Wearable Fatigue Index Calculation via Heart Rate Variability
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Solution Overview
Problem
Current methods for assessing cancer-related fatigue (CRF) rely heavily on subjective patient reports, which are often underreported and ineffective, as patients may not accurately perceive their fatigue levels, leading to untreated symptoms and disrupted quality of life.
Innovation Solution
A wearable device with photoplethysmography (PPG) or electrocardiography (ECG) sensors collects heart rate variability (HRV) data to objectively calculate a fatigue index (FI) using LF/HF ratios, providing an objective measurement of fatigue levels over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If subjective patient self-reports are used to assess fatigue, then the assessment method is simple and easy to implement, but the measurement precision and reliability are poor because patients may not accurately perceive or report their fatigue levels
Solution Approach 1:
The patent replaces the mechanical/subjective system of patient self-reporting with an optical/physiological system using PPG sensors to detect heart rate variability. The PPG sensor measures blood volume changes in the microvascular bed, and HRV parameters (time-domain, frequency-domain, non-linear) are extracted to objectively quantify fatigue levels, substituting subjective perception with objective physiological measurement.
Solution Approach 2:
The patent introduces heart rate variability as an intermediary parameter that mediates between the physiological state (fatigue) and the measurement system. Instead of directly measuring fatigue, the system measures HRV parameters (which are influenced by autonomic nervous system activity) that serve as reliable indicators of fatigue levels, providing an indirect but objective assessment method.
2Measurement precision
If objective physiological measurements are used to assess fatigue, then the measurement precision and reliability improve, but the device complexity increases due to the need for PPG sensors and signal processing systems
Solution Approach 1:
The patent makes the PPG sensor system multi-functional by using it for both heart rate monitoring and fatigue assessment through HRV analysis. The same sensor hardware and signal processing infrastructure serve multiple purposes, reducing the need for additional specialized equipment and minimizing overall system complexity while maintaining high measurement precision.
Solution Approach 2:
The system uses the patient's own physiological signals (heart rate variability from PPG) to assess their fatigue level without requiring external testing equipment or complex intervention procedures. The body's natural physiological responses serve as the measurement source, eliminating the need for specialized external testing apparatus and simplifying the overall system.
3Reliability
If continuous monitoring is implemented to track fatigue levels over time, then the reliability of fatigue assessment improves, but the energy consumption and duration of action of the device increase
Solution Approach 1:
The patent implements periodic sampling of PPG signals at optimized intervals rather than continuous high-rate acquisition. The system collects HRV data at specific time points throughout the day, processes these periodic measurements to track fatigue trends, and reduces energy consumption by avoiding constant high-power signal acquisition while maintaining reliable fatigue assessment through strategic periodic monitoring.
Solution Approach 2:
The system uses partial action by monitoring only the essential HRV parameters needed for fatigue assessment rather than comprehensive continuous physiological monitoring. It selectively processes time-domain, frequency-domain, and non-linear HRV parameters from PPG signals, avoiding excessive measurement and processing of unrelated physiological data, thus reducing energy consumption while maintaining assessment reliability.
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
The solution provides an accurate and objective assessment of fatigue, correlating with subjective reports, enabling better management and treatment of CRF, improving patient quality of life and treatment compliance.
Implementation Method 1
A wearable device with photoplethysmography (PPG) or electrocardiography (ECG) sensors collects heart rate variability (HRV) data
Implementation Method 2
A wearable device with photoplethysmography (PPG) or electrocardiography (ECG) sensors collects heart rate variability (HRV) data
Data Source
AI summary
The present disclosure provides methods and apparatuses for determining a fatigue index. A method of determining a fatigue index may include receiving physiological signals, generating a plurality of parameters of heart rate variability based on the physiological signals, and determining the fatigue index based on the plurality of parameters of heart rate variability.