Estimation of human core temperature based on heart rate system and method
Inventors
Assignees
United States Department of the Army
Publication Number
US-10702165-B2
Publication Date
2020-07-07
Expiration Date
2033-12-16
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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.
Core Innovation
The invention relates to a method and system for estimating a person's core body temperature based solely on heart rate data using an extended Kalman filter. The method involves setting an initial core body temperature, receiving heart rate measurements, calculating predicted core body temperature values using the extended Kalman filter based on these heart rate inputs and prior temperature estimates, and providing the predicted temperatures. This approach can continuously track core body temperature over time during warm to hot conditions, especially during exercise, using only heart rate as an input parameter.
The core problem addressed is the difficulty in non-invasively and practically measuring core body temperature in ambulatory or field settings. Traditional methods like pulmonary arterial blood temperature measurements are limited to clinical settings, while other methods such as rectal, esophageal probes, zero heat-flux sensors, or ingestible thermometer pills have limitations including impracticality, unreliability, user contraindications, or environmental interferences. Existing thermoregulatory heat transfer models necessitate multiple input parameters often unavailable or difficult to measure in real time, such as metabolic rate, environmental, and clothing characteristics. The invention provides a model that overcomes these issues by using heart rate alone, offering an accurate, practical, and real-time estimate of core body temperature suitable for heat illness risk assessment in various real-world conditions.
Claims Coverage
The patent presents ten main inventive features drawn from independent claims concerning a method and mobile device for estimating core body temperature using heart rate data processed by an extended Kalman filter.
Setting initial core body temperature based on initial heart rate
The method sets an initial core body temperature with a processor using solely the first heart rate measurement from a heart rate monitor comprising electrodes attached to the person.
Calculating predicted core body temperature with extended Kalman filter using heart rate
The processor calculates predicted core body temperature using an extended Kalman filter based solely on received heart rate data and prior core body temperature, updating predictions at predetermined intervals.
Providing predicted core body temperature via display and transmission
The predicted core body temperature is provided to a display on the mobile device and can also be transmitted to external devices.
Alarm triggering based on core temperature thresholds
An alarm signal is sent when the new predicted core body temperature exceeds a predetermined threshold, triggering an alarm before continuing measurements.
Adjusting extended Kalman filter based on individual physiological parameters
The extended Kalman filter can be adjusted based on the person's fitness level, age, maximum heart rate, and resting heart rate for personalized estimations.
Mobile device with integrated heart rate monitor and processor using extended Kalman filter
A mobile device including a heart rate monitor with electrodes, a memory storing core body temperature data, and a processor computing core temperature solely from heart rate input and prior core temperature using an extended Kalman filter.
Modules within processor for comprehensive functionality
The processor comprises modules for setting initial core body temperature, obtaining heart rate information, calculating core temperature, timing intervals, and alarming upon threshold exceedance.
Modular components including display, transmitter, and temperature sensor
The mobile device can include a display, a transmitter for external communication, and a temperature sensor integrated with processing, timing, or alarm modules.
Calculation steps involving preliminary estimates and Kalman gain weighting
Core temperature calculation involves a multi-step process with preliminary core temperature estimates, variance calculations, mapping function variance coefficients, Kalman gain factors, and final variance determination.
Program code embodied in processor for full core temperature estimation method
The processor is programmed to execute code that sets initial core body temperature, receives heart rate data, computes predicted core temperature using an extended Kalman filter with heart rate and initial/prior temperature as only inputs, and provides the estimated temperature.
The claims cover a method and a mobile device that use heart rate readings from electrodes and a processor implementing an extended Kalman filter to iteratively and accurately estimate a person's core body temperature, enabling real-time monitoring with alarm capability and options for personalizing the algorithm based on physiological factors.
Stated Advantages
Provides accurate core body temperature estimates using only heart rate without requiring invasive or multi-parameter inputs.
Offers practical, real-time heat illness risk assessment suitable for ambulatory and field settings.
The method and device can be personalized to individual parameters such as fitness, age, and heart rate characteristics to improve accuracy.
The system can trigger alarms when predicted core temperature exceeds thresholds, enhancing safety.
The approach demonstrates similar accuracy and limits of agreement compared to clinical core temperature measurements like rectal and esophageal probes.
Documented Applications
Non-invasive real-time monitoring of core body temperature during exercise and strenuous work in warm to hot environments.
Use in military field training and operations under various environmental and clothing conditions to assess heat strain.
Continuous physiological monitoring for safety assessment in occupational and athletic settings.
Integration into wearable devices such as heart rate monitors or processing hubs worn by individuals.
Transmission of predicted core body temperature data to external systems for health management and alerts.
Use of alarm signals to warn individuals or monitoring personnel of potential overheating and heat illness risk.
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