A Class 1 (20-30 mmHg) compression sleeve gives a pressure of:
- A. 30 mmHg pressure distally and 20 mmHg proximally
- B. 20 mmHg distally and 30 mmHg proximally
- C. 20-30 mmHg somewhere along the garment
- D. 20 mmHg distally at the smallest circumference in the range listed for that point and 30 mmHg at the largest circumference
How do graduated compression garments really work? Even seasoned professionals may be stumped by the above exam question, because the science behind compression garments is solemnly explained. The answer is D, the pressure a patient receives within the 20-30 mmHg range is dependent on their measurements for that point. Did you answer correctly? The theory of compression is relatively simple. For ready-made sleeves, the compression is usually stated as a compression class, such as Class 1 and also as a range of compression, such as 20-30 mmHg. In order to fit the patient within the range of compression, manufacturers also give a range of sizes for three or more points along the arm. For instance, a medium compression Class 1 sleeve would have a wrist measurement between 16.5 cm and 21.5 cm.
However, size ranges don’t tell you when a patient’s specific measurement creates a problem. For example, when the wrist circumference is at the smaller end of the range and then forearm circumference is at the upper end of its range, pressure at the forearm could exceed the pressure on the wrist, potentially creating a tourniquet effect at the forearm. The problem is less likely to occur if the patient is in the middle range in all areas. When fitting a patient for a garment, how does a therapist determine whether a garment will work for the patient without knowing the approximate pressure at each measuring point? Currently, this is determined by trial and error or by fitting a patient for a custom garment.
The practice of compression varies from the theory of compression simply because there isn’t a single approach to determining the best range of compression based on the severity of the patient’s edema. For instance, in the United States, 20-30 mmHg is standard compression for prevention and minimal edema and 30-40 mmHg is standard for moderate to severe edema. In the UK on the other hand, 15-20 mmHg is standard for prevention and minimal edema and 20-30 mmHg is standard for moderate to severe edema, with 30-40 mmHg being rarely used. These varied recommendations are based on practice experience, as no trustable studies exist to determine the best range of compression based on a patient’s edema.
Due to the conflict in the theory of compression versus the practice of compression, it is best to fit patients by delivered compression based on the patient’s severity of lymphedema, instead of fitting by the sizing within a range of compression. For that purpose, as the Chief Medical Officer and Vice President of LympheDIVAs, I have developed the Fitter’s Aid technology to allow therapists and fitters to determine approximate delivered pressure in any of our garments based on their patient’s specific measurements.
My background isn’t in compression garments; I had been trained as an Internist and Rheumatologist but had worked as a bench immunochemist at Harvard and the National Institute of Health. It wasn’t until my daughter Rachel, who had founded LympheDIVAs, asked me to take over the company shortly before she died, that I started my adventure into lymphedema and the physics of compression garments.
When I first took over the company, we would receive calls with questions on how to determine sizing for a patient’s particular arm. I didn’t want to rely on the sizing chart ranges to answer these critical questions; instead I determined that a better approach would be to measure the delivered compression for a given circumference in all of our garments. I obtained an instrument to measure pressure and dived headfirst into the theory of compression. I determined that at the smallest circumference of the listed compression range for the size, the compression is as it’s lowest for the class, and at the largest circumference, the compression is at the highest listed for the class. The circumference versus compression curve starts out steep and tends to flatten out because of Laplace’s law. The fact that the sleeve is a medical garment assumes that as you move proximally along the 3-5 measuring points along the arm, there is a decrease in pressure, but the designation of 20-30 mmHg does not specifically say anything about pressures proximal to the most distal point.
With the Fitter’s Aid, a therapist is able to fit a patient based on delivered compression at each point. A sleeve is determined to be medically correct for the patient if the wrist pressure is sufficient within the compression range necessary for the patient’s edema, and then pressures going proximally decrease by at least 4-5 mmHg for patient’s actively managing edema. With this knowledge, any of our 6 size and compression combinations can be virtually fit to determine the best pressure irrespective of the size and compression class. The only critical information to fitting the garment is the distal pressure and graduated compression after that.
One caveat with respect to pressure; all pressures are determined by using a perfect circle standard. However, the cross section of a limb is never a perfect circle, and because of Laplace’s law, wherever it protrudes, the pressure is higher.
All compression garments are manufactured using either flat knit or circular knit. Most ready-made sleeves are seamless circular knit, while most custom sleeves are seamed and flat knit. There are many aspects that are shared between these two techniques and fewer that differentiate them. The term most heard in separating circular knit from flat knit is “containment.” This is not a medical term, but generally means that because flat knit is stiffer it can “bridge” fat folds, while the circular knit follows the skin. However, there is no research showing any clinical advantage of one type over the other. The other discussion point used to differentiate flat knit from circular knit, is that flat knit with its heavier fabric, is more like a short stretch bandage and performs a pumping action when worn. This is a misconception, while the flat knit is thicker, is it not like a short stretch bandage and the compression profile is often nearly identical to that of a circular knit.
Just like with ready-made garments - a range of compression classifies custom-made sleeves. If a custom manufacturer knows the properties of the textile, and the circumference of the arm being fitted for that custom sleeve, then there should be a precise number, such as 25 mmHg, provided for each measuring point. Unless a therapist has access to equipment to measure the pressures of the custom sleeve, they are often flying blind with respect to what pressures are along the garment regardless of whether the garment is flat knit, circular knit, ready-made or custom.
The current practice of fitting a patient for a compression garment varies based on the therapist. There are a few factors to be considered when fitting a patient for a compression garment. First is compression; is the patient getting the necessary pressure at all points on their arm to manage the severity of their edema? Depending on the severity of edema and the patient’s measurements this would vary between flat knit, circular knit, ready-made and custom-made garments, based on the patient’s individual needs. As garment tightness is often considered an uncomfortable side effect of compression sleeves it may be best to start with the lowest compression needed to manage the severity of the patient’s edema and only move to a higher pressure garment if necessary. The only way to determine if a garment provides the lowest range of compression for a patient is to know the delivered compression for all given measurement points along the arm. It is a matter of determining if a compression garment with the range 20-30 mmHg offers a starting wrist compression of 20 mmHg, 25 mmHg or 30 mmHg.
Second factor in determining the best compression garment for a patient is compliance; is the patient likely to wear the garment? How does the garment look and how does it make the patient feel? A compression garment, no matter how well made and fitted, will not work for the patient if it is not worn. Sleeves that are uncomfortable or produce a negative response are unlikely to be worn and can then offer no positive compression benefit to the patient. With so many garments options, it is important to value the patient’s comfort as highly as the medical pressure the garment delivers. A garment that is comfortable and has an attractive appearance is more likely to be worn and can therefore be more medically effective for the patient.
The final factor in determining the best compression garment for a patient is cost; can the patient afford the optimal garment for their treatment? The cost difference between custom and ready-made sleeves vary greatly. If cost is enough a factor for the patient to not purchase the garment, and therefore not be able to wear it, then alternative more cost-effective options must be considered. The expense can be so high that it not only keeps the patient from purchasing the garment, but also keeps the patient from returning to the therapist for continued treatment.
There isn’t a one-size fits all solution to fit each individual’s compression, compliance and cost needs. Once compression levels of garment are determined to perform for a patient clinically, then therapists should approach their decision by considering which garment is the patient will actually wear and is cost-effective. Compression, compliance and cost should be the main determining factors in finding the right garment for each patient’s individual needs.