Venous skin ulcers also known as stasis ulcers or varicose ulcers are chronic wounds caused by the poor blood circulation in the venous valves or veins, usually occurring in the lower part of the legs, between the ankle and the calf. This condition is known venous insufficiency and accounts for roughly 70 % to 90% of leg ulcer cases. These ulcers are often recurring, extremely painful and can take months and years to heal. This condition affects approximately 500,000 Americans annually, and the number is expected to increase as the rate of obesity climbs. It is estimated that the financial burden for the treatment of venous skin ulcers costs US healthcare systems over one billion dollars per year and the monthly treatment costs could be as high as $2,400 a month. Current treatments for venous skin ulcers are either conservative management, such as compression therapy or invasive and expensive surgical procedures, such as skin grafts. Other available treatment options include mechanical treatment and medications. The most standard treatment however involves the infection control, wound dressings and compression therapy in which patients are asked to wear elastic stockings to help improve leg circulation. Nevertheless, all these approaches were not found to be successful in every case and these wounds take often months or sometime years to heal.
Designing Ultrasound patch:
Recently, a team of researchers led by Dr. Peter A. Lewin at Drexel University at Philadelphia have designed a novel non-invasive technique called “Ultrasound Patch” for treating chronic ulcers and wounds. This technique uses patches with a novel ultrasound applicator that can be worn effortlessly like a band-aid. In this alternative therapy, battery-powered patch sends low-frequency and low-intensity ultrasound waves directly to the wound site. The therapeutic benefits of ultrasound for wound healing were established in previous studies, but most of studies were performed with much higher frequencies, around 1-3 megahertz (MHz). Dr. Lewin believed that decreasing the frequency to 20–100 kilohertz (kHz) might work better with a reduced exposure. According to him, one of the biggest challenges in designing this technology was to build a battery-powered patch since most ultrasound transducers require a bulky apparatus which need to be fixed on the wall. Dr. Lewin and colleagues also wanted to create something which is portable and can be easily worn for which the device has to be essentially battery operated. To accomplish this, they designed a transducer that could produce medically pertinent energy levels using minimum voltage. The ultrasound patch in its present form, weighs approximately 100 grams and required two rechargeable AA batteries. It is designed to be worn over the ulcer or the wound and the patient can deliver controlled pulses of ultrasound directly to the wound, while at home. The funding for this study was received from the National Institute of Biomedical Imaging and Bioengineering (NIBIB), a part of the National Institutes of Health.
Clinical studies for testing Ultrasound patch
To determine the optimal frequency and treatment duration of ultrasound patch, the study trial was carried out initially in total 20 patients, divided into four groups. Each group received either 20 kHz for 15 minutes, 20 kHz for 45 minutes 100 kHz for 15 minutes, or 15 minutes of a placebo or control which received no radiation. According to the researchers, the first group was the one that eventually came out best, where all the five participants completely healed by the time they reached their fourth session. In contrast, the ulcers of the patients in the placebo group worsened over the similar duration. Results suggested that patients who received this low-frequency, low-intensity ultrasound therapy during their weekly follow ups (in addition to the standard compression therapy), showed a net reduction in wound size just after four weeks of the therapy. Whereas, the patients who did not received the ultrasound treatment had an average increase in the wound size. The team’s clinical findings were further confirmed by their in vitro studies where after 24 hours of receiving 20 kHz ultrasound for 15 minutes, mouse fibroblasts cells that play an active role in wound healing showed a 32% increase in cell metabolism and a 40% increase in cell proliferation as compared to the control cells. These findings are yet to be published in the Journal of the Acoustical Society of America.
Advantages and applications of Ultrasound patch
Researchers believe that using ultrasound patch for chronic ulcers will reduce the treatment cost and patient’s discomfort. It aids in speedy recovery of wounds as compared to the conventional approaches and could eventually be used to manage wounds associated with diabetic and pressure ulcers. However, before it widespread applications, studies need to be conducted on the larger-scale for establishing its overall safety and efficacy. The ultrasound patch is light weight and can be easily worn like a band-aid. Another characteristic feature of this patch is an attached monitoring component that uses near infrared spectroscopy (NIRS) to assess the progress of wound healing. NIRS can help to non-invasively assess changes in the wound bed and monitor if the treatment is working in its initial stages, when healing is difficult to spot with the naked eye. Using this patch will also prevent frequent visits to doctor’s clinic or hospital, which can be at times very difficult for patients with chronic wounds. Currently, studies with larger numbers of patients are underway to confirm the safety and efficacy of this patch before it makes its way into the clinics.
