Pulmonary Physiology, Gas Pressures & Volumes, Dr. D. Penney




Figure 1.01. Standard (static) lung volumes as measured with a spirometer.


Tidal Volume (TV) is the volume of air moved in and out of the respiratory tract (breathed) during each ventilatory cycle.

Inspiratory Reserve Volume (IRV) is the additional volume of air that can be forcibly inhaled following a normal inspiration. It can be accessed simply by inspiring maximally, to the Maximal Inspiratory Level.

Expiratory Reserve Volume (ERV) is the additional volume of air that can be forcibly exhaled following a normal expiration. It can be accessed simply by expiring maximally to the Maximal Expiratory Level.

Vital Capacity (VC) is the maximal volume of air that can be forcibly exhaled after a Maximal Inspiration. VC = TV + IRV + ERV.

Residual Volume (RV) is that volume of air remaining in the lungs after a Maximal Expiration. It cannot be expired no matter how vigorous or long the effort. RV = FRC - ERV.

Functional Residual Capacity (FRC) is the volume of air remaining in the lungs at the end of a normal expiration. FRC = RV + ERV.

Total Lung Capacity (TLC) is the volume of air in the lungs at the end of a Maximal Inspiration. TLC = FRC + TV + IRV = VC + RV

Minute Volume is the volume of air exhaled per minute.

Maximal Breathing Capacity (also called "Maximal Voluntary Ventilation") is the maximum volume of air that can be exhaled by voluntary effort in a 15 second interval. This volume is multiplied by 4 and expressed as liters per minute.

For an Alternate List of Lung Volumes



Another graphical representation of Lung Volumes.



Last Changed 05/01/00


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