Pulse Oximetry: Definition and Uses in Medicine

A pulse oximetry sensor.
A pulse oximetry sensor.. Dorling Kindersley/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 non-invasive, which means it doesn't use a needle or other instrument that pierces the skin. Instead, pulse oximetry uses a probe or sensor that is placed on the forehead, ear lobe, fingertip or even on the bridge of the nose to determine your blood oxygen levels.

In COPD, your doctor can use pulse oximetry to determine whether you need supplemental oxygen, and how much oxygen you might need. In the case of a sudden worsening of your condition, your doctor might use pulse oximetry to determine if you should be hospitalized.

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 sleep apnea, pulse oximetry may detect times when a person's breathing stops.

How Does Pulse Oximetry Work?

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

The probe that's clipped or placed on you 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.

Normal oxygen saturation levels range between 95% to 100%. Oxygen saturation levels in COPD and in other conditions, such as asthma, lung cancer, heart failure and pneumonia, are typically lower.

Pulse oximetry monitors are useful for monitoring supplemental oxygen therapy.

Pulse oximetry is considered quite accurate and so often is used instead of the "gold standard" oxygen saturation test, arterial blood gas analysis (which requires a blood draw).

Where Is Pulse Oximetry Performed?

Since this is a simple procedure (about as easy as taking your blood pressure), pulse oximetry can be performed virtually anywhere: at your doctor's office, in the hospital, or at home.

In fact, you can purchase wearable pulse oximetry monitors for your wrist that will track your blood oxygen levels around the clock and potentially alert your physician or caregivers if the levels fall too low. You also can buy fingertip clip-on devices that will transmit blood oxygenation data to your smart phone.


Jubran A. Pulse oximetry. Critical Care. 1999; 3(2): R11–R17.

Plüddemann A. Pulse oximetry in primary care: primary care diagnostic technology update. British Journal of General Practice. 2011 May; 61(586): 358–359.

Johns Hopkins Medicine Health Library. Pulse Oximetry fact sheet. Accessed Jan. 14, 2016.

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