Signal processing for measurement of physiological analytes

• US 7,295,867 B2
• Filed: 02/12/2003
• Issued: 11/13/2007
• Est. Priority Date: 05/13/1998
• Status: Active Grant

Abstract

A method is provided for continually or continuously measuring the concentration of target chemical analytes present in a biological system, and processing analyte-specific signals to obtain a measurement value that is closely correlated with the concentration of the target chemical analyte in the biological system. One important application of the invention involves a method for signal processing in a system for monitoring blood glucose values.

Claims

1. One or more microprocessors comprising programming to control operating a sensing device to obtain two or more active signals, wherein (i) said sensing device is in operative contact with an analyte, (ii) said sensing device obtains an active signal from the analyte, and (iii) said active signal is specifically related to analyte amount or concentration present in a biological system;

assigning a fractional weight to each of said two or more active signals based on when the respective active signals were generated with respect to one another;

determining a weighted signal that accounts for the different contributions of each of said two or more active signals and their associated fractional weights; and

performing a calibration step that converts the weighted signal to a measurement value indicative of the amount or concentration of analyte present in the biological system.

2. The one or more microprocessors of claim 1, wherein said one or more microprocessors further comprise programming to control

operating a sampling device for extracting the analyte from the biological system, wherein said sampling device is adapted for extracting the analyte across a skin or mucosal surface of said biological system.

3. A monitoring system for measuring an analyte present in a biological system, said system comprising, in operative combination:

the one or more microprocessors of claim 1; and

the sensing device.

4. A monitoring system for measuring an analyte present in a biological system, said system comprising, in operative combination:

the one or more microprocessors of claim 2;

the sampling device; and

the sensing device.

5. The monitoring system of claim 4, wherein the sampling device comprises one or more collection reservoirs for containing the extracted analyte.

6. The monitoring system of claim 5, wherein one or more collection reservoirs comprise an enzyme that reacts with the extracted analyte to produce an electrochemically detectable signal.

7. The monitoring system of claim 6, wherein the analyte is glucose and the enzyme comprises glucose oxidase.

8. The monitoring system of claim 3, wherein the analyte is glucose.

9. The monitoring system of claim 4, wherein the analyte is glucose.

10. One or more microprocessors comprising Programming to control operating a sensing device to obtain two or more active signals, wherein (i) said sensing device is in operative contact with an analyte, (ii) said sensing device obtains an active signal from the analyte, and (iii) said active signal is specifically related to analyte amount or concentration present in a biological system:

assigning a fractional weight to each of said two or more active signals;

determining a weighted signal that accounts for the different contributions of each of said two or more active signals and their associated fractional weights; and

performing a calibration step that converts the weighted signal to a measurement value indicative of the amount or concentration of analyte present in the biological system.

wherein the sensing device uses an iontophoretic current to extract the analyte from the biological system.

11. A method for measuring an analyte amount or concentration present in a biological system, said method comprising:

obtaining an active signal from the analyte, wherein said active signal is related to analyte concentration;

repeating said obtaining to provide two or more active signals;

assigning a fractional weight to each of said two or more active signals based on when the respective active signals were generated with respect to one another;

determining a weighted signal that accounts for the different contributions of each of said two or more active signals and their associated fractional weights; and

performing a calibration step which converts the weighted signal to a measurement value indicative of the amount or concentration of analyte present in the biological system.

12. The method of claim 11, wherein said weighted signal is a weighted sum of each of said two or more active signals.

13. The method of claim 11, wherein said weighted signal is a weighted average of each of said two or more active signals.

14. The method of claim 11, wherein the analyte is extracted from the biological system into a first collection reservoir to obtain an active signal in said reservoir.

15. The method of claim 14, wherein the analyte is extracted from the biological system alternatively into (i) the first collection reservoir to obtain an active signal in said first collection reservoir, and (ii) a second collection reservoir to obtain an active signal in said second collection reservoir.

16. The method of claim 15, wherein said weighted signal is a weighted sum of the two or more active signals.

17. The method of claim 16, wherein said weighted signal is determined as follows:

Y_t,ε

=aY_t1,act1+bY_t2,act2′

wherein Y_t,ε

is the summed signal at time t, a is a fractional weight for a first signal at time t1 (Y_t1,act1), and b is the fractional weight for a second active signal at time t2 (Y_t2,act2).

18. The method of claim 15, wherein said weighted signal is a weighted average of the two or more active signals.

20. The method of claim 14, wherein the first collection reservoir contains an enzyme that reacts with the extracted analyte to produce an electrochemically detectable signal.

21. The method of claim 20, wherein the analyte is glucose and the enzyme is glucose oxidase.

22. The method of claim 11, wherein the analyte is glucose.

24. The method of claim 15, wherein the second collection reservoir comprises an enzyme that reacts with the extracted analyte to produce an electrochemically detectable signal.

25. The method of claim 11, wherein an initial signal output is integrated over a sensing time period to provide the active signal.

27. The method of claim 11, wherein said fractional weights are time-dependent fractional weights.

28. The method of claim 11, wherein each active signal is subjected to a data screen which invalidates or corrects poor or incorrect signals based on a detected parameter indicative of a poor or incorrect signal.

29. The method of claim 11, wherein the calibration step entails a single-point calibration against a calibration reference value.

30. The method of claim 11, further comprising:

transdermally extracting the analyte from the biological system using a sampling device that is in operative contact with a skin or mucosal surface of said biological system before said obtaining; and

repeating said extracting and said obtaining to provide two or more active signals.

19. A method for measuring an analyte amount or concentration present in a biological system, said method comprising:

obtaining an active signal from the analyte, wherein said active signal is related to analyte concentration;

repeating said obtaining to provide two or more active signals;

assigning a fractional weight to each of said two or more active signals;

determining a weighted signal that accounts for the different contributions of each of said two or more active signals and their associated fractional weights; and

performing a calibration step which converts the weighted signal to a measurement value indicative of the amount or concentration of analyte present in the biological system,

wherein the first collection reservoir is in contact with the skin or mucosal surface of the biological system and the analyte is extracted using an iontophoretic current applied to said skin or mucosal surface.

23. A method for measuring an analyte amount or concentration present in a biological system, said method comprising:

obtaining an active signal from the analyte, wherein said active signal is related to analyte concentration;

repeating said obtaining to provide two or more active signals;

assigning a fractional weight to each of said two or more active signals;

determining a weighted signal that accounts for the different contributions of each of said two or more active signals and their associated fractional weights; and

performing a calibration step which converts the weighted signal to a measurement value indicative of the amount or concentration of analyte present in the biological system,

wherein obtaining the active signal comprises a baseline background subtraction method to remove background noise from the active signal.

26. A method for measuring an analyte amount or concentration present in a biological system, said method comprising:

obtaining an active signal from the analyte, wherein said active signal is related to analyte concentration;

repeating said obtaining to provide two or more active signals;

assigning a fractional weight to each of said two or more active signals;

determining a weighted signal that accounts for the different contributions of each of said two or more active signals and their associated fractional weights; and

performing a calibration which converts the weighted signal to a measurement value indicative of the amount or concentration of analyte present in the biological system,

wherein the calibration entails the use of a neural network algorithm that correlates each weighted signal with a measurement value indicative of the concentration of analyte present in the biological system.