In-line fluid measurement systems

Abstract

To provide a fluid sensor system, and a method of operating the fluid sensor system.SOLUTION: A fluid sensor device of the fluid sensor system can be connected with a treatment system in-line. The fluid sensor system may receive a second solution different from a first calibration fluid to use as a calibration fluid to reduce costs associated with storing a calibration fluid inside the fluid sensor device prior to the use with the treatment system.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This application relates to an in-line fluid sensor system. More specifically, the in-line fluid sensor system can use an external calibration fluid source. [Background technology]

[0002] In-line fluid sensor systems can be used during many treatment procedures to measure and / or monitor the properties of a sample fluid, e.g., a patient's blood. Calibration fluids are often used in such fluid sensor systems to calibrate the system's sensors before and / or after each measurement of the sample fluid to ensure long-term use of the sensors with sufficient accuracy. The operational lifetime of a fluid sensor system is often determined by the amount of calibration fluid available and the number of calibration sequences that can be performed. Storing and maintaining large amounts of calibration fluid can be costly due to a larger footprint and more expensive storage solutions. Summary of the Invention [Means for solving the problem]

[0003] The present disclosure relates generally to in-line fluid sensor systems.

[0004] One aspect relates to a method for calibrating a fluid sensor device connected in-line with a treatment system, the method including providing a first calibration fluid stored in a calibration compartment to a sensing element, obtaining a first measurement of the first calibration fluid with the sensing element, providing a second calibration fluid from a second calibration fluid source, obtaining a second measurement of the second calibration fluid with the sensing element, and calibrating the sensing element using the second calibration fluid.

[0005] A variation of the above embodiment further includes connecting the inlet of the fluid sensor device to a first point in the treatment line of the treatment system and the outlet of the fluid sensor device to a second point in the treatment line of the treatment system.

[0006] A variation of the above embodiment further includes storing a second calibration fluid in the second calibration compartment.

[0007] In one variation of the above embodiment, the second calibration compartment is empty before being connected to the treatment system.

[0008] A variation of the above embodiment further includes determining a difference between the first measurement of the first calibration fluid and the second measurement of the second calibration fluid.

[0009] In one variation of the above aspect, calibrating the sensing element includes comparing the second calibration measurement to a difference between the first measurement of the first calibration fluid and the second measurement of the second calibration fluid.

[0010] In one variation of the above embodiment, a treatment line connects the patient and a second source of calibration fluid.

[0011] In one variation of the above embodiment, the second source of calibration fluid is external to the fluid sensor device.

[0012] In one variation of the above embodiment, the second calibration fluid comprises a physiological solution.

[0013] A variation of the above aspect further includes providing sample fluid from the patient to the sensing element via a treatment line.

[0014] A variation of the above embodiment further includes controlling a direction of fluid flow in the treatment line to provide a second calibration fluid from the treatment solution source to the sensing element after providing sample fluid from the patient through the treatment line to the sensing element.

[0015] Another aspect of the present disclosure relates to a fluid sensor system configured to measure a sample fluid in-line with a treatment system. The fluid sensor system includes a fluid sensor device. The fluid sensor device includes a sensing channel configured to receive the sample fluid from the treatment system, a first calibration compartment containing a first calibration fluid and in fluid communication with the sensing channel, a second calibration compartment configured to receive a second calibration fluid from a second calibration fluid source, and a sensing element configured to interact with and transduce a property of the fluid in the sensing channel. The second calibration compartment is in fluid communication with the sensing channel.

[0016] In one variation of the above embodiment, the first calibration compartment has a volume in the range of 5 to 100 microliters.

[0017] In one variation of the above embodiment, the second source of calibration fluid is external to the fluid sensor system.

[0018] In one variation of the above embodiment, the second source of calibration fluid comprises a treatment line of the treatment system.

[0019] In one variation of the above embodiment, the second calibration fluid is a physiological fluid.

[0020] A variation of the above aspect further includes a processor configured to determine a difference between a first measurement value obtained by the sensing element of the first calibration fluid and a second measurement value obtained by the sensing element of the second calibration fluid, and to calibrate the sensing element based at least on the measurement value obtained by the sensing element of the second calibration fluid and the determined difference.

[0021] In one variation of the above embodiment, the second calibration compartment is empty during the storage mode, and the fluid sensor system is not connected to the treatment system during the storage mode.

[0022] Another aspect of the present disclosure relates to a fluid sensor system configured to measure a sample fluid in-line with a treatment system. The fluid sensor system includes a fluid sensor device. The fluid sensor device includes a sensing channel configured to receive the sample fluid from the treatment system, a calibration compartment containing a first calibration fluid and in fluid communication with the sensing channel, and a sensing element configured to interact with the fluid in the sensing channel. The calibration compartment has a volume in the range of 5 to 100 microliters.

[0023] A variation of the above embodiment further includes a controller configured to control one or more valves to selectively direct only the second calibration fluid from the treatment system to the detection channel in the calibration mode, and to control one or more valves to selectively direct only the sample fluid from the treatment system to the detection channel in the detection mode.

[0024] A variation of the above aspect further includes a processor configured to determine a difference between a first measurement value obtained by the sensing element of the first calibration fluid and a second measurement value obtained by the sensing element of the second calibration fluid, and in a calibration mode, calibrate the sensing element based at least on the measurement value obtained by the sensing element of the second calibration fluid and the determined difference.

[0025] The present disclosure will be described with reference to the accompanying drawings, in which like reference characters refer to like elements. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is a schematic system diagram of a fluid sensor system. [Figure 2] FIG. 1 is a schematic system diagram of a fluid sensor system according to one embodiment of the present disclosure. [Figure 3A] FIG. 10 is a schematic system diagram of a fluid sensor system according to another embodiment of the present disclosure. [Figure 3B] FIG. 3B is a schematic system diagram of the fluid sensor system of FIG. 3A during a calibration mode. [Figure 3C] FIG. 3B is a schematic system diagram of the fluid sensor system of FIG. 3A in a sample fluid sensing mode. [Figure 4] 1 is a flowchart illustrating an exemplary method of operating a fluid sensor system according to the present disclosure. [Figure 5] FIG. 3B is a block diagram illustrating electrical components in the fluid sensor system of FIG. 2 or FIG. 3A. DETAILED DESCRIPTION OF THE INVENTION

[0027] As generally described, one or more aspects of the present disclosure relate to an in-line fluid sensor system. The in-line fluid sensor system can be connected to, for example, a treatment line of a treatment system and function without interrupting treatment. In certain embodiments, the present disclosure relates to systems and methods for measuring sample fluids using multiple sources of calibration fluid. In some embodiments, the fluid sensor system can include an empty fluid compartment configured to receive and store physiological fluid from the treatment line for use as a calibration fluid when the fluid sensor system is connected to the treatment system. In some embodiments, the fluid sensor system can be configured to receive and use physiological solution as a calibration fluid directly from the treatment line when the fluid sensor system is connected to the treatment system, without storing the physiological solution in a dedicated calibration fluid compartment of the fluid sensor system. In other embodiments, the fluid sensor system can store the solution in a second calibration fluid compartment in addition to the first calibration fluid compartment that stores the calibration fluid.

[0028] 1 , a fluid sensor system 1000 can include a fluid sensor device 100 with a sensing element 130 that includes a plurality of functionalized transducers or electrodes that, when exposed to a sample fluid, can measure a property or component of the sample fluid (e.g., a patient's blood) and transmit a signal indicative of the property or component of the sample fluid (e.g., the concentration of a particular component in the sample fluid). During a treatment procedure, the fluid sensor device 100 can be connected in-line to a treatment line 150 of a treatment system and configured to operate in multiple modes. For example, during a sensing mode, the sample fluid 150 can enter the fluid sensor device 100 via an inlet 152 and exit the fluid sensor device 100 via an outlet 154. After the sample fluid 150 enters the fluid sensor device 100, the treatment line 150 can be directed to a sensing channel 132 to interact with the sensing element 130 and enable the sensing element 130 to perform a measurement.

[0029] During calibration mode, the sample fluid 150 may be directed to pass directly from the inlet 152 to the outlet 154, bypassing the electrodes of the sensing element 130 without entering the sensing channel 132. Alternatively, a specific volume of a calibration fluid (e.g., a biocompatible fluid such as water, saline, or the like) may be provided to the sensing element 130 from the calibration compartment 110 of the fluid sensor device 100. The calibration fluid may serve to reset the fluid sensor device 100 by presenting a known characteristic (e.g., a voltage representing a specific concentration of a component) that the sensing element 130 can measure and calibrate. For example, in some embodiments, the calibration fluid may have a known potassium level, and the sensing element 130 may measure a voltage of the calibration fluid that represents the concentration of potassium in the calibration fluid. In some embodiments, the sensing element 130 may be calibrated based on an offset between the measured voltage of the calibration fluid and a stored voltage value stored in memory. Additionally, the calibration fluid can improve the accuracy of the sensing element 130 by flushing the sensing channel 132 to remove residual sample fluid and / or other debris. In some embodiments, at the end of the calibration mode, the calibration fluid can exit the sensing channel 132 and enter and be stored in the waste compartment 120. Further details regarding how the fluid sensor device 100 may operate (e.g., take measurements, store information, and transmit signals) can be found in U.S. Patent Application No. 18 / 055,799 (published as U.S. Patent Application Publication No. 2023 / 0149608), the entire disclosure of which is incorporated by reference as if fully set forth herein.

[0030] As shown in FIG. 1 , the fluid sensor device 100 can include a large calibration fluid compartment 110 that stores a volume of calibration fluid that can last the entire operational lifetime of the fluid sensor device 100. For example, the volume of calibration fluid stored in the calibration fluid compartment 110 can be sufficient to calibrate the sensing element 130 before and / or after each measurement of the sample fluid for as many test or sample cycles as the fluid sensor device 100 is designed for. Maintaining a large volume of calibration fluid within the fluid sensor device 100 to ensure that the calibration fluid is fresh and has consistent properties for calibrating the sensing element 130 can be very costly, inconvenient, and increase the overall size of the device 100. In accordance with the disclosure of various embodiments herein, FIGS. 2-3C illustrate embodiments of a fluid sensor system that can utilize multiple sources of calibration fluid and allow a reduced-size calibration compartment to be filled during storage and transport prior to a procedure. Unless otherwise noted, the components of fluid sensor system 2000 may be identical to or generally similar to the components of fluid sensor system 1000 having the same reference numbers incremented by 100 relative to the reference numbers of FIG. 1, and may function or operate in a generally similar manner.

[0031] A fluid sensor system 2000 disclosed herein may include a fluid sensor device 200 as shown in FIG. 2 and may operate according to the flowchart of FIG. 4. The fluid sensor device 200 may also include a sensing element 230 configured to interact with a fluid in a sensing channel 232. In some embodiments, the sensing element 230 may take a measurement of the fluid in the sensing channel 232 and transmit a signal indicative of the measurement, e.g., a voltage relative to a reference electrode. In some embodiments, referring to FIG. 5, the fluid sensor system 2000 may include a processor 280 and / or memory 238 configured to process and / or store information transmitted from the sensing element 230. In some embodiments, the fluid sensor system 2000 may also include a controller 236 configured to control the fluid sensor device 200 to operate in multiple modes (e.g., a calibration mode, a sensing mode, etc.). In some embodiments, the controller 236 may be configured to control one or more valves 240 on the fluid sensor device 200 to direct fluid flow within the fluid sensor device 200. In some embodiments, the controller 236, the processor 280, and / or the memory 238 may be located on the fluid sensor device 300. In some embodiments, the controller 236, the processor 280, and / or the memory 238 may be located on a separate reader device connectable to the fluid sensor device 200. In some embodiments, the controller 236 and the processor 280 may be formed or provided in the same chip or device or in separate chips or devices.

[0032] In some embodiments, fluid sensor device 200 may include a calibration compartment 210 that is filled with a calibration fluid before fluid sensor device 200 is connected to a treatment system. In some embodiments, calibration compartment 210 may have a volume that is less than the total volume of calibration fluid required for the entire operational lifetime of fluid sensor device 200. In some embodiments, calibration compartment 210 may have a volume, for example, in the range of 5 to 100 microliters, in the range of 10 to 50 microliters, in the range of 10 to 100 microliters, in the range of 20 to 40 microliters, in the range of 100 to 1000 microliters, or in the range of about 30 microliters.

[0033] In some embodiments, the fluid sensor device 200 may include a second calibration fluid compartment 258 that is empty before the fluid sensor device 200 is connected to a treatment system. In some embodiments, the second calibration fluid compartment 258 can be kept empty during storage or transport to reduce costs. In other embodiments, the second calibration fluid compartment 258 may be at least partially pre-filled with fluid during storage and / or transport. In some embodiments, the fluid sensor device 200 may be connected in-line with a treatment line 251 that is connected to a treatment system. In some embodiments, only the second calibration fluid 250 (e.g., a physiological solution) may pass through the treatment line 251. In some embodiments, the second calibration fluid 250 and / or the sample fluid (e.g., a patient's blood) may selectively pass through the treatment line 251.

[0034] In some embodiments, when fluid sensor device 200 is initially connected to a treatment system, controller 236 of fluid sensor device 200 may be configured to initiate a first calibration mode, in which controller 236 may cause calibration fluid in calibration compartment 210 to flow into sensing channel 232 and interact with sensing element 230. In some embodiments, controller 236 may control one or more valves 240 to provide calibration fluid flow from calibration compartment 210 to sensing channel 232. During the first calibration mode, or block 402 shown in FIG. 4 , sensing element 230 may obtain a first measurement of the calibration fluid from calibration compartment 210 and transmit a signal including the first measurement (e.g., a potential difference between an electrode of sensing element 230 and a reference electrode) to memory 230 of fluid sensor system 2000 for storage and / or processing by processor 280 (see FIG. 5 ).

[0035] In some embodiments, after the calibration fluid from calibration compartment 210 interacts with sensing element 230 and passes to waste compartment 220, controller 236 of fluid sensor device 200 can then cause a second calibration fluid 250 (e.g., a physiological solution) from treatment line 251 entering through inlet 252 of fluid sensor device 200 to flow into second calibration fluid compartment 258. Thereafter, in some embodiments, controller 236 can cause second calibration fluid 250 to be stored in second calibration fluid compartment 258. In some embodiments, controller 236 can cause second calibration fluid 250 to flow into and be stored in second calibration fluid compartment 258 by controlling one or more valves 240.

[0036] In some embodiments, a second calibration mode may then be initiated by controller 236 to provide second calibration fluid 250 from second calibration fluid compartment 258 to sensing channel 232 to interact with sensing element 230. As shown in FIG. 4 , sensing element 230 may take a second measurement of second calibration fluid 250 and transmit a signal including the first measurement (e.g., a potential difference between an electrode of sensing element 230 and a reference electrode) to memory 230 of fluid sensor system 2000 for storage and / or processing by processor 280 (see FIG. 5 ). In some embodiments, in block 406, processor 280 may then compare the first measurement taken in block 402 with the second measurement taken in block 404 to determine a difference that is stored in memory 238. The stored difference can be used in a subsequent calibration mode as a reference to calibrate sensing element 230 using a treatment solution or second calibration fluid 250 coming from an external source instead of the existing calibration fluid from calibration compartment 210. For example, in some embodiments, after a sample fluid detection event in which sample fluid flows through treatment line 251 into sensing channel 232 and interacts with sensing element 230, second calibration fluid 250 can be provided from second calibration fluid compartment 258 to sensing channel 232 to flush out any remaining sample fluid or debris and interact with sensing element 230 in order for sensing element 230 to take a third measurement. In some embodiments, in block 410, sensing element 230 can then calibrate and reconfigure sensing element 230 using the third measurement and the stored difference as a reference. Thereby, enough calibration fluid for only one calibration event (eg, a first calibration event) can be stored in the calibration compartment 210 before the fluid sensor device 200 is connected to a treatment system.

[0037] In some embodiments, after fluid is provided to sensing channel 232 and interacts with sensing element 230, the fluid flows to waste compartment 220. In some embodiments, one of one or more valves 240 may be positioned between sensing channel 232 and waste compartment 220, such that controller 236 may also be configured to control when and whether fluid is directed to waste compartment 220.

[0038] 3A-3C illustrate another embodiment of a fluid sensor system 3000 disclosed herein. The fluid sensor system 3000 may include a fluid sensor device 300 configured to connect to a treatment system. In some embodiments, the fluid sensor system 3000 may operate similarly to the fluid sensor system 2000, as shown in FIG. 4. Unless otherwise noted, the components of the fluid sensor system 3000 may be identical to or generally similar to, and may function or operate in a generally similar manner to, the same numbered components of the fluid sensor system 2000, which have reference numbers incremented by 100 relative to the reference numbers of FIG. 2.

[0039] In some embodiments, fluid sensor device 300 can be configured to connect in-line to treatment line 351, with inlet 352 connecting to one point on treatment line 351 and outlet 354 connecting to another point on treatment line 351. In some embodiments, one end of treatment line 351 can be connected to second calibration fluid source 304 and the other end of treatment line 351 can be connected to patient 302. In some embodiments, second calibration fluid 350 (e.g., a physiological solution) and / or sample fluid 353 (e.g., the patient's blood) can selectively pass through treatment line 351. In some embodiments, treatment line 351 can include pump 360 configured to control fluid flow within treatment line 351. In some embodiments, pump 360 can be configured to cause second calibration fluid 350 to flow through at least a portion of treatment line 351 toward fluid sensor device 300, or cause sample fluid 352 to flow through at least a portion of treatment line 351 toward fluid sensor device 300. When the fluid sensor device 300 is initially connected to the treatment line 351, in some embodiments, the controller 336 (see FIG. 5) of the fluid sensor system 3000 may control one or more valves 340 to retain the second calibration fluid 350 within the treatment line 351 without entering the sensing channel 332 as shown in FIG. 3A.

[0040] In some embodiments, the fluid sensor device 300 may include a calibration compartment 310 having a volume that is smaller than the total volume of calibration fluid required over the entire operational life of the fluid sensor device 300. In some embodiments, the calibration compartment 310 may have a volume in the range of 5 to 100 microliters, in the range of 10 to 50 microliters, in the range of 20 to 40 microliters, or in the range of about 30 microliters, for example. In some embodiments, the calibration compartment 310 may have a volume sufficient for only one calibration event as described above.

[0041] 2, fluid sensor device 300 of fluid sensor system 3000 may omit the second calibration compartment compared to the embodiment of FIG. 2 and instead may draw second calibration fluid 350 from treatment line 351 directly into sensing channel 332 during a calibration mode / event without being stored in or contained in a separate compartment. During a first calibration mode, in some embodiments, fluid sensor system 3000 may similarly provide calibration fluid from calibration compartment 310 to sensing channel 332 and operate according to block 402 to obtain a first measurement of the calibration fluid in 310 using sensing element 330 (see FIG. 4).

[0042] Thereafter, during the second calibration mode, the controller 236 may control one or more valves 340 to direct the second calibration fluid 350 to flow into the sensing channel 332 and interact with the sensing element 330, as shown in FIG. 3B. The fluid sensor system 3000 may operate according to block 404 to obtain a second measurement of the second calibration fluid 350 using the sensing element 330 and determine a difference between the first and second measurements using the processor 380 (see FIG. 5). The fluid sensor system 3000 may then store the difference in memory 338 according to block 406 and use the stored difference to calibrate the sensing element 330 during the second calibration event and / or each subsequent calibration event.

[0043] In some embodiments, the first measurement of the calibration fluid from the calibration compartment 310 may also be stored in the memory 338. Thereby, in some embodiments, the fluid sensor system 3000 may instead take measurements of the second calibration fluid 350, determine a difference relative to the first measurement during each subsequent calibration event, and use the determined difference to calibrate the sensing element 330 without storing the difference.

[0044] In some embodiments, when the second calibration fluid source is changed to provide a third solution different from the second calibration fluid 350, the processor 280 of the fluid sensor system 3000 may receive input that the second calibration fluid source has been changed and configure the memory to erase any stored information (e.g., stored differences) regarding the previous calibration fluid. In some embodiments, the calibration compartment 310 may contain enough calibration fluid to perform two or more calibration events so that new measurements of the calibration fluid can be taken to determine new differences.

[0045] After the initial calibration event, the fluid sensor system 3000 may operate to provide sample fluid 352 by altering the flow of fluid in the treatment line 351 using pump 360 and to provide sample fluid 352 to the sensing channel 332 by controlling one or more valves 340 as shown in FIG. 3C during the sensing mode. After a measurement of the sample fluid 352 is taken, the fluid sensor system 3000 may again begin the calibration mode to flush out any residue and recalibrate the sensing element 330, as described above.

[0046] The foregoing disclosure is not intended to limit the disclosure to the precise form or particular field of use disclosed. Accordingly, various alternative embodiments and / or modifications of the disclosure, whether expressly described or implied herein, are contemplated as being possible in light of the present disclosure. Thus, while embodiments of the present disclosure have been described, those skilled in the art will recognize that changes can be made in form and detail without departing from the scope of the present disclosure. Accordingly, the present disclosure is limited only by the claims.

[0047] In the foregoing specification, the present disclosure has been described with reference to specific embodiments. However, as those skilled in the art will understand, the various embodiments disclosed herein can be modified or embodied in various other ways without departing from the spirit and scope of the present disclosure. Accordingly, this description is to be considered illustrative and is intended to teach those skilled in the art how to make and use various embodiments of the disclosed fluid sensor system. It should be understood that the forms of the disclosure shown and described herein should be considered representative embodiments. Equivalent elements, materials, processes, or steps may be substituted for those typically shown and described herein. Furthermore, certain features of the present disclosure may be utilized independently of the use of other features, all of which will be apparent to those skilled in the art after having the benefit of this description of the present disclosure. The terms "including," "comprising," "incorporating," "consisting of," "have," and the like, used to describe and claim the present disclosure, are intended to be construed in a non-exclusive manner, i.e., allowing for the presence of items, components, or elements not expressly described. References to the singular are also to be construed as relating to the plural.

[0048] Furthermore, the various embodiments disclosed herein should be understood in an illustrative and descriptive sense and should not be construed as limiting the present disclosure in any way. All connector references (e.g., attached, affixed, coupled, connected, etc.) are used solely to aid the reader's understanding of the present disclosure and should not impose any limitations on the location, orientation, or use of the systems and / or methods disclosed herein, among other things. Therefore, connector references, if any, should be interpreted fairly. Furthermore, such connector references do not necessarily infer that two elements are directly connected to one another. In addition, all numerical terms, such as "first," "second," "tertiary," "primary," "secondary," "main," or any other conventional and / or numerical term, should also be taken solely as identifiers to aid the reader's understanding of the various elements, embodiments, variations, and / or modifications of the present disclosure and should not impose any limitations, particularly regarding the order or preference of any element, variation, and / or modification relative to another element, embodiment, variation, and / or modification.

[0049] It will also be understood that one or more of the elements shown in the drawings / figures may be implemented in a more separated or integrated manner as may be useful depending on the particular application, or may in certain cases be removed or rendered inoperable. [Explanation of symbols]

[0050] 100 Fluid sensor device 110 Calibration fluid compartment 120 waste compartment 130 Sensing Elements 132 detection channels 150 Treatment Line 152 Entrance 154 Exit 200 Fluid Sensor Device 210 Calibration Compartment 220 Waste Compartment 230 Sensing Elements 230 memory 232 detection channels 236 Controller 238 memory 240 Valve 250 Second Calibration Fluid 251 Treatment Line 252 Entrance 258 Second Calibration Fluid Compartment 280 processor 300 Fluid Sensor Device 302 patients 304 Second Calibration Fluid Source 310 Calibration Compartment 330 Sensing Elements 332 direct detection channels 336 Controller 338 memory 340 Valve 350 Second Calibration Fluid 351 Treatment Line 352 Entrance 353 Sample Fluid 354 Exit 360 Pump 380 processor 1000 Fluid Sensor System 2000 Fluid Sensor System 3000 Fluid Sensor System

Claims

1. 1. A method of calibrating a fluid sensor device connected in-line with a treatment system, the method comprising: providing a first calibration fluid stored in a calibration compartment to the sensing element; obtaining a first measurement of the first calibration fluid using the sensing element; providing a second calibration fluid from a second calibration fluid source external to the fluid sensor device; storing the second calibration fluid in a second calibration compartment within the fluid sensor device; obtaining a second measurement of the second calibrant fluid using the sensing element; calibrating the sensing element using the second calibration fluid.

2. 10. The method of claim 1, further comprising connecting an inlet of the fluid sensor device to a first point in a treatment line of the treatment system and an outlet of the fluid sensor device to a second point in the treatment line of the treatment system.

3. The method of claim 1 , wherein the second calibration compartment is empty before being connected to the treatment system.

4. The method of claim 1 , further comprising determining a difference between the first measurement of the first calibration fluid and the second measurement of the second calibration fluid.

5. 5. The method of claim 4, wherein calibrating the sensing element includes comparing the second measurement of the second calibration fluid to the difference between the first measurement of the first calibration fluid and the second measurement of the second calibration fluid.

6. The method of claim 2 , wherein the treatment line connects a patient and the second source of calibration fluid.

7. The method of claim 1 , wherein the second calibration fluid comprises a physiological solution.

8. The method of claim 6 , further comprising providing a sample fluid from the patient through the treatment line to the sensing element.

9. 9. The method of claim 8, further comprising controlling a direction of fluid flow in the treatment line to provide the second calibration fluid from the second calibration fluid source to the sensing element after providing the sample fluid from the patient through the treatment line to the sensing element.

10. 1. A fluid sensor system configured to perform measurements of a sample fluid in-line with a treatment system, the fluid sensor system comprising: a fluid sensor device, the fluid sensor device comprising: a sensing channel configured to receive sample fluid from the treatment system; a first calibration compartment containing a first calibration fluid and in fluid communication with the sensing channel; a second calibration compartment internal to the fluid sensor device configured to receive a second calibration fluid from a second calibration fluid source external to the fluid sensor device, the second calibration compartment in fluid communication with the sensing channel; a sensing element configured to interact with and transduce a property of a fluid in the sensing channel.

11. The fluid sensor system of claim 10, wherein the first calibration compartment has a volume in the range of 5 to 100 microliters.

12. The fluid sensor system of claim 10 , wherein the second calibration fluid source comprises a treatment line of the treatment system.

13. 11. The fluid sensor system of claim 10, further comprising a processor configured to determine a difference between a first measurement value obtained by the sensing element of the first calibration fluid and a second measurement value obtained by the sensing element of the second calibration fluid, and to calibrate the sensing element based at least on the measurement value obtained by the sensing element of the second calibration fluid and the determined difference.

14. 11. The fluid sensor system of claim 10, wherein the second calibration compartment is empty during a storage mode, and wherein the fluid sensor system is not connected to the treatment system during the storage mode.

15. 1. A fluid sensor system configured to perform measurements of a sample fluid in-line with a treatment system, the fluid sensor system comprising: a fluid sensor device, the fluid sensor device comprising: a sensing channel configured to receive sample fluid from the treatment system; a calibration compartment containing a first calibration fluid and in fluid communication with the sensing channel, the calibration compartment having a volume in the range of 5 to 100 microliters; a second calibration compartment internal to the fluid sensor device configured to receive a second calibration fluid from a second calibration fluid source external to the fluid sensor device, the second calibration compartment in fluid communication with the sensing channel; a sensing element configured to interact with a fluid in the sensing channel.

16. 16. The fluid sensor system of claim 15, further comprising a controller configured to control one or more valves to selectively direct only the second calibration fluid from the treatment system to the detection channel in a calibration mode, and to control the one or more valves to selectively direct only the sample fluid from the treatment system to the detection channel in a detection mode.

17. 17. The fluid sensor system of claim 16, further comprising a processor configured to determine a difference between a first measurement value obtained by the sensing element of the first calibration fluid and a second measurement value obtained by the sensing element of the second calibration fluid, and to calibrate the sensing element in the calibration mode based at least on the measurement value obtained by the sensing element of the second calibration fluid and the determined difference.

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