Question 20

a) Outline the classification system for pressure induced skin and soft tissue injuries.
(20% marks)
b) List six risk factors for the development of pressure injuries. (30% marks)
c) List the mechanisms by which negative pressure wound therapy systems (VAC systems) potentially contribute to wound healing. (20% marks)
d) List six complications of negative pressure wound therapy systems. (30% marks)

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College answer

Not available.


a) This is the NPUAP/EPUAP system (2009), which goes by many names, and which is endorsed by the Australian Wound Management Association and the Pan Pacific Clinical Practice Guideline for the Prevention and Management of Pressure Injury.

  • Stage I: non-blanchable erythema
  • Stage II: partial thickness skin loss
  • Stage III: full thickness skin loss
  • Stage IV: full thickness tissue loss
  • Unstageable pressure injury: depth unknown
  • Suspected deep tissue injury: depth unknown

b) Risk factors for pressure injuries are numerous; one might expect that any six of the following would have been enough:

  • Modifiable risk factors
    • Prolonged immobility
    • Use of neuromuscular junction blockers
    • Use of steroids
    • Hemodynamic instability preventing pressure area care
    • Incontinence with soiling
    • Low albumin
    • Poor nutrition
    • Oedema
    • Hypotension
  • Non-modifiable risk factors and comorbidities
    • Low BMI (no padding!)
    • Altered mental state
    • Peripheral vascular disease
    • Diabetes
    • Age over 60
    • Severe illness (APACHE II score over 13)
  • Associated disease states:
    • malignancy
    • stroke
    • pneumonia
    • sepsis
    • heart failure

c) Several mechanisms are proposed to explain how VAC works.

  • Stabilisation of the wound environment
  • Removal of extracellular fluid
  • Contraction of the wound
  • Microdeformation at the foam-wound interface
  • Neurogenesis
  • Angiogenesis
  • Modulation of inflammation
  •  Stimulus for cellular proliferation

d) Complications of VAC systems:

  • Seal failure and pump blockage (i.e. where the VAC doesn't vac)
  • Bleeding, eg. where the dressing is applied over vessels, or where dressing change disturbs haemostatic thrombi
  • Protein loss  because the fluid being sucked out is relatively protein-rich; in this fashion these patients lose more protein per area VACed than do burns patients
  • Fluid loss which is often an accountable volume, perhaps measured in litres per day
  • Infection, eg. introduced during dressing changes or as the result of a failed seal
  • Pain, both constant and acutely severe during dressing changes (which often require sedation)


Krupp, Anna E., and Jill Monfre. "Pressure Ulcers in the ICU Patient: an Update on Prevention and Treatment." Current infectious disease reports 17.3 (2015): 1-6.

Coyer, Fiona, et al. "Reducing Pressure Injuries in Critically Ill Patients by Using a Patient Skin Integrity Care Bundle (Inspire)." American Journal of Critical Care 24.3 (2015): 199-209.

Panayi, Adriana C., Tripp Leavitt, and Dennis P. Orgill. "Evidence based review of negative pressure wound therapy." World J Dermatology 6.1 (2017).

Li, Zonghuan, and Aixi Yu. "Complications of negative pressure wound therapy: a mini review." Wound Repair and Regeneration 22.4 (2014): 457-461.

Fagerdahl, Ann-Mari, et al. "Risk factors for unsuccessful treatment and complications with negative pressure wound therapy." Wounds 24.6 (2012): 168.