Airflow Obstruction (or Obstructive Ventilatory Defect)
The medical term you're looking for is "airflow obstruction" or "obstructive ventilatory defect", which is characterized by a disproportionate reduction of maximal airflow during exhalation relative to lung volume 1.
Key Physiological Mechanism
When airway inflammation occurs, it causes:
- Bronchoconstriction - bronchial smooth muscle contraction that narrows the airways 2
- Airway edema - swelling from inflammation that further limits airflow 2
- Mucus hypersecretion - formation of mucus plugs that obstruct airways 2
These inflammatory changes specifically impair the expiratory phase, causing a shortened or slowed exhalation that is reflected in reduced forced expiratory volume in one second (FEV₁) and a reduced FEV₁/VC ratio below the 5th percentile of predicted values 1.
Clinical Manifestation
The hallmark finding is:
- Slowing in the terminal portion of the spirogram - the earliest change associated with airflow obstruction 1
- Concave shape on the flow-volume curve - visually demonstrates the expiratory flow limitation 1
- Reduced FEV₁/FVC ratio - the defining criterion for obstructive defect 1
Specific Terminology by Context
The precise term varies slightly by clinical context:
- In asthma: "reversible airflow obstruction" or "airflow limitation" - emphasizing that it improves with bronchodilators 2
- In COPD: "expiratory flow limitation" - often with associated small airway collapse during tidal breathing 3
- On spirometry reports: "obstructive ventilatory defect" - the formal diagnostic terminology 1
The inflammation-induced narrowing prevents normal expiratory flow rates, which is why patients cannot exhale as quickly or completely as they should, resulting in the characteristic shortened or prolonged (but incomplete) exhalation pattern seen in obstructive lung diseases.