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How to assess mean blood pressure properly at the brachial artery level

Bos, Willem JWa; Verrij, Elisabetha; Vincent, Hieronymus Ha; Westerhof, Berend Eb; Parati, Gianfrancoc; van Montfrans, Gert Ad

doi: 10.1097/HJH.0b013e32803fb621
Original papers: Blood pressure measurement
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Objectives Mean arterial pressure at the upper arm is traditionally calculated by adding one-third of the pulse pressure to the diastolic pressure. We questioned the general validity of this formula.

Methods We used previously recorded resting intrabrachial pressure and Riva–Rocci Korotkoff blood pressure measurements in 57 subjects (study A) and 24-h intra-arterial recordings obtained in 22 ambulant subjects (study B).

Results In study A the intra-arterially measured ‘real’ mean pressure was found at 39.5 ± 2.5% of pulse pressure above diastolic pressure, namely at a level higher than the expected 33.3% of pulse pressure, in all individuals. Results were not related to age, blood pressure, pulse pressure or heart rate levels. Mean pressure calculated with the traditional one-third rule therefore underestimated ‘real’ mean pressure by 5.0 ± 2.3 mmHg (P < 0.01) when calculated from intra-arterial pressure readings, and by 4.9 ± 5.3 mmHg (P < 0.01) when calculated from Riva–Rocci Korotkoff readings. In study B we showed activity-related variations in the relative level of the ‘real’ mean pressure, which increased by 1.8 ± 1.4% (P < 0.01) during sleep, and decreased by 0.5 ± 0.9% during walking (P < 0.05) and by 0.8 ± 1.3% during cycling (P < 0.01).

Conclusion The mean pressure at the upper arm is underestimated when calculated using the traditional formula of adding one-third of the pulse pressure to the diastolic pressure. This underestimation can be avoided by adding 40% of pulse pressure to the diastolic pressure. The proposed approach needs to be validated through larger scale studies.

aDepartment of Internal Medicine, St Antonius Hospital, Nieuwegein, The Netherlands

bBMEye, Amsterdam, The Netherlands

cDepartment of Clinical Medicine, Prevention and Applied Biotechnology, University of Milano-Bicocca and Istituto Auxologico Italiano, Milan, Italy

dDepartment of Internal Medicine, Academic Medical Centre, Amsterdam, The Netherlands

Received 11 July, 2006

Revised 9 December, 2006

Accepted 12 December, 2006

Correspondence and requests for reprints to Willem J.W. Bos, Department of Internal Medicine, St Antonius Hospital, Koekoekslaan 1, 3435 CM Nieuwegein, The Netherlands Tel: +31 30 6099111; fax: +31 30 6056357; e-mail: w.bos@antonius.net

© 2007 Lippincott Williams & Wilkins, Inc.