Oxygen Saturation (Ambulatory) - CE

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.

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

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%.^1,3 A consistent SpO₂ of less than 95% should be investigated.² SpO₂ of less than 92% signifies developing hypoxemia.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 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.² 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.² 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 (Box 1). 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

• 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.
• Explain to the patient that the procedure does not cause any pain or discomfort.
• Encourage questions and answer them as they arise.

PROCEDURE

1. Perform hand hygiene and don gloves. Don appropriate 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 SpO₂ measurement.
5. Ensure that evaluation findings are communicated to the clinical team leader per the organization’s practice.
6. Determine the patient’s risk factors for decreased SpO₂.
   1. Acute or chronic respiratory dysfunction
   2. Opioid medications
   3. Injury to the chest wall
   4. Sleep apnea
7. Evaluate the patient for signs and symptoms of alterations in SpO₂.
   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 bizarre behavior
   5. Decreased level of consciousness
   6. Labored breathing or difficulty breathing
8. Evaluate 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)
   5. Parkinson disease or other diseases that cause tremors
9. Determine the most appropriate site (i.e., finger or toe, 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 artificial reading that can trigger alarms.

   1. Evaluate capillary refill. If it is prolonged, select an alternative site.
   2. Evaluate 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 oxygen sensor to fingers or toes that are hypothermic.

   3. Evaluate 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 forehead sensor.
   5. If the patient is obese and the clip-on sensor will not fit properly, use a disposable sensor.
10. Obtain the correct sensor for the selected site and prepare the site as appropriate.
    1. Consult the manufacturer’s instructions for use 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.

11. Place the patient in a comfortable position. If using a finger as the site, position the hand so the finger is clear of obstructions.

    Rationale: Correct hand positioning ensures sensor position and decreases motion artifact that interferes with SpO₂ determination.

12. Instruct the patient to breathe normally.

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

13. If using a clip-on finger sensor, inform the patient that it will feel like a clothespin on the finger but will not hurt.
14. Attach the sensor to the selected site (Figure 1). Make sure that the light source and the photodetector inside the sensor are aligned directly opposite each other.
15. When the sensor is in place, turn on the oximeter.
16. 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.

17. Correlate the oximeter pulse rate with the patient’s radial pulse.
18. If simultaneously measuring oximeter pulse rate, radial pulse, and apical pulse and each is different, reevaluate the oximeter sensor placement, reposition the sensor if necessary, and obtain the rates again.
19. If performing intermittent 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 site and turn off the device.
    3. 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.
20. Discard supplies, remove PPE, and perform hand hygiene.
21. Document the procedure in the patient’s record.

EXPECTED OUTCOMES

• Patient’s SpO₂ is greater than 92%.³
• 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.

UNEXPECTED OUTCOMES

• SpO₂ is less than 92%.³
• 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 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

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 toddlers because of skin fragility.

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.
• A sensor designed for the forehead or earlobe should be considered. Peripheral circulation may be compromised in the older adult, resulting in distorted pulse oximetry values.

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 (Level VI)
2. United States Food and Drug Administration (FDA). (2022). Pulse oximeter accuracy and limitations: FDA safety communication. Retrieved August 1, 2022, from https://www.fda.gov/medical-devices/safety-communications/pulse-oximeter-accuracy-and-limitations-fda-safety-communication (Level VII)
3. Yale Medicine. (n.d.) Pulse oximetry. Retrieved August 1, 2022, from https://www.yalemedicine.org/conditions/pulse-oximetry

ADDITIONAL READINGS

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 (classic reference)* (Level VII)

*In these skills, a “classic” reference is a widely cited, standard work of established excellence that significantly affects current practice and may also represent the foundational research for practice.

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