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Incoming links: Tidal volume
Vital capacity 2026-11-05
Vital capacity, VC, is the volume change between maximal inspiration and maximal expiration. It is the exchangeable difference between total lung capacity and residual lung volume:The sum uses inspiratory reserve volume, tidal volume and expiratory reserve volume.[ref]
Standardisation of the measurement of lung volumes, 2023 update by Nirav R. Bhakta and others. Definitions and subdivisions of lung volume; Figure 1
A constructed volume record with maximum 6.0 L and minimum 1.4 L gives VC 4.6 L. Subdivisions 3.0 L, 0.5 L and 1.1 L give the same result. Those increments partition the full excursion; none includes the 1.4 L that remains after maximal expiration.
Forced vital capacity names a specific forceful expiratory maneuver. The broader vital capacity can also be measured during a relaxed expiration or inspiration. The maneuver and completeness of its endpoints matter when comparing measurements.[ref]
Standardisation of the measurement of lung volumes, 2023 update by Nirav R. Bhakta and others. Definitions and subdivisions of lung volume, inspiratory VC, expiratory VC and FVC
[ref]Standardization of Spirometry 2019 Update by Brian L. Graham and others. FVC Maneuver; end-of-forced-expiration considerations
A spirometry trace records volume change, so the same VC can arise at different absolute lung-gas levels. A second stipulated record spanning 7.0 to 2.4 L also gives 4.6 L. Adding a common offset to every point leaves VC unchanged. This is why a precise vital capacity measurement alone cannot determine residual lung volume or total lung capacity.