Medical-Surgical Nursing · Inflammation and Healing
Pressure Injury
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In 30 seconds
A Pressure injury Localized damage to skin/underlying tissue from sustained pressure, usually over bone Full entry → is localized damage to the skin and the tissue beneath it, caused by prolonged pressure — usually over a bony prominence — sometimes combined with Shear Skin and deep tissue sliding in opposite directions Full entry →, Friction Rubbing of skin against a surface, or moisture. The term "pressure injury" has largely replaced the older terms "pressure ulcer" and "bed sore" in current professional usage, partly because the newer term recognizes that damage can occur even while the skin is still intact.
The mechanism is deceptively simple: pressure that squeezes tissue between a hard surface and a bone compresses blood vessels. When vessels are compressed long enough or hard enough, the tissue beyond them is starved of oxygen and nutrients, and cells begin to die. Because the damage begins deep and works outward, skin that still looks intact can hide significant injury underneath — one reason pressure injuries are so dangerous and so important to prevent.
Why this matters
Pressure injuries are one of the most studied and most preventable problems in health care. They cause pain, prolong hospital stays, increase infection risk, and can become chronic wounds that take months to heal. They are also a major patient-safety indicator: their development is often treated as a quality-of-care measure, and prevention is a core nursing responsibility at every level of care — hospitals, long-term care, and home health.
For the nurse, this topic connects directly to daily practice: risk assessment on admission, skin inspection, repositioning, moisture management, and knowing what to do when a suspicious area is found. A pressure injury that is caught at the earliest Stage Depth-based description of tissue damage (1–4, unstageable, suspected DTI) Full entry → is far easier to reverse than one discovered later. Prevention is genuinely the best treatment, and it is largely nursing work.
The college version
Core Concepts
Why pressure damages tissue
Every tissue needs a blood supply. When external pressure exceeds the pressure inside the small vessels, those vessels collapse and blood stops flowing to the area — a state called Ischemia Reduced blood flow from compressed vessels Full entry →. If ischemia lasts long enough, the tissue becomes hypoxic (starved of oxygen) and cells die. Two variables dominate: the intensity of the pressure and its duration. High pressure for a short time and low pressure for a long time can both cause injury. Bony prominences are especially vulnerable because the bone concentrates pressure on a small area of overlying tissue.
Shear, friction, and moisture
Pressure is the headline, but three accomplices make injury more likely:
- Shear occurs when skin and underlying tissue slide in opposite directions (for example, when a person slides down in bed while the skin of the sacrum stays put). The sliding distorts and kinks blood vessels, damaging tissue at lower pressures than straight compression alone.
- Friction is the rubbing of skin against a surface, which can strip away the superficial layers — for example, dragging a person across bed linens instead of lifting them.
- Moisture (from perspiration, incontinence, or wound drainage) softens and macerates the skin, making it weaker and more easily damaged.
Who is at risk
Risk is a combination of exposure to pressure and the body's ability to tolerate it. Common risk factors include limited mobility (which prevents self-repositioning), decreased sensation (which removes the pain signal that normally prompts movement), poor perfusion (from vascular disease or certain chronic conditions), malnutrition, age-related skin changes, and moisture. It is also important to remember that medical devices — oxygen tubing, urinary catheters, casts, and braces — can press on skin and cause device-related pressure injuries anywhere on the body, not just over bony prominences.
Where pressure injuries occur
The most common sites are areas where bone lies close to the skin: the sacrum and coccyx, the heels, the hips (trochanters), the ischial tuberosities (the bones you sit on), the elbows, the back of the head (occiput), the ears, and the shoulder blades. Heels and the sacrum are frequent trouble spots for people on bed rest; the ischial area is the classic site for people who sit for long periods. Knowing the map of at-risk sites tells the nurse where to look during skin inspection.
Staging: describing the depth of damage
Pressure injuries are described by stage, which reflects the depth of tissue damage. As an educational overview, the commonly taught framework runs:
- Stage 1: intact skin with a localized area of redness that does not blanch (turn pale) when pressed — the earliest visible warning sign.
- Stage 2: partial-thickness skin loss; a shallow open wound, or an intact or ruptured blister.
- Stage 3: full-thickness skin loss in which subcutaneous fat is visible.
- Stage 4: full-thickness loss that exposes muscle, bone, or tendon.
- Unstageable Wound base covered by slough or eschar, hiding true depth Full entry →: the wound base is covered by slough or eschar, so the true depth cannot yet be determined.
- Suspected deep tissue injury: intact skin with a persistent deep purple or maroon discoloration, indicating damage below the surface.
Formal staging is performed by qualified personnel following training and institutional policy. A student or new nurse should describe what is visible in plain terms, document it, and report the finding — not assign a stage independently.
Risk assessment
Standardized risk scales help teams identify people who need intensified prevention. These tools typically weigh factors such as sensory perception, moisture exposure, activity level, mobility, nutrition, and friction/shear, producing a score that guides how often the person is repositioned and what equipment is used. The specific scale and the score thresholds that trigger interventions vary by facility, so nurses must learn their institution's tool and policy. Risk assessment is repeated over time, not just on admission, because a patient's condition changes.
Prevention is the treatment
Prevention strategies cluster into a few proven categories:
- Repositioning and offloading: regularly changing position to relieve pressure on vulnerable areas; frequency is determined by the person's risk, tolerance, and facility policy.
- Pressure-redistribution surfaces: specialized mattresses, overlays, cushions, and heel protectors that spread pressure over a larger area.
- Skin inspection and care: daily skin checks, especially over bony prominences; keeping skin clean and dry; using moisturizers per policy.
- Moisture management: prompt attention to incontinence and perspiration.
- Nutrition support: adequate intake to support skin integrity and healing.
- Early mobility: getting the person moving as soon as safely possible.
Recognizing and reporting suspicious findings
Nonblanchable redness on intact skin is the sentinel finding — it means blood flow is already impaired in that area, even though the skin has not broken. Other warning signs include purple or maroon discoloration, blistering, pain, and skin that feels warmer or cooler than the surrounding area. Any suspicious finding should be documented descriptively, reported, and paired with immediate pressure relief (for example, repositioning the person off the area).
Common Confusions
| Do not confuse | With | Difference |
|---|---|---|
| Nonblanchable redness | Normal pressure redness (blanchable) | Blanchable redness fades with pressure and is temporary; nonblanchable means blood flow is already impaired |
| Pressure injury | Skin tear | Skin tears come from friction/shearing trauma; pressure injuries from sustained pressure — different mechanisms, though they can coexist |
| Stage 1 injury | Bruise | Stage 1 shows nonblanchable redness on intact skin; a bruise reflects bleeding under the skin from impact |
| Unstageable injury | Stage 4 injury | Unstageable means depth is hidden by slough/eschar; stage 4 means depth is known and deep — different situations |
| "Pressure ulcer" | "Pressure injury" | Newer terminology recognizes damage can occur with intact skin; use current terms per guidelines |
| Wound size | Wound stage | Size (length × width) and depth category (stage) are separate descriptors |
| Pressure only from bed rest | Pressure from any source | Chairs, wheelchairs, and medical devices cause pressure injuries too |
Eli explains
The same idea, in plain words
Explain it like I’m 10
If you press your finger on your arm and hold it there, the skin under your finger turns white because the blood is squeezed out. If something presses on one spot of your body for a long time — like lying in one position for hours — that spot can get hurt because its blood can't get through. Nurses help by turning people, keeping their skin dry and clean, and checking often so they catch the sore spot before it gets bad.
Worked example
A patient who has been on bed rest for several days after surgery complains that their right heel "feels sore." On inspection, the skin is intact but shows a small area of redness that does not blanch when the nurse presses on it. The heel is resting directly on the mattress.
The nurse recognizes this as nonblanchable erythema — the earliest stage of pressure injury — and acts immediately: the heel is offloaded by repositioning the leg so the heel floats above the mattress, a pressure-redistributing cushion or heel protection device is requested per policy, the skin is kept clean and dry, and the finding is documented and reported. The care team adds the patient to the repositioning schedule and reassesses the area at intervals.
Compare this with the alternative: no one checks the heel, the redness deepens to purple, and days later the skin opens into a full-thickness wound that takes months to heal. The first scenario is prevention working — the second is prevention failing. Most of the difference is a nurse who looked, recognized, and acted on the earliest sign.
Key takeaways
- Pressure injury = localized tissue damage from prolonged pressure, often over bony prominences, with shear, friction, and moisture as contributing factors.
- Nonblanchable erythema on intact skin is the earliest visible sign (stage 1) — act immediately with pressure relief and reporting.
- Damage begins deep and moves outward — intact skin can hide deeper injury (suspected deep tissue injury).
- Common sites: sacrum, heels, hips, ischial tuberosities, elbows, occiput; devices can cause injuries anywhere.
- Risk factors: immobility, sensory loss, poor perfusion, malnutrition, moisture, age-related skin changes.
- Prevention is the core treatment: repositioning, pressure-redistribution surfaces, skin inspection, moisture management, nutrition, early mobility.
- Staging requires training and institutional policy — students describe what they see and report; they do not stage independently.
- "Pressure injury" is the current term — older terms like "pressure ulcer" and "bed sore" are being retired.
Check yourself
6 review questions from the chapter. Try each one, then open the answer.
What is the basic mechanism by which pressure injures tissue?
Show answer
External pressure compresses blood vessels, causing ischemia; if it lasts long enough, tissue becomes hypoxic and cells die. Intensity and duration of pressure both matter.
What is the earliest visible sign of a pressure injury, and why must it be acted on immediately?
Show answer
Nonblanchable erythema on intact skin (stage 1). It signals impaired blood flow; prompt pressure relief and reporting can stop progression before the skin breaks.
Name three factors besides pressure that contribute to pressure injury development.
Show answer
Shear, friction, and moisture. (Risk factors such as immobility, sensory loss, poor perfusion, and malnutrition also contribute.)
List four common locations for pressure injuries.
Show answer
Sacrum/coccyx, heels, hips (trochanters), ischial tuberosities, elbows, occiput, ears, shoulder blades. Devices can cause injuries anywhere.
Why should a student or new nurse not assign a pressure injury stage independently?
Show answer
Formal staging requires specific training and follows institutional policy; mis-staging can mislead the care team. Students should describe what they see and report the finding.
Name four prevention strategies a nurse can implement.
Show answer
Repositioning/offloading, pressure-redistribution surfaces, regular skin inspection and care, moisture management, nutrition support, early mobility.
Study tools & related lessonsKey vocabulary · Related
Key vocabulary
- Pressure injury
- Localized damage to skin/underlying tissue from sustained pressure, usually over bone
- Ischemia
- Reduced blood flow from compressed vessels
- Nonblanchable erythema
- Redness that does not turn pale when pressed
- Shear
- Skin and deep tissue sliding in opposite directions
- Friction
- Rubbing of skin against a surface
- Maceration
- Softening/weakening of skin from prolonged moisture
- Stage
- Depth-based description of tissue damage (1–4, unstageable, suspected DTI)
- Unstageable
- Wound base covered by slough or eschar, hiding true depth
- Support surface
- Specialized mattress, overlay, or cushion that redistributes pressure
- Device-related pressure injury
- Injury caused by a medical device pressing on skin
Sources & references
This lesson was adapted from the open educational references above; their licenses and attributions are preserved. See Copyright & Licensing.
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