Review of Oxygen Therapy

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Review of Oxygen Therapy

• RsCr 224
• Respiratory Care Theory 2
• Fall 2003

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Characteristics of Oxygen

• Colorless, odorless, tasteless, transparent
• Non-flammable supports combustion
• 21 of atmosphere
• FDA standards of 99 pure
• Exerts 159 mmHg of pressure (of 760)
• Slightly heavier then air
• Critical temperature 119 degrees C

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Signs Symptoms of Hypoxemia

• Tachypnea
• Increased accessory muscle use
• Patient c/o dyspnea
• Tachycardia
• Cyanosis (in severe cases only)
• Restlessness disorientation impaired
  judgement confusion somnolence loss of
  coordination coma

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Long Term Consequences of Hypoxemia (persistent)

• Clubbing

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Mini Clini

• A disoriented postoperative male patient
  breathing room air exhibits tachypnea,
  tachycardia and mild cyanosis of the mucus
  membranes. Using a pulse oximeter, you measure
  the patients oxyhemoglobin saturation as 93.
  What would you recommend?

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Assessing the Need for Supplemental Oxygen

• Initial assessment is generally based upon values
  of oxygen obtained by using a pulse oximeter
  (SpO2 values)
• These values are not always accurate
• Assessment of need should also be based on other
  observable symptoms (discussed previously)
• The best method for determining need is through
  the analysis of an arterial blood sample (PaO2)

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Indications for Oxygen Therapy

• Suspected hypoxia
• Documented hypoxia
• Trauma
• Myocardial Infarction (MI)
• Heart attack
• Post anesthesia (recovery room)

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AARC Clinical Practice Guidelines

• The oxygen in the arteries is low
• PaO2 lt 60 mmHg
• And / or
• The oxygen saturation is low
• SaO2 lt90

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Levels of Hypoxemia in Adults

• Mild
• 60 - 80 mmHg
• Moderate
• 40 60 mmHg
• Severe
• Less then 40 mmHg

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What is Accomplished by Giving Oxygen to
Hypoxemic Patients?

• Workload on the heart is decreased
• Tachycardia generally goes away
• Blood pressure stabilizes resulting in a decrease
  in heart workload
• Since hypoxemia actually causes pulmonary
  vasoconstriction - once hypoxemia is relieved,
  pulmonary vasoconstriction goes away.
• Long term hypoxemia causes Right Heart Failure

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What else is Accomplished by Giving Oxygen to
Hypoxemic Patients?

• Mental capacity increases - patients become more
  alert and less sleepy confusion diminishes
• Breathing workload diminishes - tachypnea
  decreases or vanishes accessory muscle use
  decreases
• Color improves - patients become less pale or
  less cyanotic capillary refill improves

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Precautions Hazards Associated with the Use of
Oxygen

• Oxygen Toxicity

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Development of Oxygen Toxicity is Dose Related

• How much oxygen is the patient receiving? (What
  is the FIO2?)
• Risk is present if FIO2 is gt.50
• Risk increases as FIO2 increases above .50
• How long has the patient been receiving it?
• Lung damage begins to occur in as little as 12
  hours
• Clinical symptoms begin to show up in 24 hours
  (worsening hypoxemia)
• Severe damage will occur after 48-72 hours
  (Exudative phase)

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Other Precautions Hazards of Oxygen Use

• Oxygen Induced Hypoventilation
• Commonly seen in patients with COPD who are
  considered Blue Bloaters

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What Makes These Patients Vulnerable?

• They tend to be hypercapnic (CO2 values may be 20
  to 23 torr above normal)
• They tend to ventilate less than normal
  individuals
• They tend to breath based mainly upon peripheral
  chemoreceptor drive
• Too much oxygen causes them to decrease their
  depth rate of breathing- leading to a further
  drop in pH and potentially serious cardiac
  problems

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Other Precautions Hazards of Oxygen Use

• Retinopathy of Prematurity (retrolental
  fibroplasia)
• Only seen in neonates who are given enough oxygen
  sufficient to raise the PaO2 above 100 torr.
• Only affects the arteries of the eyes and is only
  operative for about the first month of life.
• Can cause blindness
• Simple prevention by keeping PaO2 to lt80 torr

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Other Precautions Hazards

• Absorption Atelectasis
• Occurs when airways are blocked after the patient
  has been receiving a high level of oxygen (gt.50)
• Results in the collapse of the area distal to the
  obstruction as remaining oxygen is removed and
  cannot be replaced

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Schematic of Development of Absorption
Atelectasis
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Types of Oxygen Delivery System

• High Flow Systems
• Includes enclosures
• Low Flow Systems
• Includes reservoir systems

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Low Flow Systems

• Do not meet or exceed the patients peak flow
  demand
• Examples - nasal cannulas simple masks
  nonrebreathing masks transtracheal catheters

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Nasal Cannula
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Nasal Catheter
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Transtracheal Catheter
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Reservoir Cannula
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Pendant Cannula
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Simple Oxygen Mask
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Partial rebreathing andNon-Rebreathe
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High Flow Systems

• Generally must be able to deliver a total flow of
  gt 30 - 40 l/m
• Air Entrainment Masks (Venti-masks) Large Volume
  Jet Nebulizers Blending Systems (rarely used)

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Venturi Mask
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Characteristics of Entrainment Systems

• As FIO2 is increased - total flow decreases
• Therefore source gas flow must be set higher on
  the flowmeter to compensate for this fact
• Entrainment systems are sensitive to backpressure
  occurring downstream from the jet
• Any resulting backpressure will decrease air
  entrainment which will lead to an increase in
  FIO2 and a decrease in total flow. Backpressure
  issues should be avoided!!

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Aerosol Setup
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Schematic of a Blender Type High Flow System
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How Blenders Work

• A Blender requires a source of 50 psi oxygen and
  a source of 50 psi air. Gas is blended to
  provide 50 psi blended gas at any FIO2 between 21
  100.
• A flowmeter can be attached to the blenders 50
  psi DISS outlet connector OR
• A ventilator requiring 50 psi can be attached
  directly to the 50 psi outlet on the blender

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Picture of an Oxygen Blender
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Other Less Common Oxygen Delivery Methods

• Oxygen Tents (Croup Tents) Used for children
• Infant Oxygen Hood
• Infant Incubator

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Croup Tent
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Head Hood
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Infant Incubator
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Hyperbaric Oxygen

• Used for
• Tx of air embolism
• Carbon Monoxide poisoning
• To enhance wound healing
• Necrotizing soft tissue infections
• Exceptional blood loss
• Tx of refractory osteomyelitis
• Radiation Necrosis

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A Monoplace Hyperbaric Chamber
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Other Therapeutic Gases

• Nitric Oxide - used to enhance blood flow through
  the lungs by selectively dilating pulmonary
  vessels.
• Helium- Heliox - used in mixtures of 80 oxygen -
  20 helium or 90 oxygen - 10 helium
• Used in conjunction with small volume nebulizer
  therapy to enhance drug deposition in cases of
  severe asthma
• Correction factor when using 80/20 is 1.8.
  Multiply this value times flowrate setting on the
  flowmeter to determine actual flow.
• Carbon Dioxide and Oxygen (Carbogen)
• Act as a respiratory stimulant, treat singulation

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End of Review

• Thats all folks