Meanings of Lung Volumes and Capacities:
Tidal Volume:
During each normal breath, this the volume of air that is inspired and expired.
Expiratory Reserve Volume:
After expiration of normal amount of air (in Tidal volume), this is the amount of air that can still be expired with more effort.
Inspiratory Reserve Volume:
Similar to the expiratory reserve volume, this is the amount of air that can still be inspired with more effort (after taking in a normal breath of air during a tidal volume). Think of it as the extra amount of air that you can still breathe in after a normal breath.
Residual Volume:
When we breath (inspire/expire), this is the volume of air that never actually leaves the lungs (this is because the alveoli still have some air in them even after we breathe out which keeps structural integrity of the lungs).
Dead Space:
There are 2 types of dead spaces: anatomic and physiologic. Both refer to air that is not involved in gas exchange.