If the blood pressure cuff is too large, the reading is typically:

• A. Inaccurate low blood pressure reading
• B. Inaccurate high blood pressure reading
• C. Accurate reading
• D. No reading

Answer: (A)

Cuff size directly affects how pressure translates to arterial compression. If the cuff is too large for the arm, the bladder spreads the force over a wider area and doesn’t compress the brachial artery as effectively at the same cuff pressure. As a result, the artery isn’t occluded as it should be, and the reading tends to fall short of the true systolic and diastolic pressures. So you typically get an inaccurately low blood pressure reading. To avoid this, use a cuff whose width is about 40% of the arm circumference and whose bladder length covers roughly 80% of the arm.