Heart Rate Variability Analysis in Healthy Subjects Under Different Colored Lighting Conditions

The exposure to colored light with different wavelengths has proved to affect the physiological functions of the human body. To test such influence, this work was focused on heart rate variability (HRV) analysis associated with different colored light exposure of healthy volunteers. A Photoplethysmography (PPG) wireless sensor network node was employed to acquire information about the cardiac activity, as it proves to be a more convenient and less intrusive method as electrocardiography (ECG). A small group of healthy volunteers were exposed to 10 minutes of blue and red light, preceded and followed by 5 minutes of dark lighting conditions. HRV was acquired during the last 5 minutes of each colored illumination period. The HRV analysis was based on time-domain variables, frequency-domain variables and fractal (nonlinear) analysis. The experimental results from this study show that PPG can be considered as a reliable method to study HRV. The exposure to different colored light conducted to HRV variations that characterize the autonomous nervous system balance. Experimental results obtained for volunteers exposed to different illumination conditions are also included in the paper.