Pulse Oximetry (SpO2)
Pulse oximetry is a noninvasive method of measuring the oxygen saturation (SpO2) of the blood using a small clip-on sensor placed on the fingertip, toe, or earlobe. The normal SpO2 range is 95-100%, and readings below 90% indicate a medical emergency requiring immediate reporting to the nurse.
Exam Tip
SpO2 normal = 95-100%. Below 90% = emergency, report immediately. Remove nail polish. Cold fingers give inaccurate readings. CNA can measure but CANNOT adjust oxygen flow. Signs of low oxygen: confusion, restlessness, cyanosis (blue lips/nailbeds).
What Is Pulse Oximetry?
Pulse oximetry uses a device called a pulse oximeter to measure how much oxygen is being carried by the hemoglobin in red blood cells. It works by shining red and infrared light through the tissue and measuring how much light is absorbed. The result is displayed as SpO2 (peripheral oxygen saturation) as a percentage.
Normal and Abnormal SpO2 Ranges
| SpO2 Reading | Interpretation | Action |
|---|---|---|
| 95-100% | Normal | Continue monitoring as ordered |
| 91-94% | Below normal | Report to nurse promptly |
| 90% or below | Critically low (hypoxemia) | Report to nurse IMMEDIATELY |
| Below 85% | Severe hypoxemia | Emergency; may indicate respiratory failure |
How to Measure SpO2
- Select the appropriate site (fingertip is most common)
- Ensure the site is clean and dry
- Remove nail polish or acrylic nails if on the finger (they interfere with readings)
- Place the sensor clip on the finger (light source on top, detector on bottom)
- Wait for a stable reading (usually 10-30 seconds)
- Record the reading and report abnormal values
Factors That Affect Accuracy
| Factor | Effect |
|---|---|
| Nail polish/acrylic nails | Blocks light, gives falsely low reading |
| Poor circulation | Cold fingers, low blood pressure = inaccurate |
| Movement/shivering | Causes erratic readings |
| Dark skin pigmentation | May give slightly higher readings |
| Carbon monoxide poisoning | Falsely NORMAL readings (CO binds hemoglobin like O2) |
| Edema | Swelling at sensor site affects accuracy |
| Bright ambient light | Can interfere with sensor |
CNA Responsibilities
- Apply the sensor correctly and ensure proper placement
- Remove nail polish from the finger if present (or use an alternate site)
- Record the reading accurately
- Report readings below 95% to the nurse (or per facility protocol)
- Report readings of 90% or below IMMEDIATELY (this is a medical emergency)
- Do NOT adjust oxygen flow rates (this is a nurse/RT responsibility)
- Observe for signs of low oxygen: confusion, restlessness, cyanosis (blue lips/nailbeds), shortness of breath
Exam Alert
Pulse oximetry measures oxygen saturation (SpO2). Normal = 95-100%. Below 90% = EMERGENCY, report immediately. Remove nail polish before measurement. The CNA can apply the sensor and record readings but CANNOT adjust oxygen. Know signs of low oxygen: confusion, restlessness, cyanosis, shortness of breath.
Study This Term In
Related Terms
Vital Signs
Vital signs are the fundamental measurements of basic body functions: temperature, pulse (heart rate), respirations (breathing rate), blood pressure, and pain (often called the "5th vital sign"). They provide critical data about a patient's physiological status and are assessed by all levels of nursing staff.
Edema
Edema is swelling caused by excess fluid trapped in the body's tissues. It most commonly occurs in the feet, ankles, legs, and hands (peripheral edema), but can affect any part of the body. Edema may indicate heart failure, kidney disease, liver disease, or other serious conditions that the CNA must report.
Fowler's Position
Fowler's position is a standard patient positioning in which the head of the bed is elevated to a 45-90 degree angle while the patient sits semi-upright or upright. Variations include low Fowler's (15-30 degrees), semi-Fowler's (30-45 degrees), standard Fowler's (45-60 degrees), and high Fowler's (60-90 degrees).
10 free AI interactions per day
Stay Updated
Get free exam tips and study guides delivered to your inbox.