I've written about blood pressure cuff sizes on my pregnancy website before, but recent comments suggest to me that perhaps it's time I revisit the importance of blood pressure cuff sizes.
So today, we start a small series about the importance of the proper blood pressure cuff size. This is an important issue for fat people of any gender or situation, but it's particularly vital knowledge for fat pregnant women, as we'll explore in a later post.
Why Blood Pressure Cuff Size Is Crucial
The size of your blood pressure cuff is of critical importance in getting proper medical care. If you have your BP taken with the incorrect cuff, the result will be inaccurate and you may get inappropriate treatment.
- If you use a cuff that is too small, the resulting blood pressure reading will be too high.
- If you use a cuff that is too large, the resulting blood pressure reading will be too low.
Being off in either direction can have significant health implications.
For example, if they use a too-small cuff (undercuffing) and you are incorrectly diagnosed with high blood pressure as a result, you will be given strong drugs which may have significant negative side effects, yet without any benefits to offset these risks.
On the other hand, if your blood pressure is truly high and goes undiagnosed because they are using a too-large cuff (overcuffing), it can lead to damage to your blood vessels, stroke, and heart attack.
Either way, what is most important is to have ACCURATE data on which to make medical decisions.
Using the wrong cuff size (miscuffing) means that any readings you get are meaningless. Always insist on the correct cuff size before permitting a blood pressure reading.
Miscuffing is Very Common
Research demonstrating the importance of proper cuffing has been around for more than 25 years, yet it remains one of the most common medical mistakes made with people of size.
One classic study on the importance of correct cuffing was Maxwell (Lancet, 1982). This study examined "obese" people already diagnosed with high blood pressure, then re-took their blood pressure with the correct cuff for their arm size. They found that 37%----more than ONE THIRD!----of obese hypertensives were incorrectly diagnosed and actually had normal blood pressure.
Linfors (1984) found twice the level of high blood pressure in "obese" subjects with the standard BP cuff compared to the large adult cuff. Numerous other studies since then have confirmed that using a too-small cuff significantly overestimates blood pressure in "obese" people (sometimes called "Spurious Hypertension").
Of course, cuff size is not just an issue for fat people. A recent study showed that a "standard" cuff often underestimates blood pressure in very lean people; about 80% of the "lean" pregnant women in this study had their blood pressure underestimated with a standard cuff. Thus, many skinny folks may be told that they have normal blood pressure when in fact they have hypertension and are being untreated.
Correct cuff size is an important issue for people of all sizes, but experts agree it is particularly paramount for the "obese."
Typical Cuff Sizes
Do you know what your arm measurement is? You should. Go get a tape measure right now and see what it is. Measure at the mid-point of your arm with a flexible cloth measuring tape.
Once you have measured, memorize that number so you will have it at the tip of your tongue if a cuffing question comes up at an appointment.
If you can, measure it in centimeters because that's how BP cuffs are labeled. However, if you can only measure in inches, click here to help you convert your measurement. (Or do it yourself; multiply by 2.54 to convert inches to cm; divide to go the other way.)
BP cuffs typically come in three sizes--adult, adult large, and "thigh" cuffs.
The adult size is meant for an average-sized adult. The large cuff is meant for people with larger-sized arms (like men with very muscular arms, or "overweight" and "obese" people). The so-called "thigh" cuff is an even larger cuff which is used for supersized people or people who carry a lot of extra weight in their arms.
- Regular Adult Cuff: 27-34 cm, up to 13.4 inches
- Adult Large Cuff: 35-44 cm, 13.8 inches to 17.3 inches
- "Thigh" Cuff: 45-52 cm, 17.7 inches to 20.5 inches
Research differs on exactly when the larger-sized cuff becomes necessary, but the American Academy of Family Physicians states that if the arm circumference is greater than 34 cm (13+ inches or so), a larger cuff size is definitely needed.
Although most fat people will be served by an "Adult Large" cuff, some will need an even bigger cuff. This is the unfortunately-named "thigh" cuff. It's generally used on folks with arms larger than about 17.5 inches or so. Thigh cuff ranges vary a lot, but generally they top out at about 20.5 inches.
What if your arm is larger than that? Never fear, there are cuffs available for you, but they are a special purchase and not likely to be carried by a doctor's office. See below for more information on buying your own specialty cuff or on using forearm measurements instead.
Typical Cuffing Errors
The most common errors in blood pressure cuffing are:
- Using a regular cuff when a large cuff is needed. This error is extremely common; healthcare workers should know about the importance of this but often ignore it because they don't want to go to the trouble of getting a large cuff or because they don't believe it makes that much difference
- Using a large cuff for all obese people, even when a thigh cuff is really needed. Unfortunately, many healthcare workers do not know when a thigh cuff is needed
- Using a thigh cuff for "super-obese" people, even when the upper limits of the thigh cuff are surpassed. Unfortunately, many healthcare workers are not aware of the upper limits of the larger cuffs
If you arm is even remotely borderline, it's very important that you always look at the cuff size range printed on the side of the cuff. If you are not within the range listed or are very close to its upper limits, request a different size and don't let them talk you out of it.
Common Cuffing Questions
What if my arm is close in size to the cutoffs? Which do I use?
One of the most difficult cuffing questions is what to do if your arm measurement is on the borderline between two cuff sizes. In this situation, it is difficult to know which way to err. You don't want to use the larger cuff and miss some hypertension that truly needed treating; on the other hand, you don't want to be treated for something you don't really have either.
Research shows that the error rate begins to increase as you get close to the cuff size cutoffs. Sprafka found that blood pressure cuff sizes made a significant difference in the prevalence of hypertension, even among people who were marginally large and whose arm circumferences were right around the cuff cutoff of about 13 inches. They stated:
Using a cuff one size smaller than appropriate resulted in...[an overestimation of the prevalence of hypertension of] approximately 36%.
Generally sources suggest that you should err on the side of the larger cuff if you are truly borderline because the degree of error is significantly greater when a too-small cuff is used than when a too-large cuff is used.
Do I really need to check the cuff size every time I have my BP checked?
If you need a larger cuff, you need to check that they are using the correct cuff every time you have your BP taken. Never take it for granted, even if they've always done it correctly before.
However, you don't necessarily have to check the range printed on the side of the cuff every single time unless you are near the upper limits of the cuff size. If you are in the middle of the large cuff range, just about all the large cuffs will probably work for you. Just make sure they are using a large cuff.
But if you are borderline it all, it really behooves you to check the range on the cuff. This is because BP cuff sizes are not standardized. Each maker uses its own cutoffs; the numbers listed above are merely general guidelines. Although it's unusual, it is possible to go to one office and need a large cuff, yet need a thigh cuff with the same arm size at another office.
The bottom end of cutoffs for large cuffs (just over 13") tends to be pretty standardized, but the upper end is not. It can vary by quite a bit. Therefore, if you are closer to the upper cutoff between large and thigh cuffs (or at the upper end of the thigh cuff range), you will need to check the cuff sizes printed on the cuff.
Cuff sizes are usually printed right on the side of the cuff (in centimeters, of course). If you know your arm size in cm, you can easily see if you are within the range printed on the cuff. That's why it's so important to memorize your arm size.
What about forearm readings?
In a pinch or in an emergency situation, a regular cuff can be used on your forearm; this will give a general "ballpark" picture of your BP but has not been found to be accurate to the degree really needed for most non-emergent treatment decisions.
Graves (2001) notes that while forearm blood pressure readings are possible, "These readings are not usually performed as falsely higher diastolic blood pressure readings may be obtained."
A Brazilian study (2004) found that forearm blood pressure readings with a standard cuff tended to overestimate BP readings compared to upper arm measurements with an appropriately-sized cuff. Another recent Missouri study (2008) found a similar result.
Singer (1999) found that forearm readings were within 20 mm Hg of upper arm readings in the majority of people, which is not that significant in an emergency situation with non-pregnant people. However, a difference of 20 points can make a lot of difference in treatment decisions in pregnancy, or if a healthcare provider is trying to decide whether or not to put you on high blood pressure medicine when you are borderline.
Therefore, forearm BP readings should be reserved mainly for emergencies in which a BP is needed now, or for supersized folks whose arm size is over 50 cm but who do not have quick access to a specialized cuff.
Generally speaking, forearm readings should not be relied on for regular routine readings or for making non-emergent treatment decisions, nor should they be relied on for decision-making or interventions in pregnancy unless there is a critical emergency.
Buying Consistency: If In Doubt, Get Your Own
Even if you are in the mid-range of the large cuff (which should be routinely available in every medical office or facility), you cannot always count on the doctor's office or even the hospital to have the correct size blood pressure cuff, for it to be in working order, or for medical personnel to be willing to use it. Therefore, you might want to consider purchasing your own blood pressure cuff and taking it with you to each appointment and to the hospital.
"Supersized" people or those with heavy arms may particularly want to invest in their own blood pressure cuffs. While many offices carry large cuffs, not all carry a thigh cuff. If your arm is over 17-18 inches in circumference or you weigh significantly over 300 lbs., you might especially want to consider buying an appropriately-sized cuff of your own.
Undercuffing is chronic in these groups, as few healthcare workers realize when a thigh cuff is required. Sadly, even when they know a thigh cuff is needed, many don't bother to use it, even in very large people.
If your blood pressure is borderline, if your arm is very heavy, or if you are supersized, investing in your own cuff is probably a good idea.
Nowadays, a number of internet companies offer blood pressure cuffs for sale; be sure you only buy one with the correct size cuff for you. Don't just accept that the cuff size is "large;" you need to get the exact range because of the lack of standardized cuff sizing.
In addition, if possible, choose a cuff whose accuracy has been tested and validated. Many monitors out there on the market have not had their accuracy verified. Remember, you want accurate data on which to make your treatment decisions.
The internet company, Amplestuff, sells blood pressure cuffs in varying sizes (including sizes for arms over 20 inches). It is one of the only good sources for the very largest of cuffs. These cuffs attach easily to the blood pressure devices in most offices, and then accuracy is always at your fingertips.
Blood pressure cuff size is a critical issue in healthcare for people of size, yet despite years of research on the issue, miscuffing is quite common. Some sources suggest that up to 1 in 3 BP readings are miscuffed, and that the "obese" are particularly at risk for miscuffing issues.
If your arm is over about 13 inches, you need to ask about cuff size EVERY time you get your blood pressure taken. Even if the office routinely uses the larger cuff with you, you still need to verify cuff size; don't ever take it for granted that they are using the correct cuff size.
Blood pressure is a very important health issue. If you truly have hypertension, it really does need to be treated. However, these decisions need to be made on the basis of accurate data, and research is very clear that miscuffing is still a significant issue for fat folk.
Coming soon: Your chance to share your BP miscuffing stories, the heightened importance of BP cuff issues during pregnancy, and how to deal proactively with resistance from healthcare workers.