April 26, 2001 -- Acute respiratory distress syndrome, or ARDS, will affect about 200,000 Americans this year, according to some estimates. As many as half of those people will die, often because the ventilators used to treat them can cause permanent, irreversible lung damage. But a University of Pittsburgh researcher says he is ready to begin human tests of a device that can temporarily replace damaged lungs -- and thus save lives.
ARDS is characterized by a rapid and progressive breakdown of the lungs that impairs their ability to take in oxygen. It is usually associated with the failure of other organs as well and is generally caused by trauma, infection, severe pneumonia, or shock.
Brack Hattler, MD, PhD, tells WebMD that he and his colleagues have been working on their device for 14 years and are ready to begin human testing in Europe sometime next year.
Hattler brought a group of transplant experts up to speed on the latest artificial lung technology with a speech at the International Society for Heart and Lung Transplantation meeting in Vancouver, British Columbia.
A professor of surgery at the University of Pittsburgh, Hattler says the U.S. Department of Defense first asked him to work on developing a "temporary lung" during the days leading up to the Gulf War as they were worried that Iraqi forces led would use chemical weapons against allied forces. Those toxic chemicals can cause severe lung injuries, but not permanent ones. If the lungs were given a breather and allowed to recover, Hattler says, "the damage could be reversed."
This kind of damage is very similar to what is seen in patients with ARDS. Currently patients who have this type of injury are put on a ventilator, which mechanically supplies oxygen and forces the lungs to breathe. Unfortunately, both actions can cause permanent damage.
So the goal was to develop a device that could be "easily used and could replace the lungs for a brief period of about 5 to 14 days," Hattler says. The device developed by his team works inside a vein in the leg to supply oxygen to the blood.
He explains that external controls regulate the amount of oxygen supplied as well as the rate at which carbon dioxide is vacuumed out of the blood.
Hattler says that although this device is the first major breakthrough in artificial lung technology, it does build on earlier technology.
Several years ago a venture capital company introduced the concept with IVOX, a device that supplies oxygen to the veins. That product was "actually tested in humans," says Lyle Mockros, PhD, but it was eventually abandoned when the developers ran out of money. Mockros is a professor of biomedical engineering at Northwestern University in Chicago.
Mockros says his group at Northwestern, as well as a third team at the University of Michigan, are concentrating their efforts on developing a more permanent artificial lung that could be used longer-term while a patient waits to get a lung transplant, says Mockros. Current work is focused on devices that are wearable and are attached to the patient.
Physicians have been trying to adapt the heart-lung machine for use as an artificial lung for people with severely damaged lungs, such as people with severe emphysema, Mockros says, but efforts have not been successful.
The difficulty in developing a successful artificial lung is that the lungs, he says, have a large surface area and devices that mimic them also have a large surface area. When blood passes over a large artificial area, it can be damaged in a way that causes the formation of blood clots. Designers seek to overcome this risk by giving patients powerful anticlotting drugs, but those can lead to unintended bleeding.
Hattler's device is much smaller, so the surface area is less, and the anticlotting drug heparin has actually been built into the device. This approach reduces the risk for clot formation, Hattler says.
If Hattler's device is successful in human studies, Mockros says it will be a major advance in the world of artificial lungs.