Question

Which respiratory volume cannot be measured using a simple spirometer?

• A. Tidal Volume
• B. Inspiratory Reserve Volume
• C. Expiratory Reserve Volume
• D. Residual Volume

Hint:

Remember: A spirometer measures only the air that moves in and out of the lungs.
Residual Volume always remains in the lungs and therefore cannot be measured by spirometry.

Answer 1

The Correct Option is D

Concept:
A spirometer is an instrument used to measure different respiratory volumes and capacities by recording the amount of air inhaled and exhaled by the lungs. However, it can only measure the volumes of air that move in and out of the lungs. Any volume of air that remains inside the lungs and cannot be expelled cannot be directly measured using a simple spirometer.

Step 1: Understanding respiratory volumes
The main respiratory volumes include:
• Tidal Volume (TV): The volume of air inhaled or exhaled during normal breathing.
• Inspiratory Reserve Volume (IRV): The extra amount of air that can be inhaled after a normal inspiration.
• Expiratory Reserve Volume (ERV): The additional air that can be forcefully exhaled after normal expiration.
• Residual Volume (RV): The air that remains in the lungs even after a forceful exhalation.

Step 2: Identifying the volume not measurable by spirometer
Residual Volume remains inside the lungs and prevents lung collapse by maintaining alveolar inflation. Since this air cannot be exhaled, a spirometer cannot measure it directly. Conclusion:
Thus, the respiratory volume that cannot be measured using a simple spirometer is Residual Volume.