Exhaled NO may predict the decline in lung function in bronchiolitis obliterans syndrome.

Bronchiolitis obliterans syndrome (BOS) remains the leading cause of morbidity/mortality following lung transplantation. In recipients with BOS, markers predicting the decline in lung function are needed. The aim of this longitudinal study was to determine whether exhaled nitric oxide fraction (FeNO) measurements provide useful information for discriminating patients with unstable BOS from those with stable BOS. During a 14-month period, 145 FeNO measurements were performed in 50 lung transplant recipients. Among them, 16 recipients with BOS (32 FeNO measurements) were analysed. For each FeNO measurement, the patients were classified into three groups according to the decline in forced expiratory volume in one second (FEV1) within the following 6 months: 1) stable BOS free; 2) stable BOS (decline in FEV1 of <5%); and 3) unstable BOS (decline in FEV1 of > or =15%). The mean FeNO in patients with unstable BOS was significantly increased compared with that in stable BOS-free patients (18.4+/-5.7 versus 9.7+/-3.7 ppb) and that in patients with stable BOS (18.4+/-5.7 versus 9.7+/-3.3 ppb). The present findings suggest that, in patients with bronchiolitis obliterans syndrome, a raised exhaled nitric oxide fraction may predict the development of worrisome functional impairment during long-term follow-up.