A new formula for identifying lung transplant candidates reveals that oversized lungs lead to improved survival following transplantation, especially for patients receiving bilateral lung transplants, according to University of Iowa researchers.
Michael Eberlein, clinical assistant professor in internal medicine at the University of Iowa, developed a new formula, called predicted total lung capacity (pTLC). Instead of using height to identify potential recipients — as is currently practiced — the pTLC ratio is calculated using both height and gender. The pTLC-ratio is determined by dividing the donor’s pTLC by the patient’s pTLC. A ratio of 1.0 is a perfect size match, whereas for example a ratio of 1.3 indicates that the donor lung is significantly larger than the patient’s lung.
Eberlein noted that while it is commonly believed transplanting oversized lungs is problematic, “no data were available to substantiate that idea.”
In single-lung transplants, each 0.1 increase in pTLC-ratio was associated with a 6% decrease in the risk of death a year later; however, this association was not present following the same additional adjustment to account for any bias to oversizing.
Those undergoing double-lung transplants, each 0.1 increase in the pTLC ratio was associated with a 7% decrease in risk of death a year after the procedure. This decrease was still independently associated with improved survival following additional adjustment to account for any bias to oversizing.
“This study shows that lung size matters in lung-transplant procedures,” said Eberlein, lead author of the study. “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.”