Pajamas monitor heart rate, breathing while person sleeps

Pajamas monitor heart rate, breathing while person sleeps
Fabric-based pressure sensor combined with a triboelectric sensor. (University of Massachusetts Amherst/Andrew Lab)

Pajamas may never be the same.

Wearable technology to monitor health parameters is progressing beyond patches and watches, possibly to the pajamas you sleep in. Researchers at the University of Massachusetts Amherst have developed physiological-sensing textiles that can be woven or stitched into sleep garments dubbed “phyjamas.” The “phyjamas” can incorporate sensing circuitry to monitor heart rate,  respiratory rate, and other health parameters.

University of Massachutsetts graduate students Ali Kiaghadi and S. Zohreh Homayounfar, with their professors Trisha L. Andrew, a materials chemist, and computer scientist Deepak Ganesan, presented their research at the Ubicomp 2019 conference this week in London, U.K. A paper detailing the work will be published in the Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies (IMWUT).

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Because sleepwear is loosely worn, designing material with reliable sensors that would not interfere or cause discomfort to the wearer challenged the researchers. 

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“The challenge we faced was how to obtain useful signals without changing the aesthetics or feel of the textile,” said Andrew. “Generally, people assume that smart textiles refer to tightly worn clothing that has various sensors embedded in it for measuring physiological and physical signals, but this is clearly not a solution for everyday clothing and, in particular, sleepwear.”

Ganesan added, “Our insight was that even though sleepwear is worn loosely, there are several parts of such a textile that are pressed against the body due to our posture and contact with external surfaces. Such pressured regions of the textile are potential locations where we can measure ballistic movements caused by heartbeats and breathing,” he explained, “and these can be used to extract physiological variables.”

The scientists went on the notion that obtaining accurate data on medical conditions would not be accomplished through readings from a few sensors, but rather analyzing signals from sensors distributed across the body.

Andrew, Ganesan and colleagues designed a new fabric-based pressure sensor and combined that with a triboelectric sensor—one activated by a change in physical contact—to develop a distributed sensor suite that could be integrated into loose-fitting clothing like pajamas. They also developed data analytics to fuse signals from many points that took into account the quality of the signal coming in from each location.

The authors said this sensor configuration enabled them to detect physiological signals across many different postures. They conducted multiple user studies in both controlled and natural settings and showed that they can extract heartbeat peaks with high accuracy, breathing rate with less than one beat per minute error, and perfectly predict sleep posture.

“We expect that these advances can be particularly useful for monitoring elderly patients, many of whom suffer from sleep disorders,” said Andrew. “Current-generation wearables, like smartwatches, are not ideal for this population, since elderly individuals often forget to consistently wear or are resistant to wearing additional devices, while sleepwear is already a normal part of their daily life.”

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