<prompt> Lung volume at the end of quiet expiration:Functional reserve capacityExpiratory reserve volumeResidual volumeTidal volume  <response>: Ans. a Functional reserve capacity. Ref. Guyton 11thpg. pg. 477; Ganong Physiology 22nd ed. 651.The functional residual capacity FRC, which is the volume of air that remains in the lungs at the end of each normal expiration, is important to lung function. Because its value changes markedly in some types of pulmonary disease, it is often desirable to measure this capacity. The spirometer cannot be used in a direct way to measure the functional residual capacity, because the air in the residual volume of the lungs cannot be expired into the spirometer, and this volume constitutes about one half of the functional residual capacity. To measure functional residual capacity, the spirometer must be used in an indirect manner, usually by means of a helium dilution method.LUNG VOLUMES Lung VolumeDefinitionNormal value1.Residual volume RVAir in lung at maximal expiration1..2L2.Expiratory reserve volume ERVAir that can still be breathed out after normal expiration2.2 L3.Tidal volume TVAir that moves into lung with each quiet inspiration500 ml4.Inspiratory reserve volume IRVAir in excess of tidal volume that moves into lung on maximum inspiration3.3 L5.Vital capacity VCIt is everything but the residual volume 5.4 L6.Timed Vital CapacityFEV10.787.Functional reserve capacity FRCRV ERV. Volume in lungs after a normal respiration3.4 L8.Inspiratory capacity 1CIRV TV3.7 L9.Total lung capacityTLC IRV TV ERV RV6.6 L10.Closing lung volume 