Session PB6.1

Mean Arterial Pressure Estimation Method Using Morphological Changes in Oscillometric Waveform

SH Song*, DH Kim, JS Lee, YJ Chee, IY Kim

Hanyang University
Seoul, Korea

The estimation method of MAP (Mean Arterial Pressure) has used the magnitude of oscillometric pulses using the conventional oscillometric method. When the pressure of the cuff is decompressed, the magnitude of the oscillogram pulse is usually increased gradually and its peak is shown nearby the MAP point. After this point, the magnitude has shown a decreasing trend. But this trend is not always shown. For example, oscillogram shape is shown the flat trend like a trapezoid in some subjects’ cases that have cardiovascular disease or ages are high. In these cases, the estimation of MAP is difficult because it is hard to find the maximum magnitude information. To solve this problem, we designed a new method of estimating MAP only through the morphology changes of the pulse without information of magnitude.
When the pressure of the brachial cuff is decompressed, the morphology of the primary oscillogram pulse shows the flat slope from the peak to the end point of each pulse. However, if the cuff pressure is lowered gradually, the slope is steeper, and eventually the part of the flat slope disappears. For detecting this point, we normalized the amplitudes and widths of whole pulses, and drew a straight line from the peak to the end point of each pulse. We then calculated the area between the straight line and the pulse in each pulse. Through this process, we found that the area rapidly decreased when the part of the flat slope disappeared. Finally, we compared this point with the reference MAP for validation.
46 subjects’ (11 males, 53 females, the ages of 20~70 years) cuff pressure was recorded in Seoul National University Hospital for validation, and two observers who were trained by the BHS program measured the SBP (Systolic Blood Pressure) and the DBP (Diastolic Blood Pressure) by the auscultatory method as a reference. After averaging the measured SBP and DBP, the reference MAP were calculated by the equation 1/3 SBP + 2/3 DBP using these values, and compared with the measured MAP. The resulting mean difference and standard deviation are shown: -2mmHg and 4.52mmHg respectively.
This method is an easy and correct way that finds the MAP and blood pressure using the oscillometric method. In addition, if we supplement the algorithm using the MAP which is measured by an invasive blood pressure device, this method would be expected to yield even more correct results.

(Abstract Control Number: 185)