Question:

I have been reading several articles mentioning that a standard size cuff on a large arm can yield a false higher reading and a thin arm can yield a false lower reading.

How accurate are these findings as blood pressure varies under various circumstances. I would have thought a large arm could give a false low readng as the brachial artery would be well protected by layers of fat. Conversely, a thin arm could yield a false high reading as thin arms have less padding and the reading would be increased by the isometric tension created.

So what is the verdict out there or is it subject to controversy. And what is the circumference of the arm sizes in these studies?

Answer:

The American Heart Association recommends the following cuff sizes for use with sphygmomanometers (blood pressure monitors):

• Arm circumference 22-36 cm:  small adult (12 x 22 cm)
• Arm circumference 27-34 cm: adult (16 x 30 cm)
• Arm circumference 35-44 cm:  large adult (16 x 36 cm)
• Arm circumference 45-52 cm:  adult thigh (16 x 42 cm)

Using a cuff that is too small (circumference too short) will cause a falsely high reading, because the arm has to be compressed more to collapse the artery.  A cuff that is too large can give a reading that is too low, although that does not often occur.

The error rate is less with using a cuff that is too large.  The most common error made is using a cuff that is too small (circumference too short).

For more information:

Go to the High Blood Pressure health topic.