January 30, 2008
Artificial Lungs Coming Soon
When the lungs fail, doctors have woefully few tools in their arsenal to help people breathe.
That may change soon, say scientists who believe they are within sprinting distance of offering patients with acute lung failure an artificial lung -- at least one that can be used short-term while they await transplants or for their damaged lungs to heal.Researchers from academic institutions across the country who are developing and testing prototypes believe artificial lung clinical trials in humans, similar to studies already underway in Canada and Europe, may begin as early as this spring.
"We are doing extensive work with the Department of Defense," says Brack Hattler, director of the Artificial Lung Program at the University of Pittsburgh. "They are very interested in support of soldiers in combat." He expects human trials this spring for his group's external device, the Hemolung.
Other artificial-lung researchers expect their models to be ready for human testing within one to five years. Food and Drug Administration approval for such devices could take years longer.
For suffering patients, five years may seem eons away, but in the research world it's just around the bend, says Keith Cook, research assistant professor in the department of surgery and biomedical engineering at the University of Michigan.
Cook and colleague Robert Bartlett, a pioneer in the development of artificial organs, won a $5 million grant from the National Institutes of Health to fund animal studies that will accelerate the use of their Total Artificial Lung prototype in humans.
According to the National Heart, Lung, and Blood Institute, 150,000 Americans experience lung failure each year. A third do not survive, and those who do often suffer permanent respiratory damage. One thousand wait in line for lung transplants; 25% will die because their lungs fail them while they wait.
The purpose of an artificial lung is to help lung-failure patients survive the tenuous bridge of time between loss of respiratory function and a lung transplant, and to allow a patient whose lungs have undergone trauma, like severe smoke inhalation, to rest and heal, Cook says. "That time frame may be a few days or a few weeks."
'Iron lung' memories persist
Early artificial-breathing devices include the tank respirator, or "iron lung," introduced in the late 1920s and known for its role in treating polio victims.
Current treatment for lung failure is to hook patients up to an artificial respirator. It is costly, immobile and requires intubation, a process that can cause infection, says John Conte, a heart-and-lung transplant surgeon and associate professor at Johns Hopkins University School of Medicine. "You don't want to take a patient who's been flat on his back, with poor muscles and infection at the IV site, and do a transplant. That's a recipe for disaster."
Artificial lungs are small and portable, however, and are designed to allow patients to remain mobile and therefore stronger for surgery.
In healthy lungs, blood vessels absorb oxygen from the blood that's pumped in from the heart, then release carbon dioxide through exhalation. An artificial lung basically imitates the way a normal lung works.
Scott Merz, a biomedical engineer and founder of MC3, a medical device company in Ann Arbor, Mich., says his company has a prototype of an artificial lung, Biolung, that may begin human testing in another year or two. MC3's soda-can-sized device contains a bundle of polymer fibers that help exchange oxygen in the blood for carbon dioxide as blood washes over them.
Like other artificial-lung models, the Biolung is not implanted. It's worn outside the body, attached with tubes to large blood vessels in the chest, arms or legs. It relies on a patient's heart to pump the blood through the device, with blood flowing naturally between the high pressure in an artery to the lower pressure in a vein.
In Canada and Europe, Novalung, an artificial lung made by a German company of the same name, is in clinical trials. Doctors say they are having success with temporary use.
Shaf Keshavjee, professor and chairman of thoracic surgery at Toronto General Hospital and the University of Toronto, has performed five artificial-lung procedures in the past year using the Novalung. The CD-sized device has helped support patients for up to two weeks while they awaited a lung transplant.
Oxygen transfer is the key
Finding a surface -- a membrane like the corporeal membrane in the chest -- that transfers a significant amount of oxygen while not causing blood to clot or damaging blood cells as they pass across it has been a challenge for artificial-lung developers, Keshavjee says, but they have achieved success. "The technology that has developed now works well enough to use short-term," he says. "It is a reality."
Novalung was approved in October, not yet for lung failure, but for temporary use during heart surgery.
Down the road, researchers such as the University of Pittsburgh's William Federspiel hope an implantable lung will be available to support patients with chronic diseases like asthma and cystic fibrosis.
Federspiel has been exploring an enzyme that, when used to coat the fibers in the artificial lung, accelerates the removal of carbon dioxide from the blood and may reduce the amount of blood that needs to be fed through the device, making it more efficient and safer for patients.
"The devices have come of age," Keshavjee says. "There's a real hope you can save lives with these devices. The long-term isn't there yet, but it's coming,"<>>