Research Of Cardic Reserve Monitoring System Based On Smartphone

With the rapid development of economy, people’s living standards have beengreatly improved, more and more social resources are invested in medical healthcare.However, a lot of serious problems are still existed in public healthcare system. Forexample, medical resources are extremely uneven distributed. Currently, thecardiovascular disease has become major public health problem because of its highincidence and mortality. Heart sound is the reflection of cardiovascular systemmechanical movement conditions. Cardiac reserve represents the increase capacity ofcardiac function. So, non-invasive monitoring of cardiac reserve based on heart soundcan be used as an effective method to diagnosis the cardiovascular diseases. Potentialcardiovascular diseases can early be detected through cardiac reserve monitoring so asto prevent these diseases instead of treatment. In this paper, cardiac reserve monitoringis proposed to prevent cardiovascular diseases. Meanwhile, it can help to solve theproblem that medical resource is uneven distribution, such as expensive and difficult intreatment. Cardiac reserve monitoring is realized by heart sound detection. Thefollowing aspects are the main content of the research.Firstly, the characteristics of heart sound are analysed. To confirm itstime-frequency characteristics, short time Fourier transform is applied.Secondly, heart sound acquisition circuit is designed, which consist of analogcircuit and digital circuit. The analog circuit includes a power supply circuit and a signalconditioning circuit. The power supply circuit provides3.3V to supply microprocessorand bluetooth module and±5V to supply amplifier. The signal conditiong circuitincludes preamplifier circuit, band pass circuit,50Hz notch, post amplifier, level upliftcircuit which are used to condition the signal. The digital circuit includes the design ofmicroprocessor software and bluetooth module. The reasonable design of software canconvert the analog signal to digital, and then the digital signal is transmitted bybluetooth module.Thirdly, a software program is designed. At first, mobile software developmentenvironment is established. Then the algorithms of denoising and feature extraction areresearched. Using db4and five levels of wavelet decomposition can get a gooddenosing effect. Denosied signal envelope is extracted by Shannon energy. In order toextract the three features (the ration of first heart sound amplitude to second heart sound amplitude, S1/S2; the ration of diastolic to systolic duration, D/S; heart rate, HR) ofcardiac reserve, the difference method to determine the location of S1and S2is used. Atlast, the software is realized.Finally, after the hardware circuit testing, microcontroller control program testing,algorithm testing and functional testing, the results showed that the cardiac reservemonitoring based on smartphone can realize the basic functions and operate stably.