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Smartphone app can measure blood oxygen levels with 80% accuracy

No oximeter? Do not worry! Smartphone app can measure blood oxygen levels with 80% accuracy by shining the phone’s flash through your finger, study finds

  • Blood oxygen levels are currently measured with a pulse oximeter
  • But this makes it difficult to test blood oxygen levels on the go
  • Scientists have developed an app that uses the phone’s camera and flash
  • In tests, it was shown to detect low oxygen levels in the blood with an accuracy of 80%

From asthma to Covid-19, a variety of conditions can require regular blood oxygen measurements.

Currently, these measurements are taken with a pulse oximeter — a device that clips onto your fingertip or ear — although this can make testing on the go tricky.

Hoping to make the process easier, scientists have developed a smartphone app that uses the device’s camera and flash to measure blood oxygen levels.

During testing, researchers from the University of Washington and the University of California at San Diego showed that a smartphone can detect blood oxygen saturation up to 70 percent — the lowest value pulse oximeters should be able to measure.

Scientists have developed a smartphone app that uses the device's camera and flash to measure blood oxygen levels

Scientists have developed a smartphone app that uses the device’s camera and flash to measure blood oxygen levels

What is a pulse oximeter?

A pulse oximeter measures how much light is absorbed by your blood.

This tells us how much oxygen your blood contains.

The pulse oximeter shines 2 lights through your fingertip or earlobe: a red light and an infrared light.

Blood with a lot of oxygen absorbs more infrared light and lets more red light through.

Blood without enough oxygen absorbs more red light and lets more infrared light through.

If your blood cells don’t have enough oxygen, they will appear bluer.

Source: British Lung Foundation

The system involves the user placing their finger on the smartphone’s camera and flashing it before a video is captured.

An in-depth learning algorithm can then decipher the oxygen levels in the blood based on the images.

To put it to the test, the researchers recruited six participants, ages 20 to 34.

Each participant wore a standard pulse oximeter on one finger and then placed another finger on the same hand over a smartphone’s camera and flash.

“The camera records a video: every time your heart beats, fresh blood flows through the part illuminated by the flash,” says senior author Edward Wang.

‘The camera registers how much that blood absorbs the light from the flash in each of the three color channels it measures: red, green and blue.

‘Then we can enter those intensity measurements into our deep learning model.’

Over the course of 15 minutes, each participant breathed in a controlled mix of oxygen and nitrogen to slowly lower their oxygen levels.

The results showed that the smartphone correctly predicted 80 percent of the time whether the subject had low oxygen levels in the blood.

The researchers hope to continue the research by testing the algorithm on more people.

Each participant wore a standard pulse oximeter on one finger, then placed another finger on the same hand over a smartphone's camera and flash.

Each participant wore a standard pulse oximeter on one finger, then placed another finger on the same hand over a smartphone’s camera and flash.

Huawei unveils a £400 wearable device that can take your blood pressure by inflating around your wrist

Huawei has launched a smartwatch that inflates on the wrist to take accurate blood pressure readings, much like a cuff on the arm at a doctor’s office.

The Huawei Watch D has an airbag on the inside of the band that slowly inflates around your wrist.

Blood pressure is a critical indicator of overall health, but when taken by the doctor it can be altered by something known as the ‘white coat’ effect, where the blood pressure rises slightly when we are at the doctor.

“One of our subjects had thick calluses on their fingers, which made it more difficult for our algorithm to accurately determine the oxygen level in their blood,” said Jason Hoffman, co-lead author of the study.

‘If we expanded this study to more subjects, we would probably see more people with calluses and more people with different skin colors.

‘Then we may have an algorithm with sufficient complexity to better model all those differences.’

The researchers emphasize how almost everyone has a smartphone these days.

“This way you can take multiple measurements with your own device, for free or at a low cost,” said Dr Matthew Thompson, co-author of the study.

‘In an ideal world, this information could be passed on seamlessly to a doctor’s office.

“For telemedicine appointments or for triage nurses, this would be very useful to quickly determine whether patients need to go to the emergency room or whether they can rest at home and make an appointment with their GP later.”

The study comes shortly after Huawei launched a smartwatch that inflates on the wrist to take accurate blood pressure readings, much like a cuff on the arm at a doctor’s office.

The new Huawei Watch D has an airbag on the inside of the band that slowly inflates around your wrist.

Blood pressure is a critical indicator of overall health, but when taken by the doctor it can be altered by something known as the “white coat” effect.

This is where the blood pressure rises slightly when we are at the doctor, because of the slight increase in anxiety from being in a clinical setting.

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