An electronic device for detecting respiratory depression in swallowed patients.

Newswise – Cambridge, MA – Diagnosing sleep disorders like sleep apnea usually requires a patient to spend the night in a sleep lab, connected to various sensors and monitors. Researchers at MIT, Celero Systems and West Virginia University hope to make the process less intrusive with a digestive capsule they've developed that can monitor vital signs from a patient's gastrointestinal tract.

The capsule, which is about the size of a multivitamin, uses an accelerometer to measure the patient's breathing rate and heart rate. In addition to diagnosing sleep apnea, the device could also be useful for detecting opioid overdoses in people at high risk, the researchers said.

“This is an exciting intervention to help people diagnose and then receive appropriate treatment if they have obstructive sleep apnea,” says Giovanni Traverso, an associate professor of mechanical engineering at MIT and a gastroenterologist at Brigham and Women's Hospital. “The device also has the potential to detect changes in respiratory status early, whether as a result of opiates or other conditions that can be monitored, such as asthma or chronic obstructive pulmonary disease (COPD).

In a study of 10 volunteers, researchers showed that the capsule can be used to monitor vital signs and detect episodes of sleep apnea, which occurs when a patient repeatedly stops and starts breathing during sleep. Patients did not experience any side effects from the capsule, which passed safely through the digestive tract.

Traverso is one of the study's senior authors, along with Robert Langer, MIT Institute Professor and member of the Koch Institute for Integrative Cancer Research at MIT; Victor Finomore, director of the Center for Human Performance and Applied Neuroscience Research at West Virginia University School of Medicine; and Ali Rezai, director of the Rockefeller Neuroscience Institute at West Virginia University School of Medicine. The paper was published today in the journal device.

Measurement of vital signs

Over the past decade, Traverso and Langer have developed a range of digestive sensors that can be used Monitor vital signs and diagnosing disorders of the gastrointestinal tract, such as Gastrointestinal slowing and Inflammatory bowel diseases.

This new study focused on measuring vital signs using a capsule developed by Celero Systems that includes an accelerometer that detects the slight movements produced by the heartbeat and lung expansion. The capsule also contains two small batteries and a wireless antenna that transmits data to an external device such as a laptop.

In animal model tests, researchers found that this capsule can accurately measure breathing rate and heart rate. In one experiment, they showed that the sensor could detect a decrease in breathing rate caused by a large dose of fentanyl, an opioid drug.

Based on these results, the researchers decided to further test the capsule in clinical trials West Virginia University Rockefeller Institute for Neuroscience. Ten patients enrolled in the study were monitored using a digestive capsule, and these patients were also connected to sensors commonly used for sleep monitoring, so researchers could compare measurements from both types of sensors.

The researchers found that their ingestible sensor could accurately measure breathing rate and heart rate, and also detected an episode of sleep apnea experienced by one of the patients.

“What we were able to show is that using the capsule, we could capture data that matches what traditional transdermal sensors capture,” says Traverso. “We also observed that the capsule could detect apnea, and this was confirmed by standard monitoring systems available in the sleep laboratory.”

In this study, the researchers observed the signals emitted by the capsule while it was in the stomach, but before learningThey showed that vital signs can be measured from other parts of the gastrointestinal tract as well.

“The abdomen generally gives the best signals, mainly because it's close to the heart and lungs, but we know we can feel them elsewhere,” says Traverso.

No patient reported any discomfort or harm from the capsule. X-ray imaging performed 14 days after taking the capsules showed that all of them had passed through the patients' bodies. Previous work by the research team has shown that objects of similar size typically move through the digestive tract in one day.

Close monitoring

The researchers believe this type of sensor could be used to diagnose sleep apnea in a less intrusive way than the skin-based sensors currently in use. It can also be used to monitor patients when they start apnea treatment to make sure the treatment is working.

Celero systemsThe company, founded by Travers, Langer, Jeremy Raskin, a professor of medicine at Harvard Medical School, and Benjamin Pless, now the company's CEO, is now working on sensors that can be used to detect sleep apnea or opioid overdoses.

“We know that people who have overdosed are at a higher risk of recidivism, so those people can be watched more closely so that someone can help them in the event of another overdose,” says Traverso.

In future work, the researchers hope to incorporate an overdose reversal agent, such as nalmefene, into the device to release the drug when a person's breathing rate slows or stops. They are also working on strategies to extend the time the capsules stay in the stomach.

The research was funded by the Carl Van Tassell Career Professorship, MIT's Department of Mechanical Engineering, and Celero Systems.


The paper is also co-authored by Pless, James Mahoney, Justin Kupec, Robert Stansbury, Daniel Butcher, Shannon Schuetz, and Alison Hayward.