As weeks and months go by without a vaccine or silver-bullet treatment for the coronavirus, we’re all looking for ways to protect our families from falling severely ill. The latest contraption to capture our attention? The pulse oximeter, to monitor your heart rate and blood oxygen level.

The devices are commonly used in hospitals to track patients’ vital signs, and doctors are finding them useful for identifying troubling developments among COVID-19 patients. They’re not a medicine cabinet staple in most households, but should they be?

We spoke with three local physicians to get the lowdown on these devices and whether you need one: Hernan Alvarado, director of respiratory therapy at Temple Health; William A. Gray, a cardiologist at Main Line Health and president of the American Heart Association’s Philadelphia chapter; and Marcus Schabacker, an intensive care specialist and CEO of the ECRI in Plymouth Meeting.

What is a pulse oximeter and what does it do?

A pulse oximeter is a small device that clips onto a fingertip and measures heart rate and blood oxygen levels, both of which are tracked on a small screen. The device emits a small beam of light, and the amount of reflection or absorption of that light indicates how much oxygen is in the blood.

Heart rate and blood oxygen levels are good indicators of a patient’s stability. In hospitals, these devices are commonly used as a noninvasive way to track vital signs before, during and after surgery. Patients who use at-home oxygen to manage chronic heart or lung problems, such as chronic obstructive pulmonary disease, may also use a pulse oximeter.

How are they used in COVID-19 treatment?

COVID-19 is associated with pneumonia-like symptoms, and many patients who develop severe cases of the virus experience such difficulty breathing that they must be put on a ventilator. Reports of blood oxygen levels dropping before patients realize they are in severe respiratory distress suggest that such declines could be a sign that a mild case of COVID-19 is worsening. Monitoring levels may allow for earlier intervention.

Who would benefit from having one at home?

People who test positive but have mild symptoms will likely be sent home with instructions to isolate from others, monitor their symptoms and call their doctor if their condition worsens. Using a pulse oximeter could help with that monitoring.

Doctors agree that there is no reason for a healthy individual to routinely measure blood oxygen levels, as a decline is unlikely to be the first symptom of illness.

“It’s not a great early warning system,” said Gray.

I’m not sick. Should I get a pulse oximeter?

Doctors have varying opinions about whether a pulse oximeter should join a thermometer in your medicine cabinet. Gray and Schabacker worry that people could decide if their blood oxygen levels are normal, they don’t need to worry about any signs of illness.

“It could be useful, but don’t replace common sense with a pulse oximeter reading,” Gray said.

But both said people with underlying heart or lung conditions that make them more vulnerable to developing severe cases of COVID-19 may use the device to track their blood oxygen levels if they start to feel sick.

Alvarado said he thinks there’s no harm in anyone having one, so long as they understand that the devices can give false readings and should be interpreted in the context of other health indicators. The more information you’re able to give your doctor when you’re feeling sick, the better, and a pulse oximeter reading could be one more detail to help your doctor evaluate your situation, he said.

“If you feel as though you’re having respiratory distress and want to give a physician an informed picture of what they’re dealing with, it’s not a bad thing to have,” he said.

How do I use it?

Most consumer pulse oximeters attach to a finger, so make sure the sensors are securely in place. For best readings, make sure your hand is warm, relaxed, and below your heart. Typically, a reading over 94 is considered healthy, while a reading under 92 is cause for concern.

But one-time readings can be misleading. You could get a false reading if you have cold hands, poor circulation or are wearing nail polish or artificial nails. So check your reading multiple times over an extended period. A steady, low reading or downward trend could be a sign of potential trouble.

But try not to panic — call your doctor to share your other symptoms, too.

“We look at that number, but we look at it in context of the total clinical picture,” Alvarado said.

How do I buy one?

Pulse oximeters are available in stores and online, though supplies have been running low because of the pandemic. You can get one for under $50, though like many coronavirus commodities, prices have spiked. All basic models have a screen where you can see the trend and numbers, and our experts did not recommend any specific brands. ECRI suggested looking for a device that meets International Organization for Standardization regulations, or “ISO standards."

Other factors to consider when selecting a device:

  • Are the numbers large enough for you to see?
  • Are the buttons or touch screen easy to use?
  • Does it come with instructions in your preferred language?
  • Does it have any operating requirements, such as internet access or batteries?