A Non-invasive Continuous Blood Pressure Measurement System Based On Pulse Wave Velocity

As the development of living quality and improvement of diet structure, people paymore and more attention to decrease the morbidity and mortality of cardiovascular andcerebrovascular diseases which have become a serious threat of human’s health, especiallyfor hypertension crowd. Blood pressure, as one of important parameters in vital signsmonitoring, is not only a physiological index of the cardiovascular function, also animportant parameter of human circulatory system. It plays a significant role in the diseasediagnosis, therapeutic effect observation and rehabilitation monitoring, and prognosisjudgment process.There are two ways to realize noninvasive blood pressure measurement: direct andindirect way. By analyzing the research in domestic and foreign in the last few decades, it isfound that traditional continuous noninvasive blood pressure measurement (such as his soundauscultation method and wave method) is unable to realize a real-time detection and can beeasily influenced by many factors. So this method produces a bigger error. Continuousnoninvasive blood pressure measurement can monitor the changes in each cardiac cycle ofartery blood pressure waveform, which provides an effective way for early detection andtreatment of hypertension disease. The significance of continuous noninvasive blood pressuremeasurement becomes more obvious under the special environments like overweight andweightless. Compared with the continuous measurement method, noninvasive continuousblood pressure measurement is more important in clinical and medical research.In this paper, after having a good understanding of the background and significance ofthis research, a complete noninvasive continuous blood pressure measurement system is fulldeveloped based on the pulse wave velocity. The main work and results of this study are asfollows:1. Establish the mathematical model and develop a detection method based on thedeeply analysis of the blood pressure and pulse wave forming mechanism, the influencingfactors and the relationship between pulse wave velocity and blood pressure.2. A noninvasive continuous blood pressure measurement system is design based onpulse wave velocity. The hardware includes: MC9S12XS128SCM smallest system, adders,keyboard circuit, LCD display module, dual D/A converter circuit, and serial communicationinterface module. Use the built-in A/D component of SCM to realize a high-speed andreal-time data acquisition. And the data is stored in an expanded storage. The value of pulsewave velocity is displayed in real-time way. The data is transmitted to a PC through a serialcommunication. Complete the data analysis, processing and display on the MTALABplatform. Calculate the value of arterial blood pressure and complete the design of the wholesystem based on pulse wave velocity of the blood pressure value and the value of curvefitting. The feature point extracting of the pulse wave signal is the key and also the difficultpart of this design.3. Do experiments and discuss the results. Measure and record the blood pressure from several volunteers by using Omron electronic sphygmomanometer and our developedsystems respectively. Comparing the data, it is found that the error of testing results can becontrolled in the standard error range. The feasibility of our method is proven and theexpected goal is achieved.Two pulse sensors are applied in this research. The data of two pulse wave signals arecollected at the same time to make sure that the data is from the pulse signal at two differentparts. This system has a friendly human-computer interaction platform and can achieve thereal-time multi-point data acquisition, processing, analysis, and display. Also, this systemsatisfies the requirements of a small volume and power consumption, and strong analysisability. However, this system can still be improved through modifying the algorithm based onmore experiments. It will offer a better reference value for the clinical diagnosis and homenursing.