“Sensor tablet” could make sleep apnea diagnosis easier

The technical units for monitoring vital functions are housed in this small capsule. © Ben Pless

No need to spend the night in a sleep lab: Researchers have developed a swallowable capsule that can record pauses in breathing and a person's heart rate from the digestive tract. As successful tests of the system on ten volunteers show, this procedure could make it easier to diagnose and treat patients with sleep apnea. It could also be used to monitor drug overdoses that affect breathing.

Exhausted and not rested despite sleeping for a long time: These symptoms can be caused by so-called obstructive sleep apnea. Those affected unknowingly suffer from pauses in breathing at night, which significantly impair their quality of sleep. It is a relatively common problem that can severely disrupt your well-being and increase the risk of other illnesses. However, diagnosing sleep apnea has so far been relatively complicated: sleep and breathing are recorded by sensors placed on the skin and connected to monitoring devices. For a detailed examination, those affected must go to a sleep laboratory. After a diagnosis, this is often necessary to investigate treatment success.

The researchers led by Giovanni Traverso from the Massachusetts Institute of Technology in Cambridge have now developed a concept that could make the diagnosis and monitoring of nocturnal breathing and cardiac activity more convenient. It is based on technology that is currently being developed for other medical applications. These are swallowable capsules that can be equipped with various electronic functional units. After they have been used for examinations or treatments in the gastrointestinal tract, they are excreted again.

Accelerometers record vital signs

The researchers have now adapted this concept to their intended application: They have developed a capsule that is about the size of a multivitamin tablet and can monitor a user's vital functions from the digestive tract. The device has a battery to power two technical units: It is equipped with a highly sensitive accelerometer that can record the subtle movements that are transmitted to the gastrointestinal tract through breathing and heartbeat. The capsule also houses a small transmitter that transmits the data to external devices such as a smartphone or laptop. They can then be transferred into a representation of the course of breathing and cardiac function.

The scientists first tested their sensor capsule on pigs. It was shown that the small device was able to accurately measure the animals' breathing and heart rates and was easily excreted after use. In an experiment, they were also able to show that the sensor capsule detected the reduction in breathing rate that was caused by the drug fentanyl in the animals. It is an opioid active ingredient that is used, among other things, in emergency medicine to treat severe pain. However, there is a risk of overdose, which can lead to dangerous breathing problems.

Promising test results

After the successful animal experiments, the researchers were able to move on to a clinical test: ten people agreed to take the capsule and be examined. In order to be able to compare the results, they were also monitored using the standard system for recording vital functions in a sleep laboratory. As the researchers report, the results confirmed the results of the animal experiments: the ingestible sensor precisely recorded the subjects' breathing and heart rate. The operation went smoothly and the devices were removed without any problems. There was a particular success: Using the data, the team actually identified a sleep apnea episode in one of the study participants. “We were able to show that we use the capsule to collect data that corresponds to that of conventional skin sensors. “We were also able to confirm that the capsule can detect apnea – and this was confirmed by the standard monitoring systems available in the sleep laboratory,” concludes Traverso.

According to him, there is now considerable potential for the concept: “It could help make diagnoses easier and then initiate appropriate treatment in the case of obstructive sleep apnea,” says Traverso. It could then also be used to conveniently monitor the effectiveness of the therapy. There are also other important applications, such as monitoring opioid overdoses, the team emphasizes. “The device has the potential to detect changes in breathing early, regardless of whether they are due to opiates or illness,” says Traverso.

He and his colleagues now want to devote themselves to further developing the system. It may be possible to incorporate a feature that could automatically release an opioid overdose reversal agent when a patient's breathing rate slows or stops.

Source: Massachusetts Institute of Technology, Cell Press. Specialist article: Device, doi: 10.1016/j.device.2023.100125

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