Oxygen Topics

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Oxygen Topics

• Oxygen Analyzers
• Monitoring Oxygen Therapy

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Four types of Analyzers

• Physical
• Paramagnetic
• Electrical
• Wheatstone Bridge
• Electro-Chemical
• Galvanic
• Polarographic

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Physical Oxygen Analyzers

• Uses principle of paramagnatism
• Oxygen align themselves with a magnetic field
• Measures partial pressure and displays FiO2

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Physical analyzer
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Electrical Oxygen Analyzers

• Uses Wheatstone bridge
• Can only measure in limited situations

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Electric analyzer
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Electrochemical Galvanic

• Has negative and positive electrodes
• Gold and lead
• Measures partial pressure but displays percentage
  of oxygen

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Galvanic analyzer
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Electrochemical Polarographic

• The most often seen clinically today
• Fast acting
• Easy turn on and off
• Intermittent or continuous
• Uses 9-volt battery

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Polarographic analyzer
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Monitoring Oxygen Therapy

• ABGs
• Pulse oximetry
• Transcutaneous

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Monitoring Patient

• Clinical assessment including but not limited to
  cardiac, pulmonary, and neurological status
• Assessment of physiologic parameters measurement
  of oxygen tensions or saturation in any patient
  treated with oxygen

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AARC Guidelines

• In conjunction with the initiation of therapy or
  
• Within 12 hours of initiation with FIO2 lt 0.40
• Within 8 hours, with FIO2 gt or 0.40 (including
  post anesthesia recovery)

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AARC Guidelines

• Within 72 hours in acute myocardial infarction
• Within 2 hours for any patient with the principal
  diagnosis of COPD
• Within 1 hour for the neonate

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Invasive Monitoring
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Invasive Methods

• Arterial Blood Gases (ABGs)
• Puncture
• Art Line
• Is measured in Blood Gas Machines
• ABG machine
• Co-oximeter

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Arterial Blood Gas

• Most accurate
• Direct measurement of P02, PC02 and pH
• Greater risks of complications
• Only a instantaneous picture of a long time line
• Open to misinterpretation

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Puncture
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Arterial Line

• All patients
• in ICU
• need an
• Art line.
• Paul T.

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Co-oximetry

• Usually performed with ABG analysis
• Small hospitals often do NOT have
• A second machine that measures blood sample for
  abnormal types of hemoglobin.

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Non-Invasive Monitoring

• Pulse Ox
• Transcutaneous

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Noninvasive Methods

• Pulse Oximetry
• Continuous or Spot monitoring
• Transcutaneous
• With neonates only

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Pulse Oximetry

• Most common method used to monitor patients
  oxygenation status
• Uses two wavelengths of red and infra-red light
  to measure if the hemoglobin is carrying oxygen
• Displays saturation and Heart Rate

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Continuous Pulse Ox

• Continuous SpO2 monitoring may be indicated
  throughout a bronchoscopy for detecting episodes
  of desaturation
• CPOX is always indicated in the ICU

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Spot Checks

• A spot check may suffice for evaluating the
  efficacy of continued oxygen therapy in a stable
  postoperative patient.
• Every 4 hours (Q4h) is suitable for most floor /
  ward patient

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Location

• Usually on adult patients finger
• Bridge of nose
• Ear Lobe
• Toe
• Usually on infants foot

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Pulse Oximetry

• Limitations
• Movement
• Poor peripheral circulation
• Nail polish
• Can NOT tell if hemoglobin is dysfunctional
• False reading with Carbon Monoxide Poisoning

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Limitations to Pulse Ox

• Some intravascular dyes
• Used during some procedures
• Exposure of light to the probe
• Skin pigmentation

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Validation

• Clinically patient does not look like the
  saturation reading
• Need a continuous strong pulse for 5 to 10
  seconds
• Correlate pulse with other means
• Often we need to validate the readings of the
  pulse ox with the results of an ABG.

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Clinical Judgment

• Often there is an unacceptable disparity between
  the patient condition and pulse oximetry device.
• Clinical judgment must be exercised.
• SpO2 results should reflect the patient's
  clinical condition

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Trained Personnel

• Pulse oximetry is a relatively easy procedure to
  perform. However, if the procedure is not
  properly performed or if it is performed by
  persons who are not cognizant of device
  limitations or applications, spurious results can
  lead to inappropriate intervention.

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Transcutaneous Monitoring
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Transcutaneous Monitoring

• The skin is heated to 44 to 45oC
• Thin skin of neonates and newborns are ideal
• It is more sensitive then pulse oximetry
• Can cause burns to skin
• Therapist must move electrodes every 2 to 4 hours

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Diagram of Sensor
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Contraindications

• Patients with
• - poor skin integrity
• - adhesive allergies

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Assessment of Need

• When direct measurement of arterial blood in not
  available.
• Limitation
• Results should reflect clinical condition
• Trends are more important than readings (TC are
  lower than actual)

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The End