What is a key feature of chronic obstructive pulmonary disease (COPD)?

Chronic obstructive pulmonary disease (COPD) is primarily characterized by persistent airflow limitation, which is a hallmark feature of the disease. This limitation is often due to a combination of chronic bronchitis and emphysema, both of which lead to progressive and largely irreversible changes in the airway structure and function. Unlike asthma, which is marked by reversible airway obstruction, COPD exhibits a progressive decline in lung function over time that does not significantly improve with bronchodilators or other medications.

Patients with COPD experience a gradual worsening of respiratory symptoms such as chronic cough, sputum production, and shortness of breath, especially during physical activities. However, these symptoms persist even at rest during the disease's later stages, differentiating COPD from transient airway conditions. In contrast to the other options, which may have varying relevance to COPD, it is the ongoing, persistent limitation in airflow that defines the disease and its impact on the patient's quality of life.