Table 1 Definition of obstructive airway syndromes
AsthmaEpisodic respiratory symptoms
Variable airflow obstruction occurring spontaneously, with treatment or after provocation
COPDIncompletely reversible airflow obstruction
Overlap syndromeAsthma and COPD—that is, symptoms of increased variability of airflow and incompletely reversible airflow obstruction
Chronic bronchitisSymptomatic mucus hypersecretion with cough and sputum daily for at least 3 months over 2 years
EmphysemaAbnormal airspace enlargement
Variable airflow obstructionIncreased diurnal variability of peak flow: maximum–minimum/average >10%
Increased response to bronchodilator: >200 ml FEV1 and >12% baseline
Increased airway responsiveness: provocation dose or concentration <normal
Incompletely reversible airflow obstructionPostbronchodilator FEV1 <80% predicted and FEV1/FVC <70%
Bronchodilator responsivenessImprovement in FEV1 >15% and 400 ml after a therapeutic dose of inhaled rapid acting β2-agonist
Airway hyper-responsivenessSignificant fall in FEV1 from a stable baseline after inhalation of bronchial provocation stimulus occurring at a stimulus dose less than required to induce a significant change in FEV1 in healthy controls.
  • COPD, chronic obstructive pulmonary disease; FEV1, forced expiratory volume in 1 s; FVC, forced vital capacity.