Transcript

Music

Introduction

This is a production of the National Institute of Biomedical Imaging and Bioengineering, part of the National Institutes of Health.

Host: Margot Kern

Kern: Venous ulcers affect approximately 1% of the population. These chronic wounds occur when valves in the veins of the leg malfunction, and they can take months and occasionally years to heal.

Kern: Dr. Michael Weingarten, Chief of Drexel University’s vascular surgery department and a specialist in chronic wound management, says venous ulcers are a significant economic burden.

Weingarten: To put it in perspective, it’s a chronic problem accounting for probably several billion dollars in healthcare costs in the United States, and it’s prevalent not only in elderly patients but also in working age patients. So, we’re talking about expenses in terms of treating the wounds, but also time loss from work, disabilities, things like that.

Kern: Currently, the standard treatment for venous ulcers involves controlling swelling, taking care of the wound by keeping it moist and preventing infection, and a technique called compression therapy in which patients wear special socks that squeeze the leg to prevent blood from flowing backwards. But Dr. Weingarten says these measures are lacking.

Weingarten: These are what we call passive treatment modalities. We try to change the homeostasis of the wound so it’s ideal for healing and that can be very difficult. There are very few active technologies that actively stimulate healing for these ulcers, in particular.

Kern: But that may soon change. With support from NIBIB, a research team led by Dr. Peter A. Lewin, a professor of biomedical engineering at Drexel University, has recently created a novel battery operated ultrasound patch that can accelerate healing by delivering low-frequency, low-intensity ultrasound directly to wounds.

Kern: In a recent pilot clinical trial of twenty patients, the team reported that patients who received therapeutic ultrasound treatment using their patch, in addition to standard compression therapy, had a net reduction in wound size after just four weeks.  In contrast, patients who received only compression therapy had an average increase in wound size at 4 weeks.  Surprisingly, the greatest effect was seen in a subgroup of five patients who received the ultrasound treatment for the least amount of time (just 15 minutes per week) at the lowest frequency (20khZ). All five patients in this group experienced complete healing by the fourth week.

Kern: Dr. Weingarten was impressed by the results:

Weingarten: This is a very difficult population to heal in a timely manner, and so, yes, it was rather surprising.

Kern: While using ultrasound to accelerate wound healing is not a new idea, until now, it’s been difficult to prove its clinical efficacy. One reason is that studies have used a range of ultrasound frequencies, and it turns out that lower frequencies may be better at promoting healing. So says Peter Lewin.

Lewin: We had an idea that if some of the mechanisms which were proposed by us in the literature would work, they probably would be better or more profound if we applied them at the lower frequency. Typically the therapeutic ultrasound is applied at 1-3 megahertz, we went down to between approximately 20 and a 100 kilohertz. So it’s at least a magnitude of order lower.

Kern: The team’s clinical findings were supported by experiments conducted in the lab in which cells involved in wound healing were treated with low-frequency ultrasound. The team found that 15 minutes of 20khz stimulation caused both an increase in cell proliferation and cell metabolism just 24 hours after receiving the treatment.

Kern: According to the team, one of the most challenging but also important components of the research was developing the battery operated ultrasound patch. Lewin says the device offers tremendous value to patients because it gives them the option of receiving frequent treatments without having to return to the clinic, ultimately increasing patient compliance, while saving money.

Lewin: So the whole device is approximately a 100 grams and it’s connected to the fully wearable two batteries, which are fully rechargeable, so the patient can have the device on the wound, if needed, twenty four hours a day.

Kern: The team is now working to develop an additional component of their patch which would allow physicians to view subtle tissue changes during and directly after ultrasound treatment using near infrared spectroscopy.

Kern: Lewin says the ability to monitor changes in the wound tissue during treatment would allow physicians to optimize the frequency, intensity, and rate of the ultrasound delivery for each patient. Going forward, the team plans to test their patch on a larger group of patients and to expand their studies in the lab, examining different types of cells involved in wound healing.

Kern: Josh Samuels, a Ph.D. student in Lewin’s lab says some of these mechanistic studies are already under way.

Samuels: We’re looking now a lot more at the macrophages and we’re also looking at fibroblasts. We’re trying to look at the different levels of wound healing. We know there is the inflammation phase, the proliferation phase, and the remodeling and we’re looking at the primary participants at each phase. So we know the endothelial cells are going to play a big role and the macrophages. So we’re actually examining the effects of ultrasound on each individually and then we’re going to look collectively to see if there’s cascade effects, see if one influences the other. That’s really where we’re at now with our in vitro studies.

Kern: For NIBIB, I’m Margot Kern.