Strain sensor offers wearable solution for monitoring lung disease

Strain sensor devices developed could provide people with a wearable, disposable respiration monitoring solution that helps them manage chronic pulmonary conditions.

Strain sensor devices
Paired sensors track the rate and volume of the wearer’s respiration by measuring the local strain on the application areas (Pic: Josh Kim/UCI)

Developed by researchers at the University of California, Irvine, the new device has been designed to provide high-fidelity readings on a continuous basis to children with asthma and cystic fibrosis, or others with chronic respiratory disease.

The inexpensively produced sensors were created by UCI biomedical engineers using thin sheets of plastic that are painted or drawn on and then shrunk with heat.

Placed in two positions – one between the ninth and 10th ribs and another on the abdomen – the sticking plaster-like devices track the rate and volume of the wearer’s respiration by measuring the local strain on the application areas. According to UCI, the information gleaned could, in the case of asthma, help warn of an oncoming attack.

“The current standard of care in respiration monitoring is a pulmonary function test that’s often difficult to perform and limited in terms of the snapshot it provides of a patient’s respiratory health – meaning problems can sometimes be missed,” said Michael Chu, UCI graduate student researcher in biomedical engineering and lead author of a paper on the innovation published in npj Digital Medicine. “Our new stretch sensors allow users to walk around and go about their lives while vital information on the health of their lungs is being collected.”

The strain sensor devices are made by applying a very thin layer of metal to a sheet of plastic and then heat-shrinking it to cause corrugation. The film is then transferred to a soft, stretchy material – similar to small bandage – that can be adhered to a patient. Signals from embedded sensors can be transmitted via Bluetooth to be displayed on a smartphone app.

The strain sensor devices were developed in the lab of Michelle Khine, UCI professor of biomedical engineering whose newborn son was confined to a neonatal intensive care unit that was connected to an array of machines that supplied oxygen and monitored his breathing.

“Despite having his whole tiny body covered in sensors, all the hospital staff could get was respiration rate information. If you looked at the vitals monitor, you’d see this waveform, so it looked like they were getting [respiration volume] information, but they weren’t,” Khine said. “I felt so helpless with my child just lying in this box. I wasn’t allowed to carry him for eight days, so it was heartbreaking – but also frustrating to see all of these wires hooked up to him but not giving all the information we wanted.”

She said those days in the hospital following the birth of her son were strongly motivating to her as a biomedical engineer: “I sent some pictures of him all wired up to my students, and I said: ‘We have to be able to do better than this.”

So far, members of the Khine lab have tested the new technology on healthy subjects, but there are plans for a pilot trial with a small number of asthma sufferers in the coming months.