A battery-powered skin patch can help heal chronic wounds by zapping them with ultrasound, research has shown.
In tests, the 100 gram device - little bigger than a sticking plaster - dramatically reduced the size of chronic leg ulcers after four weeks.
Patients who were not given the treatment saw an average increase in wound size over the same period.
The patch delivers pulses of low-frequency ultrasound to the wound for 15 minutes.
Scientists are not sure how it works, but are looking at the effects of ultrasound on macrophages - immune cells that play a critical role in healing - and collagen production.
Laboratory studies showed that skin cells from mice experienced a 32% increase in metabolism and 40% increase in multiplication rate after being exposed to low-frequency ultrasound.
Venous ulcers occur when malfunctioning vein valves cause blood to pool in the legs.
Standard treatment involves controlling swelling, fighting infection, and compression of the leg to prevent a back-flow of blood.
Wounds often take months and occasionally years to heal.
“Right now, we rely mostly on passive treatments,” said lead researcher Dr Michael Weingarten, from Drexel University in Philadelphia, US. “With the exception of expensive skin grafting surgeries, there are very few technologies that actively stimulate healing of these ulcers.”
The research showed that low-frequency 20 kilohertz ultrasound was more effective than ultrasound at higher frequencies.
Five patients experienced significant healing after four weekly 15-minute treatments, the scientists reported in the Journal of the Acoustical Society of America. Their gaping red wounds had almost closed.
Surprisingly, a longer 45 minute treatment did not produce such good results.
“Sometimes we learn that more is not always better,” said co-author Joshua Samuels, from Drexel University. “There may be a dosing effect.”
An add-on diagnostic device that can help optimise ultrasound treatment for each patient is also being tested.
<http://acousticalsociety.org/> (Journal of the Acoustical Society of America)