Pulse oximeters: How they work, may help fight COVID-19 and more – CNET

A pulse oximeter attaches to a finger and uses light to detect the level of oxygen in your blood.

Ascoronavirus testing efforts continue to ramp up and face masksbecome part of everyday life, a tiny diagnostic tool that clips to your finger is quickly becoming a must-have gadget in thefight against COVID-19. It's called a pulse oximeter, and it checks your blood oxygen level.

The device was already beginning to surge in popularity as the public learned that people with the coronavirus oftenarrive at the hospital with abnormally low oxygen levels. After anop-ed piece in The New York Timeson April 20 recommended that pulse oximeters be used to identify the sickest among COVID-19 patients and detect the frightening condition known as "silent hypoxia," sales of the devicesskyrocketed. Right now, most are sold out in stores and online.

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But questions and controversy have arisen around the at-home use of pulse oximeters, which painlessly measure heart rate and oxygen levels. It's not entirely clear if pulse oximeters can help detect a coronavirus infection or whether their widespread use can helpcurb the spread of COVID-19.

Whether you already have a pulse oximeter or you're thinking about buying one, here's what you need to know about what they do, how they work, what the results mean and how accurate they might be.

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A pulse oximeter is a small medical device that measures heart rate and blood oxygen saturation. It's usually clipped to your finger, but it can also attach to your ear, nose, toe or forehead. Some are battery powered and provide real-time results on a small LED display on the device itself. Others connect with a wire to a separate vital sign monitor that records even more precise information about your heart rhythm, body temperature and blood pressure using other sensors connected to your body.

A pulse oximeter measures your blood oxygen saturation and heart rate by shining a light through your skin and detecting both the color and movement of your blood cells. Oxygenated blood cells are bright red, deoxygenated cells are dark red.

The pulse oximeter compares the number of bright red cells to dark red cells to calculate your oxygen saturation as a percentage. So, for example, a reading of 99% means only 1% of the blood cells in your bloodstream have been depleted of oxygen.

Every time your heart beats, it pushes your blood through your body in a quick pulse (which is why "pulse" is another word for "heart rate"). A pulse oximeter, using light, detects this movement and calculates your heart rate in beats per minute, or BPM.

According to the Mayo Clinic, a normal pulse oximeter oxygen level reading is between95% and 100%, and anything less than 90% is considered dangerously low, or hypoxic. Some doctors have reported COVID-19 patients entering the hospital withoxygen levels at 50% or below.

A normal resting heart rate is between 60 and 100 BPM. Typically, lower is better, as a slower heart rate is usually an indication of a strong cardiovascular system.

Not exactly. Although many doctors report that patients with COVID-19 are presenting with dangerously low blood oxygen levels, COVID-19 isn't the only disease that can cause such a problem. Chronic lung diseases, like COPD, asthma and other non-COVID-19 lung infections can also result in a low oxygen count.

A low oxygen reading by itself is not enough to diagnose COVID-19, but your doctor would want to know about it, especially if you notice the level decreasing over time. And if you've been diagnosed with COVID-19, your doctor may want you to monitor your oxygen level to determine whether your condition is worsening or improving.

Although medical professionals continue to rely on temperature checks as an indication of a coronavirus infection, many patients with COVID-19 do not have fevers.

Like with any electronic equipment, not all pulse oximeters are created equal. A 2016 study of low-cost pulse oximeters concluded several inexpensive consumer-grade devicesprovided highly inaccurate readings.

Some pulse oximeters have been cleared by the FDA, which means they should meet FDA standards for accuracy. Note that there is a distinction between "FDA-approved" and "FDA-cleared," with "cleared" being the less rigorous of the two. That said, Class II medical devices like pulse oximeters are usually "cleared" rather than "approved."

You can look for pulse oximeters on the FDA-cleared list by visiting the FDA'sPremarket Notification website and searching for "pulse oximeter" in the Device Name field, with or without a manufacturer's name.

Although retailers like Amazon and Walmart still have pulse oximeters available, they're often unbranded and of questionable accuracy.

In the2016 study that found most low-cost pulse oximeters to be relatively inaccurate, "low-cost" was defined as costing less than $50. Pulse oximeters that have been cleared by the FDA tend to range in price from around $50 to $60 to well into the hundreds and even thousands of dollars.

You can still find pulse oximeters on sale online atWalmart,Amazon andeBay, but most of the name-brand devices you'll find on various best lists, like those atDigitalTrends,The Wirecutter andConsumer Reports, are either sold out completely or on backorder, with shipping estimates weeks or sometimes months away.

This week, the CDC added five more official COVID-19 symptoms for a total of seven, which are detailed here. However, symptoms, vital signs and statistics aren't the only way to track the pandemic: Memes and social media chatter are relevant data points, too. Depression and anxiety may not be symptoms of the disease itself, but as the pandemic continues, you're not the only one feeling down about it.

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Pulse oximeters: How they work, may help fight COVID-19 and more - CNET