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Percentage change in median FEV1 (a) and FVC (b) from baseline, at follow-up visit 1 (12 ± 1.5 months), visit 2 (24 ± 2.5 months), visit 3 (48 ± 3 months) and visit 4 (60 ± 3 months) separately for COPD EC users and COPD controls.
BL, baseline; COPD, chronic obstructive pulmonary disease; EC, electronic cigarette; FEV1, forced expiratory volume in 1 second; FVC, Forced vital capacity; L, litres; M, months.
