Blood Pressure Measurement: Brachial Artery is the Standard Site
The brachial artery is the standard and preferred location for blood pressure measurement in clinical practice, not the radial artery. 1
Why the Brachial Artery is Preferred
The American Heart Association explicitly states that the standard location for blood pressure measurement is the upper arm, with the stethoscope at the elbow crease over the brachial artery. 1 This recommendation is based on several critical factors:
Epidemiological foundation: All major cardiovascular outcome studies establishing the relationship between blood pressure and morbidity/mortality used brachial artery measurements, making this the only site with validated prognostic significance. 1
Physiological accuracy: Systolic and diastolic pressures vary substantially throughout the arterial tree, with systolic pressure increasing and diastolic pressure decreasing in more distal arteries. 1
Problems with Radial Artery Measurements
Radial artery blood pressure measurements are not interchangeable with brachial measurements and should not be used for routine clinical blood pressure assessment:
Systolic pressure amplification: Radial systolic BP averages 5.5 mmHg higher than brachial systolic BP, with only 43% of patients having radial values within ±5 mmHg of brachial measurements. 2
Wide individual variation: 46% of patients have radial systolic BP >5 mmHg higher than brachial, 14% have differences >15 mmHg (the "Popeye phenomenon"), and 11% actually have radial systolic BP lower than brachial. 2
Calibration issues: When radial artery tonometry is used to estimate central aortic pressure, calibrating with brachial pressures (rather than radial) systematically underestimates central pulse pressure by approximately 10 mmHg, with brachial-to-radial amplification being the primary determinant of this error. 3
When Radial Measurements Might Be Considered
Radial artery assessment has extremely limited clinical applications:
Research purposes only: Radial tonometry with proper calibration can estimate central aortic pressure for research studies, but this requires specialized equipment and is not suitable for routine clinical use. 1
Doppler assistance: In patients with very faint Korotkoff sounds (e.g., muscular atrophy), a Doppler probe over the brachial artery—not radial—may help detect systolic pressure. 1
Wrist Monitors Are Not Recommended
The American Heart Association and American Society of Hypertension joint statement is unequivocal: wrist monitors are not recommended for routine clinical use. 1 This applies to both automated oscillometric devices and manual measurements at the wrist/radial artery.
Clinical Algorithm for BP Measurement Site Selection
Use the brachial artery in the upper arm for all routine clinical blood pressure measurements. 1
Position the cuff so its mid-portion lies over the brachial artery with the arm supported at heart level. 1
Measure both arms at the first visit; if difference >10 mmHg, use the arm with higher readings for subsequent measurements. 1
The only contraindication to using a specific arm is the presence of lymphedema in that limb. 1