Currently, if you want to measure someone's blood oxygen levels, you have to use one of those oximeters that clips onto their finger. An experimental new system, however, is able to check those levels anywhere on the body – and that could mean big things for the field of medicine.

Traditional oximeters use LEDs to shine red and near-infrared light through the skin on one side of a translucent part of the body, typically a fingertip or an ear lobe. Lighter-colored oxygen-rich blood absorbs much of the infrared light, while darker oxygen-poor blood absorbs much of the red light. Therefore, by analyzing the ratio of the two types of light that make it through to the other side of the body part, the oximeter is able to determine the blood oxygen levels.

As mentioned, though, there are only a few places on the body where such devices can be used.

In 2014, a team of grad students at the University of California Berkeley created thin, flexible oximeters incorporating printed organic LEDs. More recently, they also developed a method of determining blood oxygen levels by analyzing light that's reflected back from the blood, as opposed to passing through it. Those two technologies have now been combined in the new system.

It incorporates a multi-point grid array of alternating red LEDs, near-infrared LEDs and photodiodes, all of which are printed onto a flexible plastic sheet. That array can then be placed on any part of the body, where it will shine the two types of light down through the skin, analyzing the amounts of both that are reflected back out.

So far, prototypes have successfully been used to measure blood oxygenation levels on the forearm of one volunteer, and on the forehead of another. In the latter case, the participant breathed air with progressively lower concentrations of oxygen, causing the concentrations in his blood to drop accordingly – the flexible oximeter was found to measure those changing levels just as accurately as a traditional fingertip-mounted model.

It is now hoped that once developed further, the technology could be used for things such as mapping oxygenation within skin grafts, or monitoring oxygen levels in transplanted organs.

"All medical applications that use oxygen monitoring could benefit from a wearable sensor," says Prof. Ana Claudia Arias, who led the study. "Patients with diabetes, respiration diseases and even sleep apnea could use a sensor that could be worn anywhere to monitor blood-oxygen levels 24/7."

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