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Dartmouth Medical School Dartmouth-Hitchcock Medical Center


Organ model seeks greatest good

By Matthew C. Wiencke

"There are still people who die waiting for lung transplantation," says DMS pulmonologist Jeffrey Munson, M.D. The reason is that there are simply not enough donated organs to meet the demand. Munson has studied this problem from many angles, including, recently, comparing the benefits of transplanting two lungs versus a single lung.

For patients with chronic obstructive pulmonary disorder (COPD), a bilateral lung transplantation (BLT) can increase survival compared to a single lung transplantation (SLT). But bilateral transplants reduce the number of lungs available to other patients.

So, Munson says, the issue comes down to a tricky ethical question.

To examine the tradeoffs, Munson and a team of researchers created a computer model of two identical groups of 1,000 simulated patients, whose characteristics and diagnoses were based on real patient data. All the patients needed transplants, as a result of either COPD or other lung diseases for which SLT is usually as effective as BLT. In one group, patients were on a waiting list for BLT. Those in the other group received SLT. The team then tracked simulated patient outcomes over a two-year period, examining movement up and down a waiting list, the number who received transplants, the number who died, and post-transplant survival. The results were reported in the American Journal of Respiratory and Critical Care Medicine.

Results: Overall, the SLT arm of the study did better. More patients received transplants (809 versus 758) and fewer died while waiting (157 versus 199). The total years survived post-transplant was about the same for both groups (4,586 years for SLT; 4,577 years for BLT). Munson believes the results show that SLT may be a better approach in terms of the benefit to society as a whole.

But when the researchers simulated scenarios with shorter waiting lists and more lungs available for donation, patients lived longer after a BLT. And the outcomes varied by region as well. One northeastern region had 368 fewer years of total survival and 75 more deaths on the waiting list for BLT. But a region in the western U.S. had 215 more years of survival and just 14 more deaths for BLT.

So, Munson says, the issue comes down to a tricky ethical question as to what is the most important outcome. "Is it the number of people you transplant or is it the total survival of the transplant population?" he says. "You can make an argument for both."

Munson's hope is that the study encourages more dialogue on this tough issue. "When you decide to do mostly BLT in your COPD population, that has implications for other patients on the transplant list, and we need to talk about what those implications are," he says. Traditionally, he adds, doctors have tried to take care of the individual in front of them, without considering the implications for other patients. But given limited resources, he says, "maybe that blind allegiance to the individual should be reconsidered."

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