Monitoring Pulse Oximetry

1
Monitoring Pulse Oximetry

• By the EMT-Basic

2
Objectives

• Understand the Kansas Regulations relative to
  monitoring pulse oximetry by the EMT-B
• Review the signs and symptoms of respiratory
  compromise
• Understand the importance of adequate tissue
  perfusion
• Define hypoxia and describe the clinical signs
  and symptoms

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continued

• Describe the technology of the pulse oximeter
• Define normal parameters of oxygen saturation
• Describe the relationship between oxygen
  saturation and partial pressure oxygen
• Describe the significance of the information
  provided by pulse oximetry
• Describe monitoring pulse oximetry during patient
  assessment

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continued

• Describe the use of pulse oximetry with
  pediatrics
• Describe patient conditions that may affect pulse
  oximetry accuracy
• Describe patient environments that may affect
  pulse oximetry accuracy
• Describe the evaluation and documentation of
  pulse oximetry monitoring

5
Kansas Regulations

• Regulation 109-6-4
• Adopts EMT-Basic Advanced Initiatives
• Allows EMTs to monitor saturation of arterial
  oxygen levels of blood by way of pulse oximetry
• Appropriate physician oversight
• On line medical control or written protocols
• Complete a course of instruction

6
Respiratory Compromise

• Signs and Symptoms
• Dyspnea
• Accessory muscle use
• Inability to speak in full sentences
• Adventitious breath sounds
• Increased or decreased breathing rates
• Shallow breathing
• Flared nostrils or pursed lips

7
continued

• Retractions
• Upright or tripod position
• Unusual anatomy changes

8
Hypoxemia

• Decreased oxygen in arterial blood
• Results in decreased cellular oxygenation
• Anaerobic metabolism
• Loss of cellular energy production

9
Hypoxemia Etiology

• Inadequate External Respiration
• Decreased on-loading of oxygen at pulmonary
  capillaries
• Inadequate Oxygen Transport
• Decreased oxygen carrying capacity
• Inadequate Internal Respiration
• Decreased off-loading of oxygen at cellular
  capillaries

10
External Respiration

• Exchange of gases between the alveoli and
  pulmonary capillaries
• Oxygen diffuses from an area of higher
  concentration to an area of lower oxygen
  concentration
• Oxygen must be available and must be able to
  diffuse across alveolar and capillary membranes
• Oxygen must be able to saturate the hemoglobin

11
Inadequate External Respiration

• Decreased oxygen available in the environment
• Smoke inhalation
• Toxic gas inhalation
• High altitudes
• Enclosures without outside ventilation
• Inadequate mechanical ventilation
• Pain
• Rib fractures
• Pleurisy

12
continued

• Traumatic injuries
• Open pneumothorax
• Loss of ability to change intrathoracic pressures
• Crushing injuries of the neck and chest
• Traumatic asphyxia
• Crushing neck injuries
• Tension pneumothorax
• Increased intrathoracic pressures reducing
  ventilation
• Hemothorax
• Blood in thoracic cavity reducing lung expansion
• Flail Chest
• Loss of ability to change intrathoracic pressures

13
continued

• Other conditions
• Upper Airway Obstruction
• Epiglottitis
• Croup
• Airway Edema-anaphylaxis
• Lower Airway Obstructions
• Asthma
• Airway Edema from inhalation of toxic substances

14
continued

• Hypoventilation
• Muscle Paralysis
• Spinal injuries
• Paralytic drug for intubation
• Drug Overdose
• Respiratory depressants
• Brain Stem Injuries
• Damage to the respiratory center

15
continued

• Inadequate oxygen diffusion
• Pulmonary edema
• Fluid between alveoli and capillaries inhibit
  diffusion
• Pneumonia
• Consolidation reduces surface area of respiratory
  membranes
• Reduces the ventilation-perfusion ratio
• COPD
• Air trapping in alveoli
• Loss of surface area of respiratory membranes

16
continued

• Pulmonary emboli
• Area of the lung is ventilated but hypoperfused
• Loss of functional respiration membranes

17
Oxygen Transport

• Most of the oxygen in arterial blood is saturated
  on hemoglobin
• Red blood cells must be adequate in number and
  have adequate hemoglobin
• Sufficient circulation is necessary to transport
  oxygen to the cellular level

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Inadequate Oxygen Transport

• Anemia
• Reduces red blood cells reduce oxygen carrying
  capacity
• Inadequate hemoglobin results in the loss of
  oxygen saturation
• Poisoning
• Carbon monoxide on-loads on the hemoglobin more
  readily preventing oxygen saturation and oxygen
  carrying capacity
• Shock
• Low blood pressures result in inadequate oxygen
  carrying capacity

19
Internal Respiration

• Exchange of gases from the systemic capillaries
  to the tissue cells
• Oxygen must be able to off-load the hemoglobin
• Oxygen moves from a area of higher concentration
  to an area of lower concentration of oxygen

20
Inadequate Internal Respiration

• Shock
• Oxygen is not available due to massive peripheral
  vasoconstriction or micro-emboli
• Cellular environment is not conducive to
  off-loading oxygen
• Acid Base Imbalance
• Lower than normal temperature
• Poisoning
• CO will reduce the oxygen available at the
  cellular level

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Signs and Symptoms of Hypoxemia

• Restlessness
• Altered or deteriorating mental status
• Increased or decreased pulse rates
• Increased or decrease respiratory rates
• Decreased oxygen oximetry readings
• Cyanosis (late sign)

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Pathophysiology

• Oxygen is exchanged by diffusion from higher
  concentrations to lower concentrations
• Most of the oxygen in the arterial blood is
  carried bound to hemoglobin
• 97 of total oxygen is normally bound to
  hemoglobin
• 3 of total oxygen is dissolved in the plasma

23
Oxygen Saturation

• Percentage of hemoglobin saturated with oxygen
• Normal SpO2 is 95-98
• Suspect cellular perfusion compromise if less
  than 95 SpO2
• Insure adequate airway
• Provide supplemental oxygen
• Monitor carefully for further changes and
  intervene appropriately

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continued

• Suspect severe cellular perfusion compromise when
  SpO2 is less than 90
• Insure airway and provide positive ventilations
  if necessary
• Administer high flow oxygen
• Head injured patients should never drop below 90
  SpO2

25
SpO2 and PaO2

• SpO2 indicates the oxygen bound to hemoglobin
• Closely corresponds to SaO2 measured in
  laboratory tests
• SpO2 indicates the saturation was obtained with
  non-invasive oximetry
• PaO2 indicates the oxygen dissolved in the plasma
• Measured in ABGs

26
continued

• Normal PaO2 is 80-100 mmHg
• Normally
• 80-100 mm Hg corresponds to 95-100 SpO2
• 60 mm Hg corresponds to 90 SpO2
• 40 mm Hg corresponds to 75 SpO2

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Technology

• The pulse oximeter has Light-emitting diodes
  (LEDs) that produce red and infrared light
• LEDs and the detector are on opposite sides of
  the sensor
• Sensor must be place so light passes through a
  capillary bed
• Requires physiological pulsatile waves to measure
  saturation
• Requires a pulse or a pulse wave (Adequate CPR)

28
continued

• Oxygenated blood and deoxygenated blood absorb
  different light sources
• Oxyhemoglobin absorbs more infrared light
• Reduced hemoglobin absorbs more red light
• Pulse oximetry reveals arterial saturation my
  measuring the difference.

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Patient Assessment

• Patient assessment should include all components
• Scene Size-up
• Initial Assessment
• Rapid Trauma Assessment or Focused Physical Exam
• Focused History
• Vital Signs
• Detailed Assessment
• Ongoing Assessment

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Pulse Oximetry Monitoring

• Pulse oximetry monitoring is NOT intended to
  replace any part of the patient assessment
• Pulse oximetry is a useful adjunct in assessing
  the patients oxygenation and monitoring
  treatment interventions
• Initiate pulse oximetry immediately prior to or
  concurrently with oxygen administration

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Continuous Monitoring

• Monitor current oxygenation status and response
  to oxygen therapy
• Monitor response to nebulized treatments
• Monitor patient following intubation
• Monitor patient following positioning patients
  for stabilization and transport
• Decreased circulating oxygen in the blood may
  occur rapidly without immediate clinical signs
  and symptoms

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Pediatrics

• Use appropriate sized sensors
• Adult sensors may be used on arms or feet
• Active movement may cause erroneous readings
• Pulse rate on the oximeter must coincide with
  palpated pulse
• Poor perfusion will cause erroneous readings
• Treat patient according to clinical status when
  in doubt
• Pulse oximetry is useless in pediatric cardiac
  arrest

33
Conditions Affecting Accuracy

• Patient conditions
• Carboxyhemoglobin
• Anemia
• Hypovolemia/Hypotension
• Hypothermia

34
Carboxyhemoglobin

• Carbon monoxide has 200-250 greater affinity for
  the hemoglobin molecule than oxygen
• Binds at the oxygen binding site
• Prevents on-loading of oxygen
• Fails of readily off-load at the tissue cells
• Carboxyhemoglobin can not be distinguished from
  oxyhemoglobin by pulse oximetry
• Erroneously high reading may present

35
continued

• Suspect the presence of carboxyhemoglobin in
  patient with
• Smoke inhalation
• Intentional and accidental CO poisoning
• Heavy cigarette smoking
• Treat carboxyhemoglobin with high flow oxygen
  irregardless of the pulse oximetry reading!

36
Anemia

• Low quantities of erythrocytes or hemoglobin
• Normal value of hemoglobin is 11-18 g/dl
• Values as low as 5 g/dl may result in 100 SpO2
• Anemic patients require high levels of oxygen to
  compensate for low oxygen carrying capacities!

37
Hypovolemia/Hypotension

• Adequate oxygen saturation but reduced oxygen
  carrying capacity
• Vasoconstriction or reduction in cardiac output
  may result in loss of detectable pulsatile
  waveform at sensor site
• Patients in shock or receiving vasoconstrictors
  may not have adequate perfusion to be detected by
  oximetry
• Always administer oxygen to patients with poor
  perfusion!

38
Hypothermia

• Severe peripheral vasoconstriction may prevent
  oximetry detection
• Shivering may result in erroneous oximetry motion
• Pulse rate on oximeter must coincide with
  palpable pulse rate to be considered accurate
• Treat the patient according to hypothermic
  guidelines and administer oxygen accordingly!

39
Patient Environments

• Ambient Light
• Excessive Motion

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Ambient Lighting

• Any external light exposure to capillary bed
  where sampling is occurring may result in an
  erroneous reading
• Most sensors are designed to prevent light from
  passing through the shell
• Shielding the sensor by covering the extremity is
  acceptable

41
Excessive Motion

• New technology filters out most motion artifact
• Always compare the palpable pulse rate with the
  pulse rate indicated on the pulse oximetry
• If they do not coincide, reading must be
  considered inaccurate

42
Other Concerns

• Fingernail polish and pressed on nails
• Most commonly use nails and fingernail polish
  will not affect pulse oximetry accuracy
• Some shades of blue, black and green may affect
  accuracy (remove with acetone pad)
• Metallic flaked polish should be removed with
  acetone pad
• The sensor may be placed on the ear if reading is
  affected

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continued

• Skin pigmentation
• Apply sensor to the fingertips of darkly
  pigmented patients.

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Interpreting Pulse Oximetry

• Assess and treat the PATIENT not the oximeter!
• Use oximetry as an adjunct to patient assessment
  and treatment evaluation
• NEVER withhold oxygen if the patient ahs signs or
  symptoms of hypoxia or hypoxemia irregardless of
  oximetry readings!

45
continued

• Pulse oximetry measures oxygenation not
  ventilation
• Pulse oximetry does NOT indicate the removal of
  carbon dioxide from the blood!

46
Documentation

• Pulse oximetry is usually documented as SpO2
• Distinguishes non-invasive pulse oximetry from
  SaO2 determined by laboratory testing
• Document oximetry readings as frequently as other
  vital signs
• When oximetry reading is obtained before oxygen
  administration, designate the reading as room
  air

47
continued

• When oxygen administration is changed, document
  the evaluation of pulse oximetry
• When treatments provided could potentially affect
  respiration or ventilation, document pulse
  oximetry
• Spinal immobilization
• Shock position
• Fluid administration

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Summary

• As with all monitoring devices, the
  interpretation of information and response to
  that interpretation is the responsibility of a
  properly trained technician!

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References

• Bledsoe, B. et al. (2003). Essentials of
  paramedic care. Upper Saddle River, New Jersey
  Prentice Hall.
• Halstead, D., Progress in pulse oximetrya
  powerful tool for EMS providers. JEMS, 2001
  55-66.
• Henry, M., Stapleton, E. (1997). EMT prehospital
  care (2nd ed.). Philadelphia W.B. Saunders.
• Limmer, D., et al. (2001) Emergency Care (9th
  ed.). Upper Saddle River, New Jersey Prentice
  Hall.
• Porter, R., et al The fifth vital sign.
  Emergency, 1991 22(3) 127-130.
• Sanders, M., (2001). Paramedic textbook (rev.
  2nd ed.). St. Louis Mosby.
• Shade, B., et al. (2002). EMT intermediate
  textbook (2nd ed.). St. Louis Mosby.
• Cason, D., Pons, P. (1997) Paramedic field care
  a complaint approach. St. Louis Mosby.