How Do Pressure Sores Form and How Can They Be Prevented?

A pressure sore, also called a pressure injury or bedsore, is damaged skin and tissue caused by sustained pressure, friction or shear, often over a bony area such as the tailbone or heel. Sores are more likely when someone cannot shift position easily, has fragile skin or has reduced sensation. A review of best practices in PubMed Central (NIH), listed in Sources, describes prevention as combining position changes, skin protection, moisture management and support surfaces. This article explains how sores develop, who is at risk, early skin changes and when to get urgent care.

How Pressure Sores Form: Pressure, Friction and Shear on Fragile Skin

According to MedlinePlus (NIH), pressure sores are areas of damaged skin and underlying tissue caused by sustained pressure on the skin. They often appear over bony parts of the body. Several factors contribute, and the mechanism is not fully understood in every person.

The basic story goes like this. When your body weight presses skin against a mattress, chair or other hard surface, the small blood vessels in that spot get squeezed. Blood carries oxygen and nutrients. If the squeeze continues, the tissue may not get enough of either, and cells can be injured. In deep tissue injury, damage can start in tissue near the bone while the skin surface looks only discolored or intact.

Three forces are usually discussed together:

• Pressure: weight pressing on one area for a long stretch, such as the tailbone while lying on your back.
• Friction: skin rubbing against sheets, a wheelchair seat or clothing, which can scrape the top layer.
• Shear: layers of tissue sliding in opposite directions, for example when a person slumps down in a raised bed and the skin stays put while the bones move.

Moisture from sweat or incontinence can soften skin and make it easier to injure. If bladder leaks are part of the picture, our article on urinary incontinence in older adults covers causes and treatment options.

Who Is at Higher Risk of Developing Pressure Sores

Anyone who spends long periods in one position can be affected. Risk is often higher in older adults because skin may be thinner and drier, and because illness or weakness can limit movement. A hospital stay can add to this, and our article on strength loss after a hospital stay explains why recovery of mobility can be slow.

Factors that are associated with higher risk include:

• Limited movement: being bedbound, using a wheelchair for long periods, or recovering from surgery or a hip fracture.
• Reduced sensation: nerve damage can mean a person does not feel the discomfort that would normally prompt a shift in position. Spinal cord injuries and peripheral nerve disorders are examples.
• Medical conditions: diabetes and conditions that reduce circulation may affect how well skin heals.
• Poor nutrition or low fluid intake: skin and healing tissue need adequate nourishment.
• Moisture: sweat, urine or stool left against the skin.
• Confusion or sedation: a person may not be able to tell anyone that something hurts or may not move on their own.

Research on people with spinal cord injury suggests that personal factors matter too. In one small South African study, "I forget to do pressure relief", participants described forgetting routine pressure-relief habits, which suggests that reminders and routines may be useful.

Where Pressure Sores Often Develop

Pressure sores commonly appear where bone lies close to the skin surface. Which spots are affected often depends on the position a person spends the most time in.

• Lying on the back: tailbone, sacrum, heels, shoulder blades, back of the head and elbows.
• Lying on the side: hip bone, outer knee, ankle bone, shoulder and ear.
• Sitting in a chair or wheelchair: tailbone, buttocks, backs of the thighs and heels, and sometimes the spine or shoulder blades.

Medical devices can also cause pressure injuries. Tight straps, oxygen tubing, casts, splints and face masks can press on skin. A systematic review of mask-related pressure injury prevention with non-invasive ventilation discusses this problem for people who use breathing masks. If a person wears any device, ask their care team how often to check the skin underneath.

Early Skin Changes to Look For

Catching a problem early gives the skin the best chance to recover. Check the skin daily, especially over the bony areas above. In people with darker skin, redness can be harder to see, so touch, warmth and texture matter as well as color.

Changes that may suggest early pressure damage include:

• A patch of skin that looks red, purple or darker than the skin around it and does not fade after you gently relieve the pressure.
• Skin that feels warmer, cooler, firmer or softer than the surrounding area.
• Swelling in one spot.
• Pain, itching or tenderness in an area that has been pressed on. Some people with reduced sensation feel nothing, so a lack of pain does not rule out damage.
• A blister or shallow open area.

As a sore progresses, it can become a deeper wound that exposes fat, muscle or even bone. Dead tissue may look dark, black or leathery. At that point the wound needs professional care. A pressure sore may be hard to tell apart from a friction blister or other skin problem, so a clinician should look at any area that worries you.

Pressure Injury Stages: What Clinicians Mean by Stage 1 to Stage 4

Clinicians commonly describe pressure injuries in stages, which grade how deep the damage goes. Your care team may use these terms, and the exact assessment is theirs to make. The descriptions below are a simplified overview.

• Stage 1: intact skin with redness or darker color that does not fade when pressure is relieved.
• Stage 2: partial loss of skin thickness, which may look like a blister or shallow open sore.
• Stage 3: full loss of skin thickness, with visible fat beneath.
• Stage 4: deeper loss that can expose muscle, tendon or bone.
• Unstageable and deep tissue injury: the wound base is covered by dead tissue, or the skin looks deep red, maroon or purple while deeper tissue is damaged. These need prompt professional assessment.

Earlier stages may improve once pressure is removed, while deeper stages often need a wound care plan. Because depth can be hard to judge from the surface, any open sore or blister should be looked at by a clinician.

Everyday Steps to Prevent Pressure Sores

A review of best practices for preventing pressure injuries in people with impaired mobility describes prevention as a combination of strategies rather than a single fix, including repositioning, skin assessment, support surfaces and nutrition. The steps below are common elements. Ask the care team which ones fit your situation.

Change position regularly

Shifting weight takes pressure off one spot and lets blood flow return. A person in bed may be turned or helped to a different position on a schedule that a nurse or physician sets, and a person in a chair may be taught to lift or lean to relieve the seat. Care teams often use a risk assessment tool to judge a person's risk and set an individual repositioning plan, and the right schedule depends on the person's skin, health and support surface. Ask what plan fits the person rather than relying on a general rule.

Reduce friction and shear

• Lift rather than drag a person when moving them, or use a draw sheet or slide sheet if the care team recommends one.
• Keep the head of the bed only as high as needed when possible, since sitting up in bed can cause sliding. A clinician can advise when a higher angle is necessary, such as for meals or breathing.
• Smooth out wrinkles in sheets and clothing and avoid thick seams under bony areas.
• Keep heels off the mattress surface using pillows or a device the care team suggests, so the heels are not bearing weight.

Care for the skin

• Clean the skin gently when it is soiled and pat it dry instead of rubbing.
• Use a moisture barrier or other products if a clinician recommends them for incontinence-related moisture.
• Avoid massaging reddened areas over bone, since this may cause further injury. Ask a clinician if you are unsure.
• Keep skin from getting very dry. A clinician or pharmacist can suggest a suitable moisturizer.

Support nutrition and hydration

Healthy skin and wound repair depend on enough calories, protein and fluids. Appetite often falls with illness or age. Tell the clinician if a person is eating or drinking much less than usual, has lost weight or has trouble chewing or swallowing, so they can decide whether a dietitian or other support is appropriate. Changes to diet in people with kidney disease, diabetes or other conditions should be guided by their clinician.

Stay as active as safely possible

Walking, sitting up for meals and doing the exercises a physical therapist suggests can all reduce long stretches in one position. After a hip fracture or an illness, ask the rehabilitation team how much activity is appropriate. Our article on recovery after a hip fracture in an older adult describes what rehab often involves.

Mattresses, Cushions and Other Support Surfaces

Special surfaces are designed to spread pressure over a larger area or to vary which parts of the body bear weight. A review of support surfaces for pressure ulcer prevention compares options such as foam, gel, air-filled and alternating-pressure designs. The evidence for how much better one type is than another varies, so the choice usually depends on the person's risk, mobility and setting.

• Foam or gel cushions and mattresses: spread weight and are common in homes and care facilities.
• Air-filled or alternating-pressure mattresses: change the pressure under the body over time. Reviews note that support-surface designs continue to change, and the evidence for one type over another is mixed.
• Wheelchair cushions: should be matched to the person and checked by a therapist, because the wrong fit or a flat, worn cushion may reduce protection.

A ring or donut-shaped cushion is sometimes used, but it can concentrate pressure on surrounding tissue. Ask a clinician or occupational therapist before choosing one. Even the best surface does not replace skin checks and position changes.

What Happens if a Pressure Sore Develops

Treatment generally begins with taking pressure off the area, and the care team then plans wound cleaning, dressings, nutrition and infection checks based on the stage. If the person keeps lying or sitting on the sore, it is unlikely to heal. A care team may adjust the support surface, change the repositioning plan, clean and dress the wound, and look at nutrition, moisture, circulation and blood sugar. Which dressing is appropriate depends on how deep the wound is and whether there is drainage, so do not choose products for a wound without guidance.

In broad terms, a stage 1 or shallow stage 2 injury is often managed by relieving pressure, protecting the skin and monitoring it. Deeper wounds more often need dressings chosen by a clinician, closer follow-up and sometimes a wound specialist. Healing time varies widely with depth, overall health and how well pressure can be avoided.

Clinicians also assess the wound for signs of infection and ask about pain, since pressure sores can be painful and pain control may be part of the plan. Some wounds need removal of dead tissue by a clinician, and deep, infected or slow-healing ones may call for referral to a wound specialist or surgery. A review of therapeutic interventions for pressure ulcers after spinal cord injury notes how limited the evidence is for many treatments, which is another reason to rely on a clinician's plan.

Complications

Pressure sores can become infected. An infection can spread to the surrounding skin, to bone, or to the bloodstream, which can cause a life-threatening reaction called sepsis. Some bacteria are hard to treat with common antibiotics, which is one reason to avoid using leftover or unprescribed antibiotics. MedlinePlus (NIH) explains antibiotic resistance in more detail.

Practical Tips for Family Caregivers

• Pick a consistent time each day for a head-to-toe skin check, such as during bathing or dressing.
• Write down what you see, including the location, size and color, so you can show a clinician how it changes.
• Ask the nurse or therapist to demonstrate safe turning and lifting methods before you try them alone.
• Make sure the person can reach a call button or has some way to ask for help if they feel pain.
• Take photos only if the care team agrees, and share concerns early instead of waiting for a scheduled visit.
• Tell the care team about new incontinence, poor appetite, fever or a change in mental state, since these may raise risk.

This article is general information and cannot diagnose a skin problem. A clinician combines history, examination and sometimes testing to judge how serious a sore is and what treatment fits.

When to Seek Medical Care