Table. 7—

Summary of the considerations for severity classification

The severity of pulmonary function abnormalities is based on FEV1 % pred. This does not apply to upper airway obstruction. In addition, it might not be suitable for comparing different pulmonary diseases or conditions
FEV1 may sometimes fail to properly identify the severity of a defect, especially at the very severe stages of the diseases
FEV1 % pred correlates poorly with symptoms and may not, by itself, accurately predict clinical severity or prognosis for individual patients
Lung hyperinflation and the presence of expiratory flow limitation during tidal breathing may be useful in categorising the severity of lung function impairment<1?twb?>
  • FEV1: forced expiratory volume in one second; % pred: % predicted.