Smartphone tympanometer identifies ear issues

Being able to hear properly is critical for the development of language and education. But in resource poor settings, like Third World countries, it can be hard to achieve an accurate diagnosis of an underlying ear disorder that may be hampering hearing and therefore damaging a person’s potential. That’s because the equipment needed is often preclusively expensive. But now scientists at the University of Washington have come up with a way to use a smart phone to study the performance of the middle ear. This is called “tympanometry” and Julia Ravey heard from Justin Chan how it works…

Justin - Ear infections affect the mobility of the ear drum because fluid that's infected or not infected, can accumulate behind the eardrum and make it stiff. And tympanometry is really one of the key tests that are used to measure middle ear function but these devices are quite expensive. They're two to five thousand uUS dollars, and this makes them inaccessible, especially in low to middle income countries. These hospitals have to rely on a very small number of tympanometry devices. So patients are coming from like nine hours drive away just for hearing screenings or other types of checkups like this.

Julia - And how does a tympanometer work?

Justin - I can present that in the context of what we have here. So what we built was a low cost tympanometry device. This is smartphone-based with parts that are only about 20 or 30 US dollars, and the parts can be purchased anywhere. So the hardware and the software for this are open source for anyone to replicate. What I'm showing here is the attachment; a syringe. So this is a medical syringe. And the idea here is that we have a motor that moves the plunger very small amounts; at sub millimetre precision. And this connects through a series of tubes that ends up in the ear. So the plunger actually ends up moving the eardrum very small and precise amounts. And at the same time, we are sending a sound via the same tubing into the eardrum and we are measuring the sound that comes back. What happens is that the recording of the sound changes as you flex the eardrum and this recording it's called a tympanogram. That's used for making clinical decisions, especially related to diagnosing ear disorders.

Julia - And so that device - you've just shown me it there - it's sort of like a box that sits on the back of your smartphone and it's all very compact and portable. There's a big long tube with almost like an earbud on the end that goes into the eardrum. And that's taking a measurement of how stiff or how flexible the eardrum is. So then do you get a readout of that on your smartphone?

Justin - Exactly. You get a real time reading on a smartphone like this. This graph here just looks like a little mountain. So the height of the mountain and the width of the mountain are key metrics that are used to determine how flexible the eardrum is. So for example, an eardrum which is too flexible will have a much higher peak one than one that's not flexible enough, with maybe a lower peak. And if you have an ear infection where your eardrum is stiff, it will actually just show up as flat; the eardrum will not move at all, even if you are adding or decreasing pressure.

Julia - And have you tested this out and compared it to the original machine that will be used in this situation to see how they compare?

Justin - Yes, we conducted clinical testing on 50 paediatric ears, and this was done in parallel with a clinical-grade tympanometry device. And we showed in our study that there was good agreement between both devices of about 86%. So this is promising and we think that for future studies, testing this out in the field will be useful to evaluate the durability of the device.

Julia - And once you get the read out from the device - say you've built it and you've done a read out - and it's saying that your eardrum doesn't respond as it should be doing so potentially you have an infection. Then what do people do with that information?

Justin - This information is typically used by a clinician in combination with other tests to guide middle ear disorder diagnosis. So this is typically just one part of a battery of tests to diagnose the function for the middle ear. This can diagnose quite a large range of disorders, so the exact follow up procedure will vary from patient to patient.