Hyperbaric oxygen therapy (29)
Up to date – Hyperbaric Oxygen Therapy - C Crawford Mechem, MD, FACEP
Scott Manaker, MD, PhD
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Hyperbaric oxygen is used as a primary or adjunctive therapy in many conditions
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Air or gas embolism/Decompression sickness
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Divers breathing compressed air who return to the surface too rapidly, and aviators
ascending over 5500 meters are at risk for decompression sickness and arterial gas
embolism
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Treatment consists of a 2 to 5 hour session at 2.5 to 3.0 atm, until symptoms abate
Clostridial myonecrosis/ Actinomycotic brain abscess/ Refractory osteomyelitis/ Necrotizing
soft tissue infections
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Although no randomized, controlled trials in humans have been conducted, a
rigorous study evaluating combinations of antibiotics, surgery, and HBO for
clostridial infection in a dog model has demonstrated a 35 percent survival increase
with adjunctive HBO
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HBO has been advocated for use in other severe invasive infections such as
cutaneous soft-tissue and rhinocerebral mucormycosis (or zygomycosis) and
actinomycotic brain abscesses, although data in support of these indications are less
robust
Crush injury and other forms of traumatic ischemia
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The potential efficacy of this approach was evaluated in a trial in which 36 patients
with crush injuries were randomly assigned to either a 90 minute twice daily HBO
treatment or a 90 minute twice daily sham treatment
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The group treated with HBO had significantly more complete healing (17 versus 10
patients) and required fewer skin flaps, grafts, vascular surgery, or amputation (1
versus 6 patients).
Enhanced healing of problematic wounds, including diabetic wounds
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Two small prospective randomized controlled trials of HBO therapy for 46 patients
with chronic diabetic foot ulcers found significantly improved wound resolution
among patients treated with HBO
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Therapy for nonhealing wounds generally consists of up to 30 to 70 90 minute
sessions at 2.0 to 2.5 atm
Severe anemia
Radiation necrosis of soft tissue and bone
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Previously irradiated tissue is characterized by fibro-atrophic changes, with
decreased vascularity, impaired cellular proliferation, and local hypoxia that can
persist long after radiation therapy
Compromised skin grafts and flaps
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Patients who require skin grafting or reconstructive flaps in areas with local
vascular compromise, previous radiation therapy, or in sites of previous graft failure
may benefit from HBO
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In a retrospective review of 105 patients with risk factors for skin graft and flap
failure (diabetes, peripheral vascular disease, irradiation, or chronic infection),
approximately 90 percent had flap and graft survival with adjunctive HBO therapy
[65]. In comparison, earlier studies reported graft and flap survival rates of 17 to 60
percent in patients with similar risk factors
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Mechanism of Action
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Increased Oxygen Delivery
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Henrys law = the amount of gas dissolved in solution is directly proportional to its
partial pressure
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3 atm yields a dissolved O2 content of 6mg/dl – an amount adequate for RESTING
tissue oxygen requirements despite irrespective of the adequacy of the hemoglobinoxygen pool
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Reduction of gas bubble size
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Boyle's Law - the volume of nitrogen bubbles is inversely related to the pressure
exerted upon it
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At 3.0 atm, bubble volume decreases by approximately two-thirds
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bubble dissolution is accomplished by the replacement of inert nitrogen within the
bubbles with oxygen, which is then rapidly metabolized by tissues
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Antagonism of carbon monoxide
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Carbon monoxide (CO) binds to hemoglobin with an affinity 200 to 250 times as
great as that of oxygen
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The 4 to 6 hour half-life of COHb at ambient air decreases to 40 to 80 minutes with
100 percent normobaric oxygen (NBO). With HBO therapy, the half-life of COHb
decreases further, to 15 to 30 minutes
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Improved wound healing
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Local hyperoxia induces vasoconstriction and reduces vasogenic edema following
acute trauma
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HBO ameliorates ischemia-reperfusion-induced leukocyte influx
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HBO augments neutrophil bactericidal activity, limits clostridial exotoxin and spore
production, kills anaerobes such as Clostridium perfringens, and inhibits the growth
of several other bacterial pathogens
Technique
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Multiplace chambers allow closer monitoring of critically ill patients, while single occupancy
chambers are most appropriate for the treatment of chronic medical conditions in stable
patients
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Chamber pressure 2.5-3 atm
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Duration of therapy – 45-300 minutes
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Acute indications – 1-2 treatments
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Chronic indications – up to 30 treatments
Contraindications
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Absolute - Untreated pneumothorax
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Relative – seizure disorder, pneumothorax, chest surgery
Complications
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Reversible myopia secondary to oxygen toxicity of the lens (20%)
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Symptomatic otic barotraumas (3-20%)
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Middle ear symptoms may be alleviated by tympanos6tomy tubes
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Pulmonary barotraumas
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Unusual providing that pneumothoraces have been decompressed
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Pulmonary oxygen toxicity
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manifested by chest tightness, cough, and a reversible decline of pulmonary
function, occurs most commonly in patients receiving multiple treatments or
previously exposed to high oxygen levels
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Seizures
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due to central nervous system oxygen toxicity are a rare but dramatic consequence
of HBO treatment
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The risk is increased by HBO exposure greater than 90 to 120 minutes and by
pressures greater than 2.8 to 3.0 atm
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Risk factors = glucocorticoids, insulin, thyroid replacement and sympathomemetic
medications
Treatment
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Decrease FiO2 to 21%
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Give anticonvulsant therapy
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Alternating short periods of air with hyperbaric oxygen