The soft, miniaturised devices were developed by researchers at Northwestern University in Illinois. Stuck to the skin, the devices continuously track internal sounds around the body.
During even the most routine visits, physicians listen to sounds inside their patients’ bodies – air moving in and out of lungs, heart beats and even digested food progressing through the long gastrointestinal tract. These sounds provide valuable information about a person’s health. And when these sounds subtly change or stop, they can signal serious problems that need urgent investigation.
“Currently, there are no existing methods for continuously monitoring and spatially mapping body sounds at home or in hospital settings,” said Northwestern’s John A Rogers, a bioelectronics specialist who led the device 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.”
Containing pairs of high-performance digital microphones and accelerometers, the small, lightweight devices adhere to the skin to create what the researchers called a “comprehensive non-invasive sensing network”. By simultaneously capturing sounds and correlating them with body processes, the devices spatially map how air flows into, through and out of the lungs, as well as how cardiac rhythm changes in varied resting and active states, and how food, gas and fluids move through the intestines.
Encapsulated in silicone, each device measures 40mm long, 20mm wide and 8mm thick. Within that small footprint, they contain a flash memory drive, battery, electronic components, Bluetooth capabilities and two microphones – one facing inward toward the body and another facing outward toward the exterior. By capturing sounds in both directions, an algorithm can separate external sounds and internal body sounds.
“Lungs don't produce enough sound for a normal person to hear,” said Dr Ankit Bharat, who led the clinical research in adult subjects. “They just aren’t loud enough, and hospitals can be noisy places. When there are people talking nearby or machines beeping, it can be incredibly difficult. An important aspect of our technology is that it can correct for those ambient sounds.”
In pilot studies, researchers tested the devices on 15 premature babies with respiratory and intestinal motility disorders and 55 adults, including 35 with chronic lung diseases. The devices performed with clinical-grade accuracy, they said, while also offering new functionalities.
In the study, premature babies wore sensors at four locations across their abdomen. Early results aligned with measurements of adult intestinal motility using wire-based systems, which is the current standard of care.
In the tests with adult patients, the devices captured the distribution of lung sounds and body motions at various locations simultaneously, enabling researchers to analyse a single breath across different regions in the lungs.
“As physicians, we often don’t understand how a specific region of the lungs is functioning,” Dr Bharat said. “With these wireless sensors, we can capture different regions of the lungs and assess their specific performance and each region’s performance relative to one another.”
The study was published in Nature Medicine.
Want the best engineering stories delivered straight to your inbox? The Professional Engineering newsletter gives you vital updates on the most cutting-edge engineering and exciting new job opportunities. To sign up, click here.
Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.