This spring, our daughter insisted that my husband and I, both in our 60s, get the latest weapon in the fight against the novel coronavirus: the pulse oximeter, a device that can measure the level of oxygen in the blood.

Recent reports have shown that a lower-than-healthy level of oxygen saturation in the blood can be an early predictor of covid-related pneumonia, even in those with mild symptoms.

My oxygen saturation was 91.

“Values under 90 percent are considered low” for oxygen saturation, according to the Mayo Clinic’s online site.

This time the reading said my oxygen saturation level was 71.

I took my oxygen level again — again and again.

That’s why having that reading in their arsenal is another useful measure.

The instructions that came with the Zacurate Pro Series 500DL Fingertip Pulse Oxygen Saturation Monitor ($35.95, but seemingly out of stock on Amazon) mainly concerned how to put in the two AAA batteries.

Some people suggested I use my middle finger, not pointer, and insert it palm side up to get a better reading.

She treats people who come into the hospital’s emergency room and often makes decisions about admittance based on how low their oxygen levels are.

Having a pulse oximeter at home is a good idea for people who suspect they might have the coronavirus.

“We’re seeing a lot of people coming in [to the emergency room] feeling lousy, when their oxygen level is normal,” she says.

That means extraneous trips to the hospital, and potential exposure to illnesses, including the coronavirus among people who are truly sick.

For people who are healthy but worried that they might get sick, constant testing with a pulse oximeter is not necessarily a great plan, she adds.

Panagis Galiatsatos, a pulmonary and critical care doctor at Johns Hopkins Hospital in Baltimore, also says that while having a pulse oximeter at home is a useful device for patients with chronic obstructive pulmonary disease, or other lung disease, it could be misread by those who are not using it properly or don’t know how to interpret it in the context of their medical condition.

You don’t want people “going in negative and coming out positive” for the coronavirus.

Patti Geary Kessel, a retired nurse who now lives in Florida, says that when she worked as a high school nurse, she used a pulse oximeter for the asthmatic students who came into her office.

For healthy people, she says, it could be useful if they measure their oxygen level to get a baseline before they feel sick.

Healthy people who suddenly get a reading in the 80s would probably feel short of breath, she says.

As for me, I took my reading daily for a few weeks after I got the meter.

When my husband, 69, took his, he got a reading of 100?