Aug 06, 2013 09:07 AM EDT By Staff Reporter, UniversityHerald Reporter

Oversized lungs used in transplants lead to better survival rates after surgery when compared to patients, who receive a smaller organ, according to a study conducted by researchers from the University of Iowa. This finding particularly holds true for patients receiving double-lung transplants.

The findings of the study are published in the journal The Annals of Thoracic Surgery.

"An unresolved question in the field of lung transplantation is how the size of the donor lungs relative to the recipient affects transplant success. It is commonly believed that transplanting oversized lungs is problematic, but no data were available to substantiate that idea," said Michael Eberlein, study author and a clinical assistant professor in internal medicine at the University of Iowa.

Eberlein and his team arrived at the conclusion after analyzing data from nearly 7,000 patients who underwent either single-lung or double-lung transplants in the U.S. between May 2005 and April 2010.

In the U.S., height is used to determine lung size for transplant candidates. But Michael Eberlein, clinical assistant professor in internal medicine at the UI, and colleagues developed a new formula, called 'predicted total lung capacity ratio,' (pLTC) to identify the perfect match based on the size of a lung.

The pLTC is calculated by the height and gender. Taller people have bigger lungs and male lungs are larger than female's of similar height.

The predicted total lung capacity ratio can be obtained by dividing the pLTC of the donor with the patient's pLTC. Researchers found that a ratio of 1.0 is a perfect size match, while a ratio of 1.3 means donor's lung is significantly larger than the recipient's lung.            

"This study shows that lung size matters in lung-transplant procedures," said Eberlein. "We found that oversized allografts, up to a point, were associated with improved survival after lung transplantation. We would hope that recipients, within surgically feasible limits, could be listed for higher donor height ranges and ultimately have a better chance of receiving an acceptable donor lung."

According to the study, a seven percent lower risk of death was observed in a patient who had a double-lung transplant with a 0.1 increase in the pLTC ratio, a year after surgery. A six percent lower death risk was observed in patients with a single lung transplant surgery.

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