(CNN) – Many patients with severe cases of Covid-19 have been shown to have extremely low levels of oxygen in the blood. Others who test positive are short of breath.
This may be the reason why people have recently become interested in pulse oximeters, medical devices that measure the oxygen saturation of red blood cells.
Pulse oximeters have been sold on CVS and Walgreens websites, research revealed on Friday. US sales of pulse oximeters increased on January 20 when the country’s first Covid-19 case was confirmed, and again in mid-February, according to Quartz. As the rate of increase has slowed, sales have continued to grow every week since then, the store reported.
Meanwhile, Google is looking for “pulse oximeters” that peaked in early April and have peaked in recent days after emergency physician Richard Levitan published an editorial in the New York Times suggesting that the devices could provide early warnings of the need for treatment. against Covid-19.
So should you buy one? Here’s what you need to know.
What is a pulse oximeter
A pulse oximeter is a medical device that measures the oxygen saturation of a person’s red blood cells. It usually attaches to your finger, but it can also be attached to the ear, forehead, nose, or toes.
The device works by passing light through the skin, which is then analyzed to determine the amount of oxygen carried in the blood.
Doctors and other healthcare professionals use pulse oximeters in patients with shortness of breath or those with lung or heart problems to determine if they are getting enough oxygen. Health professionals use them regularly in hospitals and clinics when checking for vital signs.
Pulse oximeters are sometimes used at home for people with underlying health conditions. They can also be found on Amazon, pharmacies, and medical supply stores, although prices and quality can vary widely.
Doctor suggests widespread screening
Levitan, who spent 10 days in New York City treating coronavirus pneumonia, wrote in the New York Times that pulse oximeters can detect a form of oxygen starvation in which patients do not experience shortness of breath , despite low oxygen levels and pneumonia readings from chest x-rays.
According to Levitan, the devices reported to two emergency doctors that he knew they needed early treatment, and both went to the hospital and recovered.
“Widespread pulse oximetry screening 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 those types of breathing problems associated with Covid pneumonia, “he writes.
But you probably don’t need it, say experts
Experts from the American Lung Association and the American Thoracic Society said that for most people, having a pulse oximeter at home would not be particularly helpful in detecting the virus.
“If the question is, ‘Would this be a good early indicator if someone has Covid-19 infection?’ “I would probably say no,” said Dr. J. Randall Curtis, a professor of pulmonary medicine and intensive care at the university. from Washington.
It is because low oxygen levels are a relatively late indicator that a person has Covid-19, Curtis said. People potentially affected by the disease are likely to experience other symptoms, such as fever, dry cough, body aches or tiredness, which would encourage them to see a doctor for several days before noticing a drop in their oxygen levels in the blood.
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 all things that can interfere with the light used by the devices and cause false numbers, says Dr. David Hill, physician in pulmonary and intensive care and spokesperson for the American Lung Association.
“One reason not to encourage everyone to go out and get one is that there is a higher probability of having falsely low readings in a normal population,” he said. “Then these people will call doctors or go to emergency rooms that are already occupied for potentially something that is nothing. “
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There are cases where it makes sense to use pulse oximetry at home, said Curtis and Hill.
People who have already tested positive for Covid-19 and are recovering at home may want to consult their doctor about using a pulse oximeter to check if they need oxygen or supportive care more. But those who are healthy and symptom-free can probably just save the $ 50 they might otherwise spend on the device, said Hill.
Some people turn to apps
Due to the shortage of devices, some people are turning to oximeter apps instead. But a recent study suggests that apps don’t necessarily work as well – and could even be dangerous.
An analysis from the University of Oxford examined the use of oximeter applications in the context of the Covid-19 pandemic and concluded that they were unreliable.
“The oxygen saturation levels obtained from these technologies should not be reliable,” the authors wrote.
Pulse oximeters measure the 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 said.
Smartphone applications, which typically claim to measure oxygen saturation through flash light and the camera, do not generate as accurate readings because the camera cannot measure the reflection of light at two lengths d ‘wave. One application claimed to use a red light source, but the authors found that it used only one wavelength measurement, making reading inaccurate.
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