Obstructive Ventilatory Defect
This is a respiratory abnormality characterized by a slow rate of forced expiration (low FEV1/FVC). In those with active asthma or emphysema, a high residual volume and functional residual capacity and a low vital capacity are usually seen as well. In individuals with bronchitis these lung volumes are more likely to be normal.
Asthma, bronchitis, and emphysema are all considered obstructive conditions, but the way each results in an obstructive defect is quite different. More information about any of these diseases can be found in the appropriate encyclopedia entry.