Pressure ulcer categories
When skin and tissue are subject to pressure and displacement between the surface and the bone, then the circuit are shut off, after which the tissue in a while (minutes - hours) are destroyed from necrosis. The damages are often visible in the skin's top layer to begin with, to later include all layers and underlying tissue - including muscle fascia and muscle tissue. Muscle tissue is particularly sensitive to pressure. This, combined with concentrating the pressure and shear against the bone, can cause initial development of pressure damage in depth. The traditional division of pressure ulcers are graded based on the depth of the sore.
Pressure ulcer grading:
Category 0 / Signs of pressure
Reddening of the skin (hyperaemia), which disappears from pressing it. Category 0 is the skin's natural response to pressure, which momentarily leave a pale area, which is followed by subsequent redness that disappears again. Category 0 is not considered pathological
Redness of the skin. Not fading by applying pressure. Beginning tissue damage. Aseptic inflammation. The skin is intact. Painful.
Superficial skin loss through the epidermis / dermis, or both. Possibility of blisters. Painful.
Full skin loss - sore going through the subcutis without breakthrough to fascia. Often undermining, much secretion. Painful.
Distinct necrosis. Damage to muscles, bone and connective tissue. Possibility of infection. Often no pain, much secretion
Slip forces are particularly dangerous for the tissue that is already expose to pressure, because the relatively small lateral impact of the tissue is a torsion force of the vessels, which then is closed off. Typically, these slippage forces are seen from incorrect posture or when the patient progresses into the bed by lifting the headboard.