Comparison of oscillometric blood pressure measurements at the wrist with an upper-arm auscultatory mercury sphygmomanometer.

1. Oscillometric devices for blood pressure (BP) measurement at the wrist are becoming more widely used in clinical practice. However, systematic comparisons with standard auscultatory BP measurement at the brachial artery are scarce. Therefore, we compared two such devices, the Boso-Mediwatch (Bosch & Sohn GmbH U. Co., Jungingen, Germany) and the Omron R3 (Omron Corp., Tokyo, Japan), with upper-arm auscultatory mercury sphygmomanometry. 2. In 20 normotensive subjects and 20 treated hypertensive subjects, the Boso-Mediwatch was applied to the left wrist by observer 1 and was compared with mercury sphygmomanometry of the right upper arm by observer 2. Each observer swapped sides and the procedure was repeated. The Boso-Mediwatch was then applied to the right wrist by observer 1 and was compared with mercury sphygmomanometry of the left upper arm by observer 2. Each observer once again swapped sides and the procedure was repeated. An identical protocol was followed for the Omron R3 in a further 20 treated hypertensive subjects and 20 normotensive subjects. 3. There were no significant differences between observers or left versus right arm for either oscillometric device or when measurements were performed by mercury sphygmomanometry. In normotensive subjects, the Boso-Mediwatch readings were higher than mercury sphygmomanometer readings, with mean differences (95% confidence intervals) of 3.9 (0.1, 7.6; P = 0.045) and 7.0 mmHg (4.7, 9.2; P < 0.001) for systolic and diastolic BP, respectively. In hypertensive subjects, the Boso-Mediwatch readings were lower for systolic BP (mean difference -6.0 mmHg (-11.6, -0.3; P = 0.04) but were higher for diastolic BP (mean difference 3.8 mmHg (1.4, 6.3; P < 0.01). 4. In normotensive subjects, the Omron R3 readings were higher, with mean differences of 3.2 (0.6, 5.8; P = 0.018) and 4.2 mmHg (1.6, 6.7; P = 0.003) for systolic and diastolic BP, respectively. In hypertensive subjects, the Omron R3 readings were lower for both systolic and diastolic BP (mean differences: -5.8 (-8.8, -2.8; P = 0.001) and -5.5 (-9.3, -1.6; P = 0.008), respectively). 5. For the Boso-Mediwatch, weighted least products analysis confirmed the presence of both fixed and proportional error for systolic BP but not for diastolic BP. For the Omron R3, fixed or proportional error was not detected for either systolic or diastolic BP. 6. These wrist oscillometric devices, although offering portability and convenience, give BP measurements that frequently differ substantially (by at least 5 mmHg) from readings simultaneously measured at the upper arm by a mercury sphygmomanometer. The magnitude and direction of differences detected are dependent on both the device used and the underlying level of BP.