Study On Cardiac Reserve And Software Development Based On LabVIEW

Cardiac reserve(CR) refers to the heart's ability to quickly adjust to immediate demands placed upon it including cardiac efficiency reserve and heart rate reserve. Cardiac efficiency reserve is the extra-capability of cardiac rate that followed the requirement of metabolism, also called pump function reserve. The key factor of cardiac efficiency is the reserve capability of cardiac muscle contraction. The strength of cardiac muscle contraction is closely related to the amplitude of the first sound (S1),so the trend of S1 can be used to estimate the cardiac reserve. Whether the blood self-supporting time of diastolic is enough, is related to the amount of nutrients and oxygen that is preparing for the heart contraction, so the blood self-supporting time can be used as a parameter to estimate CR.The main task of this dissertation is as follows: the qualifying parameter for CR detection was defined, and the software system for CR detection was designed. In this system, the ratio of average value of S1 to average value of second sound (S2) is chosen as cardiac inotropic indicator. The ratio of diastolic (D) to systolic (S) is chosen as one indicator to estimate chronotropismus in CR. By analyzing the acquisition of heart sound samples in this system, the ratio of S1 to S2 was obtained which is generally between 1.8 and 3.0 in normal people. The ratio of D to S was chosen as the cut-off point 1.6. The CR detection system was based on Windows XP and LabView platform includeing heart sound acquisition module, database management module, CR detection module, as well as cardiac sound teaching modules. The function of the data acquisition, storage, management and analysis of CR can be implemented in this system. The quantified extraction of the assessment parameters was realized in the CR detection module such as the amplitude of S1 and S2 and the starting point.The key factor for accurate assessment of cardiac function by CR system is extraction of the characteristic value in cardiac sound especially S1 and S2. So the phonocardiogram characteristic value extraction algorithm based on Shannon standardized average energy envelope extraction and differential method to realizing extraction of the amplitude and start point position was proposed. The performance of the algorithm was verified by experiments to be accurate, reliable and practical, and easily realized.