Concentration measuring system

Abstract

A concentration measuring system (100) comprises a circulation line (110). The inside of the circulation line (110) is divided into a measurement flow path (122) and a general flow path (124) by a partition wall (120). A filter (130) is provided in an upstream communication port (115), which is one of the communication ports between the circulation line (110) and the measurement flow path (122). A sensor unit (60) of an enzyme sensor (50) is disposed in the measurement flow path (122). A sample that has passed through the filter (130) flows into the measurement flow path (122). The sensor unit (60) measures the concentration of a substance (40) to be measured in this sample.

Description

Concentration measurement system

[0001] The present disclosure relates to a concentration measurement system including an enzyme sensor.

[0002] In a medical institution, when it is necessary to temporarily substitute a patient's cardiopulmonary function during, for example, cardiac surgery, extracorporeal circulation is performed in which the patient's blood is circulated extracorporeally using an extracorporeal circulation system including a heart-lung machine or the like. An extracorporeal circulation system is disclosed, for example, in Japanese Patent Application Laid-Open No. 2007-14504. During extracorporeal circulation, a medical worker controls the extracorporeal circulation device to achieve optimal extracorporeal circulation conditions while measuring various parameters such as the partial pressure of oxygen in the patient's blood and the concentration of substances (e.g., glucose, lactate, etc.) in the blood. Enzyme sensors are used for concentration measurement. Japanese Patent Application Laid-Open No. 2024-160291 discloses a device including an enzyme sensor.

[0003] As can be understood from the description of Japanese Patent Application Laid-Open No. 2024-160291, in the conventional technique for performing concentration measurement with an enzyme sensor, a part of blood is collected as a sample from a patient, and the concentration of the target substance to be measured in this sample is measured. That is, it is a so-called batch measurement.

[0004] Japanese Patent Application Laid-Open No. 2007-14504 Japanese Patent Application Laid-Open No. 2024-160291

[0005] In batch measurement, while concentration measurement is being performed as described above, changes in the concentration of the target substance in the blood inside the patient's body cannot be grasped. Therefore, attempts have been made to measure the concentration of the target substance in a flowing sample.

[0006] Particularly, in an extracorporeal circulation system, there is a demand for continuous long-term monitoring of a patient's condition depending on the treatment period, and a sensor capable of continuous measurement over a long period of time is often required. There is also a demand for maintaining high measurement accuracy. However, when a conventional sensor is used, the sensitivity or sensor output decreases as time passes from the start of measurement. For this reason, it is not easy to continuously measure the concentration of a target substance over a long period of time.

[0007] This disclosure aims to solve the problems described above.

[0008] (1) An aspect of the present disclosure is a concentration measuring system comprising: a flow line through which a fluid sample flows; and an enzyme sensor containing an enzyme, wherein the enzyme reacts with a target substance contained in the sample to measure the concentration of the target substance in the sample, wherein the flow line comprises, in a portion of the flow line, a partition wall extending along the flow direction of the sample; a measurement channel and a general channel formed by the partition wall separating the interior of the flow line; an upstream communication port which is an inlet through which the target substance flows from the interior of the flow line into the measurement channel; a downstream communication port which is an outlet through which the target substance flows from the measurement channel into the interior of the flow line; and a filter provided at least at the upstream communication port, through which the target substance can selectively pass, wherein the enzyme sensor comprises a sensor unit for measuring the concentration of the target substance, and the sensor unit is located in the measurement channel.

[0009] With this configuration, since the sensor is placed in the measurement channel, the amount of the substance being measured that is exposed to the enzyme is less compared to when the sensor is placed in the general channel. Therefore, enzyme consumption is reduced, which in turn extends the lifespan of the enzyme sensor.

[0010] Furthermore, since a filter is installed at the upstream communication port, the inflow of substances other than the target substance (impurities) from the flow line into the measurement channel is suppressed. As a result, noise generated by impurities is reduced. In addition, since contact of impurities with the sensor is avoided, the enzyme sensor's lifespan is also extended.

[0011] (2) In the concentration measurement system described in item (1) above, the flow line may have two filters, and the two filters may be provided at the upstream communication port and the downstream communication port, respectively.

[0012] In the distribution line, it is anticipated that samples surrounding the downstream communication port may flow back into the measurement channel from the downstream communication port against the flow of the sample. Even if such a situation occurs, the filter installed at the downstream communication port will prevent contaminants from flowing into the measurement channel.

[0013] (3) In the concentration measurement system described in item (1) or (2) above, the enzyme sensor may have an enzyme layer containing the enzyme and a diffusion control layer located upstream of the enzyme layer in the diffusion direction of the substance to be measured, which controls the diffusion rate of the substance to be measured.

[0014] The diffusion control layer limits the amount of the target substance that reaches the enzyme layer. This suppresses the reaction between the enzyme in the enzyme layer and the target substance, thereby reducing enzyme depletion. In other words, it allows for a longer lifespan for the enzyme sensor.

[0015] (4) In the concentration measurement system described in any one of the above items (1) to (3), the flow line may be a tube through which the blood flows in an extracorporeal circulation system provided outside the body of a living organism that circulates the blood of the living organism outside the body.

[0016] With this configuration, the concentration of the target substance in the blood can be continuously monitored.

[0017] According to this disclosure, the concentration of a target substance in a flowing sample can be measured in real time.

[0018] Figure 1 is a schematic diagram of an extracorporeal circulation system incorporating the concentration measurement system according to the present disclosure. Figure 2 is a schematic diagram of the concentration measurement system. Figure 3 is a schematic diagram of the sensor part constituting the enzyme sensor. Figure 4 is a schematic diagram of the working electrode constituting the sensor part. Figure 5 is a graph showing the relationship between elapsed time and sensor output.

[0019] The following describes an embodiment in which blood BL, as shown in Figure 2, is used as the fluid sample. However, the fluid sample is not limited to blood BL.

[0020] Furthermore, in Figures 1 to 4, the components may be exaggerated. However, this is for convenience to facilitate understanding, and the scale shown in the drawings does not necessarily correspond to the actual size.

[0021] Figure 1 is a schematic diagram of the extracorporeal circulation system 10 incorporating the concentration measurement system 100 according to this embodiment. First, the extracorporeal circulation system 10 will be described.

[0022] The extracorporeal circulation system 10 is used to circulate the blood BL (see Figure 2) of a living human body (HM) outside the body. As shown in Figure 1, the extracorporeal circulation system 10 comprises a pump drive unit 12, a blood pump 14, a system control unit 16, and an artificial lung 18.

[0023] The pump drive unit 12 is a drive unit for rotating the blood pump 14. The pump drive unit 12 has a motor 13. The motor 13 generates rotational driving force to rotate the blood pump 14. The pump drive unit 12 is controlled by the system control unit 16.

[0024] The blood pump 14 is a pump for circulating blood BL in the extracorporeal circulation system 10. The blood pump 14 has a blood inlet port 141 and a blood outlet port 142.

[0025] A blood withdrawal catheter 22 is connected to the blood inlet port 141 of the blood pump 14. The blood withdrawal catheter 22 is a catheter for extracting blood BL from the human body (HM). Blood BL is introduced from the human body (HM) to the blood pump 14 via the blood withdrawal catheter 22. The upstream end of a relay tube 21 is connected to the blood outlet port 142 of the blood pump 14. The downstream end of the relay tube 21 is connected to the blood inlet port 30a of the artificial lung 18. Blood BL that flows out from the blood outlet port 142 of the blood pump 14 is introduced to the artificial lung 18 via the relay tube 21.

[0026] The artificial lung 18 performs a gas exchange operation with blood BL. The artificial lung 18 has a housing 26 and a gas exchange unit 28. The housing 26 has a blood inlet port 30a and a blood outlet port 30b. The downstream end of the relay tube 21 is connected to the blood inlet port 30a. A blood delivery catheter 24 is connected to the blood outlet port 30b. The blood delivery catheter 24 is a catheter for returning the blood BL after gas exchange to the human body HM.

[0027] The gas exchange unit 28 is located inside the housing 26. A gas supply line (not shown) is connected to the gas exchange unit 28. In the gas exchange unit 28, oxygen gas from the oxygen-containing gas sent to the gas exchange unit 28 via the gas supply line is exchanged with carbon dioxide gas from the blood BL. That is, the blood BL extracted from the human body HM into the artificial lung 18 is returned to the human body HM from the artificial lung 18 after the carbon dioxide gas in the blood BL has been replaced with oxygen gas in the artificial lung 18.

[0028] The blood withdrawal catheter 22 is provided with a flow line 110 that constitutes the concentration measurement system 100. The flow line 110 acts as a bypass line in the blood withdrawal catheter 22. Therefore, the flow line 110 consists of a tube 111 through which blood BL flows.

[0029] Thus, the flow line 110 of the concentration measurement system 100 is connected as a bypass line to the blood withdrawal side (for example, the blood withdrawal catheter 22). The flow line 110 may also be connected as a bypass line to the blood delivery side (for example, the blood delivery catheter 24).

[0030] Next, the concentration measurement system 100 will be described. The concentration measurement system 100 comprises a distribution line 110 and an enzyme sensor 50.

[0031] As shown in Figure 2, the flow line 110 has a tube unit 118. The tube unit 118 has a short tube 119 and a partition wall 120 provided inside the short tube 119. The short tube 119 and the partition wall 120 are integrated. The partition wall 120 is, for example, substantially flat in shape and extends along the flow direction of the blood BL sample. Since the short tube 119 is part of the flow line 110, the partition wall 120 extends along the flow direction of the blood BL in a portion of the flow line 110.

[0032] In the partition wall 120, the length in the width direction perpendicular to the flow direction is approximately equal to the inner diameter of the flow line 110 (tube 111). Therefore, the inside of the flow line 110 is divided into two flow paths by the partition wall 120. One of the two flow paths is the measurement flow path 122, and the other is the general flow path 124. The measurement flow path 122 and the general flow path 124 extend parallel to each other along the flow direction of blood BL. The measurement flow path 122, which is composed of the short tube 119 and the partition wall 120, may be directly provided on the blood withdrawal catheter 22. In this case, the flow line 110, which functions as a bypass line, is integrated with the blood withdrawal catheter 22.

[0033] In the distribution line 110, the area upstream of the measurement channel 122 and the general channel 124 is referred to as the upstream channel 114. The upstream channel 114 and the measurement channel 122 are connected via an upstream communication port 115. The upstream communication port 115 is the inlet through which the substance to be measured 40 flows from the upstream channel 114 (inside the distribution line 110) into the measurement channel 122.

[0034] In the distribution line 110, the area downstream of the measurement channel 122 and the general channel 124 is referred to as the downstream channel 116. The measurement channel 122 and the downstream channel 116 are connected via a downstream communication port 117. The downstream communication port 117 is the outlet through which the substance to be measured 40 flows from the measurement channel 122 into the downstream channel 116 (inside the distribution line 110).

[0035] In the illustrated example, the diameter of the tube unit 118 is the same as the diameters of the upstream channel 114 and the downstream channel 116. However, for example, the diameter of the tube unit 118 may be different from the diameters of the upstream channel 114 and the downstream channel 116.

[0036] In this embodiment, the concentration measurement system 100 has two filters 130. Hereinafter, the two filters 130 will be referred to as the upstream filter 131 and the downstream filter 132, respectively. The upstream filter 131 is provided at the upstream communication port 115, and the downstream filter 132 is provided at the downstream communication port 117. The upstream filter 131 and the downstream filter 132 selectively allow the substance to be measured 40 to pass through. Therefore, the amount of substance to be measured 40 flowing into the measurement channel 122 is limited. As a result, the amount of substance to be measured 40 flowing into the measurement channel 122 is reduced compared to when the filters 130 are not provided. The filters 130 are configured not to allow the passage of blood cell components such as red blood cells and other substances.

[0037] The degree of selectivity in the upstream filter 131 and the downstream filter 132 is expressed, for example, based on the degree of mesh opening. That is, the mesh opening of filter 130 is set to such an extent that the substance to be measured 40 can easily pass through, while preventing the passage of impurities 41 such as proteins. The mesh opening of filter 130 can be set to such an extent that, for example, half (50%) of the substance to be measured 40 can pass through. However, the mesh opening of filter 130 is not limited to such an extent that 50% of the substance to be measured 40 can pass through.

[0038] The two filters 130 are, for example, membranes. When the substance to be measured 40 is lactate, suitable materials for the filters 130 include hydrophilic polytetrafluoroethylene (H-PTFE) or cellulose. However, these are just examples of combinations, and the material of the filters 130 is selected according to the substance to be measured 40.

[0039] Note that the downstream filter 132 is not essential. In other words, a single filter 130 may be provided only at the upstream communication port 115.

[0040] In contrast, no filters or the like are provided at the connection point between the upstream channel 114 and the general channel 124. Similarly, no filters or the like are provided at the connection point between the general channel 124 and the downstream channel 116. Therefore, the blood BL that has flowed through the upstream channel 114 flows directly through the general channel 124. In addition, the blood BL that has flowed through the general channel 124 and the blood that has flowed through the measurement channel 122 and had some substances filtered out flow through it, are mixed together and flow through the downstream channel 116.

[0041] The enzyme sensor 50 is a sensor for measuring the concentration of the target substance 40 contained in a sample. The target substance 40 is a substance that reacts with the enzyme 821 shown in Figure 4, and is also called a substrate. In this embodiment, the sample is blood BL, which is a biological component. In this case, lactate can be given as an example of the target substance 40. However, the sample is not limited to blood BL, and the target substance 40 is not limited to lactate.

[0042] Figure 3 is a schematic diagram of the sensor unit 60 that constitutes the enzyme sensor 50. The sensor unit 60 is housed in a casing (not shown), for example. The sensor unit 60 has an working electrode 62, a counter electrode 64, and a reference electrode 66. The working electrode 62, the counter electrode 64, and the reference electrode 66 are formed on an insulating substrate 68. A first leader wire 70 is connected to the working electrode 62. Similarly, a second leader wire 72 is connected to the counter electrode 64, and a third leader wire 74 is connected to the reference electrode 66. Each of the first to third leader wires 70 to 74 is covered with an insulating layer (not shown). Each of the first to third leader wires 70 to 74 is connected to the sensor control unit 17 via a signal line 76 shown in Figure 1.

[0043] Here, the sensor control unit 17 has a processing unit 171. The processing unit 171 is composed of a processor 172, such as a CPU (Central Processing Unit), that is, a processing circuitry. The processing unit 171 can be realized by the processor 172 executing a program stored in the memory unit 173. The sensor control unit 17 is connected to the system control unit 16 via a signal line 78.

[0044] As shown in FIG. 4, the working electrode 62 includes an electrode base material 80, an enzyme layer 82, and a diffusion control layer 84. The material of the electrode base material 80 is, for example, carbon.

[0045] The enzyme layer 82 is a film supported by the electrode base material 80. In the illustrated example, the enzyme layer 82 includes an enzyme 821, an unillustrated electron transfer mediator, and unillustrated carbon nanotubes. However, the electron transfer mediator and the carbon nanotubes are not essential.

[0046] As the enzyme 821, an enzyme that reacts specifically with the analyte 40 is used. When the analyte 40 is lactate, specific examples of the enzyme 821 include lactate dehydrogenase and the like. However, these are examples of combinations; the analyte 40 is not limited to lactate as described above, and the enzyme 821 is not limited to lactate dehydrogenase.

[0047] The electron transfer mediator is a medium that transfers electrons generated when the analyte 40 reacts with the enzyme 821 to the carbon nanotubes. The electron transfer mediator is constituted, for example, by binding an electron transfer substance to a terminal end of branched polyethylene glycol. Specific examples of the electron transfer substance include phenazine derivatives and the like.

[0048] The carbon nanotubes function as a conductive material for transferring electrons received from the electron transfer mediator to the electrode base material 80. As described above, electrons generated based on the aforementioned reaction can move to the electrode base material 80 via the electron transfer mediator and the carbon nanotubes.

[0049] The working electrode 62 may further include a protective layer 83. The protective layer 83 is interposed between the enzyme layer 82 and the diffusion control layer 84, and protects the enzyme 821 contained in the enzyme layer 82 from the analyte 40.

[0050] The diffusion control layer 84 controls the diffusion rate of the substance to be measured 40 into the enzyme layer 82. In other words, the diffusion control layer 84 delays the arrival of the substance to be measured 40 into the enzyme layer 82. Specific examples of materials for the diffusion control layer 84 include urethane resin. However, the material of the diffusion control layer 84 is not limited to urethane resin.

[0051] At the working electrode 62, the substance to be measured 40 first passes through the diffusion control layer 84, then through the protective layer 83, and finally reaches the enzyme layer 82. Therefore, in the diffusion direction (flow direction) of the substance to be measured 40 at the working electrode 62, the diffusion control layer 84 is located upstream, the protective layer 83 is located midstream, and the enzyme layer 82 is located downstream.

[0052] The counter electrode 64 shown in Figure 3 is made of, for example, carbon. The reference electrode 66 has a well-known configuration such as silver / silver chloride.

[0053] Next, a method for measuring the concentration of the target substance 40 in a sample (blood BL) using the concentration measurement system 100 described above will be explained.

[0054] When the extracorporeal circulation system 10 shown in Figure 1 is activated, an oxygen-containing gas with adjusted oxygen concentration is supplied to the artificial lung 18. Meanwhile, the blood BL of the human HM circulates through the extracorporeal circulation system 10. That is, the blood BL of the human HM is drawn out to the blood pump 14 via the blood withdrawal catheter 22 and flows into the artificial lung 18 via the relay tube 21. In the artificial lung 18, the oxygen gas contained in the mixed gas is exchanged with the carbon dioxide gas in the blood BL. After that, the blood BL is returned to the human HM's body from the artificial lung 18 via the blood delivery catheter 24.

[0055] A portion of the blood BL drawn into the blood withdrawal catheter 22 by the blood pump 14 flows into the flow line 110 connected to the blood withdrawal catheter 22. The blood BL flowing through the upstream channel 114 (see Figure 2) of the flow line 110 is divided by the partition wall 120 into a first branch F1 that goes towards the measurement channel 122 and a second branch F2 that goes towards the general channel 124. The second branch F2 flows to the downstream channel 116 via the general channel 124.

[0056] Meanwhile, the first tributary F1 reaches the upstream communication port 115. As described above, an upstream filter 131 is located at the upstream communication port 115. The upstream filter 131 restricts the passage of impurities 41 such as proteins among the various components contained in the first tributary F1, while allowing the passage of a predetermined proportion of the target substance 40 and plasma PZ. As a result, the target substance 40 and plasma PZ selectively flow into the measurement channel 122. Consequently, contact of impurities 41 with the sensor unit 60 is suppressed. In addition, the amount of target substance 40 flowing into the sensor unit 60 is limited. As a result, the lifespan of the enzyme sensor 50 is extended. Furthermore, noise generated in the sensor output due to impurities 41 is reduced.

[0057] The upstream filter 131 partially restricts the passage of the target substance 40. That is, a portion of the target substance 40 contained in the blood BL flows into the measurement channel 122. Here, the sensor unit 60 is calibrated before the circulation of blood BL begins in the extracorporeal circulation system 10. Calibration is the process of passing a calibration solution with a known concentration of the target substance 40 through the enzyme sensor 50 and registering the sensor output at that time with the sensor control unit 17 to be treated as the known concentration. The memory unit 173 of the sensor control unit 17 stores a calibration curve created based on that calibration as reference information. Therefore, even if the amount of target substance 40 is limited, a correct correlation can be obtained between the actual concentration of the target substance 40 contained in the blood BL and the concentration of the target substance 40 in the plasma PZ that flows into the measurement channel 122.

[0058] The plasma PZ and the target substance 40 flowing into the measurement channel 122 come into contact with the sensor part 60 of the enzyme sensor 50 (see Figures 2 and 3). This initiates the measurement of the concentration of the target substance 40 in the plasma PZ flowing into the measurement channel 122. The flow rate of blood BL in the flow line 110 is sufficiently lower than the flow rate of blood BL in the blood withdrawal catheter 22 (see Figure 1). Therefore, noise is less likely to occur in the sensor part 60. Consequently, relatively accurate measurements of the concentration of the target substance 40 can be obtained.

[0059] The substance to be measured 40 that comes into contact with the sensor unit 60 then reaches the enzyme layer 82 via the diffusion control layer 84 and protective layer 83 shown in Figure 4. The diffusion control layer 84 delays the arrival of the substance to be measured 40 to the enzyme layer 82, thereby limiting the amount of the substance to be measured 40 that reaches the enzyme layer 82. This prevents the enzyme layer 82 from being consumed in a short time.

[0060] Based on the reaction between the enzyme 821 and the substance to be measured 40 in the enzyme layer 82, electrons are generated. Based on the electrons reaching the electrode substrate 80 via the electron transfer mediator and carbon nanotubes, an electric current is generated between the working electrode 62 and the counter electrode 64 as shown in Figure 3. Information regarding this current is sent as an information signal to the processing unit 171 of the sensor control unit 17 via the first to third leader lines 70 to 74 and the signal line 76 (see Figure 1).

[0061] The processing unit 171 compares this information signal (potential difference) with calibration curve information pre-stored in the memory unit 173 of the sensor control unit 17. That is, the processing unit 171 determines the concentration of the target substance 40 (see Figure 2) in the blood BL based on the concentration of the target substance 40 in the plasma PZ that has flowed into the measurement channel 122. The concentration is displayed, for example, on a monitor (not shown). By visually checking this display, the practitioner can determine whether the concentration of the target substance 40 in the blood BL of the human HM is within the standard range.

[0062] As described above, the blood BL that has flowed through the upstream channel 114 flows directly into the general channel 124. Therefore, when the sensor part 60 of the enzyme sensor 50 is placed in the general channel 124, the amount of the substance to be measured 40 exposed to the enzyme 821 (see Figure 4) is large. Consequently, the rate of consumption of the enzyme 821 is large. Therefore, as shown by the dashed line in Figure 5, even if the input value of the information signal regarding the concentration is constant, the sensor output decreases in a relatively short time. In other words, the sensitivity decreases.

[0063] In contrast, some of the target substance 40 in the blood BL flows into the measurement channel 122 (see Figure 2). Under these conditions, the exposure of the enzyme 821 (see Figure 4) to the target substance 40 is less compared to when the sensor part 60 of the enzyme sensor 50 is placed in the general channel 124. Therefore, the rate of consumption of the enzyme 821 is small. As a result, the sensor output is maintained for a long period of time, as shown by the solid line in Figure 5. That is, the sensitivity is maintained. In this way, by providing the measurement channel 122 inside the flow line 110 and limiting the amount of target substance 40 flowing into the measurement channel 122, the lifespan of the enzyme sensor 50 can be extended.

[0064] For the reasons stated above, the concentration of the substance 40 to be measured can be accurately measured over a long period of time. In other words, the practitioner can continuously monitor the accurate concentration of the substance 40 to be measured throughout the procedure.

[0065] A portion of the plasma PZ and the substance to be measured 40 that has flowed through the measurement channel 122 passes through the downstream filter 132 located at the downstream communication port 117 and flows into the downstream channel 116. In this situation, it is assumed that blood BL may flow back from the downstream channel 116 towards the measurement channel 122. If such a situation occurs, the downstream filter 132 prevents impurities 41 from flowing into the measurement channel 122 via the downstream communication port 117. Therefore, even if such a situation occurs, it is possible to suppress contact of impurities 41 with the sensor unit 60.

[0066] The effects of this embodiment can be summarized as follows:

[0067] As shown in Figure 2, the flow line 110 constituting the concentration measurement system 100 has a partition wall 120. The inside of the flow line 110 is divided by the partition wall 120 into a measurement flow path 122 and a general flow path 124. The upstream flow path 114, which is part of the inside of the flow line 110, communicates with the measurement flow path 122 via an upstream communication port 115. The measurement flow path 122 communicates with the downstream flow path 116, which is another part of the inside of the flow line 110, via a downstream communication port 117. At least the upstream communication port 115 is provided with a filter 130. The sensor part 60 of the enzyme sensor 50 is provided in the measurement flow path 122.

[0068] This allows the concentration of the target substance 40 in blood BL to be measured in real time while the blood BL is circulating. Therefore, if the concentration of the target substance 40 changes, the practitioner can quickly grasp that change.

[0069] Furthermore, since a filter 130 is provided at the upstream communication port 115, the entry of substances other than the target substance 40 (impurities 41) from the upstream flow path 114 into the measurement flow path 122 is suppressed. Consequently, noise generated by the impurities 41 is reduced. In addition, contact between the impurities 41 and the sensor unit 60 is avoided. As a result, the lifespan of the enzyme sensor 50 can be extended.

[0070] Furthermore, since the sensor unit 60 is positioned in the measurement channel 122, where the inflow of the substance to be measured 40 is restricted, the exposure or reaction amount of the substance to be measured 40 to the enzyme 821 (see Figure 4) is lower compared to when the sensor unit 60 is positioned in the general channel 124. As a result, the consumption of the enzyme 821 is suppressed. This makes it possible to extend the lifespan of the enzyme sensor 50.

[0071] As shown in Figure 2, the flow line 110 has two filters 130. The two filters 130 are provided at the upstream communication port 115 and the downstream communication port 117, respectively.

[0072] Even if blood BL in the downstream channel 116 flows back into the measurement channel 122 from the downstream communication port 117, the filter 130 provided in the downstream communication port 117 prevents impurities 41 from flowing into the measurement channel 122.

[0073] As shown in Figure 4, the enzyme sensor 50 has an enzyme layer 82 and a diffusion control layer 84. The diffusion control layer 84 controls the diffusion rate of the substance to be measured 40 upstream of the enzyme layer 82 in the diffusion direction of the substance to be measured 40.

[0074] The diffusion control layer 84 limits the amount of the substance to be measured 40 that reaches the enzyme layer 82. As a result, the reaction between the enzyme 821 contained in the enzyme layer 82 and the substance to be measured 40 is suppressed, and the consumption of the enzyme 821 is reduced.

[0075] The distribution line 110 is a tube 111 through which blood BL from human body HM flows in an extracorporeal circulation system 10 that circulates blood BL from human body HM outside the body.

[0076] This configuration allows for continuous monitoring of the concentration of the target substance 40 in blood BL.

[0077] While this disclosure has been described in detail, it is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of this disclosure or from the intent of this disclosure derived from the claims and their equivalents. These embodiments can also be implemented in combination. For example, the order of operations and processes in the embodiments described above are given as examples only and are not limited thereto. The same applies when numerical values ​​or mathematical formulas are used in the description of the embodiments described above.

Claims

1. A concentration measuring system comprising: a flow line through which a fluid sample flows; an enzyme sensor containing an enzyme, wherein the enzyme reacts with a target substance contained in the sample to measure the concentration of the target substance in the sample, wherein the flow line has a partition wall extending along the flow direction of the sample in a portion of the flow line; a measurement channel and a general channel formed by the partition wall separating the interior of the flow line; an upstream communication port which is an inlet through which the target substance flows from the interior of the flow line into the measurement channel; a downstream communication port which is an outlet through which the target substance flows from the measurement channel back into the interior of the flow line; and a filter provided at least at the upstream communication port, through which the target substance can selectively pass, wherein the enzyme sensor has a sensor unit for measuring the concentration of the target substance, and the sensor unit is located in the measurement channel.

2. A concentration measuring system according to claim 1, wherein the flow line has two filters, and the two filters are provided at the upstream port and the downstream port, respectively.

3. A concentration measurement system according to claim 1, wherein the enzyme sensor comprises an enzyme layer containing the enzyme and a diffusion control layer located upstream of the enzyme layer in the diffusion direction of the substance to be measured and controlling the diffusion rate of the substance to be measured.

4. A concentration measuring system according to any one of claims 1 to 3, wherein the flow line is a tube through which blood flows in an extracorporeal circulation system provided outside the body of a living organism to circulate the blood of the living organism outside the body.

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