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Negative pressure wound therapy (NPWT), marketed as wound VAC (Vacuum Assisted Closure), applies continuous or intermittent sub-atmospheric pressure to a wound through a foam or gauze dressing covered by an occlusive drape. The mechanisms of healing: removal of excess wound fluid and exudate reduces edema and bacterial burden; mechanical deformation of wound tissue stimulates cell proliferation and granulation tissue formation; increased local blood flow delivers oxygen and nutrients; the moist, closed environment optimizes the wound healing environment.
| Indications | Contraindications (Absolute) |
|---|---|
| Chronic, non-healing wounds (diabetic foot ulcers, pressure injuries Stage 3–4) | Necrotic tissue with eschar present (must debride first — VAC cannot heal over dead tissue) |
| Dehisced surgical wounds | Untreated osteomyelitis in the wound bed |
| Traumatic wounds with tissue loss | Malignancy in the wound |
| Skin grafts and flap coverage (to secure graft and promote take) | Exposed vasculature, nerves, anastomotic sites, or organs without protective tissue coverage |
| Sternal wounds post-cardiac surgery | Non-enteric or unexplored fistulas (can worsen by increasing drainage) |
| Setting | Typical Range | Clinical Notes |
|---|---|---|
| Continuous mode | -75 to -125 mmHg | Standard for most wounds; constant negative pressure; most common setting (-125 mmHg default for many devices) |
| Intermittent mode | -125 mmHg on, release to 0 for cycles | Evidence suggests may stimulate granulation more than continuous; less comfortable for patients; used for chronic wounds |
| Lower pressure (-50 to -75 mmHg) | Fragile tissue, skin grafts, painful wounds | Start lower for skin grafts (typically -75 to -100 mmHg to avoid shear on newly placed graft) |
Dressing changes are ordered every 48–72 hours (black foam) or every 12–24 hours (white/silver foam for infected or highly exudative wounds). Administer pain medication 30–60 minutes before dressing change — VAC dressing removal is painful. Maintain sterile technique throughout.
Removal: clamp the tubing, turn off the device, carefully remove the drape (slow, pulling parallel to skin, not lifting up), remove foam from the wound (count pieces in and pieces out — retained foam is a foreign body). Assessment: measure wound dimensions (length × width × depth), assess wound bed (percentage of granulation tissue, slough, or necrotic tissue), note drainage character and odor, assess periwound skin (maceration, breakdown).
Application: cut foam to fit the wound shape (do not overfill or underfill — foam should be in contact with all wound surfaces but not overpacked); place foam in wound; cut drape to cover foam plus 3–5 cm margin of intact periwound skin; apply drape without tension; pinch drape up to create a small bubble, cut a small hole through the bubble, apply the SensaT.R.A.C. pad over the hole; connect tubing; turn on device and confirm seal by observing foam collapse and hearing no leak sounds.
| Alarm | Most Likely Cause | Nursing Fix |
|---|---|---|
| Leak alarm (most common) | Air entering the system through a drape breach or poor seal | Listen/feel for leak; reinforce drape with additional strips; check all tubing connections; replace drape if needed |
| Canister full | Exudate has filled the collection canister | Clamp tubing, turn off device, replace canister, restart |
| Blockage/occlusion | Foam has collapsed completely (at target pressure), tubing kinked, or foam saturated | Check tubing for kinks; reposition tubing; if foam is completely flat and occluded, may need dressing change earlier than scheduled |
| Low battery | Device on battery power; battery depleting | Plug device into wall outlet |
Notify the provider or wound care team for: bright red bleeding from the wound (stop VAC, apply pressure, call immediately — arterial bleeding in the wound bed is a contraindication to VAC); wound appears to be enlarging rather than healing after 2 weeks of therapy; increasing malodor suggesting wound infection; periwound skin breakdown extending beyond the drape margin; exposed bone, tendon, or blood vessel identified in the wound bed.
Related guides: Wound care | Post-op complications
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