Table 1

 Classification of bronchiolitis obliterans syndrome (BOS)53

BOS 0-p, potential BOS stage; FEF25–75, mid expiratory flow rate; FEV1, forced expiratory volume in 1 s.
The mean of the two highest (not necessarily consecutive) measurements represents the baseline value with which the subsequent measurements are compared.
BOS 0FEV1 >90% of baseline and FEF25–75 >75% of baseline
BOS 0-pFEV1 81–90% of baseline and/or FEF25–75 ⩽75% of baseline
BOS 1FEV1 66–80% of baseline
BOS 2FEV1 51–65% of baseline
BOS 3FEV1 ⩽50% of baseline