Core Content Lecture

Steven Elsbecker D.O.University of Nevada School of MedicineJanuary 18th 2012

DISCLAIMER

45 year old male with toe pain secondary to gout presents to your ED. While establishing IV access, the nurse forgets to flush the IV tubing and the 10ft extension tubing that she decided to use forcing a large quantity of air into your patient’s vein. He quickly becomes short of breath with concurrent drop in O2 sats

Diagnosis?Treatment?

Hyperbaric Oxygen Therapy

Steven Elsbecker D.O. / Troy Aikman / DuffmanUniversity of Nevada School of MedicineJanuary 18th 2012

Objectives

Review our dive facility and proceduresPhysics of Hyperbaric Oxygen Therapy (HOT)Physiology of HOTIndicationsReview basic principles for using HOTDisadvantages / ComplicationsEvidence for use in EM

To get ONE resident to implement HOT ONE time in 2012

History of Hyperbarics

First hyperbaric chamber built in 1662 by British clergyman Nathaniel Henshaw

Compressed manually with a bellows using room air and did not reach pressures that had any clinical significance

Up until 1955, much of hyperbarics remained “of little clinical significance”

History of Hyperbarics

In 1967, the Undersea and Hyperbaric Medicine Society (UHMS) was founded to help facilitate the exchange of knowledge in the field

Eventually became the governing body for the application of HOT

The Dive Facility

Two types of chambersMonoplace

Just patient inside. Desired gas delivered to whole chamberMultiplace

Can treat multiple critical patients at once. Nurse typically inside. Desired gas mixture given to patients individually.

Our Dive Facility

Our Dives

Duration is variable depending on indication

Pressurized to 2.0 – 2.2 ATA

FiO2 between 21 – 100%

Nurse in chamber with patients

Plasma TV with cable in the tank

Our Dives

Average bill generated for a single dive = $2600

Average repayment from Medicare is $360

Average number of dives required for a chronic wound is 30

$78,000 for a diabetic foot ulcer

Just CUT IT OFF!!!

Physics is Fun!

A neutron walks into Frankie’s and says “how much for a Fink Bomb?” The bartender replies “for you, no charge.”Boyle’s Law

Charles’ Law

Henry’s Law

Ideal Gas Law

Boyle's Law

p1v1=p2v2

Useful when thinking about gas embolic phenomenon, DCS

Charles' Law

(p1v1)/T1=(p2v2) /T2

Used to explain temperature changes when compressing or decompressing patients.

Henry's Law

P=KhC

Higher concentrations of a gas dissolved in blood will yield a higher partial pressure.

Diffusion

Wound healing, DCS, CO poisoning

Physiologic changes during HOT The $$$ Slide

HyperoxygenationFibroblast proliferationDecreases gas bubble loadVasoconstrictionAngiogenesisEnhances leukocyte oxidative killingInhibition of Clostridial toxinsAntibiotic synergy

Hyperoxygenation

Hb saturation on room air 97-100%

Also have small amount of O2 dissolved in plasma

Human tissue at rest requires approximately 250ml/min of O2

At 3atms, plasma concentration of O2 rises from 0.5 – 1.0 ml/dl to 6 ml/dl

Fibroblast proliferation / Collagen Synthesis

Main physiologic force behind healing complex wounds

More “healing” cells

Larger matrix to rebuild upon

Hunt TK, {ai MP, et al. The effect of varying ambient oxygen tensions on wound metabolismand collagen synthesis. Surg Gynecol Obstet. Oct 1972; 135(4): 561-7

Angiogenesis

Poorly understood mechanism of action

Only ever studied in rats / mice

Important for complex wounds and compromised grafts.

Limited applicability to EM

Knighton DR, Silver IA, Hunt TK, Regulation of wound healing angiogenesis-effect of oxygen gradients and inspired oxygen concentrations. Surgery. Aug 1981; 90(2): 262-70

Decreases gas bubble load

Boyle’s Law

patmvatm = pHOTvHOT

As partial pressures in plasma increase, Boyles law states that the volume of undissolved gasses must decrease

Practice Board Question

Tina McProzac, a 35 yo pregnant female with known history of bipolar disorder and SI is brought in by EMS for AMS. She was found in her home after police were called by a neighbor for her odd behavior. The patient is unresponsive, but hemodynamically stable. Basic AMS labs drawn at UMC are WNL. The female medical student rotating at UMC then comments on the patients beautiful shade of red lipstick.At what CO-Hb level should you dive these patients?Are there other indications for diving them?

Vasoconstriction

Hyperoxemia leads to vasoconstriction

O2 delivery(ml/min) = O2 carry(ml/dl) x Flow (dl/min)

No change in net O2 delivery

Decreased edema

Nylander G, Lewis D, Nordstrom H, et al. Reduction of postischemic edema with hyperbaric oxygen. Plast Reconstr Surg. Oct 1985; 76 (4): 596-603

Enhances Leukocycte Oxidative Killing

Enhances SOD

Augments oxidative destruction of phagocytosed bacteria

Inhibits Clostridial Toxins

Slows progression of necrotizing fasciitis

Limited useConservative managementWaiting for surgeonAwaiting transfer for higher level of care

No studies to date on HOT in the setting of severe C. diff infection

Antibiotic Synergy

Generation of free radicals assists in bacterial killing

Very limited studies done on HOT in the setting of sepsis. Again, only rat models available. Showed good outcomes.

Hill GB: Hyperbaric oxygen exposures for intrahepatic abscesses produced in mice by non–spore-forming anaerobic bacteria. Antimicrob Agents Chemother 1976; 9:312-317.

Quiz

Who named the following gas law: p1v1=p2v2

Robert BoyleRoss BerkeleyJacques CharlesAmedeo Avogardo

Indications for HOTAcute CO poisoningDecompression SicknessGas EmbolismNecrotizing FasciitisAcute Traumatic Peripheral IschemiaCrush InjuriesAcute Peripheral Arterial InsufficiencyPreservation of Skin GraftsRefractory OsteomyelitisRadionecrosisCyanide PoisoningActinomycosisDiabetic Wounds of the Lower ExtremetiesAcute Thermal Burns

Which Ones Do We Actually Care About?

Acute CO PoisoningDecompression SicknessGas Embolus Crush Injury / Compartment SyndromeCentral Retinal Artery OcclusionAcute Thermal Burns

CO Poisoning

HOT not always indicatedTreatment indicated for CNS depression, severe acidosis, CO-Hb > 20% or >10% in pregnant femalesTime to displace CO from Hb with room air, 100% NRB, and HOT is 300 minutes, 90 minutes, and 32 minutes respectivelyHalts lipid peroxidation by restoring cytochrome function

Principle #1

Hyperbaric oxygen is used to DIFFUSE more O2 into plasma.Increases total oxygen dissolved in plasma from 0.5 – 1.0 ml/dl up to 6ml/dl

O2 Content = 1.34 (HgB) (% Saturation) + PO2 (.003)1.34 x 14 x 1.0 (18.76) + 760 x 3 x 0.003 (6.84)

Pigs

How many divers does it take to circumcise a blue whale?

Four Skin Divers

Decompression Sickness

As partial pressure of O2 and N2 decrease in plasma, N2 and O2 dissolved in the tissues diffuse back into the bloodstream

Severity depends on total amount of gas dissolved in tissue and rapidity of ascent

Why Hyperbarics staff and SCUBA dive masters have a limited number of allowable dives per day

Decompression Sickness

Breath Hold Divers?Snorkelers?Recirculating Tanks?SCUBA?

Decompression Sickness

Type I – musculoskeletal sxs, fatigueType II – CNS and cardiorespiratory depression, shockType III – any spinal deficit, usually irreversible

Sxs 2/2 to bubble formation in vasculature leading to micro infarcts.

BrubakkA, Neuman T. Bennett and Elliot’s Physiology and Medicine of Diving. 5th edition. Great Britain. Elseiver Science Limited; 2003;Chapter 10

Principle #2

Increasing the partial pressure of dissolved gasses in plasma will decrease the volume load of undissolved gasses.Balloon in a roomGas Emboli and DCS

Gas Embolism

Rare, but very little treatment optionsNursing errorIJ Central line not in TrendelenburgDCSPulmonary barotraumaVascular surgery

No absolute amount of gas needed. Dependent on patient comorbidities and rapidity of buildup

Gas Embolii

Crush / Compartment Syndrome

Both have a myriad of complications

Edema is controllable with HOT without compromise of O2 delivery

Decreases reperfusion injury

Flint: Cummings Otolaryngology: Head & Neck Surgery, 5th ed.; CHAPTER 79

Principle #3

Hyperoxemia causes vasoconstriction and decreases edema

Proven efficacy with compartment and crush

Many types of edema, possibility of future indications

Central Retinal Artery Occlusion

Sudden onset painless monocular visual lossTheory for HOT is that the small amount of blood still getting to the retina can be hyperoxigenatedNeeds to be initiated within first 8 hours for greatest efficacyVisual improvement with HOT 82% vs 30% w/o

Beiran I, Goldberg I, Adir Y, Tamir A, Shupak A, Miller B, et al. Early hyperbaric oxygen therapy for retinal artery occlusion. Eur J Opthamol. Oct-Dec 2001;11(4):345-50

Hertzog LM, Meyer GW, Carson S, et al. Central retinal artery occlusion treated with hyperbaric oxygen. J Hyperbaric Medicine. 1992;7:33-42

Acute Thermal Burns

HOT reduces inflammatory response, reduces edema, and is protective against severe superimposed infection.

2/2 to vasoconstrictive, improved wound healing, and bacteriostatic/bacteriocidal properties.

Hart GB, O’Reiley RR, Broussard ND, et al. Treatment of burns with hyperbaric oxygen. Surg Gynecol Obstet. Nov 1974; 139(5) 693-6

Niezgoda JA, Cianci P, Folden BW, et al. The effect of hyperbaric oxygen therapy on a burn wound model in human volunteers. Plast Reconstr Surg. May 1997; 99(6). 1620-5

Nitrogen Gradient

Concept useful in DCS, air embolism, PTX

The use of HOT or a NRB yields oxygen rich, nitrogen poor plasma.

The pockets of gas in the aformentioned scenarios are mostly comprised of notrogen.

Larger gradient leads to quicker reabsorption of gas pockets

Contraindications

AbsolutePNEUMOTHORAXDisulfiramChemotherapeutic Agents

RelativeAsthmaClaustrophobiaCOPDSpherocytosisHigh FeverPacemaker/ AICDPregnancy (no eveidence showing harm)

Complications

BarotraumaMiddle ear, Sinus, dental, and pulmonary

Cataract formationHyperthermiaDecreased seizure threshold

To Dive or not to Dive??

You are in a single coverage ER near the Pacific coast, you have a chamber, what will you do?

Asymptomatic healthy 23 yo male pulled from a house fire with no burns45 yo male returning from SCUBA trip with decreased CNS fxn and generalized weakness33 yo male with nec fasc and a surgeon who says “this doesn’t need surgery”55 yo female frequent flyer with chronic pain asking for “the one that starts with a D”24 yo male construction worker with radial and ulnar fxs who is complaining of increasing pain, parasthesias, and his hand feeling cold

Future Applications / Research Ideas

HACE / Altitude SicknessHAPE

Traumatic Cerebral Edema

HOT in severe sepsis

Human shrinking??!?

Summary

Very useful tool, but costly and limited indicationsP1 – O2 diffused in plasmaP2 – increased partial pressure of dissolved gasses yield smaller volumes of undissolved gassesP3 – hyperoxemia leads to decreased edemaBe aware that as you practice in different areas, the common reasons for using HOT may change depending on your surroundings

ReferencesBrubakkA, Neuman T. Bennett and Elliot’s Physiology and Medicine of Diving. 5th

edition. Great Britain. Elseiver Science Limited; 2003;Chapter 10Flint: Cummings Otolaryngology: Head & Neck Surgery, 5th ed.; CHAPTER 79Beiran I, Goldberg I, Adir Y, Tamir A, Shupak A, Miller B, et al. Early hyperbaric

oxygen therapy for retinal artery occlusion. Eur J Opthamol. Oct-Dec 2001;11(4):345-50

Hertzog LM, Meyer GW, Carson S, et al. Central retinal artery occlusion treated with hyperbaric oxygen. J Hyperbaric Medicine. 1992;7:33-42

Hart GB, O’Reiley RR, Broussard ND, et al. Treatment of burns with hyperbaric oxygen. Surg Gynecol Obstet. Nov 1974; 139(5) 693-6

Niezgoda JA, Cianci P, Folden BW, et al. The effect of hyperbaric oxygen therapy on a burn wound model in human volunteers. Plast Reconstr Surg. May 1997; 99(6). 1620-5

Latham E, Hare M, Neumeister, et al. Hyperbaric Oxygen Therapy. Emedicine specialties. May 2010.

Auerbach: Wilderness Medicine. 6th edition. Chapters 75,77,78.

??Questions??

Final Quiz

For a Bentley’s gift card…

What does SCUBA stand for?