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J Hypertens. 2007 Apr;25(4):751-5.

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

Author information

1
Department of Internal Medicine, St Antonius Hospital, Nieuwegein, The Netherlands. w.bos@antonius.net

Abstract

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.

PMID:
17351365
DOI:
10.1097/HJH.0b013e32803fb621
[Indexed for MEDLINE]

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