Artificial Lung Closer to Clinical Trial
Long-Term Problems continued...
The BioLung, however, does not use a mechanical pump, nor does blood ever leave the body. A little larger than a soda can, it is implanted in the chest. The patient's own heart pumps blood into the device, which is packed with hollow plastic fibers perforated with holes so tiny that only gas molecules can pass through them. As blood filters through the fibers, carbon dioxide escapes through the holes and is replaced by oxygen from the surrounding air. Then the blood may go directly back to the heart to be pumped to the rest of the body, or it may take a spin through the patient's lungs first.
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.