Define the key measures of lung volume

Tidal volume (VT or TV): the volume inhaled and exhaled during normal breathing Inspiratory reserve volume (IRV): the maximum volume above the tidal volume that we can inhale into our lungs. Expiratory reserve volume (ERV): the maximum volume that we can exhale from our lungs at the end of a normal breath. Residual volume (RV): the volume of air remaining in the lungs after a full expiration. We can never empty them completely.