What happens to expiratory airflow during CF-related exercise testing?

• A. Increased expiratory airflow
• B. Reduced expiratory airflow
• C. No change
• D. Variable

Answer: (B)

In cystic fibrosis, expiratory airflow during exercise testing tends to be reduced because the airways are obstructed by thick mucus, mucus plugging, and inflammation. This obstruction limits how quickly air can be pushed out during expiration, and the higher ventilation demands of exercise reveal these flow limitations. Dynamic changes such as air trapping and increased end-expiratory lung volume can further compress the airways during expiration, making expiratory flow even poorer. So, despite the body's need to exhale rapidly during exercise, the diseased airways prevent an increase in expiratory flow, leading to a net reduction.