**5. Pressure ulcer stages**

Pressure ulcers are classified by the amount of visible tissue loss [4]. Depth of tissue loss is important, as it determines a treatment plan of care and can impact payment. Once a wound is determined to be a pressure ulcer, it is assigned a pressure ulcer‐specific stage or category. No other wound utilizes this same staging/categorizing system. A stage or category is assigned after careful and thorough assessment of the pressure ulcer to determine the extent of tissue destruction. To complete this assessment, one must have a competent understanding of the anatomy of the tissue layers involved and of the physiology of pressure ulcer development.




**Table 2.** Pressure ulcer staging [4].

**EPUAP staging**

was not due to ischemia in the epidermis. Three decades later, it has been hypothesized that the friction used in Dinsdale's study was creating shear strain or deformation in deeper layers of tissue. Current hypothesis is that friction causes mechanically damaging shear strain of superficial tissue cells and tissue damage results directly from excessive deformation not

Friction is an important factor as it leads to shear stress and strain yet does not alone lead to the development of a pressure ulcer. Friction contributes to the development of a pressure ulcer due to the shear forces it can create. In other words, friction causes the shear forces in the tissue, which can increase the risk of tissue breakdown and lead to the development of a pressure ulcer. Therefore, shear remains in the current NPUAP definition of a pressure ulcer yet friction is eliminated. Including friction would be redundant as friction is now thought to be a cause of shear. Also, eliminating friction may decrease the number of wounds that are misdiagnosed

Pressure ulcers are classified by the amount of visible tissue loss [4]. Depth of tissue loss is important, as it determines a treatment plan of care and can impact payment. Once a wound is determined to be a pressure ulcer, it is assigned a pressure ulcer‐specific stage or category. No other wound utilizes this same staging/categorizing system. A stage or category is assigned after careful and thorough assessment of the pressure ulcer to determine the extent of tissue destruction. To complete this assessment, one must have a competent understanding of the anatomy of the tissue layers involved and of the physiology of pressure ulcer development.

The NPUAP has defined the stages or categories of pressure ulcers as follows (**Table 2**):

Stage I Nonblanchable erythema—Intact skin with nonblanchable redness of a localized area usually over a

Stage II Partial thickness skin loss—partial thickness loss of dermis presenting as a shallow open ulcer with a

Stage III Full‐thickness skin loss—Full‐thickness tissue loss. Subcutaneous fat may be visible but bone, tendon or

bony prominence. Darkly pigmented skin may not have visible blanching; its color may differ from the surrounding area. The area may be painful, firm, soft, warmer or cooler as compared to adjacent tissue. Category I may be difficult to detect in individuals with dark skin tones. May indicate "at‐risk"

red pink wound bed, without slough. May also present as an intact or open/ruptured serum‐filled or sero‐sanguinous‐filled blister. Presents as a shiny or dry shallow ulcer without slough or bruising. This category should not be used to describe skin tears, tape burns, incontinence‐associated dermatitis,

muscles are not exposed. Slough may be present but does not obscure the depth of tissue loss. May

as pressure ulcers when they are caused solely by friction [10].

ischemia as previously thought.

328 Wound Healing - New insights into Ancient Challenges

**5. Pressure ulcer stages**

persons.

maceration or excoriation

**EPUAP staging guideline**

An illustration of the pressure ulcer stages/categories is seen in **Table 3** [1].

As pressure ulcers heal, the lost muscle, subcutaneous fat or dermis are not replaced with like tissue before they re‐epithelialize [12]. A pressure ulcer fills in with scar tissue, which is composed primarily of endothelial cells, fibroblasts, collagen and extracellular matrix. Therefore, a stage‐III pressure ulcer, for example, cannot, as the wound heals, become a stage‐ II pressure ulcer and progress on to a stage‐I pressure ulcer because the term stage I would not accurately reflect the structures that are now present under the newly re‐epithelialized tissue. Referring to a healing stage‐III pressure ulcer as a stage II, then a stage‐I pressure ulcer is known as reverse staging or down staging and is not acceptable. The stage needs to reflect the scar tissue that has developed. Therefore, the stage for this healing pressure ulcer is "healing stage‐III pressure ulcer" and when the pressure ulcer has healed, the stage is a "healed stage‐III pressure ulcer," indicating the pressure ulcer is now filled with granulation or scar tissue and resurfaced with epithelium [12].

**Table 3.** Pressure ulcer injury/ulcer stages/categories.

Mucosal pressure injuries are *pressure injuries found on mucous membranes with a history of a medical device in use at the location of the ulcer* [1]. A mucous membrane is the moist lining of a body cavity, such as the gastrointestinal tract, nasal passages, urinary tract and vaginal canal, that communicates with the exterior. When pressure is applied to a mucous membrane, ischemia can result that can lead to a pressure ulcer. Mucous membranes are vulnerable to pressure especially related to medical devices such as oxygen tubing, feeding tubes, urinary catheters and fecal containment devices [13].

The anatomy of mucous membranes impacts the staging or categorizing of a mucous mem‐ brane pressure injury [13]. There are two types of mucous membrane tissue; nonkeratinized stratified squamous epithelium and an underlying connective tissue layer, the lamina propria. These layers are similar to the epidermis and dermis and are connected via rete pegs. At the interface of the two layers is a basal laminal layer. The epithelial layer is continuously renewed through migration of lower layers of epithelium to the surface. The epithelium of the mucosa, although is not keratinized like the epithelium of the skin. The lamina propria generally contains blood vessels, elastin and collagen fibers [13].

Injured mucosa heals similarly as skin with the exception of scar formation [13]. There is an increasing evidence that the fibroblasts in mucosa resembles fetal fibroblasts. Most mucosal injuries heal without scar formation [13].

The staging or categorizing of pressure ulcers that is used for the skin cannot be used to stage mucosal pressure injuries [13]. Nonblanchable erythema cannot be seen in mucous mem‐ branes, as superficial tissue losses of the nonkeratinized epithelium are so shallow they cannot be differentiated from deeper, full thickness injuries. The coagulum seen on a mucous membrane pressure injury resembles slough yet it is actually soft blood clot. Muscle is seldom seen in a mucous membrane pressure injury and bone is not present in these tissues. Therefore, pressure injuries located on a mucous membrane are referred to as mucous membrane pressure injuries [13].
