Design Of Wearable Sleep Breathing Monitoring System

Sleep is an extremely significant physiological activity.Research shows that nearly one-third of people in the world suffer from various sleep disorders.Among them,sleep apnea hypopnea syndrome(SAHS)has gradually attracted people’s attention,due to its strong concealment and great harm.SAHS can cause repeated apneas and hypopneas during sleep,resulting in insufficient oxygen supply in the body,hypoxia in the body and tissues,and damage to organ functions.In the long run,it may develop into diseases such as high blood pressure and coronary heart disease,which will seriously threaten people’s life and health.Therefore,it is necessary to screen for SAHS through sleep apnea monitoring as early as possible.Compared with polysomnography in hospitals,portable sleep respiration monitoring equipment has the characteristics of small size,low cost,and always-ready.It is more suitable for home use.By analyzing the pathogenesis and diagnostic criteria of SAHS,a wearable sleep breathing monitoring system based on piezoresistive flexible membrane pressure sensor is developed.The main research contents are as follows:(1)The hardware acquisition equipment of sleep breathing signal is designed and made.The wearable part of the device is in the form of shorts with built-in main and auxiliary dual sensors,which can realize continuous monitoring of sleep breathing signal through normal wearing.The signal conditioning circuit in the hardware part can realize the functions of linear conversion,filtering,amplification of respiratory signal and the correct wearing indication of the device.The system also adds a signal correction circuit,which can correct the respiratory signal collected by the main sensor according to the sleep position signal measured by the auxiliary sensor.The core controller of hardware circuit is MSP430 single chip microcomputer,which mainly completes the A/D conversion and data transmission function of respiratory signal.(2)The sleep respiration monitoring software is designed with LabVIEW,which can realize the input and management of basic user information,as well as the real-time display,detection,storage and playback of the sleep breathing signal waveform,and alarm for abnormal breathing frequency and long-term apnea.The system uses state machine to judge and record apnea and hypopnea during sleep,and gives health analysis report based on BMI and AHI after collection.(3)According to the beginning and end time of each apnea occurrence,the apnea waveform is extracted,and the image recognition algorithm based on shape context feature is used to further classify the waveform,so as to obtain the type of apnea.Through comparative experiments,the relationship between the number of different contour points and the recognition accuracy and speed is analyzed.The experimental results show that the system has great practicability and accuracy,can be used as a preliminary screening tool for SAHS,and can meet the needs of respiratory monitoring in families.