Amount of air that remains within lungs after a forced exhalation is called residual volume. This air participates in gasseous exchange but anatomical dead space volume cannot do so.
Residual volume is an amount of air that allows of gases to continue between pulmonary blood capillaries and alveoli even after a forced exhalation. The volume could never be measured.
Anatomical dead space volume represents an amount of air that does not participate in gaseous exchange because it is retained in the respiratory tract, and can not reach vascularised alveoli. Generally an young adult breathes in 500ml of air, which is called tidal volume . 150ml of tidal volume occupies anatomical dead space.
