Chronic wounds are usually vascular, diabetic or pressure wounds. Vascular wounds can be caused by venous stasis (incompetence of the valves within the veins leading to pooling of blood in tissues and breakdown of tissues) or peripheral vascular disease leading to decreased arterial blood flow and death of tissue. Diabetic ulcers are related to small vessel disease, decreased sensory input, hyperglycemia, and poor skin quality. Pressure ulcers are related to unrelieved pressure (for as little as 2 hours) on tissues leading to break-down, usually seen in paraplegics who have no sensation in the buttocks and thighs.
Normal wound healing is usually divided into four stages. An interruption of one or more stages causes a wound not to heal properly. The first stage is the coagulation stage in which platelets and the normal blood clotting cascade prevents excessive bleeding and provides the initial protection of the wound. The inflammatory phase leads to mobilization of white blood cells and macrophases and the activation of growth factors and dermal/epidermal cells. The third stage of wound healing is the proliferative phase
with the formation of granulation tissue. The final stage is the remodeling phase with the formation of scar tissue that seals off the wound with a protective barrier.
Most chronic wounds that fail to heal are characterized by a prolonged inflammatory phase with associated infection. Steroids, a compromised immune system, and smoking may contribute to poor wound healing.
Debridement of non-viable tissues, controlling infection (with topical antiseptics and topical antibacterials and systemic antibiotics) and maintaining a moist envirnoment are important managment tools. Hyperbaric Oxygen Therapy is sometimes indicated to promote wound healing by adding supra-saturated oxygen concentrations into the arteries under increased pressure.