Session PB6.2

Estimation of Blood Pressure Using Photoplethysmography on the Wrist

SH Song*, JS Cho, HS Oh, JS Lee, IY Kim

Hanyang University
Seoul, Korea

Blood pressure is one of the most basic vital signs that indicate hypertension, diabetes, obesity, or some kind of cardiovascular diseases. Therefore, it is important that measuring and managing the blood pressure easily and continuously at home. In general, home automatic sphygmomanometers are inaccurate and inconvenient, so a new algorithm or technique is necessary for improving the performance of measuring device. We have studied a new method that estimates the blood pressure using wrist cuff and wrist PPG (Photoplethysmography) signal.
When the pressure of wrist cuff is decompressed, the PPG pulse appears at certain point that is similar to Korotkoff sound. This point can be related to SBP (Systolic Blood Pressure). After the pulse appeared, the morphology of PPG pulses were started taking the certain shape, and then the reflection wave of PPG pulses were appeared rapidly and were maintained from specific point. So, we detected the point that the slope of reflection wave changed rapidly, and then this point compared with the reference DBP (Diastolic Blood Pressure) for validation. The reference SBP and DBP are measured by two observers who were trained by the BHS program using auscultatory method at the left upper arm. Subjects were 13 non cardiac disease of man in their twenties.
The result of this methods, the pressure at the point that PPG pulse appeared was 14mmHg (mean value of difference) higher than the reference SBP, and the pressure at the point that slope of reflection wave changed rapidly was 18mmHg (mean value of difference) higher than the reference DBP. So we defined the SBP and DBP of PPG pulse as the values that were subtracted by two difference values. In conclusion, the mean difference of the blood pressure, SBP and DBP, between auscultatory method and PPG analysis is 2.08 ± 5.07mmHg and 1.38 ± 7.86mmHg respectively.
The research which estimates the DBP using the morphology of PPG signal has hardly existed even though the research of SBP estimation has existed numerously. In this study, we suggest the efficient method that improves the accuracy of blood pressure estimation according to finding the method that estimates the DBP using the change of morphology in PPG signal without the amplitude information.

(Abstract Control Number: 186)