What Is Pulse Oximetry?

What to expect when undergoing this test

Hand with pulse oximeter
abalcazar/E+/Getty Images

Pulse oximetry is a way of determining the oxygen level in your blood, which is an important indicator of your overall health. The test is noninvasive and uses a probe or sensor placed on the forehead, earlobe, fingertip, or bridge of the nose to determine your blood oxygen levels. It's often used in emergency rooms or critical care settings, though it may also be used in some healthcare providers' offices.

Purpose of Test

Pulse oximetry is a means of measuring oxygen saturation or the percentage of hemoglobin saturated with oxygen in arterial blood. This can be a useful tool in the management of chronic obstructive pulmonary disease (COPD) and other lung conditions to check pulmonary function, or how well your lungs are working.

In COPD, your healthcare provider can use pulse oximetry to determine whether you need supplemental oxygen and, if so, how much. In the case of a sudden worsening of your condition, your practitioner might use pulse oximetry to determine if you should be hospitalized. One study of COPD patients using pulse oximeters showed that the devices were highly effective in predicting when COPD symptoms suddenly got worse, known as exacerbations.

There are many other conditions and situations where pulse oximetry provides useful information. For example, an anesthesiologist might use pulse oximetry to monitor your blood oxygen levels during or after sedation for surgery. In addition, in assessment for sleep apnea, pulse oximetry may detect times when a person's breathing stops.

Pulse oximeters are widely used in hospitals, clinics, healthcare providers' offices, and homes. They're generally accurate and provide spot-on readings of oxygen saturation levels. This can be a valuable tool, especially in emergency situations.

During the Test

Your blood contains hemoglobin, which carries oxygen molecules from your lungs to where they're needed in your body. In pulse oximetry, how much of the hemoglobin in your blood is and is not carrying oxygen is what's measured.

Since this is a simple procedure (about as easy as taking your blood pressure), pulse oximetry can be performed virtually anywhere. It is fairly quick and should be painless:

  1. The sensor gently clamps onto your finger or another body part to measure your oxygen saturation.
  2. The device then uses light in specific wavelengths to measure oxygen saturation of your hemoglobin.

Hemoglobin that's carrying oxygen absorbs this light differently than hemoglobin that isn't carrying oxygen, and the data collected by the probe will show the difference.

Wearable Monitors

You can purchase a wearable pulse oximetry monitor for your wrist that will track your blood oxygen levels around the clock and potentially alert your healthcare provider or caregivers if the levels fall too low. You also can buy fingertip clip-on devices that will transmit blood oxygenation data to your smartphone.

Interpreting Results

Normal oxygen saturation levels range between 95% and 100%. Oxygen saturation levels in COPD and in other conditions, such as asthmalung cancerheart failure, and pneumonia, may be lower.

Pulse oximetry should not replace, but rather complement, the use of spirometry in the diagnosis and management of chronic respiratory illnesses like COPD.

Pulse oximetry monitors are also useful for monitoring supplemental oxygen therapy to determine if your levels should be titrated up or down depending on your needs.

Never titrate your oxygen levels without specific instructions from your healthcare provider.

Although widely accepted in clinical and home settings, pulse oximetry should never replace arterial blood gas analysis (considered the gold standard of blood oxygen measurement) and/or sound medical advice from your healthcare provider. It should only be used as a screening tool when low blood oxygen levels are suspected.

A Word From Verywell

Pulse oximetry is a painless way to get an accurate measure of your blood oxygen saturation levels, and is a great tool for determining lung function, disease progression, and how well certain treatment methods are working.

However, never rely on a pulse oximeter to determine how you should be feeling. If your oxygen saturation level is normal but you're severely short of breath and/or are experiencing other troubling symptoms, seek emergency medical attention and notify your healthcare provider as soon as possible.

Was this page helpful?
6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Plüddemann A, Thompson M, Heneghan C, Price C. Pulse oximetry in primary care: primary care diagnostic technology updateBr J Gen Pract. 2011;61(586):358–359. doi:10.3399/bjgp11X572553

  2. Shah SA, Velardo C, Farmer A, Tarassenko L. Exacerbations in Chronic Obstructive Pulmonary Disease: Identification and Prediction Using a Digital Health System. J Med Internet Res 2017;19(3):e69.

  3. Vold ML, Aasebø U, Wilsgaard T, Melbye H. Low oxygen saturation and mortality in an adult cohort: the Tromsø studyBMC Pulm Med. 2015;15:9. Published 2015 Feb 12. doi:10.1186/s12890-015-0003-5

  4. Pandya NK, Sharma S. Capnography And Pulse Oximetry. [Updated 2020 Jan 30]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK539754/

  5. Castro D, Keenaghan M. Arterial Blood Gas. [Updated 2020 Feb 20]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK536919/

  6. Torp KD, Simon LV. Pulse Oximetry. [Updated 2019 Apr 28]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK470348/

Additional Reading