Artificial Lung Closer to Clinical Trial

People who need a lung transplant can only wait and hope that a donor organ will materialize in time. But all too often, time runs out.

In response to the United States' critical shortage of donor organs, researchers have been racing to develop artificial organs that would serve as a "bridge" to transplantation. One such device is the BioLung, which may be tested in people soon.

Robert Bartlett, MD, surgeon at the University of Michigan Medical Center, leads the research on the BioLung, and Michigan Critical Care Consultants (MC3), a company in Ann Arbor, Mich., makes the device. Bartlett is well known in this field: He is credited with inventing the current generation of artificial breathing machines.

For eight years, the Ann Arbor team, with support from scientists at other universities, has been trying to invent a device that can do what today's machines cannot: supply 100% of a patient's oxygen needs by using the heart's own pumping power. "It took those eight years of iterations to meet those design requirements," says Scott Merz, president of MC3.

The system now used in hospitals is known as ECMO, or extracorporeal membrane oxygenation. ECMO machines take over the functions of both the lungs and heart, pumping blood and exchanging carbon dioxide for oxygen outside the body. Bartlett says ECMO works well for patients who have had respiratory failure because of infections, such as pneumonia, or trauma, such as smoke inhalation. They only need to stay on the machine briefly, until their lungs have healed enough to begin breathing normally.

Long-Term Problems

While ECMO is a short-term lifesaver, it's not good for long-term use. Many people whose lungs are in such bad shape that they need a transplant -- such as sufferers of severe emphysema, cystic fibrosis, and pulmonary fibrosis -- do not survive on ECMO long enough to match them with a donor organ.

To keep the blood moving through the machine without clotting, patients get a blood-thinning drug. The blood thinner can cause bleeding. If blood clots do form, they can damage the brain and other vital organs. What's more, Merz says the mechanical pumps used in ECMO damage red blood cells -- the cells that carry oxygen.

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.