'Smart Bandage' Detects Bed Sores Invisible To The Naked Eye

'Smart Bandage' Detects Bed Sores Before They Are Visible To Doctors
The smart bandage is fabricated by printing gold electrodes
onto a thin piece of plastic. This flexible sensor uses
impedance spectroscopy to detect bedsores that are invisible
to the naked eye. (Credit: UC Berkeley)
Engineers are developing a new type of bandage that does far more than stanch the bleeding from a paper cut or scraped knee. Thanks to advances in flexible electronics, the researchers have created a new "smart bandage" that uses electrical currents to detect early tissue damage from pressure ulcers, or bedsores, before they can be seen by human eyes - and while recovery is still possible.
 
The researchers exploited the electrical changes that occur when a healthy cell starts dying. They tested the thin, non-invasive bandage on the skin of rats and found that the device was able to detect varying degrees of tissue damage consistently across multiple animals.

Tackling a growing health problem
The findings, published in the journal 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.

Pressure ulcers, or bedsores, are injuries that can result after prolonged pressure cuts off 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 bedsores. Patients who are bedridden or otherwise lack mobility are most at risk.

By the time you see signs of a bedsore on the surface of the skin, it's usually too late. This bandage could provide an easy early-warning system that would allow intervention before the injury is permanent. 

Bedsores are associated with deadly septic infections, and recent research has shown that 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 bedsores.

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

The researchers pointed out that a cell's membrane is relatively impermeable when functioning properly, thus acting like an insulator to the cell's conductive contents and drawing the comparison to a capacitor. As a cell starts to die, the integrity of the cell wall starts to break down, allowing electrical signals to leak through, much like a resistor.

To mimic a pressure wound, the researchers gently squeezed the bare skin of rats between two magnets. They left the magnets in place for one or three 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 three 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 a dying cell. Not surprisingly, one hour of pressure produced mild, reversible tissue damage while three hours of pressure produced more serious, permanent injury.

"We set out to create a type of bandage that could detect bedsores as they are forming, before the damage reaches the surface of the skin. 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 said.


Based on material originally posted by University of California - Berkeley.