, i.e., during continuous circulation of the liquid, the suction flow generated when cerebrospinal fluid is discharged from the outlet 511 of the drainage catheter 51 reaches and affects the inlet 521 of the injection catheter 52. As a result, the flow from the inlet 521 of the injection catheter 52 toward the outlet 511 of the drainage catheter 51 becomes steady. That is, as indicated by arrows A14 and A15 in FIG. 6 , a local steady flow of the liquid 91 injected into the body cavity from the inlet 521 of the injection catheter 52 toward the outlet 511 of the drainage catheter 51 occurs. As a result, the liquid 91 injected into the body cavity from the inlet 521 of the injection catheter 52 hardly flows forward (i.e., in the direction toward the brain).

[0064] Furthermore, due to the influence of the local steady flow, the diffusion of oxygen and the like contained in the liquid 91 toward the brain side slows down compared to immediately after the start of liquid circulation. Due to the influence of the local steady flow, the liquid 91 diffuses toward the lumbar side due to the difference in concentration of oxygen and the like contained in the liquid 91, and is discharged outside the body cavity from the discharge port 511 of the discharge catheter 51.

[0065] 7, after the liquid circulation stops, the local steady flow that occurred during the liquid circulation disappears, and therefore, oxygen and other substances contained in the liquid 91 diffuse toward the brain and lumbar spine, as indicated by arrows A16 and A17 in FIG.

[0066] 6, when continuous circulation of the liquid is performed, a local steady flow of the liquid 91 injected into the body cavity from the inlet 521 of the injection catheter 52 is generated toward the outlet 511 of the discharge catheter 51. This results in a small flow of the liquid 91 from the inlet 521 of the injection catheter 52 toward the treatment region of the brain, making it difficult to efficiently deliver the liquid 91 to the treatment region of the brain.

[0067] Therefore, the control unit 21 of the medical system 2 according to this embodiment sets a first period during which the liquid 91 is injected into the body cavity but not discharged from the body cavity, and a second period during which the liquid 91 is not injected into the body cavity but is discharged from the body cavity. By alternately repeating the first and second periods, the liquid 91 can be efficiently delivered to the brain without generating the local steady flow. Furthermore, the control unit 21 sets the amount of the liquid 91 injected during the first period to be substantially the same as the amount of the liquid 91 discharged during the second period, thereby suppressing increases or decreases in the amount of cerebrospinal fluid originally present in the body cavity and suppressing the pressure within the body cavity within an acceptable range. Details of the control of the medical system 2 according to this embodiment will be described below with reference to the drawings.

[0068] Fig. 8 is a graph showing the relationship between the injection amount, the discharge amount, and the amount of fluid in the body cavity under the control of this embodiment. Fig. 9 is a schematic diagram illustrating the flow of fluid that occurs in the body cavity during injection under the control of this embodiment. Fig. 10 is a schematic diagram illustrating the flow of fluid that occurs in the body cavity while the control of this embodiment is stopped. Fig. 11 is a schematic diagram illustrating the flow of fluid that occurs in the body cavity during discharge under the control of this embodiment.

[0069] The horizontal axis of the graph shown in Figure 8 represents time. The vertical axis of the graph shown in Figure 8 represents the change in fluid volume. Specifically, the "injection volume" shown in Figure 8 represents the cumulative volume of fluid 91 injected into the body cavity from the start of control execution. The "discharge volume" shown in Figure 8 represents the cumulative volume of cerebrospinal fluid discharged outside the body cavity from the start of control execution. The "volume of fluid in the body cavity" shown in Figure 8 represents the change in the cerebrospinal fluid present in the body cavity at the start of control execution.

[0070] 8 , in the control of this embodiment, the control unit 21 sets a first period 211 in which the liquid 91 is injected into the body cavity but not discharged from the body cavity, and a second period 212 in which the liquid 91 is not injected into the body cavity but is discharged from the body cavity. That is, in the first period 211, only the injection of the liquid 91 into the body cavity is performed. On the other hand, in the second period 212, only the discharge of the liquid 91 from the body cavity is performed.

[0071] 8, the control unit 21 alternately repeats a first period 211 and a second period 212. The control unit 21 also sets the amount of liquid 91 injected during the first period 211 to be substantially the same as the amount of liquid 91 discharged during the second period 212. As a result, the injection and discharge of the liquid 91 are alternately repeated in the same amount as long as the allowable fluctuation range of the intracranial pressure is not exceeded.

[0072] In the control of the medical system 2 according to this embodiment, the liquid 91 is not injected and discharged simultaneously, and the occurrence of a local steady flow of the liquid 91 injected into the body cavity from the inlet 521 of the injection catheter 52 toward the outlet 511 of the discharge catheter 51 can be suppressed.

[0073] As shown in FIG. 9 , during the first period 211, the liquid 91 injected into the body cavity through the inlet 521 of the injection catheter 52 flows toward the brain in accordance with the injection direction and injection flow rate. Furthermore, as indicated by arrow A21 in FIG. 9 , turbulence caused by resistance between the liquid 91 injected into the body cavity through the inlet 521 of the injection catheter 52 and the cerebrospinal fluid in the body cavity causes agitation of the liquid 91 and the cerebrospinal fluid. Furthermore, as indicated by arrows A22 and A23 in FIG. 9 , diffusion due to differences in the concentrations of oxygen and other components contained in the liquid 91 progresses. This allows the liquid to be efficiently delivered to the treatment region of the brain. Furthermore, because the amount of liquid 91 injected during the first period 211 is substantially the same as the amount of liquid 91 discharged during the second period 212, the amount of liquid present in the body cavity is maintained within a certain range. This allows fluctuations in intracranial pressure to be kept within an acceptable range.

[0074] 11 , during the second period 212, the same amount of liquid 91 as the amount of liquid 91 injected into the body cavity from the inlet 521 of the injection catheter 52 flows toward the outlet 511 of the discharge catheter 51 and is sucked into the outlet 511 of the discharge catheter 51. Furthermore, while the liquid 91 injected into the body cavity from the inlet 521 of the injection catheter 52 is entirely pulled back toward the outlet 511 of the discharge catheter 51, the liquid 91 that has spread in the injection direction remains in the body cavity, for example, as shown by arrow A27 in FIG.

[0075] As shown in FIG. 8 , the controller 21 further sets a third period 213, during which the liquid 91 is not injected into the body cavity and the liquid 91 is not discharged from the body cavity, between the first period 211 and the second period 212 and between the second period 212 and the first period 211. That is, during the third period 213, the injection of the liquid 91 into the body cavity and the discharge of the liquid 91 from the body cavity are simultaneously stopped. The controller 21 repeats the first period 211, the third period 213, the second period 212, and the third period 213 in this order. During the third period, as shown by arrows A24 and A25 in FIG. 10 , for example, diffusion due to differences in the concentrations of oxygen and the like contained in the liquid 91 progresses toward the brain side and the lumbar side according to the duration of the third period 213 (i.e., the stop time). The duration of the third period 213 is preferably until the flow caused by the immediately preceding injection or discharge has disappeared, and specifically, is preferably 1 second or more.

[0076] As described above, the control of the medical system 2 according to this embodiment prevents simultaneous injection and discharge of the liquid 91, thereby preventing the liquid 91 injected into the body cavity from the inlet 521 of the injection catheter 52 toward the outlet 511 of the discharge catheter 51. Therefore, the liquid 91 injected into the body cavity flows toward the treatment region of the brain according to the injection direction and injection flow rate. Furthermore, turbulence caused by resistance between the liquid injected into the body cavity and the cerebrospinal fluid in the body cavity agitates the liquid and the cerebrospinal fluid. Furthermore, diffusion due to differences in the concentrations of oxygen and other components contained in the liquid 91 progresses. This allows the liquid to be efficiently delivered to the treatment region of the brain. Furthermore, because the amount of liquid 91 injected is substantially the same as the amount of liquid 91 discharged, the amount of liquid present in the body cavity can be maintained within a certain range. This allows fluctuations in intracranial pressure to be kept within an acceptable range.

[0077] The period from the start of the first period 211 to the end of the second period 212 is substantially constant during execution of the control. Therefore, at least one of agitation of the liquid 91 and cerebrospinal fluid and diffusion due to differences in the concentration of oxygen and other substances contained in the liquid 91 proceeds stably. This allows for efficient delivery of a therapeutic substance (oxygen, etc.) to the treatment region of the brain. Furthermore, the amount of liquid present in the body cavity can be stably maintained within a certain range. This allows fluctuations in intracranial pressure to be suppressed within an acceptable range.

[0078] As described above, the control unit 21 further sets a third period 213, during which the liquid 91 is not injected into the body cavity and is not discharged from the body cavity, between the first period 211 and the second period 212 and between the second period 212 and the first period 211. Therefore, the diffusion of oxygen and other substances contained in the liquid 91 progresses more rapidly depending on the length of the third period. This allows the liquid to be delivered to the treatment region of the brain more efficiently.

[0079] The discharge rate of the liquid 91 in the second period 212 may be slower than the injection rate of the liquid 91 in the first period 211. In this case, since the discharge rate in the second period 212 is slower than the injection rate in the first period 211, it is possible to prevent the liquid 91, immediately after being injected into the body cavity from the inlet 521 of the injection catheter 52, from being discharged out of the body cavity from the outlet 511 of the discharge catheter 51. This allows the therapeutic substance (oxygen, etc.) to be efficiently delivered to the treatment region of the brain.

[0080] 8 , the control unit 21 sets a second period 212 at or near the end of the control, and executes control to discharge the liquid from the body cavity to approximate the amount of cerebrospinal fluid present in the body cavity at the start of the control. This allows the control unit 21 to set the amount of liquid present in the body cavity at the end of the control of the medical system 2 to be substantially the same as the amount of cerebrospinal fluid present in the body cavity at the start of the control of the medical system 2. Therefore, the intracranial pressure at the end of the control of the medical system 2 can be set to be substantially the same as the intracranial pressure at the start of the control of the medical system 2. This suppresses fluctuations in intracranial pressure between the end of the control of the medical system 2 and the start of the control of the medical system 2.

[0081] The control unit 21 may control the first period 211 and the second period 212 in reverse order, starting with the second period 212 (i.e., discharge of the liquid 91). In this case, the first period 211 is set at or shortly before the end of the control, and control is performed to inject the liquid into the body cavity so that the amount of cerebrospinal fluid approaches the amount present in the body cavity at the start of the control. Even in this case, the same effect as when the control unit 21 sets the second period 212 at or shortly before the end of the control can be obtained.

[0082] Next, a modification of the control of the medical system according to this embodiment will be described with reference to the drawings. Fig. 12 is a graph showing the relationship between the infusion rate, the discharge rate, and the amount of fluid in the body cavity according to a first modification of the control of this embodiment. The horizontal and vertical axes of the graph shown in Fig. 12, as well as the "infusion rate," "discharge rate," and "amount of fluid in the body cavity" shown in Fig. 12, are as described above with reference to Fig. 8.

[0083] 12 , in a first modified example of the control of this embodiment, the control unit 21 repeats a first period 211, a third period 213, a second period 212, and a third period 213 in this order. As shown in FIG. 12 , the duration of the third period 213, which is set between the first period 211 and the second period 212, is longer than the duration of the first period 211. As a result, the time during which diffusion due to the difference in concentration of oxygen and the like contained in the liquid 91 progresses is longer than the injection time of the liquid 91. This allows the liquid to be delivered to the treatment region of the brain more efficiently.

[0084] 12 , the duration (first time) of the third period 213, which is set between the first period 211 and the second period 212, is longer than the duration (second time) of the third period 213, which is set between the second period 212 and the first period 211. This more reliably prevents discharge of the liquid 91 into the body cavity from the inlet 521 of the injection catheter 52 before the flow of the liquid 91 stops, ensuring time for diffusion due to differences in the concentrations of oxygen and other substances contained in the liquid 91 to proceed. This allows for more efficient delivery of the liquid to the treatment region of the brain. Furthermore, shortening the duration (second time) of the third period 213, which is set between the second period 212 and the first period 211, allows for the timing of the subsequent injection of the liquid 91 containing oxygen and other therapeutic substances to be accelerated, which is expected to improve the therapeutic effect.

[0085] 13 is a graph showing the relationship between the infusion rate, the discharge rate, and the amount of fluid in the body cavity according to the second modification of the control of this embodiment. The horizontal and vertical axes of the graph shown in FIG. 13, as well as the "infusion rate," "discharge rate," and "amount of fluid in the body cavity" shown in FIG. 13, are as described above with reference to FIG. 8.

[0086] 13 , in the second modified example of the control of this embodiment, the control unit 21 initially sets a zeroth period 211a in which a smaller amount of liquid 91 is injected than the amount injected in the first period 211, and then repeats a third period 213, a second period 212, a third period 213, and a first period 211 in this order. As shown in FIG. 13 , the amount of liquid 91 injected in the initial zeroth period 211a is smaller than the amount of liquid 91 injected in the second and subsequent first periods 211. For example, the amount of liquid 91 injected in the initial zeroth period 211a is substantially half of the amount of liquid 91 injected in the second and subsequent first periods 211.

[0087] 13 , the control unit 21 sets the injection time of the liquid 91 in the initial zero period 211a to be shorter than the injection time of the liquid 91 in the second or subsequent first periods 211, thereby setting the injection amount of the liquid 91 in the initial zero period 211a to be less than the injection amount of the liquid 91 in the second or subsequent first periods 211. Alternatively, the control unit 21 may set the injection rate of the liquid 91 in the initial zero period 211a to be slower than the injection rate of the liquid 91 in the second or subsequent first periods 211, thereby setting the injection amount of the liquid 91 in the initial zero period 211a to be less than the injection amount of the liquid 91 in the second or subsequent first periods 211. Furthermore, by discharging the same amount of liquid as in the zero period 211a at or shortly before the end of the control, the final pressure in the body cavity can be made substantially the same as the pressure at the start of the control.

[0088] According to this modification, the amount of cerebrospinal fluid in the body cavity fluctuates above and below the original amount, so the deviation in intracranial pressure from the initial value at the start of control can be smaller than in the above-described embodiment. Alternatively, the amount of liquid 91 containing the therapeutic substance injected at one time can be increased from the second injection onward. This allows the fluctuation in intracranial pressure to be kept within the allowable fluctuation range, resulting in a higher therapeutic effect. In this modification, as in the modification shown in FIG. 12 , the duration (first time) of the pause period (third period) between injection and discharge may be set longer than the duration (second time) of the pause period (third period) between discharge and injection.

[0089] 14 is a graph showing the relationship between the infusion rate, the discharge rate, and the amount of fluid in the body cavity according to the third modification of the control of this embodiment. The horizontal and vertical axes of the graph shown in FIG. 14, as well as the "infusion rate," "discharge rate," and "amount of fluid in the body cavity" shown in FIG. 14, are as described above with reference to FIG. 8.

[0090] 14 , in the third modified example of the control of this embodiment, the control unit 21 initially sets a zeroth period 212a in which a smaller amount of liquid 91 is discharged than the amount discharged in the second period 212, and then repeats a third period 213, a first period 211, a third period 213, and a second period 212 in this order. As shown in FIG. 14 , the amount of liquid 91 discharged in the initial zeroth period 212a is less than the amount of liquid 91 discharged in the second and subsequent second periods 212. For example, the amount of liquid 91 discharged in the initial zeroth period 212a is substantially half of the amount of liquid 91 discharged in the second and subsequent second periods 212.

[0091] 14 , the control unit 21 sets the discharge time of the liquid 91 in the initial zero period 212a to be shorter than the discharge time of the liquid 91 in the second or subsequent second periods 212, thereby setting the discharge amount of the liquid 91 in the initial zero period 212a to be less than the discharge amount of the liquid 91 in the second or subsequent second periods 212. Alternatively, the control unit 21 may set the discharge rate of the liquid 91 in the initial zero period 212a to be slower than the discharge rate of the liquid 91 in the second or subsequent second periods 212, thereby setting the discharge amount of the liquid 91 in the initial zero period 212a to be less than the discharge amount of the liquid 91 in the second or subsequent second periods 212. Furthermore, by injecting the same amount of liquid as in the zero period 212a at or just before the end of the control, the final pressure in the body cavity can be made substantially the same as the pressure at the start of the control.

[0092] According to this modification, the amount of cerebrospinal fluid in the body cavity fluctuates above and below the original amount, so the deviation in intracranial pressure from the initial value at the start of control can be reduced compared to the above-described embodiment. Alternatively, the amount of liquid 91 containing the therapeutic substance injected at one time can be increased compared to the above-described embodiment. This allows the fluctuation in intracranial pressure to be kept within the allowable fluctuation range, resulting in a higher therapeutic effect. In this modification, as in the modification shown in FIG. 12 , the duration (first time) of the pause period (third period) between injection and discharge may be set longer than the duration (second time) of the pause period (third period) between discharge and injection.

[0093] Next, an example of an experiment conducted by the present inventor will be described with reference to the drawings. FIG. 15 is a schematic diagram illustrating an outline of the experiment conducted by the present inventor. FIG. 16 is a table illustrating an example of the results of the experiment conducted by the present inventor. FIG. 17 is a photograph showing the state of the experiment conducted by the present inventor. FIG. 17(a) is a photograph showing the state at the start of the experiment. FIG. 17(b) is a photograph showing the state during the experiment, i.e., when the colored water 911 has reached the intermediate position of the tube 55. FIG. 17(c) is a photograph showing the state when the colored water 911 has reached the goal position. For ease of explanation, the colored water 911 is shaded in the photographs of FIGS. 17(b) and 17(c).

[0094] The inventors used a model simulating the spinal cord portion of the subarachnoid space as shown in FIGS. 17( a) to 17(c) to inject colored water 911 into tube 55 from injection port 521 of injection catheter 52, and compared the time required for colored water 911 to reach a set goal position after being injected into tube 55. In the models shown in FIGS. 17( a) to 17(c), the lumen of tube 55 is a portion simulating the subarachnoid space. The lumen of tank 56 is a portion simulating the intracranial space. The goal position is a position near the connection between tube 55 and tank 56, immediately after colored water 911 passes through tube 55 and flows into tank 56. The goal position is a portion simulating the cisterna magna.

[0095] 15, the distance in the longitudinal direction D1 (see FIG. 3) between the tip of the drainage catheter 51 (i.e., the drain port 511) and the tip of the injection catheter 52 exposed from the drainage port 511 of the drainage catheter 51 (i.e., the injection port 521) is 20 cm. Also, the distance in the longitudinal direction D1 between the injection port 521 of the injection catheter 52 and the goal position (i.e., the portion simulating the cisterna magna) is 20 cm.

[0096] The injection and discharge methods used in this experiment will be described using Figure 16. In the table shown in Figure 16, "continuous circulation" is a method in which colored water 911 is continuously injected and discharged, and is a method used as a comparative example. That is, as shown in the table shown in Figure 16, in "continuous circulation," the control unit 21 sets a period during which colored water 911 is continuously injected and discharged at a flow rate of 20 mL / min.

[0097] In the table shown in FIG. 16, "equal volume balance" refers to the injection and discharge method when the control described above with reference to FIGS. 8 to 11 is executed. That is, as shown in the table shown in FIG. 16, in "equal volume balance," the control unit 21 sets a first period 211 during which the colored water 911 is injected into the tube 55 but not discharged from the tube 55, and a second period 212 during which the colored water 911 is not injected into the tube 55 but is discharged from the tube 55. The duration of the first period 211 is 3 seconds. During the first period 211, the colored water 911 is injected into the tube 55 at a flow rate of 20 mL / min over 3 seconds, so the amount of colored water 911 injected is 1 mL. The duration of the second period 212 is 3 seconds. During the second period 212, the colored water 911 is discharged from the tube 55 at a flow rate of 20 mL / min over three seconds, resulting in a discharge volume of 1 mL. The controller 21 alternately repeats the first period 211 and the second period 212. Furthermore, during the "equal volume dispensing" mode, the controller 21 sets a third period 213, during which the colored water 911 is not injected into the tube 55 and is not discharged from the tube 55, between the first period 211 and the second period 212 and between the second period 212 and the first period 211. The duration of the third period 213 is 12 seconds. Thus, during the "equal volume dispensing" mode, the controller 21 repeats the first period 211, the third period 213, the second period 212, and the third period 213 in this order.

[0098] An example of the results of this experiment is shown in the table in FIG. 16 . That is, the colored water 911 was able to reach the goal position in both the "continuous circulation" and "constant volume delivery" methods. The time required for the colored water 911 to reach the goal position after being injected into the tube 55 was 60 minutes in the "continuous circulation" method and 0.75 minutes in the "constant volume delivery" method. The amount of colored water 911 injected after being injected into the tube 55 until it reached the goal position was 1200 mL in the "continuous circulation" method and 2 mL in the "constant volume delivery" method. The results of this experiment demonstrate that the "constant volume delivery" method can deliver the colored water 911 to the goal position more efficiently than the "continuous circulation" method.

[0099] Next, the liquid circulation system according to this embodiment will be described with reference to the drawings. Note that, in cases where the components of the liquid circulation system 3 are similar to the components of the medical system 2 described above with reference to Figures 1 to 17, redundant explanations will be omitted as appropriate, and the following description will focus on the differences.

[0100] 18 is a schematic diagram illustrating an overview of a liquid circulation system according to this embodiment. The liquid circulation system 3 according to this embodiment circulates a liquid by injecting the liquid into a body cavity and discharging it outside the body cavity. An example of the body cavity is a body cavity in which cerebrospinal fluid of a subject is present. In the explanation of the liquid circulation system 3 according to this embodiment, a case where the liquid injected into the body cavity is a highly oxygenated solution will be given as an example.

[0101] As shown in FIG. 18, the liquid circulation system 3 includes a system circuit unit 31, a biological circuit unit 32, and a pump unit 33.

[0102] The system circuit unit 31 is a unit that generates and adjusts the temperature of the highly oxygenated solution, and also adjusts the total volume of the liquid in the circulation circuit, and includes the control unit 21, a reservoir 311, an oxygenation mechanism 312, and an oxygen supply source 313. The oxygenation mechanism 312 of this embodiment is an example of the "liquid treatment device" and "oxygenation device" of the present invention.

[0103] The system circuit unit 31 further includes a first drive unit 23 and a second drive unit 24. The first drive unit 23 and the second drive unit 24 are each connected to the control unit 21 and operate based on a control signal transmitted from the control unit 21. The first drive unit 23 and the second drive unit 24 may be, for example, an actuator such as a motor. The first drive unit 23 and the second drive unit 24 may be provided in the pump unit 33.

[0104] The biological circuit section 32 is a section that injects a liquid into a body cavity and discharges the liquid to the outside of the body cavity, and includes a drainage catheter 51 and an injection catheter 52. The drainage catheter 51 and the injection catheter 52 are connected to the system circuit section 31 via the pump section 33. The drainage catheter 51 and the injection catheter 52 are as described above with reference to Figures 1 to 17.

[0105] The pump unit 33 functions as a liquid delivery unit shared by the system circuit unit 31 and the biological circuit unit 32. The pump unit 33 has a first liquid storage unit 331, a first pump 332, a first flow path switching unit 333, a second liquid storage unit 334, a second pump 335, and a second flow path switching unit 336. The first pump 332 of this embodiment is an example of the "first liquid delivery unit" of the present invention. The second pump 335 of this embodiment is an example of the "second liquid delivery unit" of the present invention. As described above, the pump unit 33 may have a first drive unit 23 and a second drive unit 24.

[0106] As shown in FIG. 18 , the oxygenation mechanism 312 is connected to the first flow path switching unit 333 via the first pipe 41. The oxygenation mechanism 312 is also connected to the reservoir 311 via the seventh pipe 47. The oxygenation mechanism 312 is further connected to the oxygen supply source 313 via the eighth pipe 48. The oxygenation mechanism 312 generates oxygenated cerebrospinal fluid by mixing cerebrospinal fluid, artificial cerebrospinal fluid such as lactated Ringer's solution, or a mixture thereof supplied from the reservoir 311 via the seventh pipe 47 with oxygen supplied from the oxygen supply source 313 via the eighth pipe. The oxygenation mechanism 312 also has a heat exchanger that adjusts the temperature of the oxygenated cerebrospinal fluid. The oxygenation mechanism 312 then supplies the oxygenated cerebrospinal fluid as a highly oxygenated solution to the first flow path switching unit 333 via the first pipe 41. The oxygenation mechanism 312 in this embodiment can be a hollow fiber oxygenator for adding oxygen to blood.

[0107] First flow path switching unit 333 is provided at the connection between first tube 41, second tube 42, and third tube 43, and is capable of switching between a flow path connecting first tube 41 and second tube 42 and a flow path connecting second tube 42 and third tube 43. Specifically, first drive unit 23 controls the operation of first flow path switching unit 333 based on a control signal transmitted from control unit 21, and switches between a flow path connecting first tube 41 and second tube 42 and a flow path connecting second tube 42 and third tube 43. First tube 41, second tube 42, and third tube 43 are examples of the "liquid delivery line" of the present invention, and are connected to first liquid storage unit 331 and injection catheter 52.

[0108] The first flow path switching unit 333 is connected to the first liquid storage unit 331 via the second pipe 42. The first pump 332 is provided in the second pipe 42. Examples of the first pump 332 include a roller pump and a syringe pump. The first pump 332 operates based on a control signal transmitted from the control unit 21, and moves the liquid toward the first liquid storage unit 331 or toward the first flow path switching unit 333.

[0109] When the first flow path switching unit 333 connects the first tube 41 and the second tube 42, and the first pump 332 is driven in the first direction, the first pump 332 supplies the liquid (i.e., the highly oxygenated solution) produced in the oxygenation mechanism 312 to the first liquid storage unit 331 through the first tube 41 and the second tube 42. As a result, the first liquid storage unit 331 stores the liquid supplied from the oxygenation mechanism 312 through the first tube 41 and the second tube 42. Note that when the first flow path switching unit 333 connects the first tube 41 and the second tube 42, and the first pump 332 is driven in the second direction, the first pump 332 supplies the liquid stored in the first liquid storage unit 331 to the oxygenation mechanism 312 through the first tube 41 and the second tube 42.

[0110] On the other hand, when the first flow path switching unit 333 connects the second tube 42 and the third tube 43 and the first pump 332 is driven in the second direction, the first pump 332 supplies the liquid stored in the first liquid storage unit 331 to the injection catheter 52 through the second tube 42 and the third tube 43.

[0111] 18 , the reservoir 311 is connected to the second flow path switching unit 336 via a sixth pipe 46. The reservoir 311 is also connected to the oxygenation mechanism 312 via a seventh pipe 47. The reservoir 311 temporarily stores the cerebrospinal fluid supplied through the sixth pipe 46. The reservoir 311 then supplies the stored cerebrospinal fluid to the oxygenation mechanism 312 through the seventh pipe 47. The reservoir 311 has a structure in which the inside and outside are connected to each other, and gas contained in the stored cerebrospinal fluid can be released to the outside. In other words, the reservoir 311 functions as an air trap.

[0112] The second flow path switching unit 336 is provided at the connection between the fourth tube 44, the fifth tube 45, and the sixth tube 46, and is capable of switching between a flow path connecting the fourth tube 44 and the fifth tube 45 and a flow path connecting the fifth tube 45 and the sixth tube 46. Specifically, the second drive unit 24 controls the operation of the second flow path switching unit 336 based on a control signal transmitted from the control unit 21, and switches between a flow path connecting the fourth tube 44 and the fifth tube 45 and a flow path connecting the fifth tube 45 and the sixth tube 46. The fourth tube 44, the fifth tube 45, and the sixth tube 46 are examples of the "drainage line" of the present invention, and are connected to the second liquid storage unit 334 and the discharge catheter 51.

[0113] The second flow path switching unit 336 is connected to the second liquid storage unit 334 via a fifth pipe 45. The second pump 335 is provided in the fifth pipe 45. Examples of the second pump 335 include a roller pump and a syringe pump. The second pump 335 operates based on a control signal transmitted from the control unit 21, and moves the liquid toward the second liquid storage unit 334 or toward the second flow path switching unit 336.

[0114] When the second pump 335 is driven in the first direction while the second flow path switching unit 336 connects the fourth tube 44 and the fifth tube 45, the second pump 335 supplies the liquid (i.e., cerebrospinal fluid) discharged from inside the body cavity to outside the body cavity through the fourth tube 44 and the fifth tube 45 to the second liquid storage unit 334. As a result, the second liquid storage unit 334 stores the liquid (i.e., cerebrospinal fluid) discharged from inside the body cavity to outside the body cavity through the fourth tube 44 and the fifth tube 45.

[0115] On the other hand, when the second flow path switching unit 336 connects the fifth tube 45 and the sixth tube 46, and the second pump 335 is driven in the first direction, the second pump 335 supplies the cerebrospinal fluid stored in the reservoir 311 to the second liquid storage unit 334 via the fifth tube 45 and the sixth tube 46. As a result, the second liquid storage unit 334 stores the liquid (i.e., cerebrospinal fluid) supplied from the reservoir 311 via the fifth tube 45 and the sixth tube 46. When the second flow path switching unit 336 connects the fifth tube 45 and the sixth tube 46, and the second pump 335 is driven in the second direction, the second pump 335 supplies the liquid (i.e., cerebrospinal fluid) stored in the second liquid storage unit 334 to the reservoir 311 via the fifth tube 45 and the sixth tube 46.

[0116] 19 to 22 are schematic diagrams illustrating the operation of the liquid circulation system according to this embodiment. The operation of the liquid circulation system 3 described with reference to FIGS. 19 to 22 is based on the control described above with reference to FIGS. 8 to 11. For ease of explanation, the control unit 21, first drive unit 23, and second drive unit 24 are omitted from FIGS. 19 to 22. The operation described below is based on the assumption that the tubes, reservoirs, and oxygenation mechanism in the circuit are primed and filled with artificial cerebrospinal fluid (AISF), such as lactated Ringer's solution, before starting operation.

[0117] 19 , in a first step, the control unit 21 sends a control signal to the first drive unit 23 to control the operation of the first flow path switching unit 333, thereby connecting the first tube 41 and the second tube 42. The control unit 21 also sends a control signal to the second drive unit 24 to control the operation of the second flow path switching unit 336, thereby connecting the fourth tube 44 and the fifth tube 45. In this state, the control unit 21 sends a control signal to the first pump 332 to drive the first pump 332 in the second direction, and sends a control signal to the second pump 335 to drive the second pump 335 in the first direction.

[0118] Then, as indicated by an arrow A41 in Fig. 19 , the liquid 91 (see Fig. 20 ) stored in the first liquid storage unit 331 is returned to the oxygenation mechanism 312 through the first tube 41 and the second tube 42. Meanwhile, as indicated by an arrow A11 in Fig. 19 , for example, cerebrospinal fluid 92 in the body cavity is sucked into the outlet 511 of the drainage catheter 51. Then, as indicated by an arrow A42 in Fig. 19 , the cerebrospinal fluid 92 is supplied to and stored in the second liquid storage unit 334 through the fourth tube 44 and the fifth tube 45.

[0119] 20 , in a second step, the control unit 21 sends a control signal to the first drive unit 23 to control the operation of the first flow path switching unit 333, thereby connecting the first tube 41 and the second tube 42. The control unit 21 also sends a control signal to the second drive unit 24 to control the operation of the second flow path switching unit 336, thereby connecting the fifth tube 45 and the sixth tube 46. In this state, the control unit 21 sends a control signal to the first pump 332 to drive the first pump 332 in the first direction, and sends a control signal to the second pump 335 to drive the second pump 335 in the second direction.

[0120] 20 , the liquid 91 (i.e., the highly oxygenated solution) produced in the oxygenation mechanism 312 is supplied to and stored in the first liquid storage section 331 through the first tube 41 and the second tube 42. Furthermore, as indicated by arrow A44 in Fig. 20 , the cerebrospinal fluid 92 stored in the second liquid storage section 334 is supplied to and stored in the reservoir 311 through the fifth tube 45 and the sixth tube 46. Furthermore, as indicated by arrow A45 in Fig. 20 , the cerebrospinal fluid 92 stored in the reservoir 311 is supplied to the oxygenation mechanism 312 through the seventh tube 47.

[0121] 21 , in a third step, the control unit 21 sends a control signal to the first drive unit 23 to control the operation of the first flow path switching unit 333, thereby connecting the second tube 42 and the third tube 43. The control unit 21 also sends a control signal to the second drive unit 24 to control the operation of the second flow path switching unit 336, thereby connecting the fifth tube 45 and the sixth tube 46. In this state, the control unit 21 sends a control signal to the first pump 332 to drive the first pump 332 in the second direction, and sends a control signal to the second pump 335 to drive the second pump 335 in the first direction.

[0122] 21 , the liquid 91 (i.e., the highly oxygenated solution) stored in the first liquid storage section 331 is supplied to the injection catheter 52 through the second tube 42 and the third tube 43. Then, as shown by arrow A13 in Fig. 21 , the liquid 91 is injected into the body cavity from the injection port 521 of the injection catheter 52. Meanwhile, as shown by arrow A47 in Fig. 21 , the cerebrospinal fluid 92 stored in the reservoir 311 is returned to the second liquid storage section 334 through the fifth tube 45 and the sixth tube 46.

[0123] 22 , in a fourth step, the control unit 21 sends a control signal to the first drive unit 23 to control the operation of the first flow path switching unit 333, thereby connecting the first tube 41 and the second tube 42. The control unit 21 also sends a control signal to the second drive unit 24 to control the operation of the second flow path switching unit 336, thereby connecting the fifth tube 45 and the sixth tube 46. In this state, the control unit 21 sends a control signal to the first pump 332 to drive the first pump 332 in the first direction, and sends a control signal to the second pump 335 to drive the second pump 335 in the second direction.

[0124] 22, the liquid 91 (i.e., the highly oxygenated solution) produced in the oxygenation mechanism 312 is supplied to and stored in the first liquid storage section 331 through the first tube 41 and the second tube 42. Furthermore, as indicated by arrow A49 in Fig. 22, the cerebrospinal fluid 92 stored in the second liquid storage section 334 is supplied to and stored in the reservoir 311 through the fifth tube 45 and the sixth tube 46. Furthermore, as indicated by arrow A51 in Fig. 22, the cerebrospinal fluid 92 stored in the reservoir 311 is supplied to the oxygenation mechanism 312 through the seventh tube 47.

[0125] In the liquid circulation system 3 according to this embodiment, the circuit for circulating the liquid is divided into a circuit including the infusion catheter 52 and the drainage catheter 51 (i.e., the biological circuit unit 32) and a circuit including the liquid supply lines (i.e., the first tube 41, the second tube 42, and the third tube 43) connected to the infusion catheter 52 and the drainage lines (i.e., the fourth tube 44, the fifth tube 45, and the sixth tube 46) connected to the drainage catheter 51 (i.e., the system circuit unit 31). Furthermore, a first pump 332 provided on the liquid supply line for moving the liquid and a second pump 335 provided on the drainage line for moving the liquid function as a shared pump for both the biological circuit unit 32 and the system circuit unit 31. This configuration of the liquid circulation system 3 allows the system circuit unit 31 to respond to increases in the total volume of the liquid caused by cavitation and decreases in the total volume of the liquid caused by evaporation while maintaining the conditions on the biological side, thereby suppressing increases and decreases in the amount of liquid in the biological circuit. This suppresses fluctuations in intracranial pressure.

[0126] The control unit 21 also repeatedly drives the first pump 332, the second pump 335, the first flow path switching unit 333, and the second flow path switching unit 336 to switch the direction of the liquid flow so as to perform the operation shown in Figures 19 to 22. As a result, the injection of liquid 91 and the discharge of cerebrospinal fluid 92 are alternately repeated in equal amounts, as long as the allowable fluctuation range of intracranial pressure is not exceeded. The control unit 21 does not control the first flow path switching unit 333 to connect the second tube 42 and the third tube 43 at the same time as the second flow path switching unit 336 to connect the fourth tube 44 and the fifth tube 45. This prevents the injection of liquid 91 and the discharge of cerebrospinal fluid 92 from occurring simultaneously, thereby preventing the occurrence of a local steady flow of liquid 91 injected into the body cavity from the inlet 521 of the injection catheter 52 toward the outlet 511 of the discharge catheter 51. Therefore, the liquid 91 injected into the body cavity flows toward the treatment region of the brain according to the injection direction and injection flow rate. Furthermore, turbulence caused by resistance between the liquid 91 injected into the body cavity and the cerebrospinal fluid 92 in the body cavity agitates the liquid 91 and the cerebrospinal fluid 92. Furthermore, diffusion progresses due to differences in the concentrations of oxygen and the like contained in the liquid 91. This allows the liquid to be efficiently delivered to the treatment area of ​​the brain.

[0127] Furthermore, the control unit 21 controls the sum of the amount of fluid injected into the biological circuit unit 32 while the first pump 332 is continuously or intermittently activated in the third step and the amount of fluid discharged from the biological circuit unit 32 while the second pump 335 is continuously or intermittently activated in the first step, from the time of initial activation, to within a certain range. This makes it possible to limit fluctuations in the amount of cerebrospinal fluid from the time of initial activation of the first pump 332 and the second pump 335 within a certain range. This more reliably prevents intracranial pressure from exceeding the allowable fluctuation range. This more reliably limits fluctuations in intracranial pressure within the allowable fluctuation range.

[0128] Furthermore, when the injection site is the subarachnoid space and the liquid injected there is a highly oxygenated solution, the highly oxygenated solution can be efficiently delivered to the treatment area of ​​the brain while suppressing fluctuations in intracranial pressure.

[0129] Next, liquid circulation systems according to modifications of this embodiment will be described with reference to the drawings. Note that, where the components of the liquid circulation system 3A according to the first modification and the liquid circulation system 3B according to the second modification are the same as the components of the liquid circulation system 3 described above with reference to Figures 18 to 22, redundant explanations will be omitted as appropriate, and the following description will focus on the differences.

[0130] 23 is a schematic diagram illustrating an overview of a liquid circulation system according to a first modified example of this embodiment. A liquid circulation system 3A according to this modified example circulates a liquid by injecting the liquid into a body cavity and discharging it outside the body cavity. An example of the body cavity is a body cavity containing cerebrospinal fluid of a subject. In describing the liquid circulation system 3A according to this modified example, a case where the liquid injected into the body cavity is a highly oxygenated solution will be described.

[0131] As shown in FIG. 23, the liquid circulation system 3A includes a system circuit section 31A, a biological circuit section 32A, and a pump section 33A.

[0132] System circuit section 31A is a section that generates and adjusts the temperature of a highly oxygenated solution, as well as adjusts the total volume of liquid in the circulation circuit, and includes control section 21, reservoir 311, oxygenation mechanism 312, and oxygen supply source 313. Oxygenation mechanism 312 of this modified example is an example of the "liquid treatment device" and "oxygenation device" of the present invention.

[0133] The biological circuit section 32A is a section that injects a liquid into a body cavity and discharges the liquid to the outside of the body cavity, and includes a drainage catheter 51 and an injection catheter 52. The drainage catheter 51 and the injection catheter 52 are connected to the pump section 33A and the system circuit section 31A that includes the reservoir 311 and the oxygenation mechanism 312. The drainage catheter 51 and the injection catheter 52 are as described above with reference to Figures 1 to 17.

[0134] The pump unit 33A functions as a liquid delivery unit shared by the system circuit unit 31A and the biological circuit unit 32A. The pump unit 33A has a first pump 332 and a second pump 335. The first pump 332 and the second pump 335 may be a roller pump that delivers liquid from a liquid delivery tube by squeezing the tube with a roller, or a peristaltic pump that delivers liquid from a tube by squeezing the tube with multiple fingers.

[0135] As shown in FIG. 23 , the oxygenation mechanism 312 is connected to the injection catheter 52 via the first tube 41. The oxygenation mechanism 312 is also connected to the reservoir 311 via the third tube 43. The oxygenation mechanism 312 is further connected to the oxygen supply source 313 via the fourth tube 44. The oxygenation mechanism 312 generates oxygenated cerebrospinal fluid by mixing cerebrospinal fluid, lactated Ringer's solution, or a mixture thereof supplied from the reservoir 311 via the third tube 43 with oxygen supplied from the oxygen supply source 313 via the fourth tube 44. The oxygenation mechanism 312 also has a heat exchanger that adjusts the temperature of the oxygenated cerebrospinal fluid. The oxygenation mechanism 312 then supplies the oxygenated cerebrospinal fluid as a highly oxygenated solution to the injection catheter 52 via the first tube 41. The oxygenation mechanism 312 in this modification can be a hollow fiber oxygenator for adding oxygen to blood.

[0136] The first pump 332 is provided on the path of the first tube 41. The first pump 332 operates based on a control signal sent from the control unit 21, and moves the liquid from the oxygenation mechanism 312 toward the injection catheter 52.

[0137] When the first pump 332 is driven, the first pump 332 supplies the liquid (i.e., the highly oxygenated solution) produced in the oxygenation mechanism 312 through the first tube 41 to the injection catheter 52, and ultimately injects it into the body cavity.

[0138] 23 , the reservoir 311 is connected to the drainage catheter 51 via the second tube 42. The reservoir 311 is also connected to the oxygenation mechanism 312 via the third tube 43. The reservoir 311 temporarily stores the cerebrospinal fluid supplied through the second tube 42. The reservoir 311 then supplies the stored cerebrospinal fluid to the oxygenation mechanism 312 via the third tube 43. The reservoir 311 has a structure in which the inside and outside are connected to each other, and gas contained in the stored cerebrospinal fluid can be released to the outside. In other words, the reservoir 311 functions as an air trap.

[0139] The second pump 335 is provided on the second tube 42. The second pump 335 operates based on a control signal sent from the control unit 21, and moves the liquid from the discharge catheter 51 toward the reservoir 311.

[0140] When the second pump 335 is driven, the second pump 335 supplies the liquid (i.e., cerebrospinal fluid) discharged from inside the body cavity to outside the body cavity through the discharge catheter 51 to the reservoir 311. As a result, the reservoir 311 stores the liquid (i.e., cerebrospinal fluid) discharged from inside the body cavity to outside the body cavity through the discharge catheter 51.

[0141] Figures 24 and 25 are schematic diagrams illustrating the operation of the liquid circulation system according to this modified example. The operation of the liquid circulation system 3A described with reference to Figures 24 and 25 is based on the control described above with reference to Figures 8 to 11. For ease of explanation, the control unit 21 is omitted from Figures 24 and 25. The operation described below will be explained assuming that the operation starts from a primed state in which the tubes, reservoirs, and oxygenation mechanisms in the circuit are filled with artificial cerebrospinal fluid (AISF) such as lactated Ringer's solution.

[0142] 24, in a first step, the control unit 21 sends a control signal to the first pump 332 to drive the first pump 332. At that time, the control unit 21 keeps the second pump 335 stationary.

[0143] 24, the liquid 91 (i.e., the highly oxygenated solution) produced in the oxygenation mechanism 312 is supplied to the injection catheter 52 through the first tube 41. Then, as shown by arrow A13 in Fig. 24, the liquid 91 is injected into the body cavity from the injection port 521 of the injection catheter 52. Furthermore, as shown by arrow A54 in Fig. 24, the cerebrospinal fluid 92 stored in the reservoir 311 is supplied to the oxygenation mechanism 312 through the third tube 43.

[0144] 25, in a second step, the control unit 21 sends a control signal to the second pump 335 to drive the second pump 335. At this time, the control unit 21 keeps the first pump 332 stationary.

[0145] 25, cerebrospinal fluid 92 in the body cavity is sucked into the outlet 511 of the drainage catheter 51. Then, as shown by arrows A55 and A56 in FIG. 25, the cerebrospinal fluid 92 is supplied to the reservoir 311 through the second tube 42 and stored therein.

[0146] In this modified liquid circulation system 3A, the circuit for circulating the liquid is divided into a circuit including the infusion catheter 52 and the drainage catheter 51 (i.e., the biological circuit unit 32A) and a circuit including the liquid supply line (i.e., the first tube 41) connected to the infusion catheter 52 and the drainage line (i.e., the second tube 42) connected to the drainage catheter 51 (i.e., the system circuit unit 31A). A first pump 332, which is provided on the liquid supply line and moves the liquid, and a second pump 335, which is provided on the drainage line and moves the liquid, function as a shared pump for both the biological circuit unit 32A and the system circuit unit 31A. This configuration of the liquid circulation system 3A allows the system circuit unit 31A to respond to increases in the total volume of liquid caused by cavitation and decreases in the total volume of liquid caused by evaporation while maintaining the conditions on the biological side, thereby suppressing increases and decreases in the amount of liquid in the biological circuit. This suppresses fluctuations in intracranial pressure.

[0147] The control unit 21 also alternately and repeatedly drives the first pump 332 and the second pump 335. Therefore, the injection of the liquid 91 and the discharge of the cerebrospinal fluid 92 are alternately repeated in equal amounts, as long as the intracranial pressure does not exceed the allowable fluctuation range. Therefore, the injection of the liquid 91 and the discharge of the cerebrospinal fluid 92 are not performed simultaneously, which can prevent the liquid 91 injected into the body cavity from the inlet 521 of the injection catheter 52 toward the outlet 511 of the discharge catheter 51. Therefore, the liquid 91 injected into the body cavity flows toward the treatment region of the brain according to the injection direction and injection flow rate. Furthermore, turbulence caused by resistance between the liquid 91 injected into the body cavity and the cerebrospinal fluid 92 in the body cavity agitates the liquid 91 and the cerebrospinal fluid 92. Furthermore, diffusion due to differences in the concentrations of oxygen and other components contained in the liquid 91 progresses. This allows the liquid to be efficiently delivered to the treatment region of the brain.

[0148] Furthermore, the control unit 21 controls the sum of the amount of fluid injected while the first pump 332 is continuously or intermittently activated without the second pump 335 being activated, and the amount of fluid discharged while the second pump 335 is continuously or intermittently activated without the first pump 332 being activated, within a certain range from the time of the initial activation. This makes it possible to limit fluctuations in the amount of cerebrospinal fluid from the time of the initial activation of the first pump 332 and the second pump 335 within a certain range. This more reliably prevents intracranial pressure from exceeding the allowable fluctuation range. This more reliably limits fluctuations in intracranial pressure within the allowable fluctuation range.

[0149] Furthermore, when the injection site is the subarachnoid space and the liquid injected there is a highly oxygenated solution, the highly oxygenated solution can be efficiently delivered to the treatment area of ​​the brain while suppressing fluctuations in intracranial pressure.

[0150] 26 is a schematic diagram illustrating an overview of a liquid circulation system according to a second modification of this embodiment. As illustrated in Fig. 26, the liquid circulation system 3B includes a system circuit unit 31B, a biological circuit unit 32B, and a pump unit 33B.

[0151] The system circuit section 31B is a section that generates and adjusts the temperature of the highly oxygenated solution, as well as adjusts the total volume of liquid in the circulation circuit, and includes a control section 21, a reservoir 311, an oxygenation mechanism 312, an oxygen supply source 313, and a heat exchanger 314.

[0152] The biological circuit unit 32B is a unit that injects liquid into the body cavity and expels the liquid from the body cavity, and includes a drainage catheter 51, an injection catheter 52, and a balloon catheter 54B. The drainage catheter 51 and the injection catheter 52 are connected to the pump unit 33B and the system circuit unit 31B, which includes the reservoir 311 and the oxygenation mechanism 312. The drainage catheter 51 and the injection catheter 52 are as described above with reference to FIGS. 1 to 17. In the liquid circulation system 3B according to this modification, the injection catheter 52 is not disposed in the lumen 513 (see FIG. 4) of the drainage catheter 51, but exists separately from the drainage catheter 51.

[0153] The biological circuit unit 32B further includes a balloon syringe 544, a balloon piston 545, and a fourth drive unit 26. The balloon syringe 544 of this modification is an example of the "balloon fluid storage unit" of the present invention, and the balloon syringe 544 and the balloon piston 545 are an example of the "balloon drive unit" of the present invention. In other words, the "balloon drive unit" of the present invention includes the balloon syringe 544 and the balloon piston 545. The fourth drive unit 26 of this modification is an example of the "piston drive unit" of the present invention.

[0154] The balloon catheter 54B has a balloon 54 at its tip. When the fourth drive unit 26 moves the balloon piston 545 in the insertion direction of the balloon syringe 544 based on a control signal transmitted from the control unit 21, the inflation fluid 93 stored in the balloon syringe 544 passes through the lumen of the balloon catheter 54B and flows toward the tip of the balloon catheter 54B. The inflation fluid 93 flowing toward the tip of the balloon catheter 54B is then supplied to the inside of the balloon 54 through a hole formed in the tip of the balloon catheter 54B. As a result, the inflation fluid 93 inflates the balloon 54. That is, the balloon 54 is inflated.

[0155] On the other hand, when the fourth drive unit 26 moves the balloon piston 545 in the direction of removing the balloon syringe 544 based on a control signal transmitted from the control unit 21, the inflation fluid 93 stored in the balloon 54 is sucked into and stored in the balloon syringe 544. This causes the inflation fluid 93 to be discharged from the balloon 54, causing the balloon 54 to contract. Note that the balloon 54 is desirably designed so as not to strongly compress the subarachnoid space near the lumbar vertebrae into which the balloon catheter 54B is inserted, even at maximum inflation.

[0156] Because the spinal cord is present inside the spinal canal, the cross-sectional area of ​​the spinal canal is not perfectly circular. Furthermore, the spine, where the spinal canal is located, has a gentle S-shaped curve overall and may deform due to aging, trauma, disease, and other factors. Therefore, the balloon 54 is preferably made of an elastic material (stretchable material) such as rubber or elastomer, and is a compliant balloon whose volume changes depending on the amount of inflation fluid injected. A compliant balloon can deform to conform to the shape of the spinal canal.

[0157] Furthermore, as shown in FIG. 26 , in this modification, only one balloon 54 is placed in the spinal canal, but this configuration is not limited to this. The balloon 54 may have, for example, a structure in which multiple inflatable portions are provided in the axial direction and the balloons are connected by a flexible material. This structure allows the axial dimension (length) of each balloon to be shortened and the outer diameter of each balloon upon inflation to be limited to a certain value or less. Furthermore, the internal spaces of each balloon may be independent, allowing inflation fluid to be injected from multiple positions separated in the axial direction. This allows for uniform inflation without changing the total volume of the entire balloon upon inflation, compared to when the balloon is composed of only one space. Furthermore, the connecting portions between the balloons serve as inflection points, allowing the balloons to more easily conform to the shape of the spinal canal.

[0158] The balloon 54 may also have a structure including multiple independent balloon catheters. Because each balloon catheter can be operated independently, the balloons can be moved and positioned to fill gaps in accordance with the shape and cross-sectional area of ​​the spinal canal. Implementing this structure reduces the risk of strong compression of a portion of the spinal cord due to the expansion of the balloon 54, thereby further reducing the load on the living body. In other words, the shape and other features of the balloon 54 are not particularly limited as long as it conforms to the shape and cross-sectional area of ​​the spinal canal and does not strongly compress the spinal cord.

[0159] The expansion fluid 93 may be a liquid or a gas. Examples of the expansion fluid 93 include physiological saline, cerebrospinal fluid, and air. The expansion fluid 93 may be a fluid different from the liquid injected into the body cavity, or may be the same fluid as the liquid injected into the body cavity.

[0160] Examples of materials for the balloon 54 include elastic materials (i.e., compliant materials) made of elastomers such as silicone and natural rubber, and rubber, but the material for the balloon 54 is not limited to these.

[0161] The pump unit 33B functions as a liquid delivery unit shared by the system circuit unit 31B and the biological circuit unit 32B. The pump unit 33B has a first pump 337 and a second pump 338. The first pump 337 of this modified example is an example of the "first liquid delivery unit" of the present invention. The second pump 338 of this modified example is an example of the "second liquid delivery unit" of the present invention. Examples of the first pump 337 and the second pump 338 include an infusion pump and a syringe pump.

[0162] As shown in FIG. 26 , the oxygenation mechanism 312 is connected to a first pump 337 via a first tube 41. The first pump 337 is connected to an infusion catheter 52. The oxygenation mechanism 312 is also connected to a reservoir 311 via a fifth tube 45. The oxygenation mechanism 312 is further connected to an oxygen supply source 313 via a sixth tube 46. The oxygenation mechanism 312 generates oxygenated cerebrospinal fluid by mixing cerebrospinal fluid, lactated Ringer's solution, or a mixture thereof supplied from the reservoir 311 via the fifth tube 45 with oxygen supplied from the oxygen supply source 313 via the sixth tube 46. The oxygenation mechanism 312 is also connected to a heat exchanger 314 via a seventh tube 47 and an eighth tube 48. The heat exchanger 314 adjusts the temperature of the oxygenated cerebrospinal fluid to approximately 37°C. The temperature adjustment by the heat exchanger is, for example, approximately 32°C to 40°C. The oxygenation mechanism 312 supplies oxygenated cerebrospinal fluid as a highly oxygenated solution to the infusion catheter 52 through the first tube 41 and the first pump 337. The oxygenation mechanism 312 in this modification can be a hollow fiber membrane oxygenator for adding oxygen to blood.

[0163] The first pump 337 is connected to the first tube 41 and the injection catheter 52, and is provided between the first tube 41 and the injection catheter 52. The first tube 41 of this modified example is an example of the "liquid delivery line" of the present invention. That is, the first tube 41 is connected to the injection catheter 52 via the first pump 337. The first pump 337 operates based on a control signal transmitted from the control unit 21, and moves the liquid from the oxygenation mechanism 312 toward the injection catheter 52.

[0164] When the first pump 337 is driven, it supplies the liquid (i.e., the highly oxygenated solution) produced in the oxygenation mechanism 312 through the first tube 41 to the injection catheter 52, and ultimately injects it into the body cavity.

[0165] 26 , the reservoir 311 is connected to the second pump 338 via a fourth pipe 44. The reservoir 311 is also connected to the oxygenation mechanism 312 via a fifth pipe 45. The reservoir 311 temporarily stores the cerebrospinal fluid supplied through the fourth pipe 44. The reservoir 311 then supplies the stored cerebrospinal fluid to the oxygenation mechanism 312 through the fifth pipe 45. The reservoir 311 has a structure in which the inside and outside are connected to each other, and gas contained in the stored cerebrospinal fluid can be released to the outside. In other words, the reservoir 311 functions as an air trap.

[0166] The second pump 338 is connected to the fourth tube 44 and the drainage catheter 51, and is disposed between the fourth tube 44 and the drainage catheter 51. The fourth tube 44 of this modified example is an example of the "drainage line" of the present invention. That is, the fourth tube 44 is connected to the drainage catheter 51 via the second pump 338. The second pump 338 operates based on a control signal transmitted from the control unit 21, and moves the liquid from the drainage catheter 51 toward the reservoir 311.

[0167] When the second pump 338 is driven, the second pump 338 supplies the liquid (i.e., cerebrospinal fluid) discharged from inside the body cavity to outside the body cavity through the discharge catheter 51 to the reservoir 311 through the fourth tube 44. As a result, the reservoir 311 stores the liquid (i.e., cerebrospinal fluid) discharged from inside the body cavity to outside the body cavity through the discharge catheter 51.

[0168] As described with respect to this modification, the liquid circulation system 3B may include a balloon catheter 54B with a balloon 54 attached to its distal end. According to the liquid circulation system 3B of this modification, the controller 21 controls the operation of the first pump 337 and the second pump 338 and the inflation and deflation of the balloon 54 disposed within the body cavity, thereby suppressing fluctuations in the volume of the body cavity as a closed space. Therefore, the body cavity can change its volume in a high-compliance region and deform in response to a decrease or increase in the amount of liquid within the body cavity. This suppresses fluctuations in intracranial pressure. Furthermore, by controlling the first pump 337 and the second pump 338 and further controlling the inflation and deflation of the balloon 54, the controller 21 can more appropriately set the timing and speed of the injection of the liquid 91 and the deflation of the balloon 54, as well as the timing and speed of the discharge of the liquid 91 and the inflation of the balloon 54. This further suppresses fluctuations in intracranial pressure.

[0169] Fig. 27 is a schematic diagram showing a modified example of the medical device of this embodiment. Note that, when the components of the medical device 5B shown in Fig. 27 are the same as the components of the medical device 5 described above with reference to Figs. 2 to 4, redundant explanations will be omitted as appropriate, and the following explanation will focus on the differences.

[0170] The medical device 5B shown in Fig. 27 has a drainage catheter 51, an injection catheter 52B, and a balloon 54, and is used in, for example, the liquid circulation system 3B described above with reference to Fig. 26. The balloon 54 is provided at the tip of the injection catheter 52B. In other words, the injection catheter 52B has the balloon 54 at its tip. The drainage catheter 51 is as described above with reference to Figs. 2 to 4.

[0171] The injection catheter 52B is disposed in the lumen 513 of the drainage catheter 51 and is not coupled to the drainage catheter 51. Therefore, the injection catheter 52B can move within the lumen 513 of the drainage catheter 51 along the longitudinal direction D1 of the drainage catheter 51. Because the distal end of the drainage catheter 51 opens as the drainage outlet 511, as shown in FIG. 27 , the distal end of the injection catheter 52B (i.e., the portion where the balloon 54 is provided) can pass through the drainage outlet 511 of the drainage catheter 51. In other words, the medical device 5B has a structure in which only the injection catheter 52B and the balloon 54 are integrally formed, and the injection catheter 52B is not coupled to the drainage catheter 51. This structure allows the positions of the injection catheter and drainage catheter to be changed, making it possible to position the injection catheter to fit the shape of the patient's spinal cavity.

[0172] The balloon 54 of this embodiment is not limited to being formed integrally with the injection catheter. For example, as in the liquid circulation system 3B described above with reference to Figure 26, the balloon 54 may be formed separately from the injection catheter and provided at the tip of a balloon catheter 54B.

[0173] In this modification, the distance D1 in the longitudinal direction between the tip of the discharge catheter 51 and the tip of the injection catheter 52B exposed from the discharge port 511 of the discharge catheter 51 is preferably, for example, 0 mm or more and 300 mm or less. ２ ~16.7mm ２ Considering that the discharge catheter 51 is placed in the spinal cavity separately from the balloon 54, the cross-sectional area is set to about half that, for example, 3.3 mm ２ ~8.3mm ２The length of the balloon 54 along the longitudinal direction D1 is, for example, about 1 mm to 300 mm, and preferably 36 mm to 200 mm. By disposing the injection catheter 52B at a position separated from the tip of the discharge catheter 51 by the length of the balloon 54, when the balloon 54 is inflated, the balloon 54 and the discharge port 511 at the tip of the discharge catheter 51 come into contact with each other, and can function without interfering with each other.

[0174] For example, as indicated by arrow A3 in Fig. 27 , the inflation fluid supplied from the base end of the injection catheter 52B passes through a lumen 542B formed inside the injection catheter 52B and flows toward the distal end of the injection catheter 52B. Then, as indicated by arrow A4 in Fig. 27 , the inflation fluid flowing toward the distal end of the injection catheter 52B passes through a hole 541B formed at the distal end of the injection catheter 52B and is supplied to the inside of the balloon 54. As a result, the inflation fluid inflates the balloon 54. That is, the balloon 54 expands. On the other hand, when the inflation fluid is discharged from the balloon 54, the balloon 54 contracts.

[0175] For example, as indicated by arrows A11 and A12 in Fig. 27 , the drainage catheter 51 sucks cerebrospinal fluid present in the subarachnoid space near the lumbar vertebrae into the space 53 through the drainage port 511. Also, as indicated by arrow A10 in Fig. 27 , the drainage catheter 51 sucks cerebrospinal fluid present in the subarachnoid space near the lumbar vertebrae into the space 53 through the multiple holes 512. Then, as indicated by arrow A6 in Fig. 27 , the drainage catheter 51 discharges the cerebrospinal fluid to the outside of the subject's body cavity through the space 53.

[0176] For example, as indicated by arrow A5 in Fig. 27, the liquid supplied from the base end of the injection catheter 52B passes through the lumen 523 of the injection catheter 52B and flows toward the tip end of the injection catheter 52B. Then, as indicated by arrow A13 in Fig. 27, the injection catheter 52B injects the liquid from the injection port 521 into the cerebrospinal fluid present in the subarachnoid space through the lumen 523 of the injection catheter 52B.

[0177] Next, details of the control of a medical system according to a second modification of this embodiment will be described with reference to the drawings. Fig. 28 is a graph showing the relationship between the injection amount, the discharge amount, the balloon volume, and the amount of fluid in the body cavity under the control of a medical system according to a second modification of this embodiment. In the description of the control of this modification, the case where the medical device 5B described above with reference to Fig. 27 is used will be taken as an example.

[0178] The horizontal axis of the graph shown in FIG. 28 represents time. The vertical axis of the graph shown in FIG. 28 represents the change in the volume of fluid. Specifically, the "injection volume" shown in FIG. 28 represents the cumulative volume of fluid 91 injected into the body cavity from the start of control execution. The "discharge volume" shown in FIG. 28 represents the cumulative volume of cerebrospinal fluid discharged outside the body cavity from the start of control execution. The "volume of fluid in the body cavity" shown in FIG. 28 represents the change in the volume of cerebrospinal fluid present in the body cavity at the start of control execution. Furthermore, the vertical axis of the graph shown in FIG. 28 represents the change in the volume of the balloon 54.

[0179] As shown in Figure 28, in the control of this modified example, the control unit 21 sets a second period 212 in which liquid 91 is not injected into the body cavity, liquid 91 is discharged from the body cavity, and the balloon 54 placed in the body cavity is expanded, and a first period 211 in which liquid 91 is injected into the body cavity, liquid 91 is not discharged from the body cavity, and the balloon 54 is deflated.

[0180] As indicated by arrows A10 and A6 in Fig. 27 , during the second period 212, the drainage catheter 51 aspirates cerebrospinal fluid 92 (including liquid 91) present in the subarachnoid space near the lumbar vertebrae through the plurality of holes 512 into the space 53, and discharges it to the outside of the subject's body cavity through the space 53. Also, as indicated by arrows A3 and A4 in Fig. 27 , during the second period 212, the inflation fluid 93 is supplied from the base end of the medical device 5B, passes through the lumen 542B, and is supplied to the inside of the balloon 54 through the hole 541B. This causes the balloon 54 to inflate.

[0181] This allows the control unit 21 to suppress fluctuations in the volume of the body cavity as a closed space during the second period 212 in which cerebrospinal fluid 92 (including liquid 91) is discharged from the body cavity. Therefore, the volume of the body cavity can fluctuate in the high compliance region, and the body cavity can deform in response to the reduced amount of fluid within the body cavity. Therefore, fluctuations in intracranial pressure during the second period 212 are suppressed.

[0182] In the second period 212, the control unit 21 simultaneously discharges the cerebrospinal fluid 92 (including the liquid 91) and inflates the balloon 54. In addition, in the second period 212, the control unit 21 sets the amount of inflation of the balloon 54 (i.e., the amount of inflation fluid 93 injected into the balloon 54) to be substantially the same as the amount of discharged cerebrospinal fluid 92 (including the liquid 91).

[0183] This causes the amount of fluid lost within the body cavity (i.e., the volume) to be substantially the same as the amount by which the balloon 54 expands within the body cavity (i.e., the volume), so the volume of the body cavity does not substantially change during the second period 212. This more reliably suppresses fluctuations in intracranial pressure during the second period 212.

[0184] 27 , during the first period 211, the injection catheter 52B injects the liquid 91 supplied from the proximal end of the injection catheter 52B through the injection port 521 into the cerebrospinal fluid present in the subarachnoid space via the lumen 523. Also during the first period 211, the inflation fluid 93 inside the balloon 54 passes through the hole 541B and the lumen 542B and is discharged to the outside of the balloon 54. This causes the balloon 54 to deflate.

[0185] This allows the controller 21 to suppress fluctuations in the volume of the body cavity as a closed space during the first period 211 in which the liquid 91 is injected into the body cavity. This allows the volume of the body cavity to fluctuate in the high compliance region, enabling the body cavity to deform in response to the increased amount of liquid in the body cavity. This suppresses fluctuations in intracranial pressure during the first period 211.

[0186] During the first period 211, the control unit 21 simultaneously injects the liquid 91 and deflates the balloon 54. Furthermore, during the first period 211, the control unit 21 sets the amount of deflation of the balloon 54 (i.e., the amount of inflation fluid 93 discharged from the balloon 54) to be substantially the same as the amount of injection of the liquid 91.

[0187] This causes the amount of fluid increased within the body cavity (i.e., the volume) to be substantially the same as the amount of fluid deflated within the body cavity (i.e., the volume) of the balloon 54. Therefore, the volume of the body cavity does not substantially change during the first period 211. This more reliably suppresses fluctuations in intracranial pressure during the first period 211.

[0188] 28 , the control unit 21 alternately repeats the second period 212 and the first period 211. In the control of the medical system according to this modification, the injection and discharge of the liquid 91 are not performed simultaneously, and it is possible to suppress the occurrence of a local steady flow of the liquid 91 injected into the body cavity from the injection port 521 of the injection catheter 52B toward the discharge port 511 of the discharge catheter 51.

[0189] 28 , the controller 21 further sets a third period 213, during which the liquid 91 is not injected into the body cavity and the liquid 91 is not discharged from the body cavity, between the second period 212 and the first period 211 and between the first period 211 and the second period 212. That is, during the third period 213, the injection of the liquid 91 into the body cavity and the discharge of the liquid 91 from the body cavity are simultaneously stopped. The controller 21 repeats the second period 212, the third period 213, the first period 211, and the third period 213 in this order. During the third period, as indicated by arrows A24 and A25 in FIG. 10 , for example, diffusion due to differences in the concentrations of oxygen and the like contained in the liquid 91 progresses toward the brain side and the lumbar side according to the duration of the third period 213 (i.e., the stop time). The duration of the third period 213 is preferably until the flow caused by the immediately preceding injection or discharge has disappeared, and specifically, is preferably 1 second or more.

[0190] The control unit 21 executes control to maintain the balloon 54 in an expanded state during a third period 213 between the second period 212 and the first period 211. For example, the control unit 21 maintains a state in which the expansion fluid 93 is supplied to the inside of the balloon 54 during the third period 213 between the second period 212 and the first period 211, thereby maintaining the balloon 54 in an expanded state.

[0191] Meanwhile, the control unit 21 executes control to maintain the balloon 54 in a deflated state during a third period between the first and second periods. For example, the control unit 21 maintains the state in which the inflation fluid 93 is discharged to the outside of the balloon 54 during the third period between the first and second periods, thereby maintaining the balloon 54 in a deflated state.

[0192] As described above, in the liquid circulation system 3B according to the second modification and the medical system according to this modification, the amount of liquid (i.e., volume) that increases or decreases within the body cavity is substantially equal to the amount of the balloon 54 that increases or decreases within the body cavity. Therefore, the volume of the body cavity does not substantially change. This suppresses fluctuations in intracranial pressure. Furthermore, because the volume of the body cavity does not substantially change, the body cavity can change its volume in a high compliance region regardless of the amount of liquid 91 injected, and can deform in response to the increase or decrease in the amount of liquid within the body cavity. Therefore, even if the balance of the amount of liquid is slightly lost, the body cavity can respond by compliance. Furthermore, because the volume of the body cavity does not substantially change regardless of the amount of liquid 91 injected, the amount of liquid 91 injected can be increased as long as there is space for the balloon 54 to expand.

[0193] On the other hand, because the volume of the balloon 54 cannot be negative, it is necessary to adjust the volume so that the cumulative balance between the amount of fluid injected into and discharged from the balloon 54 after the balloon 54 is deflated in the first period 211 does not become negative at any time. Specifically, the amount of fluid injected into and discharged from the balloon is limited so that "(total amount of fluid injected into the balloon in n iterations) - (total amount of fluid discharged from the balloon in n-1 iterations) ≥ n iteration discharge." The amount of fluid discharged per iteration is not particularly limited as long as it does not exceed the volume of the spinal cavity, and is, for example, approximately 1 mL to 30 mL. The amount of fluid injected per iteration is approximately 1 mL to 30 mL, and more preferably approximately 3 mL to 10 mL, taking into account the cross-sectional area of ​​the balloon 54 and the length that can be disposed along the longitudinal direction D1.

[0194] As described above, the control unit 21 further sets a third period 213, during which the liquid 91 is not injected into the body cavity and is not discharged from the body cavity, between the second period 212 and the first period 211 and between the first period 211 and the second period 212. Therefore, the diffusion of oxygen and other substances contained in the liquid 91 progresses more rapidly depending on the length of the third period. This allows the liquid to be delivered to the treatment area of ​​the brain more efficiently.

[0195] The above describes the embodiments of the present invention. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the claims. The configurations of the above embodiments can be partially omitted or arbitrarily combined in a different manner from the above.

[0196] 2: Medical system, 3: Liquid circulation system, 3A: Liquid circulation system, 3B: Liquid circulation system, 5: Medical device, 5B: Medical device, 21: Control unit, 22: Pump, 23: First drive unit, 24: Second drive unit, 26: Fourth drive unit, 31: System circuit unit, 31A: System circuit unit, 31B: System circuit unit, 32: Biocircuit unit, 32A: Biocircuit unit, 32B: Biocircuit unit, 33: Pump unit, 33A: Pump unit, 33B: Pump unit, 41: First tube, 42: Second tube, 43: Third tube, 44: Fourth tube, 45: Fifth tube, 46: Sixth tube, 47: Seventh tube, 48: Eighth tube, 51: Drainage catheter, 52: Infusion catheter, 52B: Infusion catheter, 53: Space, 54: Balloon, 54B: Balloon catheter, 55: Tube, 56: Tank, 91: Liquid, 92: Cerebrospinal fluid, 93: Inflation fluid, 211: First period, 211a: First period, 212: Second period, 212a: Second period, 213: Third period, 311: Reservoir, 312: Oxygenation mechanism, 313: Oxygen supply source, 314: Heat exchanger, 331: First liquid storage section, 332: First pump, 333: First flow path switching section, 334: Second liquid storage section, 335: Second pump, 336: Second flow path switching section, 337: First pump, 338: Second pump, 511: Outlet, 512: Hole, 513: Lumen, 521: Inlet, 523: Lumen, 541B: Hole, 542B: Lumen, 544: Balloon syringe, 545: Balloon piston, 911: Colored water

Claims

1. A medical system for injecting a liquid into a body cavity in which cerebrospinal fluid of a subject is present and discharging the liquid present in the body cavity from the body cavity, comprising: a control unit that sets a first period during which the liquid is injected into the body cavity and is not discharged from the body cavity; and a second period during which the liquid is not injected into the body cavity and is discharged from the body cavity; and that alternates between the first period and the second period and controls the amount of the liquid injected during the first period to be substantially the same as the amount of the liquid discharged during the second period.

2. The medical system according to claim 1, wherein the period from the start of said first period to the end of said second period is substantially constant.

3. The medical system described in claim 1, characterized in that the control unit further sets a third period between the first period and the second period, during which the liquid is not injected into the body cavity and the liquid is not discharged from the body cavity.

4. The medical system according to claim 3, wherein the third period of time is longer than the first period of time.

5. The medical system according to claim 3, wherein the third period is greater than or equal to 1 second.

6. The medical system described in claim 3, characterized in that the control unit further sets the third period between the second period and the first period, and a first time of the third period set between the first period and the second period is longer than a second time of the third period set between the second period and the first period.

7. The medical system of claim 1, wherein the rate at which the liquid is drained during the second period is slower than the rate at which the liquid is infused during the first period.

8. The medical system described in claim 1, characterized in that the control unit initially sets a 0th period in which the liquid is injected or discharged in an amount smaller than the injection amount in the first period and the discharge amount in the second period, and starts a period of the first period and the second period in which the liquid moves in a different direction from the 0th period after the 0th period.

9. The medical system of claim 8, wherein the injection amount during the zero period is substantially half of the injection amount during the first period, and the discharge amount during the zero period is substantially half of the discharge amount during the second period.

10. The medical system described in claim 1, characterized in that the control unit executes control at the end of the control to inject the liquid into the body cavity to approximate the amount of cerebrospinal fluid that was present in the body cavity at the start of execution of the control, or to discharge the liquid from the body cavity to approximate the amount of cerebrospinal fluid that was present in the body cavity at the start of execution of the control.

11. The medical system of claim 1, further comprising an injection catheter for injecting the liquid into the body cavity, and a drainage catheter for draining the liquid from the body cavity, wherein the distance between the tip of the injection catheter and the tip of the drainage catheter is 30 centimeters or less when execution of the control begins.

12. The medical system of claim 1, further comprising control for contracting a balloon that is placed in the body cavity and capable of expanding and contracting during the first period, and for expanding the balloon during the second period.

13. The medical system described in claim 12, characterized in that the control unit simultaneously performs the injection of the liquid and the contraction of the balloon during the first period, and simultaneously performs the discharge of the liquid and the expansion of the balloon during the second period.

14. The medical system described in claim 12, characterized in that the control unit sets the amount of contraction of the balloon during the first period to be substantially equal to the amount of liquid injected, and sets the amount of expansion of the balloon during the second period to be substantially equal to the amount of liquid discharged.

15. The medical system described in claim 12, characterized in that the control unit further sets a third period between the first period and the second period and between the second period and the first period, during which the liquid is not injected into the body cavity and the liquid is not discharged from the body cavity, and maintains the balloon in the contracted state during the third period between the first period and the second period, and maintains the balloon in the expanded state during the third period between the second period and the first period.

16. A liquid circulation system that circulates a liquid by injecting the liquid into a body cavity in which cerebrospinal fluid is present and discharging the liquid outside the body cavity, comprising: an injection catheter that injects the liquid into the body cavity; a discharge catheter that discharges the liquid from within the body cavity to outside the body cavity; a liquid delivery line connected to the injection catheter; a drainage line connected to the drainage catheter; a first liquid delivery unit provided on the liquid delivery line and moving the liquid; a second liquid delivery unit provided on the drainage line and moving the liquid; and a single control unit that controls the first liquid delivery unit and the second liquid delivery unit.

17. The liquid circulation system according to claim 16, further comprising: a liquid storage section for storing at least one of the liquid to be injected into the body cavity and the liquid discharged from the body cavity; and a liquid treatment device provided in the liquid delivery line between the liquid storage section and the first liquid delivery section for treating the liquid.

18. The liquid circulation system according to claim 17, wherein the liquid treatment device is an oxygenation device that adds oxygen to the liquid discharged outside the body cavity.

19. The liquid circulation system according to claim 16, characterized in that the control unit repeatedly drives the first liquid delivery unit and the second liquid delivery unit alternately.

20. The liquid circulation system described in claim 16, characterized in that the control unit controls the sum of the injection amount of the liquid ejected while the first liquid delivery unit is operating continuously or intermittently without starting the second liquid delivery unit, and the discharge amount of the liquid ejected while the second liquid delivery unit is operating continuously or intermittently without starting the first liquid delivery unit, from the time of initial startup within a certain range.

21. The liquid circulation system of claim 16, further comprising a balloon disposed within the body cavity and capable of expanding and contracting, wherein the control unit further controls the expansion and contraction of the balloon.

22. The liquid circulation system described in claim 21, further comprising a balloon driving unit having a balloon fluid storage section for storing an expansion fluid for expanding the balloon, and performing the operations of injecting the expansion fluid in the balloon fluid storage section into the balloon and sending the expansion fluid from inside the balloon into the balloon fluid storage section, wherein the balloon driving unit injects the expansion fluid into the balloon to expand the balloon and discharges the expansion fluid from the balloon to contract the balloon.

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