ADVANCED ANALYTE SENSOR CALIBRATION AND ERROR DETECTION

• US 20120265035A1
• Filed: 04/13/2012
• Published: 10/18/2012
• Est. Priority Date: 04/15/2011
• Status: Active Grant

• Current Assignee: DexCom Incorporated
• Original Assignee: DexCom Incorporated
• Inventors: Bohm, Sebastian, Rong, Daiting, Simpson, Peter C.
• Granted Patent: US 9,801,575 B2
• Time in Patent Office: Days
• US Class Current: 600/309
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 2560/0276 Determining malfunction
• CPC Class Codes: A61B 2560/04 Constructional details of apparatus
• CPC Class Codes: A61B 2562/085 combined with means for recording calibration data
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/14503 invasive, e.g. introduced into the body by a catheter or needle or using implanted sensors A61B5/1459, A61B5/1464, A61B5/1473, A61B5/1482, A61B5/14865 take precedence
• CPC Class Codes: A61B 5/1451 for interstitial fluid
• CPC Class Codes: A61B 5/14517 for sweat
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/14535 for measuring haematocrit
• CPC Class Codes: A61B 5/14539 for measuring pH
• CPC Class Codes: A61B 5/14542 for measuring blood gases A61B5/14551 takes precedence
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61B 5/1473 invasive, e.g. introduced into the body by a catheter A61B5/1482 takes precedence
• CPC Class Codes: A61B 5/14735 comprising an immobilised reagent
• CPC Class Codes: A61B 5/1486 using enzyme electrodes, e.g. with immobilised oxidase
• CPC Class Codes: A61B 5/14865 invasive, e.g. introduced into the body by a catheter or needle or using implanted sensors
• CPC Class Codes: A61B 5/1495 Calibrating or testing of in-vivo probes
• CPC Class Codes: A61B 5/15003 for venous or arterial blood
• CPC Class Codes: A61B 5/150992 Blood sampling from a fluid line external to a patient, such as a catheter line, combined with an infusion line; blood sampling from indwelling needle sets, e.g. sealable ports, luer couplings, valves tubing connectors and couplings A61M39/00
• CPC Class Codes: A61B 5/155 : Devices specially adapted for continuous or multiple sampling, e.g. at predetermined intervals devices loaded with multiple lancets simultaneously A61B5/15146
• CPC Class Codes: A61B 5/157 : Devices characterised by integrated means for measuring characteristics of blood
• CPC Class Codes: A61B 5/412 : Detecting or monitoring sepsis
• CPC Class Codes: A61B 5/4839 : combined with drug delivery
• CPC Class Codes: A61B 5/6848 : Needles
• CPC Class Codes: A61B 5/6849 : in combination with a needle set
• CPC Class Codes: A61B 5/6866 : Extracorporeal blood circuits, e.g. dialysis circuits
• CPC Class Codes: A61B 5/7257 : using Fourier transforms
• CPC Class Codes: A61B 5/7267 : involving training the classification device
• CPC Class Codes: A61B 5/7275 : Determining trends in physiological measurement data; Predicting development of a medical condition based on physiological measurements, e.g. determining a risk factor
• CPC Class Codes: A61B 5/743 : Displaying an image simultaneously with additional graphical information, e.g. symbols, charts, function plots
• CPC Class Codes: A61M 2005/14296 : Pharmacokinetic models
• CPC Class Codes: A61M 2230/201 : Glucose concentration
• CPC Class Codes: A61M 5/14 : Infusion devices, e.g. infusing by gravity; Blood infusion; Accessories therefor
• CPC Class Codes: A61M 5/16804 : Flow controllers
• CPC Class Codes: A61M 5/1723 : using feedback of body parameters, e.g. blood-sugar, pressure measurement of body parameters A61B5/00
• CPC Class Codes: C12Q 1/001 : Enzyme electrodes
• CPC Class Codes: C12Q 1/006 : for glucose
• CPC Class Codes: G01D 18/00 : Testing or calibrating apparatus or arrangements provided for in groups G01D1/00 - G01D15/00
• CPC Class Codes: G01N 27/026 : Dielectric impedance spectroscopy electrochemical impedance spectroscopy for measuring corrosion G01N17/02
• CPC Class Codes: G01N 27/3274 : Corrective measures, e.g. error detection, compensation for temperature or hematocrit, calibration coding of calibration information G01N33/48771
• CPC Class Codes: G01N 33/49 : Blood chemical methods for determining blood cell populations G01N33/5094; chemical analysis of blood groups or blood types G01N33/80
• CPC Class Codes: G16H 10/40 : for data related to laboratory analysis, e.g. patient specimen analysis
• CPC Class Codes: G16H 20/17 : delivered via infusion or injection
• CPC Class Codes: G16H 40/40 : for the management of medical equipment or devices, e.g. scheduling maintenance or upgrades
• CPC Class Codes: G16H 40/63 : for local operation
• CPC Class Codes: H05K 999/00 : dummy group
• CPC Class Codes: H05K 999/99 : dummy group
• CPC Class Codes: Y02A 90/10 : Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation

Abstract

Systems and methods for processing sensor data and self-calibration are provided. In some embodiments, systems and methods are provided which are capable of calibrating a continuous analyte sensor based on an initial sensitivity, and then continuously performing self-calibration without using, or with reduced use of, reference measurements. In certain embodiments, a sensitivity of the analyte sensor is determined by applying an estimative algorithm that is a function of certain parameters. Also described herein are systems and methods for determining a property of an analyte sensor using a stimulus signal. The sensor property can be used to compensate sensor data for sensitivity drift, or determine another property associated with the sensor, such as temperature, sensor membrane damage, moisture ingress in sensor electronics, and scaling factors.

Claims

1. A method for calibrating an analyte sensor, the method comprising:

applying a time-varying signal to the analyte sensor;

measuring a signal response to the applied signal;

determining, using sensor electronics, a sensitivity of the analyte sensor, the determining comprising correlating at least one property of the signal response to a predetermined sensor sensitivity profile; and

generating, using sensor electronics, estimated analyte concentration values using the determined sensitivity and sensor data generated by the analyte sensor.

2. The method of claim 1, wherein the sensitivity profile comprises varying sensitivity values over time since implantation of the sensor.

3. The method of claim 1, wherein the predetermined sensitivity profile comprises a plurality of sensitivity values.

4. The method of claim 1, wherein the predetermined sensitivity profile is based on sensor sensitivity data generated from studying sensitivity changes of analyte sensors similar to the analyte sensor.

5. The method of claim 1, further comprising applying a bias voltage to the sensor, wherein the time-varying signal comprises a step voltage above the bias voltage or a sine wave overlaying a voltage bias voltage.

6. The method of claim 1, wherein the determining further comprises calculating an impedance value based on the measured signal response and correlating the impedance value to a sensitivity value of the predetermined sensitivity profile.

7. The method of claim 1, further comprising applying a DC bias voltage to the sensor to generate sensor data, wherein the estimating analyte concentration values includes generating corrected sensor data using the determined sensitivity.

8. The method of claim 7, further comprising applying a conversion function to the corrected sensor data to generate the estimated analyte concentration values.

9. The method of claim 7, further comprising forming a conversion function based at least in part of the determined sensitivity, and wherein the conversion function is applied to the sensor data to generate the estimated analyte concentration values.

10. The method of claim 1, wherein the property is a peak current value of the signal response.

11. The method of claim 1, wherein the determining further comprises using at least one of performing a Fast Fourier Transform on the signal response data, integrating at least a portion of a curve of the signal response, and determining a peak current of the signal response.

12. The method of claim 11, further comprising generating estimated analyte concentration values using the selected sensitivity profile.

13. The method of claim 1, wherein the determining further comprises selecting the predetermined sensitivity profile based on the determined sensor property from a plurality of different predetermined sensitivity profiles.

14. The method of claim 13, wherein the selecting includes performing a data association analysis to determine a correlation between the determined sensor property and each of the plurality of different predetermined sensitivity profiles and wherein the selected predetermined sensitivity profile has the highest correlation.

15. The method of claim 13, further comprising generating estimated analyte concentration values using the selected sensitivity profile.

16. The method of claim 15, further comprising determining a second sensitivity value using the selected sensitivity profile, wherein a first set of estimated analyte concentration values is generated using the determined sensitivity value and sensor data associated with a first time period, and wherein a second set of concentration values is generated using the second sensitivity value and sensor data associated with a second time period.

17. A system for measuring an analyte, the system comprising sensor electronics configured to be operably connected to a continuous analyte sensor, the sensor electronics configured to:

apply a time-varying signal to the analyte sensor;

measure a signal response to the applied signal;

determine a sensitivity of the analyte sensor, the determining comprising correlating at least one property of the signal response to a predetermined sensor sensitivity profile; and

generate estimated analyte concentration values using the determined sensitivity and sensor data generated by the analyte sensor.

18. The system of claim 17, wherein the sensitivity profile comprises varying sensitivity values over time since implantation of the sensor.

19. The system of claim 17, wherein the predetermined sensitivity profile comprises a plurality of sensitivity values.

20. The system of claim 17, wherein the predetermined sensitivity profile is based on sensor sensitivity data generated from studying sensitivity changes of analyte sensors similar to the analyte sensor.

21. The system of claim 17, wherein the sensor electronics are further configured to apply a bias voltage to the sensor, wherein the time-varying signal comprises a step voltage above the bias voltage or a sine wave overlaying a voltage bias voltage.

22. The system of claim 17, wherein the determining further comprises calculating an impedance value based on the measured signal response and correlating the impedance value to a sensitivity value of the predetermined sensitivity profile.

23. The system of claim 17, wherein the sensor electronics are further configured to apply a DC bias voltage to the sensor to generate sensor data, wherein the estimating analyte concentration values includes generating corrected sensor data using the determined sensitivity.

24. The system of claim 17, wherein the sensor electronics are further configured to apply a conversion function to the corrected sensor data to generate the estimated analyte concentration values.

25. The system of claim 17, wherein the sensor electronics are further configured to form a conversion function based at least in part of the determined sensitivity, and wherein the conversion function is applied to the sensor data to generate the estimated analyte concentration values.

26. The system of claim 17, wherein the property is a peak current value of the signal response.

27. The system of claim 17, wherein the determining further comprises using at least one of performing a Fast Fourier Transform on the signal response data, integrating at least a portion of a curve of the signal response, and determining a peak current of the signal response.

28. The system of claim 27, wherein the sensor electronics are further configured to generate estimated analyte concentration values using the selected sensitivity profile.

29. The system of claim 17, wherein the determining further comprises selecting the predetermined sensitivity profile based on the determined sensor property from a plurality of different predetermined sensitivity profiles.

30. The system of claim 29, wherein the selecting includes performing a data association analysis to determine a correlation between the determined sensor property and each of the plurality of different predetermined sensitivity profiles and wherein the selected predetermined sensitivity profile has the highest correlation.

31. The system of claim 29, wherein the system electronics are further configured to generate estimated analyte concentration values using the selected sensitivity profile.

32. The system of claim 31, wherein the system electronics are further configured to determine a second sensitivity value using the selected sensitivity profile, wherein a first set of estimated analyte concentration values is generated using the determined sensitivity value and sensor data associated with a first time period, and wherein a second set of concentration values is generated using the second sensitivity value and sensor data associated with a second time period.

33. The system of claim 17, wherein the sensor electronics comprise a processor module, the processor module comprising instructions stored in computer memory, wherein the instructions, when executed by the processor module, cause the sensor electronics to perform the applying, the measuring, the determining and the generating.