Comparison of two oscillometric blood pressure monitors in subjects with atrial fibrillation

OBJECTIVE: To compare blood pressure readings obtained with two commonly used oscillometric monitors: Omron HEM 711 AC (OM) and Welch-Allyn 52000 series NIBP/oximeter (WA) with mercury sphygmomanometers (Merc) in subjects with atrial fibrillation. METHODS: We recruited 51 hemodynamically stable subjects with atrial fibrillation. Fifty four subjects in normal sinus rhythm served as controls. Supine blood pressure readings in each arm were recorded simultaneously using one monitor and Merc. The second monitor then replaced the first and readings were repeated. Merc was then switched to the opposite arm, and both monitors retested. Apical heart rates were ascertained with a stethoscope. We used the averaged, same arm Merc readings as "gold standard". RESULTS: Automated blood pressure readings were obtained in all control subjects and in all but three of those with atrial fibrillation. Both monitors, and operators, noted a difference between apical and radial/brachial pulse rates: apical-recorded: Merc 6.1 + or - 15.0; OM 5.5 + or - 13.7; WA 10.0 + or - 21.2 beats per minute. Both monitors were accurate in controls: over 90% of readings were within 10 mmHg of averaged Merc, and both achieved European Hypertension Society standards. In subjects with atrial fibrillation, about one quarter of all oscillometric readings differed from Merc by more than 10 mmHg. Both falsely high and falsely low readings occurred, some up to 30 mmHg. There was no relation between accuracy and heart rate. CONCLUSIONS: Single blood pressure readings, taken with oscillometric monitors in subjects with atrial fibrillation differ, often markedly, from those taken manually. Health care professionals should record multiple readings manually, using validated instruments when making therapeutic decisions.