Chronic obstructive pulmonary disease, comes in two forms, emphysema and chronic bronchitis. Smoking is by far the most likely cause of these conditions. Persistent cough is the hallmark of chronic bronchitis. Smoking causes a progressive, inexorable destruction of the lungs in susceptible people, and the only way to halt its progress is to quit smoking. Apart from quitting smoking, people with COPD can get help with other therapies.