September 19, 2022
This technique involves having participants place their fingers on the camera and smartphone flash, which uses a deep learning algorithm to decode blood oxygen levels from blood flow patterns in the resulting video.Dennis Wise/University of Washington
First, stop and take a deep breath.
When we breathe, our lungs are filled with oxygen, which is distributed to our red blood cells to travel throughout our bodies. Our bodies need a lot of oxygen to function, and healthy people have at least 95% oxygen saturation all the time.
Conditions such as asthma or COVID-19 make it difficult for the body to absorb oxygen from the lungs. This drops oxygen saturations to 90% or less, which is an indication that medical attention is needed.
In the clinic, doctors monitor oxygen saturation using pulse oximeters — those clips you place on the tip of your finger or ear. But monitoring oxygen saturation at home several times a day can happen Helping patients monitor symptoms of COVIDfor example.
In a proof-of-principle study, researchers from the University of Washington and the University of California San Diego demonstrated that smartphones are able to detect blood oxygen saturation levels up to 70%. This is the lowest value a pulse oximeter should be able to measure, as recommended by the U.S. Food and Drug Administration.
This technique involves participants placing their finger on a camera and smartphone flash that uses a deep learning algorithm to decode oxygen levels in the blood. When the team administered a controlled mixture of nitrogen and oxygen to six people to artificially lower blood oxygen levels, the smartphone correctly predicted whether the person had low blood oxygen levels 80% of the time.
the team Post these results september 19 in digital medicine npj.
“Other smartphone apps have been developed that do this by asking people to hold their breath. People feel very uncomfortable and have to breathe after a minute or so, before their blood oxygen levels drop enough to represent the full range,” said the co-lead author. for clinically relevant data.” Jason Hoffman, who is a UW doctoral student at the Paul G. Allen School of Computer Science and Engineering. “With our testing, we can collect 15 minutes of data from each subject. Our data shows that smartphones can perform well within the critical threshold range.”
One way to measure oxygen saturation is to use pulse oximeters – those little clips you put on the tip of your finger (some shown here in gray and blue).Dennis Wise/University of Washington
Another benefit of measuring blood oxygen levels on a smartphone is that almost everyone has one.
“This way you can get multiple measurements using your own device either at no cost or at low cost,” said one of the co-authors. Dr. Matthew Thompson, professor of family medicine at the University of Washington School of Medicine. “In an ideal world, this information could be seamlessly transmitted to the doctor’s office. This would be really useful for telemedicine appointments or for triage nurses so they can quickly determine if patients need to go to the emergency department or if they can continue to rest at home And make an appointment with your primary care provider at a later time.”
The team recruited six participants, ages 20 to 34. Three of them were identified as female, and three were identified as male. One participant was identified as African American, while the rest were identified as Caucasian.
To collect data to train and test the algorithm, the researchers asked each participant to wear a standard pulse oximeter with one finger and then place another finger on the same hand on a smartphone camera and flash. Each participant has the same setting on both hands simultaneously.
“The camera records a video: every time your heart beats, new blood flows through the part that the flash lights up,” said one of the senior authors. Edward Wangwho started this project as a PhD student at the University of Washington studying electrical and computer engineering and is now an assistant professor at the University of California, San Diego. design lab Department of Electrical and Computer Engineering.
Wang said, who also directs UCSD DigiHealth . Laboratory. “Then we can enter these density measurements into our deep learning model.”
Each participant breathes in a controlled mixture of oxygen and nitrogen to slowly reduce oxygen levels. The process took about 15 minutes. For all six participants, the team took more than 10,000 readings of a blood oxygen level between 61% and 100%.
The researchers used data from four participants to train a deep-learning algorithm to pull oxygen levels in the blood. The rest of the data was used to validate the method and then tested to see how well it performed on the new subjects.
co-author said Varun Viswanath, a UW graduate and now a doctoral student advised by Wang at the University of California, San Diego. “Deep learning is a really useful technique here because it can see these really complex and subtle features and help you find patterns that you wouldn’t be able to see otherwise.”
The team hopes to continue this research by testing the algorithm on more people.
“One of our team members had thick nails on his fingers, which made it difficult for our algorithm to accurately determine blood oxygen levels,” Hoffman said. “If we expand this study to more subjects, we are likely to see more people with corns and more people with different skin types. And then we can have an algorithm with enough complexity to be able to better model all of these differences.”
But the researchers said this is a good first step toward developing biomedical devices aided by machine learning.
“It is very important to do a study like this,” Wang said. “Traditional medical devices are subjected to rigorous testing. But computer science research is just in its infancy using machine learning to develop biomedical devices and we are all still learning. By forcing ourselves to be strict, we are forcing ourselves to learn how to do things properly” .
Additional co-authors are Xinyi DingPhD student at Southern Methodist University. Eric LarsonAssociate Professor of Computer Science at Southern Methodist University; Kaiwei Tian, who completed this research as a UW undergraduate student; And the Shwetak Patel, a UW professor in both the Allen School and the Department of Electrical and Computer Engineering. This research was funded by the University of Washington. The researchers applied for a patent covering SpO2 classification systems and methods using smartphones (application number: 17/164,745).
For more information, contact Hoffman at jasonhof@cs.washington.edu, Wang at ejaywang@eng.ucsd.edu, and Viswanath at varunv9@eng.ucsd.edu. For questions specifically directed at Matthew Thompson, please contact Lila Gray at leilag@uw.edu.
tag(s): College of Engineering • COVID-19 • Department of Electrical and Computer Engineering • Department of Family Medicine • Jason Hoffman • Matthew Thompson • Paul G. Allen School of Computer Science and Engineering • medical school • Shwetak Patel
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