Negative Pressure Wound Therapy (NPWT): Principles, Tips & Techniques

1. Negative Pressure Wound Therapy (NPWT): Principles, Tips & Techniques Mary Arnold Long, MSN, RN, CRRN, CWOCN-AP, ACNS-BC Mid East Region WOCN Conference 2010

2. Disclosures • Speakers Bureau Healthpoint Medical • Consultant SpanAmerica • Artwork/slide content have been provided by: • ConvaTec • KCI • ITI • Premco • Prospera • Smith & Nephew • Spiracur • Joseph B. Warren, LTC AN, First Army Command

3. NPWT Definition • The use of sub-atmospheric pressure to promote or assist wound healing or to remove fluids from a site.

4. NPWT History • NPWT concepts utilized in Eastern medicine as an adjunct to acupuncture (cupping) • NPWT has been in literature approx. 50 years (Fleck 2004) • “Kremlin Papers” (Usupov 1987, Davydov 1986, Davydov 1991) • Chariker & Jeter (1989) • Morykwas & Argenta (1990’s) • Various & sundry techniques have been improvised to provide negative pressure

5. NPWT – TheTerminology • Various terms are used for NPWT • Vacuum-Assisted Wound Closure – V.A.C.® • Topical Negative Pressure – TNP • Vacuum Sealing Technique – VST • Sealed Surface Suction – SSS • Negative Pressure Therapy - NPT • Negative Pressure Wound Therapy – NPWT • NPWT is the most appropriate term • V.A.C.® is a registered trademark • TNP is too narrow • VST, SSS and NPT are too general Slide courtesy of Smith & Nephew

6. NPWT – The Devices • Wound VAC® – KCI • EZ Care™/Vista™(formerly Versatile One) – Smith & Nephew (formerly BlueSky) • Renasys – Smith & Nephew • Engenex – ConvaTec (Boehringer Wound Systems) • Invia (Medela) • Prospera PRO-I System (Medica-Rents) • Svedman Wound Treatment System (Innovative Therapies) • Venturi System (Talley Group) • Kalypto (Kalypto Medical) • Wound VAC® – KCI • Includes ActiVAC®, InfoVAC®, VAC®Freedom, VAC®ATS, VAC®Via • EZ Care™ - Smith & Nephew (formerly Versatile One – BlueSky) • Engenex® (Boehringer Wound Systems) – ConvaTec • Genadyne A4 – Genadyne Biotechnologies Inc. • Kalypto - Kalypto Medical • Medela® - Invia • MoblVac® - Ohio Medical • Prodigy™ - Premco Medical Systems, Inc. • Prospera PRO-I™ & PRO-II™ Systems – Medica Rents • Renasys – Smith & Nephew • Svedman™ & Sved™ Systems - Innovative Therapies • Venturi™ System - Talley Group

7. Foam-Based NPWT • Reticulated Black Foam • Excellent for promoting granulation tissue formation via “macrostrain” • White foam (polyvinylalcohol) • More dense • Better for undermined/tunneled areas • Silver Reticulated Foam (KCI only) • Green Foam (Molnlycke – Europe) • Devices: • KCI Wound VAC (Granufoam TM; Versfoam TM) • Prodigy • Svedman Svamp • Smith & Nephew Renasys Foam • Medela (AvanceTM Green Foam)

8. Gauze/Drain-Based NPWT • Based onChariker-Jeter method • Different drains used with gauze • Excellent for wounds with undermining/tunneling • Less pain associated with dressing change • May be due to less tissue ingrowth into dressing medium (Borgquest, Gustafsson, Ingemannss & Malmsjo, 2009) • EZ Care/Vista, Genadyne, Invia, ITI, Mobilvac, Prodigy, Prospera, Renasys, Venturi

9. Other NPWT • Bio-dome Technology • Engenex • Canister-freeTechnology • Kalypto

10. NEWS FLASH • SNaP™ (Spiracur) • Spring operated power source • 3 different cartridges provide -75, -100 or -125mmHg • Canister 60cc capacity • Disposable • Hand-powered NPWT • Developed by MIT student • Field testing in Haiti 2/2010 • www.technologyreview.com/biomedicine/2483/7/?a=f

11. Is There a Best Device? • ECRI Institute Evidence-Based Practice Center performed a review of NPWT devices. • Commissioned by AHRQ • Systematic reviews of literature performed. • 487 page Technology Assessment Report published 2009 (www.ahrq.org).

12. Report Findings… • ALLsystematic reviews - dearth of high quality clinical evidence supporting the advantage of NPWT compared to other wound treatments. • Many systematic reviewers relied on low quality retrospective studies to judge NPWT efficacy. • No studies comparing different components (e.g. gauze vs. foam) were identified. • Benefits of NPWT for one wound type cannot be assumed for all wound types.

13. NPWT - Indications • Acute wounds • Surgical wounds • Including surgical wounds with dehiscence • Partial & full thickness burns • Neuropathic ulcers • Venous or arterial ulcers unresponsive to standard therapy • Traumatic wounds • Post-flap or meshed graft wounds • Stage III & Stage IV pressure ulcers

14. NPWT - Contraindications • Necrotic tissue with eschar • Malignant/neoplastic disease present in wound margins • Untreated osteomyelitis • Fistula of unknown source • Direct application over exposed blood vessels or organs

15. NPWT – Patient Selection • Optimized nutrition • Optimization of co-morbid conditions • Oversight of immunosuppressants • Oversight of anticoagulants • Offloading • If pressure is a contributing factor • Special Populations • Pediatrics • Combat Wounds

16. NPWT - Complications • Bleeding • In all 6 deaths reported to FDA* • In 17/77 injuries reported to FDA* • Overgrowth of granulation tissue into foam • Foam retention in 32/83 reports to FDA* • Gossypiboma (retained foreign body) • Pain (usually dissipates after 20 minutes) • Enteric fistula if foam placed over compromised intestine • ? Stomal muco-cutaneous separation *FDA Advice for Patients: Serious Complications with NPWT (Alert released 11/13/09 re:death & injury reports associated with NPWT over 2 years (www.fda.gov)

17. NWT: How Does it Work? • Five mechanisms of action (MOAs) contribute to wound healing. • Negative pressure gradient is part of all NPWT MOA • NPWT creates high negative pressure from pump & through tubing. • Negative pressure decreases as transmitted through contact material & wound tissue. • Area of lower negative pressure is created in peripheral tissue. • Resulting negative pressure gradient causes fluid to move from low to high negative pressure areas.

18. NPWT – 5 MOAs • 1- Removal of wound fluid & desiccated tissue • decreased wound edema & congestion • improved wound environment • 2 - Removal of bacteria • decreased risk of colonization & infection • 3 - Improvement in blood flow • increased delivery of oxygen & nutrients • 4 - Promotion of granulation tissue formation • increased connective tissue deposition • 5 - Physical stimulation of cells • increased cell proliferation & migration

19. Mechanisms of Action (MOA) • Some MOAs are interlinked • It is not yet known which MOAs are most important in terms of wound healing • Much known about individual MOAs Slide courtesy of Smith & Nephew

20. NPWT Contact Material • Differentmaterials used to transmit negative pressure evenly across the wound bed • Researchers & clinicians have questioned if contact material is relevant to MOA • Recent research available • Borgquist, Gustafsson, Ingemansson & Malmsjo (2010) • Gauze & foam equally effective in porcine subjects • Dorafshar, Franczyk, Lohman & Gottlieb (2009) • Gauze at least as effective as foam in human subjects

21. MOA 1 – Removal of Fluid • Removal of edema/excess wound fluid • Edema caused by increased capillary permeability (normal response to wounding) • Edema widens gap between capillaries & wound cells • Impacts oxygenation & nourishment of wound • Removal of desiccated tissue • NPWT will remove some sloughy tissue • Decreases bacterial proliferation • Enhances opportunity for granulation • NPWT will NOT remove eschar • Removal of pro-inflammatory mediators • In acute wounds, cytokines mediate wound healing cascade • In chronic wounds, cytokines are not “switched off” • Results in chronic inflammatory state Slide courtesy of Smith & Nephew

22. Overview of Effect of Fluid Removal Excess wound fluid is removed by NPWT Edema is reduced Desiccated tissue is removed Wound congestion is decreased Pro-inflammatory mediators are reduced Oxygen and nutrient delivery are improved Slide courtesy of Smith & Nephew Tissue repair is stimulated

23. MOA 2 – Removal of Bacteria • If bacteria overwhelm a wound healing is delayed or prevented • Contributing factors include: • The depth of bacteria • The type and mixture of organisms • Underlying disease • The quality and level of tissue perfusion • The patient’s immune status • Signs of critical colonization or infection include: • Pain, redness, heat, swelling, discolored wound tissue, fragile granulation tissue, pocketing, bridging, abnormal odor, static wound margins Slide courtesy of Smith & Nephew

24. NPWT Bacteria Removal Mechanisms • Physical removal of bacteria • Negative pressure gradient moves bacteria out of the wound • Improved blood supply • NPWT improves wound perfusion • More phagocytes delivered into the wound • Reducing edema • NPWT reduces wound edema • Bacteria more accessible to WBCs • Sealed system • Prevents new bacteria from entering the wound Increased perfusion & less edema helps white cells to reach bacteria Slide courtesy of Smith & Nephew

25. Research on NPWT & Bacteria • Initial study on experimental wounds • Significant bacterial removal with NPWT • Mixed results in subsequent studies • Studies suggest a positive bacterial effect with NPWT • Recent study (Boone, 2010) • No significant difference in bacterial levels with foam or silver foam compared to moist gauze w/o NPWT • despite improvement in wound bed appearance Increased perfusion and less edema helps white cells to reach bacteria Slide courtesy of Smith & Nephew

26. MOA 3 – Enhanced Blood Flow • Adequate wound perfusion essential for tissue repair • Blood supply required for delivery of cells, factors and elements • Platelets • Neutrophils • Monocytes • Nutrients • Oxygen • Peripheral blood supply essential for wound healing processes Healthy microvascular blood flow Slide courtesy of Smith & Nephew

27. Effect of NPWT on Blood Flow • NPWT improves blood flow by three mechanisms • NPWT reduces edema • Reduces gap between capillaries & cells • Improves blood flow to cells • NPWT physically increases blood flow • Interstitial pressure falls below capillary pressure – capillaries reopen – blood flow restored • Lower pressures & intermittent pressures reduced periwound hypoperfusion (Wackenfors) in porcine subjects • NPWT stimulates endothelial proliferation & angiogenesis NPWT will stimulate blood flow A secondary intention wound with a healthy local blood supply Slide courtesy of Smith & Nephew

28. Effects of Blood Flow on Wound Healing • Help a wound fight infection • By delivering phagocytes to the wound • Neutrophils: the first phagocytes at the wound site • Monocytes: activated to become macrophages • Delivers nutrients & oxygen for healing Oxygen, nutrients and other essential cells are delivered via the blood supply Wounds need oxygen and nutrients to heal successfully Slide courtesy of Smith & Nephew

29. MOA 4 - Granulation Tissue Formation • Granulation tissue • Formed through fibroplasia and angiogenesis – resulting in: • Collagen rich connective tissue • New vascular structure • Extracellular matrix (ECM) cells • Prevented in chronic wounds by: • Up-regulated pro-inflammatory cytokines, down-regulated TIMPs • Inflammatory cells (eg: neutrophils) • Bacteria and proteases • Increased collagen breakdown • Decreased collagen deposition • Poor tissue perfusion A histology picture of granulation tissue showing macrophages, fibroblasts, and collagen Slide courtesy of Smith & Nephew

30. Granulation Tissue • Formation essential for successful wound healing • Fundamental component of proliferative repair • A wound unable to produce granulation tissue will not heal • Scar tissue filling wound space • Comprised of: • Collagen rich extracellular matrix • New vascular structure (angiogenesis) Slide courtesy of Smith & Nephew A secondary intention wound filling with granulation tissue

31. NPWT and Production of Granulation Tissue • Granulation tissue formation is consistently reported in wounds managed with NPWT • The rate of granulation tissue formation under NPWT is considerably higher than the rate for wounds treated with growth factors • Granulation tissue is generated during NPWT by: • Transmission of a uniformly applied (negative) force to the wound tissue • The recruitment of new tissue via viscoelastic flow • Mechanical stress leading to increased cellular proliferation and angiogenesis Slide courtesy of Smith & Nephew

32. MOA 5 - Cell Stimulation Cell mitosis from mechanical stimulation • Cell stimulation – effect of mechanical force on cells • Applied forces deform extracellular matrix • Cells within stretched tissues also deformed • Tissue & cell deformation causes stimulation of growth factor pathways • End result = increased cell mitosis & production of new tissue Slide courtesy of Smith & Nephew

33. Cells Affected by Cell Stimulation • Fibroblasts • Found in dermis • Produce collagen, elastin, ground substance & fibronectin • Endothelial cells • Form new vessels • Provide endothelial lining for cardiovascular system • Keratinocytes • Major cell type in the epidermis (making up about 90% of epidermal cells) • Fundamental to production of new epidermis Slide courtesy of Smith & Nephew

34. NPWT and Cell Stimulation • Stimulation of cell mitosis by force is one therapeutic effect of NPWT • Experiments using NPWT have demonstrated links to mechanical cell stimulatory effects • Researchers examined effect of NPWT/tissue deformation in cadaver wounds (Morykwas, 2006) • Measured tissue deformation (strain) • Radio-opaque markers placed in tissue and radiographs taken with & without the application of NPWT • Tissue strain under NPWT was 18% at wound/dressing interface & 5% when measuredat an 8cm margin from wound edge • A further study demonstrated an increase in fibroblast cell mitosis-related activity at a 5% strain Slide courtesy of Smith & Nephew

35. Cell Stimulation and Intermittent NPWT • Cell stimulation may be linked to success of intermittent NPWT • Research has shown: • Mitosis is further increased when mechanical cell stimulation (strain) is applied in a cyclic fashion • Cyclic strain stimulates proteins related to keratinocyte growth and differentiation (Takei,1997) • Cyclic mechanical stretching increased proliferation of human fibroblasts & production of collagen type I (Yang, 2004) • 4 - fold increase in epidermal cell proliferation in 8 hours when cyclic tension applied (Pietramaggiori, 2007) Slide courtesy of Smith & Nephew

36. Mechanism of Action Questions Yet to Be Answered • To what degree does intermittent NPWT affect outcomes? • If cyclic pressure is an important factor in NPWT – what is most effective cycle? • Are interface materials (dressings) relevant to NPWT MOA? • How does use of contact layer affect cell stimulation & tissue strain? • Porcine - Contact layers can decrease in - growth of granulation tissue into wound filler (foam or gauze) (Malmsjo, 2010) • Porcine - The degrees of micro- & macro-deformation are similar…regardless if foam or gauze is used as a wound filler.” (Borquist, 2010) • “In vitro – Fibroblasts did not migrate into KerlixAMD… significant tendency to grow into Granufoam.” (Wiegand, 2010) • Is there a definitive answer about the antimicrobial function of NPWT? • Which MOA are most important?

37. Special Populations: Pediatrics • Limited clinical data to guide evidence-based practice. • NPWT has not been evaluated formally in pediatric clinical trials. • >20 articles (case series/reports) re: use of NPWT in peds published. • Although determining exact cause difficult, fistula formation has been reported. • Outcomes suggest faster wound closure with NPWT than “traditional” methods.

38. Pediatric Recommendations • Lower pressure settings (with foam) • -50 to -75mmHg for children <2 years old • -125mmHg for adolescents • Monitor closely for fluid loss • Especially in neonates

39. Special Populations: Combat Wounds • NPWT being used in field hospitals • NPWT provides efficient management of extensive traumatic wounds • NPWT promotes accelerated healing

42. NPWT - Tips and Techniques • Protect peri-wound skin to prevent maceration. • If large wound surface area, consider additional trak pads or drains. • DO NOT overpack/overfill wound. Provide space for wound to “collapse” around dressing. • Consider adjunctive dressings to wound base.

43. Adjunctive Dressings • AMD gauze (Covidien) • Hydrofera Blue (Healthpiont) • Restore Triact Silver (Hollister) • Silverlon (Argentum) • Sorbact (Cutimed) • Tegaderm Ag Mesh (3M) • Xeroflo (Covidien)

44. NPWT Tips and Techniques • For wounds in sacral/gluteal area, do not attempt intermittent setting because dressing will fail. • Consider alternating pressure • variable pressure therapy (VPT® - Prospera) • ITI • For wounds on foot consider higher pressures with foam-based NPWT to prevent maceration. • White foam requires higher pressures than black foam.

45. NPWT - Tips and Techniques • For wounds in gluteal/sacral area or other areas of challenging anatomy, use ostomy paste to promote seal of transparent drape. • For wounds with exposed vessels or intestine, protect with overlay of petrolatum gauze. • Do not leave foam dressing without suction in place >2 hours.

46. NPWT Tips and Techniques • Younger, healthier patients will granulate more rapidly than older, sicker patients. • Consider non-adherent dressing beneath black foam. • May reduce pain but may also influence in-growth of granulation tissue (Wiegand, 2010) • For patients with thick exudate, consider Wooding-Scott or lavacuator drain & gauze-based NPWT. • For patients with significant tunneling, consider channel drain & gauze-based NPWT.

47. NPWT Tips and Techniques • For wounds with significant undermining, consider protecting intact periwound skin over undermining with transparent drape and applying black foam over undermined area (the “Rick Trick”).

48. NPWT Tips & Techniques • For wounds with dead space • We add collagen dressings to wound base prior to NPWT application. • We re-approximate wound edges & secure with closure strips, then apply NPWT over top of wound.

49. Negative Pressure Wound Therapy (NPWT): Principles, Tips & Techniques Thank You!! Constant attention by a good nurse may be just as important as a major operation by a surgeon.  ~Dag Hammarskjold