Air flows into our bodies through the trachea (windpipe), spreading into the lungs via two bronchi (large air tubes), that then branch into smaller bronchioles (smaller air tubes). Bronchioles end at tiny air sacs called alveoli where oxygen is exchanged for carbon dioxide. These tubes and sacs have an elastic quality allowing them to fill with air when we breathe in and expel it when we breathe out.

In COPD, airways become increasingly inflamed (swollen) and blocked, and greatly lose their elasticity making it very difficult to expel air. This most commonly occurs through two types of lung disease:

Emphysema: inflammation of the air sacs causing:

-The loss of elasticity in the air sacs, trapping air in the lungs
-The destruction of the walls between many air sacs, reducing oxygen intake into the blood

Chronic bronchitis: refers to inflammation of airways (bronchial tubes) and increased mucus production that causes:

-The walls of the airways to become thick and inflamed, obstructing the flow of air
-Mucus to block airways stopping the expelling of air