A new app uses a paper funnel and your phone’s microphone and speaker to detect fluid behind the eardrum, a sign of ear infections in children.
Ear infections are the most common reason that parents bring their children to a pediatrician, according to the National Institutes of Health. The condition occurs when fluid builds up in the middle ear behind the eardrum and becomes infected.
The fluid buildup, also common in another condition called otitis media with effusion, can cause pain and make it hard for children to hear, especially detrimental when they are learning to talk.
Both conditions are hard to diagnose because they have vague symptoms: Sometimes children tug on their ears or have fevers, and sometimes there are no symptoms. In addition, young children may not be able to describe where they hurt.
See the doctor?
With the new app, the smartphone makes a series of soft audible chirps into the ear through a small paper funnel. Depending on the way the chirps reflect back to the phone, the app determines the likelihood of fluid present with a probability of detection of 85 percent. That’s on par with current methods that specialists use to detect fluid in the middle ear, which involve specialized tools using acoustics or a puff of air.
“Designing an accurate screening tool on something as ubiquitous as a smartphone can be game changing for parents as well as health care providers in resource limited regions,” says coauthor Shyam Gollakota, an associate professor in the University of Washington’s Paul G. Allen School of Computer Science & Engineering.
“A key advantage of our technology is that it does not require any additional hardware other than a piece of paper and a software app running on the smartphone.”
Once diagnosed, ear infections are easy to treat with observation or antibiotics. Doctors can monitor or drain persistent fluid to relieve symptoms of pain or hearing loss. A quick screening at home could help parents decide whether or not they need to take their child to the doctor.
Sound waves and chirps
The app sends sounds into the ear and measures how those sound waves change as they bounce off the eardrum. The new method involves a smartphone and a regular piece of paper that a doctor or parent can cut and fold into a funnel.
The funnel rests on the outer ear and guides sound waves in and out of the ear canal. When the phone plays a continuous 150 millisecond sound—which sounds like a bird chirping—through the funnel, the sound waves bounce off the eardrum, travel back through the funnel. The phone’s microphone then picks up the sound waves along with the original chirps. Depending on whether there’s fluid inside, the reflected sound waves interfere with the original chirp sound waves differently.
“It’s like tapping a wine glass,” says co-first author Justin Chan, a doctoral student in the Allen School. “Depending on how much liquid is in it, you get different sounds. Using machine learning on these sounds, we can detect the presence of liquid.”
When there is no fluid behind the eardrum, the eardrum vibrates and sends a variety of sound waves back. These sound waves mildly interfere with the original chirp, creating a broad, shallow dip in the overall signal. But when the eardrum has fluid behind it, it doesn’t vibrate as well and reflects the original sound waves back. They interfere more strongly with the original chirp and create a narrow, deep dip in the signal.
Ear tube surgery
To train an algorithm that detects changes in the signal and classifies ears as having fluid or not, researchers tested 53 children between the ages of 18 months and 17 years at Seattle Children’s Hospital. About half of the children were scheduled to undergo surgery for ear tube placement, a common surgery for patients with chronic or recurrent incidents of ear fluid. The other half were scheduled to undergo a different surgery unrelated to ears, such as a tonsillectomy.
“What is really unique about this study is that we used the gold standard for diagnosing ear infections,” says co-first author Sharat Raju, a surgical resident in otolaryngology-head and neck surgery. “When we put in ear tubes, we make an incision into the eardrum and drain any fluid present. That’s the best way to tell if there is fluid behind the eardrum. So these surgeries created the ideal setting for this study.”
After parents provided informed consent, the team recorded the chirps and their resulting sound waves from the patients’ ears immediately before surgery. Many of the children responded to the chirps by smiling or laughing.
Among the children getting ear tubes, surgery revealed that 24 ears had fluid behind the eardrum, while 24 ears did not. For children scheduled for other surgeries, two ears had bulging eardrums characteristic of an ear infection, while the other 48 ears were fine. The algorithm correctly identified the likelihood of fluid 85 percent of the time, comparable to current methods that specialized doctors use to diagnose fluid in the middle ear.
Then the team tested the algorithm on 15 ears belonging to younger children between 9 and 18 months of age. It correctly classified all five ears that were positive for fluid and nine out of the 10 ears, or 90 percent, that did not have fluid.
“Even though our algorithm was trained on older kids, it still works well for this age group,” says coauthor Randall Bly, an assistant professor of otolaryngology-head and neck surgery who practices at Seattle Children’s Hospital. “This is critical because this group has a high incidence of ear infections.”
Use it at home
Because researchers want parents to use the technology at home, they trained parents how to use the system on their own children. Parents and doctors folded paper funnels, tested 25 ears, and compared the results. Both parents and doctors successfully detected the six fluid-filled ears. Parents and doctors also agreed on 18 out of the 19 ears with no fluid. In addition, parent and doctor tests generated similar-looking sound wave curves.
“The ability to know how often and for how long fluid has been present could help us make the best management decisions with patients and parents,” Bly says. “It also could help primary care providers know when to refer to a specialist.”
The team also tested the algorithm on a variety of smartphones and used different types of paper to make the funnel, with consistent results. The researchers plan on commercializing the technology through a spinout company, Edus Health, and then making the app available to the public.
“Fluid behind the eardrum is so common in children that there’s a direct need for an accessible and accurate screening tool that can be used at home or in clinical settings,” Raju says. “If parents could use a piece of hardware they already have to do a quick physical exam that can say ‘Your child most likely doesn’t have ear fluid’ or ‘Your child likely has ear fluid, you should make an appointment with your pediatrician,’ that would be huge.”
The National Science Foundation, the National Institutes of Health, and the Seattle Children’s Sie-Hatsukami Research Endowment funded the work., which appears in Science Translational Medicine.
Source: University of Washington