What lung function change is observed in a patient with COPD who shows no response to bronchodilator therapy?

In a patient with chronic obstructive pulmonary disease (COPD) who demonstrates no response to bronchodilator therapy, the most appropriate lung function change observed is increased airway resistance. COPD is characterized by chronic inflammation and structural changes in the airways and lung parenchyma, leading to airflow obstruction that is typically progressive.

When bronchodilator therapy is ineffective, it indicates that the airway resistance remains elevated despite treatment. Increased airway resistance in COPD patients is primarily due to factors such as bronchial hyperreactivity, mucus production, and airway narrowing, which are rooted in the disease pathology. These factors contribute to the difficulty in exhaling air, thereby increasing the work of breathing and reducing overall lung function.

In contrast, decreased lung compliance would suggest a stiffer lung, which is not the primary characteristic seen in COPD; rather, compliance often remains normal or may be mildly altered in later stages. Normal airway resistance is not expected in COPD, as the condition inherently involves obstructive changes. Lastly, decreased airway resistance would imply an improvement in airflow, which does not occur in this scenario since the bronchodilator was ineffective. Thus, the presence of increased airway resistance aligns with the fundamental pathophysiological changes in COPD, especially when bronchodilator response is