Study On A System Of Non-Invasive Continuous Blood Pressure Measurement Based On Pulse Wave Transit Time

Blood pressure is an important physiological indicator of cardiovascular function. It has significance for both clinical monitoring and medical diagnostics. As blood pressure values are always influenced by many factors, such as physical state, measurement time, equipment etc., single blood pressure gauge cannot reflect the current physical conditions precisely. While continuous blood pressure monitoring can follow the changing effectively, it is beneficial to the prevention and treatment of hypertension. But the existing methods of non-invasive continuous blood pressure measurement do not get rid of the cuff and the positioning of sensors are highly required. They are not suitable in the long-term survey.In this study, we designed a system of non-invasive continuous blood pressure measurement that based on pulse wave transit time (PTT). It was developed depending on the linear relationship between blood pressure values and PTT. By calculating the blood wave transit time, we could get human blood pressure indirectly. The system designed in this way could help users to get rid of the gasbag and make them much more comfortable. The main contents of this thesis include:(1) Build the module between blood pressure and PTT. We used simple linear regression module and elastic cavity model to establish the linear relationship between artery systolic pressure (SP) and PTT and diastolic pressure (DP) and PTT respectively.(2) Design the hardware of the blood pressure measurement. The system choose HKD-10C ECG sensor and HKG-07C infrared pulse sensor (Huake Information Technology Co. Ltd) to acquire signals and we use the USR-WIFI232-T module (Jinan USR IOT Technology Limited) to transmit them. The collected ECG and PPG signals would be simultaneously delivered and processed on the PC platform.(3) Implement the software of the system on PC. The thesis used socket to realize the signal communication between PC and wifi modules and used multi thread technology to guarantee the acquisition of ECG and PPG signals synchronously. After the signals were received, the wavelet transform algorithm was designed to remove the high frequency noise to extract the characters of ECG signals and PPG signals accurately. According to the modules and the characters the current human systolic pressure and diastolic blood pressure could be calculated. Finally, the values were stored in the Access Database.The system was developed by C++ and MATLAB languages on the PC platform. And the Terminal operation interface was based on the MFC framework under the integrated development environment of Microsoft Visual Studio.