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Trajectory and distribution of (a) pre-bronchodilator FEV1; (b) pre-bronchodilator FEV1/FVC; and (c) pre-bronchodilator FEF25–75 in patients with acceptable spirometry at both follow-up visits at 3–12 months and 12–24 months (n = 20). FEF25–75, forced expiratory flow between 25% and 75% of vital capacity; FEV1, forced expiratory volume in 1 s; FEV1/FVC, FEV1/forced vital capacity.
