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'Smart Bandage' Detects Bed Sores Before They Are Visible to Doctors

Researchers print electrodes onto thin, flexible film

Engineers at the University of California, Berkeley, are developing a new type of bandage that does more than stop the bleeding from a paper cut or scraped knee. Thanks to advances in flexible electronics, the researchers, in collaboration with colleagues at the University of California, San Francisco, have created a new “smart bandage” that uses electrical currents to detect early tissue damage from pressure ulcers (bed sores) before they can be seen by human eyes –– and while recovery is still possible.

“We set out to create a type of bandage that could detect bed sores as they are forming, before the damage reaches the surface of the skin,” said lead investigator Dr. Michel Maharbiz. “We can imagine this being carried by a nurse for spot-checking target areas on a patient, or it could be incorporated into a wound dressing to regularly monitor how it’s healing.”

The researchers exploited the electrical changes that occur when healthy cells start dying. They tested the thin, noninvasive bandage on the skin of rats and found that the device was able to detect varying degrees of tissue damage across multiple animals.

The findings, published March 17 in Nature Communications, could provide a major boost to efforts to stem a health problem that affects an estimated 2.5 million U.S. residents at an annual cost of $11 billion, the authors say.

Bed sores are injuries that can result after prolonged pressure cuts off an adequate blood supply to the skin. Areas that cover bony parts of the body, such as the heels, hips, and tailbone, are common sites for bed sores. Patients who are bedridden or otherwise lack mobility are most at risk.

Bed sores are associated with deadly septic infections, and recent research has shown that the odds of a hospital patient dying are 2.8 times higher when they have pressure ulcers. The growing prevalence of diabetes and obesity has increased the risk factors for bed sores.

“The genius of this device is that it’s looking at the electrical properties of the tissue to assess damage. We currently have no other way to do that in clinical practice,” said co-investigator Dr. Michael Harrison. “It's tackling a big problem that many people have been trying to solve in the last 50 years. As a clinician and someone who has struggled with this clinical problem, this bandage is great.”

The researchers printed an array of dozens of electrodes onto a thin, flexible film. They then discharged a small current between the electrodes to create a spatial map of the underlying tissue based on the flow of electricity at different frequencies, a technique called impedance spectroscopy.

To mimic a pressure wound, the researchers gently squeezed the bare skin of rats between two magnets. They left the magnets in place for 1 or 3 hours while the rats resumed normal activity. The resumption of blood flow after the magnets were removed caused inflammation and oxidative damage that accelerated cell death. The smart bandage was used to collect data once a day for at least 3 days to track the progress of the wounds.

The smart bandage was able to detect changes in electrical resistance consistent with increased membrane permeability, a mark of dying cells. Not surprisingly, 1 hour of pressure produced mild, reversible tissue damage, whereas 3 hours of pressure produced more serious, permanent injury.

Maharbiz said the outlook for this and other “smart bandage” research is bright.

“As technology gets more and more miniaturized, and as we learn more and more about the responses the body has to disease and injury, we’re able to build bandages that are very intelligent,” he said. “You can imagine a future where the bandage you or a physician puts on could actually report a lot of interesting information that could be used to improve patient care.”

Source:; March 17, 2015.

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