A sensor, attached to a device called a pulse oximeter, is clipped to your finger or ear, and then directs a beam of light through the tissue. The device is able to monitor oxygen saturation in the blood by measuring the amount of light absorbed by oxygenated hemoglobin (the oxygen-carrying pigment in red blood cells).
Purpose of the Oximetry
- To monitor oxygen levels in patients at risk for decreased oxygen saturation in the blood (hypoxemia), including those who are undergoing surgery, cardiac stress testing, or pulmonary function tests; people who are heavily sedated, severely injured, or using a mechanical ventilation machine; and individuals undergoing studies in a sleep laboratory.
Who Performs It
- A doctor, a nurse, or a technician
- A variety of factors may interfere with the results, including extreme changes in temperature, movement of the fingers, severe anemia, and fingernail polish.
- This test should not be performed on patients who have taken light-activated drugs for photo-dynamic therapy.
Before the Oximetry
- If you wear nail polish, remove it from at least one fingernail.
What You Experience
- The person performing the test will rub your fingertip or ear to increase blood circulation, and attach the monitoring sensor.
- The procedure is painless and noninvasive, and takes a few minutes.
Risks and Complications
After the Oximetry
- No special aftercare is needed.
- If your oxygen levels are insufficient, you may be given supplemental oxygen through a face mask or small prongs that fit in the nose. Additional tests, such as arterial blood gases, may be needed to determine the cause.
- If you are recovering from surgery with general anesthesia, the results of oximetry will help determine when you are ready for discharge.
- Decreased oxygen levels during sleep studies may indicate sleep apnea.
The Johns Hopkins Consumer Guide to Medical Tests
Simeon Margolis, M.D., Ph.D., Medical Editor
Updated by Remedy Health Media