Which volume can be increased in obstructive lung disease?

In obstructive lung disease, there is an increase in residual volume. This occurs because the airflow obstruction makes it difficult for patients to fully exhale air from their lungs. As a result, air becomes trapped in the alveoli, leading to an increase in the amount of air left in the lungs after a maximal exhalation.

Residual volume is the amount of air that remains in the lungs at the end of a forced expiration, and in obstructive conditions such as asthma and chronic obstructive pulmonary disease (COPD), this volume is elevated due to the inability to expel air completely. The increased residual volume reflects the impaired expiratory flow rates characterizing obstructive lung diseases.

In contrast, the other volumes listed do not increase in the same manner. Vital capacity and forced vital capacity are often reduced since they rely on proper airflow to be effectively measured, and expiratory reserve volume is typically diminished due to the trapped air. Therefore, the increase in residual volume distinctly highlights the physiological changes present in obstructive lung disease.