Fig. 1From: Relationship between concavity of the flow-volume loop and small airway measures in smokers with normal spirometryGlobal and peripheral concavity indices are calculated from the maximum expiratory flow-volume curve (MEFV). Global concavity is based on forced expiratory flow at 50%, and peripheral concavity is based on forced expiratory flow at 75%, of the expired FVC. The degree of concavity is compared to the “normal” reference flows at EFE50% and EFE75%Back to article page