If a blood pressure cuff is too small, how will the affect blood pressure? Too large?

• A. Too small - falsely elevated; Too large - falsely decreased
• B. Too large - falsely decreased; Too small - falsely elevated
• C. Both sizes affect readings equally
• D. No effect

Answer: (D)

Cuff size directly affects how the cuff compresses the arm and occludes the brachial artery, so readings can be biased if the size isn’t appropriate. When the cuff is too small, it requires more pressure to stop blood flow, which makes both systolic and diastolic values read higher than the true values—a falsely elevated reading. If the cuff is too large, pressure is distributed over a bigger area and the artery isn’t occluded as effectively at the same pressures, leading to lower readings that underestimate the true BP. So the accurate principle is that a too-small cuff yields a falsely elevated reading, while a too-large cuff yields a falsely decreased reading. In practice, choose a cuff width about 40% of the arm circumference and ensure the cuff fully encircles the arm with the bladder positioned over the brachial artery.