The Power of Negative Pressure
By Sony Salzman
BU News Service
For Danielle Zurovcik, inspiration struck when she caught sight of a toilet plunger while wandering through Kmart. The mechanical engineer immediately saw this rudimentary structure not as a toilet plunger, but as the basic building block of a mobile medical device. In the plunger she saw a potential solution to an engineering problem that had been on her mind for some time. Her vision was to help doctors treat chronic wounds with a healing method called negative pressure wound therapy, but at a fraction of the cost of the devices currently used in U.S. hospitals.
Zurovcik spent much of her time at MIT, first as a masters, then a doctoral student, determined to solve the problem of negative pressure wound therapy. Slow-healing wounds like topical ulcers and surgical incisions keep low-risk patients tied to their hospital beds, hooked up to this negative pressure device. Victims of traumatic wounds from explosions and car accidents can also benefit from negative pressure wound therapy, but the current standard-of-care device used to speed up healing is expensive and cumbersome. Her device – inspired by the toilet plunger – produces almost the same amount of healing power, but costs less than $5 and gives wound patients more mobility.
Negative pressure wound therapy was originally pioneered in 1995 by medical device company Kinetic Concepts, Inc. (KCI). The device applies an external suction to a wound site, prompting cells on the surface of the skin to divide quickly, encouraging blood flow and reducing the risk of infection. The device works like a vacuum storage bag used to stow away winter clothes in the summer. Expect instead of compressing sweaters and coats, the vacuum acts on an ulcer, scar or amputation site on a patient’s skin. And unlike the storage bag, the skin’s surface has many nooks and crannies, making a perfect seal very difficult to achieve. A perfect seal theoretically allows a vacuum to exist forever (the reason sweaters stay compressed all summer). However, it’s tough to create a perfect seal on a wound site; instead, KCI’s device relies on pulling a lot of air across the wound site to create that vacuum.
Negative wound therapy has become increasingly common over the last 15 years, with many success stories from soldier’s injuries incurred in Middle East conflicts. KCI owns a majority of the market for negative pressure wound therapy, but its device relies on a continuous power source, putting it out of reach for American patients who want to heal at home, or for hospitals in developing nations with no reliable power.
For years, doctors at Brigham and Women’s Hospital have been trying to find a negative pressure wound therapy without the leash of an electric cord. After Zurovcik’s Kmart epiphany, she discovered that once compressed, the plastic toilet plunger applies almost the same amount of pressure as the KCI electrical device. She built a prototype that included her modified toilet pump, a small hose and the dressing to seal the wound. Her device is small – so small that she carries it around in her tote.
Similar to the KCI device, the process of negative pressure wound therapy begins by dressing the wound, putting one end of a small hose near the wound and covering the entire wound with a plastic bandage. The difference between KCI’s device and Zurovcik’s is that instead of an electrical vacuum at the other end of the hose, her device uses the small, compressed plunger to create pressure inside the bandage at the surface of the skin. This design is portable, does not use use batteries or electricity, and it’s cheap. Collaborating with Brigham physicians working in Rwanda, Zurovcik specifically designed her device so that it could be used in worst-case, resource-poor scenarios. She was wrapping up the first prototype just as the devastating 7.0 earthquake hit Haiti in January of 2010.
“Hospitals in Haiti had $3 million in KCI devices, no electricity and 400 patients that needed negative pressure wound therapy,” she said. Moving quickly, she and her advisor formed a small humanitarian team. However, before they left for Haiti, she needed to be able to produce her gizmo on a massive scale. She started emailing and calling the CEOs of the toilet plunger and plastic tubing manufacturing companies. Within two weeks, she convinced these companies to donate all the component parts of to build 400 new vacuum pumps. When the pallets of materials arrived at the MIT loading dock, however, Zurovcik quickly realized she underestimated just how enormous an order of 400 pumps and hoses would be.
“I had no place to store them, so I shoved them into vacant classrooms at MIT and left my email in case people needed to use the rooms,” she said. The snafu didn’t cost them any time, and the team soon flew to Haiti with all the mechanical parts and assembled the devices on the ground. By the time they landed in Port-au-Prince, many wounds from emergency surgeries had been neglected, becoming infected and healing very slowly.
Zurovcik’s team treated more than 200 patients with basic first aid as part of the overall relief effort, and she was able to test her pressure device on six patients with positive results. As part of the humanitarian mission, she was not allowed to explicitly perform clinical trials on patients, but the few instances she was able to use her device as part of the overall relief effort encouraged her to continue developing her prototype. On more than one occasion in Haiti, she applied her wound care device to a tricky area of her own skin, like an elbow or knee, before going to sleep in her tent to help her understand how the patient’s natural movement might disrupt it.
“She’s definitely got that visionary engineer and mad scientist complex,” said Dr. Robert Riviello, a Brigham surgeon who was part of the Haiti relief team and consulted with Zurovcik during prototype development. “She’s been the prime human subject in all our wound pumps.”
Now, back in Boston with her PhD in hand, Zurovcik is working full time on her start-up company called WiCare. In May, she landed a $100,000 award from the Consortium of Affordable Medical Technologies to get her company off the ground. If her device is approved by the FDA it will be a vastly cheaper option than the current negative pressure wound devices on the market. Although replacing the standard-of-care is a daunting prospect, Zurovcik and other physicians believe patients across the globe could benefit from an inexpensive, mechanical wound treatment.
“Sure, we’ve helped patients and saved limbs, but I want to expand to a larger scale now. Every day I’m not working, I feel guilty.” she said.