What is inspiratory reserve volume?

• A. Largest amount of air that can be forcibly exhaled after normal inspiration.
• B. Amount of air that can be forcibly inhaled after normal inspiration, normal is 3.3 L.
• C. Air at the end of normal respiration.
• D. Sum of all 4 lung volumes.

Answer: (B)

How much extra air you can inhale after a normal breath is the concept being tested. Inspiratory reserve volume is that additional amount of air you can forcibly inhale after a normal inspiration, allowing you to fill the lungs beyond the tidal volume up to the total lung capacity. In healthy adults this reserve is typically around 2 to 3 liters, though it varies with body size and fitness (larger individuals may reach about 3.3 L). The description in this item—an amount that can be forcibly inhaled after a normal inspiration—matches this definition exactly. Other options describe different lung volumes: the extra air you can exhale after a normal expiration is expiratory reserve volume; air at the end of normal respiration corresponds to functional residual capacity; and the sum of all four lung volumes equals total lung capacity.