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Respiration
Laboratory |
Theory>
Ventilatory Function tests: Dynamic Lung Volumes |
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Lung volumes that depend upon the rate at
which air flows out of the lungs are termed dynamic lung volumes. There
are various dynamic tests: Forced
Vital Capacity test, and the Maximum Voluntary Ventilation
test. |
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The Forced Vital Capacity (FVC)
is the volume of gas that can be exhaled as forcefully and rapidly as
possible after a maximal inspiration. Normally FVC = VC, however in
certain pulmonary diseases (characterized by increased airway
resistance), FVC is reduced. |
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From the FVC test, we can also determine the
Forced Expiratory Volume in 1 sec (FEV1),
which is the maximum volume of air that can be exhaled in a 1 sec time
period. Normally the percentage of the FVC that can be exhaled during 1
sec is around 80% (i.e. FEV1/FVC=80%). |
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Maximum Voluntary Ventilation (MVV)
is the largest volume of air that can be breathed in and out of the
lungs in 1 minute. It will be reduced in pulmonary diseases due to
increases in airway resistance or changes in compliance. |
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Lung diseases, click here |