OBSTRUCTIVE VENTILATORY IMPAIRMENT (LOW FEV1/FVC)

bronchial asthma (defect reversible with beta2-agonists)

COPD (usually not reversible; sometimes reversible element exists)

acute bronchitis (with bronchospasm; difficult to differentiate from an asthmatic attack)

upper airways obstruction, eg. laryngeal carcinoma, extrinsic compression of trachea