Like HowStuffWorks on Facebook!

What is the sequence of chronic obstructive pulmonary disease?

Chronic obstructive pulmonary disease, or COPD, refers to a group of lung diseases that include chronic bronchitis, emphysema and asthma. COPD is the fourth leading cause of death in the United States and is usually the result of many years of smoking [source: Everyday Health]

COPD is characterized by particular changes in your lungs that progress over time and make it hard for you to breath. Your lungs lose elasticity, so they don't expand as much to fill with air; the tissue walls between your lungs' air sacs (alveoli) get destroyed so that oxygen is less effectively extracted from the air; your airways swell from irritation of their lining; and more mucus is produced, which makes it harder to breathe. Emphysema is caused mainly by destruction of the tissue walls of the lung's air sacs, leaving the lung less elastic, like a floppy balloon. Chronic bronchitis, on the other hand, is characterized mainly by inflamed, plugged-up airways.

The damage that happens to the airways in COPD can't be reversed or undone, although the symptoms can be controlled by medications; lifestyle changes, like quitting smoking and exercising more, may slow the disease's progress. Typically, the first symptoms of COPD are occasional coughing and shortness of breath. Then, you might experience exacerbations, or periods when those symptoms become worse. Over time, you may begin to have symptoms all the time, known as chronic COPD. At this point, you might need medications or extra oxygen to help your lungs function and to prevent constant discomfort and symptoms. Even when you have chronic COPD that is well-controlled, you might have exacerbations when the symptoms of shortness of breath, coughing, wheezing, and increased mucus production become worse. These types of acute or chronic flare-ups can happen if you catch an infection or if you inhale something from the air that irritates your airways.