Obstructive lung disease
Also known as: obstructive pulmonary disease
Obstructive lung disease is a group of respiratory conditions — including asthma, chronic bronchitis, emphysema, and bronchiectasis — in which airflow out of the lungs is limited. The hallmark is a reduced FEV1/FVC ratio on pulmonary function testing, reflecting difficulty exhaling.
Obstructive lung disease describes any condition in which air can get into the lungs but has trouble getting out. Narrowed or collapsing airways slow expiratory airflow, so patients exhale slowly and incompletely, trapping air in the lungs. The major obstructive diseases are asthma, chronic bronchitis, emphysema (the latter two grouped as COPD), and bronchiectasis.
Pulmonary function tests define the pattern. The forced expiratory volume in one second (FEV1) falls proportionally more than the forced vital capacity (FVC), so the FEV1/FVC ratio is reduced — the single most tested criterion. Air trapping increases residual volume and total lung capacity, distinguishing obstruction from restrictive lung disease, where volumes shrink but the FEV1/FVC ratio is normal or elevated. Each obstructive disease adds its own signature: reversibility with bronchodilators in asthma, chronic productive cough in chronic bronchitis, and destruction of alveolar walls with decreased diffusion capacity in emphysema.
Clinically, patients present with wheezing, dyspnea, and prolonged expiration. Chronic obstruction strains gas exchange and can progress to hypoxemia, hypercapnia, and right heart strain. Management combines bronchodilators, inhaled corticosteroids, smoking cessation, and, in rehabilitation settings, breathing strategies such as pursed-lip breathing that keep airways open during exhalation.
The USMLE Step 1 tests obstructive lung disease in respiratory pathology — expect PFT interpretation and disease-specific findings. The NPTE for physical therapists and physical therapist assistants tests it in the pulmonary system content, emphasizing auscultation findings, differential diagnosis, and interventions for patients with obstructive disease.
Key takeaways
- Obstructive lung disease limits expiratory airflow; asthma, chronic bronchitis, emphysema, and bronchiectasis are the main types.
- A decreased FEV1/FVC ratio is the defining pulmonary function finding.
- Air trapping raises residual volume and total lung capacity, unlike restrictive disease, where lung volumes are reduced.
- Typical features include wheezing, prolonged expiration, and dyspnea; asthma is distinguished by bronchodilator reversibility.
- The USMLE Step 1 and NPTE test PFT patterns, disease features, and appropriate interventions.