In adults, changes in which volume would reflect problems with expiration?

• A. IRV
• B. TV
• C. ERV
• D. DLCO

Answer: (C)

The correct answer focuses on the expiratory reserve volume (ERV), which is the amount of air that can be forcibly exhaled after a normal expiration. If there are problems with expiration, such as in conditions like chronic obstructive pulmonary disease (COPD) or asthma, the ERV may be significantly decreased. This is due to increased airway resistance, leading to difficulty in expelling air from the lungs effectively.

In a healthy individual, the ERV provides an important measure of lung function, particularly regarding the efficiency of the expiratory phase of breathing. When expiratory issues arise, such as those seen in obstructive lung diseases, the ability to expire additional volume beyond the regular tidal volume diminishes, reflecting underlying pathophysiological changes.

In contrast, other lung volumes mentioned serve different purposes. Inspiratory reserve volume (IRV) relates to the additional air that can be inhaled after a normal inspiration, while tidal volume (TV) represents the normal volume of air displaced during each breath. DLCO refers to the diffusing capacity of the lungs for carbon monoxide, which assesses how well gases pass from the air sacs in the lungs into the blood and is not directly related to the mechanics of expiration. Therefore, changes in ERV are the