Why is cuff size critical?

• A. An undersized cuff overestimates BP; an oversized cuff underestimates BP
• B. Cuff size has no effect on BP readings
• C. A cuff size only affects diastolic measurement
• D. The cuff size only changes measurement time

Answer: (A)

Cuff size has a direct effect on the accuracy of a blood pressure reading. If the cuff is too small (undersized), you must inflate to a higher pressure to occlude the brachial artery, which makes both systolic and diastolic readings appear higher than they truly are. If the cuff is too large (oversized), the artery isn’t occluded as effectively, so you obtain lower readings. This predictable bias is why the correct statement is that an undersized cuff overestimates BP and an oversized cuff underestimates BP. For best results, choose a cuff width about 40% of the arm circumference and ensure the bladder covers most of the arm.