Methods And Systems For Processing Glucose Data Measured From A Person Having Diabetes

• US 20110184267A1
• Filed: 01/26/2010
• Published: 07/28/2011
• Est. Priority Date: 01/26/2010
• Status: Active Grant

• Current Assignee: Roche Diabetes Care Inc. (Roche Holding AG)
• Original Assignee: Roche Diagnostics Operations Incorporated (Roche Holding AG)
• Inventors: Duke, David L., Weinert, Stefan, Soni, Abhishek S.
• Granted Patent: US 8,843,321 B2
• Time in Patent Office: Days
• US Class Current: 600/365
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence
• CPC Class Codes: A61B 5/725 using specific filters therefor, e.g. Kalman or adaptive filters A61B5/316 take precedence

Abstract

Methods and systems are disclosed for estimating a glucose level of a person having diabetes comprises. One method may comprise: receiving into a computing device a plurality of measured glucose results from a glucose sensor coupled to the person; using the computing device to analyze the plurality of measured glucose results with a probability analysis tool configured to determine a probability of glucose sensor accuracy based on the plurality of measured glucose results; and using the computing device to estimate a glucose level of the person with a recursive filter configured to estimate the glucose level based on the plurality of measured glucose results weighted with the probability of glucose sensor accuracy.

Claims

1. A method for estimating a glucose level of a person having diabetes, the method comprising:

receiving into a computing device a plurality of measured glucose results from a glucose sensor coupled to the person;

using the computing device to analyze the plurality of measured glucose results with a probability analysis tool configured to determine a probability of glucose sensor accuracy P_A based on the plurality of measured glucose results; and

using the computing device to estimate the glucose level of the person with a recursive filter configured to estimate the glucose level based on the plurality of measured glucose results weighted with the probability of glucose sensor accuracy P_A.

2. The method of claim 1, wherein the computing device comprises a blood glucose meter, an insulin pump, a microprocessor coupled to the glucose sensor, a cellular phone, a smart phone, a personal digital assistant, a personal computer, or a computer server.

3. The method of claim 1, wherein the glucose sensor comprises a continuous glucose monitoring system physically coupled to the person having diabetes and configured to automatically measure the glucose level of the person.

4. The method of claim 1, wherein the plurality of measured glucose results comprises periodic glucose measurements taken approximately every one minute.

5. The method of claim 1, wherein the probability analysis tool is configured to determine a probability of glucose sensor accuracy P_A further based on at least one of:

when the person eats a meal;

when the person exercises;

when insulin is delivered to the person; and

one or more measurements from an impedance measuring device coupled to the person having diabetes and configured to measure impedance in the person.

6. The method of claim 1, wherein the probability analysis tool comprises a hidden Markov model, wherein:

the hidden Markov model has two states;

a first state S_A indicating the glucose sensor is accurate, and

a second state S_I indicating the glucose sensor is inaccurate; and

the hidden Markov model is configured to determine the probability of glucose sensor accuracy P_A, based on a state of the hidden Markov model and the plurality of measured glucose results.

7. The method of claim 6, wherein probability of the glucose sensor being in the second state S_I is based on a most-recent measured glucose result, a most-recent change in the plurality of measured glucose results, or a combination thereof.

8. The method of claim 6, wherein probability of the hidden Markov model transitioning from the first state S_A to second the state S_I is

9. The method of claim 6, wherein probability of the hidden Markov model remaining in the second state S_I is

10. The method of claim 6, wherein the probability of glucose sensor accuracy P_A is

1−

[(P<sub>A→

I</sub>×

S_A)+(P<sub>I→

I</sub>×

S_I)], wherein

S_A=1 when the hidden Markov model is in the first state S_A and S_A=0 otherwise,

S_I=1 when the hidden Markov model is in the second state S_I and S_I=0 otherwise,

P<sub>A→

I</sub> is a probability of transitioning from the first state S_A to the second state S_I, and

P<sub>I→

I</sub> is a probability of remaining in the second state S_I when in the second state S_I.

11. The method of claim 1, wherein the recursive filter is a Kalman filter or an Extended Kalman filter.

12. The method of claim 11 further comprising using the computing device to predict a future glucose level of the person with the Kalman filter or the Extended Kalman filter, wherein:

the Kalman filter or the Extended Kalman filter comprises a prediction step and a measurement step; and

the prediction step is performed one or more times in order to predict the future glucose level of the person.

13. The method of claim 11, wherein the Kalman filter or the Extended Kalman filter comprises a state vector, x_k=[g ġ

{umlaut over (g)}]^T, where k represents a kth sample of the state vector, g represents the estimated glucose level of the person, ġ

represents a first derivative of g, and {umlaut over (g)} represents a second derivative of g.

14. The method of claim 13, wherein using the computing device to estimate the glucose level of the person comprises determining the state vector

x_k={circumflex over (x)}_k+K_k(z_k−

H{circumflex over (x)}_k)P_A,

where

15. The method of claim 14, wherein the Kalman gain K_k is based on a measurement uncertainty R_k such that the measurement uncertainty R_k is variable and is based on the probability of sensor accuracy.

16. The method of claim 15, wherein the measurement uncertainty R_k is:

17. The method of claim 1, wherein the recursive filter is configured to estimate the glucose level of the person further based on at least one of:

when the person eats a meal;

when the person exercises; and

when insulin is delivered to the person.

18. The method of claim 1 further comprising using the computing device to predict a future glucose level of the person with a regression analysis tool configured to predict the future glucose level based on the estimated glucose level of the person from the recursive filter.

19. The method of claim 18, wherein the regression analysis tool comprises a Gaussian process regression analysis.

20. The method of claim 19, wherein the Gaussian process regression analysis comprises a training algorithm configured to learn one or more characteristics of the person related to the glucose level of the person.

21. The method of claim 18 further comprising determining an uncertainty of the predicted future glucose level of the person.

22. The method of claim 18, wherein the regression analysis tool is configured to predict the future glucose level of the person further based on at least one of:

when the person eats a meal;

when the person exercises; and

when insulin is delivered to the person.

23. A computer-readable medium having computer-executable instructions for performing a method for estimating a glucose level of a person having diabetes, the method comprising:

receiving into a computer a plurality of measured glucose results from a glucose sensor coupled to the person;

using the computer to analyze the plurality of measured glucose results with a probability analysis tool configured to determine a probability of glucose sensor accuracy P_A based on the plurality of measured glucose results; and

using the computer to estimate the glucose level of the person with a recursive filter configured to estimate the glucose level based on the plurality of measured glucose results weighted with the probability of glucose sensor accuracy P_A.

24. The computer-readable medium of claim 23, wherein the computer comprises a blood glucose meter, an insulin pump, a microprocessor coupled to the glucose sensor, a cellular phone, a smart phone, a personal digital assistant, a personal computer, or a computer server.

25. The computer-readable medium of claim 23, wherein the glucose sensor comprises a continuous glucose monitoring system physically coupled to the person having diabetes and configured to automatically measure the glucose level of the person.

26. The computer-readable medium of claim 23, wherein the plurality of measured glucose results comprises periodic glucose measurements taken approximately every one minute.

27. The computer-readable medium of claim 23, wherein the probability analysis tool is configured to determine a probability of glucose sensor accuracy P_A further based on at least one of:

when the person eats a meal;

when the person exercises;

when insulin is delivered to the person; and

one or more measurements from an impedance measuring device coupled to the person having diabetes and configured to measure impedance in the person.

28. The computer-readable medium of claim 23, wherein the probability analysis tool comprises a hidden Markov model, wherein:

the hidden Markov model has two states;

a first state S_A indicating the glucose sensor is accurate, and

a second state S_I indicating the glucose sensor is inaccurate; and

the hidden Markov model is configured to determine the probability of glucose sensor accuracy P_A, based on a state of the hidden Markov model and the plurality of measured glucose results.

29. The computer-readable medium of claim 28, wherein probability of the glucose sensor being in S_I is based on a most-recent measured glucose result, a most-recent change in the plurality of measured glucose results, or a combination thereof.

30. The computer-readable medium of claim 28, wherein probability of transitioning from the first state S_A to the second state S_I is

31. The computer-readable medium of claim 28, wherein probability of remaining in the second state S_I is

32. The computer-readable medium of claim 28, wherein the probability of glucose sensor accuracy P_A is

1−

[(P<sub>A→

I</sub>×

S_A)+(P<sub>I→

I</sub>×

S_I)], wherein

S_A=1 when the hidden Markov model is in the first state S_A and S_A=0 otherwise,

S₁=1 when the hidden Markov model is in the second state S_I and S_I=0 otherwise,

P<sub>A→

I</sub> is a probability of transitioning from the first state S_A to the second state S_I, and

P<sub>I→

I</sub> is a probability of remaining in the second state S_I when in the second state S_I.

33. The computer-readable medium of claim 23, wherein the recursive filter is a Kalman filter or an Extended Kalman filter.

34. The computer-readable medium of claim 33, wherein the method further comprises using the computer to predict a future glucose level of the person with the Kalman filter or the Extended Kalman filter, wherein:

the Kalman filter or the Extended Kalman filter comprises a prediction step and a measurement step; and

the prediction step is performed one or more times in order to predict the future glucose level of the person.

35. The computer-readable medium of claim 33, wherein the Kalman filter or the Extended Kalman filter comprises a state vector, x_k=[g ġ

{umlaut over (g)}]^T, where k represents a kth sample of the state vector, g represents the estimated glucose level of the person, ġ

represents a first derivative of g, and {umlaut over (g)} represents a second derivative of g.

36. The computer-readable medium of claim 35, wherein using the computer to estimate the glucose level of the person comprises determining the state vector

x_k={circumflex over (x)}_k+K_k(z_k−

H{circumflex over (x)}_k)P_A,

where

37. The computer-readable medium of claim 36, wherein the Kalman gain K_k is based on a measurement uncertainty R_k such that the measurement uncertainty R_k is variable and is based on the probability of sensor accuracy.

38. The computer-readable medium of claim 37, wherein the measurement uncertainty R_k is:

39. The computer-readable medium of claim 23, wherein the recursive filter is configured to estimate the glucose level of the person further based on at least one of:

when the person eats a meal;

when the person exercises; and

when insulin is delivered to the person.

40. The computer-readable medium of claim 23, wherein the method further comprises using the computer to predict a future glucose level of the person with a regression analysis tool configured to predict the future glucose level based on the estimated glucose level of the person from the recursive filter.

41. The computer-readable medium of claim 40, wherein the regression analysis tool comprises a Gaussian process regression analysis.

42. The computer-readable medium of claim 41, wherein the Gaussian process regression analysis comprises a training algorithm configured to learn one or more characteristics of the person related to the glucose level of the person.

43. The computer-readable medium of claim 40, wherein the method further comprises determining an uncertainty of the predicted future glucose level of the person.

44. The computer-readable medium of claim 40, wherein the regression analysis tool is configured to predict the future glucose level of the person further based on at least one of:

when the person eats a meal;

when the person exercises; and

when insulin is delivered to the person.

45. An apparatus for estimating a glucose level of a person having diabetes, the apparatus comprising a microcontroller, an input device, and a display, wherein:

the microcontroller is electrically coupled to the input device configured to receive a plurality of measured glucose results from a glucose sensor coupled to the person, wherein the microcontroller is configured to receive the plurality of measured glucose results from the input device;

the microcontroller is configured to analyze the plurality of measured glucose results with a probability analysis tool configured to determine a probability of glucose sensor accuracy P_A based on the plurality of measured glucose results;

the microcontroller is configured to estimate a glucose level of the person with a recursive filter configured to estimate the glucose level based on the plurality of measured glucose results weighted with the probability of glucose sensor accuracy P_A; and

the microcontroller is electrically coupled to the display such that the microcontroller is configured to transmit to the display information related to the estimate of the glucose level of the person.

46. The apparatus of claim 45, wherein the apparatus comprises a blood glucose meter, an insulin pump, a continuous glucose monitoring system, a cellular phone, a smart phone, a personal digital assistant, a personal computer, or a computer server.

47. The apparatus of claim 45, wherein the glucose sensor comprises a continuous glucose monitoring system physically coupled to the person having diabetes and configured to automatically measure a glucose level of the person.

48. The apparatus of claim 45, wherein the plurality of measured glucose results comprises periodic glucose measurements taken approximately every one minute.

49. The apparatus of claim 45, wherein the probability analysis tool is configured to determine a probability of glucose sensor accuracy P_A further based on at least one of:

when the person eats a meal;

when the person exercises;

when insulin is delivered to the person; and

one or more measurements from an impedance measuring device coupled to the person having diabetes and configured to measure impedance in the person.

50. The apparatus of claim 45, wherein the probability analysis tool comprises a hidden Markov model, wherein:

the hidden Markov model has two states;

a first state S_A indicating the glucose sensor is accurate, and

a second state S_I indicating the glucose sensor is inaccurate; and

the hidden Markov model is configured to determine the probability of glucose sensor accuracy P_A, based on a state of the hidden Markov model and the plurality of measured glucose results.

51. The apparatus of claim 50, wherein probability of the glucose sensor being in the second state S_I is based on a most-recent measured glucose result, a most-recent change in the plurality of measured glucose results, or a combination thereof.

52. The apparatus of claim 50, wherein probability of the hidden Markov model transitioning from the first state S_A to the second state S_I is

53. The apparatus of claim 50, wherein probability of the hidden Markov model remaining in the second state S_I is

54. The apparatus of claim 50, wherein probability of glucose sensor accuracy P_A is

1−

[(P<sub>A→

I</sub>×

S_A)+(P<sub>I→

I</sub>×

S₁)], wherein

S_A=1 when the hidden Markov model is in the first state S_A and S_A=0 otherwise,

S_I=1 when the hidden Markov model is in the second state S_I and S_I=0 otherwise,

P<sub>A→

I</sub> is a probability of transitioning from the first state S_A to the second state S_I, and

P<sub>I→

I</sub> is a probability of remaining in the second state S_I when in the second state S_I.

55. The apparatus of claim 45, wherein the recursive filter is a Kalman filter or an Extended Kalman filter.

56. The apparatus of claim 55, wherein the microcontroller is further configured to predict a future glucose level of the person with the Kalman filter or the Extended Kalman filter, wherein:

the Kalman filter or the Extended Kalman filter comprises a prediction step and a measurement step; and

the prediction step is performed one or more times in order to predict the future glucose level of the person.

57. The apparatus of claim 55, wherein the Kalman filter or the Extended Kalman filter comprises a state vector, x_k=[g ġ

{umlaut over (g)}]^T, where k represents a kth sample of the state vector, g represents the estimated glucose level of the person, ġ

represents a first derivative of g, and {umlaut over (g)} represents a second derivative of g.

58. The apparatus of claim 57, wherein the microcontroller is configured to estimate the glucose level of the person by determining the state vector

x_k={circumflex over (x)}_k+K_k(z_k−

H{circumflex over (x)}_k)P_A,

where

59. The apparatus of claim 58, wherein the Kalman gain K_k is based on a measurement uncertainty R_k such that the measurement uncertainty R_k is variable and is based on the probability of sensor accuracy.

60. The apparatus of claim 59, wherein the measurement uncertainty R_k is:

61. The apparatus of claim 45, wherein the recursive filter is configured to estimate the glucose level of the person further based on at least one of:

when the person eats a meal;

when the person exercises; and

when insulin is delivered to the person.

62. The apparatus of claim 45, wherein the microcontroller is further configured to predict a future glucose level of the person with a regression analysis tool configured to predict the future glucose level based on the estimated glucose level of the person from the recursive filter.

63. The apparatus of claim 62, wherein the regression analysis tool comprises a Gaussian process regression analysis.

64. The apparatus of claim 63, wherein the Gaussian process regression analysis comprises a training algorithm configured to learn one or more characteristics of the person related to the glucose level of the person.

65. The apparatus of claim 62, wherein the regression analysis tool is configured to determine an uncertainty of the predicted future glucose level of the person.

66. The apparatus of claim 62, wherein the regression analysis tool is configured to predict the future glucose level of the person further based on at least one of:

when the person eats a meal;

when the person exercises; and

when insulin is delivered to the person.