http://www.nhlbi.nih.gov/health/dci/Diseases/Copd/Copd_WhatIs.html
National Heart, Lung, and Blood Institute, National Institutes of Health
This publication discusses chronic obstructive pulmonary disease (COPD), a lung disease in which the lungs are damaged, making it hard to breathe. In COPD, the airways—the tubes that carry air in and out of your lungs—are partly obstructed, making it difficult to get air in and out.