Pulse Oximetry

This information is useful for children, adults, and older adults
pulse oximeter, sometimes used to monitor COVID-19 symptoms

Credit: Getty Images

Pulse oximetry is a term that frequently appears online and in news reports in connection with COVID-19. But what, exactly, is it?

Basically, pulse oximetry is a painless, noninvasive method of measuring the saturation of oxygen in a person’s blood.

Oxygen saturation is a crucial measure of how well the lungs are working. When we breathe in air, our lungs transmit oxygen into tiny blood vessels called capillaries. In turn, these capillaries send oxygen-rich blood to the heart, which then pumps it through arteries to the rest of the body. Our organs need a constant supply of oxygen to work properly. When the capacity of the lungs to transport oxygen into the blood is impaired, blood oxygen saturation declines, potentially putting our organs in danger. A pulse oximeter can quickly detect this drop in oxygen saturation, alerting people of the need for medical intervention.

If you have ever had a physical or visited a doctor for a medical procedure, you’ve had your blood oxygen saturation measured by a pulse oximeter. More recently, the spread of COVID-19, which can cause significant drops in blood oxygen saturation, has spurred a surge in the popularity of at-home pulse oximeters. (Some people who are worried they may have—or fear contracting—COVID-19, have purchased pulse oximeters with the aim of monitoring their blood oxygen levels.)

“It’s important to remember that not all changes in pulse oximetry are related to COVID-19,” says Denyse Lutchmansingh, MD, a Yale Medicine pulmonologist. “Other lung-related issues, such as pneumonia and blood clots, can also result in low readings on pulse oximetry. Thus, persistently low readings should be discussed with a doctor.”

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