Hyperbaric Medicine
Rosen’s Chapter 200
March 1, 2007
Michael Savino, PGY-2
Hyperbaric Oxygen Therapy
(HBO)
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Involves intermittently breathing pure oxygen at
greater than ambient pressure
Think of oxygen as a drug and the hyperbaric
chamber as a dosing device
Elevating tissue oxygen tension is the primary
effect
Hyperbaric Oxygen Therapy
(HBO)
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Primary therapy for:
Decompression sickness
 Air embolism
 Carbon monoxide poisoning
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Adjunct therapy for:
Surgical intervention
 Antibiotics
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Accepted Indications
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Air or gas embolism
Carbon monoxide poisoning
Clostridial myositis and myonecrosis
Crush injury, compartment syndrome, acute traumatic
ischemias
Decompression sickness
Enhance healing of wounds
Necrotizing fasciitis
Chronic osteomyelitis
Radiation necrosis, brown recluse spider bites
Thermal burns
History of Hyperbaric Therapy
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British physician, Henshaw, in 1662 used a
chamber fitted with a large pair of organ
bellows, so that air could either be compressed
into the chamber or extracted from it.
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In this ‘domicilium' increased pressures were used
for the treatment of acute disease, and reduced
pressures for the treatment of chronic diseases.
Oxygen discovered in 1775
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1889 – Moir used hyperbaric therapy to treat
workers building railroad tunnels underneath the
Hudson River. Reduced mortality rate of
decompression sickness from 25% to only 1.6%
per year.
1926 - Six-story “steel ball hospital” in
Cleveland, Ohio. The facility was capable of
treating patients in 72 rooms over 12 floors at
pressures of 3 atm absolute.
Basic Mechanisms
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Boyle’s Law – pressure and volume inversely
proportional under constant temperature
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By increasing ambient pressure to 2 atm, decreases the
volume by ½
Therapeutic for bubble forming diseases such as
decompression sickness or arterial gas embolism
Henry’s Law – at a given temperature, the amount of gas
dissolved in solute is directly proportional to the partial
pressure of the gas.
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By increasing ambient pressure, more oxygen can be
dissolved in the plasma
Mechanism of action
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Angiogenesis in ischemic tissues
Bacteriostatic/bactericidal actions
Carboxyhemoglobin dissociation hastened
Clostridium perfringens alpha toxin synthesis
inhibited
Vasoconstriction
Temporary inhibition of neutrophil Beta 2
integrin adhesion
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Monoplace (1 person) or multiplace (2-14
patients) chamber
Pressures applied inside the chamber are usually
2-3 x atm pressure, plus may have an additional
hydrostatic pressure equivalent of 1-2 atm.
Treatments last from 2-8 hours
Complications
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Middle ear barotrauma
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Middle ear barotrauma is the most common adverse effect of
HBO treatment
As ambient pressure within the chamber increases, patient
must be able to equalize the pressure in his/her middle ear
If not, pressure gradient develops across the tympanic
membrane. Pain followed by hemorrhage or serous effusion
develops
Prevention: teaching patient auto-insufflation technique or
use of decongestants
If auto-insufflation fails, tympanostomy tubes are placed.
Complications
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Pulmonary barotrauma
Rare
 Suspect if pulmonary or hemodynamic changes
occur during or shortly after decompression
 Place chest tube if pneumothorax develops
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Complications
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Oxygen Toxicity - Manifested by injuries to lungs, CNS,
and eyes:
Lungs –
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CNS toxicity –
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Can impair elasticity, vital capacity, and gas exchange. Rare.
But may occur when duration and pressures exceed normal
therapeutic protocols
Manifests as a grand mal seizure. (1-4/10,000 patients).
Risk is higher in hypercapnic, acidotic, or septic patients
Eyes –
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Progressive myopia has been reported in patients undergoing
repetitive daily therapy
Reversible within 6 weeks of discontinuing treatment
CLINICAL APPLICATIONS
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Arterial gas embolism occurs when vascular
wall is disrupted, as in:
Trauma
 Iatrogenic (surgical) – cardiovascular, Ob/gyn,
neurosurgical and orthopedic procedures, opening
of central venous catheters
 Iatrogenic (nonsurgical) - Pulmonary overexpansion
during mechanical ventilation
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Scuba Divers
Arterial gas embolism can occur due to pulmonary
expansion on decompression
 Decompression sickness (caisson disease or “the
bends”) is attributed to formation of nitrogen bubbles
in the body on decompression
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Also occurs in miners and astronauts
Emergency treatment of gas bubble
disorders
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ABC’s plus hyperbaric oxygen therapy
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Transfer to hyperbaric chamber ASAP
Gas bubbles may persist in tissues for days
Animal studies have shown efficacy of HBO therapy, but
randomized clinical trials on humans have not been done
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Mechanism of action of HBO in arterial gas
embolism and decompression sickness –
reduction of gas volume (Boyle’s Law), which
can reduce vascular compromise acutely
Hyperoxygenation hastens inert gas diffusion
and there is theoretical effect associated with
leukocyte adherence to vascular endothelium
damaged by bubbles
Carbon Monoxide Poisoning
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Carbon monoxide poisoning is the leading cause of
injury and death by poisoning in the world
Affinity of CO for hemoglobin (forming
carboxyhemoglobin) is 200 times that of oxygen.
Risk of developing neurologic sequelae including:
cognitive effects, memory loss, dementia, parkinsonism,
paralysis, chorea, cortical blindness, personality changes
and peripheral neuropathy.
Delayed sequelae occur 2-40 days after poisoning.
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Incidence of sequelae is 25-50% after severe poisoning
Carbon Monoxide Poisoning
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Supplemental oxygen is first line therapy
HBO causes carboxyhemoglobin dissociation to
occur faster than pure oxygen at sea level
pressure.
Animal studies show: improvement in
mitochondrial oxidative processes
 Inhibition of lipid peroxidation
 Impairment of leukocyte adhesion to injured vessels
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Clostridial Myonecrosis
(gas gangrene)
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Prompt recognition is important
Mortality rates of 11-52%
Most authors agree on the clinical benefit of HBO
treatment, but in retrospective studies, comparison
among patient groups, evaluation of efficacy based on
“tissue salvage” is difficult to obtain.
Diffused oxygen which raises capillary p02 levels at the
wound site, stimulates capillary budding and granulation
of new, healthy tissue.
Necrotizing Fasciitis and
Fournier’s gangrene
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Riseman and colleagues reported that addition
of HBO to surgical and antibiotic treatment
reduced mortality versus surgery and antibiotics
alone.
May suppress growth of anaerobic organisms
 May increase leukocyte function and suppress
bacterial growth
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Blood loss anemia
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Intermittent hyperbaric therapy exposures have
been used to relieve temporary physiologic stress
from acute anemia
Rarely used for this purpose
May be useful when crossmatching
incompatibilities and religious beliefs prevent
blood transfusions
Crush injury
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HBO is used in limited degree for acute traumatic
peripheral ischemia and suturing of severed limbs.
Reduces infection and wound dehiscence and improves
healing
Improves oxygenation to hypoperfused tissue
Causes arterial hyperoxia causing vasoconstriction and
decreased edema formation.
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Also, intermittent pressure stimulates circulation and reduces
edema.
Early use of HBO may reduce compartment pressures
enough to avoid fasciotomy.
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Gamow Bags, a rescue
product for high-altitude
climbers and trekkers, is
used for the treatment of
moderate to extreme
altitude sickness. By
increasing air pressure
around the patient, the
Bag simulates descents as
much as 7,000 feet
Emerging concepts
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Increasing interest and research regarding HBO
therapy as adjunct treatment in wound healing
Use of HBO in multiple sclerosis, cerebral palsy,
and vegetative coma is also being explored
OMM Considerations
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None