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Pitt at work on 2 kinds of breathing machines
Thursday, April 26, 2001 By Byron Spice, Science Editor, Post-Gazette
Researchers at the University of Pittsburgh will reveal today that they are working on an artificial lung that one day might take over a person's breathing functions for months at a time while the patient waits for a lung transplant.
The device, which is probably several years away from full development, would be surgically connected to the heart and worn outside the body in a cartridge the size of a CD player, allowing the patient to walk around. It would perform all of the oxygen and carbon dioxide exchange that the body needs.
The news comes as the researchers at Pitt's McGowan Center for Artificial Organ Development are also announcing that they are getting close to human testing of a smaller, short-term lung assist device.
The scientists said animal tests of the assist device have been encouraging and they expect to begin clinical testing in emphysema patients by autumn 2002.
The temporary device, called the Hattler Respiratory Catheter, is inserted into the large vein that carries blood back to the heart. It would add oxygen to the blood while removing carbon dioxide for up to two weeks while the patient's lungs recover from an injury or from an acute disease, such as pneumonia.
More than 3,700 Americans were on the waiting list for lung transplants as of Friday and 25 to 30 percent of them are likely to die before they get a transplant, said Dr. Brack Hattler, a cardiothoracic surgeon who has led development of the temporary lung assist device.
Hattler will update transplant surgeons about work on the breathing devices today as he presents a keynote address at the annual meeting of the International Society for Heart and Lung Transplantation in Vancouver, British Columbia.
Transplant surgeons are eager for a mechanical "bridge" that would keep patients alive until donor lungs become available, in much the same way that heart assist devices now sustain heart transplant candidates.
Help for damaged lungs is now limited. Mechanical ventilators, which force oxygen into the lungs, are of limited use when the lung itself is damaged. The heart-lung machines that are used to keep patients alive during heart surgery can also be used as artificial lungs, but they are complex, expensive and prone to complications.
The Hattler catheter uses thin, porous fibers that look like the bristles on a paint brush to release oxygen into the blood and to pump carbon dioxide out. Hundreds of the fibers are wrapped around a balloon, which works to swish the fibers around as it inflates and deflates.
The catheter is narrow enough that it can be quickly inserted through a vein in the upper leg and threaded into the vena cava, a large vein. The catheter is connected to an external pump that inflates and deflates the balloon and moves oxygen and carbon dioxide in and out.
William Federspiel, a chemical engineer working on the project with Hattler, said the device has been tested successfully in calves for a week at a time. The design is now being readied for clinical trials with humans, which could begin next year in Europe.
Federspiel and Hattler have founded a company, Alung Technologies, to produce the devices.
Much of the funding for the Hattler catheter has come from the Defense Department, which is interested in a device that could help soldiers who are exposed to biological weapons, such as anthrax.
But the Hattler catheter can provide for only about half the body's gas exchange needs.
The Hattler's combination of hollow fibers and agitation has been so successful that researchers think it could provide the basis for an artificial lung that could meet all the body's needs.
"It's a very complicated organ to reproduce in plastic," said Dr. Bartley Griffith, UPMC chief of cardiothoracic surgery. But Hattler's success inspired Griffith and others to try to develop a lung replacement -- what they call the chronic artificial lung -- that could handle all of the body's needs.
The device would be surgically attached to the heart's right ventricle, which normally pumps blood to the lungs. The blood would instead be diverted outside the body and into the artificial lung. Rather than being wrapped around a cylinder, as in the Hattler catheter, the fibers would be formed into a disk that rotates.
By happy coincidence, the rotating disk not only mixes the blood with the fibers, but works as a centrifugal pump, Griffith said. The blood would circulate back into the body and through the lungs. The blood would then return, as normal, to the left side of the heart, which would pump the oxygenated blood throughout the body.
The idea to leverage Hattler's concept took hold four years ago. Last spring, Griffith obtained a four-year award worth almost $1 million a year from the National Institutes of Health to develop the artificial lung. Early 24-hour tests in animals have gone well, Griffith said.
He said a clinical trial is still several years away. In the meantime, a McGowan researcher, Philip Litwak, has established a company called Ension Inc. to adapt the technology to replace the conventional heart-lung machines used in surgery.
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