What flow-volume loop would you see with a large airway obstruction?

What flow-volume loop would you see with a large airway obstruction?

• A. Wonky loop
• B. Normal loop
• C. Flat loop
• D. Skinny loop

Answer: (C)

Flow-volume loops show how airflow changes with lung volume during a forced breath. A large airway obstruction is typically fixed, meaning the narrowing does not shift with inspiration or expiration, so peak flow is limited in both directions. This causes flattening of both the inspiratory and expiratory limbs, producing a flat, rectangular-looking loop rather than the normal rounded shape.

Flow-volume loops show how airflow changes with lung volume during a forced breath. A large airway obstruction is typically fixed, meaning the narrowing does not shift with inspiration or expiration, so peak flow is limited in both directions. This causes flattening of both the inspiratory and expiratory limbs, producing a flat, rectangular-looking loop rather than the normal rounded shape.