On a chilly October evening a decade ago, physician Michael Cohen arrived at Boston’s Logan International Airport lugging a hefty contraption, built like a tiny tank, that immediately drew the attention of airport security officers. It was a device to detect ear problems, and he and a colleague were hauling it around the globe — first on a redeye to Frankfurt, followed by Khartoum, and then on to Addis Ababa.
The device — called a tympanometer — was too pricey for many health care providers worldwide to afford on their own, so Cohen, an otolaryngologist at Massachusetts Eye and Ear, was shuttling it to colleagues in Ethiopia.
Now, a group of engineers and hearing specialists are working to tackle that gap head-on. They are designing tympanometers that are cheap enough and small enough to find their way into the hands of nearly any provider who needs one. In a preliminary new study, published last month in Communications Medicine, the researchers report that their smartphone-based device performed nearly as well as commercially available tympanometers that can cost thousands of dollars.
“This is the sort of product that’s ideal for a resource-constrained setting where this information would just otherwise be unavailable,” said Cohen.
The tympanometer is one of the many devices in the armamentarium of ear, nose, and throat doctors and audiologists, who focus on hearing and collaborate closely with otolaryngologists. A tympanometer vibrates the eardrum and then measures the sound it reflects, testing how well the ear moves. That detected sound shows physicians whether the eardrum is functioning appropriately. Fluid in the ear, a punctured eardrum, and abnormal bone growth all show up on the graphs generated by tympanometers.
The first in particular, which is often a sign of infection, is a big problem that can cause hearing loss and diminished hearing. Middle ear infections are among the most common reasons that a family will visit a primary care provider and it is estimated that over half of all toddlers will develop such an infection every year. Especially in childhood, any type of hearing loss is an even bigger problem, as toddlers rely on their sense of sound to understand language and continue normal development.
“Tympanometry is something that is used all the time in otolaryngology and audiology visits. It’s part of routine care,” said Randall Bly, an otolaryngologist at Seattle Children’s Hospital and the University of Washington and a senior author on the new study. “And it’s prohibitively expensive in many instances.”
Tympanometers are expensive, typically running between $2,000 to $5,000. There are already portable tympanometers on the market that are smaller than the traditional model Cohen was using, but they, too, can cost thousands of dollars. In designing the new model, the researchers specifically wanted to dramatically cut down the costs of using the technology in routine care while retaining accuracy. In a study with 50 children, the smartphone-based tool gave results similar to those delivered by commercial devices in 86% of cases.
And importantly, the researchers published the code online and purposefully did not patent the technology, which allows others to build on and use the work freely.
“This exploits the economies of scale that smartphones have (which comes with processors, displays and all kinds of hardware sensors) that does not exist with these diagnostic medical devices,” said Shyam Gollakata, a professor at the University of Washington and senior author of the paper, in an email. “I think this is an important direction we need to explore for multiple medical conditions so as to democratize medical devices and make them accessible to all parts of the world.”
The new device uses a cheap speaker, microphone, motor, and pressure sensor to replicate the mechanism of existing tympanometers, which insert a Q-tip-like probe into the ear, play a sound, and record the sound reflecting from the eardrum. (This also involves measurements at different pressures in the ear canal, made possible by a syringe and the pressure sensor.) Overall, the design is compact. By comparison, the tympanometer that Cohen took to Ethiopia weighed the equivalent of 6 gallons of water.
To build it, the researchers scoured patents and took apart tympanometers they bought on eBay. The most challenging step was creating an airtight seal, said the study authors, which involved testing many different materials and adhesives to get it right. “I thought it was pretty cool because they have to be able to change air pressure in the ear,” said Beth Prieve, an audiologist and professor at Syracuse University who studies the middle ear and was not involved in the study.
The pandemic disrupted the timeline of the study, as it temporarily paused patient recruitment. It also narrowed the pool of potential participants, because fewer kids were coming in to have their ear infections treated.
Beyond portability, one of the main strengths of the new device is its price — a mere $28 on top of the smartphone. High cost of other tympanometers is a concern shared by other physicians. Brian Westerberg, who travels to Uganda nearly every year for medical work, compared the price for tympanometers to the high cost of certain hearing aids. “The anecdotal word on the street is that all the hardware in that, you could buy for a few hundred dollars. And it’s all research and development, and the name, and the software really that you are paying for,” said Westerberg, a neurotologist at Providence Health Care in Canada. With tympanometers, he said, “I’m not sure research and development costs you can put in there because all of that technology has been around for decades.”
“There has not been much recent innovation in tympanometer devices in the last decade or so,” Gollakata said. “The medical device industry has had no competition.”
The devices are largely ill-suited to the dust and dirt outside of in-hospital clinics. “They tend to be delicate, getting knocked around, and they have to be calibrated too on a regular basis,” said Westerberg. Larger devices are also hard to bring to schools or transport in a mobile clinic. That is why Westerberg sees the open source insights from the new research as so valuable. “It seems very altruistic,” said Westerberg. “They just seem to be in it to improve access to care, which is a refreshing, refreshing perspective.”
The researchers hope that their device will be used and improved upon in lower-resource areas. It is an appealing prospect for physicians who practice in those regions.
“The results that they have and the accessibility they would give to very low resource countries, it would really help to avoid all the problems of not having a diagnosis of hearing loss or problems that give hearing loss,” said Amarilis Meléndez, head of the Department of Otorhinolaryngology at Hospital Santo Tomás in Panama.
It could also be useful in other areas where health care is difficult to access. “Whether you’re in the United States or Canada, there are still pockets of people who do not have good access to care,” said Westerberg. “And this technology, this mobile technology, really is allowing people to take it closer to home.”
Westerberg has personally experienced this. “I just got an email the other day from a family doc who’s up in Haida Gwaii,” an archipelago off of Canada’s west coast “way out by the Alaska border,” he said. By examining pictures the local doctor sent, he was able to save the patient a “three-hour flight down and all the costs to the health care system associated with that.” That is not always possible, however, because even for experts, visual examination is not fool-proof. “I look at ears all day long and there’s some areas that I just struggle to tell: Is there fluid there or not?” said Westerberg. He needs a tympanometer in these instances to decide between different but critical treatment options.
But additional work lies ahead, including to make the devices useful for infants, who have softer ear canals. The conventional frequency that works for older children and adults does not work for them. A higher frequency, which was not tested in the study, would perform better instead. “I would like to see [this] done in another study,” said Meaghan Reed, Director of Clinical Audiology at Massachusetts Eye and Ear.
Physicians and the study authors alike also point out the need for more research, including experiments involving care providers who are not specially trained and practice in different parts of the world. “I would be very willing to test this product,” said Titus Ibekwe, head of the Department of Otorhinolaryngology at the University of Abuja in Nigeria. He said the first study is “enough to draw an anecdotal conclusion, but not a conclusive one.” Gollakata said there are also plans to test the device in Kenya.
Experts said that for the technology to be used more broadly, there is also a need to ensure that there are providers trained to use it and the specialists to treat the problems that get diagnosed. “In some places, you don’t have enough resources of ENTs to see the patients,” said Meléndez, using an acronym that refers to otolaryngologists. A 2019 study that she co-authored found a significant disparity in the number of otolaryngologists within Latin America, with as few as 50 of these specialists in Guatemala, a country with 17.7 million people. The low number of otolaryngologists is a problem in her home country of Panama too, Meléndez said.
Experts added that use of the new, smartphone-based tympanometers isn’t enough to close gaps in access. Devices such as audiometers and electroencephalograms are necessary for pinpointing other hearing-related problems and conducting universal hearing screenings for newborns, which the World Health Organization recommends. “But the equipment is not there, so that becomes the limitation,” said Ibekwe. Audiometers, which are used for hearing tests, are even more expensive, costing as much as $12,000, Westerberg said. “That’s just a nonstarter for somewhere like Uganda,” he said.
The researchers already see their work making an impact, though. “Previously if you wanted to do this, it’d be a lot of red tape and bureaucracy to try to buy a tympanometer and order a tympanometer,” said Justin Chan, a Ph.D. student at the University of Washington and first author of the study. “But now we have something that somebody can just download off the internet and potentially build and assemble. And that’s a capability that has not been done before.”