A T-Shirt That Monitors Breathing Rate

18 May 2017

Looking for a less invasive way to monitor asthma, sleep apnea and chronic pulmonary disease sufferers and to diagnose respiratory illnesses, researchers at Université Laval's Faculty of Science and Engineering and its Center for Optics, Photonics, and Lasers have created a smart T-shirt that monitors a person’s respiratory rate in real time.

The T-shirt works without attaching wires, electrodes and sensors to the body, explains Younes Messaddeq, the professor who led the team that developed the technology.

"The T-shirt is really comfortable and doesn't inhibit the subject's natural movements. Our tests show that the data captured by the shirt is reliable, whether the user is lying down, sitting, standing or moving around."

Detailed in Sensors, an antenna that is made of a hollow optical fiber coated with a thin layer of silver on its inner surface is sewn into the shirt at chest level. The fiber's exterior surface is covered in a polymer that protects it against the environment.

"The antenna does double duty, sensing and transmitting the signals created by respiratory movements," adds Professor Messaddeq. "The data can be sent to the user's smartphone or a nearby computer."

As the user breathes, the smart fiber senses the increase in both thorax circumference and the volume of air in the lungs, explains Messaddeq. "These changes modify some of the resonant frequency of the antenna. That's why the T-shirt doesn't need to be tight or in direct contact with the wearer's skin. The oscillations that occur with each breath are enough for the fiber to sense the user's respiratory rate."

Researchers also measured the durability of the shirt and washed it with the antenna still intact. "After 20 washes, the antenna had withstood the water and detergent and was still in good working condition," said Messaddeq.

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