Lexington, KY - Some of the most critically ill victims of H1N1 influenza now have better odds of beating the deadly disease, thanks to an invention developed by two doctors at the University of Kentucky.
Dr. Joseph B. Zwischenberger, the Johnson-Wright Professor and chairman of UK's department of surgery, and Dr. Dongfang Wang, director of UK's Artificial Organ Laboratory, devised an improvement for the Extracorporeal Membrane Oxygenation (ECMO) machine, commonly called a lung bypass.
The new cannula costs about $2,000, compared to older models that cost about $400. Zwischenberger described it as "an advance in a single component of a complex system. Briefly, the system is a simplified heart/lung machine that includes a cannula for draining and reinfusing blood, a pump for pumping the blood, and a gas exchanger that removes carbon dioxide and adds oxygen to the blood."
The FDA approved the UK doctors' double lumen catheter (DLC) in October 2008. UK was the first medical center to have it available for patients, in January 2009. The device, known as the Avalon Elite Bi-Caval DLC, is less invasive, allows for patient mobility, offers total/more efficient exchange of blood gases and lessens the chances of infection.
The DLC is inserted directly into the patient's right internal jugular vein in the neck. The drainage lumen is open to both the superior vena cava and inferior vena cava of the heart to maximize venous drainage. A separate collapsible infusion lumen, open to the right atrium, facilitates the return of blood through a single insertion site.
While prior versions of the ECMO machine saved the lives of critically ill babies and small children, they had serious limitations. No machine was large enough for adults or older children. Tubes tended to kink or collapse, and the machines were not as efficient as they needed to be in the exchange of blood gases.
The flu epidemic hit Australia and New Zealand during July and August of 2009. Patients who were the sickest could not breathe without ventilators, prolonged use of which causes lung damage. Sixty-eight H1N1 patients who failed to recover, despite support from ventilators, were given ECMO treatment. About 71 percent survived.
Dr. Robert. H. Bartlett, Emeritus Professor of Surgery at the University of Michigan, predicted on www.mdconsult.com that "In five or 10 years, every ICU will have this capability, and there are a thousand of those."
Counts vary on how many U.S. hospitals have the ECMO machine, but the estimates range from 70 to 120. The major drawback is cost.
"ECMO requires an institutional investment in capital and, more importantly, trained physicians and nurses," Zwischenberger said. "ECMO requires dedicated equipment with costs of up to $100,000 start-up and about $20,000 per patient, with increased staffing over and above normal ICU patients (often two caregivers for each patient)."
In addition, the numbers of patients needing the specialized treatment are relatively small. "Many centers (are) doing less than five patients per year and only a few busy centers (are) doing more than 20 per year. Most predict ECMO will still be limited to major health care centers in the future," Zwischenberger explained.
He was cautiously optimistic about the potential of the DLC. "More experience is necessary to assess cost versus risk, versus benefit, of this new technology. Early results are very promising."
The University of Michigan Medical Center maintains a voluntary data repository tracking the number of H1N1 cases treated with ECMO at medical centers across the country. More than 200 cases have been reported.
Research into ECMO is one part of a big picture. Lung failure, the fourth leading cause of death in the United States, affects patients of all ages. Compared to other states, Kentucky has very high rates of lung cancer, emphysema, bronchitis and chronic obstructive pulmonary disease (COPD). These diseases are related to the state's high smoking rates.
When the lungs are so damaged that they can't heal, the only current treatment is transplantation. Unfortunately, the demand for donor lungs is much greater than the supply.
People who need kidney transplants can be kept alive by dialysis while they wait for donor kidneys. People who need heart transplants also have an option that buys them waiting time, the ventricular assist device (VAD). No suitable bridge to lung transplantation exists at this time.
Zwischenberger, a Kentucky native and a graduate of UK's Medical School, brought the DLC project with him when he was recruited from the University of Texas Medical Branch in 2007 to become chairman of the department of surgery. He has worked for 25 years on developing an artificial lung. Both he and Wang, partners for the last nine years, believe that the DLC is an important step toward achieving an artificial lung.
"UK is now well-positioned to be a leader in this field," Zwischenberger said.