Respiratory diseases such as COVID-19 affect the body’s ability to draw oxygen from the lungs, requiring frequent monitoring of patients’ blood oxygen levels. New research now suggests that people could track these levels at home with their smartphones.
Normally, blood oxygen saturation is monitored using a device known as a pulse oximeter, which is attached to either a finger or the lobe of the ear. These tools are typically used and monitored by trained technicians in hospitals or clinics. Smartphone-connected oximeters do exist, but they are another item that home users would need to purchase.
Looking for a simpler and less expensive alternative, scientists from the University of Washington and the University of California – San Diego developed an experimental app. They started with six volunteers ranging in age from 20 to 34 – three men, three women, one of whom was African American and the rest Caucasian.
To train the deep-learning-based algorithm used by the app, four of these subjects wore a standard oximeter on one finger and placed another finger on the same hand over a smartphone’s camera lens and flash. Over a period of 15 minutes, they breathed a mixture of oxygen and nitrogen to slowly lower their blood oxygen levels.
As they did so, the phone recorded a flashlit video of the blood pulsing into her finger. The app continuously analyzed how much light in the green, red and blue color channels was absorbed by the blood. The amount absorbed varied with the amount of oxygen in their blood.
When the blood oxygen readings obtained from the oximeter were compared to the light intensity readings from the phone, it was possible to determine which specific readings corresponded to which specific light readings. The app was therefore able to use the amount of light absorbed to learn how much oxygen was present in the blood at a certain point in time through the blood.
When the app was then tested on all six volunteers, it was found to be able to measure blood oxygen levels up to 70%, which is the lowest level that commercial oximeters are required to measure. In contrast, a healthy person should have a blood oxygen level of at least 95% and usually need medical attention if this falls below 90%.
In its current form, the app is able to accurately detect low levels 80% of the time. It is believed that this number should improve significantly as technology advances, which will involve training the app on a much larger dataset.
“That way, you could take multiple measurements with your own device, either for free or at low cost,” said Dr. Matthew Thompson of the University of Washington, co-author of a paper on the research. “In an ideal world, this information could be seamlessly transmitted to a doctor’s office. This would be very beneficial for telemedicine appointments or for triage nurses to be able to quickly determine if patients need to go to the ER or can continue to go. “Rest at home.”
The paper was recently published in the journal npj Digital medicine.
Source: University of Washington