Although people with chronic obstructive pulmonary disease (COPD) usually have elements of both chronic
bronchitis and emphysema, one can have chronic
bronchitis, without emphysema or, more commonly, chronic bronchitis with a wide range of emphysema severity from minimal to quite severe. Chronic bronchitis is characterized by airway obstruction to air flow but there is not a good correlation between the degree of obstruction and the amount of emphysema.