SYSTEMS AND METHODS FOR REPLACING SIGNAL ARTIFACTS IN A GLUCOSE SENSOR DATA STREAM

• US 20100036216A1
• Filed: 10/14/2009
• Published: 02/11/2010
• Est. Priority Date: 08/22/2003
• Status: Active Grant

• Current Assignee: DexCom Incorporated
• Original Assignee: DexCom Incorporated
• Inventors: Brauker, James H., Carr-Brendel, Victoria, Thrower, James Patrick, Kamath, Apurv U., Goode, Paul V. JR.
• Granted Patent: US 8,128,562 B2
• Time in Patent Office: Days
• US Class Current: 600/316
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 2562/0247 Pressure sensors
• CPC Class Codes: A61B 2562/0271 Thermal or temperature sensors
• CPC Class Codes: A61B 2562/08 Sensors provided with means for identification, e.g. barcodes or memory chips
• CPC Class Codes: A61B 5/0004 characterised by the type of physiological signal transmitted
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• 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 5/1473 invasive, e.g. introduced into the body by a catheter A61B5/1482 takes precedence
• 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 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7225 Details of analog processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation A61B5/30, A61B5/316 take precedence; transformers for specific applications H01F38/00; amplifiers H03F
• CPC Class Codes: A61B 5/7257 using Fourier transforms
• CPC Class Codes: A61B 5/726 using Wavelet transforms
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence
• CPC Class Codes: A61B 5/742 using visual displays A61B5/339 takes precedence
• CPC Class Codes: A61B 5/7475 User input or interface means, e.g. keyboard, pointing device, joystick

Abstract

Systems and methods for minimizing or eliminating transient non-glucose related signal noise due to non-glucose rate limiting phenomenon such as ischemia, pH changes, temperatures changes, and the like. The system monitors a data stream from a glucose sensor and detects signal artifacts that have higher amplitude than electronic or diffusion-related system noise. The system replaces some or the entire data stream continually or intermittently including signal estimation methods that particularly address transient signal artifacts. The system is also capable of detecting the severity of the signal artifacts and selectively applying one or more signal estimation algorithm factors responsive to the severity of the signal artifacts, which includes selectively applying distinct sets of parameters to a signal estimation algorithm or selectively applying distinct signal estimation algorithms.

Claims

1. In a glucose sensing system comprising a glucose sensor configured for producing an output representative of glucose concentration in a host and processing circuitry configured to process the output, a method for processing data from the output, the method comprising:

generating at least one data stream from the glucose sensor output;

calculating a data stream value range based at least in part on at least one historical data stream value, wherein the data stream value range comprises at least one limit value;

replacing at least one data stream value with at least one limit value when the data stream value is outside the limit value; and

displaying at least one of the data stream value or the limit value to a user of the glucose sensing system.

2. The method of claim 1, wherein the at least one limit value is based at least in part on physiology.

3. The method of claim 1, wherein the at least one limit value is defined by a cone of possible values extending from at least one historical data stream value.

4. The method of claim 3, wherein the cone is derived from one or both of physiologically acceptable glucose concentration rate and acceleration values.

5. The method of claim 1, wherein the at least one limit value is derived from a linear extrapolation.

6. The method of claim 1, wherein the data stream comprises a calibrated data stream of glucose concentration values.

7. The method of claim 1, comprising alerting a user of the glucose sensing system to upcoming hypoglycemic or hyperglycemic events

8. The method of claim 1, comprising detecting a signal artifact, and reducing or replacing a data stream portion containing the signal artifact with the at least one limit value.

9. A glucose sensor system for monitoring a glucose concentration in a host, the system comprising:

a continuous glucose sensor configured to produce a data stream;

a processing module configured to;

calculate a data stream value range based at least in part on at least one historical estimated data stream value, wherein the data stream value range comprises at least one limit value; and

replace the data stream value with the at least one limit value when the data stream value is outside the data stream value range; and

a display;

wherein the system is configured to display at least one of the data stream value or the limit value to a user of the glucose sensing system.

10. The system of claim 9, wherein the signal estimation module is housed in at least one of a sensor electronics housing or a receiver electronics housing.

11. The system of claim 9, wherein the processing module is configured to calculate the limit value is based at least in part on physiology.

12. The system of claim 9, wherein the processing module is configured to define the limit by a cone of possible values extending from at least one historical data stream value.

13. The system of claim 12, wherein the processing module is configured to derive the cone from one or both of physiologically acceptable glucose concentration rate and acceleration values.

14. The system of claim 9, wherein the processing module is configured to derive the limit value from a linear extrapolation.

15. The system of claim 9, wherein the processing module is configured to detect a signal artifact, and to reduce or replace a data stream portion containing the signal artifact with the at least one limit value.