Back in March, I thought my sister, Michelle Mendes, was being overly paranoid when she showed up to our house and dropped off a pulse oximeter, a lightweight device used to monitor the amount of oxygen carried in the body. Even though this device was relatively inexpensive, I thought it was a waste of money that we would never use. I couldn’t have been more wrong. Now, I believe a pulse oximeter is priceless because of our family’s recent experience with COVID-19.

My sister and I are concerned with the misconception that COVID-19 comes with a cough and shortness of breath. While at home, our mother, Wilma Ogimi, had no cough and no shortness of breath — but was COVID-19-positive and needed medical care. Her symptoms were slight fever (100 degress and less), body aches and fatigue. She did not present respiratory issues or typical COVID-19 symptoms. Had we waited for her to develop shortness of breath, she may not be with us today. Luckily, before our mother developed any visible apparent respiratory issues, the pulse oximeter told us her oxygen level was abnormally low (88%) and that it was time to head to the emergency room.

We feel it’s important to share what we’ve learned since our mother’s COVID-19 diagnosis. According to Dr. Richard Levitan, an emergency room doctor in New Hampshire who worked with COVID patients in Manhattan, “when COVID pneumonia first strikes, patients don’t feel short of breath, even as their oxygen levels fall. And by the time they do, they have alarmingly low oxygen levels and moderate-to-severe pneumonia.”

COVID patients arriving at hospitals with shortness of breath often need critical care, and sometimes it is too late. This is why early detection of COVID-19 is essential and pulse oximeters are key. “It’s time to get ahead of this virus instead of chasing it,” Levitan wrote in The New York Times (“The Infection That’s Silently Killing Coronavirus Patients,” April 20).

While being treated for COVID pneumonia in the hospital, our mother was told by doctors and nurses that she is lucky to have sought medical care when she did. Early detection of her COVID pneumonia allowed for her to enter the hospital while her lungs were still strong and played a huge part in the efficacy of her treatment. Rather than be in respiratory distress and in need of acute care, she was able to enter the hospital in a stable condition.

We believe in the power of pulse oximeters. Of course, pulse oximeters should not be relied on for diagnostic purposes, but this simple device can help families monitor oxygen levels of sick family members so they can determine when it might be time to seek more medical advice and care.

If you don’t have a pulse oximeter in your household first-aid kit (some smartphones already have a built-in feature but may be less reliable), please go out and buy one today. It’s a small investment that could make all the difference — we believe it saved our mom from COVID-19.

More information on oximeters is available on npr.org, search for “pulse oximeter.”