Temperature estimations in a blood glucose measuring device

• US 8,140,294 B2
• Filed: 06/05/2009
• Issued: 03/20/2012
• Est. Priority Date: 06/05/2009
• Status: Active Grant

• Current Assignee: Roche Diabetes Care Inc. (Roche Holding AG)
• Original Assignee: Roche Diagnostics Operations Incorporated (Roche Holding AG)
• Inventors: Ramey, Blaine Edward, Brown, Michael L., Pauley, James L. Jr.
• Primary Examiner(s): Barbee, Manuel L
• Application Number:
  US12/479,212
• Publication Number:
  US 20100307916A1
• Time in Patent Office: 1,019 Days
• Field of Search: 702/99, 702130-136, 600/316, 600/347, 374/1
• US Class Current: 702/131
• CPC Class Codes: A61B 2560/0252 using ambient temperature
• CPC Class Codes: A61B 2562/0295 Strip shaped analyte sensors for apparatus classified in A61B5/145 or A61B5/157
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1495 Calibrating or testing of in-vivo probes
• CPC Class Codes: A61B 5/6887 mounted on external non-worn devices, e.g. non-medical devices
• CPC Class Codes: G01K 7/42 Circuits effecting compensation of thermal inertia; Circuits for predicting the stationary value of a temperature

Abstract

Methods of estimating the temperature of a reaction site on a measurement strip in a blood glucose measuring devices are provided. In one embodiment, a method includes determining an activation initiation time, an activation duration time, a thermal magnitude and a temperature elevation for heat generating components within a device. The temperature elevation for each of the heat generating components is determined at least in part by an impulse response matrix [X_i], the activation initiation time, the activation duration time and the thermal magnitude for each of the heat generating components. The method further includes determining a total temperature elevation of the glucose measuring device by summing the temperature elevation of each of the heat generating components, reading a temperature value provided by the temperature measuring element, and determining a reaction site temperature estimation by subtracting the total temperature elevation from the temperature value provided by the temperature measuring element.

Claims

1. A method of estimating the temperature of a reaction site on a measurement strip in a blood glucose measuring device having a plurality of heat generating components and a temperature measuring element, the method comprising:

determining, by a microcontroller, an activation initiation time, when a heat generating element becomes active, an activation duration time, how long a heat generating element had been active within a sample period, and a thermal magnitude Qx at which a heat generating element had been active within the sample period for each of the heat generating components;

determining, by a microcontroller, a temperature elevation Ex for each of the heat generating components, wherein the temperature elevation Ex for each of the heat generating components is determined at least in part by an impulse response matrix [X_i] for times t₁ through t_Nx, the activation initiation time, the activation duration time and the thermal magnitude Qx for each of the heat generating components;

determining, by a microcontroller, a total temperature elevation E_total of the glucose measuring device by summing the temperature elevation Ex of each of the heat generating components;

reading, by a microcontroller, a temperature value T_sensor provided by the temperature measuring element; and

determining, by a microcontroller, a reaction site temperature estimation T_site by subtracting the total temperature elevation E_total from the temperature value T_sensor provided by the temperature measuring element.

2. The method as claimed in claim 1 further comprising preventing a blood glucose test if the reaction site temperature estimation T_site is greater than a maximum reaction site temperature T_max or less than a minimum reaction site temperature T_min.

3. The method as claimed in claim 1 wherein the impulse response matrix [X_i] for each heat generating component comprises a plurality of impulse response values X_i and the act of determining the temperature elevation Ex for each of the heat generating components further comprises summing the impulse response values X_i corresponding to the activation initiation time, the activation duration time and the thermal magnitude Qx of each heat generating component.

4. The method as claimed in claim 1 wherein determining the temperature elevation Ex for each of the heat generating components is described by:

[Ex_i]=Qx·

[U]·

[X_i];

where;

[Ex_i] is a temperature elevation matrix of a heat generating component;

Qx is the thermal magnitude of a heat generating component;

[U] is a unit impulse matrix; and

[X_i] is the impulse response matrix of a heat generating component.

5. The method as claimed in claim 4 wherein:

the method further comprises determining a temperature elevation E_k for a heat generating component k having a sequence of heat impulses of duration Δ

t and a variable magnitude [Q_k] beginning at a time N·

Δ

t such that

6. The method as claimed in claim 4 wherein the impulse response matrix [X_i] for each heat generating component comprises an (N×

1) matrix that describes a sample period of N·

Δ

t where Δ

t is the sampling interval.

7. The method as claimed in claim 6 wherein N is greater than or equal to the number of values of the impulse response matrix having the largest number of values.

8. The method as claimed in claim 1 wherein the blood glucose measuring device further comprises a mobile communications module.

9. A blood glucose measuring device comprising:

a plurality of heat generating components;

a measurement strip port operable to receive a removable measurement strip having a reaction site for receiving a blood sample;

a temperature measuring element operable to measure an internal temperature T_sensor of the blood glucose measuring device and provide an internal temperature signal that corresponds with the measured internal temperature T_sensor; and

a controller operable to receive the internal temperature signal from the temperature measuring element and to determine a temperature estimate of the reaction site T_site based on blood glucose measuring device usage by applying a dynamic thermal model, wherein;

the dynamic thermal model determines a total temperature elevation E_total based at least on part on an activation initiation time, an activation duration time and a thermal magnitude Qx of each heat generating component within a sample period; and

the controller calculates the temperature estimate of the reaction site T_site by subtracting the total temperature elevation E_total from the internal temperature T_sensor provided by the internal temperature signal.

10. The blood glucose measuring device as claimed in claim 9 wherein the dynamic thermal model determines a temperature elevation Ex for each heat generating component by summing a succession of heat impulse responses that are defined at least in part by the activation initiation time, the activation duration time and the thermal magnitude Qx of the heat generating component.

11. A blood glucose measuring device as claimed in claim 10 wherein the dynamic thermal model determines a temperature elevation Ex for each heat generating component such that:

[Ex_i]=Qx·

[U]·

[X_i];

where;

[Ex_i] is a temperature elevation matrix of a heat generating component for times t₁ through t_Nx;

Qx is the thermal magnitude of a heat generating component;

[U] is a unit impulse matrix; and

[X_i] is the impulse response matrix of a heat generating component.

12. A blood glucose measuring device as claimed in claim 9 wherein:

the dynamic thermal model determines a temperature elevation Ex for each of the heat generating components, wherein the temperature elevation Ex for each of the heat generating components is determined at least in part by an impulse response matrix [X_i] for times t₁ through t_Nx, the activation initiation time, the activation duration time and the thermal magnitude Qx for each of the heat generating components; and

the dynamic thermal model determines a total temperature elevation E_total of the glucose measuring device by summing the temperature elevation Ex of the heat generating components.

13. A blood glucose measuring device as claimed in claim 12 wherein the blood glucose measuring device further comprises a non-volatile memory configured to store the impulse response matrix [X_i] for each heat generating component such that each impulse response matrix [X_i] is accessible by the controller.

14. A blood glucose measuring device as claimed in claim 12 wherein the impulse response matrix [X_i] for each heat generating component comprises an (N×

1) matrix that describes a sample period of N·

Δ

t where Δ

t is the sampling interval.

15. A blood glucose measuring device as claimed in claim 14 wherein N is greater than or equal to the number of values of the impulse response matrix having the largest number of values.

16. A blood glucose measuring device as claimed in claim 9 wherein the controller is further operable to determine the activation initiation time, the activation duration time and the thermal magnitude Qx of each heat generating component.

17. A blood glucose measuring device as claimed in claim 9 wherein the blood glucose measuring device is implemented into a mobile communications device, a personal computer or a personal data assistant.

18. A blood glucose measuring device comprising a controller, a temperature measuring element, a measurement strip port, and a plurality of heat generating elements, wherein:

the measurement strip port is operable to receive a removable measurement strip having a reaction site positioned at an end;

the temperature measuring element is in electrical communication with the controller and is operable to measure the temperature of the blood glucose measuring device and transmit a temperature signal corresponding to the temperature of the blood glucose measuring device to the controller; and

the controller is programmed to;

determine one or more activity characteristics within a sample period for each of the heat generating components wherein;

the one or more activity characteristics comprises an initiation time when a heat generating element becomes active, how long a heat generating element had been active within a sample period, and a thermal magnitude at which a heat generating element had been active within the sample period;

calculate a total temperature elevation within the blood glucose measuring device due to the activity characteristics of the heat generating elements within the sample period; and

calculate a temperature estimation of the reaction site by subtracting the total temperature elevation from the temperature of the blood glucose measuring device corresponding to the temperature signal received from the temperature measuring element.

19. A blood glucose measuring device as claimed in claim 18 wherein:

the blood glucose measuring device further comprises a non-volatile memory;

the controller is further programmed to calculate the temperature elevation of the blood glucose measuring device by performing a linear superposition of a plurality of temperature elevations corresponding to the heat generating components; and

the controller is further programmed to determine the temperature elevation for each of the heat generating components by performing a linear superposition of a succession of heat impulse responses for each heat generating component, wherein the succession of heat impulse responses is defined by the activity characteristics for each heat generating component within the sample period.