The Research Of VDT Mental Fatigue Estimated Method Based On ECG And Pulse Signal

Now Visual Display Terminal (VDT) has been widely used in study, work and life. It makes the work and life more convenient and efficient, and also causes some new occupational health problems, such as visual fatigue, mental fatigue and muscle fatigue, etc. Because of mental fatigue, the quality of people's lives would be affected, work efficiency would be reduced and social economic development would be hindered. The study of mental fatigue has become a top priority. Therefore, it has the very vital significance to understand the nature of VDT mental fatigue and the effect of fatigue on people's life for taking precautions against fatigue during the VDT work.At present the traditional methods to determine physiological mental fatigue are mainly subjective evaluation method and objective evaluation method two kinds. With the development of science and technology, there are more and more objective methods to research fatigue, and physiological indexes intervene makes it a medical, cognitive science and psychology research hot spot. However, the detection of mental fatigue is still lack of objective physiological indexes. The ECG and the pulse signals contain rich human physiological information, and they can reflect the physiological state of each subsystem and the pathological changes of physiological condition well in human body. This paper discussed the VDT mental fatigue influence to human physiological signal, mainly through ECG signal, pulse signal and temperature signal processing and analysis.In this paper, a mantal fatigue experiment is desgined. All the subjects are required to finish the the addition and the substraction of two three-digits on computer for 1.5 hours. At the same time, the ECG, the pulse singal and the body temperature signal are acquired. Some characteristic parameters are extracted from the physiologic signals and analyzed, such as the peak value of the pulse signals (map), the tidal wave peak of the pulse signals (map1), the heart rate, the amplitude of S waves in the ECG, the RMSSD and the PNN50 of heart rate variability, and some frequency indexes etc, the frequency indexes main contain LF, HF and LF/HF and so on. The VDT mental fatigue state is estimated by analyzing the changes of these characteristic parameters before and after the experiment. In addition, a preliminary exploration is comducted to the body temperature. Compared with mental fatigue pre-experiment, the temperature of the subject increases significantly (P<0.001), and the PNN50 increases obviously (P<0.05), and the amplitude of S waves of the ECG signals decreases obviously (P<0.05) after mental fatigue experiment; compared with the end of mental fatigue experiment, the temperature increases, and the changes of PNN50 are not obvious, and the amplitude of S waves increases significantly (P<0.01), and the mental fatigue is somewhat remittance after natural recovery. According to the results of the experiment group and the control group, the main wave peak and the tidal wave peak of the pulse signals are all declined significantly (P < 0.001). But from the declining degree, the pulse peak of the subjects in the experiment group decreases more significant. However, the experiment results in control group have demonstrated that the physical fatigue will also appear on the subjects in the nature state, which makes the physiological characteristic parameters change. The results above have revealed that the objective indicators can be found to evaluate the VDT mental fatigue effectively through the analysis of the human physiological signals.