During even the most routine visits, physicians listen to sounds inside their patients’ bodies - air moving in and out of the lungs, heartbeats, and even digested food progressing through the long gastrointestinal tract. These sounds provide valuable information about a person’s health. When these sounds subtly change or downright stop, it can signal a serious problem that warrants time-sensitive intervention.
Now, Northwestern University researchers are introducing new soft, miniaturized wearable devices that go well beyond episodic measurements obtained during occasional doctor exams. Softly adhered to the skin, the devices continuously track these subtle sounds simultaneously and wirelessly at multiple locations across nearly any region of the body.
The new study was published in the journal Nature Medicine.
In pilot studies, researchers tested the devices on 15 premature babies with respiratory and intestinal motility disorders and 55 adults, including 20 with chronic lung diseases. Not only did the devices perform with clinical-grade accuracy, but they also offered new functionalities that have not been developed nor introduced into research or clinical care, reports Northwestern University.
“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 pioneer 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.”
“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,” said Dr. Ankit Bharat, a thoracic surgeon at Northwestern Medicine, who led the clinical research in the adult subjects. “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 dynamic assessment of lung health that is translated into a movie on a real-life computer screen.”
Comprehensive, non-invasive sensing network
Containing pairs of high-performance, digital microphones and accelerometers, the small, lightweight devices gently adhere to the skin to create a comprehensive non-invasive sensing network. By simultaneously capturing sounds and correlating those sounds to 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.
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Encapsulated in soft silicone, each device measures 40 millimeters long, 20 millimeters wide, and 8 millimeters thick. Within that small footprint, the device contains a flash memory drive, tiny battery, electronic components, Bluetooth capabilities, and two tiny 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 (ambient or neighboring organ) sounds and internal body sounds.
Not only does capturing ambient noise enable noise canceling, but it also provides contextual information about the patients’ surrounding environments, which is particularly important when treating premature babies.
Non-obtrusively monitoring babies’ breathing
In collaborative studies conducted at the Montreal Children’s Hospital in Canada, healthcare workers placed the acoustic devices on babies just below the suprasternal notch at the base of the throat. Devices successfully detected the presence of airflow and chest movements and could estimate the degree of airflow obstruction with high reliability, therefore allowing the identification and classification of all apnea subtypes.
“When placed on the suprasternal notch, the enhanced ability to detect and classify apneas could lead to more targeted and personalized care, improved outcomes, and reduced length of hospitalization and costs,” said Dr. Wissam Shalish, a neonatologist at the Montreal Children’s Hospital and co-first author of the paper. “When placed on the right and left chest of critically ill babies, the real-time feedback transmitted whenever the air entry is diminished on one side relative to the other could promptly alert clinicians of a possible pathology necessitating immediate intervention.”
Tracking infant digestion
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.
“When placed on the abdomen, the automatic detection of reduced bowel sounds could alert the clinician of an impending (sometimes life-threatening) gastrointestinal complication,” Shalish said. “While improved bowel sounds could indicate signs of bowel recovery, especially after a gastrointestinal surgery.”
Mapping a single breath
Accompanying the NICU study, researchers tested the devices on adult patients, which included 35 adults with chronic lung diseases and 20 healthy controls. In all subjects, the devices captured the distribution of lung sounds and body motions at various locations simultaneously, enabling researchers to analyze a single breath across a range of regions throughout the lungs.
“Lungs can make all sorts of sounds, including crackling, wheezing, rippling, and howling,” Bharat said. “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.”
