What does an elevated Residual Volume (RV) suggest about lung function?

An elevated Residual Volume (RV) suggests the presence of air trapping, which is commonly seen in obstructive lung diseases. In these conditions, such as asthma or chronic obstructive pulmonary disease (COPD), there is increased resistance to airflow during expiration. This leads to a portion of the air remaining in the lungs after the maximum exhalation, causing the RV to increase.

Air trapping occurs because the airways may collapse or narrow during expiration, preventing complete emptying of the lungs. This condition results in a higher volume of air that cannot be exhaled, leading to the elevated RV measurement. Understanding this relationship is crucial for diagnosing and managing obstructive lung diseases, as it helps differentiate them from restrictive lung diseases, which typically present with a decrease in lung volumes, including RV.