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.