Clinical diagnosis of obstructive and restrictive lung disease
Lung function tests entailing the measurement of FEV1, the vital capacity, and optionally maximum expiratory flow-volume curves, may be used to assess the presence of an obstructive syndrome.
Restrictive ventilatory defects cannot be diagnosed from spirometric tests, as an abnormally small lung characterizes them. Hence the presence of restrictive lung disease can only be demonstrated or excluded by measurements of the total lung capacity, mostly performed by gas dilution tests or plethysmographic measurements.
Obstructive as well as restrictive syndromes are caused by a multitude of clinical diseases; on that account a particular pattern of lung function tests is never characteristic of any single disease.