Figure 26-1 Forced vital capacity (FVC) maneuver in a subject with a normal lung. Exhaled volume is plotted against time as the subject expires forcefully, rapidly, and completely to residual volume (RV) after a maximum deep inspiration to total lung capacity (TLC). FEV₁ , forced expired volume in 1 second; FEF_200–1200 , forced expiratory flow between 200 and 1200 mL of expired volume; FEF_25%–75% , forced expiratory flow over the midportion of vital capacity (i.e., from 25% to 75% of expired volume).