Normothermic Wound Therapy
An optimal environment for wound healing is thought to include a moist normothermic (normal body temperature) environment, enhancing the subcutaneous oxygen tension and increasing the blood flow to the wound. A device called Warm-Up Active Wound Therapy®, approved by the United States Food and Drug Administration (FDA), attempts to create this environment. The device includes a noncontact bandage and warming unit designed to maintain 100% relative humidity and to produce normothermia in the wound and surrounding tissues. The bandage is composed of a sterile foam collar that adheres to the periwound (peripheral) skin, and a sterile transparent film that covers the top of the wound but does not touch it. An infrared warming card is inserted into a pocket of the film covering. Treatments are administered three times a day in one hour sessions.
Ultrasound (US) Wound Therapy
Low-frequency ultrasound (US) in the kiloherz range may improve wound healing. Several devices are available; one example is the MIST Therapy® system, which delivers ultrasonic energy to wounds via a saline mist without direct skin contact.
US is defined as a mechanical vibration above the upper threshold of human hearing (>20 KHz). US in the MHz range (1–3 MHz) has been used for the treatment of musculoskeletal disorders, primarily by physical therapists. Although the exact mechanism underlying its clinical effects is not known, therapeutic US has been shown to have a variety of effects at a cellular level including angiogenesis; leukocyte adhesion; growth factor and collagen production; and increases in macrophage responsiveness, fibrinolysis, and nitric oxide levels. More recently, the therapeutic effects of US energy in the kilohertz range have been examined. It has been proposed that low frequency US in this range may improve wound healing via the production, vibration, and movement of micron-sized bubbles in the coupling medium and tissue.
The mechanical energy from US is typically transmitted to tissue through a coupling gel. Several high-intensity US devices with contact probes are currently available for wound debridement. A noncontact low-intensity US device has been developed that does not require use of a coupling gel or other direct contact. The MIST Therapy™ System (Celleration) delivers a saline mist to the wound with low-frequency US (40 KHz); it includes a generator, a transducer, and a disposable applicator for discharge of prepackaged saline.
In 2004, the FDA reclassified these devices from class III to class II at the request of Celleration (K032378). As part of the reclassification, the FDA named this type of device as a "low energy ultrasound wound cleaner" which they defined as “a device that uses ultrasound energy to vaporize a solution and generate a mist that is used for the cleaning and maintenance debridement of wounds. Low levels of ultrasound energy may be carried to the wound by the saline mist.” In 2005, the Celleration MIST therapy device received marketing clearance (K050129) through the FDA's 510(k) process, “to promote wound healing through wound cleansing and maintenance debridement by the removal of yellow slough, fibrin, tissue exudates and bacteria.” Several wound drainage and wound vacuum systems were listed as predicate devices.
The FDA’s 510(k) process does not require data regarding clinical efficacy; this device was considered essentially equivalent to predicate powered suction pump devices based on the “use of mechanical energy to promote wound healing through means such as the removal of infectious material and other wound exudates.”
In 2007, the AR1000 Ultrasonic Wound Therapy System (Arobella Medical) received marketing clearance, listing the Celleration MIST system and several other ultrasonic wound debridement and hydrosurgery systems as predicate devices. The AR1000 system uses a combination of irrigation and US with a contact probe to debride and cleanse wounds. The indications are similar to that of the MIST system, listed as: “selective dissection and fragmentation of tissue, wound debridement (acute and chronic wounds, burns, diseased or necrotic tissue), and cleansing irrigation of the site for the removal of debris, exudates, fragments, and other matter.”