Negative pressure wound therapy (NPWT) is a non-surgical, evidence-based treatment used to promote healing and improve patient outcomes in acute, chronic, and complex wounds. Often referred to as “wound vac,” the abbreviation stands for vacuum-assisted closure. It has become standard adjunctive therapy in wound management across acute care, long-term care, outpatient clinics, and home health settings. For wound care clinicians, understanding how NPWT works, when to use it, and when to discontinue therapy is essential for improving patient outcomes and preventing complications.

Key Takeaways

A wound vac is a system that applies negative pressure evenly across the entirety of the wound site using a special vacuum device to promote healing in complex acute or chronic wounds. It works by removing exudate, reducing edema, improving perfusion, and stimulating granulation tissue formation. Dressings are typically changed every 48 to 72 hours, though more frequent changes may be required in infected wounds. The duration of therapy varies depending on wound characteristics and patient response. Therapy should be discontinued when goals are met, when the wound fails to progress, or when complications arise. Wound care nurses play a central role in patient selection, monitoring, documentation, and education throughout treatment.

What is a wound vac?

A wound vac is a medical device that delivers negative pressure wound therapy by applying controlled subatmospheric pressure to the wound bed. The system typically includes a foam or gauze dressing placed into the wound, an occlusive adhesive drape that creates an airtight seal, tubing that connects the dressing to a portable vacuum pump, and a canister that collects drainage. Once activated, the device creates suction within the sealed environment.

According to StatPearls Publishing through the National Library of Medicine, NPWT is used to manage a variety of wound types, including diabetic foot ulcers, pressure injuries, surgical wounds, traumatic wounds, and wounds requiring graft or flap support.¹ Its versatility has made it a valuable tool in both inpatient and outpatient wound care settings.

How does a wound vac work?

Negative pressure wound therapy supports healing through four distinct but linked actions.

Fluid removal (Exudate and Edema control): Removes excess exudate from the wound bed that is often loaded with enzymes harmful to healthy tissue. By continuously drawing fluid into a collection canister, NPWT helps reduce peri-wound maceration and may lower bacterial burden. This also reduces swelling in the area, which in turn improves microcirculation and enhances both oxygen and nutrient delivery to the wound bed.
Macrodeformation (Wound Edge Contraction): Negative pressure foam or gauze placed in the wound and connected to the vacuum pump will pull the wound edges together creating mechanical contraction. This action physically shrinks the wound, which can shorten healing time.
Microdeformation (Granulation tissue promotion): The foams’ porous structure applies a controlled mechanical stress to the individual cells in the wound bed — sometimes referred to as microstrain. The continuous suction then stimulates cellular proliferation, angiogenesis, and extracellular matrix production. Research published in the International Wound Journal describes how these mechanical forces help accelerate progression through the proliferative phase of healing.² The Agency for Healthcare Research and Quality (AHRQ) also recognizes NPWT as an advanced wound therapy used to promote wound contraction and granulation in appropriate patients.³

Wound Protection (Stabilization of the Environment): The semi occlusive cover provides a closed, moist, and warm environment conducive to healing. It also acts as a physical barrier, protecting the wound from outside bacteria and contamination.

What does a wound vac look like?

Clinically, a wound vac consists of a foam dressing, commonly black polyurethane foam or white polyvinyl alcohol foam, cut to fit the wound bed. The foam is covered with a clear adhesive drape to create an airtight seal. A small opening in the drape connects to tubing that attaches to a portable vacuum pump with a drainage canister.

When functioning properly, the foam appears compressed due to active suction. If the foam expands or the device alarms, this may indicate a leak in the seal or loss of negative pressure. Devices range from larger hospital-based units to smaller, disposable systems designed for home use.

How long does a wound vac stay on?

The length of time a wound vac stays in place depends on both dressing change frequency and overall treatment duration. In most cases, dressings are changed every 48 to 72 hours. If the wound is infected or heavily draining, dressing changes may be required every 24 hours.¹ Treat wound infection accordingly.

The total duration of therapy varies. Some wounds require only a few weeks of NPWT to achieve sufficient granulation tissue formation, while others may need longer courses depending on wound size, depth, perfusion status, glycemic control, nutritional status, and the presence of comorbidities. There is no universal timeframe. Regular reassessment is essential to determine whether the therapy remains appropriate and effective.

When should a wound vac be discontinued?

Negative pressure wound therapy should be discontinued when the therapeutic goal has been achieved, such as when the wound bed has developed adequate granulation tissue and is ready for closure, grafting, or transition to another dressing modality. Therapy should also be reconsidered if the wound fails to demonstrate measurable improvement. AHRQ recommends reassessing advanced therapies if there is no progress within two to four weeks.³ Additionally, if the patient is unable or unwilling to follow the medical plan of care, wound vac should be discontinued as maximum benefits might not be achieved.

NPWT is contraindicated in certain situations, including untreated osteomyelitis, necrotic tissue with eschar present, malignancy in the wound, uncontrolled bleeding, or exposed organs or vasculature without appropriate protection.¹ If any of these conditions develop, therapy should be stopped, and the care plan reevaluated. Additionally, patient intolerance, uncontrolled pain, or inability to maintain seal integrity may warrant discontinuation.

What does a wound care nurse need to know?

Wound care nurses are integral to the safe and effective use of NPWT. Proper patient selection begins with confirming indications and ruling out contraindications. Ongoing assessment includes monitoring seal integrity, evaluating exudate characteristics, measuring wound dimensions, and documenting tissue type and periwound condition. Accurate and consistent documentation supports both clinical decision-making and reimbursement requirements.

Nurses must also monitor for signs of infection, including increased drainage, odor, erythema, fever, or escalating pain. While NPWT can assist with exudate management, it does not replace appropriate infection control measures such as debridement or antibiotic therapy when indicated.

Pain management is another important consideration. Dressing changes can cause discomfort, particularly when foam adheres to granulation tissue. Premedication and gentle removal techniques can improve patient tolerance, along with the use of a non-adherent material layer before foam placement. Additional tips that may help would be to consider stopping therapy 15 minutes prior to dressing change or soak the wound and dressing with an appropriate solution before removal.

In home care settings, patient and caregiver education is critical. Teaching should include how to maintain the seal, respond to alarms, charge the device, and recognize complications. Because therapy effectiveness depends on continuous negative pressure, adherence directly impacts healing outcomes.

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Frequently Asked Questions

Is a wound vac painful?

Patients may experience mild discomfort from suction or during dressing changes. Appropriate pressure settings and premedication can help minimize pain. Always contact the prescribing clinician if there is a sudden increase or change in the pain characteristics.

Can a patient go home with a wound vac?

Yes. Portable NPWT systems are commonly used in home health settings with proper training and follow-up.

How much negative pressure is typically used?

A common setting is approximately –125 mmHg when using black foam dressings, although pressure settings may vary based on wound type and clinical goals. ¹

Does a wound vac prevent infection?

NPWT helps manage exudate and may reduce bacterial burden, but it does not replace surgical debridement or systemic antibiotics when infection is present. ³

What happens if the seal breaks?

If the seal is lost, suction stops, and the device typically alarms. The foam will expand, indicating loss of negative pressure. The dressing should be reinforced promptly to restore therapy. Never leave the foam in the wound for longer than two hours with the wound vac turned off or not working properly. If you are unable to find or repair the leak or if the machine or dressing is malfunctioning or turned off for more than two hours, the whole wound vac and all the dressings in the wound bed need to be removed. The wound must be thoroughly washed, and a new dressing placed.

References

StatPearls Publishing. (2023). Negative pressure wound therapy. National Library of Medicine. https://www.ncbi.nlm.nih.gov/books/NBK576388/
Orgill, D. P., & Bayer, L. R. (2013). Negative pressure wound therapy: Past, present and future. International Wound Journal, 10(Suppl 1), 15–19. https://doi.org/10.1111/iwj.12167
Agency for Healthcare Research and Quality. (2014). Negative pressure wound therapy devices. Technology assessment report.
Net Health. (2025). What is a Wound Vac? https://www.nethealth.com/blog/what-is-a-wound-vac/#:~:text=So%20What%20Is%20a%20Wound,meters%20in%20the%20same%20class.

What Is a Wound Vac? Our Guide to Negative Pressure Wound Therapy