Session P34.2

The Modified Step-Wise Deflation Method in Blood Pressure Measurement

HS Oh*, YJ Chee, JS Lee, IY Kim,
S Kim, YS Kim

Hanyang University
Seoul, Korea

In non-invasive blood pressure (NIBP) measurement, most of the automatic devices use oscillometric method. There are two types of deflation in oscillometric method. One is the linear deflation and the other is the step-wise deflation method. In step-wise deflation of cuff pressure, two or more consecutive pulsations in cuff pressure are required to decide the amplitude at each step. In this study, we suggest the modified step-wise deflation to reduce the measurement time while keeping the advantage of step-wise deflation over linear deflation. With the control of the valve and real time signal processing, we implemented the blood pressure measurement system and new algorithm. We measure the amplitude of each systolic pulsation. After measuring the amplitude, the deflation to next step starts immediately and it can be finished during its diastolic period. When there is a noise or motion artifacts during the measurement of pulse, we supposed that the amplitude of the pulse varies so much when it is compared to the pulse in previous step. When the algorithm classifies the pulsation as a noise in a certain step, the program waits next pulse in that step. Also the excessively large pulses are excluded in data regression stage to detect mean arterial pressure (MAP). To validate our suggested algorithm, eleven healthy volunteers were recruited and we took the measurement 10 times under the different conditions for each subject. To evaluate its performance, the conventional auscultation method based on Korotkoff sound was performed by the well trained staff according to European Hypertension Society guidelines. The mean difference of systolic blood pressure (SBP) value from our suggested method and conventional auscultation method is 0.35±3.8 mmHg. 0.4±4.5 mmHg is for diastolic blood pressure (DBP). The result of the paired t-test for the data from two methods says that there is no significant difference for SBP and DBP. By its inherent property of single pulse in each step, the measurement time was decreased 40 % from conventional step-wise deflation method. The single pulse detection in each step can reduce the measurement time while not losing the accuracy of conventional step-wise deflation method.

(Abstract Control Number: 242)