Development of full-featured ECG system for visual stress induced heart rate variability (HRV) assessment

Visual stress which can induce headache, migraines and eyestrain affects our body often detrimentally. Heart rate variability (HRV) analysis is commonly used as a quantitative marker depicting the activity of autonomic nervous system (ANS) that may be related to visual stress. In this paper, we proposed an improved HRV methodology for HRV features extraction and analysis. Firstly, a multi-channel portable ECG device has been developed for signal collection, and then we designed full-featured ECG monitoring system which suitable for real-time ECG display, signal processing, high accuracy R wave detection and HRV analysis in time and frequency domain. Taking consideration of the simplicity and real-time, the design of processing flow includes three stages. The first stage is signal preprocessing, we introduced a simple and reliable method termed the Mathematical Morphology (MM) and Difference Operation Method (DOM) for de-noising and R wave amplification. The second stage is to look for the point R and extract R-R interval series based on the above processing. The last stage focuses on HRV analysis from the aspects of time domain and frequency domain. Moreover, this research investigates the relationship between visual stress and HRV, 15 healthy, right-handed volunteers (all males aged from 19 to 25 years) participated in the experiment; there is significant changes of HRV features of visual stress condition compared to reference state. These results show that the HRV is affected by the presence of visual stress and long-term visual stress may weak the function of ANS, which may enable us for visual stress monitoring and management in daily life.