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(CNN) – Many patients with severe cases of covid-19 have been shown to have extremely low levels of oxygen in the blood. Others who have tested positive for coronaviruses have difficulty breathing.
Perhaps that is why people are so interested lately in pulse oximeters, which are medical devices that measure oxygen saturation in red blood cells.
Pulse oximeters were sold out on CVS and Walgreens websites, a search showed on Friday. Sales of pulse oximeters in the United States increased on January 20 when the first covid-19 case was confirmed in the country, and again in mid-February, according to Quartz. While the rate of increase has slowed, sales have continued to grow every week since then, the outlet reported.
Meanwhile, Google searches for “pulse oximeters” skyrocketed in early April and peaked in recent days, after emergency physician Richard Levitan published an op-ed in The New York Times suggesting that the devices could provide early warnings about the need for covid-19 treatment.
So should you go out and buy one? This is what you should know.
What is a pulse oximeter
A pulse oximeter is a medical device that measures the saturation of oxygen in a person’s red blood cells. Usually attached to the finger, it can also be placed on the ear, forehead, nose, or toes.
The device works by shining a light through the skin, which it then analyzes to determine how much oxygen the blood carries.
Doctors and other medical professionals use pulse oximeters in patients who experience shortness of breath or those who have lung or heart problems to determine if they are receiving enough oxygen. They are commonly used by health professionals in hospitals and clinics when monitoring vital signs.
Pulse oximeters are occasionally used in home settings for people who have underlying health conditions. They can also be found on Amazon, in pharmacies, and in medical supply stores, although prices and quality can vary widely.
A doctor suggests a general evaluation
Levitan, who spent 10 days in New York treating cases of coronavirus pneumonia, wrote in The New York Times that pulse oximeters could detect a form of oxygen deprivation in which patients do not experience difficulty breathing, despite from low oxygen levels and pneumonia readings from chest x-rays.
According to Levitan, the devices indicated to two emergency doctors he knew they needed treatment from the start, and they were both hospitalized and recovered.
“Widespread oximetry monitoring for covid pneumonia, whether people check themselves on home devices or go to clinics or doctor’s offices, could provide an early warning system for the types of respiratory problems associated with pneumonia by covid ”, he wrote.
But you probably don’t need one, experts say
Experts from the American Lung Association and the American Thoracic Society said that having a pulse oximeter at home would not be particularly helpful for detecting the coronavirus for most people.
“If the question is, ‘Would it be a good early indicator if someone has a covid-19 infection?’ I would say probably not,” said Dr. J. Randall Curtis, professor of pulmonary and critical care medicine at the University of Washington.
That’s because low oxygen levels are a relatively late indicator that a person has covid-19, Curtis said. People who potentially have the disease will likely experience other symptoms, such as fever, dry cough, body aches, or fatigue, that would lead them to seek medical attention days before noticing a decrease in their blood oxygen levels.
It is also possible that people using pulse oximeters at home may see inaccurate readings. Nail polish, artificial nails, cold hands and poor circulation are things that can interfere with the light used by the devices and lead to false numbers, said Dr. David Hill, pulmonary and critical care physician and spokesman. from the American Lung Association.
“One reason not to encourage everyone to go out and get an oximeter is that there is a greater chance of having falsely low readings in a normal population,” he said. “Then those people will call doctors or go to emergency rooms that are already occupied by something that is potentially nothing.”
There are cases where it would make sense to use a pulse oximeter at home, Curtis and Hill said.
People who have already tested positive for covid-19 and are recovering at home can ask their doctor about using a pulse oximeter to check for oxygen or more supportive care. But those who are healthy and experiencing no symptoms can probably save $ 50 or more, otherwise they could spend on the device, Hill said.
Some people turn to apps
Due to the shortage of devices, some people turn to oximeter applications. But a recent study suggests that apps don’t necessarily work as well, and could even be dangerous.
An analysis by the University of Oxford examined the use of oximeter applications in the context of the covid-19 pandemic and concluded that they were not reliable.
“Oxygen saturation levels obtained from such technologies should not be relied upon,” the authors wrote.
Pulse oximeters measure light transmitted or reflected through the skin at two different wavelengths (usually red and infrared) to determine the level of oxygen saturation in the blood, the authors explained.
Smartphone apps, which generally claim to measure oxygen saturation through light from the flash and camera, do not generate such accurate readings because the camera cannot measure the reflection of light at two wavelengths. One app claimed to use a red light source, but the authors found that it only used a single wavelength measurement, rendering the reading inaccurate.
