The management and treatment of wounds remain a treatment challenge. In the majority of chronic wounds, healing will take place only if the underlying cause (venous stasis, pressure, infection, etc.) is addressed. In addition, cleaning the wound to remove non-viable tissue, microorganisms, and foreign bodies is essential to create optimal conditions for either reepithelialization (healing by secondary intention) or preparation for wound closure with skin grafts or flaps (healing by primary intention). Debridement, irrigation, whirlpool treatments, moist dressings, negative pressure wound therapy (NPWT), and the use of certain bioengineered skin substitutes are components of chronic wound care.
NPWT consists of:
- Non-adherent, porous wound dressing (one example is GranuFoam™, San Antonio, Texas);
- Drainage tube placed adjacent or inserted in the dressing;
- Occlusive transparent film (which seals the wound);
- Connection to a vacuum source, which supplies the negative pressure; and
The concept is to turn an open wound into a controlled, closed wound while removing excess fluid from the wound bed, thus enhancing circulation and disposal of cellular waste from the lymphatic system. The outcome is improved tissue perfusion, reduction in tissue edema and increased granulation tissue formation.
A non-powered (mechanical) NPWT system has also been developed; one device is the Smart Negative Pressure (SNaP) Wound Care System. This device is portable and lightweight (3 oz) and can be worn underneath clothing. This system consists of a cartridge, dressing, and strap; the cartridge acts as the negative pressure source. The system is reported to generate negative pressure levels similar to other NPWT systems. This system is fully disposable.
Wounds occur when the integrity of the skin is compromised. Wounds can occur by a fall, a surgery, a tear, piercing, an infectious disease; or by an underlying condition such as diabetes or venous insufficiency causing necrosis of the tissue. The causes may be structural, such as injury, pressure phenomena or physiological, such as an underlying disease. Most acute wounds heal within an expected timeframe, usually within 30 days.
Chronic wounds are wounds that do not heal within an expected time frame, usually within 30 days. The most frequently occurring chronic skin wounds are pressure ulcers, venous stasis ulcers, and diabetic foot ulcers.
The National Pressure Ulcer Advisory Panel redefined pressure ulcers and the stages of pressure ulcers in February 2007 as follows:
Pressure Ulcer Definition
A pressure ulcer is a localized injury to the skin and/or underlying tissue usually over a bony prominence, as a result of pressure, or pressure in combination with shear and/or friction. A number of contributing or confounding factors are also associated with pressure ulcers; the significance of these factors is yet to be elucidated.
Pressure Ulcer Stages
Suspected Deep Tissue Injury
Purple or maroon localized area of discolored intact skin or blood-filled blister due to damage of underlying soft tissue from pressure and/or shear. The area may be preceded by tissue that is painful, firm, mushy, boggy, warmer or cooler as compared to adjacent tissue.
Deep tissue injury may be difficult to detect in individuals with dark skin tones. Evolution may include a thin blister over a dark wound bed. The wound may further evolve and become covered by thin eschar. Evolution may be rapid exposing additional layers of tissue even with optimal treatment.
Intact skin with non-blanchable redness of a localized area usually over a bony prominence. Darkly pigmented skin may not have visible blanching; its color may differ from the surrounding area.
The area may be painful, firm, soft, warmer or cooler as compared to adjacent tissue. Stage I may be difficult to detect in individuals with dark skin tones. May indicate "at risk" persons (a heralding sign of risk)
Partial thickness loss of dermis presenting as a shallow open ulcer with a red pink wound bed, without slough. May also present as an intact or open/ruptured serum-filled blister.
Presents as a shiny or dry shallow ulcer without slough or bruising.* This stage should not be used to describe skin tears, tape burns, perineal dermatitis, maceration or excoriation.
*Bruising indicates suspected deep tissue injury
Full thickness tissue loss. Subcutaneous fat may be visible but bone, tendon or muscle are not exposed. Slough may be present but does not obscure the depth of tissue loss. May include undermining and tunneling.
The depth of a stage III pressure ulcer varies by anatomical location. The bridge of the nose, ear, occiput and malleolus do not have subcutaneous tissue and stage III ulcers can be shallow. In contrast, areas of significant adiposity can develop extremely deep stage III pressure ulcers. Bone/tendon is not visible or directly palpable.
Full thickness tissue loss with exposed bone, tendon or muscle. Slough or eschar may be present on some parts of the wound bed. Often include undermining and tunneling.
The depth of a stage IV pressure ulcer varies by anatomical location. The bridge of the nose, ear, occiput and malleolus do not have subcutaneous tissue and these ulcers can be shallow. Stage IV ulcers can extend into muscle and/or supporting structures (e.g., fascia, tendon or joint capsule) making osteomyelitis possible. Exposed bone/tendon is visible or directly palpable.
Full thickness tissue loss in which the base of the ulcer is covered by slough (yellow, tan, gray, green or brown) and/or eschar (tan, brown or black) in the wound bed.
Until enough slough and/or eschar is removed to expose the base of the wound, the true depth, and therefore stage, cannot be determined. Stable (dry, adherent, intact without erythema or fluctuance) eschar on the heels serves as "the body's natural (biological) cover" and should not be removed.
NOTE: The majority of patients will achieve sufficient wound closure within six weeks, although some patients may require a longer period of time.
Negative pressure therapy or suction devices cleared by the U.S. Food and Drug Administration (FDA) for the purpose of treating chronic wounds include, but are not limited to: V.A.C.® (Negative pressure therapy Assisted Closure®) Therapy™ (Kinetic Concepts, Inc); Versatile 1™ Wound Negative pressure therapy System (Blue Sky Medical), and RENASYS EZ and RENASYS GO systems (The latter is a portable system) (Smith-Nephew).
A non-powered NPWT device, the SNaP Wound Care System from Spiracur, is a Class II device requiring notification to market but not having FDA premarket approval. It received 510(k) marketing clearance from the FDA in 2009 (K081406) and is designed to remove small amounts of exudate from chronic, traumatic, dehisced, acute, subacute wounds and diabetic and pressure ulcers.
In November 2009, the FDA issued an alert concerning complications and deaths that had been associated with NPWT systems. An updated alert was issued in February 2011. Contraindications to the use of NPWT systems include the following conditions as noted by a November 2009 FDA alert: necrotic tissue with eschar, untreated osteomyelitis, nonenteric and unexplored fistulas, malignancy in the wound, exposed nerve, exposed anastomotic site, and exposed organ. The FDA reported that the safety and effectiveness of NPWT systems in newborns, infants and children has not been established at this time and currently, there are no NPWT systems cleared for use in these populations.