What causes bottom-up injury?

Bottom-up injury refers to damage that occurs primarily due to underlying factors that affect the deeper layers of the skin and soft tissue before the overlying tissue shows signs of injury. Pressure and shear are the primary mechanisms for bottom-up injury.

When there is sustained pressure on a specific area of the skin, blood flow is compromised in the tissues underneath, leading to ischemia and eventual tissue necrosis. Shear forces occur when the skin is moved in a direction that is different from the underlying soft tissue, which can further disrupt blood flow and lead to deeper tissue damage. This combination of pressure and shear is critical in the formation of pressure injuries, particularly in bony prominences, where soft tissue is particularly vulnerable.

In contrast, while friction and moisture can lead to skin damage, they primarily contribute to superficial injuries rather than bottom-up injuries. Diaphoresis and incontinence can exacerbate skin integrity issues but do not directly cause the deeper tissue injury characteristic of bottom-up injury. Intermittent blood flow may affect tissue health, but without sustained pressure or shear, it does not specifically lead to the type of deep tissue injury associated with bottom-up damage.