When my daughter returned to school this fall, I sent a care package that was perfect for a college student going through a pandemic. It contained cookies, a coffee mug – and a pulse oximeter.
A pulse oximeter is a small device that attaches to your finger and measures your blood oxygen levels. Although my daughter and her friends are all vaccinated against Covid-19, I wanted her to have the device handy in case she got a breakthrough infection.
Many people first learned about a pulse oximeter in the early days of the pandemic after doctors warned that some patients with Covid-19 develop a form of oxygen starvation called “silent hypoxia,” which occurs when blood oxygen levels are so slow decreases that a patient does not notice that something is wrong. Often these patients are already so sick in the hospital that they have to be connected to a ventilator.
New research from South Africa shows that using a pulse oximeter to check oxygen levels after a Covid diagnosis really saves lives. For the study, 8,115 high-risk patients were given a pulse oximeter for use at home after being diagnosed with Covid-19. The study focused on patients at the highest risk, including the elderly, pregnant women, or those with chronic conditions such as heart disease, high blood pressure, or diabetes.
After a Covid diagnosis, patients were given a pulse oximeter and a follow-up call to make sure they were using it properly. They were asked to record their oxygen saturation and heart rate twice a day and call a doctor if the reading fell below 95 percent.
If the reading fell below 90 percent, they were directed to go to the emergency room. And all patients were told to seek emergency care if they had difficulty breathing, regardless of the number on the device.
The study group was then compared to approximately 30,000 patients in the general population who were examined by doctors nationwide between March and October 2020. During the study period, 544 people (out of 38,660 patients) died of Covid-19, including 49 in the study group.
But the risk of death was 52 percent lower for those patients who were instructed to monitor their oxygen at home. Based on the overall mortality rate, 95 people in the study group were expected to have died. But using a pulse oximeter appears to have saved the lives of 46 people.
“I think it’s important to know that a pulse oximeter makes a difference,” said Shirley Collie, author of the new study and chief actuary for health analysis at Discovery Health, a major managed care administrator in South Africa. “You monitor your oxygen because when you get to the hospital has a huge impact on your clinical outcome.”
The magnitude of the benefits stunned even some of the most staunch proponents of home oxygen monitoring. Dr. Richard Levitan, an ambulance who raised the alarm about silent hypoxia in a guest article for The Times, called the results “amazing”.
“It is extremely rare in medicine to show such a big difference in treatment, especially with such a complicated disease,” said Dr. Levitan, who practices at Littleton Regional Healthcare in New Hampshire. “All of this happened with different management in different hospitals as the pandemic unfolded. A 50 percent mortality difference is phenomenal. We almost never see such a great benefit. “
The researchers said the difference in mortality between the two groups seemed to be explained by people who monitored their oxygen levels at home, seeking medical attention earlier as their illness progressed. Among the patients who went to the hospital, those who used a pulse oximeter at home had lower levels of inflammation as measured by a C-reactive protein (CRP) test.
Not only can a pulse oximeter help patients see a doctor, but it can also reduce anxiety after a Covid-19 diagnosis. Ms. Collie said she experienced the benefits firsthand after suffering a breakthrough infection this summer, despite being fully vaccinated with the Johnson & Johnson vaccine. She had a cough and chest tightness and regularly monitored her home oxygen levels. “There’s a lot of convenience when it comes to checking where you are,” she said. “This monitoring can change your risk of a really bad result. I think it’s enormously invigorating. “
To use a pulse oximeter, press down on the device like a clip or clothespin and place your finger firmly in it. The device emits light of different wavelengths through your finger. It targets hemoglobin, a protein molecule in your blood that carries oxygen. Your pulse oximeter will show you a numeric value – a percentage that indicates the level of oxygen saturation in your blood. Within seconds, it will light up with numbers showing your blood oxygen levels and heart rate.
Most healthy people get 95 to 99 percent oxygen levels. Some people with existing health problems may have a lower normal score. In general, doctors say that if the number drops quickly or drops below 94, you should seek medical advice.
However, the accuracy of the device may vary, especially for patients with dark skin. One study found that the result was incorrect in 1 in 10 black patients. A person with dark skin can still use the device, but doctors say it’s important to watch out for any downward trend in oxygen levels rather than fixate on a specific number. If you have Covid-19 at home and your normal reading drops by four points or more, that’s a good reason to see your doctor. Dark nail polish can also interfere with reading.
The South Africa study was conducted before vaccines were available and people who have been vaccinated have a far lower risk of becoming seriously ill or hospitalized because of Covid-19. However, some vaccinated people, especially those in high-risk groups, can still develop serious illnesses. Dr. Levitan said you should use a pulse oximeter after a diagnosis of Covid-19, even if you are vaccinated and at low risk of developing serious illness.
“Your chances of getting seriously ill are slim, but I have hospitalized patients with Covid pneumonia who have been vaccinated,” said Dr. Levitan. “Throughout medicine, people with previous treatment are better off. If you come early and spend three to five days in the hospital, that is very different from being late and ending up in the intensive care unit. “