Which of the following lung volumes CANNOT be measured by simple water-seal spirometry?

• A Tidal volume
• B Residual volume ✓
• C Inspiratory reserve volume
• D Expiratory reserve volume

Explanation

Spirometry measures only the volumes that exchange with the atmosphere. Residual volume remains in the lungs after maximal expiration and never leaves the chest, so it cannot be recorded by a spirometer. Functional residual capacity, total lung capacity and RV require helium dilution, nitrogen washout or body plethysmography. Tidal volume, IRV and ERV are all directly traceable on the spirogram, which eliminates the other three options.

Reference: Ganong's Review of Medical Physiology, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.