University of Southern California Mrs. T.H. Chan Division of Occupational Science and Occupational Therapy
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Injury and Friction

The purpose of our skin is to protect us from illness and injury, but, as we all know, it is all too easy to damage the skin. Scrapes, cuts, burns, blisters, rashes and pressure ulcers (which means the same thing as "pressure sores" or "bedsores") are just some of the forms of harm that can happen to skin. Although any wound can possibly lead to pain, swelling, blood loss and/or infection, skin damage can also be the source of a pressure ulcer, especially for people with spinal cord injuries. This article will explain how either injury or friction, that is, rubbing or scraping, can lead to a pressure ulcer.

Injury. The number one cause of pressure ulcers is, as you might guess, pressure; keeping steady pressure on any one part of the body forces blood out of the area 1. Since blood carries oxygen to all the body's cells, the area that is under pressure can experience ischemia, that is, tissue damage due to oxygen loss, and ischemia is the start of a pressure ulcer 2. But tissue damage can come from a number of sources, such as a bad bump, or a cut that gets infected. Several of our study participants got pressure ulcers from injuries; for example, Aaron transported himself up and down stairs on his buttocks, and during one trip, he got a splinter without realizing it. It got infected, and led to a pressure ulcer that eventually needed surgery. Charlie got pressure ulcers after injuries caused by a scrape while transferring, a fall from his wheelchair during a wheelchair marathon and a fall from a hospital bed that had a loose railing. And Steve scraped himself on the tire of his wheelchair, causing a small sore that he was able to treat himself at home with medication left over from a previously healed pressure ulcer. Another study participant, Billy, has gotten a pressure ulcer from falling out of a wheelchair that was in bad shape, then dragging himself across the floor to call for help. Infection in a cut or scrape can be particularly dangerous because it can be going on beneath the surface of the skin, where it can't be seen. Billy has also gotten a pressure ulcer after a bump that caused an infection, which he described this way:

Sometimes, like transferring or going out, I bump my body, right? Bump it. Then I look at it and touch it - "Oh, it's nothing." It's like a little red spot, and I let it go away. ... The next thing you know, it's like a little pimple. And I clean it and pop it, and I clean it and it's cool. Next thing you know, the inside is so infected that pus starts coming out. That's how I get my pressure ulcers, from the inside, 'cause I don't know [it's infected].

Friction. As explained earlier, friction means rubbing or scraping. Another way to explain friction is that it is when two surfaces move in opposite directions - and one of the "surfaces" is your skin! It can commonly happen during transfers 1. For example, while Judy, one of our study participants, was in the hospital, she was transferred with a sliding board, but the board was jabbed frequently in the same part of her left buttock. This combination of friction and bumping caused an injury which led to a pressure ulcer.

But there are other forms of friction that cause pressure ulcers. For example, when clothing or bedding is not smooth, the wrinkles that are formed create a raised or bumpy surface that rubs against the skin. For example, Judy got two pressure ulcers when she was out of town for a few weeks and new care attendants, who were not used to smoothing out the loose-fitting dresses that she likes to wear, let her sit on wrinkles. And Billy has gotten pressure ulcers from sitting on pencils that his young nieces left lying on the furniture he sat on, and when he sat on the thick stitching of the back pockets of his jeans.

Friction can also come from frequent rubbing on the same spot of your body, like when our study participant Odel got a pressure ulcer on his heel from a combination of wearing a pair of dress shoes that were not well-padded, and from rubbing the same heel against his sheets at night when he experienced spasms.

There's another page in this guide that explains how shearing, which is kind of a combination of pressure and friction, can also damage the skin and create a pressure ulcer. That section is titled "Pressure and Shearing".

So what should you do after injuring your skin? The first step is to apply "first aid," such as cleaning the wound and putting on a bandage, possibly with a very mild antibiotic or saline solution. You need to be careful about what kind of antibiotic you put on the wound, because some over-the-counter brands that you can buy at a supermarket or drugstore, like alcohol, hydrogen peroxide or Bactine®, are too harsh for sensitive skin as it heals. Your doctor can tell you what kind of antibiotic is best for an injury; in fact, your second step should be to consult with your doctor, either over the phone or, preferably, in person. If the doctor can examine the wound, he or she will have a better idea whether it looks like it might develop into something worse. Even if you just talk to your doctor (or their physician assistant) on the phone, that will provide you with good advice for taking care of the wound. Your next step is to watch the area carefully for several days, even a few weeks; it will be easy to look at your injury as part of your daily skin checks. If the color of the area changes, or if the temperature of the skin changes (for instance, if you notice that it starts to feel warm or hot to the touch), or if it swells, go to your doctor right away. These are all signs that an infection is forming.

Of course, even better than reacting to an injury after it happens is preventing one from happening at all. If you take part in sports, wear the right kind of protective gear, such as gloves (which might also be useful if you go long distances in a manual wheelchair). Make sure that harder surfaces your skin rubs against regularly, like shoes, braces, splints, or wheelchairs, are properly padded. If you bump into the edges of furniture in your home or office frequently, you might want to pad the edges. If you experience spasms, talk to your doctor or an occupational therapist about whether you should get splints to prevent friction, particularly overnight.

The more you know about what causes pressure ulcers, the better your chances of preventing them. Injury or friction can damage your skin, but taking care of your skin afterward can help you avoid getting a pressure ulcer.

If you would like to look somewhere else on the Internet for more information about how injury and friction can cause pressure ulcers, try some general websites about pressure ulcers, which include information about injury and friction. These include an article, Bedsores (Decubitus Ulcers), on the Aetna insurance company's "InteliHealth" website. Information on their website is provided by Harvard Medical School. An excellent, ad-free website is maintained by the University Health Care System, which includes a useful page about pressure ulcers. WebMD, a website run by the publicly-traded company WebMD Corporation, displays ads along with health information. An excellent, general page about Pressure Sores (Pressure Ulcers; Bed Sores; Decubitus Ulcers) was written by Debra Wood, R.N., who has more than 25 years experience as a nurse, for the health care information website HealthGate Data Corp; her wonderful article is used by a number of hospital websites across the country. And Skin & Pressure Sore Care, Treatment & Prevention after Spinal Cord Injury, on the SCI-Info-Pages website, has text and black-and-white drawings created for the Louis Calder Memorial Library at the University of Miami School of Medicine, and covers a number of pressure ulcer issues, including how bruises and scrapes (that is, injury and friction) can cause them. SCI-Info-Pages is an award-winning website maintained by Matt, a person who received a spinal cord injury at C-5/C-6 in a diving accident in 1999.

If you are interested in information that is in the same style you might see in a hospital or rehabilitation facility, an excellent resource is Pressure Ulcers: What You Should Know, created by the Consortium for Spinal Cord Medicine, which is supported financially by the Paralyzed Veterans of America (PVA). This 45-page guide is easy to read and to use. You can download a free copy in PDF format. Úlceras por Decúbito: Lo Que Usted Debe Saber Una Guía para Personas con Lesiones Medulares ha sido producida en Español de parte del PVA por el Consorcio de Medicina de la Médula Espinal. Usted puede llamar a 1-888-860-7244.

You can download a Spinal Cord Injury Manual at no cost. The manual was prepared for consumers by the Regional Spinal Cord Injury Center of the Delaware Valley, which is part of Thomas Jefferson University Hospital in Philadelphia, PA. Prevention of Pressure Sores through Skin Care is a useful PDF provided by the Spinal Cord Injury Model System, maintained by the University of Alabama at Birmingham.

1 Dharmarajan, T. S., & Ahmed, S. (2003). The growing problem of pressure ulcers. Postgraduate Medicine, 113, (5), 77-90.

2 Noble, M., Voegli, D., & Clough, G. F. (2003). A comparison of cutaneous vascular responses to transient pressure loading in smokers and nonsmokers. Journal of Rehabilitation Research and Development, 40, (3), 283-288.