Microphone-Packing Miniature Wearables Show Promise for Non-Invasive Continuous Health Monitoring

Researchers from Northwestern University, Hanyang University ERICA, the McGill University Health Center, the Korea Advanced Institute of Science and Technology, Dankook University, the University of California, Davis, Kyung Hee University, and the Adlai E. Stevenson High School have developed a wearable which tracks the health of its user by listening to their body — literally.

“Currently, there are no existing methods for continuously monitoring and spatially mapping body sounds at home or in hospital settings," says Northwestern Engineering's John A. Rogers, who led the device's development.

"Physicians have to put a conventional, or a digital, stethoscope on different parts of the chest and back to listen to the lungs in a point-by-point fashion. In close collaborations with our clinical teams, we set out to develop a new strategy for monitoring patients in real-time on a continuous basis and without encumbrances associated with rigid, wired, bulky technology."

The system developed by the researchers takes the form of soft, wearable devices which can be gently stuck to the skin of a patient to be monitored — including premature babies, 15 of which made up a test group with 55 adults. Operating continuously, the devices pick up sounds generated by the body — primarily, though not exclusively, the lungs — using digital microphones coupled with accelerometers to track movement.

"The idea behind these devices is to provide highly accurate, continuous evaluation of patient health and then make clinical decisions in the clinics or when patients are admitted to the hospital or attached to ventilators," thoracic surgeon Ankit Bharat explains.

"A key advantage of this device is to be able to simultaneously listen and compare different regions of the lungs. Simply put, it’s like up to 13 highly trained doctors listening to different regions of the lungs simultaneously with their stethoscopes, and their minds are synced to create a continuous and a dynamic assessment of the lung health that is translated into a movie on a real-life computer screen."

The team did have one key problem to solve in the design: external sounds. As any parent knows, when a baby is sick it has a tendency to cry — and that crying would drown out the subtler sounds of its body's breathing. Add in ambient noises in a hospital setting — other children, alarms, machines — and you've got bad data. The solution: giving each sensor a pair of microphones, one facing inwards and one facing outwards, then using the ambient sound recording to cancel out noise on the body-facing microphone.

The wearables have been tested in a clinical setting, successfully tracking both breathing and digestion in adults and children and showing promise for better, more detailed, and less invasive health monitoring for a range of conditions. "Lungs can make all sorts of sounds, including crackling, wheezing, rippling, and howling," Bharat explains.

"It's a fascinating microenvironment. By continuously monitoring these sounds in real time, we can determine if lung health is getting better or worse and evaluate how well a patient is responding to a particular medication or treatment. Then we can personalize treatments to individual patients."

The team's work has been published in the journal Nature Medicine under open-access terms.