Pulse Oximetry - CE/NCPD

ALERT

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

Do not attach the sensor to a finger, an earlobe, or the bridge of the nose if the area is edematous or if skin integrity is compromised. Do not attach the sensor to fingers that are hypothermic.

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

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#ref1">1}

OVERVIEW

Pulse oximetry is the noninvasive measurement of peripheral oxygen saturation (SpO₂), which is expressed as 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.⁴ In general, the normal range for SpO₂ is 95% to 99%.² A consistent SpO₂ of less than 95% should be investigated, and an SpO₂ of 90% signifies developing hypoxemia.² Pulse oximetry devices have a margin of error of 3% to 4%, especially in critically ill patients and newborns.³

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 oxygen saturation (e.g., ABG sampling). 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 oxygen saturation in these areas. For patients with decreased peripheral perfusion, 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. If factors affect light transmission, oxygenation levels should be obtained through ABG sampling instead.⁴

In adults, reusable and disposable oximeter sensors should be applied to the earlobe, finger, toe, bridge of the nose, or forehead (Box 1) Box 1 . Each sensor is designated for a different part of the body; the sensors are not interchangeable, so a sensor for the finger (Figure 1) or toe should not be used on the ear or nose.

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.¹

SUPPLIES

See Supplies tab at the top of the page.

EDUCATION

Provide developmentally and culturally appropriate education based on the desire for knowledge, readiness to learn, and overall neurologic and psychosocial state.
Provide the patient and family with an explanation of the equipment and the procedure.
Teach the patient and family the signs and symptoms of hypoxemia: restlessness, confusion, dusky color, shortness of breath, and dyspnea.
Teach the patient and family about the effects of high-risk behaviors (e.g., cigarette smoking, vaping) on oxygen saturation.
Explain to the patient and family that the procedure does not cause any pain or discomfort.
Encourage questions and answer them as they arise.

ASSESSMENT AND PREPARATION

Assessment

Perform hand hygiene before patient contact.
Introduce yourself to the patient.
Verify the correct patient using two identifiers.
Assess the patient for risk factors for decreased oxygen saturation.
1. Acute or chronic respiratory dysfunction
2. Recovery from general anesthesia or procedural sedation
3. Sedation or paralytic therapy
4. Use of opioid medications
5. Injury to the chest wall
6. Ventilator dependence
7. Sleep apnea
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, and skin
4. Restlessness, irritability, confusion, or unusual behavior
5. Decreased level of consciousness
6. Labored breathing or difficulty breathing
Assess the patient for factors that influence the measurement of SpO₂.
1. Oxygen therapy
2. Chest physiotherapy (e.g., postural drainage, percussion)
3. Hemoglobin level
4. Medications (e.g., bronchodilators)

Preparation

Obtain the previous baseline SpO₂ (if available) from the patient’s record.

PROCEDURE

Perform hand hygiene. Don appropriate personal protective equipment (PPE) based on the patient’s need for isolation precautions or the risk of exposure to bodily fluids.
Verify the correct patient using two identifiers.
Explain the procedure and ensure that the patient agrees to treatment.
Determine the most appropriate site (i.e., finger or toe [digit], earlobe, bridge of nose, or forehead) for sensor placement.
Do not place a reusable clip-on finger sensor on the thumb; it is not designed for the thumb.

Do not place the sensor on the same extremity as an electronic blood pressure cuff; blood flow is interrupted when the blood pressure cuff inflates, causing an inaccurate reading that can trigger alarms.
1. Assess capillary refill. If capillary refill is prolonged, select an alternative site.
2. Assess the temperature of the site. If the site is cold to the touch, select an alternative site.
  Rationale: Peripheral vasoconstriction alters SpO₂.
  
  Do not attach the sensor to fingers or toes that are hypothermic.
3. Assess the skin integrity of the site. If the site is edematous or skin integrity is compromised, select an alternative site.
  Rationale: The site must have adequate local circulation and be free of moisture.
4. If the patient has tremors or is likely to move, use an earlobe or a forehead sensor.
5. If the patient has obesity, use a disposable sensor.
  Rationale: If the patient has obesity, a clip-on sensor may not fit properly.
Select the appropriate sensor for the site and prepare the site as appropriate.
1. Consult the manufacturer’s instructions for the designated site placement of the sensor.
  Place the sensor on its designated site only; otherwise, an erroneous reading may be obtained.
2. If using the patient’s finger, first remove nail polish with acetone or polish remover.
  Rationale: Opaque coatings decrease light transmission; nail polish containing blue pigment absorbs light emissions and alters the SpO₂ measurement.
Position the patient comfortably. If using a finger as the monitoring site, position the hand so the finger is clear of obstructions, such as blankets and straps.
Rationale: Correct hand positioning ensures sensor position and decreases motion artifact that interferes with SpO₂ determination.
Instruct the patient to breathe normally.
Rationale: Normal breathing prevents large fluctuations in minute ventilation and possible changes in SpO₂.
If using a clip-on finger sensor, inform the patient that the sensor feels like a clothespin on the finger but does not hurt.
Attach the sensor to the selected monitoring site (Figure 1). Make sure the light source and the photodetector inside the sensor are aligned directly opposite each other.
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.
Rationale: The pulse waveform display and audible beep are proportional to the pulse and SpO₂ value. Manually obtaining the pulse rate confirms oximeter accuracy.
Correlate the oximeter pulse rate with the patient’s radial pulse.
If simultaneously measuring oximeter pulse rate, radial pulse, and apical pulse and they are different, reevaluate the oximeter sensor placement and reassess the pulse rates. If necessary, reposition the sensor and reassess the rates.
If performing intermittent monitoring (spot-checking) of SpO₂, leave the sensor in place until the oximeter readout reaches a constant value and the pulse display reaches full strength during each cardiac cycle.
1. Read the SpO₂ on the digital display.
2. Remove the sensor from the patient’s finger and turn off the device.
3. Disinfect the device and return it to the designated storage location.
If continuously monitoring SpO₂, adjust the alarm limits and activate the alarms. Inform the patient that the oximeter alarm will sound if the sensor falls off or if the patient moves the sensor.
Discard supplies, remove PPE, and perform hand hygiene.
Document the procedure in the patient’s record.

MONITORING AND CARE

If assessing the patient’s SpO₂ for the first time, establish it as baseline if it is within an acceptable range.
Compare the current SpO₂ with the patient’s previous baseline and acceptable SpO₂. Notify the practitioner of abnormal findings.
Assess skin integrity under or around the sensor site.
1. If using a reusable clip-on sensor, apply and remove it each time SpO₂ is assessed.³ If continuous monitoring is needed, assess the skin under the oximetry sensor for signs of redness.
  Rationale: Spring tension of the sensor can lead to pressure ulcer development under the sensor.
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.
  Rationale: Adhesives can cause injury to the skin by damaging skin cells and detaching the outer layers of skin from underlying layers.³
Assess, treat, and reassess pain.

EXPECTED OUTCOMES

Patient’s SpO₂ is greater than 92%,² 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 92%² or it is below the patient’s baseline.
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.

DOCUMENTATION

Education
SpO₂
Type and amount of oxygen therapy (if applicable)
Signs and symptoms of oxygen desaturation
Unexpected outcomes and related interventions
Pain assessment and management

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 sensor 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 because of tissue fragility and decreased elasticity.
Consider using a sensor designed for the forehead or earlobe. Peripheral circulation may be compromised in older adult patients, resulting in inaccurate pulse oximetry values.

HOME CARE CONSIDERATIONS

Use pulse oximetry in home care to monitor oxygen therapy or changes in oxygen therapy.
Teach the patient and family proper use of pulse oximetry devices.
Older adults may have limited dexterity in applying pulse oximetry devices. Teach modifications to the patient and family as needed.

REFERENCES

American Lung Association. (2024). Pulse oximetry. Retrieved July 3, 2024, from https://www.lung.org/lung-health-diseases/lung-procedures-and-tests/pulse-oximetry
Jubran, A. (2015). Pulse oximetry. Critical Care, 19(1), 272. doi:10.1186/s13054-015-0984-8
Nitzan, M., Romem, A., Koppel, R. (2014). Pulse oximetry: Fundamentals and technology update. Medical Devices (Auckland), 7, 231-239. doi:10.2147/MDER.S47319
Pretto, J.J. and others. (2014). Clinical use of pulse oximetry: Official guidelines from the Thoracic Society of Australia and New Zealand. Respirology, 19(1), 38-46. doi:10.1111/resp.12204

ADDITIONAL READINGS

National Health Service (NHS). (2022). Guidelines on oxygen and oximetry. Retrieved July 3, 2024, from https://handbook.ggcmedicines.org.uk/guidelines/respiratory-system/guidelines-on-oxygen-and-oximetry

Siegel, B.K., Heuer, A.J., Kallet, R.H. (2021). Chapter 19: Analysis and monitoring of gas exchange. In R.M. Kacmarek, J.K. Stoller, A.J. Heuer (Eds.), Egan’s fundamentals of respiratory care (12th ed., pp. 368-394). St. Louis: Elsevier.

Adapted from Perry, A.G. and others (Eds.). (2022). Clinical nursing skills & techniques (10th ed.). St. Louis: Elsevier.

Clinical Review: Suzanne M. Casey, MSN-Ed, RN

Published: August 2024