Transcript Hyperbaric Oxygen Therapy - Web Page Maker : Make your …

Hyperbaric Oxygen Therapy
Module II
CRC 432
Subacute Cardiorespiratory Care
Problem-Based Learning
HBO OUTLINE
•
•
•
•
•
Definitions
History
Altitude/descent
Gas laws
Physiological effects of HBO
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
Hyperbaric Oxygen Therapy
• Pressure:
pressure = force/area
• Force:
force = mass x acceleration
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.
Hyperbaric Oxygen Therapy
• Barometric pressure = measure of
atmospheric pressure
• Barometric pressure = atmospheric
pressure
• When surrounded by air:
atmospheric pressure =
ambient pressure =
barometric pressure
Hyperbaric Oxygen Therapy
• When surrounded by water:
atmospheric pressure =
water pressure =
ambient pressure
• CAUTION!!! Don’t confuse:
atmospheric pressure & atmosphere as
unit
Hyperbaric Oxygen Therapy
• Atmospheric pressure can be ANY
value:
1 atm (sea level)
½ atm (8,000 feet elevation)
3 atm (hyperbaric chamber)
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
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
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
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
Hyperbaric Oxygen Therapy
• J. Priestly discovered O2 in England
1776
• Antoinne Lavoisier of France shares O2
discovery
Hyperbaric Oxygen Therapy
GAS LAWS
Air under hyperbaric conditions obeys the
same gas laws as air in the atmosphere.
Boyle’s law (1627 – 1691)
Dalton’s law (1766 – 1844)
Henry’s law (1774 – 1790)
Hyperbaric Oxygen Therapy
Boyles’s law
• When mass & T are K, V & P inverse.
K=VxP
K = 2V x ½P
K = ½V x 2 P
• If P increases, V decreases, & vice versa.
Hyperbaric Oxygen Therapy
Boyle’s 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 ⅓, & D triples.
Hyperbaric Oxygen Therapy
Boyle’s law
• During HBO, density in lungs increases.
• Deep scuba diving: density of air
increases, & breathing becomes more
difficult.
Hyperbaric Oxygen Therapy
Dalton’s law
• PT = pressure exerted by gas equals the
sum of all the Pgas of the constituent
gases.
PT = P1 + P2 + P3 = . . . Pn
Hyperbaric Oxygen Therapy
Dalton’s law
To calculate the partial pressure of a
gas in a mixture of gases:
Pgas = Fgas (PT – PH2O)
Hyperbaric Oxygen Therapy
Dalton’s 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.
????????????????????????
Hyperbaric Oxygen Therapy
Dalton’s law
TRUE!!!
Hyperbaric Oxygen Therapy
Dalton’s 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.
???????????????????????????????????????
Hyperbaric Oxygen Therapy
Dalton’s law
TRUE!!!
Hyperbaric Oxygen Therapy
Dalton’s 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.
???????????????????????????????????????
Hyperbaric Oxygen Therapy
Dalton’s law
TRUE!!!
Hyperbaric Oxygen Therapy
Dalton’s 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
Hyperbaric Oxygen Therapy
Henry’s 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.
Hyperbaric Oxygen Therapy
Henry’s 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.
Hyperbaric Oxygen Therapy
Henry’s & Dalton’s 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.
Hyperbaric Oxygen Therapy
Henry’s & Dalton’s 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.
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
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%
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%
Hyperbaric Oxygen Therapy
Physiologic Effects
• Hyperoxygenation
Alveolar Air Equation:
 1.0  FOI 2 
PAO  FO (P  P )  PaCO  FO 


R 
1.0  FIO2 

PAO2  FIO2 (PT  PH 2O)  PaCO2  FIO2 



R
I
H
O
I
2
2 T
2
2 2
1.0  FIO 2 

PAO 2  FIO 2 (PT  PH 2 O)  PaCO2  FIO 2 

R


Hyperbaric Oxygen Therapy
Physiologic Effects
• Hyperoxygenation
HBO patient breathing FIO2 0.4@ 2.5 atm
 1.0 0.4
PAO2  0.4(1,900torr 47torr) 40torr 0.4 
 0.8 
1.0 0.4 

PAO 2  0.4(1,900torr 47torr) 40torr 0.4


0.8 
Hyperbaric Oxygen Therapy
Hyperoxygenation
PAO2 = 0.4 (1,900 torr – 47 torr) – 40 torr(1.15)
PAO2 = 1,807 torr
1,807 torr x 0.003 vol%/torr = 5.4 vol%
Hyperbaric Oxygen Therapy
Normal 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%
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%
Hyperbaric Oxygen Therapy
PHYSIOLOGIC EFFECTS
• Hyperoxygenation
– HBO increases dissolved oxygen in the
plasma
Hyperbaric Oxygen Therapy
Physiologic Effects
• Direct Pressure
– Shrinks gas bubbles (Boyle’s law) to
expedite reabsorption of gases
– Good for decompression sickness (DCS –
aka: “the bends”)
– Good for air/gas embolism
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
Hyperbaric Oxygen Therapy
Physiologic Effects
• Bactericidal/Bacteriostatic
– Halts spread of toxins
– Enhances killing of bacteria
– Stimulates production of neutrophils
Hyperbaric Oxygen Therapy
Physiologic Effects
• Angiogenesis/Neovascularization
– Promote growth of new blood vessels
– Promote collagen formation to support new
blood vessels
Hyperbaric Oxygen Therapy
• Atmospheric pressure caused by weight
of gas molecules in contact with earth’s
surface
• Atmospheric pressure exerted on a
surface of water
• Pressure decreases with altitude
• Denver, CO at 5,280 ft elevation; 1 atm
= 630 torr
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
Hyperbaric Oxygen Therapy
• Indications – CHRONIC
– Nonhealing wounds
– Refractory osteomyelitis
– Radiation necrosis
www.uhms.org/indications/indications.htm
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
Hyperbaric Oxygen Therapy
• Hazards
– O2 Toxicity
• CNS toxicity (twitching, seizures,
convulsions)
• Pulmonary toxicity (leaky A/C
membrane)
– Other
• Sudden decompression
• Reversible visual changes
• Claustrophobia
Hyperbaric Oxygen Therapy
• Hyperbaric Chambers
– Monoplace transparent Plexiglas cylinder
– One patient
– No mask
– No electric equipment inside
– 100% oxygen
– Less expensive than multi-place
Hyperbaric Oxygen Therapy
Hyperbaric Oxygen Therapy
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.
multiplacehyperchamber.jpg
Hyperbaric Oxygen Therapy
img_header.jpg
Hyperbaric Oxygen Therapy
multiplacehyperchamber.jpg
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