Non-Invasive Core Temperature Estimation With Extended Kalman Filtering

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing methods for estimating core body temperature in ambulatory settings are impractical, unreliable, or require invasive procedures, and existing heart rate-based models fail to accurately predict core body temperature at lower temperatures.

Innovation Solution

A sigmoid equation within an extended Kalman filter model uses heart rate to estimate core body temperature, adjusting for factors like age, fitness, and environmental conditions, providing accurate predictions across a range of temperatures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If traditional invasive methods (rectal/esophageal probes) are used to measure core body temperature, then measurement precision is improved, but ease of operation and adaptability to ambulatory settings deteriorates

Engineering Contradiction:

Improvecore body temperature measurement precisionVSAvoidambulatory measurement ease

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The patent replaces invasive mechanical probe insertion with a mathematical modeling approach that uses readily available physiological parameters (heart rate, skin temperature) to estimate core body temperature. The extended Kalman filter model substitutes direct physical measurement with computational estimation, eliminating the need for rectal or esophageal probes while maintaining measurement precision.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces mathematical models (thermoregulatory heat transfer models combined with extended Kalman filter) as intermediaries between easily measurable parameters (heart rate, skin temperature) and the difficult-to-measure core body temperature. These models act as mediators that translate accessible physiological signals into accurate core temperature estimates without direct invasion.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If non-invasive methods (axillary/tympanic temperature) are used to estimate core body temperature, then ease of operation is improved, but measurement precision deteriorates

Engineering Contradiction:

Improvenon-invasive measurement easeVSAvoidcore body temperature estimation precision

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent merges multiple easily measurable parameters (heart rate, skin temperature, environmental conditions) into a unified computational model that estimates core body temperature. By combining these non-invasive measurements through the extended Kalman filter framework, the system achieves measurement precision comparable to invasive methods while maintaining the ease of non-invasive operation.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent transforms the approach by changing from direct temperature measurement to indirect estimation through physiological parameter relationships. The system uses heart rate and skin temperature as input parameters, processes them through thermoregulatory models, and outputs core body temperature estimates, thereby achieving high precision through parameter transformation rather than direct measurement.

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If existing heart rate-based models are used to predict core body temperature, then ease of operation is improved, but measurement precision deteriorates at lower temperatures

Engineering Contradiction:

Improveheart rate-based prediction easeVSAvoidcore body temperature prediction precision at lower temperatures

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent implements a dynamic extended Kalman filter model that adapts to changing physiological conditions in real-time. The model continuously updates its estimates based on incoming heart rate data and adjusts its predictions according to the current thermal state, thereby maintaining high precision across the full temperature range including lower temperatures where static models fail.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent incorporates feedback mechanisms where the model continuously compares predicted core temperature with observed physiological responses and adjusts its predictions accordingly. The extended Kalman filter uses feedback from heart rate measurements to refine temperature estimates, improving accuracy at lower temperatures by learning from the relationship between heart rate and temperature across different physiological states.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS12426839B2Method for estimating core body temperature

Publication Date: 2025.09.30 UNITED STATES OF AMERICA THE AS REPRESENTED BY THE SEC OF THE ARMY

AI summary

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