Nobody knows precisely why it works, but doctors have known for decades that the healing process for open wounds can be greatly speeded up by applying negative pressure — that is, suction — under a bandage sealed tightly over the affected area. The speculation is that it helps by drawing bacteria and fluid away from the wound, keeping it cleaner.For patients, there is a benefit even beyond the speedier healing. Traditional dressings need to be removed and replaced — sometimes painfully — up to three times a day, but with the negative pressure system dressings can be left in place for a few days. But in the developing world, there's a problem: The systems are expensive, and they need to be plugged in or powered by batteries that last only a few hours. In many developing nations, a reliable source of electricity is rarely available.That's the problem that students in an MIT mechanical engineering class decided to tackle a few years ago. With the help of Dr. Robert Sheridan from Massachusetts General Hospital, the students developed a simple, inexpensive and lightweight version of the system that required no power supply and could be left in place for days. One of those students, Danielle Zurovcik SM '07, continued to work on the project and made it the subject of her master's thesis. She has continued to work on it on the side as she pursues her doctorate.The project was part of a mechanical design class taught by mechanical engineering professor Alexander Slocum in collaboration with local hospitals through a Boston-based organization called the Center for Integration of Medicine and Innovative Technology.Earlier this semester, Zurovcik, who had been making plans for field tests of the patent-pending device at a rural clinic in Rwanda this fall, was asked by the nonprofit healthcare organization Partners in Health to take part in earthquake relief efforts in Haiti. She traveled there with a supply of 50 of the current version of the plastic, molded pumps, which cost about $3 each. (The only portable versions on the market today cost $100 a day just to rent, and must have their batteries recharged after about six hours.)The device, a cylinder with accordion-like folds, is squeezed to create the suction, and then left in place, connected to the underside of the wound dressing by a thin plastic tube. At that point, it requires no further attention: "It holds its pressure for as long as there's not an air leak," Zurovcik explains. For that reason, a suitable dressing that can hold the seal is a crucial element of the system.The Haitian patients who were treated with the device were pleased with how it worked. While the team didn't have time to conduct long-term evaluations, Zurovcik says, "In the short term, we systematically evaluated the wounds, and were able to verify that negative-pressure therapy was being applied and the healing process was underway."The trip to Haiti was led by Dr. Robert Riviello of the Division of Trauma, Burn and Surgical Critical Care at Brigham and Women's Hospital in Boston. Riviello estimates that between 50 million and 60 million people in low-income countries suffer from acute and chronic wounds, and a large number of them would benefit from negative-pressure wound therapy. He says the device "has the potential to be a great benefit to patients around the world" once a few technical hurdles are cleared."Our biggest challenge at the moment is ensuring a reliably intact seal on human skin [that can be] easily applied," Riviello says. "If we can resolve this, then I think there is enormous potential."Zurovcik notes that an improved version of the device — one that maintains a more constant pressure and is smaller and so easier to conceal when being worn for days — has been developed and is being manufactured now.Zurovcik and her team designed the devices to be made in a sustainable way. They can be manufactured locally in many developing nations, using equipment that already exists there, she says. She is already in discussions with a plastic molding company in Rwanda, she says.She plans to go to Rwanda in the fall to test the new version of the device, which is small enough to carry in a pocket. "Their clinics are filled with wounds," she says, noting that the injuries are often severe because patients avoid going to clinics as long as they can. The clinics themselves "don't have power, don't have a lot of supplies. I'd like to be able to bring something simple, that patients would be able to care for on their own."