Using technology invented by researchers from the Massachusetts Institute of Technology (MIT), doctors may one day be able to monitor a patient’s vital signs by having them swallow an ingestible sensor.

The new sensor calculates heart and breathing rates from the distinctive sound waves produced by the beating of the heart and the inhalation and exhalation of the lungs.

“Through characterisation of the acoustic wave, recorded from different parts of the gastrointestinal tract, we found that we could measure both heart rate and respiratory rate with good accuracy,” said research affiliate at MIT’s Koch Institute for Integrative Cancer Research, Giovanni Traverso.

The researchers say the sensor could make it easier to assess trauma patients, perform long-term evaluation of patients with chronic illnesses or improve training for professional and amateur athletes.

According to the researchers, inspiration for the device came from existing ingestible devices that can measure body temperature or take images of the digestive tract. Based on those concepts, the researchers set out to design a sensor that would measure heart and respiratory rate, as well as temperature, from inside the digestive tract.

To achieve this, the researchers, would have to listen to the body using a small microphone, essentially creating an extremely tiny stethoscope that can be swallowed.

“Using the same sensor, we can collect both your heart sounds and your lung sounds. That’s one of the advantages of our approach — we can use one sensor to get two pieces of information,” said MIT Lincoln Laboratory Biomaterials Scientist, Albert Swiston, Ph.D.

To interpret the acoustic data into heart and breathing rates, the researchers created a signal processing system that distinguishes between the sounds produced by the heart and lungs from each other, as well as from background noise produced by the digestive tract and other parts of the body.

The entire sensor is about the size of a multivitamin pill and consists of a tiny microphone packaged in a silicone capsule, along with electronics that process the sound and wirelessly send radio signals to an external receiver, with a range of about three meters.

After testing the pill in the gastrointestinal tract of pigs, the researchers found that the device could accurately pick up heart rate and respiratory rate, even when conditions such as the amount of food being digested were varied. The researchers expect that the device would remain in the digestive tract for only a day or two, so for longer-term monitoring; patients would swallow new capsules as needed.

In the future, the researchers plan to design sensors that could diagnose heart conditions such as abnormal heart rhythms, or breathing problems including emphysema or asthma. Currently doctors require patients to wear a harness monitor for up to a week to detect such problems, but these often fail to produce a diagnosis because patients are uncomfortable wearing them 24 hours a day.

“We hope that one day we’re able to detect certain molecules or a pathogen and then deliver an antibiotic, for example. This development provides the foundation for that kind of system down the line,” concluded Traverso.

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