Q8. How are pressure ulcers classified?
1. See Table 2 for the National Pressure Ulcer Advisory Panel (NPUAP) ulcer staging system (NPUAP 2007) and Figure 5 for associated images.
Stage 1: Intact but non-blanchable skin
Stage 2: Partial thickness loss of dermis
Stage 3: Full thickness tissue loss
Stage 4: Full thickness tissue loss with exposed bone, tendon or muscle

Table 2. National Pressure Ulcer Advisory Panel’s (NPUAP) Pressure Ulcer Staging



Deep Tissue Injury (Suspected) Stage

Purple or maroon localized area of discolored intact skin or blood-filled blister due to damage of underlying soft tissue from pressure and/or shear. The area may be preceded by tissue that is painful, firm, mushy, boggy, warmer or cooler as compared to adjacent tissue.

Stage I

Intact skin with non-blanchable redness of a localized area usually over a bony prominence. Darkly pigmented skin may not have visible blanching; its color may differ from the surrounding area.

Stage II

Partial-thickness loss of dermis presenting as a shallow open ulcer with a red pink wound bed, without slough. May also present as an intact or open/ruptured serum-filled blister.

Stage III

Full-thickness tissue loss. Subcutaneous fat may be visible but bone, tendon, or muscles are not exposed. Slough may be present but does not obscure the depth of tissue loss. May include undermining and tunneling.

Stage IV

Full-thickness tissue loss with exposed bone, tendon, or muscle. Slough or eschar may be present on some parts of the wound bed. Often includes undermining and tunneling.


Full-thickness tissue loss in which the base of the ulcer is covered by slough (yellow, tan, gray, green, or brown) and/or eschar (tan, brown, or black) in the wound bed.


Figure5. Illustration of stages of decubiti formation