Expansion
Obstruction traps gas and raises volumes; restriction reduces all volumes
Expansion
| Obstructive | Restrictive | |
|---|---|---|
| Problem | Airflow out | Lung expansion in |
| FEV1/FVC | Low | Normal or high |
| Total lung capacity | Normal or high | Low |
| Residual volume | High (gas trapping) | Low |
| Compliance | High (emphysema) | Low |
| Breathing pattern | Slow and deep | Rapid and shallow |
| Chest shape | Hyperinflated, barrel | Small volume |
Diffusing capacity helps subdivide further: it is reduced in emphysema and in fibrosis (loss of surface area), but normal or raised in asthma and in chronic bronchitis, and raised in pulmonary haemorrhage.
Within restriction, the site matters. Intrinsic (parenchymal) restriction such as fibrosis reduces compliance and diffusing capacity; extrinsic restriction from neuromuscular weakness, obesity or chest wall disease reduces volumes with preserved diffusing capacity, and is suggested by a low maximal inspiratory pressure.