Using the correct blood pressure (BP) cuff size is important to get an accurate measurement. Too large and the BP reading will be falsely low; too small and the reading will be falsely high.
A recent study published in JAMA Internal Medicine looked at the effect of BP cuff sizes on automated BP readings.
- Question: What is the effect of using a regular size BP cuff regardless of an individual’s mid-upper arm circumference on BP readings when using an automated device?
- Findings: In this randomized crossover trial of 195 community-dwelling adults with a wide range of mid-arm circumferences, use of a regular BP cuff resulted in a 3.6-mmHg lower systolic BP reading among individuals requiring a small BP cuff. In contrast, among individuals requiring a large or extralarge BP cuff, use of a regular BP cuff resulted in 4.8-mmHg and 19.5-mmHg higher systolic BP
readings, respectively. - Meaning: Using a regular BP cuff size for all individuals regardless of arm size resulted in strikingly inaccurate BP readings with an automated device; a renewed emphasis on individualized BP cuff selection is warranted, particularly in individuals with larger arm sizes.
The most precise way to choose the correct BP cuff size is to measure the circumference of the arm and match it with the correct size on a sizing chart (see example below).
- The circumference of the cuff should be measured midway between the acromion and the olecranon.
- The bladder of the cuff (see image, above right) should be ~80% of the arm circumference and the width of the cuff should be ~40% of the arm circumference.
Other pearls for accurate BP measurement:
- No caffeine or exercise 30 minutes before measurement
- Sit alone (without talking) for at least 5 minutes prior to measurement
- Keep feet flat on the floor and legs uncrossed
- Let arm rest at heart height (i.e., patient should not be holding their arm up)
- Keep the patient’s back supported
- Tell patients to go pee (seriously—having a full bladder can increase BP by 10-15 mmHg!)