Design And Study On Prototype Of Non-invasive Blood Pressure Monitoring System Based On Pulse Wave

Blood pressure is the lateral pressure that imposed on the unit area of vessel wall while blood flow inside the vessel. Arterial blood pressure is important physiological parameter for the assessment of cardiovascular haemodynamic function in basic medical research as well as in clinical application. Blood pressure can fluctuate distinctly with individual biothythm, emotion and any other kinds of internal and external stimulations. Therefore, the blood pressure of every single measurement or continual measurement comes out discrepantly. By measuring the blood pressure in every cardiac cycle, continuous measurement is proved to be significant in the family health care and clinical diagnosis. Yet,the existing continuous blood pressure measure approaches are not suitable for long-term continuous blood pressure measurement due to complicated apparatus and specific position for the high precision sensors.Based on the study of relevant theories on arterial blood pressure and pulse wave transmission, the thesis developed a cuffless and noninvasive method for blood pressure measurement by PTT. This dissertation investigates a new noninvasive continuous blood pressure measurement by Photoplethysmography pulse wave and a new concept about normalizing concept about the Photoplethysmography pulse wave. Based on this concept, a new approach is developed to calculate cardiovascular parameters and diastolic pressure. Compared with the results of oscillometry method,the results from this novel measure system showed that the system has the potential to used in basic research and clinical application.The main tasks and results of this dissertation are summarized as following.1. Extraction of the continuous ECG and PPG signals based on Software/Hardware Co-Design.The hardware system takes MSP430F149 SCM as the core, collecting ECG and PPG signals with onboard A/D module, sending collected signal to PC through the serial port. The hardware system also includes PPG signal conditioning module designed in the use of Lambert– Bill theory, and ECG signal conditioning module designed on the basis of Einthoven standard ? lead linking way. This thesis based on. Net Framework technology, designed and implemented the detection software running on the Windows XP, successfully storage and display the PPG and ECG signals.2. Signal processing of pulse wave by wavelet transformation.The Photoplethysmography signal is a kind of faint physiological signal and very vulnerable to be interfered by noise. Meanwhile,the shape of the pulse wave changes greatly from person to person because of the variability of individual artery elastic and blood content in the finger capillary vessels. This thesis investigates the spectrum of pulse wave and the source of noise, and develops a method of reducing the noise and identifying the charaeteristic points of pulse wave.3. Extraction of cardiovascular parameters by normalized Photoplethysmography pulse wave.This thesis investigates the relation between Photoplethysmography pulse wave and blood pressure waveform by considering the formation mechanism and propagation process of pulse wave. The dissertation also investigates the relation between arteria lblood pressure and cardiovascular parameters by looking into the single elastic cavity model and two elastic cavity model of Human Cardiovascular System. Besides that, the thesis develops a calculating method of cardiovascular parameters based on the new concept developed about normalizing the Photoplethysmography pulse wave.4. Calculating of the systolic pressure and diastolic pressure by analyzing the pulse wave Propagation time and normalized Photoplethysmography pulse wave.The theory of calculating systolic pressure by analyzing the pulse transit time,and the method of calculating the systolic pressure by deriving the equation of pulse transit time and systolic pressure and calibrating parameters of the equation by experiment is provided. The method to calculate diastolic pressure by using Photoplethysmography pulse wave is analyzed in this paper. Cardiovascular parameters are obtained in calibration experiment and diastolic pressure is figured out continuously by using systolic pressure and cardiovascular parameters.5. Experimental test of the system.Based on the data gained from oscillometry blood pressure measurement device, formula parameters for different individual are calibrated. Then different individual blood pressure is measured by using both oscillometry and PTT method synchronously. Finally, the analysis and comparison of the measurement results should be done to test the system.