1993 Classification | 2002 Classification | ||
FEV1 ≥80% of baseline | FEV1 >90% of baseline and FEF25–75% >75% of baseline | BOS 0 | |
FEV1 81–90% of baseline and/or FEF25–75% ≤75% of baseline | BOS 0‐p | ||
BOS 1 | FEV1 66–80% of baseline | FEV1 66–80% of baseline | BOS 1 |
BOS 2 | FEV1 51–65% of baseline | FEV1 51–65% of baseline | BOS 2 |
BOS 3 | FEV1 ≤50% of baseline | FEV1 ≤50% of baseline | BOS 3 |
FEV1: forced expiratory volume in one second
FEF25–75%: forced mid-expiratory flow rates