This reduction is especially noticeable in the first second of air breathed out in a single breath, called FEV1—forced expiratory volume (in one second), which typically is reduced even more than the FVC.

在患者用力呼气的第一秒，这种减少更为明显，此时的呼气量称为FEV1（第一秒用力呼气容积）；它的降低甚至比FVC更明显。