Chronic bronchitis and emphysema are the two primary diseases found within this "class" of disease called COPD. Asthma, although sharing many similarities and symptoms with COPD, is not included in this class because it can be reversed. In other words, a person with asthma, may not have permanent lung damage, like is seen with COPD.
Also, asthma is also not a progressive disease. In fact, children diagnosed with asthma may grow into adulthood and experience very minimal asthma-related symptoms. Despite these marked differences, many of the treatments are the same since many of the symptoms manifested are the same - like narrowing of the airway, coughing, production of mucous, etc.