Research On A Novel Hygmomanometry Based On Combination Of Auscultatory And Oscillometry Methods

Automatic blood pressure measurement technology has broad applications and significant social value, low accuracy is a key technical problem which this urgently awaits to be solved. Commonly used measurement techniques fall into two categories: oscillometric method as an indirect measurement is difficult to improve its accuracy; auscultatory method is expected to significantly improve the accuracy of automated blood pressure measurement, but the filtering and identification of Korotkoff sound is the main difficulty. Therefore, we need to explore new technology in automatic blood pressure measurement.In this paper, a novel hygmomanometry based on combination of auscultatory and oscillometry methods is presented. Measuring system and specific measurement processes and relative algorithms are designed. An in-depth study on Korotkoff sound processing was carried out.Firstly, based on the analysis of Korotkoff sound signal generation mechanism, spectrum, intensity, and noise characteristics, a Korotkoff sound synthesis process is designed. Among them, the noise adaptive threshold method based on statistical is employed to achieve a strong suppression on background noise, while maintaining effective Korotkoff sound characteristic; Time domain window function based on Korotkoff sounds and pulse wave correlation is designed to eliminate random noise with substantial value; An audio spectrum based pattern matching on Korotkoff sound recognition is preliminary researched.Secondly, we designed system architecture, using the electret microphone and resistance type pressure sensor as signal measurement devices, an integrated measuring process and method are adhere to this system: A real time effective feature extraction algorithm is established to pick out useful information in pulse wave and Korotkoff sound, which can significantly reduce information storage; Oscillometric be used firstly in obtaining confidence blood pressure values intervals, while auscultatory is used to accurately determine the ultimate blood pressure, this logic ensured stability and accuracy; practical technical problems such as adaptive inflation control and fault tolerance are also included.Finally, hygmomanometer prototype is finished, including essential circuits and procedure frame. With Matlab, analysis, confirmation, and appraisal are carried out on Korotkoff sound processing algorithm. The results show that threshold filtering, window based noise reduction, and pattern matching recognition technology are valid; Practical application of the novel measuring system, signal processing method, and comprehensive measurement process in clinical surveys shown that, this new device achieves higher accuracy comparing with manual auscultatory method, it also confirmed the correctness and practicability of all the theories.