Design Of High Precision Blood Pressure Measurement System Based On Oscillometry

As the improvement of living standards, people ’s own health attracts more andmore attentions. Blood pressure is a very important indicator reflecting the health ofhuman physiology. However, blood pressure is susceptible and hard to measure, dueto some internal or external factors such as mood and sport conditions. Therefore, theconvenient, fast and accurate blood pressure measurement has a very importantsignificance for clinical care and health care.The hardware of the systemconsists of upper and lower machine compositions.The upper uses PC as a platform, employing Microsoft Visual Studio developmenttools to design controlling interface and display important datas. The lower uses theARM controller STM32produced by STMicroelectronics as the core and theμC/OS-II embedded operating system as the software platform, combined with thepressure sensor, band pass filter, solenoid valves and pump constituting the main bodyof blood pressure measurement device. The core of the software is the signalprocessing algorithms: draw into a one-order low-pass IIR digital filter while readingthe pressure sensor datas to exclude the noise which is similar with pulse wave signal;by analyzing the pulse wave feature points, adopt an improved threshold methodwhich can accurately detect the pulse wave peaks under a variety of pathologicalconditions, it overcomes the disadvantages that the traditional threshold method’saccuracy is not high; explore a variety of data fitting algorithms, including the leastsquares method, Gaussian fitting, adaptive Kalman fitting, and finally select theadaptive Kalman fitting algorithm which has fast convergence and is not easy todiverge, its variance is relatively smaller and it is closer to the distribution of theoriginal datas; adopt an improved amplitude coefficient method by using an averagepressure value to determine the scale factor, which can improve the individualadaptation and outcome accuracy;The system has been tested by BP-Pump2non-invasive blood pressure monitortester from three aspects which are standard mode, patient mode and arrhythmia mode.The statistical test results show that: average measurement error of blood pressure isless than4mmHg, measurement range is0~295mmHg and measurement time is about30s. Meantime it has high precision, wide range and high speed. It is in line with themeasurement requirements that the international organization of Legal Metrology released non-invasive electronic sphygmomanometer of QIML R16-2in2002. It hasachieved the goal.