USMLE Step 1 Question 322

Question:

A 59-year-old man with a 40-year history of smoking at least one pack per day presents complaining of progressive shortness of breath over the last few years. On exam, he is found to have lung hyperinflation, prolonged expiration, and hyperresonance to percussion. Which of the following findings is most likely?

Correct Answer: D.  Loss of small airway patency during expiration

This man likely has emphysema secondary to cigarette smoking. In emphysema, there is destruction of the airspaces distal to the respiratory bronchioles, as well as a loss of elasticity of these airways. As a result of the loss of elasticity, small airways in emphysematous lung regions will collapse due to the increased intrathoracic pressure of expiration. This results in air being trapped distal to collapsed airways. Throughout expiration, these air spaces exert pressure on the chest wall, increasing the anteriorposterior diameter of the chest over time.
Due to air trapping, the tendency of the lungs to collapse is decreased. The exception to this is if a bulla were to rupture, spontaneous pneumothorax could occur, secondarily resulting in atelectasis.
Due to the loss of elasticity and increased lung volume, lung compliance actually increases in emphysema.
Due to air trapping, residual volume is increased.
Small airway patency is maintained during inspiration because there is a negative intrathoracic pressure.