Doctors say one of the best ways to monitor patients with COVID-19 is by tracking their blood oxygen levels, which can show when they have dangerous breathing problems — even if they don’t feel short of breath.
With the devices out of reach, people are turning to questionable alternatives: the third most popular paid iPhone app last week claims to be able to measure blood oxygen levels through the phone’s camera, despite a disclaimer that says the app is not a medical device.
Apps don’t work well because most use a different mechanism to test blood oxygen levels than standard, medical pulse oximetry devices. The devices send two different wavelengths of light — usually red and infrared — through a fingertip, where there’s lots of blood close to the surface of the skin.
Some models of Fitbit and Garmin smartwatches also have pulse oximetry features. Fitbit can track oxygen level trends during sleep, and Garmin can give on-the-spot readings. Their watches do use red light, but they use the less-accurate reflective method. They also take readings from blood flow at the wrist — which isn’t as strong as it is at the finger.
See Apps aren’t a reliable way to measure blood oxygen levels
Don’t download an app if pulse oximeters are sold out in your area