Monitoring Pulse Oximetry
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Transcript Monitoring Pulse Oximetry
Monitoring Pulse
Oximetry
By the EMT-Basic
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
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
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
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
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
continued
Retractions
Upright or tripod position
Unusual anatomy changes
Hypoxemia
Decreased oxygen in arterial blood
Results in decreased cellular oxygenation
Anaerobic metabolism
Loss of cellular energy production
Hypoxemia Etiology
Inadequate External Respiration
Inadequate Oxygen Transport
Decreased on-loading of oxygen at pulmonary
capillaries
Decreased oxygen carrying capacity
Inadequate Internal Respiration
Decreased off-loading of oxygen at cellular
capillaries
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
Decreased oxygen available in the environment
Smoke inhalation
Toxic gas inhalation
High altitudes
Enclosures without outside ventilation
Inadequate mechanical ventilation
Pain
Rib fractures
Pleurisy
continued
Traumatic injuries
Open pneumothorax
Crushing injuries of the neck and chest
Increased intrathoracic pressures reducing ventilation
Hemothorax
Traumatic asphyxia
Crushing neck injuries
Tension pneumothorax
Loss of ability to change intrathoracic pressures
Blood in thoracic cavity reducing lung expansion
Flail Chest
Loss of ability to change intrathoracic pressures
continued
Other conditions
Upper Airway Obstruction
Epiglottitis
Croup
Airway Edema-anaphylaxis
Lower Airway Obstructions
Asthma
Airway Edema from inhalation of toxic substances
continued
Hypoventilation
Muscle Paralysis
Drug Overdose
Spinal injuries
Paralytic drug for intubation
Respiratory depressants
Brain Stem Injuries
Damage to the respiratory center
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
continued
Pulmonary emboli
Area of the lung is ventilated but hypoperfused
Loss of functional respiration membranes
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
Anemia
Poisoning
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
Low blood pressures result in inadequate oxygen carrying
capacity
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
Shock
Cellular environment is not conducive to off-loading
oxygen
Oxygen is not available due to massive peripheral
vasoconstriction or micro-emboli
Acid Base Imbalance
Lower than normal temperature
Poisoning
CO will reduce the oxygen available at the cellular level
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)
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
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
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
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
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
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)
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.
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 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
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
Use appropriate sized sensors
Active movement may cause erroneous readings
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
Conditions Affecting Accuracy
Patient conditions
Carboxyhemoglobin
Anemia
Hypovolemia/Hypotension
Hypothermia
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
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!
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!
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!
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!
Patient Environments
Ambient Light
Excessive Motion
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
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
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
continued
Skin pigmentation
Apply sensor to the fingertips of darkly pigmented
patients.
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!
continued
Pulse oximetry measures oxygenation not
ventilation
Pulse oximetry does NOT indicate the removal of
carbon dioxide from the blood!
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”
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
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.