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

J Hypertens. 2007 Apr;25(4):751-5. doi: 10.1097/HJH.0b013e32803fb621.

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.

MeSH terms

  • Adult
  • Age Factors
  • Aged
  • Aged, 80 and over
  • Arm / blood supply
  • Blood Pressure*
  • Brachial Artery / physiopathology*
  • Case-Control Studies
  • Circadian Rhythm
  • Female
  • Heart Rate
  • Humans
  • Hypertension / physiopathology
  • Male
  • Middle Aged
  • Reproducibility of Results
  • Research Design
  • Vasodilation