Pressure injury stages, and the surfaces used at each one

The stages, in plain language

Staging describes how deep the damage goes, not how serious the situation is overall. A stage 2 injury on someone frail and malnourished can be a bigger problem than a stage 3 on someone otherwise well. The stage is a description of tissue, and the clinician reads it alongside everything else.

One thing worth knowing before the list: stages do not run backwards. A stage 4 injury that is healing is described as a healing stage 4, not reclassified as a stage 3, 2 and 1 on the way. If you see the stage stop changing in the notes while the wound is visibly improving, that is why.

• Stage 1 — intact skin with a localised area of non-blanchable redness. The skin is not broken. In darkly pigmented skin the color change can be harder to see and may present as a difference from the surrounding skin rather than as redness, so changes in temperature, firmness or sensation can be the first sign.
• Stage 2 — partial-thickness loss of skin with exposed dermis. The wound bed is viable, pink or red and moist, and it may present as an intact or ruptured blister filled with clear fluid. Fat is not visible, and there is no slough or eschar.
• Stage 3 — full-thickness loss of skin, where fat is visible in the wound. Granulation tissue and rolled wound edges are often present, slough or eschar may be present, and undermining and tunnelling can occur. Fascia, muscle, tendon, ligament, cartilage and bone are not exposed.
• Stage 4 — full-thickness loss of skin and tissue, with fascia, muscle, tendon, ligament, cartilage or bone exposed or directly palpable in the wound. Slough or eschar, rolled edges, undermining and tunnelling are common.
• Unstageable — full-thickness loss where the depth cannot be confirmed because the wound bed is obscured by slough or eschar. Once the obscuring tissue is removed, a stage 3 or stage 4 injury is revealed. Stable, dry eschar on a heel or an ischaemic limb is sometimes deliberately left alone, and that is a clinical decision, not an oversight.
• Deep tissue pressure injury — persistent non-blanchable deep red, maroon or purple discolouration, or epidermal separation revealing a dark wound bed or a blood-filled blister. It results from intense or prolonged pressure and shear at the interface between bone and muscle, and it may resolve without tissue loss or may evolve quickly to reveal the true extent of the damage.
• Two further categories exist and are not staged the same way: injuries caused by a medical device, which take the shape of the device, and injuries on mucous membranes, which cannot be staged because the tissue is different.

How bad is a stage 4 pressure injury?

It is the deepest category in the staging system. A stage 4 injury means the loss of tissue has gone through the skin and the fat beneath it far enough that structures like fascia, muscle, tendon, ligament, cartilage or bone are exposed or can be felt directly in the wound. That is a serious finding and it needs a clinician who can see it, urgently, not next week.

What we are not going to do is tell you what it means for the person you are asking about. We cannot. The significance of a stage 4 injury depends on where it is, how large it is, whether infection is present, what the person's nutrition and circulation are doing, what other conditions they are managing and what the goals of their care are. Those are things the wound-care team knows and we do not, and a website that offers you reassurance or a prognosis on this question is offering you something it has no way to know.

What we can tell you is what usually happens next, because knowing the shape of it helps. The wound gets assessed and measured properly. Non-viable tissue is dealt with. Infection is looked for and managed. Pressure is taken off the area, which means a repositioning plan and usually a change of support surface. Nutrition gets attention, often from a dietitian. And somebody asks whether surgical reconstruction is on the table, which is a question for a surgical team rather than an equipment supplier.

If you are reading this at two in the morning with a photograph on your phone: contact the treating clinician or the wound-care service. That is the right next step, and it is the only one we are qualified to recommend.

What hospitals do to prevent them

Prevention in a hospital is a protocol rather than a product, and the surface is the last item on the list rather than the first. Risk is assessed on admission and reassessed regularly. Skin is inspected, particularly over the sacrum, heels, hips and any area under a device. Repositioning happens on a schedule and is documented. Moisture and incontinence are managed, because wet skin fails faster. Nutrition and hydration are assessed and acted on. Heels are offloaded specifically, because a heel does not benefit much from a mattress.

Medicare's own coverage policy gives a useful, concrete description of what a comprehensive treatment program is expected to contain, because it requires evidence of one before it will pay for a higher-level surface: an appropriate Group 1 support surface, regular assessment by a nurse, physician or other licensed practitioner, appropriate turning and positioning, appropriate wound care, appropriate management of moisture and incontinence, and nutritional assessment and intervention consistent with the person's overall plan of care. That list is not a bad checklist for a household either.

The surface sits inside that program. Joerns says its own technology "has been demonstrated to reduce the risk of pressure ulcer formation as part of protocols for the prevention and treatment of pressure ulcers" — note the phrase "as part of protocols for". That is the manufacturer's own framing and it is the right one. No surface on the market replaces turning, and any supplier who suggests one does is telling you something dangerous.

What type of mattress is best for pressure sores?

There is no single answer, and the honest version of it annoys people who want one. The right surface depends on the stage and number of wounds, where they are, the person's mobility and weight, whether moisture is a factor, what the care setting can support, and what the goals of care are. The team that assessed the person picks from a ladder; your job is to understand the rungs well enough to ask good questions.

The ladder Medicare uses is a reasonable map of the market, because manufacturers build to it. Group 1 is non-powered: foam, gel, water and non-powered air overlays and mattresses. It is where prevention and lower-risk situations usually sit. Group 2 is powered — alternating pressure and low air loss surfaces and their advanced non-powered equivalents — and it is where the criteria start requiring a documented wound. Group 3 is a single item, the air-fluidized bed, for specific severe situations.

So the practical answer for most people asking this question is: probably a Group 2 surface, chosen by the wound-care team, obtained through a supplier enrolled with the payer, on top of a proper repositioning and wound-care plan. That is not what a company selling a five-figure specialty surface is supposed to say. It is what is true most of the time, and the Medicare page on this site sets out the criteria in detail so you can check the documentation before it goes in.

The surfaces, mechanism by mechanism

Four mechanisms account for most of what you will be offered, and they are genuinely different from each other. Knowing which one is in the room is more useful than knowing the brand.

• Non-powered (Group 1) — foam, gel, water or air, with no pump. The surface conforms and spreads load over a larger area. Simple, quiet, nothing to fail, and the baseline that the higher tiers are measured against.
• Alternating pressure (Group 2) — an air pump inflates and deflates cells in sequence, so the areas carrying load change on a cycle and no single area carries it continuously. CMS describes this under E0277 for a mattress and E0372 for an overlay.
• Low air loss (Group 2) — an air pump or blower maintains a low interface pressure throughout the surface while air moves through it, managing heat and moisture at the skin. Same codes as above; the code descriptions cover alternating pressure, low air loss and powered flotation together.
• Air-fluidized (Group 3, E0194) — warm filtered air is circulated through silicone-coated ceramic beads so the bed takes on fluid characteristics and the body is supported by the moving medium. It is the top of the coverage ladder and it has the strictest criteria attached.
• Fluid immersion simulation — a fifth mechanism. Joerns' AutoVector® control module monitors the support surface "more than 100 times per second for any patient movement or surface changes", automatically measures the anthropometric characteristics of the individual as they engage the surface, and produces an individualised immersion profile that Joerns describes as creating "a near neutrally buoyant state".

Dolphin FIS and a low air loss bed: what is actually different

The mechanisms differ. A low air loss surface uses moving air to keep interface pressure low across the whole surface and to manage moisture and heat at the skin. Fluid immersion simulation adjusts the surface continuously against a measured profile of the individual person, aiming for immersion rather than airflow. Joerns describes its system as delivering "many of the best elements of air-fluidized therapy such as three-dimensional volumetric engagement and the elimination of gradient shear forces". That is the manufacturer's claim, in the manufacturer's words, and we are not going to strengthen it.

The coding position differs, and this is the part that changes what happens to you. Low air loss and alternating pressure are described, coded categories — E0277, E0371, E0372, E0373 — that a payer can authorize and pay against when its criteria are met. Fluid immersion simulation has no HCPCS code of its own. There is nothing for a payer to authorize, price or reimburse, which is why a Dolphin FIS system is a private purchase or rental and why we do not bill Medicare or any insurer.

A Dolphin FIS is also not an air-fluidized bed. E0194 is defined by a specific mechanism — warm filtered air through silicone-coated ceramic beads — and this is not that. Joerns' own language is a comparison to air-fluidized therapy, not a claim of equivalence, and any supplier telling you the product is "covered under E0194" is describing something that does not exist.

What follows from all that is unglamorous. If the clinical need is met by a Group 2 surface, the Group 2 surface is very likely the right answer, because it is the one with a code, a policy, a contracted supply chain and someone else paying. Fluid immersion simulation is a conversation for the situations where a care team has specifically asked for it and the household has decided to fund it.

What the indications actually say

Joerns states that the technology "reduces soft tissue distortion and promotes blood flow, creating a platform that is highly effective for the prevention and healing of pressure injuries through Stage 4, as well as, treating patients with post-operative flaps and grafts". It adds that the system "may also be used for patients whose medical condition precludes turning and repositioning, or where these interventions may be contraindicated", and for "patients with spinal cord injury once the acute injury has been stabilized and these patients have been cleared by a physician".

Those are the published indications and they are the limit of what may be said. There are no outcome percentages, no healing-time figures and no patient stories in any Joerns source we could read, so there are none on this site. If you find a supplier quoting a healing rate for this technology, ask them where it came from and read the source yourself.