Ventilators and ECMO are used to give the lungs time to rest and recover from an injury. But they each have drawbacks. The highly pressurized air delivered by a ventilator can sometimes cause more lung damage and inhibit healing. ECMO uses low levels of ventilation, but isn’t meant for long-term treatment. Eventually, patients may require a lung transplant. The Organ Procurement and Transplantation Network reports 1,336 lung transplants were performed in the U.S. last year. But there aren’t enough donor lungs to go around. Those who are critically ill may die before a new lung becomes available.
ECMO is the closest thing to an artificial lung, but it isn’t meant to be a long-term solution. However, one patient recently survived on ECMO for 107 days before receiving a double lung transplant – nearly twice as long as other patients. The record-breaking survival time gave doctors hope that similar treatments could be used to sustain other patients waiting for a lung transplant. Despite the enthusiasm over the possible long-term use for ECMO, doctors say there is an important limitation of the treatment.
Bartley Griffith, M.D., a Heart & Lung Transplant Surgeon at the University of Maryland Medical Center, says patients require nutritional supplementation and must remain in bed, flat on their backs for the entire time. Those limitations interfere with their quality of life and can impede recovery and rehabilitation.
Researchers are now developing a small version of an artificial lung that may, in some cases, provide an alternative to ECMO. Griffith says the goal of the research is make the lung pump small enough to enable patients to move around, stay at home and maintain some quality of life. Griffith explains that if a human lung would be opened and unfolded, it would open to about the size of a tennis court. Thus, the challenge for researchers is being able to find an adequate substitute for all the tiny air sacs in the lungs, where oxygen and carbon dioxide are exchanged.
The lung pump under development contains special hollow, permeable fibers that mimic the action of the air sacs. As blood from the patient is passed through the pump, the fibers act like a gas exchange membrane. Oxygen moves through the fibers into the blood. At the same time, carbon dioxide is pulled out of the blood, into the fibers and then out of the pump. So far, researchers have only tested their new device on sheep. However, the outcome has been good and no complications have been seen. Griffith hopes to have a prototype ready for human clinical trials within two years. He says if the artificial lung is eventually approved, it would be useful for patients who need a temporary lung assist or those who are waiting for a lung transplant.