What is meant by 'expiratory reserve volume'?

Expiratory reserve volume refers to the amount of air that can be forcefully exhaled after the end of a normal expiration. This means that after you breathe out normally, there is still a significant volume of air left in your lungs that can be exhaled with effort. Thus, it represents the additional air expelled beyond the typical breath out.

This concept is significant in respiratory physiology as it helps in assessing lung function and overall respiratory health. Individuals with certain conditions may have a reduced expiratory reserve volume, indicating potential issues with lung capacity or function.

The other definitions provided do not accurately describe expiratory reserve volume; for example, the maximum volume of gas that can be inspired and the total lung capacity after maximum inspiration refer to different capacities related to inhalation. The amount of gas left after maximum expiration pertains to residual volume, which is the air remaining in the lungs after a complete exhalation.