Pulse Oximetry - 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

Consult the manufacturer’s instructions for the designated site for placement of the sensor.

Do not place a sensor on an extremity that has an electronic blood pressure cuff because blood flow to the fingers will be temporarily interrupted when the cuff inflates, causing an inaccurate reading that can trigger alarms.

Conditions that decrease arterial blood flow, such as peripheral vascular disease, hypothermia, hypotension, and peripheral edema, affect the accuracy of oxygen saturation readings. Pharmacologic vasoconstrictors also decrease arterial blood flow.

Pulse oximeters overestimate oxygen saturation in patients with acute respiratory failure, chronic bronchitis, and emphysema; however, monitoring trends is helpful. If a pulse oximeter reading is questionable, obtain arterial blood gas (ABG) values to determine oxygen saturation.^{undefined#ref2">2}

OVERVIEW

Pulse oximetry is the noninvasive measurement of arterial blood oxygen saturation (the percentage of hemoglobin saturated with oxygen). This measurement is indicated for patients who are at risk of inadequate oxygenation.

A pulse oximeter is a probe 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.³ In adults, reusable and disposable oximeter probes may be applied to the earlobe, finger, toe, bridge of the nose, or forehead (Box 1) Box 1 .

The measurement of oxygen saturation is simple and painless and has only a few of the risks associated with more invasive measurements of oxygen saturation, such as ABG sampling. A vascular, pulsatile area is needed to detect the change in the transmitted light when making measurements with a finger. A forehead reflectance sensor can be used for patients with decreased peripheral perfusion.

Factors that affect light transmission, such as outside light sources or patient motion, also affect the measurement of oxygen saturation. Direct sunlight or fluorescent lighting should be avoided when using an oximeter. Carbon monoxide in the blood, jaundice, and intravascular dyes can influence the light reflected from hemoglobin molecules, causing falsely high results. If factors that affect light transmission are present, oxygenation levels should be obtained through an ABG sample.⁵

Some limitations may impact the accuracy of pulse oximeters, such as poor circulation; dark skin pigmentation; thick skin; current use of nicotine-containing products; cool skin; dark fingernail polish; and long, artificial nails. The pulse oximeter reading should not be used alone to determine the state of health.²

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 and family the significance of monitoring peripheral oxygen saturation (SpO₂).
Teach the patient and family the signs and symptoms of hypoxemia, including headache, somnolence, confusion, dusky color, shortness of breath, and dyspnea.
Explain the effects of high-risk behaviors, such as cigarette smoking, on oxygen saturation.
Encourage questions and answer them as they arise.

ASSESSMENT AND PREPARATION

Assessment

Determine if the patient or family has health literacy needs or requires tools or assistance to effectively communicate. Be sure these needs can be met without compromising safety.
Review the patient’s and family’s previous experience and knowledge of pulse oximetry and understanding of the care to be provided.
Find out the need to measure the patient’s oxygen saturation.
1. Assess the patient for risk factors for decreased oxygen saturation.
  1. Acute or chronic compromised respiratory function
  2. Recovery from general anesthesia or moderate sedation
  3. Continuous sedation or paralytic therapy
  4. Use of opioid pain medications
  5. Traumatic injury to the chest wall with or without collapse of underlying lung tissue
  6. Ventilator dependence
  7. Changes in supplemental oxygen therapy
  8. Activity intolerance
  9. Obstructive sleep apnea
2. Assess the patient for signs and symptoms of alterations in oxygen saturation.
  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. Reduced level of consciousness
  6. Labored or difficulty breathing
Assess the patient for factors that influence the measurement of SpO₂.
1. Oxygen therapy
2. Respiratory therapy, such as postural drainage and percussion
3. Hemoglobin level
4. Hypotension
5. Temperature
6. Medications, such as bronchodilators
Review the patient’s record for the prescribing practitioner’s order for measuring SpO₂.
Find out the previous baseline SpO₂ (if available) from the patient’s record.
Find out the most appropriate patient-specific site (e.g., finger, earlobe, bridge of the nose, forehead) for sensor probe placement.
1. If capillary refill at the chosen site is prolonged, select an alternate site.
2. Make sure that the site is dry and has adequate local circulation.
3. If the patient has tremors or is likely to move, use the earlobe or forehead. Earlobe probe sensors may be used in patients with Parkinson disease.
4. If the patient has obesity, a clip-on probe may not fit properly; obtain a disposable (tape-on) probe.
  Do not place a reusable clip-on finger sensor on the thumb; it is not designed for the thumb. Do not attach the probe to the finger, ear, or bridge of nose if the area is edematous or skin integrity is compromised. Do not use bridge of the nose sensors for infants or toddlers because of their skin fragility. Do not attach a sensor to fingers that are hypothermic.
  
  Select the bridge of the nose as the sensor site if an adult has a history of peripheral vascular disease.

Preparation

Get the appropriate equipment and place it at the patient’s bedside.
If using the finger site, remove fingernail polish with acetone or polish remover.
Clean the probe, if it is not disposable.

PROCEDURE

Position the patient in a stable position that limits excessive movement. If the finger is the monitoring site, support the upper extremity.
Tell the patient to breathe normally.
Tell the patient that the clip-on probe will feel like a clothespin on the finger but will not hurt. Then attach the sensor to the monitoring site (Figure 1).
When the sensor is in place, turn on the oximeter.
Observe the pulse waveform or intensity display and listen for the audible beep, if available.
Correlate the oximeter pulse rate with the patient’s radial pulse and apical pulse simultaneously. If the values are different, reevaluate the oximeter probe placement and reassess the pulse rates.
Read the SpO₂ on the digital display. Leave the sensor in place until the oximeter readout reaches a constant value and the pulse display reaches full strength during each cardiac cycle.
Inform the patient that the oximeter alarm will sound if the sensor falls off or if the patient moves it.
If intermittently checking or spot-checking SpO₂, remove the probe, turn the oximeter power off, clean the probe with an alcohol pad, and store the sensor in an appropriate location.
For continuous monitoring, make sure that the alarms on the oximeter are turned on.
Discuss the findings with the patient, as needed.

MONITORING AND CARE

If measuring a patient’s oxygen saturation for the first time, establish the SpO₂ as the baseline. Record whether oxygen therapy was used when determining the baseline.
Compare the current SpO₂ with the patient’s previous baseline and acceptable SpO₂. Notify the authorized practitioner of abnormal findings.⁴
Assess the patient’s skin integrity under the probe as needed, based on the patient’s peripheral circulation. Relocate the sensor if skin integrity is altered or tissue perfusion is compromised.
1. If using a reusable clip-on sensor, apply and remove it each time oxygen saturation is assessed. If continuous monitoring is needed, assess the skin under the oximetry sensor for signs of redness.
2. If using an adhesive sensor, assess the skin around the sensor for signs of irritation. Change the sensor in accordance with the manufacturer’s instructions or when clinically indicated.
If monitoring oxygen saturation continuously, verify that the SpO₂ alarms are on and set according to the patient’s clinical condition and the prescribing practitioner’s order.
Make sure that the probe site is changed frequently to prevent any loss of skin integrity from pressure or friction.
Observe the patient for signs and symptoms of pain. If pain is suspected, report it to the authorized practitioner.

EXPECTED OUTCOMES

Patient’s SpO₂ is greater than 95%¹ or it improves to a satisfactory level for the patient’s condition.
Patient’s oxygenation therapies are adjusted without requiring invasive assessment measures.
Patient’s skin is free from signs of injury from adhesive or spring tension of the oximetry device.

UNEXPECTED OUTCOMES

SpO₂ is less than 95%¹ or it is below the patient’s baseline.
Pulse waveform or intensity display is dampened or irregular.
Pulse rate indicated on oximeter is less than radial or apical pulse rate.
Results are inconsistent with the patient’s clinical condition.
Pulse oximetry reading is unobtainable.
Skin shows signs of injury from adhesive or spring tension of the oximetry device.

DOCUMENTATION

SpO₂ on vital sign flow sheet
Device type and amount of oxygen therapy in use
Measurement of oxygen saturation after administration of specific therapies
Signs or symptoms of oxygen desaturation
Abnormal findings
Education
Unexpected outcomes and related interventions

PEDIATRIC CONSIDERATIONS

For infants, secure the sensor to the great toe, secure the cable to the foot (Figure 2), and cover the foot with a snugly fitting sock.
For children, secure the sensor on the index finger and secure the cable to the hand.
Cover sensors when used during phototherapy or with radiant warmers. Heat and light sources affect sensors.
Do not use earlobe and bridge-of-nose sensors for infants and toddlers because of skin fragility.
Consider using special skin protection products for neonates before placing pulse oximetry sensors. Adhesive medical devices can cause skin stripping, tears, or blisters in newborns.

OLDER ADULT CONSIDERATIONS

Identifying an acceptable pulse oximeter probe site is difficult in older adults because of the likelihood of peripheral vascular disease, cold-induced vasoconstriction, and anemia.
Older adults require more frequent assessment of the skin under the sensor site because of tissue fragility and decreased elasticity caused by aging.

REFERENCES

American Heart Association (AHA). (2020). Part 3: High-performance teams. In ACLS: Advanced cardiovascular life support: Provider manual (17th ed., pp. 91-163). Dallas: Author.
American Lung Association. (2024). Pulse oximetry. Retrieved July 28, 2025, from https://www.lung.org/lung-health-diseases/lung-procedures-and-tests/pulse-oximetry
Brashers, V.L., Turner, K.C. (2026). Chapter 28: Structure and function of the pulmonary system. In S.E. Huether, K.L. McCance, V.L. Brashers (Eds.), Understanding pathophysiology (8th ed., pp. 670-683). St. Louis: Elsevier.
Perry, A.G. (2025). Chapter 5: Vital signs. In A.G. Perry and others (Eds.), Clinical nursing skills & techniques (11th ed., pp. 70-109). St. Louis: Elsevier.
Shaikh, H., Littleton, S., Laghi, F. (2025). Chapter 19: Analysis and monitoring of gas exchange. In J.K. Stoller and others (Eds.), Egan’s fundamentals of respiratory care (13th ed., pp. 361-389). St. Louis: Elsevier.

ADDITIONAL READINGS

National Health Service (NHS). (2022). Guidelines on oxygen and oximetry. Retrieved July 28, 2025, from https://handbook.ggcmedicines.org.uk/guidelines/respiratory-system/guidelines-on-oxygen-and-oximetry/

Adapted from Perry, A.G. and others (Eds.). (2025). Clinical nursing skills & techniques (11th ed.). St. Louis: Elsevier.

Clinical Review: Justin J. Milici, MSN, RN, CEN, CPEN, CPN, TCRN, CCRN, FAEN

Published: September 2025