What Is NPWT in Wound Care? Negative Pressure Wound Therapy Explained

What Is Negative Pressure Wound Therapy?

Negative pressure wound therapy (NPWT) is a wound treatment that uses a sealed dressing connected to a suction pump to apply sub-atmospheric pressure directly to the wound bed. The pump draws air out of the sealed dressing, creating a controlled vacuum that pulls fluid from the wound, reduces swelling, and mechanically stimulates the tissue underneath.

The device is commonly referred to as a wound VAC (vacuum-assisted closure), though that is a brand name. Multiple manufacturers produce NPWT systems, and the therapy itself is device-agnostic -- the clinical mechanism is the same regardless of which pump delivers the pressure.

How Does NPWT Work?

The sealed dressing -- typically a foam or gauze interface -- is placed directly on the wound bed and covered with an adhesive drape to create an airtight seal. A suction tube connects the dressing to a portable pump, which applies continuous or intermittent negative pressure, usually between -75 mmHg and -125 mmHg.

This sub-atmospheric pressure produces four therapeutic effects:

Exudate removal. The vacuum draws wound fluid away from the tissue, keeping the wound bed moist without allowing fluid accumulation that slows healing.

Edema reduction. Removing excess interstitial fluid reduces tissue swelling around the wound, which improves oxygen delivery to the wound margins.

Granulation tissue promotion. The mechanical stress of negative pressure stimulates cellular proliferation at the wound surface, accelerating the formation of granulation tissue that fills the wound from the base up.

Increased local blood flow. Studies demonstrate that sub-atmospheric pressure increases perfusion to the wound bed and periwound tissue, supporting the metabolic demands of active wound healing.

Which Wounds Benefit from NPWT?

NPWT is indicated for wounds that need active fluid management, granulation tissue stimulation, or both. The most common clinical applications include:

Deep pressure ulcers (Stage 3 and 4) with moderate to heavy exudate and a clean or debrided wound bed
Post-surgical wound dehiscence where the incision has separated and is healing by secondary intention
Large chronic wounds with heavy exudate that overwhelm standard dressing absorption capacity
Traumatic wounds with significant tissue loss requiring granulation before closure or grafting
Diabetic foot ulcers that have failed conservative treatment and have adequate perfusion to support healing

NPWT is not a first-line therapy. Most LCDs require documented failure of standard wound care before NPWT initiation is covered. For the documentation requirements that support NPWT coverage, see our 4-week rule guide.

Two Delivery Models: DME-Provided vs Physician-Applied

DME-provided NPWT is the traditional model. A durable medical equipment company delivers the pump and supplies to the patient's home or facility. The clinician places the initial dressing, and subsequent dressing changes are performed by home health staff, facility nurses, or the patient. The DME company bills for the pump rental and supply kit under HCPCS E2402 and associated supply codes. The physician does not bill for the device -- only for the dressing application procedure.

Physician-applied disposable NPWT uses a single-use, portable device that the clinician applies during the visit. These disposable systems (such as PICO or Prevena) do not require a DME order. The clinician bills for the application, and the device cost is built into the procedure reimbursement or billed separately depending on the payer. This model is increasingly common in mobile wound care, where coordinating DME delivery to a patient's location adds logistical complexity.

For the billing codes and modifier rules that apply to each model, see our NPWT billing guide and our Medicare NPWT billing FAQ.

Treatment Duration and Dressing Changes

NPWT dressing changes are typically performed every 2-3 days. More frequent changes may be needed for wounds with heavy drainage or signs of infection. Less frequent changes -- every 3-5 days -- may be appropriate for wounds with minimal exudate once granulation is well established.

Total treatment duration varies by wound size and response, but most wounds treated with NPWT show measurable improvement within 2-4 weeks. If the wound is not progressing after 4 weeks of NPWT, the treatment plan should be reassessed.

Contraindications

NPWT should not be used on wounds with:

Exposed blood vessels or organs -- sub-atmospheric pressure on exposed vasculature creates hemorrhage risk
Malignancy in or near the wound bed -- mechanical stimulation may promote tumor growth
Untreated osteomyelitis -- NPWT over infected bone can drive bacteria deeper into the tissue; osteomyelitis must be treated before NPWT initiation
Necrotic tissue with eschar -- the wound bed must be debrided to viable tissue before NPWT placement
Non-enteric or unexplored fistulas -- negative pressure may worsen the fistula tract