What Is COPD? Symptoms, Stages, Medications, & More GoodRx Silent Airway Mucus Plugs in COPD and Clinical Implications CHEST Electronic cigarette use and its association with asthma, chronic obstructive pulmonary disease (COPD) and asthma COPD overlap syndrome among never cigarette smokers Electronic cigarette use and its association with asthma, chronic obstructive pulmonary disease (COPD) and asthma COPD overlap syndrome among never cigarette smokers