Diagnosis
Obstruction can be measured using spirometry. A decreased FEV1/FVC ratio (versus the normal of about 80%) is indicative of an airway obstruction, as the normal amount of air can no longer be exhaled in the first second of expiration. An airway restriction would not produce a reduced FEV1/FVC ratio, would produce a reduced vital capacity. The ventilation is therefore affected leading to a ventilation perfusion mismatch and hypoxia.
Read more about this topic: Airway Obstruction