The at-home device can be useful for monitoring coronavirus symptoms, along with other respiratory conditions.

By Leah Groth
April 28, 2020
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You may not recognize the name, but you've likely seen a pulse oximeter before (probably in a doctor's office or hospital setting). Much like a thermometer reads your temperature, a pulse oximeter—a small rectangular device that clips onto your finger—reads your blood oxygen levels and heart rate. But unlike a thermometer, which many people already have in their homes, pulse oximeters aren't a mainstay in many medicine cabinets. COVID-19, however, may change all of that.

"Everybody is trying to avoid leaving the house—especially to go to the doctor," Sharon Chekijian, MD MPH, an emergency medicine doctor with Yale Medicine, explains to Health, adding that those with mild symptoms are often urged to stay home and consult their doctors via telemedicine. But sometimes it's hard to distinguish milder symptoms from those that warrant emergency medical care—that's where a pulse oximeter can come into play. "Many doctors have been advising patients, especially those with worrisome symptoms or chronic health conditions like heart or lung problems, to buy a pulse oximeter for home to monitor their oxygen levels without trekking to the doctor or [emergency department],” says Dr. Chekijian.

Richard Levitan, MD, is one of those doctors. The emergency physician wrote an op-ed for The New York Times detailing his experience volunteering at New York City's Bellevue Hospital, where he saw an overwhelming amount of critically-ill patients who arrived at the hospital with dangerously low oxygen levels. It's in cases like these, he wrote, when a pulse oximeter can help. "Widespread pulse oximetry screening for COVID pneumonia—whether people check themselves on home devices or go to clinics or doctors’ offices—could provide an early warning system for the kinds of breathing problems associated with COVID pneumonia,” he wrote, adding that all patients who test positive for COVID-19—and even patients who show symptoms but have not had testing—should have pulse oximetry monitoring for two weeks, since that's typically when COVID-19 pneumonia can develop. 

While pulse oximeters are by no means a necessity for the average healthy person—though some doctors may suggest them to those with preexisting breathing issues like asthma, COPD, or other lung diseases—they may be helpful during the COVID-19 pandemic. Also important: All doctors aren't in agreement on whether or not pulse oximeters are a good idea for widespread home-monitoring, but here's what you need to know if you're interested in investing in one.

What is a pulse oximeter?

A pulse oximeter (also called a "Pulse Ox") is a device that measures oxygen levels (or oxygen saturation) in your blood, according to Johns Hopkins Medicine—specifically the peripheral oxygen saturation, since it's detected peripherally (externally) on the finger, toe, or ear. That's important, per the World Health Organization, because your blood (specifically proteins in your red blood cells) carries oxygen around your body and delivers it to your tissues.

Pulse oximeters also measure pulse rate, in terms of heartbeats per minute—this can also show how well the body's tissues are "perfused" or supplied with blood, and ultimately, oxygen.

In terms of COVID-19, a pulse oximeter can help detect or monitor breathing issues associated with COVID-19 or COVID-19 pneumonia. The devices can be especially helpful for those experiencing shortness of breath with diagnosed COVID-19—either to keep an eye on progress or to determine when it's worth an emergency room visit.

How do you use a pulse oximeter?

If you're using an at-home pulse oximeter, the device will clip onto your finger, toe, or earlobe. "Most commonly, it is a clip to place on your finger and it transmits wavelengths of light to a sensor which accurately calculates your blood oxygen saturation," George Fallieras, MD, medical director of BioCorRx and doctor at LA Surge Hospital. That wavelength is targeting hemoglobin, a protein in your blood that carries oxygen—and the light absorbed by the blood varies with the oxygen saturation of hemoglobin, per the WHO, which then transmits a reading

The best way administer the test is to do so while sitting down, says Dr. Chekijian. "The best finger to use it on is the middle finger," she adds. Make sure to take off any nail polish, avoid using on cold fingers, and sit still. "If your fingers are cold, you are wearing nail polish, or if you are moving around, it may not pick up a correct reading," she explains. Also, if you use somebody else’s device be sure to disinfect thoroughly before and after use.

Another important thing to check for during a reading is that there is a tracing on the device that looks like a sine or continuous wave, Dr. Chekijian instructs. "The wave varies with your breathing. This means the device is really picking up the right signals. This is especially important if the reading looks low so you don’t misinterpret it." If the reading is low, but you see a squiggly line instead of a regular sine wave, you are probably not getting a great reading.

What is a normal pulse oximeter reading?

According to Dr. Chekijian, for a healthy person without lung problems, a reading between 96-100% would signify a normal level of oxygen in the blood. The WHO lowers that by 1%, saying that anything between 95-100% is normal, and anything under 94% should be evaluated by a medical professional. A pulse oximeter reading of anything below 90% is considered a "clinical emergency," per the WHO and should be treated urgently. 

“If you do think you have COVID and you’re using the pulse oximeter to measure your oxygen level, be sure to make a log of the readings so you can see if there are any changes,” Dr. Chekijian suggests. Also, the numbers aren’t the only thing you should focus on. She suggests noting how you were feeling at the time of the reading—like if you felt fine or if you were experiencing shortness of breath. 

It's important to keep track of the second number, your heart rate, too. "That is helpful to note as well so you can report it to your doctor," says Dr. Chekijian. According to the WHO, a normal heart rate in those ages 10 and older ranges between 60 to 100 beats per minute.

Are there any downsides to using an at-home pulse oximeter?

As with any at-home test, there is always room for faulty readings or incorrect use. The WHO acknowledges this, and prompts medical professionals to rely on their own clinical judgement versus a reading on the device. If you get a strange reading at home (and you're not feeling ill), you can check the device's accuracy on another healthy family member—but if you're uneasy about a reading and how you're feeling, it's best to seek medical attention.

It's also important not to let a good pulse oximeter reading to give you a false sense of security if you're feeling unwell. If you're feeling lousy—shortness of breath, cough, fever—and you haven't been diagnosed with COVID-19, it's best to check in with your health care provider. The good news: Sometimes a good pulse oximetry reading can be a relief if you are feeling lousy with a COVID-19 diagnosis, to show you aren't getting any worse.

Where can you get a pulse oximeter?

That's the million-dollar question right now. Because they're so in-demand, pulse oximeters, which are normally bought online, at drug stores, or via medical device suppliers, can be hard to find right now. "If you think you need one, call ahead [to your preferred store] so you don’t go on a wild goose chase and expose yourself to unnecessary risk in the process,” Dr. Chekijian urges.

Your current best bet is to check out Amazon or other websites for available pulse oximeters. According to Wirecutter, part of The New York Times, you can check out devices listed on the Food and Drug Administration’s 510(k) Premarket Notification Database by searching "oximeter."

For now, it's also best to stick to at-home finger pulse oximeter devices—while there are some apps for smartphones that claim to measure oxygen levels, recent research from the Oxford COVID-19 Evidence Service Team has found that that none of them are reliable enough to substitute for the real thing.

If you can't find a pulse oximeter due to the shortage, and you're worried about your levels, you can (and should) check in with your doctor to see if you can get a reading. "If you feel like you can't catch your breath or are winded with activity please visit a minute clinic, urgent care, or call your doctor to see if you can be seen," says Dr. Chekijian. "If it's after hours, call 911 or proceed to the emergency department so we can check your levels for you."

The information in this story is accurate as of press time. However, as the situation surrounding COVID-19 continues to evolve, it's possible that some data have changed since publication. While Health is trying to keep our stories as up-to-date as possible, we also encourage readers to stay informed on news and recommendations for their own communities by using the CDCWHO, and their local public health department as resources.

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