Differences of Small Airways Function Between Chronic Obstructive Pulmonary Disease(COPD) and Asthma-copd Overlap(ACO)

Inclusion Criteria: * Male or female patients 18 to 80 years-old. * A diagnosis of chronic obstructive pulmonary disease according to the Global Initiative for Chronic Obstructive Disease(GOLD 2018) guidelines are recruited to the chronic obstructive pulmonary disease group.A diagnosis of asthma-chronic obstructive pulmonary disease overlap according to Global Initiative for Chronic Obstructive Disease(GOLD 2018),Global Initiative for Asthma(GINA 2018) and Spanish COPD Guidelines(GesEPOC 2017) are recruited to the asthma-chronic obstructive pulmonary disease overlap group. * Willing and able to provide written informed consent. * Willing and able to attend all study visits and adhere to all study assessments and procedures. Exclusion Criteria: * Severe comorbidities including unstable cardiac or pulmonary disease or any other medical conditions including unstable ischemic heart disease,unstable cardiac arrhythmia or heart failure,life threatening arrhythmias,etc. * Recent history of chronic obstructive pulmonary disease exacerbation requiring hospitalization or need for increased treatments for chronic obstructive pulmonary disease within 6 weeks.