Oxygen Saturation (Ambulatory) - CE/NCPD

The content in Clinical Skills is evidence based and intended to be a guide to clinical practice. Always follow your organization’s practice.

ALERT

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.

OVERVIEW

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 finger, toe, 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 blood circulation to the extremities or diseases that cause tremors (e.g., Parkinson disease), a forehead 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 a covering that blocks light or towel. Carbon monoxide in the blood, jaundice, and intravascular dyes can affect the light in the hemoglobin molecules, causing inaccurate SpO₂ levels. Other factors that affect accuracy of pulse oximetry readings include color of the skin 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.

SUPPLIES

See Supplies tab at the top of the page.

EDUCATION

• Give developmentally and culturally appropriate education based on the desire for knowledge, readiness to learn, preferred learning style, and overall neurologic and psychosocial state.
• Teach the patient about the equipment and how it works.
• 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.

PROCEDURE

1. Determine if the patient has health literacy needs or requires tools or assistance to effectively communicate. Be sure these needs can be met without compromising safety.
2. Review the patient’s previous experience and knowledge of oxygen saturation monitoring and understanding of the care to be provided.
3. Determine the need to monitor the patient’s oxygen saturation.
4. 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
5. 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
6. 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)
7. Determine the patient’s previous baseline SpO₂ measurement from the patient’s record, if available.
8. Clean hands and put on appropriate personal protective equipment (PPE) based on the risk of exposure to body fluids or infection precautions.
9. 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.

10. Get the correct sensor and pulse oximetry equipment for the selected site.
11. Ask the patient to breathe normally and relax.

    Rationale: Normal breathing prevents large fluctuations in minute ventilation and possible changes in SpO₂.

12. Attach the sensor to the selected site per the manufacturer’s instructions for use (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.

13. When the sensor is in place, turn on the oximeter.
14. 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.

15. 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.

16. Inform the patient that the pulse oximetry alarm will sound if the sensor falls off or the patient moves or removes the sensor.
17. 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.
18. 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 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.

19. 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.

EXPECTED OUTCOMES

• Patient’s SpO₂ is greater than 95%.²

UNEXPECTED OUTCOMES

• SpO₂ is less than 95%.²

DOCUMENTATION

• Education
• SpO₂ level obtained
• Signs and symptoms of oxygen desaturation, as applicable
• Unexpected outcomes and related interventions

PEDIATRIC CONSIDERATIONS

• 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

REFERENCES

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
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). (2025). Pulse oximeters. Retrieved May 13, 2025, from https://www.fda.gov/medical-devices/products-and-medical-procedures/pulse-oximeters

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

Published: July 2025