Influence of Finger Movement on the Stability of the Oscillometric Pulse Waveform for Blood Pressure Measurement

In medical clinics the oscillometric automated sphygmomanometer is widely used. However, there are few studies to quantify the influence of the oscillometric pulse waveform stability on the accuracy of BP values. This study addresses this issue. Cuff pressure signals during the slow deflation phase were measured from 20 healthy normotensive subjects. For each subject, measurements were performed with the normal quiet and still body condition, and also when subjects moved their fingers. Oscillometric pulse waveforms were filtered from the cuff pressure signals. The second-order Gaussian model was used to fit the peaks of the oscillometric pulse waveform. The root mean square error (RMSE) between the fitted curve and the pulse amplitudes was used to assess the smoothness of the oscillometric pulse waveform characteristics. Compared to the quiet condition, finger movement increased the RMSE by 0.28 mmHg. Finger movement also resulted in a significant increase of Systolic blood pressure (SBP) by 7.2 mmHg and diastolic blood pressure (DBP) by 9.2 mmHg (both P<0.01). This study quantitatively showed the effect on BP and oscillometric waveform stability of subjects not following the requirement to stay still.