System and method for determining an adaptive physiological strain index
Inventors
Assignees
United States Department of the Army
Publication Number
US-11564579-B2
Publication Date
2023-01-31
Expiration Date
2037-04-17
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Abstract
The invention in at least one embodiment includes a system and method for detecting and evaluating an adaptive physiological strain index (aPSI) of an individual with a processor and in a further embodiment taking into account the fitness, age and clothing of the individual based upon physiology. The invention in at least one embodiment includes a system and method to calculate the aPSI using physiological measures. In at least one embodiment, the method obtains an individual's skin temperature and heart rate in order to calculate the individual's aPSI.
Core Innovation
The invention relates to a system and method for determining an adaptive physiological strain index (aPSI) using an individual's body core temperature, skin temperature, and heart rate. It involves calculating an aPSI score that reflects the physiological strain on an individual, accounting for variables including fitness, age, and clothing factors, to provide a personalized assessment of heat-related illness risk.
The problem addressed is the inadequacy of existing physiological strain indices and environmental monitoring methods, which fail to account for individual differences such as acclimation status, fitness, body composition, morphology, prior heat injury, protective clothing, and age. These factors impact an individual's response to exertion in hot environments, and existing systems lack the adaptation to different populations, work, and protective clothing conditions.
By combining physiological measures into a single adaptive index (aPSI), the invention provides a more accurate risk assessment of heat-related illness (HRI) for individuals in various environments and activities. It utilizes sensors for heart rate and skin temperature, calculates body core temperature (potentially using Kalman filters), and adapts critical thresholds based on personal factors. Additionally, the system can provide alerts and is configured for wearable implementations to continuously monitor physiological strain and prevent heat illness.
Claims Coverage
The patent includes multiple independent claims covering systems and methods for generating an adaptive physiological strain index (aPSI). The claims focus on inventive features related to sensor configurations, adaptive calculations, and the integration of personal and physiological data to determine the aPSI score.
Sensor-based aPSI generation using heart rate and skin temperature
A system comprising at least one heart rate sensor and at least one skin temperature sensor configured to detect physiological parameters, with a processor configured to produce an aPSI score using the heart rate and an adaptive maximum body temperature based on a critical temperature and a temperature gradient between the skin temperature and a body core temperature determined from the heart rate, where the heart rate is used without signal analysis by the processor.
Adaptive aPSI score calculation incorporating individual-specific data and temperature gradients
The processor calculates the aPSI score using equations that adjust the critical heart rate and critical body temperature based on age and skin-to-core temperature gradients, producing updated aPSI values at predetermined intervals or when variances in physiological data are detected.
Inclusion of timing and activity monitoring for dynamic aPSI updates
The system includes a timer circuit and an accelerometer. The timer controls when recalculations occur, and the accelerometer detects periods of rest to determine resting physiological values (resting heart rate and skin temperature) which are used to compute the resting body core temperature.
Use of Kalman filter for body core temperature estimation
The processor calculates the body core temperature using a Kalman filter or an extended Kalman filter model to estimate core temperature from heart rate and other data when direct core temperature measurement is unavailable.
Multi-sensor configurations including internal temperature sensors
The system optionally includes at least one internal temperature sensor to directly measure body core temperature, integrated with skin temperature and heart rate sensors to produce the aPSI score.
Methods for compensating missing physiological data
The method includes using previously stored values or calculating estimates when one or more physiological readings (such as skin temperature or heart rate) are unavailable to continue producing the aPSI score.
Adaptive adjustment of aPSI based on fitness, age, and heart rate parameters
The processor adjusts the aPSI score according to individual-specific factors including fitness level, age, maximum heart rate, and resting heart rate, enabling personalized adaptation of the strain index.
Overall, the claims cover an adaptive and personalized physiological strain monitoring system and method using integrated heart rate and skin temperature sensing, advanced body core temperature estimation, dynamic update mechanisms, and customizable parameters reflecting individual characteristics and environmental conditions.
Stated Advantages
Provides an improved indication of physiological strain by combining multiple physiological measures into a single adaptive index.
Accounts for individual differences including fitness, age, clothing, and work environment that are not addressed by prior strain indices.
Enables continuous monitoring and timely alerts when physiological strain exceeds safe thresholds, helping to prevent heat-related illness.
Adaptive calculation methods, including use of Kalman filters for estimating body core temperature, improve accuracy under varying data availability.
The system's wearable configuration facilitates practical, real-time monitoring during physical activity in hot environments.
Documented Applications
Monitoring heat-related illness risk in athletes, military personnel, and workers in hot environments wearing protective clothing.
Use in occupational safety to detect and prevent heat illness caused by heavy workloads and environmental heat exposure.
Wearable devices for real-time physiological strain monitoring to inform activity or pace changes to reduce heat stress.
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