Machine kept the man alive 107 days until he received a double lung transplant
A patient at the University of Maryland Medical Center was kept alive on an artificial lung system longer than anyone else in the world. The 24-year-old man remained on a system called ECMO (extracorporeal membrane oxygenation) for 107 days until he received a double-lung transplant. The previous longest ECMO survivor reported in the medical literature was a patient in Michigan, who had been on the machine for 57 days. This man’s experience is encouraging to University of Maryland researchers who are working to develop a small, portable artificial lung.
The patient, Timothy McClellan, of Fairfax, Virginia, was flown to the medical center’s R Adams Cowley Shock Trauma Center from Western Maryland, where he sustained a severe head injury on October 26, 2006. As the Shock Trauma team worked to save his life, his head trauma caused a type of lung damage that can be associated with head injuries, called adult acute respiratory distress syndrome. His lungs went into shock, causing them to scar and become stiff or fibrous. He needed to remain on ECMO support until he received the double-lung transplant on February 28, 2007.
ECMO technology is more than 20 years old. It is a simplified version of a heart-lung machine and employs a pump to circulate blood through an artificial lung and back to the bloodstream. It infuses the blood with oxygen and removes carbon dioxide, similar to healthy lungs. A person who is on the system must remain lying down with tubes placed in the neck and groin. ECMO is most often used in infants with a reversible breathing or heart problem whose heart or lungs can benefit from a temporary rest.
“We supported this patient’s complete respiratory requirements throughout his illness because his lungs could not provide for his needs,” says Bartley P. Griffith, M.D., director of Heart and Lung Transplantation at the University of Maryland Medical Center and professor of surgery and chief of the Division of Cardiac Surgery at the University of Maryland School of Medicine, who performed the lung transplant.
Dr. Griffith attributes the patient’s lengthy survival on ECMO to the expertise of specialists at the University of Maryland Medical Center, including the Shock Trauma team, led by Nader M. Habashi, M.D., medical director of the Multi-Trauma Intensive Care Unit and an associate professor of medicine at the University of Maryland School of Medicine. All have vast experience dealing with people who have complicated lung cases.
“Many of our patients require ECMO assistance to get them through breathing difficulties,” says Thomas M. Scalea, M.D., physician-in-chief at the Shock Trauma Center and director of the Program in Trauma at the University of Maryland School of Medicine. “But the extraordinary length of time that Mr. McClellan required ECMO made this case quite unusual.”
Aldo T. Iacono, M.D., medical director of the lung transplant program at the University of Maryland Medical Center and associate professor of medicine at the University of Maryland School of Medicine, says, “Mr. McClellan and his family kept a positive outlook and remained hopeful for a transplant. That helped him through the long ECMO experience. Nevertheless, the patient’s recovery has been challenging even after the transplant, due to his head trauma, inactivity while on ECMO and other medical issues.”
Dr. Iacono sees added significance in this patient’s ECMO course because it was used as a bridge to keep him alive until a lung transplant became available. ECMO is rarely used as a bridge to transplant but this case suggests it is feasible and there is a place for a more technologically advanced lung system that is superior to the present ECMO.
Along that line, Dr. Griffith adds, “this experience with ECMO has reinforced my commitment to one of our major areas of research, artificial lung development.”
Dr. Griffith and researchers at the University of Maryland School of Medicine hope to move beyond the cumbersome ECMO therapy by engineering an artificial lung that would be portable, similar to many types of heart pumps or ventricular assist devices available today. The Maryland team has developed and evaluated numerous innovative blood pumps to support patients with failing hearts, but Dr. Griffith believes that patients with lung failure are underserved. “They suffer with each attempt to catch a breath and represent one of the patient groups most in need of better therapies,” he says.
Dr. Griffith says ECMO is a good temporary option for children and adults who are bound to an intensive care setting. But he notes that there is a need for more comfortable and more effective lung assist/replacement devices that are portable. He says a survey of lung transplant program directors indicates a strong inclination to use promising investigational devices to support transplant candidates near death who are waiting for a scarce donor organ.
According to the National Heart, Lung, and Blood Institute, acute respiratory distress syndrome affects 150,000 people yearly, killing 30-40 percent of those patients. Only about 1,600 lung transplants are performed annually in the United States, due to restrictions on donor criteria and limited donor organs. Each year, 10 percent of patients on the lung transplant waiting list die before an organ becomes available.
It is those statistics that are driving the development of a modern artificial lung. Several groups in the U.S. are working on respiratory support devices.
The University of Maryland team, led by Dr. Griffith, has two grants from the National Institutes of Health to develop a portable artificial lung and pump combination that a patient could carry in a small case. Unlike other experimental artificial lungs which involve several separate parts, this device would integrate all aspects of an artificial lung into a single unit. It combines a pump similar to that used in heart pumps to circulate blood through a small array of hollow micro fiber membranes where the carbon dioxide and oxygen exchange occurs. The membranes do the work of the natural lung’s alveoli.
University of Maryland engineers continue to refine the design of the device while it undergoes testing in animal models. Zhongjun Wu, Ph.D., an assistant professor of surgery and director of the artificial organs laboratory at the University of Maryland School of Medicine, says the pump portion has no bearings or other moving parts that might wear out.
The researchers estimate it will take another two years of development before the University of Maryland’s artificial lung is ready for human testing.
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