Pressure injury staging
Depth of injury · Stages 1-4 Capillary closing ~32 mmHg Bony prominence
Localised damage to skin and underlying soft tissue over a bony prominence or under a device, caused by sustained pressure with or without shear. Because staging is defined purely by the deepest tissue involved, it maps directly onto the layers of the skin.
Traced from the start
Detail
- Mechanism
- External pressure exceeding the capillary closing pressure of about 32 mmHg obstructs the dermal microcirculation; shear additionally kinks the perforating vessels crossing the hypodermis
- Stage 1
- Non-blanchable erythema of intact skin — the microcirculation of the subpapillary plexus is damaged but the epidermis is unbroken
- Stage 2
- Partial-thickness skin loss with exposed dermis; no slough, eschar or granulation tissue. Moisture-associated skin damage and skin tears are not staged this way
- Stage 3
- Full-thickness skin loss with adipose tissue visible; granulation tissue, rolled wound edges, slough or eschar may be present, and undermining or tunnelling may occur, but fascia, muscle, tendon, ligament, cartilage and bone are not exposed
- Stage 4
- Full-thickness skin and tissue loss with exposed or directly palpable fascia, muscle, tendon, ligament, cartilage or bone
- Unstageable and deep tissue injury
- Unstageable when slough or eschar obscures the depth of a full-thickness loss; deep tissue pressure injury when there is persistent non-blanchable deep discolouration or a blood-filled blister, reflecting damage that began at the muscle-bone interface
- Sites and prevention
- Sacrum, heels, ischial tuberosities, greater trochanters and occiput; risk scored with the Braden or Waterlow scale and managed by repositioning, pressure-redistributing surfaces, moisture control and nutrition
When it goes wrong
Immobility with sustained sacral pressure in an elderly inpatient
Because muscle tolerates ischaemia less well than skin, deep damage can be extensive under apparently intact skin; the visible lesion underestimates the injury and may declare itself days later
Stage 4 injury with exposed bone at the sacrum or heel
Underlying osteomyelitis should be assumed; investigate with MRI and bone biopsy rather than superficial swab, and plan surgical debridement
Dry, stable, adherent heel eschar
It is left intact as a biological cover rather than debrided, unless there is fluctuance, erythema or drainage suggesting infection
Practise this structure
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