...in with the good

Take a breath.

Feel that?

If your lungs are functioning properly, there isn’t much to feel. In an instant, oxygen-rich blood is pumped from the lungs, to the heart, and sent into the body. At the same time, oxygen-depleted blood is pushed into the lungs, allowing you to exhale carbon dioxide.

Unfortunately, it’s not that simple for a large number of Americans. More than 12 million patients in the U.S. suffer from long-term lung diseases, which can turn the simple act of breathing into a strenuous chore. Of those who suffer, military veterans are one-and-a-half to three times more likely than typical civilians to develop long-term diseases.

“Part of that is simply that they smoke more often, and part of it is that they’re also exposed to some environmental hazards that most people aren’t,” said Keith Cook, a professor of biomedical engineering (BME) at Carnegie Mellon University.

Recently, the U.S. Army Medical Research and Material Command awarded Cook a grant to continue research and development on a pulmonary assist system (PAS) that offers long-term support for those with chronic lung disease—including veterans—as well as emergency respiratory support for soldiers wounded in battle as they’re transported from the front lines to military hospitals.

Cook’s PAS device is revolutionary in the field of extracorporeal membrane oxygenation (ECMO)—the general term for external oxygenators. His device has the potential to far outlast current ECMO devices, retaining its functionality for months rather than the current standard of days or, in some cases, hours.

This tremendous increase in the lifespan of the device means patients would be able to leave a hospital after surgery, return home, and live their daily lives with the device attached. This return to normalcy, and the improved quality of life that comes with it, is unheard of with current ECMO technology.

To develop his device, Cook is working with Dr. Matthew Bacchetta, an associate professor of surgery in the Division of Cardiothoracic Surgery at New York Presbyterian/Columbia University Medical Center. Bacchetta is also Surgical Director of the Adult Extracorporeal Membrane Oxygenation Program and a lieutenant colonel in the United States Army Reserves. Bacchetta has served as a combat surgeon in Iraq, Afghanistan, and Africa and has used ECMO devices during tours in Afghanistan.

The single biggest challenge Bacchetta has said he’s faced with current ECMO devices is that they’re extremely thrombogenic, meaning they cause a patient’s blood to clot. To prohibit clotting, anticoagulants must be introduced to thin the blood, presenting a whole new set of challenges.

“In a combat situation, you have to worry about bleeding,” said Bacchetta, who has performed more than 130 combat surgeries and transports when ECMO devices have been used.

If a patient is losing blood, it’s hard to justify giving them an anticoagulant. Without an anticoagulant, an ECMO device’s durability is greatly affected, Bacchetta said, meaning the patient won’t get the oxygen they need.

In preliminary testing, Cook’s PAS device—which pumps blood from the body and through a small artificial lung before returning it to the body—has been shown to greatly reduce the problems of clotting and blood cell damage prevalent in existing ECMO devices.

Early indicators point to the loose packing of the PAS device’s internal fiber bundles and the design of the blood flow pathways as the groundbreaking solutions to these problems.

“Part of it is the fluid mechanical design of the device, making sure that blood flows evenly through the fiber bundle,” Cook said.

Cook’s results aren’t conclusive yet, but the grant he received will allow him to conduct two-month testing on his device. This two-month timespan is remarkable because until now, other ECMO devices haven’t been able to last nearly as long.

Bacchetta said that most ECMO devices are designed for surgical support, and are only required by the FDA to demonstrate their function for a period of six hours. If Cook can show that his PAS can maintain its functionality without blood coagulation or bleeding complications for an extended period of time—months, eventually years—it would be a major advancement in ECMO technology.

“A device that would allow us to avoid clotting in the field would be a major improvement on current systems,” said Bacchetta.

Having a patient at home walking around on one of these devices, being supported for several months to even years—that’s revolutionary.

Keith Cook, Professor, Biomedical Engineering, Carnegie Mellon University

In instances where a soldier is injured in battle, leading to acute respiratory failure, the system would attach to the body via a blood vessel in the neck, sending a tube down to the heart. This allows blood to pump through the system during emergency transport so it can be oxygenated in lieu of failing lungs. Once the soldier arrives at a medical facility, they would undergo surgery to attach the PAS in a more controlled and stable way.

Doctors can also treat veterans suffering from the slow decline of chronic lung-disease by surgically attaching the PAS device for long-term care.

Currently, the surgical approach means grafting the device onto a large vein, like the vena cava. This will pull deoxygenated blood into the PAS. After the PAS oxygenates the blood, it will return the blood to the body via a second graft on an artery in the upper torso.

Each of the grafts are attached to tubing that tunnels under the skin and connects to the PAS device that is worn at waist level. Tunneling in this way forms a continuous conduit for blood flow and reduces the risk of infection since strong seals between graft and tube can be created.

“The reason why you use the graft method is that it’s more flexible,” said Cook. “If you’ve got a patient who’s outside the hospital, walking around, you get a connection that’s not going to be tugging on blood vessels.”

For this long-term care, the device’s artificial lung would need to be replaced every few months, but once attached, would give patients a return to a normal life.

Bacchetta said the long-term durability and pulmonary-specific support offered by Cook’s PAS is ideal. And according to Cook, “Having a patient at home walking around on one of these devices, being supported for several months to even years—that’s revolutionary.”

Take a breath.

Feel that?

Soon, veterans suffering from chronic lung-disease might feel the same thing.

Nothing at all.