Inaccuracy of wrist-cuff oscillometric blood pressure devices: an arm position artefact?

BACKGROUND: Despite the increasing popularity of wrist-cuff blood pressure (BP) devices, their accuracy has not been established and international guidelines do not support their use. Because arm position influences BP measurement, it is possible that conflicting reports on wrist-cuff device accuracy reflects diverse arm positions.
METHOD: This study compared BP measured by two oscillometric devices, the upper arm-cuff OMRON HEM 705 CP and the OMRON R6 oscillometric wrist-cuff device. In the former BP was measured with the arm in two supported positions, dependent on a table (manufacturer's instructions) and horizontal (mid sternum), while the latter followed the manufacturer's instructions.
RESULTS: In contrast to the dependent arm where BP was significantly higher (P<0.05), the horizontal arm position with the arm-cuff produced a mean systolic and diastolic BP comparable to the wrist-cuff device where the wrist was at heart level being respectively, 137+/-29/80+/-16 and 134+/-27/77+/-16 mmHg. A close relationship over a wide BP range was also confirmed by least squares, least product linear regression and Bland-Altman analysis.
CONCLUSION: This study supports the use of wrist-cuff monitors for self/home use and underlines the need for a more precise definition for arm position when using all BP devices -- mercury and oscillometric.