Discussion:

The definition offered for pressure ulcers was the “clinical sequelae of compromised blood flow to tissues superficial to bone.” Pressure ulcer types were divided into truncal and extremity pressure ulcers in recognition of the different causes and treatment strategies. The stages were described according to the amount of tissue loss as shown in the table below. The authors note that there can be several stages in a wound at one time, which should be completely assessed. However, the authors suggest that the overall treatment plan should reflect the worst stage assessed.

 

Stage	Description
I	No visible loss of tissue. Underlying area is affected and is evidenced by nonblanchable erythema or a different appearance from surrounding tissues in darkly pigmented skin.
II	Superficial partial-thickness skin breakdown. Minimal necrosis, but painful. May be an abrasion or superficial blister and are open to bacterial contamination.
III	Full thickness skin breakdown above the deep fascia. Also open to bacterial colonization.
IV	Wound that extends through deep fascia and exposes underlying muscle and/or bone.

 

Risk Factors

The authors explored risk factors for pressure ulcer development including nutritional status, age, and the presence of vascular compromise or immobility. The authors suggested that the evidence for treatment of nutritional status, particularly of hypoalbuminemia, has not been clearly shown to improve treatment.

 

Impaired healing and immobility are both risk factors for the elderly and contribute to an increased risk for pressure ulcers. This is especially true when patients have other problems that decrease tissue perfusion, such as cardiovascular disease, infections, and other problems.

 

The authors describe the pathogenesis of the pressure ulcer initiated through pressure, shear forces, and reperfusion ischemia. As little as 12 mm Hg pressure can impair blood supply. Pressures above normal arteriolar pressure of 32 mm Hg can prevent tissue perfusion. Pressure at 70 mm Hg for two hours can lead to ulcers, though 240 mm Hg can be tolerated if pressure is routinely relieved. A standard hospital bed can apply 150 mm Hg and normal sitting pressures can reach 300 mm Hg, it becomes a challenge for immobile patients to maintain tissue integrity. In addition, patients can experience shear forces where there is a tangential force applied to the dermal and underlying deeper tissues. This can occur when the head of the bed is elevated higher than 30 degrees and the patient subsequently slides downward. This contributes to friction forces on the skin which may damage outer layers of tissues. If shear forces exist, the amount of pressure required to cause pressure ulcers is greatly reduced. When tissues are relieved of pressure and allowed to reperfuse with blood, tissue can be damaged by both the reperfusion process and the inflammatory mediators that are carried to the wound in the process.