Cuff size matters

21 April 2022

One cuff size does not fit all when it comes to measuring your blood pressure, and choosing a cuff that doesn’t fit you properly will lead to inaccurate readings. A cuff size that is too small will make your blood pressure reading too high, and a cuff that is too large will make it too low. New research from the United States has put figures to the facts using modern blood pressure machines, as opposed to the old mercury sphygmomanometers which this knowledge was derived from. It shows the wrong cuff size could lead to a reading that is out by up to 5mmHg.

Study author Tammy M. Brady, medical director of the Pediatric Hypertension Program at Johns Hopkins University in Baltimore, explained: "While clinical practice guidelines highlight the importance of individualized blood pressure cuff selection for measuring blood pressure, most of the research looking at cuff size on measurement accuracy was done using mercury sphygmomanometers, which are blood pressure monitors in which the cuff is manually inflated and blood pressure is determined by listening for arterial sounds through a stethoscope. We looked at how cuff size impacts blood pressure readings with today's widely used automated blood pressure monitors."

Dr Brady explained "Accurate blood pressure measurement depends on... individualized selection of cuff size, which should be based on the measured mid-arm circumference.”

The researchers analysed blood pressure readings from 165 adults taken in one setting. Each person had their blood pressure measured three times using a regular adult-sized cuff, and again three times using a cuff that was the appropriate size for them. They were asked to walk a certain distance before each set of readings, so they hadn’t been resting for more time before the second set.

Other factors that can affect readings were also considered, for example, they rested for 5 minutes after the cuff was placed, they did not speak during the measurements, didn’t use a smart phone and the room was kept quiet.

The researchers found:

• Among those who required a small adult cuff, a regular-sized cuff resulted in lower blood pressure readings, including an average of 3.8mmHg lower systolic reading and 1.5mmHg lower diastolic reading.
• Among those who required a large or extra-large adult cuff, a regular-sized cuff was associated with higher readings, including an average 4.8mmHg systolic reading and 19.7mmHg higher diastolic reading, respectively.

Accurate blood pressure readings are important because a reading that’s too high could lead to GPs prescribing blood pressure medicines that are not necessary, or not prescribing them when they are.

This preliminary research which was due to be presented at the American Heart Association's Epidemiology, Prevention, Lifestyle & Cardiometabolic Health Conference 2022 from 1-4 March 2022, and is currently unpublished.

Nirmala Markhandu, Hypertension Nurse Specialist at Bloor Pressure UK says: “It’s well known that cuff size is very important in measuring blood pressure accurately. This study highlights the fact clearly. It shows the importance of choosing the right size, both for health professionals in clinical settings, and the public when buying home monitors.”

You can read more about sources of error in blood pressure readings and how to choose a monitor in the Summer issue of our magazine, Positive Pressure. You can also read more about choosing a home monitor on our website.

Source: American Heart Association
Full bibliographic information
One Size Does Not Fit All: Impact Of Using A Regular Cuff For All Blood Pressure Measurements
Authors: Tammy M Brady, John Hopkins University, Baltimore, MD; Jeanne Charleston, Johns Hopkins Univ ProHealth, Baltimore, MD; Junichi Ishigami, Johns Hopkins Univ, Baltimore, MD; Gregory P Prokopowicz, Johns Hopkins Hospital, Baltimore, MD; Edgar R Miller II, Johns Hopkins Medical Institutions, Baltimore, MD; Kunihiro Matsushita, JOHN HOPKINS UNIVERSITY, Baltimore, MD; Lawrence J Appel, Johns Hopkins Medical Institutions, Baltimore, MD