Technology helps heal chronic wounds

Physicians have been taking advantage of technology to help wounds heal for centuries by using bandages, stitches, and more recently, staples and adhesives. And fortunately, most wounds eventually heal themselves, But there are situations in which wounds just won’t heal. These chronic wounds — usually defined as those that show no improvement after 30 days — include bed sores in paralyzed or immobilized people, foot and leg sores on diabetics, and large traumatic wounds due to car accidents or combat.

Fortunately, biomedical engineers and material scientists have developed several new devices and therapies that work on chronic wounds.

Better dressings
One of the simplest new approaches to wound therapy are bioceramic dressings from Cerdak, a South African company. The FDA-approved dressing, called Cerdak, consists of a sachet of loosely packed alumina-oxide spheres ranging in diameter from 0.2 to 1 mm. There are many voids between the nonallergenic spheres and each sphere has many pores. In fact, pores make up about 75% of the spheres’ volume. The pores average about 2 to 5 µm in diameter, which creates capillary suction forces of about 56 kPA when in contact with liquids.

When placed in or near a wound, the spheres attract and retain fluid. As they remove older fluid, the body reacts by supplying more, which contains fresh antigens and the growth hormones and proteins needed to fight infection, grow new tissue and blood vessels, and heal the wound. And studies show the spheres reduce the amount of bacterial toxins and free radicals, which are both inimical to healing.

The standard Cerdak dressing is about the size of a tea bag, but the company makes specialized dressings for wounds in various locations. For example, there are large ones for cavity wounds, specially shaped ones for finger-tip and toe injuries, smaller dressings for facial wounds, and die-cut versions for nonhealing wounds around catheter entry points. The dressings come with and without adhesives.

Negative pressure
Negative-pressure wound therapy (NPWT) involves applying a vacuum to a wound, about –125-mm Hg for up to 22 hr a day, continuous or intermittent, and sealing the wound to retain the vacuum. NPWT has proven effective on acute and chronic wounds, as well as second and third-degree burns. Doctors have to be careful where NPWT is used, but there seems to be no downside to the therapy.

NPWT is thought to cure wounds through five proven mechanisms:
• Suction pulls edges of a wound closer together, reducing the distance needed to be filled by new tissue or even completely closing the wound.
• Stimulates tissue growth that will fill in the wound and replace lost tissue.
• Continually cleans wound, which reduces the bacteria count and chances of infection, and removes substances that inhibit healing.
• Removes pus and other fluids exuded by the wound.
• Reduces swelling and edema, which takes pressure off surrounding capillaries and lets blood flow back into the area.