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Mar.22.2022
 Pulse Oximetry

Pulse Oximetry

A sensor clipped onto a finger to test the amount of oxygen in the blood.

Pulse oximetry is a technology that measures the oxygen saturation level in the blood through the skin without the need for a blood sample. This may also be referred to as oxygen level. The device used to measure the oxygen level is called a pulse oximeter. This device also measures the heart rate (pulse). Pulse oximetry helps to assess:
  • Current oxygen level, including low blood oxygen levels (hypoxemia).
  • The need for or effectiveness of oxygen therapy or other treatments, including the need for more or less oxygen.
  • Blood flow (circulation) to different parts of the body.
  • Oxygen level during activity.

What are the benefits?

Benefits of pulse oximetry include:
  • Not needing a blood sample to measure the oxygen level.
  • The test does not hurt.
  • Having the option to measure oxygen level continuously or as needed.
  • An alarm to tell you when your oxygen levels are out of range if pulse oximetry is continuous.

What are the risks?

The risks associated with pulse oximetry are rare. However, there is a risk of skin sores if the sensor is left in the same spot for long periods of time.

What happens during the test?

Pulse oximetry is done using a pulse oximeter device with a light sensor attached.
  • One side of the sensor passes a red beam of light through the skin, and the other side of the sensor measures the amount of light that is absorbed while it passes through. The sensor is connected to the pulse oximeter.
  • The pulse oximeter uses the information from the sensor to calculate the percentage of blood cells carrying oxygen in the blood.
  • The sensor is placed on an area of the body where the beam of light can easily pass through the skin.
    • For adults and children, the sensor is usually a clip placed on a finger, with the light centered over the nail bed. The sensor may also be placed on an earlobe or toe.
    • For babies, the sensor is usually a sticky tape strip that is placed around areas such as the sole of a foot or the palm of a hand.

What can I expect after the test?

  • The pulse oximetry results should be available right away.
  • If your pulse oximetry results are low, you may need to use oxygen.
  • The pulse oximetry results are a percentage. The normal value may vary depending on your medical condition.
    • Most healthy people have oxygen saturation levels between 95% and 100%.
    • Low oxygen saturation levels are below 90%. This may happen in people with lung conditions, such as long-term (chronic) obstructive pulmonary disease (COPD).

What can affect the accuracy of the oximetry reading?

Pulse oximetry depends on the amount of light absorbed as it passes through skin tissue. Because of this, the accuracy of this measurement can be affected by one or more of the following:
  • Factors such as:
    • Dark nail polish or artificial nails.
    • Very dark skin.
    • Shivering or too much movement.
    • Bright, artificial lighting.
    • Chronic smoking and recent breathing-in (inhalation) of smoke or carbon monoxide.
  • Conditions such as:
    • Cool skin or poor blood flow to the area where the sensor is placed.
    • Sweating or very warm skin in the area where the sensor is placed.
    • Anemia, or low levels of hemoglobin or red blood cells.
    • Polycythemia vera. This is a bone marrow disease that causes high levels of red blood cells, white blood cells, and platelets.

If a more accurate measurement is needed, a blood sample will be taken.

Summary

  • Pulse oximetry uses a device to measure the oxygen level in the blood.
  • Pulse oximetry does not hurt. The risks associated with pulse oximetry are rare.
  • Most healthy people have oxygen levels between 95% and 100%. A low oxygen saturation level is below 90%.
  • People with low oxygen levels may need supplemental oxygen.

This information is not intended to replace advice given to you by your health care provider. Make sure you discuss any questions you have with your health care provider.

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