An estimated 200,000 people die from lung disease in the United States each year, many while waiting for a transplant.
Keith Cook, a research associate professor of surgery, hopes to lower that number by developing a thoracic artificial lung, also known as a TAL. The device will serve as a “bridge to transplant” by performing the function of natural lungs until the patient is able to receive treatment, Cook said.
“What happens to these patients is that they get progressively worse and worse and worse,” Cook said. “It’s almost as if you have to achieve some sort of magic to get on the waiting list. You have to get worse and worse and worse, but not horribly worse.”
TALs — which are about the size of a book and are composed of plastic and a bundle of fibers used to oxygenate blood — sit outside the body and are connected to the pulmonary artery by a graft that pumps blood into the device. Though it has only been tested on sheep so far, Cook said it has received positive results.
“That’s very much the way your natural lung works,” Cook said. “Your natural lung receives blood from the pulmonary artery and returns blood to the left atrium.”
In the sheep trials, the researchers found that the lungs have stayed clean and had no change in resistance after 14 days, whereas normally the blood flow resistance in the lungs would triple over nine days due to clotting.
As opposed to extracorporeal membrane oxygenation — the current oxygenation system for patients who need lung transplants — attaching the TALs to the pulmonary artery requires an invasive surgery. Cook said he believes the benefits TALs provide are greater than those of ECMO.
Specifically, he noted that they remove much of the circuitry of ECMO, are gentler on the blood, work more like a natural lung and allow the patient to be mobile instead of bed ridden.
Cook noted that in order to receive a transplant, patients have to be physically strong enough to handle the operation. If patients are bed-ridden they often are never able to build up the necessary strength.
“If you have a patient that is decompensating and needs a lung very soon, ECMO is a good mode of support,” Cook said. “Now, if you need to go beyond that period (of a few weeks), I think that the patient will be far better served by having a thoracic artificial lung.”
David Skoog, a graduate student research assistant in biomedical engineering who builds the lungs for testing, said it takes a few weeks to build one because they are all handmade.
“Since there are a lot of steps in the process, we always have several lungs being made at the same time, just at different stages in the process because it’s so time consuming,” Skoog said. “Otherwise we’d never be able to produce enough devices to do our experiments.”
Cook added that the TALs currently being tested didn’t have an anticoagulation coating on them, adding that he believes with the addition of a coating, the lungs could last up to a month without having to be replaced.
Cook said his ultimate goal is to support all the patients who won’t ever make it to the transplant list. However, he said he is unsure as to when TALs will make it to human clinical trials.
“The answer is always five years (until clinical trials). We always say five years,” Cook said.