Pulse Oximetry

What is pulse oximetry?

Pulse oximetry is a test that uses a small, clip-like device called a pulse oximeter (Pulse Ox) to measure oxygen levels in your blood. When you breathe, your lungs take in oxygen and send it into your bloodstream. This oxygen-rich blood is carried by your red blood cells into your heart, which pumps it to the rest of your body.

But if a health condition causes your blood oxygen level (oxygen saturation) to get too low (a condition called hypoxemia), it can make it hard for your body to work properly. The longer your blood oxygen level stays low, the higher the risk is of damage to your tissues and organs.

Pulse oximetry is a painless and quick way to find out if your oxygen level is too low. Quick treatment of low blood oxygen may help you avoid serious complications.

Other names: pulse ox, oxygen saturation monitor, finger pulse oximeter

What is it used for?

Pulse oximetry is used to check your blood oxygen level. The test may be done in your health care provider's office, a clinic, a hospital, or even your home. An at-home pulse oximeter may be helpful if you have a serious and/or chronic lung disease.

Why do I need pulse oximetry?

Your provider may give you a pulse-oximetry test as part of a routine checkup. You may also get the test if you:

• Have a condition that affects your lung function. These can include chronic obstructive pulmonary disease (COPD), lung cancer, heart failure, asthma, and COVID-19.
• Are taking medicine to treat lung disease. The test can show how well the medicine is working.
• Are having surgery. Your blood oxygen level may be checked before, during, and after your procedure.
• Have sleep apnea. This is a disorder that causes you to repeatedly stop breathing during sleep.
• Use extra oxygen (oxygen therapy). This may help your provider determine if you are getting the right oxygen flow rate from your oxygen device.
• Have shortness of breath (feeling like you can't get enough air).

What happens during pulse oximetry?

During pulse oximetry:

• A small electronic device called a pulse oximeter will be clipped to a part of your body, usually your fingertip.
• The oximeter uses a special type of light that passes through your skin and into your blood. The light may make your fingertip look red, but you won't feel any pain.
• A sensor on the oximeter measures the amount of light. That measurement is used to figure out your blood oxygen level.
• After a few seconds, the oximeter will provide a readout of your heart rate (pulse) and oxygen level.

If you have a condition that affects your lung function, your provider may recommend you use an at-home finger pulse oximeter or other oximeter to monitor your condition. Your provider will guide you on how to purchase and use your at-home device.

Will I need to do anything to prepare for the test?

Dark nail polish on the finger being tested can block the light emitted from the oximeter. Other things that may cause inaccurate results can include:

• Artificial nails
• A darker skin pigmentation (color)
• Poor circulation
• Cold skin
• Tobacco use

Are there any risks to the test?

There is no known risk to having pulse oximetry.

What do the results mean?

Results are often given as oxygen saturation levels. A normal oxygen saturation level ranges between 95% and 100%. Saturation levels may be somewhat lower and considered acceptable if you have a lung disease such as COPD or pneumonia. Your levels may also be lower if you live in an area with a higher elevation, where there is less oxygen in the air.

If you are using an at-home oximeter, watch for signs or symptoms that you have low oxygen levels, such as:

• Lips, nails, or face that look bluish (cyanosis)
• Trouble breathing or shortness of breath
• Chest pain or tightness
• Fast heart rate

Contact your provider if your oxygen saturation level is 92% or lower. If it falls to 88% or lower, seek immediate medical attention.

If you have questions about your results, talk to your provider.

Is there anything else I need to know about pulse oximetry?

Pulse oximetry results may be 2% to 4% higher or lower than your actual blood oxygen level. For a more accurate result, your provider may do a blood test called an arterial blood gas. You may need both types of tests to manage your condition.