Artificial Lung Closer to Clinical Trial
Long-Term Problems continued...
There are advantages and drawbacks either way: Directing blood
through the lungs may help filter out blood clots, because the lungs have a
natural ability to do so. Also, the fresh supply of oxygen to the lung tissue
may help heal it. But that puts a heavier load on the heart, raising the risk
for heart failure. By sending the blood directly to the heart instead, it is
possible for the artificial lung and the natural lungs to share in breathing.
But that could let clots enter the bloodstream.
The BioLung is not meant to be a lifelong replacement for
diseased lungs. At best, researchers hope to buy time for those awaiting a
transplant and let them live relatively normal lives while they wait, rather
than be tethered to a heavy life-support unit.
After nearly a decade at the drawing board, "We are looking
at what we consider final design changes," Merz says. Clinical trials may
get under way in one to two years. The National Institutes of Health recently
granted Bartlett $4.8 million to continue the research.
Early animal studies have been promising. In the latest study,
University of Texas researcher Joseph Zwischenberger, MD, tried out the BioLung
on sheep whose lungs had been badly burned by inhaling smoke. Six of the eight
sheep on the BioLung survived five days, whereas only one of six sheep on an
external breathing machine survived that long.
Meanwhile, Bartlett has been testing the waters for future
human trials. "What we wanted to do was see what the transplantation
centers were thinking," he says. So he sent them a survey.
Thirty-one transplant centers completed the survey -- and those
were responsible for 72% of all lung transplants in the United States in 1999.
Most said they would like to see the BioLung studied in fewer than 25 animals
for 30 days before beginning to test the device on humans. Almost all of them
said they would support and participate in a clinical trial.
"The FDA would have the final word," Bartlett says.
"This is just a start."
A one-month study on two dozen animals may seem hasty, but the
situation is dire. Last year, 1,054 people received lung transplants, but 477
died on the waiting list. As of August this year, 3,797 people were still
waiting to be matched to a donor.
Most of the transplant centers that responded to Bartlett's
survey said the device should be tested first on people with idiopathic
(meaning "of unknown cause") pulmonary fibrosis. Among the sickest of
these patients, few survive longer than three months.