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Monitoring Pulse Oximetry. By the EMT-Basic. Objectives. Understand the Indiana Regulations relative to monitoring pulse oximetry by the EMT-B/A Review the signs and symptoms of respiratory compromise Understand the importance of adequate tissue perfusion

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  • Understand the Indiana Regulations relative to monitoring pulse oximetry by the EMT-B/A
  • Review the signs and symptoms of respiratory compromise
  • Understand the importance of adequate tissue perfusion
  • Define hypoxia and describe the clinical signs and symptoms
  • 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
  • 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
kansas regulations
Kansas Regulations
  • Indiana EMS Regs:
    • 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
respiratory compromise
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
  • Retractions
  • Upright or tripod position
  • Unusual anatomy changes
  • Decreased oxygen in arterial blood
    • Results in decreased cellular oxygenation
    • Anaerobic metabolism
    • Loss of cellular energy production
hypoxemia etiology
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
external respiration
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
inadequate external respiration
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
  • 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
  • Other conditions
    • Upper Airway Obstruction
      • Epiglottitis
      • Croup
      • Airway Edema-anaphylaxis
    • Lower Airway Obstructions
      • Asthma
      • Airway Edema from inhalation of toxic substances
  • Hypoventilation
    • Muscle Paralysis
      • Spinal injuries
      • Paralytic drug for intubation
    • Drug Overdose
      • Respiratory depressants
    • Brain Stem Injuries
      • Damage to the respiratory center
  • 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
  • Pulmonary emboli
    • Area of the lung is ventilated but hypoperfused
    • Loss of functional respiration membranes
oxygen transport
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
inadequate oxygen transport
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
internal respiration
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
inadequate internal respiration
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
signs and symptoms of hypoxemia
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)
  • 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
oxygen saturation
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
  • 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
spo2 and pao2
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
  • 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
  • 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)
  • 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.
patient assessment
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
pulse oximetry monitoring
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 patient’s oxygenation and monitoring treatment interventions
  • Initiate pulse oximetry immediately prior to or concurrently with oxygen administration
continuous monitoring
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
  • 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
conditions affecting accuracy
Conditions Affecting Accuracy
  • Patient conditions
    • Carboxyhemoglobin
    • Anemia
    • Hypovolemia/Hypotension
    • Hypothermia
  • 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
  • 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!

  • 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!

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!

  • 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!

patient environments
Patient Environments
  • Ambient Light
  • Excessive Motion
ambient lighting
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
excessive motion
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
other concerns
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
  • Skin pigmentation
    • Apply sensor to the fingertips of darkly pigmented patients.
interpreting pulse oximetry
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!

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

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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Halstead, D., Progress in pulse oximetry—a 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.