The impact of arm position and pulse pressure on the validation of a wrist-cuff blood pressure measurement device in a high risk population

Despite the increasing popularity of blood pressure (BP) wrist monitors for self-BP measurement at home, device validation and the effect of arm position remains an issue. This study focused on the validation of the Omron HEM-609 wrist BP device, including an evaluation of the impact of arm position and pulse pressure on BP measurement validation. Fifty patients at high risk for cardiovascular disease were selected (age 65 +/- 10 years). Each patient had two measurements with a mercury sphygmomanometer and three measurements with the wrist BP device (wrist at the heart level while the horizontal arm supported [HORIZONTAL], hand supported on the opposite shoulder [SHOULDER], and elbow placed on a desk [DESK]), in random order. The achieved systolic BP (SBP) and diastolic BP (DBP) wrist-cuff readings were compared to the mercury device and the frequencies of the readings within 5, 10, and 15 mmHg of the gold standard were computed and compared with the British Hypertension Society (BHS) and Association for the Advancement of Medical Instrumentation (AAMI) protocols. The results showed while SBP readings with HORIZONTAL and SHOULDER positions were significantly different from the mercury device (mean difference = 7.1 and 13.3 mmHg, respectively; P < 0.05), the DESK position created the closest reading to mercury (mean difference = 3.8, P > 0.1). Approximately 71% of SBP readings with the DESK position were within +/-10 mmHg, whereas it was 62.5% and 34% for HORIZONTAL and SHOULDER positions, respectively. Wrist DBP attained category D with BHS criteria with all three arm positions. Bland-Altman plots illustrated that the wrist monitor systematically underestimated SBP and DBP values. However a reading adjustment of 5 and 10 mmHg for SBP and DBP (DESK position) resulted in improvement with 75% and 77% of the readings being within 10 mmHg (grade B), respectively. AAMI criteria were not fulfilled due to heterogeneity. The findings also showed that the mismatch between the mercury and wrist-cuff systolic BP readings was directly associated with pulse pressure. In conclusion the DESK position produces the most accurate readings when compared to the mercury device. Although wrist BP measurement may underestimate BP measured compared to a mercury device, an adjustment by 5 and 10 mmHg for SBP and DBP, respectively, creates a valid result with the DESK position. Nevertheless, considering the observed variations and the possible impact of arterial stiffness, individual clinical validation is recommended.