Clinical meaning
Pressure injuries result from sustained mechanical loading (pressure plus shear) that compresses soft tissue between a bony prominence and an external surface, causing localized ischemia and tissue necrosis. The National Pressure Injury Advisory Panel (NPIAP) staging system classifies injuries by tissue depth: Stage 1 is non-blanchable erythema of intact skin; Stage 2 involves partial-thickness loss with exposed dermis (shallow open wound or blister); Stage 3 is full-thickness skin loss with visible subcutaneous fat but no exposed bone, tendon, or muscle; Stage 4 is full-thickness tissue loss with exposed bone, tendon, cartilage, or muscle. Unstageable injuries have full-thickness loss obscured by slough or eschar preventing depth assessment. Deep tissue pressure injury (DTPI) presents as persistent non-blanchable deep red, maroon, or purple discoloration of intact or non-intact skin from damage to underlying tissue from prolonged pressure. Reverse staging is inappropriate - a healed Stage 4 does not become Stage 3; it becomes a healed Stage 4.
Exam relevance
Risk factors: - Immobility and inability to independently reposition - Moisture exposure (incontinence, perspiration, wound drainage) - Nutritional deficiency with albumin < 3.0 g/dL - Decreased sensory perception preventing recognition of pressure - Shear forces from sliding down in bed or chair