Estimation of human core temperature based on heart rate system and method

• US 10,702,165 B2
• Filed: 03/04/2017
• Issued: 07/07/2020
• Est. Priority Date: 12/20/2012
• Status: Active Grant

• Current Assignee: US Department of The Army (Government of the United States of America)
• Original Assignee: US Department of The Army (Government of the United States of America)
• Inventors: Buller, Mark J.
• Primary Examiner(s): Koharski, Christopher
• Assistant Examiner(s): Steinberg, Amanda L
• Application Number:
  US15/449,943
• Publication Number:
  US 20170238811A1
• Time in Patent Office: 1,221 Days
• CPC Class Codes: A61B 5/01 Measuring temperature of body parts ; Diagnostic temperature sensing, e.g. for malignant or inflamed tissue clinical contact thermometers G01K13/20
• CPC Class Codes: A61B 5/024 Detecting, measuring or recording pulse rate or heart rate A61B5/0205, A61B5/021 take precedence
• CPC Class Codes: A61B 5/02438 with portable devices, e.g. worn by the patient
• CPC Class Codes: A61B 5/725 using specific filters therefor, e.g. Kalman or adaptive filters A61B5/316 take precedence
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence

Abstract

The invention in at least one embodiment includes a method for determining the core body temperature of a person by setting an initial core body temperature with a processor; receiving a heart rate of the person with the processor; calculating a predicted core body temperature with the processor using an extended Kalman filter based on the heart rate and the initial core body temperature; and providing the predicted core body temperature. In another embodiment, a system for performing the method.

Claims

1. A method for indirectly determining a core body temperature of a person comprising:

setting an initial core body temperature at a mobile device comprising a heart rate monitor having a plurality of electrodes, a processor, and a display;

receiving at least two heart rates of the person with the processor, where the heart rates are detected by the heart rate monitor using the plurality of electrodes attached to the person;

calculating a predicted core body temperature with the processor using an extended Kalman filter based solely on the second heart rate and the initial core body temperature; and

providing the predicted core body temperature to the display, and

wherein the initial core body temperature is set by the processor based solely on the first heart rate of the person.

2. The method according to claim 1, further comprising:

receiving an additional heart rate of the person with the processor, where the additional heart rate is detected by the heart rate monitor;

calculating a new predicted core body temperature with the processor using the extended Kalman filter based solely on the additional heart rate and the last predicted core body temperature; and

repeating the receiving additional heart rate and calculating a new predicted core body temperature at predetermined intervals.

3. The method according to claim 2, further comprising:

when the new predicted core body temperature exceeds a predetermined threshold, sending an alarm signal from said processor prior to proceeding to repeating, wherein the alarm signal triggers an alarm; and

when the new predicted core body temperature does not exceed a predetermined threshold, proceeding to repeating.

4. The method according to claim 2, further comprising obtaining the predetermined interval.

5. The method according to claim 1, further comprising recording the predicted core body temperature in memory in the mobile device;

and

wherein the mobile device is a processing hub on the person being monitored, and

the extended Kalman filter includes a time update phase and an observation update phase.

6. The method according to claim 1, wherein providing the predicted core body temperature includes transmitting the predicted core body temperature with a transmitter in the mobile device to an external device.

7. The method according to claim 1, wherein calculating a predicted core body temperature includes

calculating a preliminary core body temperature estimate;

calculating a preliminary estimate of the variance of the preliminary core body temperature estimate;

calculating an extended Kalman filter mapping function variance coefficient;

calculating a Kalman gain weighting factor based on the preliminary estimate of variance and the extended Kalman filter variance coefficient; and

calculating the predicted core body temperature using a preliminary core body temperature estimate, an error between the new heart rate and an expected heart rate given the preliminary estimate of the core body temperature.

8. The method according to claim 7, wherein calculating a predicted core body temperature further includes determining a variance of the predicted core body temperature.

9. The method according to claim 1, further comprising adjusting the extended Kalman filter based on at least one of a fitness level, an age, a maximum heart rate and a resting heart rate of the person.

10. A mobile device for indirectly determining a core body temperature of a person, the mobile device comprising:

a heart rate monitor having a plurality of electrodes capable of attachment to the person whose core body temperature is being determined;

a memory to store core body temperature data; and

a processor in communication with said heart rate monitor, said processor calculates a core body temperature using an extended Kalman filter having a plurality of constants and the extended Kalman filter having as the only inputs heart rate information from said heart rate monitor and prior core body temperature data stored in said memory.

11. The mobile device according to claim 10, further comprising a display in communication with said processor,

wherein said processor provides the calculated core body temperature to said display.

12. The mobile device according to claim 10, further comprising a transmitter for communication with an external system, said transmitter in communication with said processor.

13. The mobile device according to claim 10, further comprising a temperature sensor in communication with said processor.

14. The mobile device according to claim 10, wherein said processor includes

an initial core body temperature module for setting an initial core body temperature,

a heart rate module for obtaining heart rate information, and

a core body temperature calculator module for calculating the core body temperature, said core body temperature calculator module in communication with said initial core body temperature module and said heart rate module.

15. The mobile device according to claim 14, where said processor further includes a timer module in communication with said heart rate module and said core body temperature calculator module.

16. The mobile device according to claim 15, where said processor further includes an alarm module for triggering an alarm when the core body temperature exceeds a threshold, said alarm module in communication with said core body temperature calculator module.

17. The mobile device according to claim 16, further comprising:

a display in communication with said core body temperature calculator module;

a transmitter in communication with said core body temperature calculator module; and

a temperature sensor in communication with at least one of said timer module and said alarm module.

18. A mobile device for indirectly determining a core body temperature of a person, the mobile device comprising:

a heart rate monitor having a plurality of electrodes attached to a heart rate monitor processor configured to convert electrical signals from said electrodes into a heart rate, said plurality of electrodes configured to contact the person during use; and

a processor in communication with said heart rate monitor, said processor having program code embodied therewith, the program code executable by the processor to

set an initial core body temperature;

receive the heart rate of the person from said heart rate monitor;

calculate a predicted core body temperature using an extended Kalman filter having as its only inputs the heart rate and at least one of the initial core body temperature and the prior core body temperature; and

provide the predicted core body temperature as the core body temperature of the person.

19. The mobile device according to claim 18, further comprising:

a display in communication with said processor; and

a transmitter in communication with said processor.

20. The mobile device according to claim 18, wherein the initial core body temperature is set based on the initial heart rate of the person.