MIT researchers have developed ingestible sensors that could be swallowed by patients to enable doctors to monitor their heart and breathing rate from inside the digestive tract.
Described in the latest issue of the journal PLOS One, the sensors actually detect sound waves produced by the patient's beating heart and inhalations and exhalations to deduce the data that interest the doctors.
“Through characterisation 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 one of the authors of the paper.
Existing methods for measuring heart and respiratory rate, such as electrocardiograms and pulse oximetry, require contact with the patient’s skin. For long-term monitoring, wearable devices can be used but these may not always be comfortable.
The researchers believe their technology could make it easier to assess the condition of trauma patients, monitor soldiers in the battle field, observe patients with chronic illnesses or even to provide data for training of professional athletes.
The capsules, inspired by existing devices used for measuring body temperature or taking images of the digestive tract, are fitted with small microphones that function like internal stethoscopes. About the size of a multivitamin pill, the capsule connects wirelessly to an external receiver up to a distance of three metres.
“Using the same sensor, we can collect both your heart sounds and your lung sounds,” said researcher Albert Swiston. “That’s one of the advantages of our approach - we can use one sensor to get two pieces of information.”
A sophisticated processing system can distinguish the signals for the two rates and filter out background noise produced by the digestive tract.
In tests with pigs, the researchers were reliably able to read heart and respiratory rates of the animals without regard to the fullness of their stomachs.
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.
The military may welcome such technology to monitor soldiers for fatigue, dehydration, tachycardia or shock. When combined with a temperature sensor, it could also detect hypothermia, hyperthermia or fever from infections.
In future, the researchers plan to design sensors that could diagnose heart conditions such as abnormal heart rhythms or breathing problems including emphysema or asthma.
The researchers also hope to create sensors that would not only diagnose a problem but also deliver a drug to treat it.