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Table 1: Lung volumes and capacities. |
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Lung volumes |
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Tidal volume (TV) |
It is the volume of gas inhaled or exhaled during the normal respiratory cycle |
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Inspiratory reserve volume (IRV) |
It is the maximum volume of gas that can be inhaled from the tidal volume at the end of inspiration. |
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Expiratory reserve volume (ERV) |
This is the maximum volume of gas that can be exhaled from the tidal volume at the end of expiration, i.e. from FRC to RV |
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Residual volume (RV) |
This is the volume of gas that remains in the lung after a maximum exhalation |
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Lung capacities |
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Vital capacity (VC) |
It is the maximum change in volume that can be exhaled or inhaled between the positions of full inspiration (TLC) and full expiration (RV). It corresponds to the sum of the displaceable volumes (VT, IRV and ERV) |
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Inspiratory capacity (IC) |
It is the maximum volume of gas that can be inhaled from the FRC to the TLC. It is the sum of IRV and VT |
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Functional residual capacity (FRC) |
It is the volume of gas present in the lung at the end of passive expiration, of a normal respiratory cycle. It is the sum of ERV and VR |
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Total lung capacity (TLC) |
It is the total volume of the lung at maximum inspiration. It is the sum of all the RV, ERV, VT and IRV volumes, and can also be calculated by the sum of the IC and the FRC or the RV with the VC |