The Study Of Heart Sound Teletransmission And Analysis System

With the rapid development of telemedicine, the transmission medium has been changed from telephone line and RF modem to mobile communication network and Internet.Especially,with the advancement of mobile communication and Internet,telemedicine has been serving the community and family.So homecare has made a lot progress.Heart sound is one of the most important physiological signals and has been applied in the cardiac disease diagnose and the cardiac contractility evaluation because it can reflect cardiac inotropism and chronotropism.Therefor,it is significant to transmit heart sound by mobile communication network.A teletransmission scheme has been put forward in this thesis based on technology of GPRS and IP.Heart sound teletransmission and seamless access can be implemented based on characteristics of GPRS such as wide network coverage,high security,wide bandwidth and so on.The system is composed of data terminal and telemonitoring center server.The telemonitoring center server is a computer which has a fixed IP address.The functions of data terminal are sampling heart sound,conserving data and transmitting data.The telemonitoring center server takes charge of receiving data, displaying the wave of heart sound signal and storing data into database.The system mainly includes the following characters:(1) The time delay for data transmission is different when the length of frame and the state of GPRS network are different.In order to transmit the data securely and reliably,the interval time between two frames must be longer than the time used by frame transmission.Firstly,data terminal samples the heart sound signal and writes the data into flash memory.Then,it transmits a cardiac-cycle-long heart sound signal each time to the telemonitoring center server.(2) The strict synchrony between ECG signal and heart sound signal implies that QRS wave can be used as a start mark for a cardiac cycle.(3) A denoise method is adopted based on Wavelet Transform and Stein Unbiased Risk Estimation rule,whose threshold is adaptive.Tests show that it can filter out the main noise in the heart sound signal significantly.This study puts forward a heart sound signal's envelope detection method based on one-dimension mathematical morphology,and a heart sound signal's feature extraction algorithms based on ECG's QRS wave used to help localization,which has better recognition rate.