Study On Noninvasive Measurement Of Blood Pressure Utilizing Pulse Wave Transmit Time

Blood pressure is the lateral pressure that imposed on the unit area of vessel wall while blood flow inside the vessel. It is an important parameter which reflects human body circulatory system function. There are many physiological parameters, such as heart pump function, heart rate, peripheral vascular resistance, aortic flexibility, systemic blood volume and physical appearance of blood etc. embodyed in the blood pressure index. Blood pressure detection has a major significance in the prevention and treatment of diseases. In order to prevent the patient appears a clinical accident, it also need to continuously monitor blood pressure on critically ill patients and surgical patients. So the blood pressure monitor has important meaning in the family health care and the clinical diagnosis.At present, the blood pressure measurement methods can be divided into direct and indirect measurement. Direct measurement is inserting a catheter which is connected with pressure sensor in the main artery, and detecting blood pressure directly. As a result this direct method has the most accurate blood pressure data, so it is recognized as the international gold standard for detecting blood pressure. But it request operators have high technique, and also cause certain trauma to the users. So it has a lot of restrictions in use. The blood pressure also is detected by measurement of the arterial pulse, volume changes and other vascular parameters indirectly. Because it is vrey simple and convenient, so it has a broad use in clinical application.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. At last the continuous blood pressure is gained through the calculating formula after establishing an experiment system. The hardware system take MSP430F149 SCM as the core, collecting ECG signal and PPG signal with onboard A/D module, sending collected signal to PC through the serial port. The hardware system also include 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, wireless data transmission module using Bluetooth theory, power management module, and oscillometry blood pressure measurement device for calibration and tracking contrast. The software system use MATLAB as a tool for data analysis and processing, designing of the integer coefficients digital notch filter and bandpass filter, using of Hilbert transform principle to achieve peak detection of R-wave, and designing of algorithm to detect characteristic point of the pulse wave , calculatting PTT and IHR at last.In the end, the system is tested. First, use the data gained from oscillometry blood pressure measurement device to calibrate formula parameters for different individual. Second, use both oscillometry and PTT method to measure different individual blood pressure synchronously. Last, the results are analyzed using Bland-Altman method. The primary conclusion draw from this testing is the blood pressure can be measured by PTT continuously.