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					Hyperbaric Medicine
    Rosen‟s Chapter 200
      March 1, 2007



   Michael Savino, PGY-2
     Hyperbaric Oxygen Therapy
              (HBO)
   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)
   Primary therapy for:
     Decompression sickness
     Air embolism

     Carbon monoxide poisoning

   Adjunct therapy for:
     Surgical intervention
     Antibiotics
            Accepted Indications
   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
   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.
       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
   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
   Boyle’s Law – pressure and volume inversely
    proportional under constant temperature
       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.
       By increasing ambient pressure, more oxygen can be
        dissolved in the plasma
           Mechanism of action
   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
   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
   Middle ear barotrauma
       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
   Pulmonary barotrauma
     Rare
     Suspect if pulmonary or hemodynamic changes
      occur during or shortly after decompression
     Place chest tube if pneumothorax develops
                     Complications
   Oxygen Toxicity - Manifested by injuries to lungs, CNS,
    and eyes:
   Lungs –
       Can impair elasticity, vital capacity, and gas exchange. Rare.
        But may occur when duration and pressures exceed normal
        therapeutic protocols
   CNS toxicity –
       Manifests as a grand mal seizure. (1-4/10,000 patients).
       Risk is higher in hypercapnic, acidotic, or septic patients
   Eyes –
       Progressive myopia has been reported in patients undergoing
        repetitive daily therapy
       Reversible within 6 weeks of discontinuing treatment
    CLINICAL APPLICATIONS
   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
   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
           Also occurs in miners and astronauts
Emergency treatment of gas bubble
            disorders
   ABC‟s plus hyperbaric oxygen therapy
       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
   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
   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.
       Incidence of sequelae is 25-50% after severe poisoning
     Carbon Monoxide Poisoning
   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
            Clostridial Myonecrosis
                (gas gangrene)
   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
   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
             Blood loss anemia
   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

   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.
       Also, intermittent pressure stimulates circulation and reduces
        edema.
   Early use of HBO may reduce compartment pressures
    enough to avoid fasciotomy.
   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
   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
   None

				
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