Advanced analyte sensor calibration and error detection

• US 9,848,809 B2
• Filed: 04/13/2012
• Issued: 12/26/2017
• 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.
• Primary Examiner(s): Natnithithadha, Navin
• Application Number:
  US13/446,983
• Publication Number:
  US 20120265037A1
• Time in Patent Office: 2,083 Days
• 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: 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 determining a sensitivity of a continuous analyte sensor, the method comprising:

applying a bias voltage to an analyte sensor;

applying a voltage step above the bias voltage to the analyte sensor;

measuring, using sensor electronics, a signal response of the voltage step from the analyte sensor;

determining, using the sensor electronics, a peak current of the signal response;

determining, using the sensor electronics, a sensitivity of the analyte sensor by correlating the peak current to a predetermined relationship of the peak current to sensor sensitivity, wherein the predetermined relationship is based at least in part on time of use of the analyte sensor;

receiving, using the sensor electronics, from the analyte sensor sensor data indicative of analyte concentration;

compensating, using the sensor electronics, the sensor data using the determined sensitivity of the analyte sensor;

determining, using the sensor electronics, an analyte concentration value based at least in part on the compensated sensor data; and

displaying, using a display, the determined analyte concentration value.

2. The method of claim 1, wherein correlating the peak current to the predetermined relationship comprises calculating an impedance of the analyte sensor based on the peak current and correlating the impedance of the analyte sensor to the predetermined relationship.

3. The method of claim 1, wherein the sensitivity of the sensor is a sensitivity of the analyte sensor or a temperature of the analyte sensor.

4. The method of claim 1, wherein the peak current is a difference between a magnitude of the response prior to the voltage step and a magnitude of the largest measured response resulting from the voltage step.

5. The method of claim 1, wherein the predetermined relationship is an impedance-to-sensor sensitivity relationship.

6. The method of claim 1, wherein the compensating comprises correlating a predetermined relationship of the peak current to sensor sensitivity or change in sensor sensitivity and modifying a value or values of the sensor data responsive to the correlated sensor sensitivity or change in sensor sensitivity.

7. The method of claim 6, wherein the predetermined relationship is a linear relationship over time of use of the analyte sensor.

8. The method of claim 6, wherein the predetermined relationship is a non-linear relationship over time of use of the analyte sensor.

9. The method claim 6, wherein the predetermined relationship is determined by prior testing of sensors similar to the analyte sensor.

11. The system of claim 8, wherein the sensor electronics are configured to correlate the peak current to the predetermined relationship by calculating an impedance of the analyte sensor based on the peak current and correlating the impedance of the analyte sensor to the predetermined relationship.

12. The system of claim 8, wherein the sensitivity of the analyte sensor is a sensitivity of the analyte sensor or a temperature of the analyte sensor.

13. The system of claim 8, wherein the peak current is a difference between a magnitude of the response prior to the voltage step and a magnitude of the largest measured response resulting from the voltage step.

14. The system of claim 8, wherein the predetermined relationship is an impedance-to-sensor sensitivity relationship.

15. The system of claim 8, wherein the sensor electronics are configured to compensate sensor data by correlating a predetermined relationship of the peak current to sensor sensitivity or change in sensor sensitivity and modifying a value or values of the sensor data responsive to the correlated sensor sensitivity or change in sensor sensitivity.

16. The system of claim 15, wherein the predetermined relationship is a linear relationship over time of use of the analyte sensor.

17. The system of claim 15, wherein the predetermined relationship is a non-linear relationship over time of use of the analyte sensor.

18. The system of claim 15, wherein the predetermined relationship is determined by prior testing of sensors similar to the analyte sensor.

10. A system for determining a sensitivity of a continuous analyte sensor, the system comprising:

sensor electronics configured to be operably connected to a continuous analyte sensor, the sensor electronics configured to;

apply a bias voltage to an analyte sensor;

apply a voltage step above the bias voltage to the analyte sensor;

measure a signal response of the voltage step from the analyte sensor;

determine a peak current of the signal response;

determine a sensitivity of the analyte sensor by correlating the peak current to a predetermined relationship of the peak current to sensor sensitivity, wherein the predetermined relationship is based at least in part on time of use of the analyte sensor;

receive from the analyte sensor sensor data indicative of analyte concentration;

compensate the sensor data using the determined sensitivity of the analyte sensor; and

determine an analyte concentration value based at least in part on the compensated sensor data; and

a display configured to display the determined analyte concentration value.