Should You Have a Pulse Oximeter in Your Family First Aid Kit?

Pulse oximeters measure heart rate and oxygen levels, but can they accurately detect dangerous symptoms of COVID-19? Experts explain how pulse oximeters work, what the readings mean, and whether parents should keep one in the house.

Close up of a person putting a pulse oximeter on their finger.
Photo: Cavan Images/Getty Images

Whether you’re an adult or child, the coronavirus can cause hypoxia, or low levels of oxygen in the body. And while hypoxia is usually accompanied by shortness of breath, doctors are now noticing a scary new trend: Some COVID-19 patients can’t self-assess emergency-level breathing difficulties, and when they finally visit a healthcare center, they might be close to respiratory distress.

Doctors call this phenomenon “silent hypoxia.” It happens when your lungs aren’t pumping enough oxygen into the bloodstream, but you don’t experience any major symptoms like chest pain or shortness of breath. Silent hypoxia likely won’t have long-term consequences, but in severe cases, organs could fail before the patient receives proper treatment.

This news has been frightening parents, who are desperately trying to keep their children safe during the pandemic. It’s also promoting them to buy pulse oximeters—electronic devices that measure oxygen levels and heart rate by clipping onto a patient’s finger.

“Pulse oximeters measure the oxygen saturation of arterial blood, which is blood that has picked up oxygen in the lungs and is then pumped by the heart out into peripheral tissues like your finger,” explains Cindy Knall, PhD, associate professor of the WWAMI School of Medical Education at the University of Alaska Anchorage.

But how accurate are pulse oximeters in detecting silent hypoxia, and should your family buy one? We spoke with experts to find out.

How Does a Pulse Oximeter Work?

To use a pulse oximeter, you typically place it on the index or middle finger, says Nadine M. Aktan, PhD, APN-BC, professor of nursing at William Paterson University in New Jersey. Depending on the product, your toe or earlobe could also work. The oximeter measures the “difference in light absorption of red and infrared light between oxygenated and deoxygenated blood,” says Dr. Knall.

The results will be given as a percentage. Normal oxygen saturation readings generally range from 95 and 100 percent, says Dr Knall, but keep in mind that one’s baseline level may differ slightly. “A person is considered to be hypoxic if the reading is below 90 percent, and in a severe hypoxic state if the level is 85 percent or lower for more than two minutes,” she adds.

Are Pulse Oximeters Accurate?

Pulse oximeters are reasonably accurate as long as the person doesn’t have severe respiratory distress. “At oxygen saturation levels of 90 percent or higher, the one-point accuracy of a pulse oximeter is greater than 97 percent,” says Dr. Knall. “However, below 90 percent saturation, they tend to overestimate the actual oxygen saturation, making the level appear better than it is.”

Unfortunately, this inaccuracy could give a false sense of security, especially in those who are older or have underlying health conditions. Also, Dr. Knall adds, pulse oximeters don’t reliably track change over time as you would need for a severe COVID-19 patient.

It’s important to note that accuracy varies depending on the circumstances of the measurement. “Accuracy can be affected by user technique, temperature of the hands, history of smoking, length of nails, and/or the use of nail polish,” says Dr. Aktan. Your elevation can also affect the reading of the pulse oximeter.

Should I Buy a Pulse Oximeter?

The decision to buy a pulse oximeter is entirely up to you. But it helps to know the facts: “Currently there isn’t any good data suggesting that the use of home pulse oximeters prevents or decreases bad outcomes in severe COVID-19 patients,” says Dr. Knall. “It’s hard to say that people should keep a pulse oximeter at home, especially given that they are known to overestimate oxygen saturation as you get below 90%.”

Essentially, those who are worried about COVID-19 symptoms can use one to monitor trends in oxygen levels. But people must also understand that pulse oximeters might not be accurate—especially if oxygen levels are below 90 percent. “If one elects to do so, home monitoring of oxygen saturation should not replace consultation with a healthcare professional, but may provide supplemental information to determine risk or need to seek emergency services,” says Dr. Aktan.

She adds that the best thing to do is stay educated about the symptoms and risk factors for COVID-19, and contact your healthcare provider with any questions regarding yourself or your kids.

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