Transcript Negative Pressure Wound Therapy (NPWT): Principles, Tips

Negative Pressure Wound Therapy (NPWT):
Principles, Tips & Techniques
Mary Arnold Long, MSN, RN, CRRN, CWOCN-AP, ACNS-BC
Mid East Region WOCN Conference 2010
• Disclosures
• Speakers Bureau Healthpoint Medical
• Consultant SpanAmerica
• Artwork/slide content have been provided by:
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ConvaTec
KCI
ITI
Premco
Prospera
Smith & Nephew
Spiracur
Joseph B. Warren, LTC AN, First Army Command
NPWT Definition
• The use of sub-atmospheric pressure to promote or assist
wound healing or to remove fluids from a site.
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
NPWT – TheTerminology
• Various terms are used for NPWT
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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
NPWT – The Devices
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
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:
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KCI Wound VAC (Granufoam TM; Versfoam TM)
Prodigy
Svedman Svamp
Smith & Nephew Renasys Foam
Medela (AvanceTM Green Foam)
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
Other NPWT
• Bio-dome Technology
• Engenex
• Canister-freeTechnology
• Kalypto
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/bio
medicine/2483/7/?a=f
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).
Report Findings…
• ALL systematic 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.
NPWT - Indications
• Acute wounds
• Surgical wounds
• Including surgical wounds with dehiscence
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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
NPWT - Contraindications
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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
NPWT – Patient Selection
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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
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*
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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)
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.
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
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increased delivery of oxygen & nutrients
• 4 - Promotion of granulation tissue formation
• increased connective tissue deposition
• 5 - Physical stimulation of cells
• increased cell proliferation & migration
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
NPWT Contact Material
• Different materials used to transmit
negative pressure evenly across the
wound bed
• Researchers & clinicians have
questioned if contact material is relevant
to MOA
• Recent research available
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Borgquist, Gustafsson, Ingemansson &
Malmsjo (2010)
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Gauze & foam equally effective in porcine subjects
Dorafshar, Franczyk, Lohman & Gottlieb
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Gauze at least as effective as foam in human
subjects
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
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
Tissue repair is stimulated
MOA 2 – Removal of Bacteria
• If bacteria overwhelm a wound healing is delayed or
prevented
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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
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
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
MOA 3 – Enhanced Blood Flow
• Adequate wound perfusion essential for tissue repair
• Blood supply required for delivery of cells, factors and
elements
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Platelets
Neutrophils
Monocytes
Nutrients
Oxygen
• Peripheral blood supply essential
for wound healing processes
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
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
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
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)
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
MOA 5 - Cell 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
Cell mitosis
from
mechanical
stimulation
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
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 measured at an 8cm margin from wound edge
• A further study demonstrated an increase in fibroblast cell mitosisrelated activity at a 5% strain
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)
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?
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.
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
Special Populations: Combat
Wounds
• NPWT being used in field hospitals
• NPWT provides efficient management of extensive
traumatic wounds
• NPWT promotes accelerated healing
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.
Adjunctive Dressings
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AMD gauze (Covidien)
Hydrofera Blue (Healthpiont)
Restore Triact Silver (Hollister)
Silverlon (Argentum)
Sorbact (Cutimed)
Tegaderm Ag Mesh (3M)
Xeroflo (Covidien)
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 foambased NPWT to prevent maceration.
• White foam requires higher pressures than black foam.
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.
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.
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”).
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.
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