Impact of Forced Expiratory Volume in 1 Second (FEV1) and 6-Minute Walking Distance at 3, 6, and 12 Months and Annually on Survival and Occurrence of Bronchiolitis Obliterans Syndrome (BOS) After Lung Transplantation

Background: Development of bronchiolitis obliterans syndrome (BOS) is a great limitation for patient survival in lung transplantation (LTx). A curative treatment for BOS is still missing, and in terminal stages re-transplantation (Re-LTx) is the only salvation. It is possible to slow the progress of BOS if it is detected at an early stage. This might be possible by assessing pulmonary function pattern. Material/Methods: Between 1990 and 2014, 278 patients underwent LTx at Skane University Hospital, Sweden. Pulmonary function was followed using spirometry (FEV1) and 6-minute walking test (6MWT) measured at 3, 6, and 12 months and annually. The endpoint used was freedom from BOS (BOS grade <= 1), BOS (BOS grade >= 2), and death or Re-LTx. Results: Double-lung transplantation (DLTx) showed a hazard ratio (HR) of 0.514 (p=0.001) versus recipients who underwent single-lung transplantation (SLTx). Regarding freedom from BOS, FEV1 showed an HR of 0.597 and 6MWT an HR of 0.982 (p<0.001). Regarding combined endpoint BOS >= 2 and Re-LTx, FEV1 showed an HR of 0.618 and 6MWT an HR of 0.972 (p<0.001). Conclusions: Recipients with higher FEV1 or 6MWT values had better chances of survival. Recipients with DLTx had a significant survival benefit and a protective effect against development of BOS. As the distance that the patient can walk in 6 minutes increases, risk for death or Re-LTx is significantly lower, as is incidence of developing BOS grade >= 2. Understanding changes within pulmonary function are probably key to understanding patient prognosis.