Small Airways Function Declines After Allogeneic Hematopoietic Stem Cell Transplantation

Word count: 218 words) Bronchiolitis obliterans (BO) following allogeneic hematopoietic stem cell transplantation (HSCT) affects peripheral airways. Detection of BO is presently delayed by the low sensitivity of spirometry. We examined the relationship between peripheral airway function and time since HSCT, and compared it with spirometry and clinical indices in 33 clinically stable allogeneic HSCT . Published on May 12, 2011 as doi: 10.1183/09031936.00018311 ERJ Express Copyright 2011 by the European Respiratory Society. recipients. Measurements of lung function, exhaled NO, forced oscillatory respiratory system resistance and reactance, acinar (Sacin) and conductive airways (Scond) ventilation heterogeneity and lung clearance index (LCI) measured by multiple breath nitrogen washout were performed. Twenty-two patients underwent repeat visits from which short term changes were examined. Median time post HSCT was 12 months. Eight patients were clinically diagnosed as having BO. In multivariate analysis, time since HSCT was predicted by Sacin and FEV1 %predicted. Twenty patients had abnormal Sacin with normal spirometry, whereas none had airflow obstruction with normal Sacin. Sacin and LCI were the only measures to change significantly between 2 visits, with both worsening. Change in Sacin was the only parameter to correlate with change in chronic graft-versus-host disease grade. In conclusion, peripheral airways ventilation heterogeneity worsens with time after HSCT. Sacin may be more sensitive than spirometry in detecting BO at an early stage, which needs confirmation in a prospective study.