FIGURE 4. Obstructive spirometry pattern, the FEV1 and FEV1/FVC are < LLN. The flow–volume loop shows less than expected expiratory flows (dotted line), which create a concave contour. FVC, forced vital capacity; FEV1, forced expiratory volume in the first second; FEV3, forced expiratory volume in the third second; M, median; LLN, lower limit of normal.
