Misconcepts in the usage of Negative Pressure Wound Therapy (NPWT)

Negative Pressure Wound Therapy (NPWT) is a therapeutic technique commonly used to treat diabetic chronic ulcers.

Following are the main objectives to achieve through NPWT:

1. Exudate Control: When an injury occurs, leaving the skin exposed and unprotected, the cells secrete a fluid known as Exudate that gets filtered from the circulatory system. It is pale to straw yellow in color, contains bioactive fibrin, serum and White Blood Cells (WBCs). This is to keep the external wound environment moist so that it would prevent the dehydration of exposed cells. Now it must be clear, why wound produces exudate and how it plays a role in wound healing.
2. Cell and Vascular migration to the wound surface: In NPWT, suction pressure is used to remove the excess exudate and promote cellular and vascular migration. However, the use of NPWT as the only treatment method is not sufficient and an ultimate ideal method to complete the process of wound healing is required.

Misconcepts in the usage of NPWT

Misconcept 1:

Direct Contact of a synthetic foam to the Wound surface is NOT an ideal method:

An interventional biological skin substitute, to protect the exposed cells in a wound, is important compared to a synthetic polymeric material. In the current NPWT treatment methods, wound cells are exposed to a non tissue–regenerative polymeric sponge (like open-pore polyurethane black or green foam or a white polyvinyl alcohol sponge, Ref. 1) that do not encourage an ideal healing response (Fig. 1). The very purpose of NPWT is to minimize or stop the exudation/drainage and that may not be achieved, as the synthetic foam cover is NOT an appropriate material to provide a proper contact surface for the cells to feel comfortable to stop its exudation completely. The drainage may continue and would be un-necessarily longer and the NPWT treatment may have to be extended resulting in delayed healing and higher cost of patient care.

Solution: The only way to resolve the above problem is by applying a biological, bio-compatible matrix membrane like a skin substitute in between the wound surface and the regular synthetic polymeric foam (Fig. 2). So, in the NPWT treatment, applying a bioactive tissue regenerative matrix membrane would immensely enhance the rate of closure of the wound and thereby would reduce the Cost of Patient Care.

Misconcept 2:

Making holes or fenestration to Skin Substitute may not be ideal, compared to Slits made by a Scalpel to allow the drainage:
When the biocompatible skin substitute membrane is in direct contact to the wound bed for better bioactivity, it should not be fenestrated to have a large opening that could allow easier microbial invasion to infect the wound.

Solution: If the surgeon makes simple slit openings using a surgical scalpel blade on the surface of the membrane to allow the flow of the fluids, it would minimize the invading germs and also would act as a natural valve (similar to the valve in veins) to permit the unidirectional flow of exudate towards the suction (Fig 3).

Fig 3: Unidirectional flow of exudate through a slit opening on the membrane

Misconcept 3:

Currently used frequency of changing the foam Dressing or the skin-substitute may not be ideal:

Dr. David Armstrong, who is highly respected and considered as a Guru in DFU treatments, seems to emphasize the change of the synthetic foam dressing once in every 48 hrs (Ref. 2). This suggestion may not be ideal for a better wound healing. From a scientific point of view, the tissue granulation process takes at least 4 to 5 days when no infection prevails. Changing the synthetic dressing applied directly onto the wound surface once in 2 days or 48 hrs physically would disturb the surface cells involved in wound healing resulting in delayed progression of granulation.

Solution: Based on the above misconcept, it is immensely required to use a biocompatible skin substitute membrane (with proper slit openings to let the drainage pass through) between the synthetic polymeric foam and the wound surface (Fig. 2). Only then, the synthetic polymeric adsorbent sponge can easily be changed every 48 hours leaving behind the biological skin substitute undisturbed to let the wound heal well. The replacement of the biological skin substitute can be done, if needed, after approximately a week or even longer if the healing progresses without infection or excess exudation. This may be an ideal solution to keep the wound surface un-disturbed to complete the normal process of wound healing.

CONCLUSION: Usage of a non-biological adsorbent sponge might not be ideal and has to be intervened by a bioengineered skin substitute like biomaterial for a better clinical outcome (Ref. 3 & 4). “The application of an advanced tissue regenerative matrix naturally would reduce the amount of exudation and thereby would minimize the cost of longer usage of the NPWT. With these scientific merits, use of a combination therapy utilizing a biologically active membrane has to be recommended by the International Diabetes Federation (IDF) as a superior healing method for a successful management of DFU.”