- Chronic obstructive pulmonary disease (COPD) is a common cause of persistent dyspnoea due to its characteristic progressive airflow limitation that is not fully reversible.
- It results from chronic bronchitis and emphysema leading to airway inflammation, obstruction, and alveolar destruction.
- These pathological changes cause impaired gas exchange and increased work of breathing, which manifest as chronic and progressively worsening breathlessness.
- Unlike asthma, which often has episodic symptoms, COPD typically produces a continuous dyspnoea that worsens over time.
- Pulmonary embolism usually causes acute dyspnoea, and interstitial lung disease, while causing dyspnoea, is less common than COPD.

Reference: Davidson’s Principles and Practice of Medicine, 24th Edition, Chapter: Disorders of the respiratory system, Page 567.