Negative pressure wound therapy

In negative pressure wound therapy, the wound is sealed airtight using a special wound dressing made of a sponge material or gauze. A pump connected to the dressing by a thin tube removes the wound secretions (fluids), which lowers the pressure around the wound and increases blood flow to the wound. It helps keep the wound moist too, which is also meant to improve the healing process. The wound dressing is usually changed regularly, depending on things like the type of wound.

Wounds heal in various ways, depending on factors like their shape and size. The types of healing are categorized as follows:

• Primary (first) wound healing: The edges of the wound are even and close together, so they can be joined together again – for instance, using stitches to close a cut made during surgery.
• Secondary (second) wound healing: The edges of the wound can’t simply be joined together because, for example, some of the tissue is missing, severely damaged or dead, or because the wound itself is infected. The body first needs to make new tissue to fill this gap. A procedure like a skin graft may be needed for the wound to heal.

Wounds can also heal by epithelial wound healing. This is where the wound is limited to the top layers of skin – such as a scrape or graze. It then heals quickly as the damaged tissue is replaced with new tissue, without any complications or scarring.

The Institute for Quality and Efficiency in Health Care (IQWiG, Germany) looked into whether negative pressure wound therapy has any advantages or disadvantages compared to standard wound treatment and care. They did one assessment for primary wound healing, and a separate assessment for secondary wound healing.

The IQWiG researchers looked for studies on the advantages and disadvantages of negative pressure wound therapy compared to standard treatment (such as a conventional wound dressing) for primary wound healing. They found a total of 45 studies with usable results. These studies looked at surgical wounds. Poor wound healing was expected in most of the patients who participated in the studies.

The initial results suggest that negative pressure wound therapy can improve wound healing within six weeks:

• With standard treatment, the wound healed in about 88 out of 100 people.
• With negative pressure wound therapy, the wound healed in about 95 out of 100 people.

The studies also suggested that negative pressure wound therapy helps to prevent mild infections.

Complications, especially serious ones, were equally common in both treatment groups. It is not clear which of the treatments resulted in less pain or shorter hospital stays: The studies showed conflicting results here. There was no difference in quality of life.

The IQWiG researchers also looked for studies on the advantages and disadvantages of negative pressure wound therapy compared to standard treatment for secondary wound healing. They found a total of 48 studies with usable results.

Overall, the studies suggest that negative pressure wound therapy can also help to heal these wounds. They found the following after six months:

• With standard treatment, the wound healed in about 35 out of 100 people.
• With negative pressure wound therapy, the wound healed in about 46 out of 100 people.

The treatment shortened the time the patients spent in the hospital, too. Study participants who were given the standard treatment stayed in the hospital for an average of 23 days (median value). Those who had negative pressure wound therapy were able to leave the hospital 5 days earlier on average.

Pain and complications (and especially serious pain and complications) were equally common for both treatments. The same is true for the number of amputations. Life expectancy was the same in both treatment groups.

It is not possible to say how negative pressure wound therapy affects quality of life: The study results were inconsistent here. The effects on the patient’s need for assistance and nursing care were not studied.

Overall, the research results showed that wounds heal better with negative pressure wound therapy than with standard treatment. Both led to a similar amount of side effects.

However, the researchers found a number of further studies in this area but couldn’t see the results because the studies hadn’t been published. These unpublished results could possibly lead to different conclusions, so negative pressure wound therapy may be less effective than currently believed.