| In a person's whole life, there is about one-third of the time spending on sleep, through sleep can help us:○1 eliminate fatigue and resume physical strength;○2 protect the brain and restore energy;○3 enhance immunity and recovery the body;○4 promote growth and development;○5 anti-aging and promote longevity;○6 protect people's mental health;○7 benefit skin care. The quality of sleep directly affects human health. However, there is no easy way to make people aware of their sleep architecture, and the importance of sleep has not been fully realized. At present, the main instrument for monitoring and diagnosing sleep is polysomnography (PSG), which has complex structure and requires to past multi-sensors on patient's body. Therefore, bring physiological and psychological burdon to patients, as well as affect patient's sleep with a relatively high cost. Furthermore, it is not easy to be portable and can not be applied broadly. In just a simple case of judging the quality of sleep, there is no need to monitor physiological signals as comprehensive as PSG do. Photoplethy- smography as an easy-access signal, not only includes the information of cardiac function, blood flow, and many other important physiological information on the cardiovascular system, but also includes a wealth of information about physiology and pathology microcirculation, It is an important source of information to study the human circulatory system. During sleep, the pulse will vary with the depth of sleep; by analyzing the sleep-related information can be isolated from the pulse. Based on this, a new method based on monitoring pulse wave signal with dual-light sources was adopted to monitor the sleep of patient, and a portable sleep monitor is designed. Firstly, we captured double-light finger signals all night long with the hardware; and then analyze the signals through PC Software, and isolated sleep-related information from the pulse signals; finally, we analyzed sleep quality with these informations.In this research, we discussed methods and principles of photoelectric finger pulse wave acquisition, evaluated the advantages and disadvantages of invasive and noninvasive detection. And its mathematical model is described in detail, illustrated the reason why choosing dual-light and the requirements of the lights'wavelength. According to the model, the parameters required to be collected in the actual circuit are: the determination of near-infrared and infrared lights'maximum intensity ( I max andΙ'max, DC component of pulse wave) and the change amplitude of the transmitted light due to the pulse beat (ΔI max andΔΙ'max, AC component of pulse wave). In addition, The SPO2 curve needs to be scaled before measuring SPO2. This paper discussed the advantages and disadvantages of traditional and modern calibration methods, and described the influence factors for measurement of SPO2.In lower computer parts, we developed the signal acquisition system of sleep monitor based on MSP430FG439, introduced the principles, structure and control approach of its various modules in detail. Constant current source with H-bridge was used to drive on the pulse probe, which not only satisfied the time-driven of LEDs, but also achieved its dynamic adjustment of light- intensity. Using microcontroller's internal amplifier, DAC, ADC, and a certain algorithm, it completed the collection of the pulse wave's DC and AC components with a combination of digital and analog manner, and completed the calculation of the instantaneous SPO2 and RRI. Through programming, the system can achieve the alarm of probe off, and automatic low-power processing.Finally, SPO2, pulse wave data and RRI were stored into a large capacity FLASH for further analysis by upper computer.In upper computer, a data analysis system of sleep monitor was designed using mixed-programming method with VC++ and MATLAB. Data was received through the serial port. The pulse, RRI and SPO2 data in accordance with the time point were obtained after decoding using established protocols. The communication between the upper computer and lower machine has two modes (real-time and non real-time reception mode). In real-time mode, collection and transmission of data began at the same time, it can be used to real-time monitor the pulse, RRI and SPO2; In non real-time mode, data were stored to FLASH firstly, when the acquisition was completed, then the data were transmited together. The correlation between sleep and various parameters were analyzed separately when analyzing the data, including time domain, frequency domain and nonlinear analysis of HRV, the waveform characteristics of the pulse wave, pulse rate and SPO2. We introduced their handling of the data in detail, isolated sleep-related information from the pulse wave, and then made an objective assessment of sleep quality. |
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