Not too far in the future, doctors may be using technology invented by a team of scientists at MIT to monitor patients’ vital signs by having them swallow an electronic device that can measure heart rate and breathing rate from within the gastrointestinal tract.

Fig. 1 - This ingestible electronic device can measure heart rate and respiratory rate from inside the gastrointestinal tract. (Credit: Albert Swiston/MIT Lincoln Laboratory)
This type of sensor, they say, could make it easier to assess trauma patients, monitor soldiers in battle, perform longterm evaluation of patients with chronic illnesses, or improve training for professional and amateur athletes.

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, they explained. (See Figure 1)

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

How It Works

The researchers were inspired by existing ingestible devices that can measure body temperature, as well as others that can take internal digestive tract images. They decided to combine the two technologies and design a sensor that would measure heart and respiratory rate, as well as temperature, from inside the digestive tract.

The simplest way to achieve this, they decided, would be to listen to the body using a small microphone. The researchers essentially created “an extremely tiny stethoscope that you can swallow,” said team member Albert Swiston, a technical staff member at Lincoln Laboratory. “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,” he explained.

In order to translate the acoustic data into heart and breathing rates, the researchers had to devise signal processing systems that distinguish 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 3 meters.

In tests along the GI 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 longerterm monitoring, patients would swallow new capsules as needed.

Future Work

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 (Holter) 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.

“If you could ingest a device that would listen for those pathological sounds, rather than wearing an electrical monitor, that would improve patient compliance,” Swiston said.

The researchers also hope to create sensors that would not only diagnose a problem but also deliver a drug to treat it.

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Medical Design Briefs Magazine

This article first appeared in the January, 2016 issue of Medical Design Briefs Magazine.

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