Tracking of Insertion Time and Removal Time of Continuous Glucose Monitoring Sensor

Abstract

In response to insertion of a continuous glucose monitoring (CGM) sensor into the user's skin, the CGM system compares the sensor's identifier with any previously stored identifiers of previously inserted sensors. If the identifier does not match a previously stored identifier, indicating a newly inserted sensor, the identifier and timestamp are stored, and CGM may begin. If there is sensor removal, a removal timestamp is stored. If the inserted sensor's identifier matches a previously stored identifier, indicating a reinserted sensor, the reinsertion time is obtained, and the elapsed removal time is checked to determine if it exceeds the maximum removal time limit. If so, the CGM is stopped. If not, the CGM may continue with the reinserted sensor. As with other aspects, methods for tracking CGM sensor insertion and removal times are also provided.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the benefit of U.S. Provisional Patent Application No. 63 / 051,853, filed on Jul. 14, 2020, the disclosure of which is incorporated herein by reference in its entirety for all purposes.

[0002] The present invention generally relates to continuous glucose monitoring (CGM).

Background Art

[0003] CGM has become a daily monitoring operation in diabetes care. By providing real - time glucose readings, therapeutic actions can be applied in a more timely manner and blood glucose levels can be better controlled. During CGM operation, the sensor of the CGM device is typically inserted subcutaneously and operates continuously in an environment surrounded by tissue and interstitial fluid. The sensor inserted under the user's skin provides a signal indicating the user's glucose level to the wireless transmitter unit of the CGM device. Glucose readings can be automatically performed many times throughout the day (e.g., every few minutes or at some other pre - established time intervals).

[0004] The CGM device can be attached to the outer surface of the user's skin, such as the abdomen or the dorsal side of the upper arm, while the sensor is inserted through the skin and in contact with the interstitial fluid. The sensor interacts with the interstitial fluid and generates an electrical signal proportional to the amount of glucose present. These electrical signals are communicated to the transmitter unit for use in determining glucose levels.

[0005] The CGM device can be worn on the body for several days or weeks before the sensor needs to be removed and replaced. In some cases, it may be necessary to remove and re - insert the sensor, for example, to address issues related to the attachment of the CGM device to the user's skin.

Summary of the Invention

[0006] In some embodiments, a continuous glucose monitoring (CGM) system is provided that includes a sensor unit memory and a sensor unit having a sensor, the sensor unit memory storing an identifier therein. The CGM system also includes a second memory configured to store a plurality of sensor identifiers therein. The CGM system further includes a real-time clock and a processor, the processor communicating with the second memory, the real-time clock, and the sensor unit. The processor is configured to (1) read the identifier stored in the sensor unit memory, (2) determine whether the identifier matches any previously stored identifier in the second memory, (3) in response to the identifier not matching any previously stored identifier in the second memory, store the identifier and an insertion timestamp in the second memory, the real-time clock being used to generate the insertion timestamp, (4) in response to the identifier matching a previously stored identifier in the second memory, obtain a reinsertion time using the real-time clock, and (5) use the reinsertion time to determine whether the sensor has exceeded a predetermined maximum removal time limit, by executing computer instructions to perform the foregoing.

[0007] In some embodiments, a continuous glucose monitoring (CGM) system is provided that includes a sensor configured to be inserted into a user's skin and generate an electrical signal indicative of a glucose level. The CGM system also includes a real-time clock, a first memory storing an identifier that identifies the sensor internally, a second memory configured to store a plurality of sensor identifiers internally, and a processor that communicates with the real-time clock and the first and second memories. The processor is configured to (1) read the identifier stored in the first memory, (2) determine whether the identifier matches any previously stored identifier in the second memory, (3) in response to the identifier not matching any previously stored identifier in the second memory, store the identifier and an insertion timestamp in the second memory, where the real-time clock is used to generate the insertion timestamp, and (4) in response to the identifier matching a previously stored identifier in the second memory, obtain a reinsertion time using the real-time clock, and (5) use the reinsertion time to determine whether the sensor has exceeded a predetermined maximum removal time limit, by executing computer instructions for doing so.

[0008] In some embodiments, a method for tracking the insertion and removal times of a continuous glucose monitoring (CGM) sensor is provided. The method includes reading, via a processor executing computer instructions in response to activation of the CGM, an identifier of the sensor from a sensor unit memory, determining whether the identifier matches any previously stored identifier in a second memory, storing the identifier and an insertion timestamp in the second memory in response to the identifier and the insertion timestamp not matching any previously stored identifier in the second memory, obtaining a reinsertion time in response to an identifier matching a previously stored identifier in the second memory, using the reinsertion time to determine whether the sensor has exceeded a predetermined maximum removal time limit, and stopping operation of the CGM in response to determining that the sensor has exceeded the predetermined maximum removal time limit.

[0009] Still other aspects, features, and advantages of the present disclosure may become readily apparent from the following detailed description and illustrations of several exemplary embodiments and implementations, including the best mode contemplated for carrying out the invention. The present disclosure may enable other different embodiments and may make several details in various aspects subject to change without departing from the scope of the invention. For example, the following description relates to continuous glucose monitoring, but the devices, systems, and methods described below may be readily adaptable for monitoring other analytes, such as cholesterol, lactate, uric acid, alcohol, etc., in other continuous analyte monitoring systems. The present disclosure is intended to embrace all modifications, equivalents, and alternatives within the scope of the appended claims (see further below).

Brief Description of the Drawings

[0010] The drawings described below are for illustrative purposes only and are not necessarily drawn to scale. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. The drawings are not intended to limit the scope of the invention in any way.

Figure 1

Figure 2

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Figure 5A

Figure 5B

Figure 5C

Figure 5D

[0011] Continuous Glucose Monitoring (CGM) methods and systems have been developed to more closely monitor and detect changes in a person's glucose concentration level. CGM methods and systems typically continuously generate an electrochemical glucose signal during operation and perform glucose measurements / estimations typically based on signals generated every few minutes.

[0012] A CGM system generally has a wearable portion (CGM device) that is worn on the body and communicates (e.g., wirelessly) with an external device such as a handheld CGM receiver or another portable device such as a smartphone that runs a suitable application software program. The CGM device may be worn for several days, or a week or two, before removal and replacement is required. The CGM device includes a sensor that is inserted (implanted) subcutaneously. The CGM device may also include an analog circuit that is coupled to the sensor, biases the sensor, and is configured to measure an electrical current signal generated by the inserted sensor in contact with interstitial fluid. The CGM device may also include a processing circuit for determining a glucose concentration level based on the measured electrical current signal. The CGM device may further include an electronic transmitter circuit for communicating the determined glucose level to an external device (e.g., a smart device or CGM receiver). The CGM device may be attached to the outer surface of the skin, such as the abdomen, the dorsal side of the upper arm, or other suitable locations, for example, via an adhesive.

[0013] The CGM system can provide frequent measurements of the user's glucose level without the need for each such measurement to involve the collection of a blood sample such as a fingerstick. The CGM system may still sometimes use the use of a blood glucose measurement (BGM) system such as a fingerstick and a Contour NEXT One (registered trademark) by Ascensia Diabetes Care AG of Basel, Switzerland, to initiate calibration of the CGM system.

[0014] The CGM device of the CGM system can typically be worn for up to about two weeks, after which the sensor can be removed and replaced. In some embodiments, the entire CGM device can be removed and replaced. In another embodiment, the CGM device may include a replaceable sensor unit that can be detached by the user from a reusable transmitter unit of the CGM device. In such embodiments, it may be necessary to remove and replace only the sensor unit of the CGM device.

[0015] The CGM system can be configured to notify the user, e.g., via a display message and / or an audible alert, when the sensor reaches its maximum allowable insertion time limit (e.g., 10 days or 14 days) and should be replaced. The CGM system can also prevent glucose measurements from occurring with such an EOL ("end-of-life") sensor. However, the user may attempt to reuse the EOL sensor by removing the sensor from the user's skin surface and then reinserting it into the skin as if it were new. For a number of health and performance reasons, a CGM system configured to prevent this from occurring would be desirable. However, the user may also have problems with the CGM device during operation, e.g., problems with the CGM device adhering to the user's skin surface, and the user may have to remove and reinsert the sensor to correct the problem. The CGM system would also desirably be configured to distinguish this situation from an attempt to reuse the EOL sensor. The CGM system would more desirably be configured to determine and prevent the reused sensor from being used if the reinserted sensor has been removed from the user's skin surface for too long a period of time. Such a sensor is no longer sterilized and may be contaminated, and if reused, may lead to health and / or other problems.

[0016] According to one or more embodiments, devices, systems, and methods are provided herein for tracking the insertion time and removal time of a CGM sensor, and subsequent detections that exceed a maximum removal time limit and / or a maximum insertion time limit, as will be described in more detail below in connection with FIGS. 1-5D.

[0017] FIG. 1 illustrates a wearable CGM device 100 inserted into a user's skin 102 according to one or more embodiments. The CGM device 100 is configured to continuously monitor and periodically provide glucose measurements (e.g., every 5 minutes, or other suitable time intervals). The CGM device 100 is shown partially as a dome shape, but the CGM device 100 may have other shapes. The CGM device 100 may include a sensor unit 104 and a transmitter unit 106. In some embodiments, the sensor unit 104 and the transmitter unit 106 may be integrally formed. In other embodiments, the sensor unit 104 may be disposable, replaceable, and detachable from the transmitter unit 106, which may be reusable with other sensor units. The sensor unit 104 and the transmitter unit 106 may be physically connected together via any suitable mechanical mechanism. The sensor unit 104 and the transmitter unit 106 may also be electrically coupled together such that when physically connected, data and control signals can be communicated and transmitted between electrical components within the sensor unit 104 and the transmitter unit 106. In some embodiments, the initiation of communication between the sensor unit 104 and the transmitter unit 106 may respond to physically connecting the two units together. In other embodiments, the communication may be initiated by a command such as a start command. The communication between the sensor unit 104 and the transmitter unit 106 may be initiated in other suitable ways.

[0018] The sensor unit 104 may include a sensor 108, a portion of which is shown inserted through the user's skin 102. The sensor 108 may extend from the sensor unit 104 through a base plate 110 and may be configured to be at least partially located within interstitial fluid in the user's subcutaneous region. The sensor 108 may be or include an analyte sensor or an analyte sensor portion such as at or near the sensor tip 108T. The sensor 108 may be inserted with an insertion device (not shown) having a sharp needle or "introducer" that pierces the skin to introduce the sensor 108 into the user's subcutaneous region. Any suitable insertion device may be used.

[0019] The sensor unit 104 may also include an adhesive layer 112 that can be, for example, a double-sided tape or a pressure-sensitive adhesive. One side of the adhesive layer 112 can be adhered to the base plate 110, while the other side of the adhesive layer 112 can be adhered to the user's skin surface 102S.

[0020] The transmitter unit 106 may include one or more electronic components that communicate with one or more electronic components within the sensor unit 104 and communicate with one or more external devices, as described in more detail below.

[0021] FIG. 2 illustrates a circuit component configuration 200 of the CGM device 100 according to one or more embodiments. The sensor unit 104 may include a sensor assembly 214 and a sensor unit memory 216. The sensor assembly 214 may include a sensor 108 and a sensor circuit (not shown separately) coupled to the sensor 108. The sensor circuit may apply at least one bias voltage to the analyte sensor portion of the sensor 108, which may generate an electrical signal while the sensor 108 is in contact with interstitial fluid. The sensor circuit may also facilitate conduction of an electrical signal between the sensor tip 108T of the sensor 108 and / or other portions of the sensor 108.

[0022] The sensor unit memory 216 may include a programmable read-only memory (PROM), an electrically erasable programmable read-only memory (EEPROM), a write-once read-many memory (WORM), a static random access memory (SRAM), a synchronous dynamic random access memory (SDRAM), a physically unclonable function (PUF) (which can function as a unique identifier), and / or NOR and NAND flash memories. Other suitable types of sensor memory circuits may be used for the sensor unit memory 216.

[0023] In some embodiments, the sensor unit memory 216 may include a radiation-hardened memory (rad-hard memory), or may be located within a rad-hard package that retains information (e.g., data) stored internally when the package and / or the memory is exposed to radiation used to sterilize the sensor unit 104.

[0024] The sensor unit memory 216 may store sensor information specific to its individual sensor unit and internal components. For example, the sensor information may include a sensor unit identifier (e.g., the serial number of the sensor unit), a corresponding maximum insertion time limit (e.g., 3, 10, or 14 days), and a corresponding maximum removal time limit (e.g., 15, 45, or 60 minutes). The identifier may be unique or at least partially unique (e.g., the manufacturer may avoid reusing the same identifier within a specific period or specific geographical area so that a user is less likely to insert a sensor with the same identifier as a different recently inserted sensor). The maximum insertion time limit is the period during which the sensor should be removed and replaced (i.e., the sensor has reached its EOL). The maximum removal time limit is the period during which a sensor removed from the user's skin is considered unsuitable for reinsertion (e.g., for health or performance reasons) and thus should not be reinserted even if the maximum insertion time limit has not been reached.

[0025] In some embodiments, the sensor information may also include, for example, one or more of the following parameters. a) Electrode sensitivity gradient, b) Manufacturing date, c) Expiration date (shelf life), d) Batch or lot number, e) Security code, and / or f) Version of the memory device.

[0026] Other parameters and / or sensor information may be stored in the sensor unit memory 216. Additionally or alternatively, some or all of the above parameters and / or sensor information may be encoded in the sensor unit 104, the CGM device 100, and / or a barcode attached to its package, etc.

[0027] In some embodiments, electrical data, control signals, and power are transmitted between the sensor unit 104 and the transmitter unit 106 via the connector 218, the electrical contact pads 220 and 222 of the sensor unit 104, and the electrical contact pads 224 and 226 of the transmitter unit 106 when the sensor unit 104 and the transmitter unit 106 are physically connected together.

[0028] The transmitter unit 106 may include power sources such as an analog front end 228, a microcontroller 230 (or other similar processing resources), a memory 232, a real-time clock 233, a wireless transmitter 234, a switch 235, and a battery 236. In some embodiments, the transmitter unit 106 may include a local display (not shown) for displaying information such as glucose concentration information, sensor EOL, etc. without using an external device.

[0029] The analog front end 228 may be configured to drive the sensor assembly 214 and / or process sensor data generated by the sensor assembly 214 and the sensor 108. For example, the analog front end 228 may be configured to apply a bias voltage to the sensor assembly 214 and measure the resulting current passing through the sensor assembly 214. In conjunction with the sensor assembly 214, the analog front end 228 may apply a bias voltage to the inserted sensor 108 located in the interstitial fluid and measure the resulting current proportional to the glucose concentration. The analog front end 228 may perform other, fewer, or more functions.

[0030] The microcontroller 230 can be coupled to an analog front end 228, a memory 232, a real-time clock 233, a wireless transmitter 234, a switch 235, and a battery 236, and optionally other circuits (not shown). The microcontroller 230 can include a processor, such as a microprocessor or other suitable processing circuit, for processing sensor data generated by the sensor assembly 214 and / or the analog front end 228 and for detecting reinsertion of the sensor as described herein. The microcontroller 230 can also include an analog-to-digital converter for converting, for example, an analog current signal generated by the sensor assembly 214 into a digital current signal. The microcontroller 230 can further store the digital current signal value in the memory 232 and / or calculate or estimate a glucose concentration level based at least in part on the digital current signal. The microcontroller 230 can also further detect whether the sensor of the CGM device has met its maximum insertion time limit and / or whether the sensor of the CGM device has been reinserted, and whether the reinserted sensor has exceeded its maximum removal time limit, as described in more detail below in connection with FIGS. 4-5D. The microcontroller 230 can perform other suitable functions.

[0031] The microcontroller 230 and / or other circuitry within the transmitter unit 106 may be electrically coupled to and configured to communicate with the sensor unit memory 216. The microcontroller 230 may receive data stored in the sensor unit memory 216, such as, for example, an identifier of the sensor unit 104 and maximum insertion time limit and removal time limit, along with other such sensor information related to one or more parameters of one or more components of the sensor unit 104. In some embodiments, a signal (e.g., a pull signal) may be transmitted from the microcontroller 230 to the sensor unit memory 216 to cause the sensor unit memory 216 to transmit data without user input. Accordingly, the sensor unit memory 216 may automatically transmit data to the microcontroller 230 in response to a connection of the sensor unit 104 to the transmitter unit 106. Alternatively, the transmission of sensor information from the sensor unit memory 216 to the microcontroller 230 may occur in response to a prompt, such as from an external device, or in any other suitable manner.

[0032] The microcontroller 230 may store information received from the sensor unit memory 216 in the memory 232 and use that information when calculating an analyte concentration, detecting whether the sensor 108 has been reinserted (and in that case, whether the sensor 108 has met and / or exceeded the maximum insertion time limit and removal time limit), and performing other functions. In other embodiments, the information may remain in the sensor unit memory 216 and may be accessed as needed by the microcontroller 230 or other circuitry during CGM processing.

[0033] Additionally or alternatively, the microcontroller 230 and the memory 232 may receive sensor information from, for example, one or more barcodes attached to the sensor unit 104, the CGM device 100, and / or its package, via scanning by an external device that communicates with the transmitter unit 106.

[0034] When executed by a processor within the microcontroller 230, the memory 232 may include computer program code stored therein that causes the CGM device 100 to communicate with one or more external devices, such as a CGM receiver or a smart device (e.g., a smartphone or a tablet) that can execute various functions and / or calculate and / or display glucose levels and related data when executing a CGM application software program.

[0035] The memory 232 may also be configured to store a plurality of sensor unit identifiers corresponding to previously used sensor units in an embodiment where the sensor unit 104 is replaceable and detachable from the transmitter unit 106 which is reusable with other sensor units. In some embodiments, the identifiers corresponding to the previously used sensor units may be stored, for example, in cloud-based storage and downloaded to the memory 232 as needed.

[0036] When executed by a processor within the microcontroller 230, the memory 232 may further include computer program instructions stored therein that cause the CGM device 100 to determine, in part, whether an identifier stored in the sensor unit memory 216 matches any previously stored identifier in the memory 232, and in response to a determination that the identifier stored in the sensor unit memory 216 matches a previously stored identifier in the memory 232, cause the sensor 108 to determine whether a predetermined maximum removal time limit has been exceeded.

[0037] In some embodiments, memory 232 can be a radiation-hardened memory (rad-hard memory), or can be located in the same or an identical rad-hard package as sensor unit memory 216. Memory 232 can be a non-volatile memory and can include, but is not limited to, an electrically programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), and / or a flash memory (e.g., a type of EEPROM in either a NOR or NAND configuration). Other suitable types of memory can be used for memory 232, including reading data from an Internet storage location that can be cloud-based.

[0038] In some embodiments, switch 235 can be any suitable mechanical or electrical switch that indicates whether sensor unit 104 is physically and electrically connected to transmitter unit 106. That is, switch 235 can have one output indicating that sensor unit 104 is physically and electrically connected to transmitter unit 106, and another output (e.g., when sensor 108 is removed from the user's skin) indicating that sensor unit 104 is not physically and electrically connected to transmitter unit 106.

[0039] In addition to or alternatively to switch 235, in other embodiments, the computer program instructions stored in memory 232, or the CGM application software program executed on an external device, can have an encoded "software switch" that monitors whether any current is received from sensor 108. If no current is received (or measured), the software switch can indicate an error condition (e.g., that sensor 108 has been removed from the user's skin).

[0040] The battery 236 is located in the transmitter unit 106 and can supply power to the transmitter unit 106. In some embodiments, the battery 236 can be rechargeable. When the sensor unit 104 is connected to the transmitter unit 106, the battery 236 can also supply power to the sensor unit 104. Providing power to the sensor unit 104 can, in some embodiments, initiate communication between the sensor unit 104 and the transmitter unit 106, initiate detection of sensor insertion, and / or initiate CGM processing. In some embodiments, power can be provided to the sensor unit 104 via the analog front end 228. In other embodiments, the battery 236 may be located within the sensor unit 104 instead of the transmitter unit 106, and in still other embodiments, the sensor unit 104 and the transmitter unit 106 can each have their own battery. Examples of the battery 236 include coin-type batteries such as flexible lithium polymer batteries, lithium manganese, silver oxide, and alkaline coin batteries (e.g., CR2032, SR516, and LR60 type coin batteries). Other power source / battery types can be used.

[0041] In some embodiments, the microcontroller 230 can transmit electrical signals, glucose concentration information, and / or other information to one or more external devices via the wireless transmitter 234. In some embodiments, the microcontroller 230 can receive electrical signals, commands, data, and / or other information from one or more external devices via the wireless transmitter 234.

[0042] FIG. 3 illustrates a CGM system 300 according to one or more embodiments. The CGM system 300 includes a CGM device 100 and an external device 330. The external device 330 can be, for example, a dedicated CGM receiver or a smart device that executes a CGM application software program. The external device 330 can include a processor 331, a memory 332, a real-time clock 333, a wireless transmitter 334, and a display 336, and the processor 331 is coupled to each of the memory 332, the real-time clock 333, the wireless transmitter 334, and the display 336, and each can be any suitable device or component configured to perform at least some or all of the CGM-related functions described herein. The external device 330 can similarly include other circuit components.

[0043] The external device 330 and the CGM device 100 can be communicatively coupled to each other via their respective wireless transmitters 234 and 334. Such wireless communication can occur via any suitable standard-based communication protocol, such as, for example, the Bluetooth® communication protocol. In some embodiments, the wireless communication between the external device 330 and the CGM device 100 can occur via near field communication (NFC), radio frequency (RF) communication, infrared (IR) communication, optical communication, or any other suitable type of wireless communication. In some embodiments, the external device 330 and the CGM device 100 can communicate additionally or alternatively via one or more wired connections. In some embodiments, a security code that matches the security code stored in the sensor unit memory 216 may need to be input by the user into the external device 330 before communication can be initiated between the sensor unit 106 and the sensor unit 104 and / or between the CGM device 100 and the external device 330.

[0044] In some embodiments, at least a portion of the sensor information stored in the sensor unit memory 216 of the sensor unit 104 can be transferred to the memory 332 of the external device 330 via the wireless transmitter 234 of the CGM device 100 and the wireless transmitter 334 of the external device 330. The received sensor information can be processed by the processor 331 and displayed on the display 336. In some embodiments, some or all of the processing for determining the glucose level can be performed by the processor 331 instead of the transmitter unit 106 and can be displayed on the display 336. Other sensor information received by the external device 330 can be displayed on the display 336 for the user of the CGM device 100. For example, the manufacturing date and / or expiration date of the sensor 108 and / or the sensor unit 104 may be provided to the user, which can enable the user to determine whether to use the sensor unit 104 and / or the CGM 100.

[0045] In some embodiments, some or all of the process of detecting the reinsertion of sensor 108 and determining whether the reinserted sensor has exceeded its maximum removal time limit as described herein in relation to transmitter unit 106 may be performed by external device 330 rather than by transmitter unit 106. Specifically, for example, memory 332 of external device 330 may be configured to store a plurality of sensor unit identifiers corresponding to previously used CGM devices (in embodiments where sensor unit 104 and transmitter unit 106 are integrally formed), or previously used sensor units (in embodiments where sensor unit 104 is removable and detachable from transmitter unit 106, which is reusable with other sensor units). Also, in some embodiments, sensor information / data may be stored in cloud-based storage and retrieved from that storage to memory 332 by external device 330 as needed. In other embodiments, some or all of the sensor information / data may be encoded, such as by one or more barcodes attached to sensor unit 104, CGM device 100, and / or their packages, and retrieved from them to memory 332 by a scanner (not shown) of external device 330.

[0046] In embodiments where sensor unit 104 and transmitter unit 106 are integrally formed, CGM device 100 needs to be removed and replaced at the EOL of sensor 108, and the identifier (e.g., serial number) of that CGM 100 may be stored in either sensor unit memory 216 or memory 232 of transmitter unit 106 and / or its barcode. In some embodiments, CGM device 100 having integrally formed sensor unit 104 and transmitter unit 106 may have only a single memory in which the identifier may be stored (e.g., sensor unit memory 216 and memory 232 may be combined in a single memory device, which may still be referred to as sensor unit memory). The CGM identifier may be transferred to memory 332 of external device 330 in response to the insertion or reinsertion of CGM device 100 into the user's skin.

[0047] When the memory 332 of the external device 330 is executed by the processor 331, it causes the processor 331 to determine whether the identifier stored in the CGM device 100 partially matches any previously stored identifier in the memory 332, and in response to a determination that the identifier stored in the CGM device 100 matches a previously stored identifier in the memory 332, it causes the sensor 108 to determine whether it has exceeded its predetermined maximum removal time limit. It may include computer program instructions that may be part of an internally stored CGM application software program.

[0048] Figure 4 illustrates a method 400 for tracking the insertion and removal times of a sensor of a CGM device. In some embodiments, method 400 may also determine whether a reinserted sensor has exceeded the maximum removal time limit and should not be used. In still other embodiments, method 400 may determine whether a reinserted sensor meets its maximum insertion time limit and should be removed and replaced.

[0049] In processing block 402, method 400 may begin by reading or receiving, via a processor that executes computer instructions, an identifier of a sensor inserted in response to activation of the CGM. Activation of the CGM may occur in response to powering on the sensor unit, in response to a command entered by the user, in response to insertion of the sensor into the user's skin, or in response to any other suitable method of starting the CGM. The identifier may be stored, for example, in a sensor unit memory of the sensor unit, and / or may be encoded, for example, in a barcode attached to the sensor unit, the CGM device, or their packages. In some embodiments, the sensor may be a sensor 108 of a sensor unit 104 of a CGM device 100 that may be a part of the CGM system 300 (see FIGS. 1-3). The sensor unit memory may be a sensor unit memory 216, the processor may be a processor of a microcontroller 230 of the CGM device 100, or may be a processor 331 of an external device 330 communicating with the CGM device 100.

[0050] Method 400 may proceed to decision block 404 to determine whether the sensor identifier matches any identifier of a previously inserted sensor stored in a second memory. The second memory may be, for example, a memory 232 located within a transmitter unit 106 of the CGM device 100, or a memory 332 of the external device 330. In some embodiments, the second memory may include a table as shown in each of FIGS. 5A-5D.

[0051] Figures 5A, 5B, 5C, and 5D each illustrate a stored table 500A, 500B, 500C, and 500D, respectively, listing an insertion timestamp, a maximum allowable insertion time, an elapsed insertion time, a removal timestamp, and an optional re-insertion timestamp corresponding to the sensor identifier ("ID") of the currently inserted sensor and / or the previously inserted sensor. Each of the insertion, removal, and optional re-insertion timestamps may have, for example, a format of month:day:hour:minute, which may be provided by a real-time clock such as real-time clock 233 or 333 (of FIGS. 2 and 3, respectively). The maximum allowable insertion time and the elapsed insertion time may have, for example, a format of day:hour:minute. Other suitable formats may be used for each entry. In some embodiments, an additional column for a maximum allowable removal time limit may also be included.

[0052] Returning to decision block 404, if the determination is "no", this indicates that the sensor identifier is not in the second memory, the sensor is presumed to be new, and method 400 may proceed to processing block 406.

[0053] In processing block 406, the second memory is updated to include a new identifier, a corresponding insertion timestamp, and the maximum allowable insertion time of the sensor (which may be read from or received from, for example, the sensor unit memory or an attached barcode). Entries for the elapsed insertion time, removal timestamp, and optional re-insertion timestamp can each be set to zero. For example, referring to FIG. 5A, assume that the newly inserted sensor has an identifier 1234567 that does not match any of the previously stored identifiers. In response, the second memory is updated with the sensor identifier 1234567, the insertion timestamp 06:19:08:32 (in the format of month:day:hour:minute, indicating that the newly inserted sensor was inserted at 8:32 am on June 19), and the maximum insertion time 14:00:00 (in the format of day:hour:minute, indicating that the maximum allowable insertion time for this sensor is 14 days). As shown in FIG. 5A, the most recently previously inserted sensor had an identifier 8765432, and the previous sensor had an identifier 4321876.

[0054] Method 400 may then proceed to processing block 408, where data from the sensor is read and a glucose level is determined / estimated based on the sensor data, as described above.

[0055] After each sensor reading and glucose level determination / estimation (which may occur at a predetermined measurement interval, such as every 5 minutes) in processing block 408, method 400 may proceed to decision block 410 to determine whether the elapsed insertion time of the currently inserted sensor should be updated. The update may occur at any suitable time interval (e.g., every 5 minutes, every hour or more, once a day, etc.), which is preferably an even multiple of the maximum insertion time limit.

[0056] If the determination is "Yes" in decision block 410, it indicates that the elapsed insertion time of the sensor should be updated, and method 400 may proceed to process block 412 where the elapsed insertion time of the currently inserted sensor can be updated in the table stored in the second memory. Referring to FIG. 5B, for example, the currently inserted sensor 1234567 is shown to have an updated elapsed insertion time of 5 days, 14 hours, and 30 minutes in table 500B.

[0057] In an alternative embodiment, instead of periodically updating the elapsed insertion time entry in the table stored in the second memory, processing block 412 may periodically increment an elapsed insertion time counter while the sensor is inserted.

[0058] If the determination is "No" in decision block 410, it indicates that the elapsed insertion time of the sensor need not be updated, and method 400 may proceed to decision block 411 where the continuation of the sensor insertion is checked. That is, method 400 checks whether the sensor has been removed from the user's skin. The removal of the sensor may be detected, for example, via switch 235 of transmitter unit 106 (see FIG. 2), which indicates whether sensor unit 104 is connected to transmitter unit 106. The disconnection may indicate that sensor unit 104 (and sensor 108) has been removed from the user's skin. When an electrical signal from sensor 108 is no longer received by transmitter unit 106, the removal of the sensor may alternatively or additionally be detected via software, which may indicate that sensor 108 is no longer in contact with the user's interstitial fluid.

[0059] If the determination is "No" in decision block 411, it indicates that the sensor has not been removed, and method 400 returns to processing block 408 to continue glucose monitoring. (The "Yes" determination in decision block 411 is described further below.)

[0060] From processing block 412, method 400 may proceed to decision block 414 to determine whether the sensor has met its maximum insertion time limit. A "yes" determination at decision block 414 indicates that the elapsed insertion time of the sensor, indicated by either a table stored in the second memory or an elapsed insertion time counter, is equal to the sensor's maximum insertion time limit. Note that in embodiments where the update interval is not an even multiple of the maximum insertion time limit, the elapsed insertion time may exceed the sensor's maximum insertion time limit. An elapsed insertion time equal to (or exceeding) the maximum insertion time limit at decision block 414 indicates that the sensor has reached its EOL and should no longer be used. For example, referring to any of FIGS. 5A-5D, assume that sensor 4321876 is the currently inserted sensor. As shown, sensor 4321876 has a maximum insertion time of 14 days and an elapsed time of 14 days. Thus, method 400 determines that the maximum insertion time of sensor 4321876 has been met and that the sensor should no longer be used. Method 400 may then proceed to processing block 416.

[0061] At processing block 416, the operation of the sensor is stopped. That is, the processor of CGM device 100 and / or external device 330 may signal the user with an error message or audible alert via the I / O devices (e.g., display and / or sound device) of CGM device 100 and / or external device 330 that glucose monitoring has been stopped and that the sensor needs to be replaced. In some embodiments, CGM device 100 and / or external device 330 may prevent the sensor from operating and / or prevent the processing of any signals received from the sensor. Method 400 may end here until a (new or previously used) sensor is inserted into the user's skin, which returns method 400 to processing block 402.

[0062] Returning to decision block 414, a "no" determination indicates that the sensor is still available because it has not met its maximum insertion time. For example, referring to FIG. 5B, method 400 determines whether the elapsed insertion time of sensor 1234567 of 5 days, 14 hours, and 30 minutes is equal to (or exceeds) the maximum insertion time limit of 14 days for sensor 1234567. Since it is not, method 400 can proceed to decision block 411 where the continuation of the sensor insertion is checked, as described above and below.

[0063] If the determination is "yes" in decision block 411, it indicates that the sensor has been removed, and method 400 can proceed to processing block 413.

[0064] In processing block 413, method 400 can store the removal timestamp corresponding to the sensor that was just removed in a second memory. For example, referring to FIG. 5C, assume that method 400 detects the removal of sensor 1234567 at 5:47 PM on June 26. Accordingly, the removal timestamp 06:26:17:47 can be stored in table 500C corresponding to sensor 1234567.

[0065] Next, method 400 can proceed to processing block 415 where the elapsed insertion time corresponding to the removed sensor is updated based on the removal timestamp. For example, referring again to FIG. 5C, the elapsed insertion time of sensor 1234567 is updated to 07:09:15 (7 days, 9 hours, 15 minutes) based on the time difference between the removal timestamp (06:26:17:47) and the insertion timestamp (06:19:08:32).

[0066] In an alternative embodiment where an elapsed insertion time counter is used as described above in connection with processing block 412, method 400 in processing block 415 can instead store the value of the elapsed insertion time counter in the second memory in response to detecting at decision block 411 that the sensor has been removed.

[0067] Method 400 may end at processing block 415 until a sensor (new or previously used) is inserted into the user's skin, and method 400 resumes at processing block 402.

[0068] If method 400 returns to decision block 404 to determine whether the identifier of the sensor inserted into the user's skin matches any identifier of a previously inserted sensor stored in the second memory, a "yes" determination indicates that the sensor identifier matches the identifier previously stored in the second memory, and thus the sensor is presumed to have been re-inserted and reused. Method 400 may then proceed to processing block 405.

[0069] At processing block 405, method 400 may obtain a re-insertion time from a real-time clock, such as one of real-time clocks 233 or 333, and optionally store a re-insertion timestamp corresponding to the re-inserted sensor in the second memory. For example, referring to FIG. 5D, assume that sensor 1234567 is removed (e.g., to adjust or replace an adhesive used to attach the sensor unit or CGM device to the user's skin surface) and is now being re-inserted. For example, the re-insertion timestamp 06:26:18:04 indicates that the sensor was re-inserted at 6:04 PM on June 26 and may optionally be stored in table 500D corresponding to sensor 1234567.

[0070] Method 400 may here proceed to decision block 407 to determine whether the maximum removal time limit of the sensor has been exceeded. The maximum removal time limit may be stored in the memory of the sensor unit, the transmitter unit, or the cloud service, or may be encoded in a barcode, the CGM application software program, or the firmware of the CGM device. The maximum removal time limit may be established in accordance with safe medical practices regarding subcutaneous implantation and may, for example, range from a few minutes to about one hour. Other maximum removal time limits may be possible. In some embodiments, Tables 500A - 500D may include additional columns for storing the maximum removal time limit. To determine whether the maximum removal time limit of the sensor has been exceeded, Method 400 determines the elapsed removal time by calculating the time difference between the reinsertion time (obtained directly from the real - time clock or reinsertion timestamp) and the removal timestamp. For example, referring to FIG. 5D, the time difference between the reinsertion timestamp of sensor 1234567 and the removal timestamp of sensor 1234567 is 17 minutes (06:26:18:04 - 06:26:17:47).

[0071] If the determination at decision block 407 is "no", indicating that the sensor has not exceeded its maximum removal time limit and may thus be suitable for continued use, Method 400 may proceed to decision block 414 to determine whether the previously inserted sensor meets its maximum insertion time limit as described above. This may prevent the reuse of EOL sensors.

[0072] Note that a reinserted sensor that does not meet the maximum insertion time limit determined at decision block 414 may still have its use continued. In some embodiments, further updating of the elapsed insertion time at processing block 412 may be continued based on the insertion timestamp, or, in embodiments where an optional insertion timestamp is stored, may be based on that insertion timestamp.

[0073] If the determination is "yes" in decision block 407, it indicates that the sensor has exceeded its maximum removal time limit and thus should not be used, and method 400 may proceed to processing block 416 where any use of this sensor is prevented, as described above.

[0074] In an alternative embodiment, Tables 500A - 500D may each include an error detection column for indicating any error, defect, malfunction, or fault of the sensor, replaceable sensor unit, or replaceable CGM device that is detected during power - on or during its use, even though the maximum insertion time limit of the sensor has not yet been met. In these alternative embodiments, alternative decision block 414 may also determine whether any such error, defect, malfunction, or fault has occurred (as indicated in that error detection column) in addition to determining whether the maximum insertion time limit of the sensor has been met. In response to a determination that such an error, defect, malfunction, or fault has occurred or that the maximum insertion time limit of the sensor has been met, alternative method 400 will proceed to block 416 to stop the operation of the sensor. In response to a determination that an error, defect, malfunction, or fault has occurred and that the maximum insertion time limit of the sensor has not been met, alternative method 400 will proceed as described above.

[0075] Note that in some embodiments, Tables 500A - 500D may store only a few identifiers (e.g., 5 - 10) corresponding to the most recently used sensors. In some embodiments, Tables 500A - 500D may be stored in the memory 232 of the transmitter unit 106, and in other embodiments, Tables 500A - 500D may be stored in the memory 332 of the external device 330 or in a cloud - based memory.

[0076] Note also that some embodiments or portions thereof may be provided as a computer program product or software that can include a machine-readable medium storing non-transitory instructions for programming a computer processor, system, controller, or other electronic device to perform the processes or methods described herein according to one or more embodiments.

[0077] While the present disclosure is susceptible to various modifications and alternative forms, specific embodiments of the methods and apparatuses are shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the specific methods and apparatuses disclosed herein are not intended to limit the scope of the disclosure or the claims.

Claims

1. A continuous glucose monitoring (CGM) system comprising: A sensor unit having a sensor unit memory and a sensor, wherein the sensor unit memory stores an identifier internally, the sensor unit; A second memory configured to store a plurality of sensor identifiers internally; A real-time clock; A processor communicating with the second memory, the real-time clock, and the sensor unit, the processor being configured to: Read the identifier stored in the sensor unit memory; Determine whether the identifier matches any previously stored identifier in the second memory; In response to the identifier not matching any previously stored identifier in the second memory, store the identifier and an insertion timestamp in the second memory, wherein the real-time clock is used to generate the insertion timestamp; In response to the identifier matching a previously stored identifier in the second memory, obtain a reinsertion time using the real-time clock; Execute computer instructions to determine whether the sensor has exceeded a predetermined maximum removal time limit using the reinsertion time. A continuous glucose monitoring (CGM) system.

2. The CGM system according to claim 1, wherein an external device, a transmitter unit, or a cloud-based service comprises the second memory.

3. The CGM system according to claim 1, wherein an external device or a transmitter unit comprises the processor.

4. Further comprising a CGM device configured to be worn by a user, the CGM device comprising: The sensor unit; A transmitter unit electrically connected to the sensor unit, the transmitter unit comprising a wireless transmitter, the real-time clock, and a microcontroller comprising the processor. The CGM system according to claim 1.

5. The CGM system according to claim 4, wherein the sensor unit and the transmitter unit are integrally formed.

6. The CGM system according to claim 4, wherein the sensor unit is replaceable and detachable from the transmitter unit that is reusable with other sensor units.

7. The CGM system according to claim 1, wherein the processor is further configured to execute a computer instruction to stop the operation of the CGM in response to the sensor exceeding the predetermined maximum removal time limit.

8. The processor is either storing the identifier and the insertion timestamp in the second memory, or The CGM system according to claim 1, wherein the processor is further configured to execute a computer instruction to read sensor data from the sensor unit and estimate the glucose level in response to determining that the sensor has not exceeded the predetermined maximum removal time limit and does not satisfy the maximum insertion time limit.

9. The CGM system according to claim 1, wherein the processor is further configured to execute a computer instruction to periodically update the elapsed insertion time of the sensor using the real-time clock.

10. The CGM system according to claim 9, wherein the processor is further configured to execute a computer instruction to determine whether the sensor has satisfied or exceeded a predetermined maximum insertion time limit in response to the updated elapsed insertion time.

11. The CGM system according to claim 1, wherein the processor is further configured to execute a computer instruction to determine whether the sensor has been removed from the user's skin surface.

12. The CGM system according to claim 11, wherein the processor is further configured to execute a computer instruction to store a removal timestamp in the second memory in response to determining that the sensor has been removed from the user's skin surface.

13. A continuous glucose monitoring (CGM) system, comprising: a sensor configured to be inserted into the user's skin and generate an electrical signal indicating a glucose level; a first memory storing an identifier for identifying the sensor therein; a second memory configured to store a plurality of sensor identifiers therein; a real-time clock; A processor that communicates with the first and second memories and the real-time clock, the processor being configured to: Read the identifier stored in the first memory; Determine whether the identifier matches any previously stored identifier in the second memory; In response to the identifier not matching any previously stored identifier in the second memory, store the identifier and an insertion timestamp in the second memory, the real-time clock being used to generate the insertion timestamp; In response to the identifier matching a previously stored identifier in the second memory, obtain a reinsertion time using the real-time clock; Use the reinsertion time to determine whether the sensor has exceeded a predetermined maximum removal time limit; and A continuous glucose monitoring (CGM) system comprising the processor. **Claim 14** The CGM system according to claim 13, wherein the CGM device comprises the first memory and the external device comprises the second memory, the real-time clock, and the processor, or wherein the first memory comprises a sensor unit memory of a sensor unit and the sensor unit comprises the sensor. **Claim 15** The CGM system according to claim 13, wherein the first memory or the second memory is cloud-based. **Claim 16** A method of operating a continuous glucose monitoring (CGM) system, the CGM system comprising a sensor unit memory and a sensor unit having a sensor, a second memory storing computer program code, and a processor communicating with the second memory and the sensor unit, When the computer program code is executed by the processor, For the CGM system, read the identifier of the sensor from the sensor unit memory via the processor that executes computer instructions in response to activation of the CGM; For the CGM system, determine whether the identifier matches any previously stored identifier in the second memory; For the CGM system, in response to the identifier not matching any previously stored identifier in the second memory, storing the identifier and the insertion timestamp in the second memory; For the CGM system, in response to the identifier matching a previously stored identifier in the second memory, obtaining a re-insertion time; For the CGM system, using the re-insertion time to determine whether the sensor has exceeded a predetermined maximum removal time limit; For the CGM system, in response to a determination that the sensor has exceeded the predetermined maximum removal time limit, stopping the operation of the CGM. A method of operation in which the steps are executed.

17. The method of operation according to claim 16, wherein determining whether the sensor has exceeded a predetermined removal time limit includes calculating an elapsed removal time based on the re-insertion time and a previously stored removal timestamp.

18. When the computer program code is executed by the processor, storing the identifier and the insertion timestamp in the second memory, or determining that the sensor has not exceeded the predetermined maximum removal time limit and does not meet the maximum insertion time limit, in response to which sensor data is read via the sensor and a glucose level is estimated via the processor. The method of operation according to claim 16, wherein the steps are further executed.

19. When the computer program code is executed by the processor, in response to reading the sensor data and estimating the glucose level, periodically updating the elapsed insertion time of the sensor. The method of operation according to claim 18, wherein the steps are further executed.

20. When the computer program code is executed by the processor, in response to updating the elapsed insertion time, determining whether the sensor has met or exceeded a predetermined maximum insertion time limit. The method of operation according to claim 19, wherein the steps are further executed.

21. When the computer program code is executed by the processor, The method of operation according to claim 20, further comprising the step of stopping the operation of the CGM in response to a determination that the sensor has met or exceeded a predetermined maximum insertion time limit. **Claim 22** When the computer program code is executed by the processor, The method of operation according to claim 16, further comprising the step of determining whether the sensor has been removed from the user's skin surface. **Claim 23** When the computer program code is executed by the processor, The method of operation according to claim 22, further comprising the step of storing a removal timestamp in the second memory in response to a determination that the sensor has been removed from the user's skin surface. **Claim 24** When the computer program code is executed by the processor, The method of operation according to claim 23, further comprising the step of updating the elapsed insertion time of the sensor in response to storing the removal timestamp.

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