lung volumes

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lung volumes

Physiology A group of air 'compartments' into which the lung may be functionally divided
Lung volumes  
Expiratory reserve capacity–ERV The maximum volume of air that can be voluntarily exhaled
Functional residual capacity (FRV) Volume left in the lungs at the end of a normal breath which is not normally part of the subdivisions
Inspiratory capacity–IC The maximum volume that can be inhaled
Inspiratory Reserve capacity–IRC The maximum volume that can be inhaled above the tidal volume
Tidal volume–VT The normal to-and-fro respiratory exchange of 500 cc; vital capacity is the maximum amount of exhalable air; after a full inspiration, which added to the residual volume, is the total lung capacity
Total lung capacity–TLC The entire volume of the lung, circa 5 liters
Vital capacity–VC The maximum volume that can be inhaled and exhaled  
Lung volumes.

lung volumes

measurements made as part of pulmonary function tests; the volumes that move in and out during the normal breathing cycle, and with deliberate additional effort, can be measured directly by spirometry with the subject breathing through a closed circuit in and out of a cylinder inverted over water, or into a vitalograph, or by pneumotachograph; the residual volume can be measured only indirectly by dilution methods (usually with helium) or by whole body plethysmography. See also ventilation. See figure and table overleaf .
Table 1: Lung volumes
VT (TV)Tidal volumeVolume of inspired/expired air moving in and out with each breath
IRV
ERV
Inspiratory and expiratory reserve volumesUsed when tidal volume increases above that at rest
VCVital capacityVolume that can be inspired/expired after full expiration/inspiration
FEV1Forced expiratory volume in 1sVolume exhaled in the first second, with maximal effort after full inspiration
FRCFunctional residual capacityVolume remaining in the lungs at end-expiration; decreases as tidal volume increases
RVResidual volumeRemains after a maximal expiratory effort; cannot be exhaled
TLCTotal lung capacityVital capacity + residual volume
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