Wound VAC nursing: a guide to negative pressure wound therapy

Negative pressure wound therapy (NPWT) — marketed most widely under the KCI V.A.C. brand — is one of the more technically demanding wound care modalities a nurse will manage. You will encounter it on surgical floors, in the ICU, in wound care clinics, and in home health. Nursing students often find NPWT intimidating because it combines hands-on dressing technique with device management and critical assessment skills. This guide breaks it all down: how the therapy works, when it is and is not appropriate, how to change the dressing step by step, what to assess at every change, and how to handle the alarms and complications that show up most often on the NCLEX.

Quick-reference overview

How NPWT works

NPWT applies subatmospheric pressure — pressure below atmospheric baseline — to the wound environment through a sealed foam dressing connected to a suction device and collection canister. The mechanism produces four simultaneous therapeutic effects:

1. Mechanical wound closure. Negative pressure draws wound edges toward the center, physically reducing wound dimensions over time.
2. Exudate removal. Excess fluid, inflammatory mediators, and bacteria are continuously evacuated from the wound bed into the canister, reducing the bacterial load and bioburden.
3. Edema reduction. Removing interstitial fluid decreases periwound edema, which improves local perfusion and oxygen delivery to healing tissue.
4. Granulation tissue stimulation. The microdeformational forces created by the foam against the wound bed activate fibroblast migration and angiogenesis, accelerating the growth of healthy granulation tissue.

Pressure settings

The standard therapeutic range is –75 to –125 mmHg. The exact setting depends on wound type and patient tolerance:

• –75 mmHg: Used for skin grafts and flaps, where higher suction could disrupt the graft-to-bed interface and impair take. Also used when patients cannot tolerate higher pressures.
• –125 mmHg: The default for most chronic wounds and surgical dehiscence. Provides more aggressive exudate removal and granulation stimulation.

Continuous vs. intermittent mode

Continuous mode maintains steady negative pressure and is the standard approach. It is better tolerated for most patients and used as first-line.

Intermittent mode cycles between negative pressure and atmospheric pressure at set intervals. It generates stronger macrostrain forces during the pressure-off phases and may enhance wound contraction in select cases, but it is less comfortable and not appropriate for all wound types. Providers specify the mode in the order.

Indications and contraindications

Getting indications and contraindications right is a persistent NCLEX challenge. The question will often present a clinical scenario and ask whether NPWT is appropriate — the correct answer almost always hinges on one of the absolute contraindications.

The clinical principle for NCLEX: NPWT augments healing — it does not treat infection, remove necrosis, or replace surgical management. Every contraindication stems from a scenario where applying negative pressure would either worsen the underlying problem or create a new dangerous one.

Foam selection: black vs. white

Foam choice is a clinically significant decision, not a preference. The two options have different structural properties that produce different effects on the wound bed.

Black polyurethane foam (GranuFoam) This is the standard foam used in most NPWT applications. Its open-cell pore structure transmits negative pressure evenly across the wound surface, generates microdeformational forces that stimulate granulation tissue, and handles high exudate volumes well. Use black foam for: chronic wounds, pressure injuries, dehisced wounds, traumatic wounds, and any wound where aggressive granulation promotion is the goal.

White polyvinyl alcohol (PVA) foam (WhiteFoam) White foam is denser with smaller pore sizes. It transmits negative pressure but produces less aggressive tissue deformation, which makes it the choice when the wound bed is fragile or when anatomical structures create risk. Use white foam for:

• Tunneling wounds (where foam needs to be inserted into a tract without damaging tissue walls)
• Wounds with exposed or at-risk vessels, nerves, or tendons
• Wounds where granulation tissue is already well-established and protection is more important than stimulation
• Patients with pain sensitivity where less tissue disruption is clinically indicated

NCLEX tip: If a question describes a wound near an exposed tendon or asks about tunneling, white foam is the correct choice. If a question asks about a chronic diabetic ulcer needing granulation, black foam is correct.

Dressing change procedure

NPWT dressing changes require more preparation and technique than standard dressing changes. Pre-medicate the patient 30 minutes before starting (discussed in the pain management section). Gather all supplies before entering the room — interrupted setup wastes time and increases infection risk. This procedure aligns with current sterile technique nursing principles.

Supplies needed: PPE (gloves, gown, mask if indicated), new foam of correct type, transparent occlusive draping (NPWT-specific), wound irrigation solution if ordered, skin barrier/prep (for periwound protection), tubing and new canister if needed, measuring device (ruler or wound measuring guide), wound assessment documentation tool.

Step-by-step procedure

1. Verify the order. Confirm foam type, pressure setting, mode (continuous vs. intermittent), and change frequency in the provider orders before touching the patient.

2. Perform hand hygiene and apply PPE. Wound VAC dressings carry significant exudate and infection risk. Gown up appropriately.

3. Turn off the device. Press the power button or therapy button to stop suction before attempting foam removal. Removing foam while suction is active causes significant patient pain and can traumatize granulation tissue.

4. Clamp the tubing. Clamp the tubing close to the dressing before disconnecting. This prevents air entry and minimizes exudate spill.

5. Remove the occlusive drape. Peel back the drape slowly from the edges toward the center. If the drape has adhered firmly to the periwound skin, apply gentle traction and use skin-safe adhesive remover if available. Rushed drape removal causes medical adhesive-related skin injury (MARSI) — a preventable complication.

6. Remove the foam. Foam frequently adheres to the wound bed, especially after the full 72-hour wear time. Soak the foam with normal saline and allow 1–2 minutes of contact time before attempting removal. This softens the foam-tissue interface and significantly reduces pain and trauma. Remove the foam gently — never forcefully pull adherent foam from a wound. Count all foam pieces removed. The piece count must match the number placed at the prior change.

7. Assess the wound. This is a critical nursing responsibility (detailed in the next section). Document wound dimensions, tissue type, drainage, periwound condition, and wound edges before placing the new dressing.

8. Irrigate if ordered. Use the prescribed solution (typically normal saline). Deliver at appropriate pressure (8–15 psi for most wounds — a 35 mL syringe with a 19-gauge angiocatheter delivers approximately this pressure). Gently pat dry with gauze.

9. Apply skin barrier to periwound skin. Skin prep/barrier wipes applied 3–5 cm beyond the wound margin protect periwound skin from MARSI and maceration from the occlusive drape adhesive. Allow it to dry completely before draping.

10. Cut foam to wound dimensions. Cut the foam to fit the wound bed with contact on all wound surfaces. Do not cut the foam smaller than the wound (leaves unprotected wound surface) or pack it tightly (increases pressure at the packing point and can cause pressure injury to wound edges). The foam should contact the wound bed — not be compressed into it.

11. Place the foam. For tunneling wounds using white foam, gently insert the foam into the tunnel. Document how many pieces are placed.

12. Cover with occlusive draping. Apply the transparent drape to overlap 3–5 cm beyond the foam margin onto intact periwound skin on all sides. Press down firmly to ensure an airtight seal. Pay close attention to skin folds, bony prominences, and irregular anatomy — these are where leaks occur.

13. Attach the tubing and canister. Connect the NPWT-specific tubing to the drape port, then connect to the canister and device.

14. Activate the device and verify the seal. Turn therapy on. Within 30–60 seconds, the foam should visibly collapse and shrink — this confirms the seal is intact and negative pressure is being achieved. If the foam does not collapse, an air leak is present.

Seal verification: If foam does not collapse, systematically check: (1) all drape edges; (2) where tubing exits the drape; (3) any bridges placed over bony prominences or skin folds; (4) proximity to ostomies or drain sites. Re-reinforce leaking edges with additional drape material.

Wound assessment at dressing changes

Every NPWT dressing change is a structured assessment opportunity. This is where you identify whether the therapy is working, whether complications are developing, and whether the wound plan needs to change. This assessment integrates with the principles described in wound assessment.

Dimensions: Measure length × width × depth at every change using a standardized technique (greatest length, greatest width perpendicular to length, greatest depth). Wound dimensions should be decreasing over the course of NPWT — a wound that is not contracting after 2–4 weeks warrants provider reassessment of the therapy plan.

Tissue type: Document the percentage of the wound base covered by each tissue type:

• Granulation tissue (beefy red, moist, bumpy) — the target tissue. Should increase over time.
• Slough (yellow/tan, soft, stringy) — non-viable tissue. Should decrease with effective NPWT.
• Eschar (black/brown, hard) — should not be present when NPWT is initiated. If eschar develops or was missed at initiation, notify the provider — NPWT is contraindicated until debridement occurs.
• Epithelial tissue (pale pink, fragile edges migrating inward) — a sign of advanced healing, typically seen as the wound approaches closure.

Drainage characteristics: Document color, consistency, volume (estimated), and odor. Sanguineous (bloody) drainage is expected for the first 24–48 hours after placement or changes but should transition to serosanguineous and then serous as healing progresses. Purulent drainage, foul odor, or significant increases in drainage volume warrant provider notification and reassessment for wound infection — see infection control nursing for assessment principles.

Periwound skin: Assess for maceration (softening, white discoloration), MARSI (erythema, blistering, skin stripping at drape margins), and signs of spreading infection (erythema, warmth, induration extending beyond the wound edge). These findings require immediate intervention and provider notification.

Wound edges: Edges should be progressively advancing toward the wound center. Rolled, hyperkeratotic, or epibolic edges suggest the wound has stalled and may need debridement.

Canister management and alarm troubleshooting

Pain management

NPWT is one of the more uncomfortable wound care interventions, and the dressing change itself is typically the most painful part. Adherent foam pulling away from granulation tissue generates significant nociceptive pain. Inadequate analgesia is one of the most common reasons patients refuse or delay NPWT dressing changes — delays that then increase infection risk and worsen outcomes.

Pre-medication protocol: Administer prescribed analgesics 30 minutes before starting the dressing change. For patients on scheduled opioids, time the dressing change to coincide with the peak effect window. For patients using oral analgesics only, coordinate timing with the pharmacy and nursing schedule.

Foam soaking technique: Before removing foam, flood the wound site with normal saline and allow 1–2 minutes of soak time. The saline dissolves the protein bonds between foam and granulation tissue. This is the most impactful single technique for reducing procedural pain at dressing changes. Do not rush this step.

Non-pharmacological adjuncts: Positioning the patient to minimize tension on the wound region, providing distraction (music, conversation), and coaching the patient through slow breathing during the most uncomfortable removal phase all contribute to procedural comfort.

Ongoing assessment: Use a validated pain scale (pain assessment nursing) at every dressing change, both before pre-medication and after the procedure. If pain is consistently poorly controlled, notify the provider — the pressure setting may need adjustment downward or the foam type may need to change.

Patient education

Many NPWT patients are discharged home with their device. Effective discharge teaching nursing is essential for safety and therapy compliance. Home health nurses will reinforce these points on each visit, but the inpatient nurse who first educates the patient sets the foundation.

Device portability: Modern NPWT devices are compact and battery-powered. Ambulatory patients can carry the device with them. Demonstrate how to manage the tubing and carry the device without kinking the tubing. The device does not need to be stationary.

Bathing and hygiene: The patient must not shower or submerge the wound while the NPWT device is connected. Sponge bathing around the dressing is appropriate. If the patient has a removable device for hygiene, this should be explicitly ordered and timed — the dressing must remain intact and the device reconnected promptly.

Alarm response: Teach the patient to recognize the three common alarms (leak, full canister, blocked tube) and know that an alarm does not mean the wound is harmed. For home patients: check tubing, check drape edges, call the home health nurse or outpatient wound clinic if the alarm cannot be silenced. Never manipulate pressure settings.

Activity restrictions and wound protection: No pressure or weight-bearing directly on the wound site unless specifically cleared by the provider. Protect the device from extreme temperatures. Sleep positioning should avoid lying on the device or tubing.

When to call for help: Any of the following require an immediate call: bright red blood in the tubing or canister, new severe pain, fever, worsening odor, or an alarm that will not clear.

NCLEX tips

• NPWT applies subatmospheric pressure — pressure below atmospheric — to the wound bed, typically –75 to –125 mmHg.
• The KCI V.A.C. (Vacuum Assisted Closure) system is the most common brand name; the generic clinical term is NPWT (Negative Pressure Wound Therapy).
• NPWT promotes wound healing through four mechanisms: mechanical wound closure, exudate removal, edema reduction, and granulation tissue stimulation.
• Absolute contraindication #1 — malignancy in the wound. Never apply NPWT to a wound that contains or is suspected to contain cancerous tissue.
• Absolute contraindication #2 — untreated osteomyelitis. Treat the bone infection first; NPWT is not appropriate until systemic treatment is established.
• Absolute contraindication #3 — necrotic tissue/eschar. Debride first. NPWT does not remove necrosis — it requires a clean wound bed to be effective.
• Absolute contraindication #4 — exposed vessels, nerves, or organs. Direct foam contact with these structures risks erosion and catastrophic hemorrhage.
• Black polyurethane foam = standard choice for most wounds (promotes granulation tissue).
• White PVA foam = tunneling wounds, fragile tissue, wounds near vessels or nerves (less aggressive deformation).
• Dressing changes every 48–72 hours is the standard; never leave in place beyond 72 hours due to infection risk.
• For skin grafts and flaps, use a lower pressure setting (–75 mmHg) to avoid disrupting graft-to-bed interface.
• Foam must be cut to wound shape and placed with contact — not tightly packed. Tight packing creates pressure points at wound edges.
• The occlusive drape must overlap 3–5 cm beyond the foam margin onto intact periwound skin for an adequate seal.
• Foam collapse after device activation is visual confirmation of an intact seal and effective negative pressure delivery.
• Bloody drainage in the canister = stop therapy immediately and notify the provider. This is a high-acuity finding.
• Pre-medicate 30 minutes before dressing changes and soak foam with normal saline before removal to reduce procedural pain.
• Canister should be changed when full or every 3–5 days. Document volume, color, and consistency of drainage at each change.
• A low-pressure alarm almost always means an air leak — check drape edges, tubing connections, and skin folds.
• Wound dimensions (L × W × D) should decrease over time with effective NPWT. A wound that is not contracting after 2–4 weeks warrants reassessment.
• NPWT does not treat infection — it can be used alongside antibiotic therapy for managed infections, but infection must be under active treatment first.

NCLEX practice scenarios

Related skills

• Wound care nursing — foundational dressing selection, wound bed preparation, and moist wound healing principles that underpin NPWT decisions
• Pressure injury nursing — Stage 3 and 4 pressure injuries are among the most common indications for NPWT; staging and management context
• Wound assessment — systematic wound measurement and documentation, which is performed at every NPWT dressing change
• Infection control nursing — PPE selection, standard precautions, and recognizing wound infection — all relevant to safe NPWT management
• Sterile technique nursing — principles of aseptic technique applied during NPWT dressing changes
• Pain assessment nursing — validated pain tools and assessment principles used to manage procedural pain at NPWT changes
• Discharge teaching nursing — structured patient education framework for home NPWT management
• Osteomyelitis nursing — osteomyelitis is a contraindication to NPWT until treated; understanding the relationship between bone infection and wound management is clinically important