What is Negative Pressure Wound Therapy (NPWT)?
NPWT is a therapeutic technique commonly used to treat chronic diabetic ulcers. The technique employs the use of a sealed dressing connected to a vacuum pump to remove excess exudate from the wound environment.
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.
Set up of a conventional NPWT system:
A conventional NPWT system consists of the following materials
1.Synthetic polymeric foam dressing:
In chronic ulcers with open wound cavity, foam dressings are used as a filler material. Commonly used foam dressings include open-pore polyurethane black or green foam or a white polyvinyl alcohol sponge. These materials are non-tissue regenerative polymeric sponge and therefore, will not provide an ideal wound healing environment.
2.Film seal/occlusive dressing:
Once the open wound cavity is filled with a foam dressing, a flat film seal with the provision for a drain tube will be applied over the wound to create an air-tight space. This complete seal is essential to contain the negative pressure/vacuum at the wound region.
3.Drain tube connected to a negative pressure pump:
The negative pressure pump or the vacuum pump, now connected to the sealed dressing will make use of suction pressure between ˗125 mmHg & ˗75 mmHg to draw out excess exudate from the wound and increase blood supply to the wound site.
Frequency of dressing change and use of a pre-fenestrated membrane
In a conventional NPWT system, the dressing is typically changed every 48 hours. The reason for the frequent replacement is the inability of the material to manage the excess exudate secretion. In order to reduce the number of replacements needed, a pre-fenestrated membrane is chosen as an alternative. This is not advisable as the pre-fenestrated membrane will provide an easier path for pathogens to invade and infect the wound.