Fig. 2

Graphic explanation of new parameters. Au was defined as the lighted area below the imaginary diagonal line and above the expiratory flow-volume curve. Area of obstruction (Ao) and area of triangle (At) were calculated as follows. Xp denotes the expirated lung volume at PEFR. The ratio of lung volumes at 75 and 25 % of PEFR (0.25/0.75 V) were also measured. Area of rectangle (AR), not shown here, was defined as follows. Ao = Au/At; At = PEFR × (FVC–Xp)/2; AR = (actual PEFR/predicted PEFR) × (actual FVC/predicted FVC) × 100 %