When we take a breath, our lungs are filled with oxygen, which is delivered to red blood cells for transport throughout the body. Our bodies need large amounts of oxygen to function, and healthy people have an oxygen saturation of at least 95% at all times.
With conditions such as asthma or COVID-19, it is harder for the body to absorb oxygen from the lungs. This causes the oxygen saturation percentage to drop to 90% or lower, indicating the need for medical attention.
In the clinic, doctors monitor oxygen saturation with pulse oximeters - clips that are placed on your fingertip or ear. But monitoring oxygen saturation at home several times a day can help patients keep track of COVID symptoms, for example.
In a pilot study, scientists at the University of California Washington showed that smartphones can detect blood oxygen saturation levels as low as 70%. This is the lowest value that pulse oximeters are required to measure, according to U.S. Food and Drug Administration guidelines.
The results of the study are published in the journal npj Digital Medicine.
Participants in the experiment placed their finger over a smartphone camera and flash, using a special deep-learning algorithm to decipher blood oxygen levels. When the team fed a controlled mixture of nitrogen and oxygen to subjects to artificially lower their blood oxygen levels, the smartphone accurately predicted whether the subject had low blood oxygen levels 80% of the time.