Question: 144 Vital capacity of lung is \_\_\_\_ .
(1) \mathrm{IRV}+\mathrm{ERV}+\mathrm{TV}-\mathrm{RV}
(2) \mathrm{IRV}+\mathrm{ERV}+\mathrm{TV}
(3) \mathrm{IRV}+\mathrm{ERV}
(4) \mathrm{IRV}+\mathrm{ERV}+\mathrm{TV}+\mathrm{RV}
Answer: Option (2)
Explanation:
Vital capacity is defined as the maximum volume of air that can be expelled from the lungs after a maximum inhalation.
It includes the volume of air inhaled forcibly after normal inspiration, the volume of air exhaled forcibly
after normal expiration, and the volume of air inhaled or exhaled during normal breathing.
Thus, vital capacity is the sum of inspiratory reserve volume, expiratory reserve volume, and tidal volume.
Mathematically, vital capacity is given by
\mathrm{VC}=\mathrm{IRV}+\mathrm{ERV}+\mathrm{TV}.
Residual volume is not included because it cannot be expelled from the lungs.
Therefore, the correct option is (2).