Oxygen Saturation (Ambulatory) - CE

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    Oxygen Saturation (Ambulatory) - CE/NCPD


    Do not attach the oxygen sensor to an area that is edematous or if skin integrity is compromised. Do not attach the sensor to fingers or toes that are hypothermic.

    Do not place the sensor on an extremity with an electronic blood pressure cuff.


    Pulse oximetry is the noninvasive measurement of peripheral oxygen saturation (SpO2), which is the percentage of hemoglobin that is filled with oxygen. A pulse oximeter has a sensor with a light-emitting diode (LED) connected by a cable to an oximeter. The LED emits light wavelengths that are absorbed differently by oxygenated and deoxygenated hemoglobin molecules. The more hemoglobin saturated by oxygen, the higher the oxygen saturation.undefined#ref1">1 In general, the normal range for SpO2 is 95% to 100%.2 However, in patients with extensive respiratory disease (e.g., chronic obstructive pulmonary disease [COPD]), SpO2 greater than 90% may be an acceptable baseline.2

    Pulse oximetry is indicated for patients who are hypoxemic or who are at risk for impaired gas exchange. The measurement of SpO2 is simple and painless and has few of the risks associated with more invasive measurements of SpO2. Taking measurements with a digit or earlobe sensor requires a vascular, pulsatile area to detect the change in the sensor’s transmitted light. Conditions that decrease arterial blood flow (e.g., peripheral vascular disease, hypothermia, pharmacologic vasoconstrictors, hypotension, peripheral edema) affect accurate determination of SpO2 in these areas. For patients with decreased peripheral perfusion or diseases that cause tremors (e.g., Parkinson disease), a forehead reflectance sensor should be applied.

    Factors that affect light transmission (e.g., outside light sources, patient motion) also affect the measurement of SpO2. Direct sunlight or fluorescent lighting should be avoided when using an oximeter, or the sensor should be protected with an opaque covering or towel. Carbon monoxide in the blood, jaundice, and intravascular dyes can influence the light reflected from hemoglobin molecules. Levels of SpO2 measured in these conditions may be inaccurate. Other factors that affect accuracy of pulse oximetry readings include skin pigmentation and thickness, current tobacco use, and the presence of nail polish.3 If factors affect light transmission, oxygenation levels should be obtained through arterial blood gas sampling instead.1

    Different brands and types of sensors used to obtain pulse oximetry readings may show variable results. Accuracy of pulse oximetry readings decreases when saturation levels are less than 80%.2 In adults, reusable and disposable oximeter sensors should be applied to the earlobe, finger, toe, bridge of the nose, or forehead. Each sensor is designated for a different part of the body; the sensors are not interchangeable. A sensor for the finger or toe should not be used on the ear or nose.


    See Supplies tab at the top of the page.


    • Provide developmentally and culturally appropriate education based on the desire for knowledge, readiness to learn, and overall neurologic and psychosocial state.
    • Provide the patient with an explanation of the equipment and the procedure.
    • Teach the patient the signs and symptoms of hypoxemia (e.g., restlessness, confusion, shortness of breath, bluish-toned skin) and provide instructions on when to seek additional care.
    • Teach the patient about the effects of high-risk behaviors (e.g., cigarette smoking) on SpO2.
    • Encourage questions and answer them as they arise.


    1. Perform hand hygiene and don gloves. Don additional personal protective equipment (PPE) based on the patient’s need for isolation precautions or the risk of exposure to bodily fluids.
    2. Introduce yourself to the patient.
    3. Verify the correct patient using two identifiers.
    4. Explain the procedure and ensure that the patient agrees to treatment.
    5. Ensure that evaluation findings are communicated to the clinical team leader per the organization’s practice.
    6. Determine the need to monitor the patient’s oxygen saturation.
    7. Determine the patient’s risk factors for decreased SpO2.2
      1. Acute or chronic respiratory dysfunction
      2. Recovery from general anesthesia or conscious sedation
      3. Ventilator dependence
      4. Traumatic injury to the patient’s chest wall
      5. Changes in supplemental oxygen therapy
    8. Evaluate the patient for signs and symptoms of alterations in SpO2.2
      1. Altered respiratory rate, depth, or rhythm
      2. Adventitious breath sounds
      3. Cyanotic appearance of nail beds, lips, mucous membranes, or skin
      4. Restlessness, irritability, or confusion
      5. Decreased level of consciousness
      6. Labored or difficult breathing
    9. Evaluate the patient for factors that influence the measurement of SpO2.2
      1. Oxygen therapy
      2. Hemoglobin level
      3. Body temperature
      4. Medications (e.g., bronchodilators)
    10. Determine the patient’s previous baseline SpO2 measurement from the patient’s record, if available.
    11. Determine the most appropriate site (e.g., finger or toe, earlobe, nose, or forehead) for sensor placement by measuring capillary refill.2
      Rationale: A pulse oximetry sensor requires a pulsating vascular bed to identify hemoglobin molecules that absorb emitted light.
      Do not place the sensor on the same extremity as an electronic blood pressure (BP) cuff.
      Rationale: Blood flow to the finger is temporarily interrupted when the BP cuff inflates and can cause inaccurate SpO2 readings.
      1. Evaluate capillary refill. If it is prolonged (e.g., greater than 2 seconds), select an alternative site.
      2. Evaluate the circulation and skin integrity at the selected site. Ensure selected site is free of moisture, edema, and skin breakdown.
        Do not apply sensors to fingers or toes that are hypothermic.
      3. If the patient has tremors or is likely to move around, use an earlobe or forehead sensor.
      4. Select the patient’s forehead, ear, or bridge of nose if the patient has a history of vascular disease.
      5. Determine if the patient has a latex allergy or sensitivity if using a disposable sensor.
        Do not use adhesive sensors for patients with latex allergy or sensitivity.
      6. If using the patient’s finger, first remove nail polish with acetone or polish remover. Acrylic nails without nail polish do not interfere with SpO2 readings.
        Rationale: Nail polish may alter the SpO2 measurement.
    12. Evaluate the patient’s knowledge of the measurement of pulse oximetry and SpO2 readings.
    13. Obtain the correct sensor and pulse oximetry equipment for the selected site.
    14. Place the patient in a comfortable position. Provide privacy for the patient as needed.
    15. Instruct the patient to breathe normally and relax.
      Rationale: Normal breathing prevents large fluctuations in minute ventilation and possible changes in SpO2.
    16. Attach the sensor to the selected site per the manufacturer’s instructions for use (Figure 1)Figure 1.
      1. Make sure that the light source and the photodetector inside the sensor are aligned directly opposite each other.
      2. If using a clip-on finger sensor, inform the patient that it will feel like a clothespin on the finger but will not hurt.
      3. Use an adhesive dressing over or use a headband to apply the sensor to the patient’s forehead (as applicable).
        Use the patient’s forehead if the patient has poor circulation.
    17. When the sensor is in place, turn on the oximeter.
    18. Observe the pulse waveform and listen for the audible beep, if available.
      Rationale: The pulse waveform display and audible beep are proportional to the pulse and SpO2 value. Manually obtaining the pulse rate confirms oximeter accuracy.
    19. Leave the sensor in place until the pulse oximeter readout reaches a constant value (SpO2 reading) and the pulse display reaches full strength during each cardiac cycle.
      Use of oxygen therapy can affect SpO2 readings.
    20. Inform the patient that the pulse oximetry alarm will sound if the sensor falls off or the patient moves or removes the sensor.
    21. Correlate the pulse oximeter readings with the patient’s vital signs.
      1. Read the SpO2 on the digital display.
      2. Check the pulse oximeter readings in comparison to the patient’s pulse and respiratory rate, depth, and rhythm.
      3. If reading for intermittent SpO2 check, remove the sensor from the site and turn off the device.
    22. If continuous SpO2 monitoring is ordered:
      1. Verify SpO2 alarm limits and that volume is turned on.
      2. Determine the limits for the SpO2 and pulse rate based on the individual patient’s needs.
      3. Monitor the patient’s skin under the sensor.
      4. Monitor the skin every 2 hours and as needed.2
        Rationale: Skin irritation and breaks in skin integrity may cause pressure injury due to sensor tension and sensitivity.
    23. Clean reusable sensors between every patient use with 70% isopropyl alcohol solution or per the manufacturer’s instructions for use.2 If a reusable sensor was used, disinfect the device and return it to the designated storage location. If a disposable device was used, dispose of it in the appropriate waste receptacle.
    24. Discard supplies, remove PPE, and perform hand hygiene.
    25. Document the procedure in the patient’s record.


    • Patient’s SpO2 is greater than 95%.2
    • Strategies to improve the patient’s oxygenation levels (e.g., through breathing or repositioning) are effective without requiring invasive measurements.
    • Patient’s skin is free from signs of injury from adhesive or spring tension of the oximetry device.


    • SpO2 is less than 95%.2
    • Pulse waveform or intensity display is dampened or irregular.
    • Pulse rate on oximeter is less than the radial or apical pulse rate.
    • Skin shows signs of injury from adhesive or spring tension of the oximetry device.


    • Education
    • SpO2 level obtained
    • Signs and symptoms of oxygen desaturation
    • Unexpected outcomes and related interventions
    • Evaluation findings communicated to the clinical team leader per the organization’s practice


    • For infants, the sensor should be secured to the great toe, the cable secured to the foot, and the foot covered with a snugly fitting sock.
    • For children, the sensor should be secured on the index finger and the cable secured to the hand.
    • The earlobe and bridge-of-nose sensors should not be used for infants and children because of skin fragility.2


    1. Deacon, A.J., Pratt, O.W. (2021). Measurement of pulse oximetry, capnography and pH. Anesthesia and Intensive Care Medicine, 22(3), 185-189. doi:10.1016/j.mpaic.2021.01.005 (Level VI)
    2. Fetzer, S. (2019). Chapter 15: Vital signs. In P.A. Potter and others (Eds.), Essentials for Nursing Practice (9th ed., pp. 268-317). St. Louis: Elsevier.
    3. United States Food and Drug Administration (FDA). (2022). Pulse oximeter accuracy and limitations: FDA safety communication. Retrieved September 8, 2023, from (Level VII)

    Elsevier Skills Levels of Evidence

    • Level I - Systematic review of all relevant randomized controlled trials
    • Level II - At least one well-designed randomized controlled trial
    • Level III - Well-designed controlled trials without randomization
    • Level IV - Well-designed case-controlled or cohort studies
    • Level V - Descriptive or qualitative studies
    • Level VI - Single descriptive or qualitative study
    • Level VII - Authority opinion or expert committee reports

    Clinical Review: Kerrie L. Chambers, MSN, RN, CNOR, CNS-CP(E)

    Published: October 2023

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