While blood pressure cuffs are considered the most accurate method of measurement, they require the user to sit down, put on the cuff, and stay still. This can be inconvenient and may lead to errors in measurement if the cuff is not worn properly or if the user does not follow the correct protocol. Researchers are now exploring the use of earbuds as an alternative to blood pressure cuffs for regular blood pressure monitoring at home. The earbuds can simplify this process, eliminate expenses for purchasing a blood pressure cuff, and support regular monitoring of blood pressure for individuals managing heart failure.

Earbuds often feature noise-cancellation technology that employs both an outer and an in-ear microphone. The outer microphone captures ambient noise while the in-ear microphone records sounds within the ear canal. Interestingly, these in-ear microphones can detect internal bodily sounds, including heart sounds. Recent studies have demonstrated that the audio signals obtained from within the body can be used to measure heart rate, similar to a stethoscope. Researchers at the University of Toronto (Toronto, ON, Canada) are now exploring various signal processing techniques to analyze these heart sounds and determine blood pressure levels, with the goal of facilitating regular blood pressure monitoring and supporting self-care for heart failure patients.

To use earbuds for blood pressure monitoring, patients can simply wear them, and the in-ear microphone will record audio and transmit it to their smartphone via Bluetooth. The phone will then analyze the heart sounds and determine blood pressure, which can be shared with the patients or their care team. This technology can be used with any earbud that has an in-ear microphone, provided that the patient is in a quiet environment since heart sounds can be very subtle and easily missed in noisy surroundings. Therefore, the most practical application of this technology would be during telehealth consultations when patients are seated in a quiet indoor environment. Additionally, patients who already own noise-canceling earbuds can use this technology without any additional equipment.

Earbuds have an advantage over smartwatches when it comes to estimating blood pressure. While smartwatches rely on blood flow at a single site, earbuds can offer twice the amount of information by measuring blood flow in both the left and right ear. In addition, some researchers have found that blood pressure can also be estimated by measuring how long it takes for a heart pulse to travel from one location in the body to another. While smartwatches can also estimate blood pressure this way, the short distance between points doesn't allow for much error. Earbuds, on the other hand, offer a much larger distance between points, which can actually make them more accurate than smartwatches.

“We’re very interested in monitoring blood pressure through any ubiquitous sensing mechanism,” says Alex Mariakakis, an assistant professor in the University of Toronto’s department of computer science in the Faculty of Arts & Science, who has been awarded a seed grant by TRANSFORM HF – a U of T institutional strategic initiative that develops point-of-care diagnostics, wearables, and AI technologies to monitor and proactively treat people with heart failure – for his project ‘Accessible Blood Pressure Estimation with Earbuds.’” “One study we’re hoping to do alongside this project, or maybe a little later, would be to compare and contrast all the different technologies being considered for blood pressure monitoring – earbuds, smartwatches, smartphones – to see what works best. Can we get better performance with earbuds versus a smartwatch? Can we combine a smartwatch and earbuds to get an even more accurate measurement? Eventually, we want to deploy this in clinic.” 

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