Hyperbaric Oxygen Therapy Module II

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Hyperbaric Oxygen TherapyModule II

• CRC 432
• Subacute Cardiorespiratory Care
• Problem-Based Learning

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HBO OUTLINE

• Definitions
• History
• Altitude/descent
• Gas laws
• Physiological effects of HBO

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Hyperbaric Oxygen Therapy

• Therapeutic oxygen at pressures greater than 1
  atm
• Unit expressing HBO pressure ata
• Ata atmospheric pressure absolute
• 1 ata 1 atmosphere (atm), or 760 torr
• HBO general pressure range 2 to 3 ata

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Hyperbaric Oxygen Therapy

• Pressure
• pressure force/area
• Force
• force mass x acceleration

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Hyperbaric Oxygen Therapy

• Ambient pressure surrounding pressure on land,
  or under water.
• Atmospheric pressure surrounding pressure
  caused by the weight of air.
• Water pressure surrounding pressure caused by
  weight of water.

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Hyperbaric Oxygen Therapy

• Barometric pressure measure of atmospheric
  pressure
• Barometric pressure atmospheric pressure
• When surrounded by air
• atmospheric pressure
• ambient pressure
• barometric pressure

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Hyperbaric Oxygen Therapy

• When surrounded by water
• atmospheric pressure
• water pressure
• ambient pressure
• CAUTION!!! Dont confuse atmospheric pressure
  atmosphere as unit

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Hyperbaric Oxygen Therapy

• Atmospheric pressure can be ANY value
• 1 atm (sea level)
• ½ atm (8,000 feet elevation)
• 3 atm (hyperbaric chamber)

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Hyperbaric Oxygen Therapy

• ABSOLUTE PRESSURE vs. GAUGE PRESSURE
• 33 ft sea water 1 atm
• Gauges set sea level pressure at 0
• At 33 ft depth, gauge indicates 1 atm
• Absolute pressure 2 atm

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Hyperbaric Oxygen Therapy

• Standard atmospheric pressure average sea level
  pressure
• 14.7 psi
• 1034 cm H2O
• 101.3 kPa
• 760 mm Hg (torr)
• 33 ft H2O
• 29.9 in Hg

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Hyperbaric Oxygen Therapy

• First sealed chamber called Domicilium built in
  1662
• Chamber held compressed air (21 O2)
• Treated various ailments scurvy, arthritis,
  inflammation, rickets
• Likely too little compression to benefit patients

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Hyperbaric Oxygen Therapy

• Beddoes is known as the Father of Respiratory
  Therapy
• Thomas Beddoes founded the Pneumatic Institute
  in Bristol, England 1780
• Patients inhaled different gases to treat their
  diseases
• Pneumatic laboratory enriched with O2 treated
  chronic conditions
• Father of English poet Thomas Lovell Beddoes

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Hyperbaric Oxygen Therapy

• J. Priestly discovered O2 in England 1776
• Antoinne Lavoisier of France shares O2 discovery

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Hyperbaric Oxygen Therapy

• GAS LAWS
• Air under hyperbaric conditions obeys the same
  gas laws as air in the atmosphere.
• Boyles law (1627 1691)
• Daltons law (1766 1844)
• Henrys law (1774 1790)

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Hyperbaric Oxygen Therapy

• Boyless law
• When mass T are K, V P inverse.
• K V x P
• K 2V x ½P
• K ½V x 2 P
• If P increases, V decreases, vice versa.

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Hyperbaric Oxygen Therapy

• Boyles law
• When mass T are K, D P direct.
• K D/P
• Consider container open at one end holding 1 L at
  1 atm.
• At 2 atm, V by ½, D doubles.
• At 3 atm, V by ?, D triples.

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Hyperbaric Oxygen Therapy

• Boyles law
• During HBO, density in lungs increases.
• Deep scuba diving density of air increases,
  breathing becomes more difficult.

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Hyperbaric Oxygen Therapy

• Daltons law
• PT pressure exerted by gas equals the sum of
  all the Pgas of the constituent gases.
• PT P1 P2 P3 . . . Pn

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Hyperbaric Oxygen Therapy

• Daltons law
• To calculate the partial pressure of a gas in a
  mixture of gases
• Pgas Fgas (PT PH2O)

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Hyperbaric Oxygen Therapy

• Daltons law
• TRUE or FALSE
• The sum of the partial pressures of all the
  gases in a gas mixture can never exceed the total
  pressure of the gas mixture.
• ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
  

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Hyperbaric Oxygen Therapy

• Daltons law
• TRUE!!!

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Hyperbaric Oxygen Therapy

• Daltons law
• TRUE or FALSE
• As air pressure increases (hyperbarism) or
  decreases (altitude), the partial pressures
  exerted by the constituent gases increases or
  decreases, as well.
• ???????????????????????????????????????

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Hyperbaric Oxygen Therapy

• Daltons law
• TRUE!!!

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Hyperbaric Oxygen Therapy

• Daltons law
• TRUE or FALSE
• When room air is compressed in a hyperbaric
  chamber, the percentage of the individual gases
  in the mixture is the same.
• ???????????????????????????????????????

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Hyperbaric Oxygen Therapy

• Daltons law
• TRUE!!!

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Hyperbaric Oxygen Therapy

• Daltons law
• Lower partial pressures at altitude reflect
  presence of less O2 N2 molecules per volume
  compared to sea level.
• Summit at Mt. Everest (29,000 ft)
• 21 O2, 78 N2, 1 other
• of O2 N2 molecules per volume of air only 1/3
  that at sea level.
• PO2 PN2 only 1/3 that at sea level

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Hyperbaric Oxygen Therapy

• Henrys law
• Amount of gas that dissolves in a liquid at a
  given temperature is a function of the partial
  pressure of the gas in contact with the liquid,
  and the solubility of the gas in that particular
  liquid.

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Hyperbaric Oxygen Therapy

• Henrys law
• SIMPLIFIED As the partial pressure of a gas
  above the surface of a liquid increases, more of
  that gas will dissolve into that liquid.

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Hyperbaric Oxygen Therapy

• Henrys Daltons laws
• When ambient pressure decreases (altitude), the
  partial pressures of O2 N2 in the body fall,
  and fewer O2 N2 molecules dissolve into the
  blood.

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Hyperbaric Oxygen Therapy

• Henrys Daltons laws
• When ambient pressure increases (hyperbarism),
  the partial pressures of O2 N2 in the body
  increase, and more O2 N2 molecules dissolve
  into the blood.

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Hyperbaric Oxygen Therapy

• Physiologic Effects
• Hyperoxygenation
• Increases volume of O2 in plasma
• 10 to 13 x greater than normal
• Elevated O2 levels purge toxins CO from the body

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Hyperbaric Oxygen Therapy

• Physiologic Effects
• Hyperoxygenation
• At sea level while breathing room air plasma O2
  concentration is 0.3 vol
• 100 torr x 0.003 vol/torr 0.3 vol

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Hyperbaric Oxygen Therapy

• Physiologic Effects
• Hyperoxygenation
• At sea level while breathing room air plasma O2
  concentration is 0.3 vol
• 100 torr x 0.003 vol/torr 0.3 vol

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Hyperbaric Oxygen Therapy

• Physiologic Effects
• Hyperoxygenation
• Alveolar Air Equation

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Hyperbaric Oxygen Therapy

• Physiologic Effects
• Hyperoxygenation
• HBO patient breathing FIO2 0.4_at_ 2.5 atm

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Hyperbaric Oxygen Therapy

• Hyperoxygenation
• PAO2 1,807 torr
• 1,807 torr x 0.003 vol/torr 5.4 vol

PAO2 0.4 (1,900 torr 47 torr) 40 torr(1.15)
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Hyperbaric Oxygen TherapyNormal a-v difference
5.0 vol

• Arterial Blood
• PaO2 100 torr
• SaO2 97.5
• Hb 15 g

• Mixed Venous Blood
• PvO2 46 torr
• SvO2 73
• Hb 15 g

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Hyperbaric Oxygen Therapy

• CaO2 (1.34)(15) (0.975) 100(0.003)
• 19.6 vol
• CvO2 (1.34)(15)(0.73) 46(0.003 vol.torr)
• 14.6 vol
• CaO2 CvO2 a-v diff 5.0 vol

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Hyperbaric Oxygen Therapy

• PHYSIOLOGIC EFFECTS
• Hyperoxygenation
• HBO increases dissolved oxygen in the plasma

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Hyperbaric Oxygen Therapy

• Physiologic Effects
• Direct Pressure
• Shrinks gas bubbles (Boyles law) to expedite
  reabsorption of gases
• Good for decompression sickness (DCS aka the
  bends)
• Good for air/gas embolism

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Hyperbaric Oxygen Therapy

• Physiologic Effects
• Vasoconstriction
• Reduces blood flow
• No significant reduction in tissue O2nation
• Benefits crushing type injuries
• Benefits thermal burns
• O2 directly enters interstitial fluid promoting
  healing

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Hyperbaric Oxygen Therapy

• Physiologic Effects
• Bactericidal/Bacteriostatic
• Halts spread of toxins
• Enhances killing of bacteria
• Stimulates production of neutrophils

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Hyperbaric Oxygen Therapy

• Physiologic Effects
• Angiogenesis/Neovascularization
• Promote growth of new blood vessels
• Promote collagen formation to support new blood
  vessels

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Hyperbaric Oxygen Therapy

• Atmospheric pressure caused by weight of gas
  molecules in contact with earths surface
• Atmospheric pressure exerted on a surface of
  water
• Pressure decreases with altitude
• Denver, CO at 5,280 ft elevation 1 atm 630 torr

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Hyperbaric Oxygen Therapy

• Water more dense than air
• 33 ft sea water 1 atm (760 torr)
• Pressure at any depth hydrostatic pressures
  atm pressure
• Depth of 33 ft of H2O 2 atm, or 2 ata
• At 33 ft H2O, 2,112 lbs over each ft2 of body (33
  ft x 64 lbs/ft3 2,112 lbs/ft2)
• 66 ft H2O 3 ata

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Hyperbaric Oxygen Therapy

• Indications CHRONIC
• Nonhealing wounds
• Refractory osteomyelitis
• Radiation necrosis
• www.uhms.org/indications/indications.htm

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Hyperbaric Oxygen Therapy

• Hazards
• Fire 50 deaths worldwide in 20 years (1997)
• Most common FATAL complication
• Only 100 cotton fabrics in chambers
• No alcohol/petroleum products
• No sprays, makeup, deodorant
• Barotrauma
• Ear/sinus trauma
• Tympanic membrane rupture
• pneumothorax

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Hyperbaric Oxygen Therapy

• Hazards
• O2 Toxicity
• CNS toxicity (twitching, seizures, convulsions)
• Pulmonary toxicity (leaky A/C membrane)
• Other
• Sudden decompression
• Reversible visual changes
• Claustrophobia

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Hyperbaric Oxygen Therapy

• Hyperbaric Chambers
• Monoplace transparent Plexiglas cylinder
• One patient
• No mask
• No electric equipment inside
• 100 oxygen
• Less expensive than multi-place

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Hyperbaric Oxygen Therapy
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Hyperbaric Oxygen Therapy
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Hyperbaric Oxygen Therapy

• Multi-place chambers
• large tanks able to accommodate 2 14 people
• achieve pressures up to 6 atm
• have a chamber lock entry system that allows
  medical personnel to pass through without
  altering the pressure of the inner chamber
• allows patients to be directly cared for by staff
• filled with compressed air patients breathe 100
  oxygen through facemask, head hood, or
  endotracheal tube.

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Hyperbaric Oxygen Therapy
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Hyperbaric Oxygen Therapy
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COHb SYMPTOMS
10 Usually none
10-20 Mild headache, dyspnea
20-30 Throbbing headache, impaired concentration
30-40 Severe headache, impaired thinking
40-50 Confusion, lethargy , syncope
50-60 Respiratory failure, seizures
60-70 Coma, convulsions, depressed cardiac respiratory function
70 Coma, rapidly fatal