Research And Implementation Of On Wearable Heart Sound Monitoring Device

Cardiovascular disease has become one of the leading cause of death for human being,accounts for 1/3 of the global deaths.The doctor initially diagnoise through the electrocardiogram(ECG)and heart sound ausculation methods to know the patient's heart health status.However,it is difficult to detect structural abnormalities of heart valves and defects containing heart murmur features from ECG;The interpretation of heart sounds using traditional auscultation methods is greatly influenced by subjective factors such as experience,skills and hearing of doctors;It is impossible to continuously monitor and record the patient's heart sound signal,and hard to capture rare heart sounds to understand the evolution of heart diseases.Therefore,it is urgent to implement a computer-assisted auscultation method for long-term,dynamic monitoring of cardiac conditions in patients with early and sudden heart disease to capture transient non-sustained abnormal heart sound changes.At present,many heart sound monitoring devices have the characteristics of large size,high cost,uncomfortable for wearing,and cannot be used for long-term dynamic heart sound monitoring.To solve the above problems,this thesis designs and implements a wearable heart sound monitoring device.The main research contents are as follows:1)Design a prototype of a heart sound sensor.Firstly,the structural design is completed according to the characteristics and design requirements of the sensing element;To balance the detection effect and size,ANSYS modeling and simulation is used to determine the optimal size of the sensor;The simulation results show that the prototype mode of the designed sensor is mainly 1st order,and the corresponding natural frequency is 2236.1Hz.The sensor is then sewn to the fabric substrate to prepare a wearable chest strap.Finally,the performance of the sensor prototype is tested by BIOPAC multi-channel physiological instrument.The results show that the sensor prototype can be used for heart sound signal acquisition,and its signal-to-noise ratio is 2dB higher than that of TSD108 sensor.2)The hardware platform of the heart sound monitoring device is built to realize the functions of heart sound signal acquisition,conditioning and wireless transmission.First,the original heart sound signal is amplified and filtered by the conditioning circuit.The conditioned signal passes through the audio power amplifier circuit to realize the realtime auscultation function of the heart sound,and the other way directly enters the main control module to realize the analog-to-digital conversion.Wireless communication with the host computer is previously implemented through the Bluetooth module.To meet the wearable and non-obtrusive characteristics of the monitoring device,the hardware platform has high integration,small size and light weight.3)Develop hardware driver for heart sound signal acquisition platform to realize heart sound signal acquisition,analog-to-digital conversion,wireless transmission and other functions;At the same time,the PC software of the heart sound PC is designed to receive and analyze the collected heart sound data,waveform display and data storage,and the EMD method is used to realize the function of heart sound preprocessing.4)Finally,the performance and reliability of the heart sound monitoring device are tested and verified.The test includes system test,subjective and objective evaluation and heart sound collection test under different motions.The results show that the heart sound monitoring device proposed in this thesis can pick up good quality heart sound signals and realize heart sound auscultation;it can realize long-term dynamic heart sound monitoring under static or slight motion.Above all,compared with the existing heart sound monitoring methods,the designed device has the characteristics of low cost,small size,unobtrusive,unrestrictive and wearable.In a static or slight motion state,it can achieve long-term dynamic heart sound monitoring.