A Preliminary Study Of Sub-healthy Evaluation System Based On Cardiac Reserve

Sub-health, which troubles most people in today's life, is a third state other than healthy and sick state. Therefore, the research of its diagnosis and therapy techniques has important scientific and social significance for the prevention and treatment of disease. This dissertation theoretically demonstrates the feasibility to evaluate people's sub-healthy state by quantifying mental and physical fatigue, which is based on the relationship between cardiac reserve, heart rate variability(HRV), and accumulated human physical activity(AHPA). Besides the design of its hardware and software, the algorithms of de-noising and extracting the signal's characteristic points are also been discussed in this paper.The results of the theoretical research show that: (1) Fatigue and tired feeling are the representative features and pathogeny of sub-health. Fatigue will affect the activity of the autonomic nervous system(ANS), and the activity of the ANS has a close relation with the functions of cardiac muscles and people's exercise ability. Therefore, we have good reasons to think that in some degree it is reasonable to quantify physical and mental fatigue by using several indexes of cardiac contractility and heart rate(HR). (2) Although there are different types of sub-health in sub-healthy patients, their physical exercise ability is prevalently low, and their daily AHPA is mostly lower than healthy people. (3) Cardiac reserve is one of the most important factors to determine people's physical exercise ability. Due to lack of physical exercise, there should be some differences between sub-healthy patients and healthy persons. Since limited by the conditions and theories of detection methods, the present sub-health evaluation techniques have some difficulties to evaluate objectively and quantitatively. Referring to the present evaluation methods and combined with the fatigue features of sub-health, this paper firstly proposed systematically an integrated method, which is based on the indexes of cardiac functions and AHPA. This method is non-invasive, quantitative, inexpensive, and convenient in detecting and evaluating sub-healthy state, and also can monitor continuously that how does the sub-healthy state affect individuals. This paper designed a portable device to evaluate people's fatigue and health state by measuring their exercise ability. It consists of a 32Mbyte FLASH memory, a PIC microchip, a universal serial bus(USB) transfer interface, phonocardiographic(PCG) detection circuit, electrocardiogram(ECG) detection circuit, and human physical activity movement signal detection circuit etc. Our experiments showed that it has following virtues: low power consumption, compact volume, lasting record, convenience, rapid transfer speed, stable quality etc. The software includes system management module, USB data communication module, dada review and analysis module, and database management module. The developing environment was Delphi 6.0 and the Access relational database (Microsoft, Inc.). Because of the importance of the detection of R-wave position, this paper also proposed a filtering method for exercise ECG(EECG) signal, which is based on Wavelet Transform(WT) and Stein's Unbiased Risk Estimate(SURE). Our experimental results demonstrate that the myoelectric disturbances and baseline drift in EECG signal can be removed efficiently, which affords the solid foundation for the further evaluation and study of people's sub-healthy state in various vocations.