This is a randomized,open-label study to research the differences of small airways function between simple chronic obstructive pulmonary disease(COPD) and asthma-COPD overlap(ACO).Assessment of small airways is conducted at baseline,including forced expired volume in one second(FEV1),forced vital capacity(FVC),peak expiratory flow(PEF),maximum expiratory flow rate at 75% of vital capacity(MEF75),maximum expiratory flow rate at 50% of vital capacity(MEF50),maximum expiratory flow rate at 25% of vital capacity(MEF25),impulse oscillometry,diffusion function,residual volume(RV) and total lung capacity(TLC).Budesonide(160ug) and formoterol(4.5ug) bid will be given to both groups(chronic obstructive pulmonary disease and asthma-COPD overlap) for 3 months.Quality of life is assessed through questionnaires including modified Medical Research Council dyspnoea scale(mMRC),St George's Respiratory Questionnaire(SGRQ) and chronic obstructive pulmonary disease assessment test(CAT).All of the patients will have a follow-up visit after 3 months' treatment.
