Wearable Core Temperature Estimation Using PPG and Bioimpedance
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Solution Overview
Problem
Existing electronic devices, such as smart watches and fitness bracelets, inaccurately measure body core temperature due to neglecting factors like ambient conditions, peripheral microcirculation, and body morphology, leading to discrepancies between surface and core temperatures.
Innovation Solution
An electronic device and method that incorporates internal and skin temperature sensors, bioimpedance, and photoplethysmogram sensors to collect data on microclimate, morphology, and peripheral microcirculation parameters, using these to accurately calculate body core temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If electronic devices measure body surface temperature, then measurement is non-invasive and fast, but measurement precision is poor compared to medical thermometers
Solution Approach 1:
The patent introduces an intermediary algorithm that processes surface temperature measurements along with additional parameters (microclimate, morphology, peripheral microcirculation) to infer body core temperature. This intermediary computational layer bridges the gap between easy surface measurement and accurate core temperature representation.
Solution Approach 2:
The patent changes the measurement approach by collecting multiple parameters beyond just surface temperature (including ambient temperature, device temperature, body impedance, PPG signals) and using these changed parameters to calculate core temperature, thereby improving precision while maintaining non-invasive measurement.
2Ease of operation
If electronic devices are placed on body limbs for temperature measurement, then ease of use is improved, but measurement precision deteriorates due to temperature gradient between core and shell
Solution Approach 1:
The patent replaces direct mechanical contact temperature sensing with optical measurement methods (PPG sensors) and electrical measurement (body impedance) to infer thermal parameters. This substitution allows measurement without direct thermal contact, overcoming the temperature gradient problem while maintaining ease of use.
Solution Approach 2:
The patent adds multiple measurement dimensions (microclimate parameters, morphology parameters, peripheral microcirculation parameters) to the traditional single-point surface temperature measurement, creating a multi-dimensional approach that accurately represents core temperature while keeping the device simple to use.
3Measurement precision
If multiple sensors and parameters are collected to improve temperature measurement accuracy, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent designs the electronic device to perform multiple functions: temperature sensing, microclimate monitoring, morphology assessment, and peripheral microcirculation evaluation. By making the device multi-functional, the patent consolidates what would otherwise require separate devices into a single unit, managing complexity while improving measurement precision.
Solution Approach 2:
The device uses its own internal sensors (temperature, PPG, body impedance) to automatically collect and process the necessary parameters for core temperature calculation without requiring external equipment or manual intervention, thereby reducing operational complexity despite the comprehensive measurement capability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables real-time, accurate determination of body core temperature by considering various influencing factors, improving measurement precision and reliability.
Implementation Method 1
at least one photoplethysmogram (PPG) sensor configured to measure at least two photoplethysmogram (PPG) signals with different wavelengths
Implementation Method 2
at least one bioimpedance sensor configured to measure at least one body impedance parameter of the user
Implementation Method 3
at least one internal temperature sensor configured to measure a temperature inside the electronic device, at least one skin temperature sensor configured to measure a skin surface temperature of the user
Data Source
AI summary
A method performed by an electronic device for determining a body core temperature of a user is provided. The method includes obtaining, by the electronic device, an internal temperature inside the electronic device, a skin surface temperature of the user, at least one body impedance parameter of the user and at least two PPG signals with different wavelengths, obtaining, by the electronic device, a measurement data set including the internal temperature, the skin surface temperature, the at least one body impedance parameter of the user and the at least two PPG signals, determining, by the electronic device, microclimate parameters around the electronic device based on a local ambient temperature and a local temperature, determining, by the electronic device, body morphology parameters of the user based on profile data of the user and the at least one body impedance parameter of the user, determining, by the electronic device, peripheral microcirculation parameters of the user body based on perfusion parameters of the user body which are calculated from the at least two PPG signals with different wavelengths, and determining, by the electronic device, the body core temperature of the user based on at least one of the measurement data set, the microclimate parameters around the electronic device, the body morphology parameters of the user, or the peripheral microcirculation parameters of the user.