Preventing troublesome variability in clinical blood pressure measurement.

Abstract

The importance of accurate blood pressure (BP) measurement is well-established. However, there is little quantitative comparative data on the influence of different measurement conditions on BP or the stability of the oscillometric pulse waveform from which BP is calculated. This study investigates the effect of six different measurement conditions (Quiet, Reading, Speaking, Deep Breathing, Moving, and Tapping) on BP readings in 30 healthy normotensive subjects. We hypothesize that non-standard conditions will result in significant deviations in BP measurements compared to the Quiet condition. Additionally, the quality and stability of the oscillometric waveform were assessed by evaluating the smoothness of the oscillometric pulse waveform characteristics during cuff deflation. Compared with the Quiet condition, all others resulted in significantly higher blood pressures, except for the respiratory condition, which resulted in significantly lower BPs. Average subject systolic BP (SBP) rose from 117.4 ± 6.0 mmHg for the Quiet condition to 129.7 ± 7.2 mmHg for the light finger tapping condition, P < 0.00001. Overall, changes for diastolic BP (DBP) were not significant. For the quality Noise indicator, all conditions in comparison with the Quiet condition were significantly noisier, increasing from 0.144 ± 0.024 to 1.055 ± 0.308 mmHg, P < 0.00001. Changes in SBP were significantly correlated to changes in quality Noise (r = 0.965, P < 0.001). This study confirms the importance of following international BP measurement guidelines, providing quantitative data showing significant changes in BP when guidelines are not followed. A method for assessing the quality of the measurement is also demonstrated, and shows that BP changes are significantly related to changes in the quality indicator.