hyperbaric oxygen therapy

Hyperbaric Oxygen Therapy

INTRODUCTION• Hyperbaric oxygen therapy is defined as

administration of 100% oxygen to a patient placed inside a chamber pressurized to greater than 1 atmosphere.

Not Hyperbaric Therapy!!!

• Local application of pressurized oxygen to a part of the body without completely enclosing the patient is not hyper baric oxygen therapy

History

• Initial discovery– 1662 Henshaw built first hyperbaric chamber

• English physician and clergyman Called the chamber the “Domicilum”

Background

• Elemental Oxygen– 1775 Discovered by Priestly (English)

• Surgical use– 1870’s Fontaine & Bert (France)

• Prolong anesthesia• Improved surgical outcomes

– Wound healing

• Decompression sickness– 1910-30’s Drager, then Behnke & Shaw

• Reduced morbidity of decompression• Studies of cardiopulmonary effects initiated

Physiology

• Cardiopulmonary– Increase in PaO2

• Saturation of available hemoglobin molecules– Hb 97% saturated at atmospheric pressure– Maximization does NOT significantly increase O2 delivery

• Increase in dissolved O2– PAO2 is 100mm Hg at atmospheric pressure– Using 100% FiO2 at 3 atm up to 2000mm Hg

» Increase O2 from 3ml/L blood to to 60ml/L» 20 times more O2 circulating in plasma

Mechanisms of Action

Increased Oxygen Tension Vasoconstriction Increased Fibroblast Replication Increased Collagen Response Angiogenesis Enhanced Leukocyte Function Attenuation of Reperfusion Injury

Mechanism of Action

• Three main effects of HBO2:1) Delivery of O2 to hypoperfused tissues

• Limit ischemic damage, cell death, and inflammation• Promotes collagen synthesis and angiogenesis• Decreases lactate production and tissue acidosis

2) Generation of oxygen free radicals• Aids in oxygen-dependent killing of bacteria• Facilitates oxygen dependent transport of antibiotics

3) Vasoconstriction• Limits leukocyte adhesion and degrannulation• Decreases tissue edema

Dosing and Delivery

• Parameters– All regimens use

100% O2 – Pressure more

variable• Most use 2.4 atm• Maximum

tolerated is 3 atm• 4 atm induces

seizuresMonoplace Hyperbaric Chamber.

Dosing and Delivery

Dosing and Delivery

• Common regimens– Dives between 30 and

120 minutes• May be daily or BID• Total number varies by

indication– Most treatments

around 30 dives– Optional addition of 10

or more dives

– Monoplace & Multiplace chambers

Multiplace Hyperbaric Chamber.

Advantages of a Monoplace Chamber

1. Patients are cared for individually thereby maintaining patient privacy.2. Isolation of patients insures that there is no amplification or spread of disease or infection from other patients.3. Patient can enjoy a more comfortable and relaxing treatment. 4. Multiplace chambers require an awkward and restraining facemask, Monoplace Chambers do not.6. Technicians can easily monitor patients.7. Ideal for patients confined to bed in acute stages of illness or injury.

INDICATIONSInvestigational

AutismAuto-immune DisordersCancer TreatmentCerebral PalsyChemical ToxicityChronic Fatigue SyndromeCrohn’s DiseaseFibromyalgiaHeadache SyndromesLyme DiseaseMacular DegenerationPre And Post Surgical Healing (Cosmetic Surgery)Multiple SclerosisNear Drowning Respiratory distress syndromeSeizure DisorderSpinal Cord InjurySports InjuriesStem Cell Recovery TreatmentStrokeTinnitusTraumatic Brain Injury•  

Applications

Today’s review1. Osteoradionecrosis2. Enhancement of graft & flap viability3. Malignant otitis externa4. Sudden SNHL5. Radiation sensitization

Osteoradionecrosis

• Pathophysiology– Reduction in caliber & number of feeding vessels– Periosteal & mucosal damage bone necrosis– Body of the mandible most affected

ORN Histology – Mandible

ORN X-ray – Mandible

Chronic Non-healing Wounds

• Generalising from other fields– Diabetic foot ulcers

• Significant reduction in morbidity• Significant improvement in functional outcomes• Significant cost savings

Clinical Uses and Therapeutic Effects of Hyperbaric Oxygen

– Rationale for Hyperbaric Oxygen in Problem Wounds:• Enhances fibroblast replication• collagen synthesis• neovascularization• leukocyte bacteriocidal activity

Skin Grafts & Free Flaps

• Pathophysiology– Grafted or transplanted tissue may be healthy– But… implantation site may be hypoxic

• Due to vasospasm, edema, infection• Oxygen & nutrient supply compromised• Must establish vascular connection for survival

• HBOT:– Improves tissue PO2– Promotes angiogenesis– Augments immune response & limits inflammation

(oedema)

Indication of HBO

Compromised Grafts And Flaps• Initial treatments should be twice daily• Once it is more viable and stable then

daily treatment• 2-2.5 ATM 90-120 minutes

Malignant Otitis Externa

• Improved efficacy of immune response

• Enhancement of bacteriacidal antibiotic effects

Need RCTs to further evaluate this indication

Radiation Sensitization

• Among first studied uses of HBO2 (1960’s)– Areas of hypoxia in tumors are resistant to therapy– Increasing oxygen pressure in the tumor can aid

tumoricidal therapies• Administration of radiation sensitizing agents (oxygen donors)

Radiation Sensitization

• Systematic review (Bennett, et al. 2008)– Found 19 randomized trials of HBO2 with XRT

• H&N, cervix, bladder, rectum, esophagus, brain

– H&N • Significant mortality reduction • Significant decrease in recurrence

HBOT in Sudden Sensorineural Hearing Loss (SSNHL)

• Idiopathic sudden sensorineural hearing loss(ISSNHL) is an otologic emergency with anincidence of about 5–20 per 100,000population per year

• It is a sudden, usually unilateral and greater than 30 dB hearing loss (HL) over at least 3 contiguous frequencies, occurring over a period of 72 hr

Management

• Controversial: The use of more than one agent in treatment is exceedingly common• Choice of agents used varies substantially

among clinicians

SSNHL

• A Cochrane Review (first published in The Cochrane Library in Issue 1, 2005 and previously updated in 2007)

•Comparing the effect on ISSHL and tinnitus of HBOT and alternative therapies

Selection criteria

• Randomized controlled trials that compared the effect of treatment for either acute or chronic idiopathic sensorineural hearing loss and/or tinnitus where hyperbaric oxygen administration is included

• FolLwing trials were included in the review– Cavallazzi 1996– Fattori 2001– Hoffmann 1995a; Hoffmann 1995b;– Pilgramm 1985– Schwab 1998– Topuz 2004

R E S U L T S

• 1. Acute ISSHL: pure tone audiometricchange in hearing

• There was a 22% greater chance ofimprovement with HBOT

• There was a statistically significantimprovement in those with severe hearing loss and moderate hearing loss

2. Chronic ISSHL: • Difference was not statistically significant• There were no significant improvements in

hearing reported for chronic presentation (6

months) of ISSHL

3. Acute tinnitus: • The significance of any improvement in

tinnitus could not be assessed4. Chronic tinnitus: relief of tinnitus• The difference was not statistically significant

Adverse events

– No trials reported any data on adverse events in a systematic way– 3 participants suffered middle ear barotrauma(Pilgramm 1985)

Barotrauma

Barotrauma

• Barotrauma refers to injury sustained from failure to equalize the pressure of an air-containing space with that of the surrounding environment

• Affects several different areas of the body, including the ear, face and lungs.

Introduction

• Diving• Aviators (after rapid ascent to altitude)• Astronauts• Rarely HBOT

Symptoms

• Symptoms of barotrauma include ear pain, hearing loss, dizziness, tinnitus and hemorrhage from the ear.

Differential diagnosis of decompressionillness

• Middle-ear or maxillary sinus overinflation• Gas expansion during ascent and an

obstructed eustachian tube or sinus ostium• Contaminated diving gas and oxygen toxic

effects

Treatment

• Recompression is usually advised even if manifestations resolve with first aid

(Since untreated decompression sickness can recur days after the initial onset)

• Complete relief of symptoms in 50-98% of individuals

Outcome

• Depending on the severity of illness• Period of time that has elapsed between

development of DCI and recompression

Contraindications

• One absolute contraindication– Pneumothorax

• Pressure converts to tension pneumothorax

– All patients get screening CXR• Relative contraindications

– History of spontaneous pneumothorax

– History of throacic surgery– Concurrent URI– Emphysema and COPD– Seizure disorders

Complications

• Barotrauma– Lung parenchyma

• Elevated pressures may damage alveoli

– Alveolar hemorrhage– Hemoptysis– Pneumonitis

– Alveolar rupture• Pneumothorax• Pulmonary interstitial

emphysema

Pneumothorax

Complications..

• Lens deformation causes temporary myopia• Exacerbation of other processes

– Dental abscess, sinusitis, laryngocele, etc.• Claustrophobia, anxiety, etc.• Oxygen toxicity

– Very rare, but may cause seizures• Potential effects on tumor growth

– Controversial

Fire Risk

• Especially monoplace– 100% oxygen– Highly pressurized– Enclosed space

• Rare… but not rare enough– 50 deaths due to HBO2-related fires since 1980– Must remove all flammable materials– Fire safety protocol is essential

• Risk reduced in multiplace chambers– Chamber pressurized– O2 delivered individually via tight-fitting masks– Attendants may enter in an emergency

Contraindications

• Absolute Contraindications– Untreated Pneumothorax– Bleomycin –cardiotoxicity– Cisplatin- delayed wound healing– Disulfiram- blocks superoxide dimutase (SOD)

Absolute HBO Contraindications

Recent Bleomycin Use – recent is not established although a one year period may be sufficient.

Current Doxorubicin (Adriamycin) – wait 2-3 days prior to starting HBO.

Undersea and Hyperbaric Medicine board Review Course for PhysiciansPenn Medicine. August 2010.

Absolute HBO Contraindications

Disulfiram (Antabuse) – blocks superoxide dismutase which decreases the body’s ability to neutralize oxygen free radicals; inhibits hyperoxic induction of cytochrome P450. Potential for pulmonary toxicity.

Contraindications

Relative Contraindications• URI• COPD with bullous emphysema or CO2 retention• Claustrophobia• Seizures• Ear or sinus surgery or recent thoracic surgery• Optic neuritis• Pacemakers (verify for pressure tolerance)• Pregnancy• Congenital Spherocytosis

Costs

• HBO2 is relatively expensive…– Monoplace chamber < Multiplace chambers– Most facilities have multiplace chamberss, etc.– But…

• Medicare reimburses for most accepted indications

Summary

• HBO2 derives its clinical benefit via– Increase in the oxygen delivery to hypoxic tissue– Promoting native mechanisms of healing – Decreasing tissue edema & reperfusion injury

• Dosing– Most commonly 30-40 dives of 90 min at 2.4atm but

less than 3 atm• Costs

– Significant, yet analyses support cost savings in proven indications

Summary

• Supported ORL-HNS indications– ORN & CRN, radiation soft tissue injury– Flap & graft survival

• Unsupported ORL-HNS indications– Sudden SNHL, tinnitus, Bell’s palsy

• Areas of uncertainty– Likely effect: MOE & skull base osteo, fistulas– Poor side effect profile: radiation sensitization

Summary

• Further research– Molecular mechanism incompletely understood

• Animal studies• Human tissue studies

– Need ethical randomized control trials• Variety of indications

– More combination regimens for cancer treatment & post-XRT reconstruction salvage

• What are the optimal dose & delivery shemes?