Pathophysiology of PU Formation

When point-pressure is placed on a garden hose (a kink), the flow of water is stopped. Similarly, in soft tissue, unrelieved pressure stops the flow of blood in the microcirculation.

Point-pressure increases tissue injury by:

• increasing capillary permeability, particularly after pressure is released
• increasing interstitial oedema
• blocking lymphatic and venous drainage
• occluding vessels causing hypoxia, ischaemia and tissue necrosis.

How this mechanism operates and leads to development of PU is well illustrated in a flow-chart.  Click on the Cellular Response button to review this flow-chart.

Notice that on the left slide of the flow-chart that if pressure is relieved, no damage to the skin occurs.  However, the remainder of the flow-chart demonstrates the effect of unrelieved pressure on skin and soft tissue.