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"When you hear the word oximeter, you remember the name of blood oxygen sensors, rigid and bulky finger-clamp sensors," said Yasser Khan, a graduate student in Electrical Engineering and Computer Science at the University of Berkeley. "We wanted to break with that and show that oximeters can be light, thin and flexible."
"All medical applications using oxygen monitoring could benefit from a portable sensor," said Ana Claudia Arias, professor of electrical engineering and computer science at the University of Berkeley. "Patients with diabetes, respiratory diseases and even sleep apnea could use a sensor that could be worn anywhere to monitor blood oxygen levels 24/7." / 7. "
Existing oximeters use light-emitting diodes (LEDs) to shine the red and near-infrared light through the skin and then detect the amount of light scattered on the other side. Oxygen-rich red blood absorbs more infrared light, while darker, oxygen-poor blood absorbs more red light. By examining the transmitted light ratio, the sensors can determine the amount of oxygen in the blood.
These oximeters only work on partially transparent body areas, such as fingertips or ear lobes, and can only measure the rate of oxygen in the blood at a single point in the body.
"The thicker regions of the body, such as the forehead, arms and legs, barely let in visible light or in the near infrared, which makes the measurement of oxygenation at these places really difficult," Khan said.
In 2014, Arias and a team of graduate students showed that printed organic LEDs could be used to create thin, flexible oximeters for fingertips or ear lobes. Since then, they have pushed their work further, developing a way to measure tissue oxygenation using reflected light rather than transmitted light. The combination of these two technologies allows them to create the new portable sensor capable of detecting oxygen levels in the blood anywhere on the body.
The new sensor consists of a set of alternating red and quasi-infrared organic LEDs and organic photodiodes printed on a flexible material. The team used the sensor to track the overall level of oxygen in the forehead blood of a volunteer who was breathing in air with progressively lower concentrations of oxygen – such as during a climb to altitude – and found that it was consistent with those using a standard oximeter. They also used the sensor to map the levels of oxygen in the blood in a three by three grid on the forearm of a volunteer wearing an armband.
"After transplantation, surgeons want to measure that all parts of an organ are receiving oxygen," Khan said. "If you have a sensor, you have to move it to measure the oxygenation in different places.With a chart, you can know right away if there is a point that is not healing properly."
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