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A Blood Pressure Cuff Must Be The Right Size...
Or a large error may be introduced. Is improper blood pressure cuff size a common error? You bet it is. You may need a large cuff if your arm size is 11 or 12 inches. By 13 inches you do need a large cuff. First, what is a blood pressure cuff? An essential part of measuring a blood pressure is the compression of the artery so that no blood flows through. The operator then listens to the sounds of the blood being pushed through as the compression is gradually reduced. An inflatable bladder encased in a cloth sleeve, which is wrapped around the upper arm, accomplishes the compression. This part is called the cuff. Its critical characteristic is its size. The error that is introduced by too small a blood pressure cuff is a reading that is too high and the error can be 50 mm and this is not rare. Just think of it as the little cuff having to work much too hard to compress the artery and thus generates an artificially elevated reading. This can lead to incorrect diagnosis and/or excess treatment. Too large a cuff introduces the opposite error, an artificially low reading but not nearly the magnitude of the too small cuff error. How to measure your arm: Using a flexible cloth (not metal) tape, measure the circumference of your upper right arm about the middle. This is in inches or centimeters and it's a good idea to know both. Memorize it. This is just one way your reading can be falsely elevated. Another source of fairly large error is the false elevation occurring when someone else takes your blood pressure This is called White-coat Hypertension and is discussed more on the Homepage? The only way to eliminate this possible large error is to learn how to take your own pressure at How to Take Blood Pressure
How prevalent is the problem? It is difficult to put exact numbers on it but studies show a possibility that 1 of 3 readings are not taken with the ideal size cuff. Obviously, those with larger arms are the most likely to suffer this mistake. Heavy women in pregnancy must be especially vigilant.
Why does this happen so often? It might mainly be due to a lack of emphasis on this factor in the training of medical personnel. This leads to a tendency to neglect cuff size in the everyday work environment, both office and hospital. What sizes are generally in use? For adults it is the Adult (27-34 cm), the Large (35-44cm) and the Thigh (45-52cm). These ranges are approximate guidelines only. Be aware there is no standardization that I know of for blood pressure cuff size. The manufacturer is free to design for the size range of their choice but should label their product prominently. A little tip: Convert centimeters to inches by dividing by 2.54 and inches to centimeters by multiplying by 2.54. What size do you need? Use only a blood pressure cuff that is designed for your size arm. Your arm size measured around the middle of the upper arm should fall in the middle 75% of the cuff’s range. When your size falls close to the upper and lower end of the cuff’s range you can see error begin to occur. At this point you might need to step up to the next size. Obviously being near the lower end of the range requires stepping down but this is not as critical. The D-ring: You will see this feature touted here and there and admittedly it is nice, making it easier to put the cuff on with one hand. But the odds are good that the cuff you want doesn't have one. Here is an easy way to get around it: With the help of someone else affix the cuff to your right arm exactly the way you want it. Then mark it. Slide it off and slide it back on and it is always ready for you. If it becomes undone for any reason just put the surfaces together exactly where you marked it and slide it on! Easy as pie. Doctor’s Practical Guide: As Socrates said, “First, know thy arm size” or was it “First, know thyself”? Was it even Socrates? Measure your arm and burn its size into your brain so that you always know it. What should you do? If you ask whomever is taking your blood pressure what is the range of the cuff they may not even know specifically. But ask you must and make sure your arm size falls in the middle 75% of the cuff range. It should be printed right on the cuff. If you have a large arm, 11 to 13 inches (28 to 33 cm.), you might need a large cuff. For over 13 inches you do need a large cuff. You might consider buying and carrying your own cuff in case the proper size is unavailable. Don’t be afraid to discuss it with your health care providers. They should be open to this and if not, consider changing. There is further discusssion of cuffs at this sister page Blood Pressure Cuffs Lastly, the final (and best) line of defense is taking your own readings with your own blood pressure cuff. See how and why at How to Take Blood Pressure
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