Quantifying the Accumulated Stress Level Using a Point-of-Care Test Device

This study developed a portable embedded multi-sensor fusion for point-of-care health monitoring to evaluate the accumulated stress levels of affected people. The instrument integrates numerous physiological parameters to quantify the level of accumulated stress, which is one of the leading causes of cardiovascular disease. The participants in this study were assigned daily mental arithmetic tasks over one week to simulate stress-accumulation conditions. Fuzzy logic rules were defined to quantify the accumulated stress level by combining electrodermal activity (EDA) and electrocardiograph (ECG) and photoplethysmograph (PPG) signals. The trends of 21 physiological parameters were analyzed and compared, from which the following four physiological parameters were identified as being representative of the effective response to cumulative stress: (1) the heart rate, (2) the ratio of low- to high-frequency powers for heart rate variability (HRV), (3) the skin conductance level (SCL) and (4) the liver harmonic proportion (i.e. the first harmonic of the peripheral blood volume pulse spectrum). Subsequently, the observed trends of these four parameters were combined to enhance the robustness and the reliability of the proposed system by adjusting the applied fuzzy logic rules. The experimental results show an 82% correlation between the measured level of accumulated stress and the social readjustment rating scale (SRRS) obtained from subject-independent testing.