Monitoring Pulse
Oximetry
By the EMT-Basic
Objectives
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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
continued
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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
continued
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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

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
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On line medical control or written protocols
Complete a course of instruction
Respiratory Compromise
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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
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continued
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Retractions
Upright or tripod position
Unusual anatomy changes
Hypoxemia
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Decreased oxygen in arterial blood
Results in decreased cellular oxygenation
 Anaerobic metabolism
 Loss of cellular energy production
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Hypoxemia Etiology
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Inadequate External Respiration
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Inadequate Oxygen Transport
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Decreased on-loading of oxygen at pulmonary
capillaries
Decreased oxygen carrying capacity
Inadequate Internal Respiration
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Decreased off-loading of oxygen at cellular
capillaries
External Respiration
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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
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Decreased oxygen available in the environment
Smoke inhalation
 Toxic gas inhalation
 High altitudes
 Enclosures without outside ventilation
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Inadequate mechanical ventilation
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Pain
Rib fractures
 Pleurisy
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continued
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Traumatic injuries
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Open pneumothorax
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Crushing injuries of the neck and chest
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Increased intrathoracic pressures reducing ventilation
Hemothorax
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Traumatic asphyxia
Crushing neck injuries
Tension pneumothorax
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Loss of ability to change intrathoracic pressures
Blood in thoracic cavity reducing lung expansion
Flail Chest
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Loss of ability to change intrathoracic pressures
continued
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Other conditions
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Upper Airway Obstruction
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Epiglottitis
Croup
Airway Edema-anaphylaxis
Lower Airway Obstructions
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Asthma
Airway Edema from inhalation of toxic substances
continued
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Hypoventilation
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Muscle Paralysis
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Drug Overdose
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Spinal injuries
Paralytic drug for intubation
Respiratory depressants
Brain Stem Injuries
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Damage to the respiratory center
continued
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Inadequate oxygen diffusion
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Pulmonary edema
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Fluid between alveoli and capillaries inhibit diffusion
Pneumonia
Consolidation reduces surface area of respiratory
membranes
 Reduces the ventilation-perfusion ratio
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COPD
Air trapping in alveoli
 Loss of surface area of respiratory membranes
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continued
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Pulmonary emboli
Area of the lung is ventilated but hypoperfused
 Loss of functional respiration membranes
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Oxygen Transport
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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
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Anemia
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Poisoning
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Reduces red blood cells reduce oxygen carrying capacity
Inadequate hemoglobin results in the loss of oxygen
saturation
Carbon monoxide on-loads on the hemoglobin more readily
preventing oxygen saturation and oxygen carrying capacity
Shock
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Low blood pressures result in inadequate oxygen carrying
capacity
Internal Respiration
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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
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Shock
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Cellular environment is not conducive to off-loading
oxygen
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Oxygen is not available due to massive peripheral
vasoconstriction or micro-emboli
Acid Base Imbalance
Lower than normal temperature
Poisoning
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CO will reduce the oxygen available at the cellular level
Signs and Symptoms of Hypoxemia
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Restlessness
Altered or deteriorating mental status
Increased or decreased pulse rates
Increased or decrease respiratory rates
Decreased oxygen oximetry readings
Cyanosis (late sign)
Pathophysiology
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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
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Oxygen Saturation
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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
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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
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SpO2 and PaO2
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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
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PaO2 indicates the oxygen dissolved in the
plasma
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Measured in ABGs
continued
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Normal PaO2 is 80-100 mmHg
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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
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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)
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continued
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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
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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
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Pulse oximetry monitoring is NOT intended to
replace any part of the patient assessment
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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
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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
Pediatrics
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Use appropriate sized sensors
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Active movement may cause erroneous readings
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Adult sensors may be used on arms or feet
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
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Conditions Affecting Accuracy
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Patient conditions
Carboxyhemoglobin
 Anemia
 Hypovolemia/Hypotension
 Hypothermia
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Carboxyhemoglobin
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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
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Carboxyhemoglobin can not be distinguished
from oxyhemoglobin by pulse oximetry
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Erroneously high reading may present
continued
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Suspect the presence of carboxyhemoglobin in
patient with:
Smoke inhalation
 Intentional and accidental CO poisoning
 Heavy cigarette smoking
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Treat carboxyhemoglobin with high flow
oxygen irregardless of the pulse oximetry
reading!
Anemia
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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
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Anemic patients require high levels of oxygen
to compensate for low oxygen carrying
capacities!
Hypovolemia/Hypotension
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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!
Hypothermia
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Severe peripheral vasoconstriction may prevent
oximetry detection
Shivering may result in erroneous oximetry
motion
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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
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Ambient Light
Excessive Motion
Ambient Lighting
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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
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Shielding the sensor by covering the extremity is
acceptable
Excessive Motion
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New technology filters out most motion artifact
Always compare the palpable pulse rate with the
pulse rate indicated on the pulse oximetry
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If they do not coincide, reading must be considered
inaccurate
Other Concerns
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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
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Skin pigmentation
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Apply sensor to the fingertips of darkly pigmented
patients.
Interpreting Pulse Oximetry
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Assess and treat the PATIENT not the
oximeter!
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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!
continued
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Pulse oximetry measures oxygenation not
ventilation
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Pulse oximetry does NOT indicate the removal of
carbon dioxide from the blood!
Documentation
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Pulse oximetry is usually documented as SpO2
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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”
continued
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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!
References
Bledsoe, B. et al. (2003). Essentials of paramedic care. Upper Saddle River, New Jersey:
Prentice Hall.
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.