In an obstructive type of ventilatory impairment the impairment is the result of an airway obstruction as the result of bronchial obstruction, as in asthma, or obstruction in other parts of the airway, e.g. laryngeal oedema, carcinoma.
This type of ventilatory impairment is characterised by a reduction in VC and FEV1. The relative reduction in FEV1 is greater than the reduction in VC and hence there is a reduction in the forced expiratory ratio, FEV1/FVC, that makes the value below 0.70.
Note that though pulmonary conditions - for example pulmonary fibrosis and parenchymal infiltration - generally produce a restrictive ventilatory impairment, an obstructive pattern may be seen.
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