For decades, heart and lung transplant surgeons have followed a strict directive: Get the donor organ into the recipient as soon as possible. That practice may be changing. In a study published Wednesday in the New England Journal of Medicine, researchers said both the number of donor lungs and successful transplants may be dramatically increased by treating the organs on a perfusion machine for several hours before transplantation. The technique marks a paradigm shift in the transplantation field, experts said. About 85% of lungs made available for donation are not used because of tissue damage that potentially could be repaired with perfusion or other techniques.