Obstructive Vs Restrictive Lung Disease

A patient who cannot move air out has a different problem from one whose lungs or chest cannot expand enough to bring air in. That distinction predicts the pulmonary-function pattern, points toward different causes, and changes treatment priorities. Obstruction is primarily a flow problem: narrowed, inflamed, mucus-filled, or collapsible airways slow expiration and trap air. Restriction is primarily a volume problem: stiff lung tissue, pleural disease, an altered chest wall, obesity, or respiratory-muscle weakness limits expansion. A patient can have both mechanisms, so a low FVC or abnormal ratio should be interpreted as a pattern to explain—not a diagnosis by itself.