Can pulse oximeters detect coronavirus? How they work and more

Some doctors are recommending these small, inexpensive devices to help monitor symptoms.

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

Sean Gallup/Getty Images

For the most up-to-date news and information about the coronavirus pandemic, visit the WHO website.

As coronavirus testing efforts continue to ramp up and face masks are now a part of everyday life, a small diagnostic tool that clips to the tip of your finger is fast becoming a must-have gadget in the fight against the coronavirus. It's called a pulse oximeter, and it painlessly checks your blood oxygen level, which can be affected by lung diseases such as COVID-19.

The device was already starting to surge in popularity as word got around that people with the coronavirus frequently arrive at the hospital with abnormally low oxygen levels. After an op-ed piece in The New York Times recommended the use of pulse oximeters to detect a frightening condition called "silent hypoxia," sales of the devices skyrocketed. Many models are sold out or on lengthy backorder online. Same with brick-and-mortar drug stores, supermarkets and box stores.

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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Pulse oximeters: Vital signs, at your fingertips

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.

How pulse oximeters measure heart rate and oxygen

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.

What's a healthy oxygen level and heart rate?

According to the Mayo Clinic, a normal pulse oximeter oxygen level reading is between 95% and 100%, and anything less than 90% is considered dangerously low, or hypoxic. Some doctors have reported COVID-19 patients entering the hospital with oxygen 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.

Can a pulse oximeter detect COVID-19?

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 COPDasthma 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.

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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.

Angela Lang/CNET

How accurate are over-the-counter pulse oximeters?

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 devices provided 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's Premarket Notification website and searching for "pulse oximeter" in the Device Name field, with or without a manufacturer's name.

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

Ben Fox Rubin/CNET

How much should I spend on a pulse oximeter?

In the 2016 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.

Where can I buy a pulse oximeter?

CNET's resident Cheapskate Rick Broida found a few deals on these three pulse oximeter models, and you can still find pulse oximeters on sale online at WalmartAmazon and eBay, but most of the name-brand devices you'll find on various best lists, like those at DigitalTrendsThe Wirecutter and Consumer 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.

Need a pulse oximeter? These models are in stock starting at $24

Don't pay jacked-up prices to measure your heart rate and blood oxygen saturation.

Rick Broida mugshot
For the most up-to-date news and information about the coronavirus pandemic, visit the WHO website.

Raise your hand if you'd never heard of a pulse oximeter until a few weeks ago, when this New York Times op-ed piece freaked everyone out with talk of "the infection that's silently killing coronavirus patients." Now raise your hand if you scrambled to buy one and found them either out of stock or significantly price-gouged. (I ordered one from Walmart for $29.99; a few days later the price was up to $49.99.)

Good news: Pulse oximeters are in stock at some stores, and although you'll still pay more than you would have a few weeks ago, there are decent deals. Whether or not you actually need one is a different story. I highly recommend reading Dale Smith's new report: Pulse oximeters: How they work, may help fight COVID-19 and more.

Pay special attention to the section on accuracy. While there are tons of pulse oximeters on the market, not all are FDA-approved. What's more, at least one study found that many of these over-the-counter devices produce inaccurate readings. Which raises the question: Should you even bother buying one?

I'll leave that to you to decide. Here are three options, all in stock at the time of this writing, at three different prices.

TomtopIf you're not in a hurry, this model ships from China in 10-20 business days -- meaning it could take as long as a month to arrive. Amusingly, you'll receive a random color: black, blue or teal, you don't get to choose. It has no user ratings, and although it's shown to be "FDA registered," it's not FDA approved. It's a roll of the dice.

ZacurateOK, this one isn't in stock at the moment, but it will be May 20, according to Amazon, and you can place your order now. Everything you need to know about the 500DL oximeter can be found in the 6,100 (!) user reviews, which average out to an impressive 4.7 stars.

Thus, while it may not be FDA-approved, chances are good it'll be pretty... Zacurate.

$40 AT AMAZON

AccuMedAlthough it's sold out at Amazon (where it has a respectable 4.3-star average rating from nearly 1,900 buyers), you can get this popular model from AccuMed proper. And it's FDA-cleared, meaning it should work as advertised. As Smith wrote in the aforementioned report: "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.'"

$40 AT ACCUMED

What are your thoughts on these things? Worth having just in case? Or better to rely on medical-grade gear?

Originally published last month. Updated to reflect new prices and availability.

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CNET's Cheapskate scours the web for great deals on tech products and much more. For the latest deals and updates, follow the Cheapskate on Facebook and Twitter. Find more great buys on the CNET Deals page and check out our CNET Coupons page for the latest promo codes from Best BuyWalmartAmazon and more. Questions about the Cheapskate blog? Find the answers on our FAQ page.

The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.

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