New formula used in calculations
THURSDAY, Aug. 1, 2013 (HealthDay News) -- Bigger might be better when it comes to lung transplants, a new study says.
Researchers found that lung transplant recipients who received bigger lungs were more likely to survive than those who received smaller lungs. This was particularly true among those who received double-lung transplants.
"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," study author Michael Eberlein, a clinical assistant professor in internal medicine at the University of Iowa, said in a university news release.
He and his colleagues analyzed data from nearly 7,000 patients who underwent either single-lung or double-lung transplants in the United States between May 2005 and April 2010. In the United States, height is used to determine lung size for transplant candidates.
But for this study, the researchers developed and used a formula called predicted total lung capacity (pTLC) ratio. A person's predicted total lung capacity is calculated using height and gender. Taller people have bigger lungs, and a man's lungs are larger than those of a woman of the same height, the study authors explained.
The predicted total lung capacity ratio is arrived at by dividing the donor's predicted total lung capacity by the patient's predicted total lung capacity. A ratio of 1.0 is a perfect size match, while a ratio of 1.3 indicates that the donor lung is significantly larger than the recipient's lung.
Among patients who had a double-lung transplant, each 0.1 increase in the predicted total lung capacity ratio was associated with a 7 percent decrease in risk of death a year after the procedure. Among those who had a single-lung transplant, each 0.1 increase in predicted total lung capacity ratio was associated with a 6 percent decrease in the risk of death a year later.
"This study shows that lung size matters in lung-transplant procedures," Eberlein said. "We found that oversized (lungs), 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."
The study was published Aug. 1 in the Annals of Thoracic Surgery.
Seth Force, of Emory University School of Medicine in Atlanta, commented on the study's strength in an accompanying journal editorial. "The data in this manuscript make a compelling argument for the lung transplant community, as well as (United Network for Organ Sharing), to consider changing to a pTLC method for lung sizing for listed patients," Force concluded.
The U.S. National Heart, Lung, and Blood Institute has more about lung transplantation (http://www.nhlbi.nih.gov/health/health-topics/topics/lungtxp/ ).
SOURCE: University of Iowa, news release, Aug. 1, 2013