Figure 17-32 The lung volume (ordinate) at which tidal volume is breathed decreases (by 1 L) from the awake state to the anesthetized state. Functional residual capacity (FRC), which is the volume of lung existing at the end of tidal volume, therefore also decreases (by 1 L) from the awake to the anesthetized state. In healthy, obese, bronchitic, and emphysematous patients, the awake FRC considerably exceeds the closing capacity (CC). In obese, bronchitic, and emphysematous patients, the anesthetized state causes FRC to be less than CC. In healthy patients, anesthesia causes FRC to equal CC.