Table 1

Different mechanisms reducing singlebreath alveolar volume (VA) in respiratory disease

DiseaseMechanismsPrototypeOther examples with comments
Restrictive disease with a small TLC and normal VA/TLC ratioLack of lung expansion: lung structure normal Loss of units: remaining lung structure normal Diffuse alveolar damageAcute inspiratory muscle weakness Pneumonectomy Fibrosing alveolitisChest wall disease and pleural disease, but lack of expansion is usually nonuniform Local alveolar infiltrate or collapse, consolidation or local destruction Pulmonary oedema, congestive heart failure, mitral stenosis, bleomycin lung, Wegeners granulomatosis. In all these conditions, severity of alveolar involve- ment varies and some normal alveoli survive and contribute to CO uptake
Obstructive disease with normal or increased TLCSampled VA<TLC due to incomplete mixing during breath-holdingEmphysemaIncomplete mixing may be associated with alveolar destruction, space-occupying lesions (bullae) or normal alveolar structure (asthma)
  • TLC: total lung capacity.