What is the accuracy of blood pressure (BP) measurements using a cuff on the forearm versus the upper arm?

From the Guidelines

Upper arm measurements are the gold standard for blood pressure readings and should be used whenever possible, as they provide more accurate results compared to forearm measurements. When using the upper arm, the cuff should be placed about 1 inch above the bend of the elbow with the bottom edge of the cuff at heart level, and the bladder of the cuff should cover at least 80% of the arm circumference snugly 1. Forearm measurements tend to produce systolic readings that are 3-13 mmHg higher and diastolic readings that are 5-10 mmHg higher than upper arm readings.

The most recent and highest quality study, published in 2021, emphasizes the importance of measuring blood pressure in the seated position, with feet on the floor and arm supported at heart level, after 5 min of rest, and using an appropriate cuff size for the upper-arm circumference 1. The American College of Cardiology/American Heart Association task force on clinical practice guidelines also recommends using a validated blood pressure measurement device, supporting the patient's arm, and positioning the middle of the cuff on the patient's upper arm at the level of the right atrium 1.

Key considerations for accurate blood pressure measurements include:

• Using a validated blood pressure measurement device
• Supporting the patient's arm
• Positioning the cuff correctly
• Using the correct cuff size
• Taking multiple readings and averaging them
• Documenting the readings accurately

In cases where upper arm measurement is not possible, such as in patients with very large arm circumference, those wearing bulky clothing that cannot be removed, or those with upper arm injuries, forearm measurements may be used, but the arm should be supported at heart level, and the healthcare provider should note that the reading was taken on the forearm. However, upper arm measurements remain the preferred method due to their higher accuracy and reliability.

From the Research

BP Cuff Placement Accuracy

• The accuracy of blood pressure (BP) measurements can be affected by the placement of the cuff on the arm, with incorrect placement potentially leading to inaccurate readings 2, 3.
• Studies have shown that the placement of the cuff on the upper arm, rather than the forearm, is recommended for accurate BP measurement 2, 3.
• The American Heart Association recommends that the cuff width should encircle 40% of the arm circumference and the cuff length should be at least 80-100% of the arm circumference 4.

Cuff Size and Accuracy

• The size of the cuff used can also impact the accuracy of BP measurements, with a cuff that is too small potentially leading to overestimation of BP 5, 3.
• A study found that a specially designed wide-range cuff can provide accurate measurements regardless of the position of the cuff on the arm 3.
• The use of a properly sized cuff is critical for obtaining accurate BP measurements, and incorrect cuff sizing can lead to systematic errors in BP measurement 5, 3.

Comparison of Cuff Positions

• A study compared the accuracy of BP measurements taken with the cuff placed on the upper arm in different positions, including the standard position, medial position, lateral position, and contralateral position 2.
• The study found that there were no significant differences in non-invasive brachial BP among the four cuff positions, and the mean BP differences between incorrect and standard cuff positions were within 1.0 mm Hg 2.
• Another study found that incorrect cuff positioning introduced a systematic overestimation of auscultatory BP when the cuff was too small in relation to arm circumference, but not when it was correctly sized 3.