Hyperbaric Oxygen Therapy and Negative Pressure Wound Therapy

Question 1

What is hyperbaric oxygen (HBO) therapy?

Answer 1

Oxygen under pressure

Use in clinical medicine came about in 1955
- Increased oxygen environments to augment the effects of radiation therapy treatments in cancer patients

Tremendous growth since 1960s, but problems and criticism over utilization and regulatory issues

Question 2

What did the “Report of the committee on hyperbaric oxygenation” (published in 1977) state?

Answer 2

Divided disorders treated by HBO into 4 categories:

• Category 1 : disorders for which there was no question of HBO efficacy
• Category 2 : disorders for which there is no supporting evidence whatsoever

This report has been updated periodically

Currently contains 14 disorders presently approved for HBO therapy

Question 3

What are the approved conditions outlined by the Undersea and Hyperbaric Medical Society (UHMC) for HBO?

Answer 3

Air or gas embolism

CO poisoning

Gas gangrene

Crush injury, compartment syndrome, and other acute traumatic ischemias

Decompression sickness

Arterial insufficiencies

Severe anemia

Intracranial abscess

Decrotizing soft tissue infections

Osteomyelitis (refractory)

Delayed radiation injury (soft tissue and bony necrosis)

Comprised grafts and flaps

Acute thermal burn injuries

Idiopathic sudden sensorineural hearing loss

Question 4

What are the general principles of hyperbaric oxygenation?

Answer 4

When inside the chamber, the patient breathes 100% oxygen intermittently at a pressure higher than at sea level

The literature supports the type of HBO therapy in which a patient is:

• In a chamber
• Breathing elevated partial pressures of oxygen
• Through an intact cardiopulmonary system

Topical high-pressure oxygen and containers enclosing individual limbs are not considered HBO therapy
- No data to support use

Question 5

What is some of the equipment used for HBO?

Answer 5

Monoplace chamber
- Treat one person at a time

Multiplace chamber
- Able to treat as many as 20 or more patients simultaneously

Question 6

What are the characteristics of a HBO Monoplace chamber?

Answer 6

Free cylindrical unit

Steel end caps

Thick, cylindrical acrylic hull

Possible to administer IV fluids, monitor BP, even mechanically ventilate an intubated patient

Question 7

What are the characteristics of a HBO Multiplace chamber?

Answer 7

Patients typically seated in special seats along the wall

Due to volume, these chambers are compressed with medical-grade air instead of oxygen

100 percent of oxygen is administered through an air mask or a hood

Question 8

What are the physiologic effects of HBO?

Answer 8

Mechanical effects of reducing bubble size

• Occurring in decompression sickness or air emboli
• Effects on gas bubble size
• Increased dissolved oxygen in plasma

Effects of an increased partial pressure of oxygen
- Varies by organ system and disorder being treated

At higher atmospheric pressure, oxygen develops pharmacologic properties
- Must be dosed appropriately to avoid complications

Question 9

What are the effects due to elevated partial pressures of oxygen?

Answer 9

The clinical administration of HBO is limited to a max pressure of 3 ATA (atmospheres absolute)
- Greater than 3 ATAs increased the toxic effects of oxygen

Question 10

What are the effects of HBO on blood flow to the tissues?

Answer 10

VASOCONSTRICTING, BUT…

Compensating for by the increased oxygen dissolved in the plasma tissues

Good for hypoxic wounds

• Forms new microcirulation
• Angiogenesis is accelerated by hyperoxygenation
• Shortens healing time

Question 11

What are the effects of HBO on Gas Gangrene?

Answer 11

Rapidly progressive and life-threatening bacterial disorder

Caused by the anaerobic bacteria CLOSTRIDIUM PERFINGENS

HBO inhibits the alpha-toxin produced by the bacterium

Direct bacterial killing effect

Question 12

How does HBO improve viability of skin flaps?

Answer 12

Increased production of an antioxidant in the HBO environment that has measured in increased quantities in preserved tissue flaps

Improved microvascular perfusion in ischemic rat skin flaps

Question 13

What is the physiological impact of oxygen in wound healing?

Answer 13

Collagen deposition

• Increase in partial pressure of oxygen
• Accelerates fibroblast replication–increased collagen synthesis
• Leads to granulation, neovascularization, and epithelialization

Immune response
- Increased cellular oxygen levels increases leukocyte bacterial killing and gram negative organisms

Mediation of cytokine activity

Angiogenesis in irradiated tissues

Question 14

HBO can be applied in what select wound types?

Answer 14

LE diabetic wounds

Arterial insufficiency ulcers

Delayed radiation injury

Clostridial gas gangrene

Chronic refractory osteomyelitis

Compromised skin grafts and flaps

Thermal burn injuries

Question 15

What are adverse effects of HBO by system?

Answer 15

CNS
- Visual changes, tinnitus, nausea, twitching, irritability, dizziness, seizure

Pulmonary
- Coughing, SOB, bronchial irritation

Ocular
- Retinal damage in premature infants, myopia (nearsidedness), nuclear cataracts

Question 16

What are the relative contraindications of HBO?

Answer 16

Emphysema

History of spontaneous pneumothorax

High fever

Optic neuritis

Active respiratory and sinusitis

History of ear surgery

Seizure disorders

CHF

Uncontrolled HTN

Pregnancy

Question 17

What are the absolute contraindications for HBO?

Answer 17

Untreated pneumothorax

Concomitant treatment with Doxorubicin
- Chemotherapy drug

Concomitant or recent treatment with Bleomycin
- Cancer medication

Question 18

What are the benefits of Negative Pressure Wound Therapy (NPWT)?

Answer 18

Promotion of moist wound healing

Reduction of edema and interstitial fluid

Increased local perfusion

Approximation of wound edges

Stimulation of granulation tissue formation

Reduction of bacterial load

Reduction in the frequency of dressing changes

Question 19

What is the theory behind NPWT?

Answer 19

Removal of fluid

• Interstitial edema is reduced
• Inflammatory mediators and bacteria removed

Mechanical stimulation of cells
- Encourages cell proliferation, granulation tissue formation, and wound contraction

Occlusion of the wound from environmental contaminants

Question 20

What are the effects of NPWT at the tissue level?

Answer 20

Occlusion

• Airtight seal to maintain moist healing environment
• Dressing is changed every 48-72 hours–exposure to air is reduced

Cellular deformation (Suction force = stretching force on cells)

• Increases release of growth factors and cytokines associated with cell proliferation
• Increased cellular division and migration of macrophages, lymphocytes, and fibroblasts
• Increased angiogenesis and granulation tissue formation

Fluid removal

• Removal of edema facilitates oxygen and nutrient diffusion
• Proliferation of lymph vessels
• Opening of collapsed lymph vessels in CVI wounds

Circulation

Wound contractions

Bioburden

Question 21

What are the indications for NPWT?

Answer 21

ACUTE SURGICAL WOUNDS:

• Grafts and flaps
• Fasciotomies
• Open abdominal wounds
• Full thickness wounds with and without exposed structures
• Deep partial and full-thickness burns
• Traumatic amputations
• Over skin substitutes

CHRONIC WOUNDS

• Debrided neuropathic wounds
• Open amputation sites related to diabetes
• Stage 3 and 4 pressure injuries
• Venous and arterial insufficiency ulcers

Question 22

What are the precautions of NPWT?

Answer 22

Anticoagulants

Low platelet count

Over bone, tendon, organs, vessels

Rate and type of drainage collection

Monitor skin condition when dressing placed over bony prominences

Question 23

What are the contraindications of NPWT?

Answer 23

Wounds with 30 percent necrotic tissue

Unrelated osteomyelitis

Lack of hemostasis

Directly over exposed vessels, bypass grafts, organs, etc.

Ischemic wounds with proximal occlusion

Question 24

What are the components of NPWT?

Answer 24

Suction device

Wound filler

Occlusive sheet cover

Tubing

Collection canister

Question 25

What is the continuous mode of suction delivery?

Answer 25

Advantages:
- Continuous fluid collection with heavily exuding wounds, single compression cycle–decreases pain, provides stability to the wound (may allow for increased mobility of patient)

Disadvantage:
- Slower granulation formation compared to intermittent therapy

Question 26

What is the intermittent mode of suction delivery?

Answer 26

Advantages:
- Cyclic compression good for wounds with decreased circulation, increased mechanical stimulation–increased rate of granulation

Disadvantages:
- Airtight sheet can loosen, more prone to leaks due to increase pooling of heavily exuding wounds, potential for pain, may disrupt sleep

Question 27

What is the variable mode of suction delivery?

Answer 27

Advantages:

- Benefits of intermittent, but maintenance of low pressure continuous

Question 28

What is the instillation mode of suction delivery?

Answer 28

Advantages:
- Allows automatic periodic topical irrigation of wound tissues with normal saline or antibacterial solutions, may lead to increased granulation due to frequent irrigation and removal of fluids

Disadvantages:
- May cause maceration and loosening of the occlusive sheet as a result of the extra fluid pumped into the foam

Question 29

What are the different kinds of wound fillers?

Answer 29

Black foam

• Promotes granulation tissue formation and produces less dense and organized granulation tissue compared to gauze
• Decreased integrity = possibility of breaking off into the wound

White foam

• Less aggressive, less adherence in tunnels, tracts, or undermining
• Slower granulation compared to black foam

Antimicrobial gauze

• Produces thinner, denser, more organized granulation tissue but at a slower rate
• Gauze fibers can shed into the wound bed

Question 30

What are the basic steps to NPWT application?

Answer 30

Prep wound bed

Prep periwound skin

Apply non-adherent protective layer

Apply wound filler

Apply occlusive sheeting 3-5 cm past wound edge

Apply top mounted drain

Connect tubing to NPWT suction/canister

Turn on and ensure a good seal