Development of a new oscillometric blood pressure measurement system

Abstract

A new blood pressure measurement system was developed, based on the oscillometric method, using a controlled linear deflation technique. The system was structured in order to make several tasks independent and specialized, thus allowing for future punctual developments. An oscillometric signal data base was formed according to the standard A N S I / W S P I 0-1992, using the manual auscultatory method as a reference to determine measurement techniques to be used The correlation among several quantities, such as reference blood pressure measurements, characteristic ratios, age, weight, height and arm circumference size, was studied. A new strategy to obtain systolic, mean and diastolic pressures was oscillometric pulse envelope, depending on parameters such as actual cuf pressure, mean pressure, pulse amplitude and arm circumference size. Mean differences of about -I,49 and 0,6I and standard deviations of 5 , I I and 5,89 mmHg were obtained for systolic and diastolic pressure measurements, respectively. Moreover, a comparative study with a commercial equipment was performed, with a simulator. IntroductionThis research describes the development and the evaluation of a new system of blood pressure measurement by oscillometric method, with the use of a controlled linear deflation technique. Technological development has made the improvement of the performance of such equipment possible, arousing the need for a new blood pressure measurement system for systolic, mean and diastolic pressure based on the profile of oscillometric pressure pulse envelope. The system provides fast and more precise measurements, similar to those obtained with the conventional auscultatoxy method, and is also immune to mhythmia and motion. It was, therefore, necessaxy to change the process of deflating the cuff and to create a new algorithm which presented a significant performance improvement, mainly in measurement accuracy and precision. 0276-6547/99 $1 0.00 0 1999 IEEE Materials and methodsThe research was developed in three sequential phases: 1. Preparation of the acquisition and storing of oscillometric signals. Data base formation for oscillatory signals and data analysis to define the strategy for measuring systolic, diastolic and mean pressure of oscillometric pressure pulses resulting from a linear cuff deflation. 2. Development and interactive upgrading of the new blood pressure measurement system by oscillometric method, with the use of a controlled linear deflation technique. 3. Performance tests and comparative stuhes of the new measurement system.The oscillometric signal data base acquisition protocol was based on the American standard for electronic or automated esphygmomanometer ANSUAAMI SP 10-1992[1]. This data base was built with the pressure signals of 10 patients in the Kidney and Hypertension Hospital in UNIFESP and 75 employees of Dixtal Biomedical Co., all registered at least three times, thus totaling 255 measurements. All measurements were sampled and stored in files through the acquisition system. Each sampled signa...

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“…The filtering method is based on removing the frequency components that belong to the deflating cuff pressure using a band-pass [51], [55] or high-pass [56] filter. The lower cutoff frequency of the filter is usually set to 0.1-0.5 Hz and the upper cutoff frequency of the filter is set around 20 Hz.…”

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