Smartphones are already capable of some health-focused tricks. From counting steps and tracking sleep to measuring heart rate and breathing rate, having a phone in your pocket is a pretty powerful health monitoring machine. Now a team of scientists at the University of Washington wants to add blood oxygen measurement to this set of tricks.
In an article published in NJP Digital Medicine, the team details what it calls “the first validation of the clinical development of a smartphone camera-based SpO2 measurement system.” Simply put, the team developed an algorithm and proved that smartphones can measure blood oxygen saturation levels up to the same baseline that is approved by the Food and Drug Administration (FDA) for over-the-counter pulse oximeters.
For reference, the agency recommends that a pulse oximeter be able to measure SpO2 levels up to 70%. In a study involving six volunteers, the team proved that blood oxygen levels of at least 70% can be measured with nearly 80% accuracy by simply placing a finger on a smartphone’s camera and a nearby flash.
The latest breakthrough transcends two critical issues. First, this method does not require the user to hold their breath. Secondly, previous smartphone-based SpO2 measurement methods could only measure the lower limit of 85%, but the new algorithmic method developed by scientists can reach the same baseline as medical pulse oximeters.
The technique used here is not too different from what the SpO2 sensors do in smartwatches such as the Apple Watch Series 8 and Samsung Galaxy Watch 5. When the flash illuminates the path of blood moving through the vessels, the light absorption rate changes, and these changes are then processed with using a special algorithm to measure the level of oxygen saturation in the blood.
The future of health monitoring, phone-centric
“Our data shows that smartphones can perform well right in the range of critical thresholds,” notes co-author Jason Hoffman. One of the biggest benefits of using smartphones to measure blood oxygen saturation levels is their affordability. Also, this method does not rely on a fancy multi-camera setup or special hardware. All it needs is a camera sensor located next to the LED flash on the back.
It is also much easier to send SpO2 data to a medical examiner from a smartphone than to take a measurement on a smart watch, pair it with a phone via a companion app, sync the data, and then transfer it. Keeping an eye on your SpO2 levels is essential these days as we live in a world affected by COVID-19.
The team has opened the entire dataset so that other stakeholders can expand on it. This is again important because the study used data collected from only six people, five of whom were of Caucasian descent and only one of whom was of African ancestry.
More diversity and a wider network of volunteers are needed to fine-tune the basic system and make smartphone-based SpO2 measurements more accurate and fair. Smartwatches like the Apple Watch have already shown vulnerability to errors when it comes to people of color or people with tattoos and obese body types.