Oxygen Saturation (Ambulatory) - CE
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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.
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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.
Do not apply sensors to fingers or toes that are hypothermic.
Do not use adhesive sensors for patients with latex allergy or sensitivity.
Rationale: Nail polish may alter the SpO2 measurement.
Rationale: Normal breathing prevents large fluctuations in minute ventilation and possible changes in SpO2.
Use the patient’s forehead if the patient has poor circulation.
Rationale: The pulse waveform display and audible beep are proportional to the pulse and SpO2 value. Manually obtaining the pulse rate confirms oximeter accuracy.
Use of oxygen therapy can affect SpO2 readings.
Rationale: Skin irritation and breaks in skin integrity may cause pressure injury due to sensor tension and sensitivity.
Clinical Review: Kerrie L. Chambers, MSN, RN, CNOR, CNS-CP(E)
Published: October 2023
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