Why does residual volume increase as capacity decreases?

RV is the residual volume

TC is the total capacity

EA is the volume of exhaled air

Hence, when capacity decreases residual volume increase

Explanation:

Maximum air inhaled or exhaled per stroke of breathing is defined as the maximum capacity of a lung. Residual volume is the air remaining in the lungs after the expiration

When the capacity of lungs reduces, the volume of air exhaled by the lungs reduces. Hence, the volume of residual air increases.  

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