Question

Residual volume is
A. Lesser than tidal volume
B. Greater than Inspiratory volume
C. Greater than vital capacity
D. Greater than tidal volume

Answer 1

The amount of air left in the lungs after complete exhalation is known as the residual volume. This air cannot be exhaled and thus maintains the opening of alveoli (small air sacs present in the lungs) at all times. This volume helps in determining the functioning of the lungs.

Complete answer:
A deep, forceful expiration does not result in collapsing of the lungs as some amount of air always remains present in the lungs. This air maintains the expansion of airways as well as the alveoli. This volume of air is known as the Residual Volume (RV) which refers to the volume of air that remains present inside the lungs even after a forceful exhalation. There is no alteration in the residual volume based on the volume of lungs at which exhalation was initiated. Moreover, it is not possible to breathe out all the air from lungs completely therefore determination of residual volume is further challenging. Residual volume is 1.2 liters in men and 1.1 liters in women.
On the other hand, tidal breathing is also referred to as the resting breathing or the normal breathing. It is the amount of air taken in or breathed out in one single breath. It is 0.5 liters in both men and women while Inspiratory reserve volume is the maximum volume of air that can be breathed in during forceful inhalation. It is 3.3 liters in men and 1.9 liters in women. However, vital capacity is the amount of air that is exhaled after the forceful inhalation. It is 4.8 liters in men and 3.1 liters in women.

Hence, the correct answer is option (D).

Note: Some indirect methods employed for measuring the residual volume are body plethysmography, radiographic planimetry, nitrogen washout and closed circuit dilution (which include the helium dilution technique).