Heart Education Awareness Resource and Training through eLearning (HEARTe)
Measuring BP in practice – 2
The upper arm is used to measure BP because it reflects the central aortic pressure. It is good practice to check BP in both arms, to identify any significant variation in measurements. Inside the cuff is the bladder, which requires to be the correct size to measure the BP correctly.
arm circumferences less than 23 cm should be measured using the small cuff size.
arm circumferences between 23 cm and 33 cm should be measured using the medium cuff size.
arm circumferences between 33 cm and 50 cm should be measured using the large cuff size.
If you use a too small cuff, you will obtain a falsely high reading, possibly by as much as 10mmHg (and this could be equivalent to one tablet to treat high BP if a too tight cuff was consistently used!)
If you use too large a cuff, you will obtain a falsely low reading, possibly by as much as 10mmHg (and you might underestimate the patient’s risk of having a stroke or heart attack by about 40%! DON’T DO IT!)
Additional Information
There is guidance to suggest that when considering a diagnosis of hypertension, BP should be measured in both arms. If the difference in readings between arms is more than 20 mmHg, these measurements should be repeated. If the difference in readings between arms remains more than 20 mmHg on the second measurement, measure subsequent blood pressures in the arm with the higher reading [NICE 2011]. You should check your local NHS Board for guidance on good practice.
When measuring BP in people with symptoms of postural hypotension (falls or postural dizziness), it is suggested that the person should be positioned either supine or seated and, thereafter, the BP measured again with the person standing for at least 1 minute prior to measurement [NICE 2004, amended 2011]. You should check this with your local NHS Board guidance.
